27 Jul
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Application of augmented reality for inferior alveolar nerve block anesthesia: A technical note

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Efforts to apply augmented reality (AR) technology in the medical field include the introduction of AR techniques into dental practice. The present report introduces a simple method of applying AR during an inferior alveolar nerve block, a procedure commonly performed in dental clinics.

Keywords: Augmented Reality; Dentistry; Inferior Alveolar Nerve; Nerve Block.


INTRODUCTION

Augmented reality (AR) technology applies virtual information, such as three-dimensional (3D) images, to the real environment in an attempt to acquire more information than can be obtained from real situations. Efforts have been made to apply augmented reality (AR) technology in the medical field [1]. AR techniques have been introduced to the fields of oral and maxillofacial surgery and dentistry, but are not yet widely used [2,3]. In fact, the application of AR techniques in dental procedures is considered impractical due to the technical difficulties with its use.

The development of cone beam computed tomography (CBCT) has led to an increased use of CT in the oral and maxillofacial fields [4]. Software that reconstructs CT images into 3D images has also become widely used. Even without expensive 3D simulation software, information regarding 3D reconstruction of the jaw can easily be obtained using free or open source 3D simulation software.

Inferior alveolar nerve block anesthesia is a necessary and fundamental local dental anesthetic procedure. Although anesthetic failures can occur with inferior alveolar nerve block anesthesia for reasons such as poor anesthetic technique and anatomical variation, 3D anatomical positioning of the mandibular foramen is important for the procedure. The three-dimensional position of the mandibular foramen relative to the anatomical structures of the oral mucosa is helpful for the block procedure because it can be used as a reference for anesthetic injection. The present report introduces a simple method for applying AR during an inferior alveolar nerve block procedure, which is commonly performed in dental clinics.

TECHNICAL NOTE

Here we describe the generation of an AR using CT images of a patient’s mandible to create a 3D image of the mandible, combined with real images of the oral cavity. We extracted digital imaging and communications in medicine (DICOM) files from the available mandibular CT data, including information obtained during the examination of a maxillofacial deformity or before the extraction of a mandibular third molar. The DICOM files were imported into 3D reconstruction software (i.e. Simplant [Materialise Dental, Leuven, Belgium], Mimics [Materialise, Leuven, Belgium], InVivoDental [Anatomage, San Jose, CA, USA], OnDemand3D [CyberMed Inc., Seoul, Korea], OsiriX Imaging Software [Pixmeo, Geneva, Switzerland], 3DSlicer open source software [http://www.slicer.org]) to produce 3D images of the mandible. The software must enable the reconstructed 3D mandibular images to be positioned, rotated, enlarged, and reduced. 3D movement of the mandibular image are possible with all the previously mentioned software. Using any of these software programs, DICOM data for the CT were converted to stereolithography (STL) file formats. The following is an example of a DICOM to STL conversion. The DICOM files were opened in Mimics software (Materialise, Leuven, Belgium). DICOM CT data were converted to STL files with the following settings: threshold values to construct 3D images of the CT data were set to 226–3071 Hounsfield unit (these were the threshold values previously set for bones in the Mimics program). The 3D structure quality was set to the optimal 3D calculation in the Mimics program. The areas of the temporomandibular joint and teeth were separated from the craniomaxillary area for only the mandibular segmentation in the case of the facial CT. If using the STL data of the mandible, computer-aided design-related software also are able to reconstruct 3D mandibular images for positioning, rotation, enlargement, and reduction. In the current method, Rapidform Explorer, which is free software (INUS Technology, Seoul, Korea) was used to manipulate the mandible using 3D movement for AR. Another software program (i.e. transparency_utility, Actual Transparent Window [Actual Tools, Vancouver, Canada]) that can adjust window transparency must also be installed on the same computer. To reduce the time required for the actual procedure, the steps for the preparation of the 3D mandible reconstruction should be completed prior to preparing the patient for surgery (Fig. 1).

For patients requiring an inferior alveolar nerve block for extraction of the third molar or other dental treatment, a digital camera was used to take intraoral photographs to obtain the images of the actual oral cavity immediately before administering inferior alveolar nerve block anesthesia. In such cases, the patient was instructed to open his or her mouth in the same manner as during an inferior alveolar nerve block. The intraoral photographs were taken from an angle similar to the one the clinician

would use to look down at the patient’s oral cavity during the injection of a local anesthetic (Fig. 2). These photographs were uploaded to a computer to be overlapped with the 3D mandibular images (Fig. 3). Next, the 3D mandibular images displayed on the software were arbitrarily overlapped with the intraoral photographs on the computer screen (Fig. 4). Another software program was used to adjust the window transparency of the software displaying the 3D images of the mandible, until the intraoral photographs were visible in the background (Fig. 5). Finally, the 3D mandibular images were enlarged, reduced, rotated, and positioned as needed so that the positions of the teeth in the 3D images matched those in the intraoral photographs (Fig. 6).

Using this simple AR method, the superimposed images were referenced in order to locate the mandibular foramen on the intraoral view during local anesthetic injection, while performing an established procedure for inferior alveolar nerve block (Fig. 7).

DISCUSSION

In this report, we introduced a simple method for applying AR techniques to dental practice. The described AR techniques combine real images of the oral cavity with 3D mandible images generated from the CT images of a patient’s mandible. Such methods are employed in dental clinics for detection of dentofacial deformities and observation of the inferior alveolar nerve canal of the jaw [2,5].

Since free/open source software are easy to access, expensive 3D simulation software is unnecessary for the current AR method. The 3D reconstruction software allows the user to simply enlarge, reduce, and rotate 3D jaw images using only a keyboard and a mouse. Software enabling window transparency adjustment is also highly accessible and easy to use.

In the method described here, tooth areas within the CT images of the jaw were replaced using optical scanning data for these teeth and subsequently, these data were merged and reconstructed into 3D images. Next, the generated 3D mandibular images were superimposed onto real oral photographs by aligning the position of each tooth to create an augmented reality. It may not always be necessary to obtain CT images with the tooth images replaced using optical scan data, particularly when the augmentation between 3D mandibular images and oral photography is performed for the purpose of using simple AR to gain supplementary information for an inferior alveolar nerve block. However, this procedure may be required to generate sufficiently accurate 3D images of the teeth of patients with an orthodontic bracket or multiple prosthodontics. In such cases, the tooth area from the CT images should be interpreted using a digital dental cast or optical scanning of the teeth [6].

The inferior alveolar nerve block is a commonly performed procedure in the field of dentistry. It requires accurate identification of the anatomical location of the mandibular foramen, which varies among patients [7]. We are now capable of obtaining greater information about the mandibular foramen through 3D reconstruction of available CT images [8]. However, the 3D information provided by this method is limited if the technique is not accompanied by direct observation of the oral cavity. We attempted to overcome this limitation with the method described here. There is currently no defined protocol for the use of AR techniques or for the superimposition of clinical and 3D images [1,9]. In general, AR techniques involve the use of devices to monitor patient movement and reflecting these movements in an AR [10]. However, it is not yet clear how tracking devices should be used for patient movement or where on the body they must be attached [1,3]. There also remains a need to assess the accuracy of the positional information provided by these devices. Overall, the advantages of AR techniques are accompanied by multiple limitations, including the difficulty of their technical application and their limited accuracy. However, we believe that AR techniques should be used wherever they can provide useful information and can be easily used in a clinical settings. For this reason, we have introduced the simple AR techniques described herein. Future studies are needed to investigate the accuracy of the superimposition method.

In our technique described here, we attempted to create an AR on a monitor. Clinicians can view clinical images on a monitor, through transparent glass, or on a headmounted display [5], with the monitor being the simplest technique. In this study, the inferior alveolar nerve block was performed quickly and with the aim of obtaining supplementary information regarding the shape and location of the mandibular foramen. In this situation and with the patient remaining stationary, it was appropriate to view the clinical images using a monitor.

Three-dimensional anatomical positioning of the mandibular foramen is important to the procedure for an inferior alveolar nerve block anesthesia. The position of the mandibular foramen should be found threedimensionally relative to the oral anatomical structures. Using the AR technique, the anatomical structures in the oral cavity that are selected as anatomical references should be easy and convenient to use regardless of the skill of the operator and the error in the positioning of the mandibular foramen should be small. Using the augmented bone structures in the oral cavity as references to optimize the position of the mandibular foramen may increase the efficiency of the procedure for an inferior alveolar nerve block. Thanks to the recent commercialization of computed tomography (CT) and the development of computer software including commercial and open software, studies of the anatomical structures of the human body have progressed. Our technique required a few more minutes to perform when compared to the conventional method for obtaining an augmented image prior to performing an inferior alveolar nerve block. Although additional time was required for AR, the current AR technique provided related informations for bony structures in the oral cavity that can be referred to during anesthetic injections in order to easily and accurately locate the position of the mandibular foramen for an inferior alveolar nerve block. These attempts at applying AR techniques to dental treatment may lead to the development of clinically applicable AR techniques. They can also be widely used for education dentistry and in the oral and maxillofacial fields.

Our technique only required a few minutes to obtain 3D CT images of the mandible, extract DICOM data, and import the data to the software prior to performing an inferior alveolar nerve block. In the clinical setting, it takes only a few seconds to transfer intraoral images from a digital camera or other device to the computer. Similarly, it required only a few seconds to adjust the window transparency of the 3D simulation software on the monitor and a minute to position, rotate, and adjust the magnification scale of the 3D images of the mandible to match the tooth area between an oral photograph and 3D mandibular image. Simple processes for applying AR techniques, as described here, may enable the routine clinical application of AR in dental practice.

Simple AR techniques, such as those described in this report, may be performed as a supplementary step in the detection of impacted teeth and jaw cysts that are difficult to observe in clinical practice. These simple attempts at applying AR techniques to medical treatment may lead to the development of clinically applicable AR techniques that can be used widely in the medical field, including dentistry and the oral and maxillofacial fields.

CONFLICTS OF INTEREST: The authors have no conflicts of interest to declare.

References

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19 Jul
info

Augmented Reality and Virtual Reality in Dentistry: Highlights from the Current Research

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Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Abstract

Many modern advancements have taken place in dentistry that have exponentially impacted the progress and practice of dentistry. Augmented reality (AR) and virtual reality (VR) are becoming the trend in the practice of modern dentistry because of their impact on changing the patient’s experience. The use of AR and VR has been beneficial in different fields of science, but their use in dentistry is yet to be thoroughly explored, and conventional ways of dentistry are still practiced at large. Over the past few years, dental treatment has been significantly reshaped by technological advancements. In dentistry, the use of AR and VR systems has not become widespread, but their different uses should be explored. Therefore, the aim of this review was to provide an update on the contemporary knowledge, to report on the ongoing progress of AR and VR in various fields of dental medicine and education, and to identify the further research required to achieve their translation into clinical practice. A literature search was performed in PubMed, Scopus, Web of Science, and Google Scholar for articles in peer-reviewed English-language journals published in the last 10 years up to 31 March 2021, with the help of specific keywords related to AR and VR in various dental fields. Of the total of 101 articles found in the literature search, 68 abstracts were considered suitable and further evaluated, and consequently, 33 full-texts were identified. Finally, a total of 13 full-texts were excluded from further analysis, resulting in 20 articles for final inclusion. The overall number of studies included in this review was low; thus, at this point in time, scientifically-proven recommendations could not be stated. AR and VR have been found to be beneficial tools for clinical practice and for enhancing the learning experiences of students during their pre-clinical education and training sessions. Clinicians can use VR technology to show their patients the expected outcomes before the undergo dental procedures. Additionally, AR and VR can be implemented to overcome dental phobia, which is commonly experienced by pediatric patients. Future studies should focus on forming technological standards with high-quality data and developing scientifically-proven AR/VR gadgets for dental practice.

Keywords: augmented reality; virtual reality; dentistry; education; health


INTRODUCTION

The field of dentistry has recently experienced many technological advancements that have changed the dimensions of many subspecialties of dentistry. To further improve and enhance dental education and the clinical application of dentistry, new innovations have been introduced. These include augmented reality (AR) and virtual reality (VR), which have been introduced and studied with the goal of improving dentistry. The word “virtual” in the field of computing and technology refers to something that appears to exist without being physically present in the real world. In dentistry, software is used to simulate dentofacial structures in real-time. The functionality of these anatomical structures is also simulated for a sophisticated yet complete virtual experience.

The commonly-used traditional digital technologies operate by using a digital scanner to obtain a digital image, then the operator uses the digital image to modify the different dental aspects of the patients, and then finally, the modifications are transferred to the digital wax-up. Virtual reality, however, takes laser scans of the patient’s teeth and other oral and extraoral structures as required and feeds them into a computer that forms a 3D model of the same, which is then loaded into a simulator. Dental surgeons/dental students using this simulator can practice and do evaluations before the procedure is performed on a real patient in various specialties of dentistry, i.e., oral and maxillofacial surgery, orthodontics, implantology, restorative dentistry, dental public health, and dental education [1,2]. Automated data recording is integrated into this system, making postoperative analysis and self-assessment possible for the users.

Augmented reality mainly aims to improve the clinical practice in the field of dentistry as the clinical information that is generated can be directly visualized on the patient, combining the real world with the digital world. The primary use of augmented reality in dentistry comprises the use of digital information to improve reality, which allows effective communication between the patients and dentists through the use of videos, pictures, and three-dimensional models.

AR is also an interactive technology but is distinct from virtual reality in the way that the user interacts with an integral image of the patient’s teeth/anatomical structures and works on them in a 3D environment registered using fundamental imaging techniques, and thus AR augments the physical elements with virtual elements [1]. Integral imaging stands somewhere between stereoscopy and holography, both of which have their limitations. The devices required for integral imaging are simply a liquid-crystal display (LCD) and a lens in front of the LCD. The resulting 3D image is easily viewed by the user without the need for special eyewear [3]. When digital images are placed upon real images and alterations are done virtually, the results that are intended to be clinically achieved can be experienced pre-operatively [4]. This familiarizes the patient with the steps of treatment and its outcome. In the case of a smile makeover or complete mouth rehabilitation, before any dental procedure is performed, AR enables patients to get a glimpse of what they will look like once the treatment is undertaken by the dentist/dental surgeon. This helps reduce the number of visits and is time and money-saving for both the patient and the dentist, along with many other advantages associated with the use of AR/VR.

On the other hand, virtual reality makes use of technologically advanced and customized software to visualize a digital three-dimensional reality where the user’s senses are stimulated using computer-generated feedback and sensations. Therefore, virtual reality allows the user to participate in virtual realities related to the physical reality, thus making virtual reality indistinguishable from physical reality. AR and VR differ from each other in several ways such as AR users can control their presence in the real world, but VR is system controlled. Secondly, the use of VR requires a headset device, but AR can be used with a smartphone. Moreover, VR can only enhance fictional reality, but AR can improve real and virtual worlds.

Virtual simulators have an edge over physical simulators as they allow the operator to go back in time and make amendments to the procedure that has been done. These virtual practice sessions improve the efficiency of the operating personnel and make the Appl. Sci. 2022, 12, 3719 3 of 13 outcome predictable [5]. According to the degree of immersion experienced by the user, virtual reality has three broad classifications: immersive virtual reality, which consists of a head-mounted display system, non-immersive virtual reality, which is based on a computer-aided (CAD) network, and semi-immersive virtual reality, based on a cave automatic virtual environment [1,6]. In immersive virtual reality, the operator is immersed in a virtual environment where they can interact with recorded 3D images/objects using a wearable device/headset and a pen-shaped manipulator. Eye movements and leap motion of the hands are detectable through this device [4]. However, in non-immersive virtual reality, the operator interacts with 3D simulations on a desktop computer displayed on a flat-screen 2D monitor using a mouse instead of a wearable device and manipulates the virtual images without being a part of a virtual scenario [4].

In regard to the sub-specialties of dentistry, so far, augmented reality and virtual reality have been mostly applied in the fields of dental implantology and orthognathic surgery. In augmented reality scenarios, the visual information gathered by registering anatomical structures and overlaying them on actual operative sites provides better guidance for surgical and other dental procedures. In some AR systems, 2D-projected computer graphics (CG) do not provide the viewer with the perception of depth at the surgical site, thus reducing the safety and accuracy of the procedure. Hence 3D images generated either via stereoscopy [3], integral imaging (or integral photography) and holographic display [7] are projected onto the site of the procedure, which enables the user to spatially visualize and perceive the depth of tissues from all locations, which enhances safety and accuracy. Furthermore, the contemporary Microsoft Hololens waveguide AR system, significantly advances the optical design of current AR display systems and may also be applied to a broad range of optical systems, including high-precision imaging, sensing, and advanced photonic devices [6].

The purpose of this review was to provide an update on the contemporary knowledge, to report on the ongoing progress of AR and VR in various fields of dental medicine and education, and to identify further research needs that will achieve their clinical translation.

2. Materials and Methods

For this review, an electronic search was performed via PubMed, Scopus, Web of Science, and Google Scholar using the terms “Augmented Reality”, “Virtual Reality”, “AR and VR”, “AR and Dentistry”, “VR and Dentistry”, “Use of AR and VR in Dentistry”, “AR/VR and dental education”, for published research articles from the year 2011 to 2021. A secondary search was further performed after analyzing the list of articles that met the pre-determined inclusion criteria of the study. Three independent researchers S.F., A.M. and N.A., read the articles that were retrieved by the search engines, and studies that did not meet the inclusion criteria were excluded. Due to the heterogeneity of the design of the included studies, a systematic review and meta-analyses could not be performed. Therefore, a narrative review with the “best-evidence synthesis” [8] approach was carried out. The pre-determined inclusion criteria for this study were as follows:

  • Clinical trials
  • Case-control studies
  • Observational studies
  • Studies where AR and VR have focused on dentistry
  • Studies in the English Language

The studies that were excluded from this study were:

  • Review articles
  • Short communications
  • Letters to Editors
  • Studies in languages other than English

The data that were collected from the studies were extracted by the investigators and then noted under the following headings: “authors”, “year of publication”, “study type”, “sample size”, “outcomes”, and “field of dentistry”. Any disagreement amongst the investigators was solved by discussion with a third reviewer, A.L.

3. Outcomes of Literature Search

The initial search of the databases resulted in a total of 101 articles. After analysis of the abstracts, title, and duplications of the studies, 81 articles were removed based on the inclusion criteria specified for this review. A total of 20 articles that fulfilled the inclusion and exclusion criteria were included in this review article.

The general characteristics of the studies included in this study have been described in Table 1. AR and VR have been successfully used in various fields of dentistry such as oral and maxillofacial surgery, orthodontics, endodontics, dental implantology, and dental public health. Dental anxiety is a problematic experience for both patients and dentists, especially pediatric patients. Such anxieties have been successfully reduced by the use of AR and VR whereby children were subjected to watching cartoons using virtual reality goggles, resulting in a decrease in heart rates and pain scores [9,10]. The use of AR and VR has further improved the surgical accuracy and duration of surgery along with the manual dexterity of surgeons who employ the use of AR and VR [11–14]. The development of AR devices has allowed users to combine all sorts of information and images that are converted into reality. Furthermore, orbital reconstruction and placement of the dental implants in the alveolar bones of patients require rigorous planning and surgical skills for optimal outcomes, which are further enhanced by the use of AR and VR [12,15].

The use of AR and VR has been introduced into operative dentistry residency training, which helps the residents to improve their confidence and knowledge by practicing the skills virtually before the implementation of their skills on patients [16]. Trauma is a common finding in dentistry, ranging from trauma affecting a single tooth to large facial fractures. Traumas and tumors are known to involve the orbits, so the introduction of the use of AR and VR in the reconstruction of the orbit has been used successfully [17]. Moreover, in the field of oral and maxillofacial surgery, the use of AR and VR in performing mandibular angle oblique split osteotomy has been studied, and improved and effective results were obtained [18]. The use of AR technology in oblique split osteotomy proved to be helpful for controlling maxillary translocation during orthognathic surgery.

Since CT scans form an integral part of treatment planning and the execution of the treatment of patients, AR and VR were introduced in CT-scan imaging for oral and maxillofacial surgery to provide images of higher quality [6]. Such CT-scan images provided better visualization for surgeons, of various anatomic structures in the area of the operative field. For a successful root canal treatment, the, detection of all canal orifices is crucial, so AR and VR use in endodontics has been explored with real-time detection of root canal orifices [19]. Since it is known that the identification of all root canal orifices is of prime importance for the success of root canal treatment, the use of AR and VR technology in endodontics can prove to be fruitful for endodontists.

For the correction of malocclusion in patients, at times, surgical corrections are required during their orthodontic treatment. So, AR and VR have been used in patients requiring surgical orthodontics where the guided placement of brackets for orthodontics correction was performed [20]. This method captured several sequences of patients’ video to help improve the robustness, performance, and accuracy for more efficient orthodontic treatment. For students, to improve their knowledge and clinical skills, AR and VR have been introduced to further improve the level of education of students during their undergraduate years [21].

4. Applications of AR and VR in Dentistry

4.1. AR and VR in Dental Specialties

AR and VR have their use in a variety of specialties of dentistry, as presented in Figure 1. AR and VR technologies have a promising role in the field of dentistry. The details of its application in oral health are described below.

4.2. AR and VR in Dental Education/Training

Traditionally, the training of dental students has been conducted on phantom headsand teeth to practice and improve their clinical skills before performing treatments onpatients. These simulators allow teachers to demonstrate the treatment techniques andaim to enhance the manual dexterity of the students. The use of such simulators makes itmandatory for the students to give their teachers constant feedback about their progressbefore moving to different treatment techniques.

In the delivery of dental education and training, instructors can help students andPG residents to achieve precision in pre-clinical/clinical skills, respectively, with 3D real-time digital simulations as well [1,9]. Learning and retaining the anatomy of the headand neck is a crucial part of dental education. Lectures and 2D images from textbooks ofanatomy have been used for teaching this subject to students [10]. In this traditional modeof teaching, cadaveric skulls are commonly employed, and students are instructed throughthese. However, the visualization of all associated muscular, neural, vascular, and otherstructures is quite challenging for students and it is not fully effective either [22].

In the midst of the COVID-19 pandemic, students suffered due to limited learningopportunities and the ability to enhance their pre-clinical skills as students could not trainat their universities without the instructor’s direct supervision. Therefore, helping thesestudents to learn while controlling the spread of COVID-19 has been the most challeng-ing aspect for the universities. Amidst the quest for better teaching methodologies, onegroup described an innovative technique to teach clinically relevant anatomy to studentsof dentistry that replaces cadavers with dissected and sliced plastinated specimens [8].However, one recent study incorporated digital tools and a 3D augmented curriculum,which is an interactive 3D experience that combines the view of the actual world withelements generated by computers along with traditional teaching methods (lectures andcadavers). The study demonstrated improved understanding and a positive influence on the retention of anatomical knowledge in students as compared to the control group (taughtvia textbooks/2D images) [23].To further increase the knowledge of dental students, virtual reality allows the studentsto watch oral treatments as a direct participant. Moreover, students can also try to reproducethe oral treatment scenario under the guidance of professionals.

4.3. AR and VR in Oral and Maxillofacial Surgery

Oral pathologies such as oral squamous cell carcinoma, cleft lip and palate, and congenitalabnormalities are common findings that are treated by oral and maxillofacial surgeons. Manyof these pathologies are treated by surgeons using their manual dexterity along with theiryears of experience. In recent years, many technological advancements have taken place inthe field of surgery such as the introduction of augmented and virtual reality [24].

The application of AR and VR technology has been explored in many surgical fields ofmedical science, such as laparoscopic surgery, neurosurgery, and plastic surgery. In dentistry, the use of AR in oral and maxillofacial surgery has focused on the placement of dental implants, craniofacial surgery, and orthognathic surgery. The use of AR technology allowsthe users to combine information and images to bring them to reality.

The training period of surgical residents is a crucial phase where the residents learn and practice their surgical skills on different simulators before actually performing on patients. Pulijala et al. [14] evaluated the effectiveness of virtual reality in surgical training and found that many of the surgeons were not confident about performing the surgeries. With the introduction and implementation of VR technologies, this has resulted in surgical residentsimproving their knowledge and confidence whilst performing the surgeries. VR is an additional tool that has immense importance in further enhancing the skills already possessed by surgeons to achieve optimal outcomes that boost confidence amongst surgeons.

Inferior alveolar block anesthesia is one of the most fundamental anesthesia used in dentistry to operate on the mandibular teeth for procedures such as root canal treatment, extractions, dental fillings, and complex surgeries. Many factors have been associated with the failure of inferior alveolar block anesthesia such as poor technique, and anatomical variations. In a study by Won et al. [17], AR was used for inferior alveolar block anesthesia and it was concluded the use of AR in this block anesthesia can improve the effectiveness when block anesthesia is used alone. AR helps in improving the precision and accuracy of using block anesthesia as the images that are directly generated from the patient help in converting those images to reality.

One of the most widely studied applications of AR and VR in dentistry is orthognathic surgery. The prime advantage of using AR-guided navigation tools is that it provides real surgical images and virtual surgical plans to guide through the treatment plan. One of the important surgical procedures in orthognathic surgery is mandibular angle split osteotomy. Mandibular angle split osteotomy is a cosmetic surgical procedure that aims to improve the prominent mandibular angle, thereby improving the aesthetics of the patient. In their study, Zhu et al. [18] used AR for mandibular angle split osteotomy and found that the use of AR enhances the translocation of the maxilla in orthognathic surgery. The use of such AR systems allows surgeons to operate real-time streaming video images that allow them to plan the surgery and study the anatomical structures of the patient, thus enhancing the accuracy of such orthognathic surgical procedures.

The use of AR has also been studied in distraction osteogenesis. In a study by Qu et al. [25], patients suffering from hemi facial macrosomia were treated with an intraoral distractor using AR and it was found that AR was more accurate in proper positioning of the osteotomy planes as compared to the conventional methods. Additionally, one study explored the use of AR systems where images were overlaid, which allowed surgeons to observe and follow the virtual surgical plans to reposition the bones of the patient after performing maxillary osteotomies [5]. Additionally, to further enhance the surgical skills, VR technology replicated different functions such as drilling, place fixation, and bone sawing with the help of hepatic force feedback [28,29].

So, the importance of VR and AR in oral and maxillofacial surgery can be appreciated given the improved accuracy of the surgery performed, the decrease in the chance of errors by the surgeons, and the unlimited number of training sessions available to surgeons. Therefore, VR and AR as an adjunct can prove to be useful tools for surgeons.

4.4. AR and VR in Paediatric Dentistry

Pediatric dentistry is one of the most challenging specialties of dentistry as the commonest factor determining the treatment outcomes in such patients is their compliance. To improve patient cooperation and compliance, different tools have been used ranging from the armamentarium of the dentist, such as behavior modification, and pharmacological interventions. Pediatric patients who are visiting the dental practice often present with tremendous amounts of anxiety as most of the time it is their first interaction with dentists [30]. So, managing the anxieties and behavior of children is one of the crucial factors in patient management.

To decrease the levels of anxiety and stress of such patients, virtual reality is one of the innovative tools that have been discussed in the literature, although to a limited extent. Different techniques to manage anxiety include in vivo exposure therapy (IVET) and virtual reality exposure therapy (VRET). IVET consists of the direct confrontation of patient’s fear to reduce their anxiety levels and this method has been categorized as a gold standard method. VRET is a recent technique that consists of computer-generated images for patients where the simulation makes the patient experience their fears without facing them in reality, thereby helping them to reduce their anxiety [31]. In a study by Ran et al. [9], the effect of virtual reality on the behavioral management of children was studied, where it was concluded that the average anxiety and behavioral scores of the patients with virtual reality was significantly reduced as compared to the control group. Since virtual reality makes use of interactive and creative audiovisual representations of information that is attractive to children, such a method of anxiety reduction can be beneficial.

Another study by Osama et al. [10] assessed the effect of virtual reality on the pain and anxiety of pediatric patients during infiltration anesthesia, where it was found that virtual reality was effective in reducing the anxiety and stress of these patients. Since the patients experience the entire scenario virtually before the actual procedure commences, this helps patients to understand the treatment and face their fears. So, one of the most important factors that determine the treatment outcomes in patients in this age group is the anxiety and stress associated with visiting the dental practice. Virtual reality can help to provide an artificial environment that is more relaxing for the patients, which can help them forget their fears.

4.5. AR and VR in Dental Implantology

Many advances have been made in dentistry in regard to the replacement of missing teeth or teeth in the mandibular and maxillary arches of patients such as removable dentures, fixed dental prostheses, and dental implants. Dental implants have emerged as a suitable and preferable choice for many patients because of their high success rate and the long-term benefits associated with them [27,32]. The introduction of AR technology in dental implants has significantly improved many procedures associated with the placement of implants. Initially, the AR surgical navigation technology was used to place implants using the retinal imaging display as the surgeon keeps his visual on the operative area, avoiding the need for the surgeon to turn away [33].

In a study by Jiang et al. [12], it was found that the use of augmented reality resulted in higher accuracy and applicability for guided placement of dental implants as compared to the traditional two-dimensional navigational method. Such AR navigation systems help the surgeon to concentrate only on the site of the implant placement, thereby providing only useful information to the surgeon, which eventually reduces the cost and time of the procedure [34]. It is of prime importance that the location of the implants should be as accurate as possible because negligence in this step of implant placement could be one of the factors responsible for future implant failure.

Moreover, one study used augmented reality-based dental implant placement to evaluate the virtual placement of the implant as compared to the actual prepared implant site created [27]. In this study, it was found that the use of augmented reality resulted in a significantly decreased deviation in implant placement from the actual planned site. Since AR navigation-based systems help the surgeon to accurately locate and place the dental implants, the accuracy of such procedures thereby increases as compared to the traditional methods.

The placement of the dental implant is a surgical procedure, so with the help of VR technology, patients have an opportunity to get a detailed explanation of the treatment and what they will experience while the treatment is being performed. Complete information given to the patients with the help of VR makes them better prepared mentally.

4.6. AR and VR in Restorative Dentistry and Endodontics

Restorative dentistry and endodontics are some of the most challenging and exhausting fields of dentistry. In order to treat diseases such as dental caries, pulpitis, and dental abscess, knowledge and clinical skills are required to become a proficient clinician [35]. A high caries rate is prevalent throughout the globe, which mandates a visit the dentist and may require dental fillings or even root canal treatment as well. These treatments are performed to save a tooth that might require extraction if not managed in a timely fashion. Many factors are associated with failed dental fillings and endodontic treatments such as isolation, poor technique, smoking, under filled canals, and missed canals [19].

Conventionally, students are first trained in the laboratory on a phantom head where the mannequin mimics the patient, which allows the students to work as if they are working on an actual patient as in a clinical setup [36]. Procedures such as cavity preparation are practiced on these mannequins by the students. In a study by Llena et al. [16], cavity preparation using AR technology was studied. In this study, it was found that the participants that used AR technology showed an improvement in their knowledge and skills. With the help of AR, realistic simulations can be delivered to the students in order to practice and improve their clinical skills without the need for live test subjects.

To overcome the chances of failure in endodontic treatments in patients, augmented reality has been used in endodontics for the reliable detection of root canals. In a study by Bruellmann et al. [19], augmented reality was used to detect root canals where it was found that overall higher sensitivity was noted in detecting root canals in molars and premolars. The success rate of root canal treatment directly depends on identifying all of the root canals as any missed canal has pulp remnants that might trigger pain for the patient [37,38].

5. Clinical Implications of Haptic Feedback in AR/VR

Haptic feedback refers to the experience of physical resistance or vibration upon manipulating oral structures with a hand-held VR tool. Augmented or virtual reality combined with haptic feedback provides a realistic environment for dental operations. Dental procedures mostly require a bi-manual technique of instrumentation inside the oral cavity. Simulating this with haptic feedback is a challenge for software developers in the healthcare industry. Simulating the force response of oral structures and contact of rigid and deformable structures is necessary to carry out accurate haptic interactions in a virtual environment [39].

Practicing on virtual patients with real-time haptic feedback allows dental surgeons or students to perform routine and complex procedures quickly and with efficacy, although some studies have pointed out serious limitations for users working with haptics [40].

6. Whether to Embrace AR/VR Systems or Not?

In dentistry, the potential impact of the AR and VR technology is tremendous because all the natural occurrences that take place when a procedure is performed on a real patient can be simulated as well, e.g., during training for a root canal procedure, bleeding upon perforation of the pulpal floor can be experienced by immersion in the virtual environment (VR goggles plus haptic peripherals) [41]. Given the recent pandemic, a keen focus on the education of dental students utilizing cutting-edge technology is warranted to enhance clinical skills [42]. Research in the field of dentistry can also employ AR/VR systems to investigate study participants remotely in a 4D environment (Hologram); this would reduce study-related expenditures as well and conveniently tackle the issue of ethical sensitivity in some studies. With virtual reality simulators, the wastage of materials is reduced as students/dentists do not need to practice on artificial teeth and models [43].

Therefore, virtual reality applications are also beneficial in preserving the natural environment. The benefits of AR/VR-based dentistry and conventional dentistry are shown in Table 2. All such results have led to a surge in interest in these technologies. However, the visual fatigue caused by a stereoscopic view in children and adults is concerning [3]. Pediatric and geriatric patients in dental care settings could be negatively affected by frequent and repeated exposures to AR/VR environments [9,10,38,44,45]. This needs to be evaluated through repeated randomized control trials (RCTs) of dental procedure-based simulations in patients of different age groups. Based on cognitive load theory (CLT), explorative studies with appropriate and validated questionnaires given to large numbers of participants should be conducted to validate the reports of cyber sickness and sensory overload associated with AR/VR-based training and treatments.

When there is an equipment failure in dental clinics, it might take a long period of time for the technician to arrive and perform the repair. However, with the help of AR, a repair can be performed quickly by the use of a head-mounted display where the dentist coordinates with the technician remotely and repairs the equipment themselves [46–49]. However, since the cost of AR and VR technology is high for the majority of dental clinics, the benefits of such technology are yet to be further explored.

7. Future Recommendations

Virtual reality creates a learning opportunity for dental surgeons to practice safe and efficient dentistry with a constant feedback mechanism. The current ongoing pandemic has demonstrated the importance of infection control in all healthcare environments now more than ever. Considering this, augmented and virtual reality-based dentistry may be even more applicable post-pandemic than before. It cannot be stressed enough that educators and clinicians need to consider the pros and cons before investing in the armamentarium required for AR/VR applications. Collaboration between experts working in the fields of Medical Informatics and Public Health Informatics with clinicians to translate AR and VR-based treatment planning and procedures into routine clinical work is an active area for future research. Moreover, further exploration is needed to evaluate the usefulness of AR/VR in dental education for different dental practitioners to practice different treatments independently.

8. Conclusions

The field of dentistry is advancing at a rapid pace, in this regard, new technologies are being developed that a dentist could benefit from; these benefits include better visualization potential, reduced operative time, better patient consultation and promising treatment outcomes. The use of AR and VR has been studied in different fields of dentistry, but there were limited studies assessing its use. In this review, augmented reality and virtual reality have been found to be beneficial tools for clinical practice in the field of oral maxillofacial surgery, preventive dentistry, endodontics, and orthodontics. Clinicians can use virtual reality technology to show their patients the expected outcomes before they even undergo any procedures. AR and VR also have a potential role in dental education through enhancing the learning experience for students during their pre-clinical education and training. Additionally, AR and VR can also be implemented to overcome dental phobia, which is commonly experienced by pediatric patients. Future studies should focus on forming technological standards with high-quality data and developing scientifically proven AR/VR gadgets for dental practice.

Author Contributions: Conceptualization, A.L., S.F., N.A., M.K.A., A.M., G.D., S.S. and A.A.G.K.; methodology, A.L., S.F., N.A. and A.M.; software, N.A., G.D., M.K.A. and A.M.; validation, M.K.A., N.A. and A.L.; formal analysis, A.L. and N.A.; investigation, A.L., S.S. and A.M.; resources, M.K.A., A.A.G.K. and S.S.; data curation, A.L. and N.A.; writing—original draft preparation, A.L., S.F., N.A., M.K.A., A.M., S.S. and A.A.G.K.; writing—review and editing, N.A., M.K.A. and A.M.; visualization, A.L., M.K.A. and N.A.; supervision. A.M. and N.A.; project administration, A.L., N.A. and S.F.; funding acquisition, M.K.A., G.D., S.S. and A.A.G.K. All authors have read and agreed to the published version of the manuscript.

Funding: This research was funded by the Deanship of Scientific Research, King Khalid University, Abha-Asir, Kingdom of Saudi Arabia under the Small Research Group, with the grant number, RGP.1/336/42.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Data Availability Statement: The data presented in this study are available on request from the corresponding author.

Acknowledgments: Authors thankfully acknowledge the Deanship of Scientific Research, King Khalid University, Abha-Asir, Kingdom of Saudi Arabia for funding this research work under the Small Research Group, with the grant number, RGP.1/336/42.

Conflicts of Interest: The authors declare no conflict of interest.

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01 Jun
info

Computer-Based Technologies in Dentistry: Types and Applications

Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2016; Vol. 13, No. 3)

Abstract

During dental education, dental students learn how to examine patients, make diagnosis, plan treatment and perform dental procedures perfectly and efficiently. However, progresses in computer-based technologies including virtual reality (VR) simulators, augmented reality (AR) and computer aided design/computer aided manufacturing (CAD/CAM) systems have resulted in new modalities for instruction and practice of dentistry. Virtual reality dental simulators enable repeated, objective and assessable practice in various controlled situations. Superimposition of three-dimensional (3D) virtual images on actual images in AR allows surgeons to simultaneously visualize the surgical site and superimpose informative 3D images of invisible regions on the surgical site to serve as a guide. The use of CAD/CAM systems for designing and manufacturing of dental appliances and prostheses has been well established. This article reviews computer-based technologies, their application in dentistry and their potentials and limitations in promoting dental education, training and practice. Practitioners will be able to choose from a broader spectrum of options in their field of practice by becoming familiar with new modalities of training and practice.

Keywords: Virtual Reality Exposure Therapy; Immersion; Computer-Aided Design; Dentistry; Education


INTRODUCTION

Computer-based technologies play an important role in all aspects of our daily life as well as in dentistry. Simplified interactions between human and computer have caused a profound progress in virtual reality (VR)-based dental training. On the other hand, computer-aided design/computer aided manufacturing (CAD/CAM) of dental appliances and prostheses is now widely used around the globe [1]. Although many dentists have become familiar with CAD/CAM subgroup of computer-based technologies in the recent years, VR and augmented reality (AR) techniques, which are going to find their place in learning and instruction of dental skills, are not as much known [2].

In this article, different types of computer-based technologies including VR and AR simulators, CAD/CAM systems and their applications in dentistry are reviewed.

Virtual Reality Technology

Virtual reality technology is defined as a method by which, an environment is three dimensionally simulated or replicated, giving the user a sense of being inside it, controlling it, and personally interacting with it [3,4]. The virtual environments are almost completely generated by computers [5]. Technology has a wide range of probable benefits in many aspects of life like construction of a building by providing a highly detailed virtual three-dimensional (3D) model of the building to verify each part of the plan, the cost and layout [6]. Similarly, in designing a new product, the virtual prototype can be used instead of physical prototypes to evaluate the design from different aspects [6]. In the medical field, VR is used for instruction of surgical procedures [7,8], education of patients and training students [9-12]. It also helps in treatment of psychological disorders by providing a valid controlled virtual environment to objectively assess the behavior and rehabilitate cognitive and functional abilities [3]. It is successfully used for treatment of complex regional pain syndrome as well [13]. The 3D virtual sceneries help improve dental experience via distraction intervention [14].

Features of VR

Virtual reality depends on two basic features namely immersion and interaction.

Immersion is the sense of being present in a virtual (non-real) environment. The environment is generated by synthesizing 3D images, sound and other stimuli, which surround the users and make them feel being physically present in a nonphysical (non-real) world [15]. The degree to which, the user believes being present in a virtual environment (immersion) is different in various systems ranging from fully immersive to non-immersive, depending on the capabilities of the system [6].

Interaction is the power of user to modify the virtual environment [15]. This feature is the main difference between 3D movies and virtual environments. In VR systems, the user is able to interact with the virtual world, moving around it, seeing it from different angles, reaching it, grabbing it and reshaping it. This sort of interaction is possible by means of head mounted video goggles, wired clothing and fiber-optic data gloves. Position-tracking devices and real-time update of visual, auditory displaying systems are also necessary [16].

Types of VR Systems

Virtual reality systems are classified into three major groups of non-immersive, semi-immersive and immersive (Fig. 1) based on the immersion and type of components utilized in the system [6].

Immersive VR simulation is a technology that gives the user the psychophysical experience of being surrounded completely by a virtual computer-generated environment (Fig. 2) by using hardware, software and interaction devices. Full immersion is the highest level of immersion, which is produced by a head mounted device that displays images three dimensionally via a process known as stereoscopy. In this process, the user sees two images -one per eye- and the brain combines them into a single 3D image. The other components are data gloves, which enable the person to interact with the objects, for example, pulling, twisting or gripping them and may also give a force feedback to the user, which is known as haptic. There are also tracking devices, which track user’s head, hands, fingers, eyes and feet to enable interaction with the virtual world. Sound is displayed as well. In fully immersive virtual environments the user is completely separated from the real world [17].

Semi-immersive VR simulation is a system in which the user stands in a room with rear projection walls, down projection floor, speakers at different angles, tracking sensors in the walls and sound/music devices (Fig. 3). By wearing eye goggles, the user sees everything three dimensionally. Since the user can still see him/herself, the system is not considered a fully immersive simulator. Cave Automatic Virtual Environment is an example of these systems [18].

Non-immersive VR simulation is the least immersive and least expensive of all. It allows the user to be involved with a 3D environment just by incorporating a stereo display monitor and glasses. They can be run on a standard desktop computer using mouse and joystick (Fig. 4). It is mostly used in designing and CAD systems [17].

Applications of VR in Dentistry

Although the VR simulation systems are used in different aspects of medical training such as laparoscopic surgery [19], their use in dentistry is not an easy task. The reason can be sought in complexity of dental instruments in type, shape and speed, and the diversity of oral tissues, which include gingiva, multilayer teeth and bone.

To simulate tooth reduction in dental virtual reality systems, the operator uses a stylus, which with the help of worn special goggles appears as the intended instrument like high or low speed hand piece in the 3D displaying stereoscopic monitor. The process mandates accurate digitized models of the instruments and oral cavity tissues and sophisticated graphic programs for showing the reduction of tooth. Unlike the monolayer resin models generally used for preclinical training, different layers of tooth like enamel, dentin and dental pulp are modeled in VR systems. This helps dental students to avoid unintentional exposure of dental pulp during preliminary clinical practice [20].

The differentiation between various structures or speed of the instrument is only possible with the help of haptic devices. They enable the user to feel the force required for each practice (force feedback) and provide a realistic tactile sense, just like working on real structures with real instruments.

In surgery, haptic devices allow surgeons to touch and feel objects such as surgical tools and human organs in a virtual environment, and to perform operations like pushing, pulling, and cutting of soft or hard tissue with realistic force feedback. Another advantage of VR simulators is that they are programmed to identify errors and assess the quality of performance. Experts determine the errors and the best performances, which would be the basis for comparison and assessment. The system is able to record and replay the performance of each user as well, which allows them to know their faults and fix them. It is also possible to practice and receive assessment as many times as required at any time, which is not possible with programmed traditional classroom instruction [21].

Augmented Reality

Augmented reality refers to superimposition of computer-generated graphics over a real-world scene [22]. In contrast to VR simulators, in AR the real environment is not completely suppressed and in fact plays a dominant role in this process (Table 1). Augmented reality aims to add synthetic additives to the real world (or to a live video of the real world) instead of engaging a person in a world, which is completely generated by a computer [23]. It is widely used in image guided surgery, where real and virtual objects need to be composed, integrated, presented or manipulated simultaneously in a single scene [24]. It is also applied in dental implantation, maxillofacial surgery, temporomandibular joint motion analysis and prosthetic surgery [8,9].

One of the main uses of AR in oral and maxillofacial surgery is in visualization of deep masked structures. Before surgery, the surgeon would be able to map the surgical plan on the 3D image of the site and consider any necessary modifications. During surgery, the surgeon sees and follows the mapped image overlaid on the surgical site by use of special glasses. This system can be developed for root canal therapy as well [24].

In some systems, both AR and VR technologies are used together in order to enhance the training capacity of the system. Developers of such systems believe that this integration improves the performance of users.

Future of VR and AR in Dentistry

The VR and robotics as new technologies will have a great impact on health care in the next decades [25]. The dynamic association of operation on a real organ with imaging data may create new modes of diagnosis and treatment for technically challenging patients. Experienced surgeons will benefit the most from such systems by extending the safe limit for more efficient operations, while less experienced surgeons may at least benefit from better visualization and orientation of critical anatomical landmarks [8]. The VR and AR systems seem promising, but there are still technological challenges that researchers and developers must face in order to fulfill these promises.

Dental CAD/CAM Systems

The evolution of dental materials and advances in computer science led to a rapid development in dental CAD/CAM technology. During the past couple of decades, many advanced chairside and laboratory CAD/CAM systems were introduced. Computers are used to collect data and design and manufacture a wide range of products in CAD/CAM systems. These systems have long been used in industries but they were not available for dental applications until the 1980s [26]. Nowadays, the term CAD/CAM in dentistry is equal to manufacturing by milling technology. However, it is not completely true, because manufacturing can either be by subtractive (milling) or additive technologies [27,28].

The CAD/CAM systems consist of three components:

1- A digitization tool/scanner that transforms geometry of a real world object into digital data to enable processing by a computer.

2- Software for data processing.

3- A technology, which manufactures the desired product from the digitized data set [27].

At present, many fixed prosthetic restorations are manufactured by the CAD/CAM systems, using different types of materials such as porcelain, composite resin and metallic blocks. Even materials like zirconia, which could not be manufactured by the conventional methods previously because of technical limitations, can now be fabricated by these systems [29]. The CAD/CAM systems are going to find substantial applications in implant dentistry to manufacture implant-supported prostheses, abutments and diagnostic templates [30].

The main benefit of this type of manufacturing in dentistry is that conventional impressions are not needed anymore, which is believed to save the dentist’s chair time and eliminate a time-consuming step [31]. Table 2 shows the advantages and limitations of CAD/CAM systems. The CAD/CAM techniques and rapid prototyping are extensively used in treatment of maxillofacial defects and surgeries [32]. These techniques are also used for designing and manufacturing removable partial denture metal frameworks through 3D printing [33] and by collecting 3D data from the patient’s cast, determining the path of insertion and designing the shape of the components of the frameworks digitally. The completed model data are stored as stereo lithography files, which are transferred to rapid prototyping models. Finally, metal removable partial denture frameworks are fabricated by selective laser melting technique [34].

The CAD/CAM technology is used in orthodontic diagnosis, treatment planning [35] and fabrication of appliances (Invisalign Production Process) which include submitting of the scan or impressions and photographs to the company with the doctor’s instructions. These intraoral scans or impressions will be used to design an accurate 3D digital model for each dental arch, after that a stereolithographic model will be fabricated for each step. Finally, a clear plastic aligner will be made over each model, and the set of aligners are then sent directly to the doctor [36].

Also, it is used in determining the position of impacted maxillary canines and for the fabrication of occlusal splints. However, CAD/CAM/additive manufacturing innovations have not been used successfully on a wide scale for removable orthodontic appliances [35].

In the CAD-CAM systems, virtual articulator is a basic tool that deals primarily with the functional aspects of the occlusion and is a core tool in many diagnostic and therapeutic procedures. With the introduction of virtual articulators a bright future will be expected and a revolutionary change will occur in digital dentistry [2]. Table 3 shows the applications of computer-based technologies in dental aspects.

CONCLUSION

At present, computer-based technologies are well established in designing and manufacturing dental appliances and prostheses. However, simulation systems for the instruction of dental skills are the new modalities not much known or widely used and only a few dental schools are using them at the time being. These systems are under constant progress and development. They are still too expensive and their maintenance and repair costs are high like any other new technology. On the other hand, computer-assisted skill acquisition in conjunction with traditional training would enable students to practice repeatedly, with constant assessment and force feedback, which is not routinely possible with resin models. In the surgical fields, simulation systems enable the students to practice in real mode on virtual subjects. They also offer visual information about the surgical site, which is of great use for the surgeons.

References

1- Jevremović DP, Puškar TM, Budak I, Vukelić D, Kojić V, Eggbeer D, et al. An RE/RM approach to the design and manufacture of removable partial dentures with a biocompatibility analysis of the F75 Co-Cr SLM alloy. Materiali in Tehnologije. 2012 March;46 (2):123-9.

2- Gugwad R, Kore A, Basavakumar M, Arvind M, Sudhindra M, Ramesh C. Virtual articulators in prosthodontics. Int J Dent Clin. 2011;3(4):39-41.

3- Schultheis MT, Rizzo AA. The application of virtual reality technology in rehabilitation. Rehabil Psychol. 2001 Aug;46(3):296-311.

4- Ausburn LJ, Ausburn FB. Desktop Virtual Reality:A Powerful New Technology for Teaching and Research in Industrial Teacher Education JITE. 2004 Winter;41(4): 1-16.

5- Connacher HI, Jayaram S, Lyons KW. Virtual assembly using virtual reality techniques. Comput Aided Des. 1997 Aug;29(8):575-84.

6- Mujber TS, Szecsi T, Hashmi MSJ. Virtual reality applications in manufacturing process simulation. J Mater Process Technol. 2004 Nov;155(156):1834-8(Confrence Proceedings).

7- Botden SM1, Jakimowicz JJ. What is going on in augmented reality simulation in laparoscopic surgery? Surg Endosc. 2009 Aug;23(8):1693-700.

8- Shuhaiber JH. Augmented reality in surgery. Arch Surg. 2004 Feb;139(2):170-4.

9- Dutã M, Amariei CI, Bodan CM, Popovici DM, Ionescu N, Nuca CI. An overview of virtual and augmented reality in dental education. OHDM. 2011 Mar;10(1):42-9.

10- Rhienmora P, Haddawy P, Khanal P, Suebnukarn  S, Dailey MN. A virtual reality simulator for teaching and evaluating dental procedures. Methods Inf Med. 2010;49(4):396-405.

11- LeBlanc VR, Urbankova A, Hadavi F, Lichtenthal RM. A Preliminary Study in Using Virtual Reality to Train Dental Students. J Dent Educ. 2004 Mar;68(3):378-83.

12- Buchanan JA. Experience with virtual realitybased technology in teaching restorative dental procedures. J Dent Educ. 2004 Dec;68(12):1258-65.

13- Sato K, Fukumori S, Matsusaki T, Maruo T, Ishikawa S, Nishie H, et al. Nonimmersive virtual reality mirror visual feedback therapy and its application for the treatment of complex regional pain syndrome: an open-label pilot study. Pain Med. 2010 Apr;11(4):622-9.

14- Tanja-Dijkstra K, Pahl S, White MP, Andrade J, May J, Stone RJ, et al. Can virtual nature improve patient experiences and memories of dental treatment? A study protocol for a randomized controlled trial. Trials. 2014 Mar 22;15:90.

15- Ryan ML. Immersion vs. interactivity: Virtual reality and literary theory. SubStance. 1999;28(2):110-37.

16- Steuer J. Defining virtual reality: Dimensions determining telepresence. J. Commun. 1992 Dec 1;42(4):73-93.

17- Shahrbanian S, Ma X, Aghaei N, KornerBitensky N, Moshiri K, Simmonds MJ. Use of virtual reality (immersive vs. non immersive) for pain management in children and adults: A systematic review of evidence from randomized controlled trials. Eur J Exp Biol. 2012;2(5):1408-22.

18- Ponto K, Kohlmann J, Tredinnick R. DSCVR: designing a commodity hybrid virtual reality system. Virtual Reality. 2015 Mar;19(1):57-70.

19- Aggarwal R, Moorthy K, Darzi A. Laparoscopic skills training and assessment. Br J Surg. 2004 Dec;91(12):1549-58.

20- Mallikarjun SA, Tiwari S, Sathyanarayana S, Devi PR. Haptics in periodontics. J Indian Soc Periodontol. 2014 Jan;18(1):112-3.

21- Konukseven EI, Önder ME, Mumcuoglu E, Kisnisci RS. Development of a Visio-Haptic Integrated Dental Training Simulation System. J Dent Educ. 2010 Aug;74(8):880-91.

22- Van Krevelen DW, Poelman R. A survey of augmented reality technologies, applications and limitations. Int J Virtual Real. 2010 Jun;9(2):1.

23- Bimber O, Raskar R. Spatial augmented reality: merging real and virtual worlds. AK Peters, Wellesly, CRC Press, Tylor &Francis Group; 2005.

24- Takato T. New technologies in oral science. JMAJ. 2011 May-June;54(3):194-6.

25- McCloy R, Stone R. Virtual Reality in Surgery. BMJ. 2001 Oct 20;323(7318):912-5.

26- Liu PR. A Panorama of dental CAD/CAM restorative system. Compend Contin Educ Dent. 2005 Jul;26(7):507-12.

27- Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J. 2008 May 10;204(9):505-11.

28- Azari A, Nikzad S. The evolution of rapid prototyping in dentistry: a review. Rapid Prototyping J 2009 May 29;15(3):216-25.

29- Raigrodski AJ. Contemporary materials and technologies for all ceramic fixed partial dentures: a review of the literature. J Prosthet Dent. 2004 Dec;92(6):557-62.

30- Fuster-Torres MÁ, Albalat-Estela S, AlcañizRaya M, Peñarrocha-Diago M. CAD/CAM dental systems in implant dentistry: update. Med Oral Patol Oral Cir Bucal. 2009 Mar 1;14(3):E141-5.

31- Daniel J P. CAD/CAM Today: A 22-Year Retrospective. Inside Dent. 2008 Nov/Dec; 4(10).

32- Hughes CW, Page K, Bibb R, Taylor J, Revington P. The custom-made titanium orbital floor prosthesis in reconstruction for orbital floor fractures. Br J Oral Maxillofac Surg. 2003 Feb;41(1):50-3.

33- Bibb RJ, Eggbeer D, Williams RJ, Woodward A. Trial fitting of a removable partial denture framework made using computer-aided design and rapid prototyping techniques. Proc Inst Mech Eng H. 2006 Jul;220(7):793-7.

34- Han J, Wang Y, Lü P. A preliminary report of designing removable partial denture frameworks using a specifically developed software package. Int J Prosthodont. 2010 Jul-Aug;23(4):370-5.

35- Al Mortadi N, Eggbeer D, Lewis J, Williams RJ. CAD/CAM/AM applications in the manufacture of dental appliances. Am J Orthod Dentofacial Orthop. 2012 Nov;142(5):727-33.

36- Proffit WR, Fields HW, Sarver DM, Ackerman JL. Contemporary orthodontics. 5th ed.St. Luis, Elsevier-Mosby, 2013:355.

25 May
info

Computerized Virtual Reality Simulation in Preclinical Dentistry: Can a Computerized Simulator Replace the Conventional Phantom Heads and Human Instruction?

Copyright © 2017 by the Society for Simulation in Healthcare. Unauthorized reproduction of this article is prohibited.

(Sim Healthcare 12:332–338, 2017)

Summary Statement: In preclinical dental education, the acquisition of clinical, technical skills, and the transfer of these skills to the clinic are paramount. Phantom heads provide an efficient way to teach preclinical students dental procedures safely while increasing their dexterity skills considerably. Modern computerized phantom head training units incorporate features of virtual reality technology and the ability to offer concurrent augmented feedback. The aims of this review were to examine and evaluate the dental literature for evidence supporting their use and to discuss the role of augmented feedback versus the facilitator’s instruction. Adjunctive training in these units seems to enhance student’s learning and skill acquisition and reduce the required faculty supervision time. However, the virtual augmented feedback cannot be used as the sole method of feedback, and the facilitator’s input is still critical. Well-powered longitudinal randomized trials exploring the impact of these units on student’s clinical performance and issues of cost-effectiveness are warranted.

Key Words: Dental education, faculty, simulation training

Operative dentistry is a demanding area of clinical education. [1] The development of clinical competence requires the assimilation of large amounts of knowledge combined with the acquisition of clinical skills and problem-solving ability. [1] One of the most essential clinical skills in operative dentistry is preparing and restoring carious teeth. The student needs to comprehend the concepts of the procedure and develop the fine motor skills to perform it.[2] The acquisition of clinical, technical skills, and the transfer of these skills to the clinic, where real patients are treated, is of paramount importance.[3] This can be achieved by vigorous training on phantom heads.[4] Phantom heads provide an efficient way to teach preclinical students dental procedures safely while increasing their psychomotor skills considerably.[4,5]

Phantom heads have been the cornerstone of learning in operative dentistry worldwide since their introduction in 1894.[4] The phantom head is affixed to a dental operating unit with a torso, in a manner that allows adjustment of position to allow the students to work in a seated position as they would in a clinical setting.[3] The heads also have a rubber sheet, which provides an approximation of the patient’s cheeks and mouth opening (Fig. 1).[3] Phantom heads replicate the real-life clinical environment including positioning of the operator and the patient, performing dental procedures with an assistant, and infection control procedures.3 Traditionally in preclinical simulation training, the students are shown models, diagrams, and pictures and are asked to repeatedly perform dental procedures on plastic phantom head teeth.[6]The learners receive verbal feedback by a faculty instructor when they have completed all or a portion of a cavity or tooth preparation task (Fig. 2).[7]

In recent years, technological advances have facilitated the incorporation of virtual reality simulation technology in preclinical operative dental education. Virtual reality simulators provide the opportunity for integrating clinical case scenarios in the operative teaching environment and also facilitating the tactile diagnostic skills by utilizing haptic technology.[1] To date, two types of computerized virtual reality dental simulators are available: mannequin-based simulators on which certain dental procedures can be performed using real dental instruments (eg, DentSim TM and Image Guided Implantology IGI both produced by the DenX, Ltd) and haptic-based simulators, which employ a haptic device and virtual models of a human tooth or mouth as a platform for facilitating the practice of dental procedures (eg, PHANToM TM, Virtual Reality Dental Training System VRDTS, Iowa Dental Surgical Simulator, HapTEL, VirDenT & Moog Simodont Dental Trainer).[1,5,6]

The mannequin-based computerized simulators combine the benefits of training on a traditional phantom head operating unit,[3] with the benefits of virtual reality simulation.[8] These computerized virtual reality simulators (CVRS) were the focus of this review.

A computerized phantom head dental simulator, which incorporates virtual reality features and provides augmented visual feedback, is the DentSim unit.[1] It has been available since 1997 and has been used and evaluated in Dental Institutions in the United States, Europe, and Asia.[1,6,9–11] The unit includes a phantom head, a dental hand piece, a light source, an infrared camera, and two computers.

The phantom head and handpiece contain infrared emitters that allow the infrared camera to detect their spatial orientation in space.[6,8] As a student prepares a cavity in the phantom head, the software formulates a virtual three-dimensional representation of the preparation in progress, which is presented on the computer screen (Fig. 3).[6,8] The student’s cavity preparation can be compared with the ideal cavity preparation by overlaying the two virtual reality images at any time during the procedure[.6,8,12] Procedural errors are audio signaled as they are made and the generated error messages can be viewed immediately.[12]

A final evaluation report and a list of errors become available at the end of the procedure.6,12 The virtual environment is enhanced with complete patient records including examination notes and radiographs, which provide a more realistic environment, bringing the technical tasks into a clinical context, during the simulation training.12 The aim of this review was to examine and evaluate the existing body of literature on the use of the CVRS in preclinical dental education. The impact on student’s performance and learning experience, as well as the role of the faculty instruction versus the augmented visual feedback provided by these units, in the clinical skills acquisition simulation training, is discussed.

METHODS

A search of the literature was performed searching the following databases via EBSCO: Medline, British Educational Index, and ERIC. The search terms used and the search strategy can be found in Table 1. Articles in which the CVRS were discussed in terms of preclinical dental education were included. Studies using CVRS in postgraduate dental education as well studies using haptic technology simulation systems were excluded. Only studies in the English language were considered for inclusion. Finally, no limits for study design were applied.

The citations retrieved from the above search (79) were inserted into the reference management software Endnote X7.4. The titles and abstracts were screened for relevance. The potentially relevant papers (33) were accessed and read in full text. The selection process of the included studies (16) and the reasons for exclusion are depicted in the PRISMA flowchart (Fig. 4).

RESULTS

Impact on Student Performance

From the 79 articles retrieved, 16 were deemed relevant and were included in this review. From these, five prospective experimental studies assessed the students’ performance in cavity preparation after additional training on the CVRS. The main characteristics and results of these studies can be found in Table2. Concerning the quality of tooth preparations, most of the studies found no significant differences between those who trained solely on conventional phantom heads versus those who had been exposed adjunctively to the CVRS.[2,13,15,16]

Conversely, Kikuchi et al [9] demonstrated that students using the CVRS units performed better quality crown preparations than those who did not. Similarly, when first-year dental students received 8 hours of adjunctive computerized dental simulation training, although they performed better early in the study, their clinical performance did not differ as assessed by the final practical examination.[12] As the retention and transferability of skill and knowledge are concerned, several studies found no significant differences in the final practical examination scores.[12,14,17] LeBlanc et al [2] did not identify any marked differences in the final examination scores but observed a more significant improvement between the first and final assessment scores for the CVRS group. In contrast, Maggio et al18,[19] suggested that the introduction of the CVRS in preclinical dental training resulted in a reduction in the course remediation rate and reduction of the course failure rates by more than a half.

Time Efficiency

In an experimental study at the University of Pennsylvania, the students who received CVRS training showed a higher efficiency in cavity preparations than the students who trained on the traditional phantom heads.[14] Namely, they prepared significantly more teeth per hour (3.8 vs. 1.6) and used more teeth (average of 11.71 vs. 6.57 for control, P = 0.02) during their practising session.[14] Similarly, training sessions with CVRS shortened the crown preparation time performed by fifth-year dental students at Tokyo Medical and Dental University.[9] Besides, virtual reality simulators seem to reduce the required instruction and supervision time by faculty members of staff.[14] Jasinevicius et al [15] demonstrated that students who were trained on conventional simulators received five times more instructional time from faculty than students who were trained on virtual reality ones. However, there were no statistically significant differences in the quality of the preparations despite the additional instructional time.

Student Learning Experience

Several studies have surveyed dental students about their preferences over conventional or virtual reality simulation. The CVRS training seems to be rated rather positively by the students. Most (87.3%) of first-year students at Tennessee Dental school working with CVRS found the experience to be “very interesting” or “interesting.” [11] Among the positive features of virtual reality simulators, as perceived by dental students, were the positive impact on improving their manual and motor skills,[14] the increased speed and number of preparations,[10,14] the access to feedback,[16] the ability for the student to monitor their own work without involvement of a supervisor,[10,16] the preparation for assessment, the consistency of evaluation,[13,16] and the allowance for self-paced learning.[10,16] Students criticized the CVRS for excessive feedback, lack of personal contact, and technical difficulties with hardware.[13,16] In addition, students agreed that virtual reality simulators could not fully replace the conventional phantom heads, and the combination of the two is the most preferable and effective way of learning.[13,16] On the other hand, students found that the feedback and supervision by faculty facilitators can be inconsistent, and supervisors can be too busy, but it increases their confidence in cavity preparations.[13,16]

Feedback

As far as quality and effectiveness of instruction and feedback is concerned, several studies have suggested that the virtual reality simulator could not be accepted as the sole form of feedback and evaluation the students should be exposed to. Namely, Urbankova [12] concluded that CVRS-augmented feedback cannot replace human instruction. Quin et al [13,16] suggested that CVRS is not appropriate as a sole method of feedback and evaluation for novice dental students. This statement agrees with a later study in which sole CVRS feedback was not found beneficial, as the retention and transfer test scores between students who used CVRS versus conventional phantom heads did not differ significantly. [17] By the same token, Wierinck et al [7] have suggested that alternating virtual reality with human instruction and feedback can result in positive learning outcomes.

DISCUSSION

The role of simulation has been recognized as an important aspect of training in healthcare, which supports and improves patient safety. [20] Technology-enhanced simulation, including virtual reality training, has been associated with positive outcomes for healthcare trainee’s knowledge and skills. [21]

The use of virtual reality simulators for the training of novice surgical trainees has been supported by a number of systematic reviews.[22–26] In laparoscopic surgery, it has been shown to result in a significant reduction in operating time and procedural errors while improving the trainees’ performance scores.[23,24] Besides, two recent systematic reviews by the Cochrane Collaboration, in the fields of endoscopy and ear, nose, and throat surgery, suggested that virtual reality simulation can be used to supplement traditional surgical training for medical students and surgical trainees with little or no surgical experience.[25,26] Nonetheless, the authors concluded that virtual reality training allows trainees to develop technical skills at least as good as those achieved through conventional training.[25]

Similarly, adjunctive training on the dental CVRS has the potential to improve student’s clinical performance and enhance their practical examination scores.[9,12,13,17] The augmented feedback through visual cues can facilitate proper eye-hand coordination and reduce the number of procedural errors.[12] Confronting the students with their own errors as they are made allows them to visually inspect their work compared with an ideal model [16,17] and instantaneously rectify it, which can potentially increase learning efficiency and skill development.[12] Noteworthily, although students seemed to perform better early after the CVRS training, their clinical performance in final examinations did not differ from that of the students who trained solely on traditional phantomhead units.[12,14,17] The fact that the amount of transfer from one task onto another depends on the similarity of the neural processing demands, underlying motor execution, may offer an explanation.[17] Besides, the transferability of skills from one context to another is not an uncommon finding in healthcare simulation. Namely, studies in the fields of bronchoscopy, endoscopy, and laparoscopic surgery have shown that skills acquired using virtual-reality simulation will transfer to the operating room. [27–29]

Nonetheless, with the expansion of the dental curricular content, the effective use of student’s time has become an increasing necessity. [16] The CVRS training has shown to improve students’ efficiency in teeth preparations [9,14] and reduce the required time for faculty instruction and supervision.[15] Hence, the faculty instructors’ time can be used in teaching the students crucial nonprocedural skills such as patient management, ethics, and teamwork. Sharing their expertise and experiences in the transition of a student from novice to clinician remains critical. [7,12]

The unsuitability of the use of CVRS feedback as the sole method of feedback and evaluation for novice students is a consistent criticism among the included studies.[7,13,16,17] Although CVRS seem to be a reliable method for monitoring technical progress, addressing the issue of lack of reproducibility among assessors[13]; they cannot be used as a substitute for expert feedback. It has been suggested that the extensively detailed and sometimes complex computer feedback can be discouraging and overwhelming, especially for the inexperienced students.[15,17] Appropriate faculty input will reinforce learned theoretical concepts and will provide the students with insight into the weaknesses of their performance.[2,16] Contextual learning will enable the students to achieve a deeper understanding of theoretical concepts and the impact of any procedural errors (eg, the biological, clinical, and medicolegal implications of damaging an adjacent tooth or unnecessarily preparing a rather deep cavity).

In a modern preclinical environment, students will reflect on the feedback received by the simulator, the facilitator, or both. The CVRS can provide the student with continuous (100%) augmented feedback or they can be set to provide feedback less frequently or none at all. In traditional phantom head preclinical courses, the supervisors offer feedback at the end of critical parts of the procedure and the end of the task. Usually, the ratio of supervisors to students does not permit every student to receive constant feedback and instruction during the dental procedure. According to Wierinck et al,

[7] continuous (100%) CVRS feedback during the task did not offer any additional benefit over intermittent (66% of the time) feedback. Nonetheless, a recent meta-analysis suggested that terminal feedback seems more effective than concurrent feedback for novice learners’ skill retention.[30] The mechanism by which feedback may be operating is in line with the guidance hypothesis[31] and, to some extent, the cognitive load theory.[32]

The guidance hypothesis suggests that constant feedback from an instructor during each practice attempt (concurrent feedback) may lead to an overreliance on the feedback such that when feedback is withdrawn, the learner’s performance declines.[30,31] Reduced frequency of instruction may, therefore, enhance motor skill learning and detection of errors.[33] According to the cognitive load theory, feedback provided during a procedural skills session could influence cognitive load, either increasing it by providing “information overload” or decreasing it by structuring the task so that it is better understood.[30,32] Thus, it is plausible that continuous feedback may cognitively overload the learner and hinder their learning.[30]

The included studies assessed the suitability and effectiveness of the CVRS units as an adjunctive training tool for novice dental students. These units can also act as a valid and reliable screening device to capture expert performance. [8] Wierinck et al [8] suggested that the DentSim unit can distinguish different levels of excellence in performance (expert vs. novice). On that ground, CVRS may be used in other areas such as continuing dental education, continued competency of practitioners, clinical board examinations, and remediation of impaired practitioners. [6] Future research will be needed to explore the feasibility of CVRS in these areas. Furthermore, evidence for the long-term effect of CVRS training on the students’ clinical performance and competence as well as data regarding the cost-effectiveness of these devices is currently lacking. Future studies should conform to the extended CONSORT and STROBE reporting guidelines for healthcare simulation research,[20] to ensure complete reporting and transparency in the research conduct.[20,34]

CONCLUSION

The existing body of evidence suggests that combining and alternating the traditional and pioneering simulation methods and feedback may be of benefit to the learners. However, there is insufficient evidence to advise for or against the use of computerized virtual reality simulators as a replacement of the traditional phantom heads and human instruction. Virtual reality simulation may enable a better understanding among learners in a more diverse learning environment and augment rather than replace existing teaching methods that work well such as faculty instruction and feedback. Incorporating such a technology in the dental curriculum can add a substantial expense nevertheless to a dental faculty’s budget. Well-designed and adequately powered long-term prospective studies exploring matters of student performance, learning outcomes, and cost-effectiveness are warranted.

ACKNOWLEDGEMENTS

The author thanks the reviewers for their thoughtful comments that substantially improved the quality of this review. In addition, the author thanks Mr. Lloyd Russell (Digital marketing, Plymouth University, England, UK) for kindly offering the images appearing in Figures 1 and 2 and Professor Els Wierinck (KU Leuven – Department of Oral Health Sciences, University Hospitals Leuven, Belgium) for offering the DentSim images appearing in Figure 3. The author is a National Institute for Health Research–funded Academic Clinical Fellow at Peninsula Dental School (Plymouth University).

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17 May
info

Real-time in situ three-dimensional integral videography and surgical navigation using augmented reality: a pilot study

International Journal of Oral Science (2013) 5, 98–102; doi:10.1038/ijos.2013.26; published online 24 May 2013

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivative Works 3.0 Unported License. To view a copy of this license, visit http:// creativecommons.org/licenses/by-nc-nd/3.0

To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. Three-dimensional surface models of the jawbones, based on the computed tomography data, were used to create the integral videography images of a subject’s maxillofacial area. The three-dimensional augmented reality system (integral videography display, computed tomography, a position tracker and a computer) was used to generate a three-dimensional overlay that was projected on the surgical site via a half-silvered mirror. Thereafter, a feasibility study was performed on a volunteer. The accuracy of this system was verified on a solid model while simulating bone resection. Positional registration was attained by identifying and tracking the patient/surgical instrument’s position. Thus, integral videography images of jawbones, teeth and the surgical tool were superimposed in the correct position. Stereoscopic images viewed from various angles were accurately displayed. Change in the viewing angle did not negatively affect the surgeon’s ability to simultaneously observe the three-dimensional images and the patient, without special glasses. The difference in three-dimensional position of each measuring point on the solid model and augmented reality navigation was almost negligible (,1 mm); this indicates that the system was highly accurate. This augmented reality system was highly accurate and effective for surgical navigation and for overlaying a three-dimensional computed tomography image on a patient’s surgical area, enabling the surgeon to understand the positional relationship between the preoperative image and the actual surgical site, with the naked eye.

Keywords: augmented reality; computed tomography; integral videography; three-dimensional image.

INTRODUCTION

In oro-maxillofacial surgeries, the complexity of the involved anatomical structures often hampers direct visualization of the surgical site. Therefore, it is important to correctly grasp steric positional relations, such as the osteotomy line or the mandibular canal, while performing surgical procedures. Although most surgeons have precise knowledge of the underlying tissues, a better understanding of the three-dimensional (3D) relationships between these internal structures would greatly facilitate surgical procedures. Efforts in this direction have resulted in the advent of various techniques and instruments that enable direct visualization and manipulation of the surgical site, such as a conventional navigation system.1–2 However, a disadvantage of such systems is that the images obtained are two-dimensional, and therefore, necessitate constant comparisons between the surgical field and the displayed image, and consequently, frequent hand-eye transformations.3 The two-dimensional information gathered is thus indirectly recognized and understood, resulting in a potentially large gap between the actual

patient morphology and its interpretation through the imaging system. With 3D models too, smaller surface details might be smoothened away and information may be lost. Additionally, fixed planes of whatever orientation are no longer considered state-of-the-art 3D image analysis. Therefore, it is imperative that full access to the volume dataset itself is provided to the person and planes are interactively reconstructed per optimal visualization needs.

 Innovative imaging technology in the form of augmented reality (AR) technique, wherein the virtual and real scenes are merged into one environment, has been recently introduced to help oral surgeons visualize sites that cannot be directly observed. AR systems can provide navigated support whereby interpreted information from preoperative data can be superimposed on the surgical site in order to enhance the perception of the physical environment. Therefore, alternate viewing of the displayed image and the actual surgical area is no longer required, as both fields can be simultaneously observed. Furthermore, in situ visualization, which is possible with these systems, is advantageous as it is intuitive and improves the speed of execution of procedures.

This study examines the possible application of the novel AR technique in the field of oral and maxillofacial surgery. The algorithms and conditions required for 3D virtual representation of the surgical area have been defined by previous research, in which integral videographic (IV) images of only the mandibular component were included.3 However, this is the first study in which dentomaxillofacial 3D computed tomography (CT) data (both maxillary and mandibular jaws along with teeth (crown and root apices)) generated by a 3D IV image display system were superimposed on a human volunteer. In addition, the study evaluated if real-time in situ AR allowed accurate display of the stereoscopic images of the maxilla, mandible and teeth, even when viewed from different angles. Furthermore, a solid model was used to test the accuracy of this system by simulating tasks such as bone resection.

MATERIALS AND METHODS

Configuration of the AR system

The configuration of the AR system is shown in Figure 1. The IV image display, which has been developed at The University of Tokyo and previously described,[6–8] consists of a high-density rear liquid crystal display and microarray glass. By creating a lens array fixed to the display surface, non-distorted 3D images can be displayed.

The specifications of the IV image display system are as follows: a Pentium Core 2 Duo, 2.4-GHz processor; a NVIDIA Quadro Plex model 4 (Quadro FX 560032) graphics processing unit (GPU); a 6.5-inch, 1 0243768 pixel display (pixel pitch50.125 mm); and a fly’s eye lens array. The pixels on the display were computed such that the light rays generated by the pixels and the microarray lenses could accurately reconstruct 3D objects in real space, allowing the operator to observe the 3D IV image with the naked eye. The IV image was generated as shown in previous studies.[6–8]

Generation of 3D IV images from preoperative CT data

Briefly, the IV image of the 3D CT was constructed as an assembly of reconstructed light sources (Figure 2). No special glasses were required for viewing the IV image display, and motion parallax could be reproduced in all directions. The system was able to render IV images at a rate of 5 frames per second.

Feasibility study on a volunteer

This feasibility study of the AR system, performed on a volunteer, was conducted in accordance with the Good Clinical Practice guidelines and the Declaration of Helsinki, and the study protocol was approved by the medical ethics committee of the Graduate School of Medicine, The University of Tokyo. Informed consent was obtained from the volunteer before study initiation. X-ray CT diagnostic equipment

(Aquilion ONE; Toshiba, Tokyo, Japan) was used to acquire CT scans (slice thickness: 0.5 mm) of the orofacial region of the volunteer. Based on the obtained CT data, 3D surface models of the upper and lower jaw bones of the volunteer were constituted using the medical image processing software (Mimics; Materialise, Leuven, Belgium). In addition to these models, the function of medical image processing open source software (3D Slicer; http://www.slicer.org) was extended, and the GPU was set to an algorithm to produce IV images and perform real-time superimposition of the 3D image on the upper and lower jaw bones. The time required for preparing the 3D models within Mimics and/or Slicer was 5–10 min.

Registration and patient tracking. A 3D coordinate system is a prerequisite for image-guided surgeries.1 To integrate the coordinate systems between the subject and IV images, the Polaris Spectra optical tracking system (Northern Digital Inc., Waterloo, Ontario, Canada) was used. This system measured the position and direction of the subject’s movements in real time. The tracking marker was noninvasively attached to the subject’s tooth by using a dental splint (Figure 1a). The coordinate system of the IV images was obtained by measuring the position of the characteristics of these images in space. Similarly, the coordinates of the subject and those of the image were correlated by measuring the coordinate system of patient characteristics. By attaching an infrared reflective ball to the teeth and by measuring the 3D position of the infrared ball, the subject’s movements could be followed; thus, superimposition of stereoscopic images on the appropriate physical area was enabled in real time.

Instrument calibration. The tracking marker frames were designed to meet the following conditions:

  1. preserving the geometric uniqueness of the markers;
  2. ensuring that the surgical operations were not disturbed.

This system required calibration using point registration for the instruments. In order to measure the tracking marker position from the optical tracking system, the calibration was performed by careful pivot motion. Since the tracking marker frames can be rigidly mounted onto the body of the surgical instruments, the calibration needs to be performed less frequently (e.g., once every few months), which can be predetermined.

Real-time surgical navigation using AR

Using the same AR assembly, superimposed 3D images of the surgical instrument (SUCCESS-40MV; OSADA, Tokyo, Japan) in real time were displayed. The accuracy of the system when used in a clinical case was evaluated by performing the drilling task on a solid model imitating a bone surface. The solid model was a plastic block of size 90 mm340 mm310 mm. To integrate the coordinate systems between the object and IV images, the Polaris Spectra optical tracking system was used. However, in this case, the tracking marker was attached to the surgical instrument (Figure 1b). The coordinate system of the IV images was obtained by measuring the position of the characteristics of these images in space. While performing the feasibility study in the volunteer, by attaching an infrared reflective ball to the teeth and by measuring the 3D position of the infrared ball, the surgical instrument’s movements could be followed. Three infrared balls were mounted to the splint to track patient movements. In order to register the position of the solid model, instead of using an external marker frame, a landmark-based transformation was performed on the model. A surgical path, defined by a point of insertion and a direction, was pre-determined and its 3D IV image was overlaid onto the surgical scene. This surgical path works as the navigation tool that can inform surgeons of the direction in which drilling should be initiated. Additionally, to help the surgeon perform precise movements, two parameters were added to the navigation screen. The first parameter was the Euclidean distance from the tip of the Lindemann drill (Stryker Corporation, Kalamazoo, MI, USA) to the surgical path (in mm), and the second was the angle between the tool’s main axis and the surgical path. When the instrument was correctly aligned to the surgical path, the color of the instrument automatically changed to alert the surgeon that it was safe to proceed. The surgeon could then initiate the task. The simulation ended when the drill reached the target point on the other side of the model. By measuring the position of the drill holes on both sides, it was possible to compute the positional and angular errors during the simulated surgery. Another similar surgical navigation trial was performed using a surgical instrument that included a reciprocating saw (Stryker Corporation, Kalamazoo, MI, USA). The videos documenting all procedures (on the volunteer as well as those on the solid model) were filmed using an EOS Kiss X4 digital camera (Olympus Optical Co., Tokyo, Japan).

RESULTS

Positional registration was attained by identifying and tracking the subject’s position, and the IV images of the maxillary and mandibular bones and teeth could be superimposed in the correct position. In this system, the surgeon could view the internal structures in the 3D format, the data for which were initially obtained from the preoperative CT data and superimposed onto the actual subject’s anatomy through a half-silvered mirror. Supplementary Movies 1–3 show the surgical sites, as viewed by the surgeon. The movies demonstrate that by using the AR technique, stereoscopy is possible from every position and that the stereoscopic images are accurately displayed across different viewing angles. Supplementary Movie 3 demonstrates that this novel technique can also appropriately detect the subject’s movements. Since the IV images were updated at the speed of 5 frames per second, the stereoscopic images can be considered to be updated in real time. Furthermore, it was observed that change in the viewing angle, laterally or vertically, did not negatively affect the surgeon’s ability to observe the 3D images and visualize the subject, and allowed the surgeon to observe images as if the target areas were being viewed in real space, without special glasses.

Positional registration was also attained by identifying and tracking the position of the surgical instrument, and its IV images were superimposed appropriately. Supplementary Movies 4 and 5 show IV images of surgical navigation using the Lindemann drill and reciprocating saw, respectively. Accuracy of the system is indicated by the positional error (in mm) and angular error (*) displayed at the bottom of the screen. The positional error, using the Lindemann drill, ranged from 0.45–1.34 mm (average 0.77; standard deviations 0.19), whereas the angular error was 26. Similarly, in the trial using the reciprocating saw, the positional error ranged from 0.02–1.26 mm (average 0.68; standard deviations 0.26), and the angular error was 2*–4* (average 3.13; standard deviations 0.65), while the saw was cutting through the solid model. Since these values are negligible, this AR system can be considered as highly accurate. Additionally, the direction of movement of the surgical instruments was also correctly depicted in this study.

DISCUSSION

The use of image guidance in oral and maxillofacial surgery has offered better patient outcomes.2 The present study evaluated the application of a 3D imaging AR display system, incorporating IV, in oral and maxillofacial surgery. The IV technique displays 3D images, without requiring the user to wear special glasses, irrespective of the viewing position. Thus, it enables observation of stereoscopic images as if the objects were being viewed in real space. Although conventional imageguided surgery provides a 3D view of the patient’s anatomy, it is difficult to accurately correlate the displayed image to the surgical field.2 The AR display system transparently displays the 3D image directly on the surgical site, and the GPU-based rendering algorithm enables real-time tracking of patient’s movements, making it possible to update the 3D images in real time during an operation. The prime advantage of AR is that the surgeon does not need to alternate his/her attention between the surgical site and monitor, as is required in other systems, thus allowing for better focus, improved hand-eye coordination, and faster execution of surgical procedures. Liao et al.6 showed that the real-time IV algorithm for calculating 3D images of surgical instruments is as effective as that for both surgical instruments and organs in representing the real-time location during a surgery. The present study demonstrated the real time use of AR technology in surgical navigation as well as to generate IV images. Since the 3D image is superimposed in real space, it is possible to immediately recognize a discrepancy between the image and the actual patient appearance. Results from a previous study show that these positional errors were in the range of 2–3 mm,[6] but a recent study showed that use of the AR technique, as described in this paper, could decrease the mean positional errors to 0.7 mm.3 The positional error and angular error calculated in this study were 0.77 mm and 0.686, respectively, which is almost negligible. Thus, the technique demonstrated in this paper can be considered as highly accurate. This could be attributed to the fact that the Liao et al.’s6 study used a computer with specifications that were as follows: CPU, 800-MHz dual Pentium III processor with 1 GB memory; Windows 2000 Operating System; and old IV display (lens pitch, 2.32 mm; pixel pitch, 0.125 mm; and display size, 1 0243768 pixels). The system was then upgraded to Pentium Core 2 Duo and 2.4 GHz; GPU, NVIDIA Quadro Plex 1000 Model 4 with 4 GB memory; Linux Fedora Operating System; and new IV display (lens pitch, 1.0 mm30.8 mm; pixel pitch, 0.125 mm; and display size, 1 0243768 pixels) in the study by Tran et al.3 The same upgraded system was used in the present study. Modern navigation systems reference patient anatomy and obtain

data sets, mainly from skin surface scanning by using laser or by using anatomic landmarks or fiducial markers. A previous study used splints attached to the lower jaw, with titanium screws mounted on them to serve as fiducial markers for the registration process,9 whereas another study used two splints to fix the mandible to the viscerocranium—one each in the open and closed position.[10] Although the mobile nature of the mandible is known to generally pose problems for its intraoperative synchronization with preacquired imaging data,1 the IV images obtained with the AR technique in the present study were an exact reproduction of the patient’s internal structures.

Additionally, with the use of the novel AR technology, the position of the reflected IV image does not change even if the observer moves the eyes (i.e., changes the viewing angle). Furthermore, the IV image provides depth perception and allows multiple viewers to have different perspectives while observing from different directions. Results from previous studies using the AR technique for intraoperative navigation have shown its effectiveness, accuracy and feasibility in interstitial brachytherapy11 and maxillofacial surgeries.12 However, these studies employed projection of the image in real space, using a two-dimensional display projector and a 3D display by binocular stereopsis, which were set ups different from the one used in the present study. Other studies used a completely different approach to AR—some used a stereo video see-through head-mounted display as an individual navigation device,5,13 whereas others used the binocular stereopsis technology, whereby the observed video does not change in accordance with the change in viewing position, and thus, allows the surgeon to only determine relative depth.5,11–13 Without motion parallax, accurate 3D positioning cannot be reproduced. The IV technique, on the other hand, is based on a different principle than binocular stereopsis, and allows for both binocular parallax, a major component of depth perception, and motion parallax, where depth cues result from the motion of the observer. The new IV technology described in this paper allows the surgeon to determine exact 3D positional relationships by using both binocular parallax and motion parallax without the need for special viewing apparatus; this is not possible with conventional binocular stereopsis technology.

The present study evaluated the application of a 3D image AR display system in the field of oral and maxillofacial surgery. The results showed that a surgical site that cannot be observed directly could be visualized with correct steric positioning; thus, this AR system can be extremely beneficial while performing surgeries and can be a huge asset in the fields of dentistry and oral and craniomaxillofacial surgery. This system can be used to track 3D movements and 3D positions of blood vessels, nerves, tumors, cysts and impacted teeth intraoperatively. In orthodontics, this system can be used to visualize the 3D position and orientation of teeth at the time of correction. In conservative dentistry, the AR system may help determine the 3D location and relationship between an apical lesion and the root canal or the condition of a root canal. In dental implantology, this technology would be particularly useful for preventing damage to the underlying nerves and cortical plate perforations during implant placement.

The novel AR technology provides a complete 3D output and would therefore add to the precision and confidence of the surgeon. Using this system, the movement of the surgeon’s head does not require the image to be adapted and updated for the altered perspective, which is an advantage compared to other systems. Future research based on this study will focus on improving some of the technical aspects with regard to the accuracy and tracking system, such as a high-definition back display or lens array for the densification of pixels in the AR display to achieve high levels of precision and geometrical accuracy, which is important because the system provides a 3D image containing accurate spatial information. Further, the intended next step is to initiate clinical trials of this technology in patients to assess a multitude of applications of this technique.

CONCLUSION

In conclusion, this study presents an accurate AR system for use in oral and maxillofacial dentistry that provides a real-time, in situ, stereoscopic visualization of 3D-CT IV images overlaid onto the surgical site with the naked eye.

ACKNOWLEDGEMENTS

This work was supported by a Grant-in-Aid for Scientific Research (22659366) from the Japan Society for the Promotion of Science. Medical writing services were provided by Cactus Communications. The authors retained full control of manuscript content.

References

1 Casap N, Wexler A, Elisha R. Computerized navigation for surgery of the lower jaw: comparison of 2 navigation systems. J Oral Maxillofac Surg 2008; 66(7): 1467– 1475.

 2 Nijmeh AD, Goodger NM, Hawkes D et al. Image-guided navigation in oral and maxillofacial surgery. Br J Oral Maxillofac Surg 2005; 43(4): 294–302.

3 Tran HH, Suenaga H, Kuwana K et al. Augmented reality system for oral surgery using 3D auto stereoscopic visualization. Med Image Comput Assist Interv 2011; 14(Pt 1): 81–88.

4 Lubbers HT, Matthews F, Damerau G et al. No plane is the best one-the volume is! Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011; 113(3): 421.

5 Traub J, Sielhorst T, Heining SM et al. Advanced display and visualization concepts for image guided surgery. J Display Technol 2008; 4(4): 483–490.

6 Liao H, Hata N, Nakajima S et al. Surgical navigation by autostereoscopic image overlay of integral videography. IEEE Trans Inf Technol Biomed 2004; 8(2): 114–121.

7 Liao H, Inomata T, Sakuma I et al. 3-D augmented reality for MRI-guided surgery using integral videography autostereoscopic image overlay. IEEE Trans Biomed Eng 2010; 7(6): 1476–1486.

8 Tran HH, Matsumiya K, Masamune K et al. Interactive 3-D navigation system for image-guided surgery. Int J Virtual Real 2009; 8(1): 9–16.

9 Lubbers HT, Obwegeser JA, Matthews F et al. A simple and flexible concept for computer-navigated surgery of the mandible. J Oral Maxillofac Surg 2011; 69(3): 924–930.

10 Bettschart C, Kruse A, Matthews F et al. Point-to-point registration with mandibulomaxillary splint in open and closed jaw position. Evaluation of registration accuracy for computer-aided surgery of the mandible. J Craniomaxillofac Surg 2011; 40(7): 592– 598.

11 Krempien R, Hoppe H, Kahrs L et al. Projector-based augmented reality for intuitive intraoperative guidance in image-guided 3D interstitial brachytherapy. Int J Radiat Oncol Biol Phys 2008; 70(3): 944–952.

12 Marmulla R, Hoppe H, Muhling J et al. An augmented reality system for image-guided surgery. Int J Oral Maxillofac Surg 2005; 34(6): 594–596.

13 Rolland JP, Fuchs H. Optical versus video see-through head-mounted displays in medical visualization. Presence 2000; 9(3): 287–309.

10 Apr
info

Augmented Reality Innovation in Prosthodontics and Smile Design

Received: October 28, 2021; Published: November 26, 2021

Abstract

Prosthetic dentistry is one of the dental branches that has evolved remarkably, taking advantage of the latest digital innovations. Augmented reality (AR) is one of the digital technology advances that superimpose virtual and real objects in the surrounding environment. AR uses displays, input devices, tracking devices, and a computer. In dentistry, AR was initially used in education to provide an immersive experience while learning virtually. In prosthetic rehabilitation with dental implants, AR enabled the visualization of the digital images and preoperative planning data superimposed on the surgical field, which assisted accurate implant positioning and drilling on the correct spatial position. Implant placement accuracy significantly improved, and operation time was significantly reduced. However, specific software applications should be further upgraded to optimize the results. In aesthetic smile design, AR provides the patients with a preview of their makeover during their discussion appointment and saves the dentist time that was consumed by multiple photographs capturing and the mock-ups creation. Mobile applications are being developed to simplify the design procedure, enhance patient integration, and facilitate communication with laboratory partners.

Keywords: Augmented Reality; Prosthodontics; Implantology; Dynamic Navigation; Smile Design

Abbreviations 2D: Two Dimensional; 3D: Three Dimensional; AR: Augmented Reality; CBCT: Cone Beam Computerized Tomography; CAD: Computer-Aided Design; CAM: Computer-Aided Manufacture; MRI: Magnetic Resonance Imaging

Introduction

Prosthetic dentistry is one of the dental branches that has evolved remarkably over the last decades taking advantage of the digital innovations and technological advancements in diagnosis, treatment planning, computer-aided design/computer-aided manufacturing of prosthetic appliances, and delivery of advanced treatment. Augmented reality (AR) is an enhanced version of virtual reality created using digital technology to superimpose virtual and real objects in a single realistic environment on an operator’s view of the real world, hence creating a computer-generated working scenario to enhance the sensory perception by interacting with it [1].

AR technology consists of devices including displays that are either head-mounted, handheld, or spatial displays, input devices, tracking devices, and a computer. Recently, AR systems utilized contact lenses and virtual retina displays to show scanned images directly onto the viewer’s eyes’ retina. While tracking devices involved digital cameras and similar optical sensors, accelerometers, solid-state compasses, global positioning systems [GPS], and wireless sensors [2]. The superimposed virtual objects are usually obtained from 3-dimensional computed tomographic dental scans, MRI, angiography, or other 3-D data [3]. In dentistry, AR was initially used in education in contribution with haptic feedback that introduced the perception of force sensation. It was possible to have an immersive experience while learning in a virtual environment. AR enhanced education outcomes supported patient safety and objectively evaluated students, and gave them direct feedback [4]. The scope of indications of AR has expanded to incorporate radiology, orthodontic bracket positioning, prosthetics augmentation, management of dental phobia, endodontic surgery, and oral and maxillofacial surgery [2].

AR and prosthodontics

In prosthetic rehabilitation of missing, badly destructed, and aesthetically unaccepted teeth, most patients are particularly concerned about the results of the lengthy treatment procedures and their fears driven from their ignorance of the anticipated results that might not meet their expectations. The introduction of AR, which allows the dentist and the patient to inspect a superimposed digital visualization of the treatment outcome, would import patient satisfaction and trust to proceed with the costly treatment process. Thus, AR has the potential to simplify prosthetic treatment to meet patients’ expectations. In addition to facilitating communication of the practitioner with the dental laboratory technician responsible for translating the operator’s plans into realism. This article aims to provide an overview of the application of AR in the dental discipline of prosthodontics.

AR in implant-prosthetic rehabilitation

AR enabled the visualization of digital images and preoperative planning data to assist in accurately positioning of the dental implants and drilling on the correct spatial position. AR is especially significant regarding the oral and maxillofacial region, where the peculiar anatomical complexity of the region has always complicated the surgical position of dental implants [5]. Surgical navigation implicates knowing proper anatomical orientation and the prediction of implant position in bone before starting the incision. AR systems project the patient’s data and pictures as retrieved from computed tomography, MRI, anatomic models, and intraoperative pictures directly on the surgical site. AR has been shown to improve dental implant positioning when a graphically superimposed suggested position is used on the patient during implant placement [3]. AR implant surgical navigation was presented using retinal imaging rather than monitor display to avoid looking away from the oral surgical field during the operation. Furthermore, AR systems were improved to act as an automatic information filter that selectively displays only the surgeons’ most relevant information [1]

In prosthetic rehabilitation with dental implants, the focus of AR technology was to achieve a more visible surgical field during the operation, which was brought using specific glasses and an integrated screen. AR allowed the surgeon to visualize, in real-time, patient parameters, relevant x-rays, 3D reconstruction, or a navigation system screen [6].

Many studies have been done to illustrate the efficiency of AR in dental implant surgical planning. A study done by Lin., et al. used the stereoscopic visualization concept combined with head mounted AR displays, revealed that implant placement accuracy, as measured by the deviation between the planned and the prepared positions of the implants, significantly improved by combined integration of the surgical template and AR technology [7]. Jiang., et al. attempted placing dental implants in edentulous mandibular models using 3D AR-guided implant navigation. The postoperative results showed better accuracy, higher efficiency, and shorter time for the 3D AR navigation than the traditional 2D image navigation method [8]. The accuracy of dynamic implant navigation using AR HoloLens was presented by Pellegrino., et al. The position of the implants was virtually planned. It contributed to a dynamic navigation system in addition to a computer-aided/image-guided procedure. The HoloLens enabled the visualization of 2D/3D data and permitted device-control via voice commands or simple gestures, which helped the practitioner to visualize the system data, information, targets, and positions by placing a virtual desktop near the patient’s face without being forced to look away from the patient’s mouth. The study appraised AR as a valuable tool in reducing operation time and accurate implant positioning, although it recommended that specific software applications be further upgraded to optimize the results [6]. In another study, AR navigation with accurate CBCT-patient registration for dental implant placement demonstrated acceptable implant accuracy, intraoperative time, and resolution of the hand eye coordination problem [9].

AR and aesthetic smile design

In dentistry, smile reconstruction has been achieved using lengthy and detailed methodologies. A pre-visualization was achieved utilizing a conventional laboratory-made wax-up and intraoral mock-up, in the form of a two-dimensional smile design by overlapping idealized teeth forms onto a picture of the patient. Protocols were proposed using only a set of photographs and presentation software to offer a predictive view of the patient’s future smile and to transfer treatment plan to the dental laboratory technician. Nevertheless, these protocols were hindered by the two dimensional presentation and were only partially immersive for the patients [10]. AR provides the patients with a preview of their aesthetic smile makeover at no obligation during their discussion appointment and saves the dentist time consumed by capturing multiple photographs or creating mock-ups. In attempts to improve patient experience and patient-practitioner communication, recent technological evolutions were proposed.

Mobile applications were suggested to ease the process of pre-visualization of the future patient smile by simply looking at the mobile camera; consequently, explaining complex treatment options was easier. Observing a virtual mirror helped the patient to decide whether to invest in the detailed, cost-intensive, and time-consuming planning of the cosmetic treatment or not. The remarkable before-and-after images and the possibility of viewing oneself with the new restorations in a virtual mirror is an enthusing experience for the patients. The app facilitates communication with the laboratory partners [10]. AVRspot [Smart Tek Solutions and Services LLC] proposed a face landmark recognition tool in a mobile app that identifies the patient’s smile in an image and substitutes it on other smiles to determine the best fit.

The app provides the users with tooth size and shape adjusting tools to match their desired smile [11]. Another contribution by Ivoclar Vivadent is the IvoSmile application available since 2019 and is compatible with Apple iPad, iPhone, and iOS 12 or higher. It provides patients with an image of their smile in a few minutes [12]. Touati., et al. examined the user-experience of smile design using facial recognition and two AR strategies. In his study, the IvoSmile app [IvoSmile®/Kapanu, Ivoclar-Vivadent] used the camera inte[1]grated into a tablet to recognize the patient’s face. After determining virtual facial and oral landmarks, a second software proposed an artificial layer of smile suggestions that was superimposed on the patient’s smile.

The patient was given the full opportunity to explore possibilities of his smile reconstruction, and accordingly, AR technology and the mobile app integrated the patient into the decision-making process for reconstruction of the aesthetic zone [10] his process was further uplifted with a new tool called “CAD link”, which directly matched the final AR proposal with a digital impression to create a digital wax-up [13]. Merchand., et al. presented this novel digital workflow combining AR and CAD/CAM technologies in a case report to illustrate the opportunity of AR in daily dental practice. Using the ‘CAD-link’ workflow combined with the AR software and the CAD software, the maxillary anterior reconstructions were planned precisely according to the previously developed design proposal of the AR software approved by the patient. The CAD-link was used to design a wax-up mock, which was fabricated using CAM technology. After the patient approved the mock-up, it was used to prepare a silicone index to guide the minimally invasive planned preparation [14].

Future innovations

AR‑based artificial intelligence contributes novel inputs in prosthodontics. Robotic systems, machine learning, and artificial intelligence can shape the future of dentistry through the ability to deal with and process massive data. Artificial intelligence is a branch of computer science concerned with building intelligent software or machines capable of running different errands that demand human intelligence. Artificial intelligence has been reported promising in maxillofacial surgery, robotic education, tooth preparation for crowns and bridges, testing tooth brushing, root canal treatment, plaque removal, orthodontics and jaw movements, material testing, tooth arrangement for complete dentures, image radiography, and robot assistance. Robotic assistance may also be help support the dental technician [3]. The dental robots are thought to be utilized sooner to manufacture removable partial dental replacement, complete dental replacement, and implant prosthesis. However, the innovation is expensive and requires attention to the techniques’ inherent complexity and hardware.

Conclusion

AR presented novel innovations in dentistry and, prosthetic rehabilitation. The significant advantage of AR in prosthetic rehabilitation is accuracy, saving working time, better communication with the patient and the laboratory technician as it accomplishes the tasks with minimum human fatigue. AR reality showed significant success in dynamic implant navigation. It is a promising technology in smile design that allows pre-visualization of the treatment and active patient engagement in decision making. Nevertheless, still more advancements are required in the quality of image construction, flexibility of the software, and ease of integration in the daily dental office. ore evolution is required for three‐dimensional conception, video analysis, functional movement evaluation, and prosthesis design. The cost of the systems is expensive, and few aspects of understanding and conversions to clinical practice are challenging and require extensive research and development.

Conflict of Interest

The author declares the absence of any financial interest or any conflict of interest.

References

  1. Kwon H-B, Park Y-S, Han J-S. Augmented reality in den[1]tistry: a current perspective. Acta Odontol Scandinivica. 2018;76(7):497-503.
  2. Rana K, Sharma B, Sarkar S, Choudhary SR. When virtuality merges with reality Application of virtual reality and aug[1]mented reality in dentistry – A literature review. SRM J Res Dent Sci. 2021;12:161-167.
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  4. Moussa R, Alghazaly A, Althagafi N, Eshky R, Borzangy S. Effec[1]tiveness of virtual reality and interactive simulators on dental education outcomes: Systematic review. Eur J Dent. 2021.
  5. Farronato M, Maspero C, Lanteri V, et al. Current state of the art in the use of augmented reality in dentistry: A systematic review of the literature. BMC Oral Health. 2019;19(1):135- 150.
  6. Pellegrino G, Mangano C, Mangano R, Ferri A, Taraschi V, Mar[1]chetti C. Augmented reality for dental implantology: A pilot clinical report of two cases. BMC Oral Health. 2019;19(1):1-8.
  7. Lin YK, Yau HT, Wang IC, Zheng C, Chung KH. A novel dental implant guided surgery based on integration of surgical tem[1]plate and augmented reality. Clin Implant Dent Relat Res. 2015;17(3):543-553.
  8. Jiang W, Ma L, Zhang B, et al. Evaluation of the 3D augmented reality-guided intraoperative positioning of dental implants in edentulous mandibular models. Int J Oral Maxillofac Im[1]plants. 2018;33(6):1219-1228.
  9. Ma L, Jiang W, Zhang B, et al. Augmented reality surgical navi[1]gation with accurate CBCT-patient registration for dental im[1]plant placement. Med Biol Eng Comput. 2019;57(1):47-57.
  10. Touati R, Richert R, Millet C, Farges JC, Sailer I, Ducret M. Com[1]parison of two innovative strategies using augmented real[1]ity for communication in aesthetic dentistry: A pilot study. J Healthc Eng. 2019;2019:7019046.
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  14. Marchand L, Touati R, Fehmer V, Ducret M, Sailer I. Latest ad[1]vances in augmented reality technology and its integration into the digital workflow. Int J Comput Dent. 2020;23(4):397- 408

 

02 Apr
info

Image-Based Tracking of the Teeth for Orthodontic Augmented Reality

Conference Paper · October 2012

Abstract. We present image-based methods for tracking teeth in a video image with respect to a CT scan of the jaw, in order to enable a novel light-weight augmented reality (AR) system in orthodontistry. Its purpose is guided bracket placement in orthodontic correction. In this context, our goal is to determine the position of the patient maxilla and mandible in a video image solely based on a CT scan. This is suitable for image guidance through an overlay of the video image with the planned position of brackets in a monocular AR system. Our tracking algorithm addresses the contradicting requirements of robustness, accuracy and performance in two problem-specific formulations. First, we exploit a distance-based modulation of two iso-surfaces from the CT image to approximate the appearance of the gum line. Second, back-projection of previous video frames to an iso-surface is used to account for recently placed brackets. In combination, this novel algorithm allowed us to track several sequences of three patient videos of real procedures, despite difficult lighting conditions. Paired with a systematic evaluation, we were able to show practical feasibility of such a system.

1. Introduction

This paper suggests a novel solution for guidance in orthodontic applications with a light-weight monocular video see-through Augmented Reality (AR) system. It targets the guided placement of brackets onto individual teeth in order to improve efficacy and reduce chair time of bracket placement and re-adjustments for dental braces in orthodontic correction, therefore allowing to incorporate pre-procedure simulation and planning. The state of the art for this procedure relies solely on the experience of the orthodontist for both placement of the brackets and the choice of the wire tension between the brackets. In dentistry, low-dose cone-beam CT reconstructions of the jaw are typically obtained with modern digital volume tomography (DVT) devices, with an acceptable dose limit even for teenagers. Related research [1] has developed simulations based on finite element methods from such CT data of teeth and bone. Those simulations could be used in a pre-procedural planning of the optimal bracket placement and wire tension, such that patient teeth move in an ideal manner while minimizing rotation. While much less accuracy is needed than for example in implant placement, a realization of the pre-procedure plan requires guided placement of the brackets. Augmentation of a patient video showing a superimposition of the newly placed bracket with its planned position would suffice. Potential benefits include higher efficacy due to a reduction in chair time with fewer follow-up visits for corrections, as well as reduced probability of relapse. Therefore, this routine procedure could be improved with a light-weight monocular augmented reality system, while avoiding the cost and complexity of a full-scale medical AR solution.

2. Related Work

One of the central choices which had to be made in realizing this system, is the choice of tracking algorithm [7]. There are several approaches commonly employed for optical tracking, such as marker-based tracking, template-based tracking [2], feature-based tracking [8] and edge-based tracking [5] as well as combinations of these methods. However, due to the nature of our tracking target not all methods can be used. Marker-based tracking is not relevant, because we do not want to augment the scene. When using external tracking systems, a disadvantage besides their high cost is the challenge to keep overall tracking error low, particularly in scenarios such as dental implant placement [12]. This is because the overall system accuracy is limited by the accumulated errors from the tracking system itself, patient registration, hand-eye calibration, synchronization, etc. In order to avoid such an accumulation of errors (as well as additional, expensive equipment) we employ solely image-based tracking methods, which track the patient jaw directly in the video used for the overlay. Template based tracking by itself is too unstable due to illumination variations, occlusions and the need for an initially textured model of the scene, which we don’t have. Feature-based tracking is also not feasible since our scene is mostly textureless and feature-point extractors will not find enough reliable features. This only leaves edge-based tracking methods for use in our system. As can be seen in Fig. 1 edges are a very dominant and a stable feature in the input image. We therefore chose to use edges as our primary tracking modality which is augmented by template-based tracking methods for increased robustness.

3. Methods

In our chosen scenario, a DVT volume of the jaw is always available, since it is the basis of the numerical simulation for planning. Therefore, we investigate methods to automatically align a DVT volume with a video image feed, which relates our problem to medical 2D-3D registration [9] and tracking [11]. For an impression of the scenario see figure Fig. 1. We attempt to use all information available from these two modalities and we present a method consisting of two complementary steps. One step provides a good overall alignment, the other step ensures robust tracking even in light of changing conditions. The underlying 2D-3D registration problem is solved through an iterative optimization of a similarity metric over a 6 DOF pose.

3.1 Dual Iso-Surfaces

In order to compute image similarity, we need a fast method of generating a 2D image from the DVT volume for comparison with the 2D video image. While direct volume rendering is able to create close to photo-realistic images, overly complex methods are too slow for real-time registration. Simpler methods, such as nonpolygonal iso-surfaces can be computed extremely efficiently, since they represent only one intensity threshold in the data set. In the patient videos, the shape of the teeth and the gum line contain the most reliable geometric information. Unfortunately, in the DVT volume the gum line itself is an interface between two intensities, i.e. enamel and gum. It can therefore not be retrieved by single iso-surface rendering. We suggest using a modulation based on normal distances of two iso-surfaces for the visualization of the gum line. Related work in “Focus and Context“ visualization [6] addressed a similar problem for context modulation, where one isosurface is shown transparent when close to a second one.

While the teeth are easily visualized as the highest CT intensities (i.e. XRay attenuation or Hounsfield units), different types of tissue, including the tongue, cheeks, lip and gum all have almost identical attenuation values. Thus, the lip folding over the gum cannot be separated, and therefore the actual gum line cannot be visualized reliably. As an alternative solution, we visualize the interface between enamel and bone or dentin (i.e. the roots of the teeth). This line approximately follows the course of the gum line and we could verify in experiments that this approximation is bias-free with respect to the registration. Please see Fig. 3 (right) for a direct comparison of the dual iso-surface and the textured iso-surface, in particular the course of the gum line.

We efficiently implement this in a single pass of a GPU ray-caster, with a speed close to single iso-surface rendering. As a ray from the camera center into the scene hits the outer surface representing gum (or dentin instead), its direction is changed to the normal of that surface. The ray then is followed for only a few millimeters more, possibly hitting the second surface for enamel. See Fig. 1 for three example points on the outer surface (blue) and their relation to the inner surface for enamel (green) in a cross section. If the enamel surface is not found (case (c) in Fig. 1 (right)), the gum surface is fully opaque. If the enamel surface is right next to the outer surface (Fig. 1 (right, a)), the outer surface is fully transparent. Otherwise, the surfaces are blended based on their distance (Fig. 1 (right, b)).

3.2 Dissimilarity Metric

Once the DVT volume is rendered, we compare it to the video image. We apply an edge-based similarity metric between the video image and the dual iso-surface rendering. This is based on weighting the distance to the closest edge in the video image with the gradient magnitude of the dual iso-surface rendering. Lower results of this metric indicate that the edges are well-aligned. For efficiency, we compute a distance map from the output of a Canny edge filter [3] of the video frame, since the video image stays constant during the pose optimization. The measure then becomes

where d(x, y) is the distance map of the video edges and g(x, y) = ∇(x,y)J2 is the squared image gradient magnitude of the dual iso-surface rendering J at pixel coordinates (x, y). We use an exponent of two, since we put more emphasis on regions with large gradients (i.e. edges), while reducing the weight of areas with only small variations in gradient caused by noise. Fig. 2 shows a plot of the dissimilarity metric against x and y translations parallel to the image plane. Millimeters are measured at the depth of the jaw. Notice a clear minimum at the center of the plot, which represents perfect visual alignment such as seen in Figure 3. Dissimilarity increases more quickly in y-direction, since the dominant occlusion edges of the teeth are in x-direction in the image. We use an elliptical region of interest, defined by two focal points as the projections of the canines.

3.3 Initial Alignment

In order to increase capture range and speed up the process, we propose another step complementing this edge-based approach. Note that there is a variety of established tracking techniques that can be used to achieve such a pre-alignment, some may not even need knowledge of the CT. Since in our scenario the CT is available, we can reproject video pixels into arbitrary views based on the surface shape from the CT and correct alignment on any one video image. 

4. Experiments

For the evaluation of the proposed system, we created a prototype to study practical feasibility. In cooperation with orthodontic partners we acquired data for the real procedure of three teenage patients. The three videos each are about 20 minutes long and show the whole procedure from the perspective of a camera mounted to the orthodontist’s head. In each case DVT image data is available. In the following, we examine both the registration for single frames and the behavior for short video sequences.

4.1 Random Studies

In a scenario where tracking is performed with the goal of a scene overlay, errors in image pixels are more relevant than in transformation parameter space. We therefore choose interest points on the surface of the teeth and compute the average projection errors. While 2D-3D point correspondences at significant edges and corners between the teeth were defined, they generally resulted in poor visual alignment due to the limited accuracy of placing those landmarks (i.e. target localization error TLE of over 5 pixels). Therefore, a quasi ground truth registration was defined based on the optimal visual alignment by the expert. In several random studies, we perturbed this ground truth alignment for all 6 pose parameters. The parameters were chosen, such that the x and y axis are parallel to the image plane and z is facing the camera with the origin at the center of the jaw. In Fig. 4 (left) we present a random study of 500 iterations as a typical representative. Translation was randomized in a range of ±20 mm in x and y direction and ±10 mm in z, while rotation in all three axes was randomized in a range of ±10 degrees, enough to observe a failure of the algorithm in some instances. In the specific view of of the patient, similar to the one shown in Fig. 3 (left), this corresponds to an average pixel offset of 37.2 pixels on the 640 × 480 video image, which is well beyond expected inter-frame motion. After removal of 10% outliers, we were able to recover from an average error of 35.4 pixels to just 2.7 pixels, or an average of 2.1 mm and 4 degrees. In Fig. 4 (left) you can see the results of the random study including outliers, sorted by initial pixel error (red). Observe that the algorithm was successful in each case with offsets of less than 40 pixels, which is marked with a blue line in the plot, with the error after registration (blue) well below the red line. Even beyond that threshold, correct alignment is recovered in about 75% of the cases.

4.2 Image Sequences

We successfully tracked several sequences of all three patient videos. Visual alignment appeared accurate and reliable, especially around the incisors. Despite the dental prop, patients are moving their jaw during the procedure, which forced us to track upper and lower halves of the jaw independently. We believe that this motion can be modeled with few parameters and included in one optimization, ultimately making alignment more stable, especially at the molars. Separation of mandible and maxilla can be performed automatically by fitting a plane.

In order to quantify behavior over a sequence of frames, we created a synthetic sequence using a textured model. While this experiment is simpler than real patient data, it allows us to compare the computed poses to ground truth. We chose a linear in-plane translation of x and y, as well as rotation about these axes and a motion returning to the starting position in 50 frames as a test case. See Fig. 5 (three plots on the left) for plots of the translation components of the resulting poses. Although the in-plane translation was recovered up to about 5 mm, there is an error in the z-translation by as much as 15 mm, which is expected for 2D-3D registration. As the z-axis is facing the viewer, translations in that direction have little effect on the image (and hence also on the final superimposition). The error in target points was 6.7 pixels average over the whole sequence.

5. Conclusion

We presented a tracking solution and novel guidance system for orthodontic correction. We focused on the feasibility of a tracking system based on a CT volume and the patient color video sequence. A multi-step algorithm was devised to use several aspects of the data. The proposed approach includes a dual iso-surface rendering method with distance based modulation to produce fast high-quality images of the gum line, paired with a textured model based pre-alignment and update step. In extensive random studies we could show correct registration of single images; more importantly, several sequences of real procedures were successfully tracked. In conclusion, we enabled a novel application of augmented reality in an orthodontics routine procedure. Future work could focus on a parameterization of jaw movement for concurrent tracking of both halves, as well as better handling of occlusion by the orthodontist’s tool. While this work focused on recursive tracking for high accuracy, detection of the prop or the teeth could complement the current method (e.g. using an advanced approach such as [4]). In the future our prototype has to be integrated with simulation and planning capabilities in order to create a fully practical solution, and a systematic quantitative evaluation of tracking accuracy performed.

Acknowledgements. We would like to thank Dr. V. Rummel, Dortmund, Germany, for his support during data acquisition and his valuable medical feedback.

References

  1. Ammar, H.H., Ngan, P., Crout, R.J., Mucino, V.H., Mukdadi, O.M.: Threedimensional modeling and finite element analysis in treatment planning for orthodontic tooth movement. American Journal of Orthodontics and Dentofacial Orthopedics 139, 59–71 (2011)
  2. Baker, S., Matthews, I.: Lucas-kanade 20 years on: A unifying framework. International Journal of Computer Vision 56(3), 221–255 (2004)
  3. Canny, J.: A computational approach to edge detection. IEEE Transactions on Pattern Analysis and Machine Intelligence 8, 679–698 (1986)
  4. Hinterstoisser, S., Cagniart, C., Ilic, S., Sturm, P., Navab, N., Fua, P., Lepetit, V.: Gradient response maps for real-time detection of texture-less objects. IEEE Transactions on Pattern Analysis and Machine Intelligence (2011)
  5. Klein, G., Murray, D.: Full-3D edge tracking with a particle filter. In: Proc. British Machine Vision Conference (BMVC 2006), vol. 3, pp. 1119–1128. BMVA, Edinburgh (September 2006)
  6. Kr¨uger, J., Schneider, J., Westermann, R.: ClearView: An interactive context preserving hotspot visualization technique. IEEE Transactions on Visualization and Computer Graphics 12(5) (September-October 2006)
  7. Lepetit, V., Fua, P.: Monocular model-based 3D tracking of rigid objects: A survey. In: Foundations and Trends in Computer Graphics and Vision, pp. 1–89 (2005)
  8. Lowe, D.G.: Distinctive image features from scale-invariant keypoints. International Journal of Computer Vision 60, 91–110 (2004)
  9. Markelj, P., Tomazevic, D., Likar, B., Pernus, F.: A review of 3D/2D registration methods for image-guided interventions. Medical Image Analysis (2010)
  10. Matthews, I., Ishikawa, T., Baker, S.: The template update problem. In: Proceedings of the British Machine Vision Conference (September 2003)
  11. Mori, K., Deguchi, D., Sugiyama, J., Suenaga, Y., Toriwaki, J., Maurer Jr., C.R., Takabatake, H., Natori, H.: Tracking of a bronchoscope using epipolar geometry analysis and intensity-based image registration of real and virtual endoscopic images. Medical Image Analysis 6(3), 321–336 (2002)
  12. Wanschitz, F., Birkfellner, W., Figl, M., Patruta, S., Wagner, A., Watzinger, F., Yerit, K., Schicho, K., Hanel, R., Kainberger, F., Imhof, H., Bergmann, H., Ewers, R.: Computer-enhanced stereoscopic vision in a head-mounted display for oral implant surgery. Clinical Oral Implants Research 13, 610–616 (2002)
14 Mar
info

Augmented reality for dental implantology: a pilot clinical report of two cases

© The Author(s). 2019 Open Access  This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Abstract

Background: Despite the limited number of articles dedicated to its use, augmented reality (AR) is an emerging technology that has shown to have increasing applications in multiple different medical sectors. These include, but are not limited to, the Maxillo-facial and Dentistry disciplines of medicine. In these medical specialties, the focus of AR technology is to achieve a more visible surgical field during an operation. Currently, this goal is brought about by an accurate display of either static or dynamic diagnostic images via the use of a visor or specific glasses. The objective of this study is to evaluate the feasibility of using a virtual display for dynamic navigation via AR. The secondary outcome is to evaluate if the use of this technology could affect the accuracy of dynamic navigation.

Case presentation: Two patients, both needing implant rehabilitation in the upper premolar area, were treated with flapless surgery. Prior to the procedure itself, the position of the implant was virtually planned and placed for each of the patients using their previous scans. This placement preparation contributed to a dynamic navigation system that was displayed on AR glasses. This, in turn, allowed for the use of a computer-aided/image-guided procedure to occur. Dedicated software for surface superimposition was then used to match the planned position of the implant and the real one obtained from the postoperative scan. Accuracies, using this procedure were evaluated by way of measuring the deviation between real and planned positions of the implants. For both surgeries it was possible to proceed using the AR technology as planned. The deviations for the first implant were 0.53 mm at the entry point and 0.50 mm at the apical point and for the second implant were 0.46 mm at the entry point and 0.48 mm at the apical point. The angular deviations were respectively 3.05° and 2.19°.

Conclusions: From the results of this pilot study, it seems that AR can be useful in dental implantology for displaying dynamic navigation systems. While this technology did not seem to noticeably affect the accuracy of the procedure, specific software applications should further optimize the results.

Keywords: Computer-assisted surgery, Image-guided surgery, Implantology, Navigation system, Real-time tracking, Implant placement accuracy.

Background

Computer-assisted procedures are becoming more and more integrated into different fields of dentistry [1]. This is particularly evident in the increasing use of processes such as 3D printing and CAD-CAM methods in the manufacturing of dental implantology. This has not only allowed for a more accurate and diverse manufacturing capability but also dramatically expands on the production surgical templates often made in-house. Currently, the examination of static guided surgery as a means of creating surgical templates to accurately position implants is ample. The conclusion drawn from this research is that should the implant be inserted with a margin of error of approximately 1 mm, the implant rehabilitation process will be mostly successful [2]. However, the working time for planning and producing the surgical template do not encourage or justify an ordinary use of this method [3]. Another method for computerassisted surgery in dental implantology is image-guided surgery through dynamic navigation. Such surgical tech- niques are already largely used in major Neurosurgery, Maxillo-facial surgery, ORL, and Orthopedic surgeries and is quickly becoming popular in Implantology. Some papers published in past years report on the comparable accuracy between dynamic and static surgical navigation [4–6]. It was shown that dynamic navigation could overcome some of the disadvantages associated with static guided surgery. These included reducing costs and time needed for the impression and laboratory procedures of a static guided system. Another advantage of a dynamic guided system could be the ability to have a direct view of the surgical field as well as the possibility to use standard drills which is optimal in a case of mouth opening reduction [7]. In addition to this, dynamic navigation allows for changes in implant planning to be made at the time of surgery. This level of flexibility is not offered by statically derived surgical guides as they are fixed and cannot be altered once they are planned and manufactured. Also, tight single-tooth edentulous ridge areas can be fully guided using dynamic guidance as a dynamic guide is not restricted by drill tube size (i.e. in the anterior mandibular incisor sites). Furthermore, implant size is not limited with dynamically guided systems, as they are with static guides and CBCT, planning and surgery can be achieved in a single day [1, 8, 9].

However, a possibly problematic disadvantage of a dynamic guided system is the need to simultaneously pay attention to the patient as well as the output from the navigation system display. This unfavourable feature is exacerbated in systems where the tracking device is positioned on the same mobile carriage as the navigation system display. This could cause difficulties in following the virtual procedure while also keeping sight of the surgical site itself [10]. Systems that use a mobile screen fixed near the patient’s head on the dental chair may address this issue as they limit the movement of the surgeon’s head and, therefore, their loss of sight of the surgical site [11].

The use of AR through specific glasses and an integrated screen is a fairly new trend in the field of medicine. This technology can allow the surgeon to visualize, in real-time, patient parameters, relevant xrays, 3D reconstruction or a navigation system screen [12, 13]. This last item could significantly increase the use of dynamic navigation a process that has already been readily adopted in other major surgical disciplines. The use of these devices is currently under validation and only few publications are present in literature to date and even fewer papers investigate this technology in dentistry [10, 14]. The aim of our pilot study is to evaluate the feasibility of adopting AR as a means of facilitating the use of dynamic navigation for dental implantology. The secondary objective was to evaluate if the accuracy obtained with this innovative display device was maintained in the range already described in literature regarding dynamic navigation.

Case presentation

Two patients were referred to the Oral and Maxillo-facial Unit of the Department of Biomedical and Neuromotor Sciences for implant supported prosthetic rehabilitation. Both patients were to be treated in the upper premolar area and were in good general health conditions and had no contra-indications to the implant surgery. The clinical procedures were carried out in accordance with national guidelines as well as with the Declaration of Helsinki.

Navigation system setting

After the filling of the appropriate consent documentation, both patients undertook a CBCT scan with the markers plate from the navigation system. These markers were positioned in situ as per protocol of using the navigation system ImplaNav (BresMedical, Sydney, Australia) which requires that the markers plate is fixed with a hard impression material (Ramitec, 3 M Espe, USA). After the scan, the markers plate was removed and replaced in the same position on the day of the surgery. The CBCT data was analyzed through the navigation system planning software and the position of two implants were virtually planned. At the time of the surgery the patient reference tool for the navigation system was fixed on the same support of the markers plate. Another reference tool was positioned and rigidly fixed on the implant drill handle. Then the calibration tool was connected to the handle and the drill axis was identified by the navigation system. The first lance drill was successively used to touch the fiducial markers on the markers plate to verify the patient position. After the calibration procedures, the navigation system was directly interfaced with the virtual reality glasses (Hololens, Microsoft, USA) through a wifi connection using a dedicated software created by Fifthingenium (Milan, Italy) (Fig. 1).

Augmented reality glasses setting

Microsoft Hololens is an augmented reality headset which can be used to expand the limits of interaction between the virtual and the physical world. Hololens runs a custom Windows 10 version as its operating system. It also features Bluetooth and Wi-Fi connectivity and is powered by a Holographic Processing Unit HPU 1.0, 2GB RAM and 64GB of Solid State storage.It is also equipped with an Inertial Measurement Unit, four environment understanding cameras, mixed reality capture, four microphones, an ambient light sensor and two HD displays capable of automatic pupillary distance calibration.

The plethora of applications of the Hololens in industry is mainly attributed to its ability to create, manipulate and display holograms or virtual objects in the field of the user. Combined with the ability to recognize objects, rooms and environments through the use of AI and markers, the capabilities of the Hololens allows it to be useful in many industries including the Healthcare and Dental sector.

An application to use Hololens in the dental field was developed in order to visualize 2D/3D data (CBCTs, face scans, oral scans) while at the dental chair without forcing the practitioner to look at a specific monitor/computer. By controlling the device via only voice commands or simple gestures, the surgeon is able to maintain visual of the physical surgical site and avoiding contamination.

A system capable of mirroring the desktop of a computer on the Hololens was developed and coupled with the navigation system used for the surgery. Such system allows the doctor to avoid looking at the computer screen to receive guidance for the surgery. Instead, the doctor can visualize the system data, info, targets and positions by placing a virtual desktop near the patient’s face without being forced to look away from the patient’s mouth.

Clinical procedure

Using the Hololens glasses, the surgeon can contemporarily visualize the surgical field (Fig. 2) and the output of the navigation system screen. The virtual position and the trajectory of the drill into the bone, the implant planned position and the bone anatomy around the implant site were checked in real-time during the whole surgical procedure (Fig. 3). The navigation system software input can also be managed with Hololens through hand movements. Two implants were placed, one for each patient following the drill sequences provided by the implant company protocol. In one case a 3.8 × 9 mm (TTi, WinSix, Ancona, Italy) was positioned. In the other case a 4.1 × 11 mm (BL, Straumann, Switzerland). In both cases, a flapless surgery was carried out (Fig. 4). A postoperative radiograph was taken to evaluate the correct positioning of the implants (Fig. 5a, b). The healing abutments were fixed without any suture.

In one case the implant position had been planned to be close to the maxillary sinus (Fig. 6) and postoperative CBCT was taken to verify if the goal had been reached (Fig. 7). After about 3 months, the contra-torque test was manually performed to verify the osseointegration status of the implants. Then through a scan of the abutment and the use of the intra-oral scanner, the implant position was digitally recorded concurrently with the bordering teeth. The virtual planned position of the implant and the adjacent teeth were exported from the planning module in the ImplaNav software. The two surfaces comprehending the teeth and the implants were compared via an N-point surface alignment of the teeth using Materialise 3-Matic (Materialise, Leuven, Belgium) (Fig. 8). The deviation between the planned implant position and the real one obtained by the scan were evaluated (Fig. 9). Both patients were rehabilitated with screw-retained crowns (Fig. 10).

Results

In both cases it was possible to proceed with the navigation-aided implant placement with the Augmented Reality (AR) displaying in real-time a combination of surgical planning, real anatomy and the output from the navigation system (Fig. 3). The deviation between the planned and the real position of the implants resulted 0.53 mm at the entry point and 0.50 mm at the apical point for the first implant and 0.46 mm at the entry point and 0.48 mm at the apical point for the second one. The angular deviations were respectively 3.05° and 2.19° and the depth deviations were 0.26 mm and 0.37 mm.

Discussion

Dynamic navigation is one of the two computer-guided surgery techniques used in implantology. Many authors reported relatively good results in terms of implant placement accuracy using different navigation systems [1, 15–17]. Block et al. [16] reported on the implant placement accuracy obtained by 3 surgeons using dynamic navigation to treat 100 partially edentulous patients. They reported a mean error of 0.87 ± 0.42mm at the entry point, 1.56 ± 0.69mm at the apex and 3.62° ±2.73° for angle deviations using dynamic navigation. Non-dynamically guided entry point deviations, apex deviations and angle discrepancies had corresponding mean values of 1.15 ± 0.59 mm, 2.51 ± 0.86mm and 7.69° ± 4.92°. Stefanelli et al. [17], in a retrospective study on 231 implants reported an error of 0.71 ± 0.40mm at coronal point, 1 ± 0.49mm at apex and a mean angular error of 2.26 ± 1.62°. Although there are reported advantages using dynamic navigation, this method requires the surgeon to coordinate his view of the screen with the movements of his hands. The look out of the implant site with the rotation of the head for looking at the navigation system screen could represent a risk in case of accidental surgical instrument shifting or unexpected patient movement, especially in advanced implantology. The use of the augmented reality can overcome this drawback and also reduce operating time [10].

The categories of AR-guided surgery are grouped as follows: type I, involving the use of glasses or head-sets [12, 13]; type II, with digital data being projected on a half-silvered mirror [18]; type III, where the images are shown directly onto the patients; type IV, with the use of an external monitor [11]. In this study glasses have been used, allowing the contemporary projection of the patient’s anatomy and the virtual instruments near the surgical field. However, when a 3D virtual layer is displayed and laid over the real environment, there is often a discrepancy between the real image and the virtual image due to an overlay or positional error. Augmented reality is employed in neurosurgery, laparoscopic digestive, laparoscopic thoracic, vascular, urological and gynecological laparoscopic and cardiac surgery. As per its application in maxillofacial surgery, most of the publications refer to its use in orthognathic surgery [13, 19, 20],

traumatic surgery and reconstructive surgery [21–23]. In dentistry, AR is applied in orthodontics for guided bracket placement [24]. In endodontics it is applied to detect root canals and for educational and training purposes [25–27]. In implantology, few studies regarding the use of dynamic navigation, especially in vitro, have been published. Ewers et al. [14] reported a significant medical benefit for the patients when navigation and AR are used for implant placement. In an in-vitro study, Jiang et al. [10] demonstrated a smaller error in incisive and canine regions implant placement using AR associated with dynamic navigation as opposed to the use of 2D navigation methods. The surgery time was significantly shorter by using a combination of the two technologies. In the present study, a dynamic navigation system associated with the augmented reality was deployed. This technique allowed the surgeon to simultaneously having a view of the surgical field as well as the navigation system monitor displaying implant planning and virtual burs. By wearing glasses where the virtual image is projected near the surgical field, the surgeon could see the implant site without interference and without the risk of overlay errors. The main limit of this technology, currently, is emanated by the sometimes inconvenient virtual window positioning and orientation together with the working distance of the glasses which could force the surgeon to operate in an uncomfortable position. Nevertheless, the cases reported were simple and these limitations did not affect the results. Despite this, a comfortable work position might become mandatory in advanced clinical cases [28, 29] in which this technology would prove to be beneficial. Other disadvantages could be considered the cost of the device, the time spent to set-up and the need to manage additional software for the AR. Possible setbacks could also occur from the device wireless connection and the battery charge although there were not reported in the present study. These problems could be solved by developing a dedicated software application for implantology and by upgrading the associated hardware. As per the application in maxillofacial surgery of an AR technique displaying 3D images without the use of glasses, Suenaga et al. [30] reported a positional error of 0.77 ± 0,19mm (range 0,45-1,34) and an angular error of 2°. Zhu et al. [12], however, reported a discrepancy of 0.96 ± 0,51mm (range 0,55–2 mm). Most of the maximum overlay errors reported in literature are lower than 3mm [11] with an exception for the research performed by Lin et al. [31], who reported a maximum error of 6.56 mm. The increase of accuracy, in addition to the lack of depth perception, is a problem the authors of these studies are working to address [32]. An in-vitro study by Lin et al. [31] showed good results in terms of implant placement accuracy using the drill-guides technique combined to AR. Katić et al. [33], by using an AR system in a pig cadaver experiment, reported a deviation of 1.1mm and 2° between the planned implant and the positioned one. In the present case report, a less than 1mm accuracy was achieved, comparable with the one reported in literature by only using the navigation system [1, 34]. This seems to indicate that AR does not affect the accuracy of the navigation procedure. A touch-less interface for the navigation system software could also promote the use of this technology in the surgical theatre. By simplifying the procedures and reducing operative time, AR can proved to be an exceptional resource in dental implantology. This kind of technology could increase the use of dynamic navigation as it solves the problem of monitoring the screen and the patient simultaneously. The further development of AR could allow matching of the virtual with the real anatomy of the patient, a concept that is already under investigation for major surgery. At the moment, this is made difficult due to the need to follow the patient movement during the intervention usually carried out under local anesthesia.

Conclusions

AR resulted to be quite useful in displaying dynamic navigation despite some software and hardware limits. The presence of the two environments in the AR does not seems to affect the accuracy of the surgical procedure. Specific software applications for navigation systems can further contribute to optimizing the results. Additional in vitro and clinical trials are required to validate the use of this new promising technology for dental implantology.

Abbreviations

AI: Artificial Intelligence; AR: Augmented Reality; CBCT: Cone-beam computerized tomography; mm: Millimeters

Acknowledgements

We thank BresMedical (Sydney, Australia) for the collaboration, Fifthingenium (Milan, Italy) for providing Hololens glasses and the Dental Radiology Division (Prof. Paolo Pisi), University of Bologna, Italy for assisting with the tomographic scanning facilities.

Authors’ contributions

GP was the surgeon, conceived the ideas and wrote the manuscript; CM (author 2) conceived the ideas, RM managed the augmented reality glasses procedures, AF was the accuracy outcome assessor and wrote the manuscript, VT gave the support for the navigation system, CM (author 6) supervised the protocol. All Authors read and approved the manuscript.

Funding 

No funding was obtained for this study.

Availability of data and materials

All data generated or analyzed during this study are included in this published article.

Ethics approval and consent to participate 

This pilot case report was performed in accordance with the Declaration of Helsinki. The present study was carried out following standard clinical procedures and the Authors confirm that this complies with national guidelines. (reference: http://www.salute.gov.it/imgs/C_17_pubblicazioni_2128_allegato.pdf) Every patient gave his consent to the treatment.

Consent for publication 

The identifying images and other personal or clinical details of participants are presented without compromise anonymity. The patients signed the consent form for publication.

Competing interests

The authors declare that they have no competing interests. The Author RM and VT, which have a relationship with the Companies providing the devices, gave only technical support in the device use.

Author details

1Oral and Maxillofacial Surgery Unit, DIBINEM, University of Bologna, 125, Via San Vitale 59, 40125 Bologna, Italy. 2Digital Dentistry Section, University San Raffaele, Milan, Italy. 3Fifthingenium, Milan, Italy. 4University of Technology Sydney, School of Life Sciences, Sydney, Australia. 5Chief of Oral and Maxillofacial Surgery Unit, DIBINEM, University of Bologna, Bologna, Italy.

Received: 18 April 2019 Accepted: 11 July 2019

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05 Mar
info

Augmented, Virtual and Mixed Reality in Dentistry: A Narrative Review on the Existing Platforms and Future Challenges

Article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/4.0/).

Copyright: © 2022 by the authors Licensee MDPI, Basel, Switzerland. This Appl. Sci. 2022, 12, 877. https://doi.org/10.3390/app12020877

Abstract

The recent advancements in digital technologies have led to exponential progress in dentistry. This narrative review aims to summarize the applications of Augmented Reality, Virtual Reality and Mixed Reality in dentistry and describes future challenges in digitalization, such as Artificial Intelligence and Robotics. Augmented Reality, Virtual Reality and Mixed Reality represent effective tools in the educational technology, as they can enhance students’ learning and clinical training. Augmented Reality and Virtual Reality and can also be useful aids during clinical practice. Augmented Reality can be used to add digital data to real life clinical data. Clinicians can apply Virtual Reality for a digital wax-up that provides a pre-visualization of the final post treatment result. In addition, both these technologies may also be employed to eradicate dental phobia in patients and further enhance patient’s education. Similarly, they can be used to enhance communication between the dentist, patient, and technician. Artificial Intelligence and Robotics can also improve clinical practice. Artificial Intelligence is currently developed to improve dental diagnosis and provide more precise prognoses of dental diseases, whereas Robotics may be used to assist in daily practice.

Keywords: augmented reality; virtual reality; mixed reality; artificial intelligence; robotics; dentistry.

1.Introduction

Currently, dentistry is benefiting from the development of modern digital transformation. Three-dimensional (3D) digital technology as well as computer-aided design and computer-aided manufacturing represent modern-day dentistry [1]. Nevertheless, innovations have been introduced in the dental field to improve dental education and clinical activity. Augmented Reality (AR) and Virtual Reality (VR) represent some of these innovations (Figure 1) and are part of the reality–virtuality continuum [2]. Commonly, traditional digital technologies in dentistry are structured into a three-step procedure which can be summarized as follows: (1) the digital image is acquired by a scanning device; (2) the operator can modify or change different dental aspect digitally, such as position or orientation of teeth; (3) the new information is transferred back to solid state or remain digital as a wax-up. With the introduction of AR and VR, these steps are simplified and implemented [3,4]. Although AR and VR possess many common aspects, the outcomes and the users’ experience are completely different. AR and VR systems require essential functionalities such as real and virtual data sources, tracking, registration techniques, visualization processing, perception locations, display types, and feedback mechanisms [5]. Instead of VR, AR generates an interaction between the real environment and virtual objects with the aim to combine virtual and real objects in a single real environment, to run interactively, and to register virtual and real objects reciprocally [6].

Monitor-based interfaces, monocular systems, head-mounted displays and other combined technologies are the instruments commonly used in AR systems. AR is mainly devoted to clinical practice in the medical field and improves the clinical procedure because it can allow clinical information to be visualized directly on the patient, overlapping the digital information and the real world [7]. In dentistry, the principal application of AR is related to overlapping digital information on the real world, basically “improving the reality” and live communication systems between patients and collaborators through the sharing of images, videos, and 3D models.

Conversely, VR uses customized and advanced software and hardware to create a digital 3D reality in which all user’s senses are stimulated with computer-generated sensations and feedbacks. VR, therefore, allows participants to experience simulated digital realities similar to those of physical reality, thus creating scenarios that are impossible to experience in the real world [8]. VR differs from AR in three basic systems: scene generator, a display device, and tracking and sensing. In VR, the display and scene generator is employed to simulate the real world; thus, the resolution of the monitor becomes vital for real-time interaction with the virtual world, allowing the user to be immersed in a digitalbuilt reality [9]. Moreover, the user can use a specific device to interact with the virtual reality as a joystick and complex haptic systems (force feedback). VR applications are already in use in the dental field and mainly concern dental training: they allow students to simulate procedures in a virtual mouth, providing direct and immediate feedback.

In addition to AR and VR, Mixed Reality (MR) represents an innovative tool for use in dentistry. Despite MR being often confused with AR, it is a combination of AR and VR. In MR, users can interact with both virtual and real objects in real-time, while simultaneously, these objects can interact with each other. This “environment awareness” implies that not only do virtual objects act in the real environment, but real objects can also modify the virtual elements, regardless of where the experience is taking place [2]. For instance, in pure MR, users would not be able to see a virtual instrument inside a drawer, unless they open it to look inside; in AR, the instrument would be overlaid, and it would be unnecessary to open the drawer. Innovations such as AI and Robotics are being introduced in the dental field. Whilst AR, VR and MR enhance and create new realities, AI and Robotics perform and replicate human tasks. Artificial Intelligence (AI) revolves around its own intelligence, concerned in algorithm, to solve problems based on learning a specific set of data. Robotics focuses on the reproducibility of different clinical procedures. The use of these new systems could improve the way to perform the clinical training at dental schools and improve clinical practice, increasing the possibility of achieving better reproducible results in less time. At the best of authors’ knowledge, there is no literature review that summarizes these novelties and their potential dental applications. For this reason, we decided to perform this narrative review aimed to recapitulate and provide an update about the actual uses and the possible applications of these new technologies in dentistry.

2. Materials and Methods

In agreement with the Scale for the Assessment of Narrative Review Articles [10,11], we conducted a keyword search-based literature for studies with abstracts or titles containing terms such as “Virtual Reality”, “Augmented Reality”, “Mixed Reality”, “Artificial Intelligence”, “Robotics”. An electronic literature search was performed in PubMed, Scopus and Web of Science considering the articles published from January 2016 to August 2021. We limited this review to the dental field only and included English language-based international peer-reviewed articles (e.g., primary research, reviews, commentaries), online reports, electronic books, and press releases. We also applied a snowballing search methodology using the references cited in the articles identified in the literature search. The publications earlier than 2016 were cited when they were essential for advancing the discussion. The full-text articles of all potential studies were evaluated according to the predetermined inclusion and exclusion criteria listed in Table 1. Moreover, each identified item was assessed for relevance by a member of the study team. Figure 2 illustrates a flowchart of the search process. This narrative review presents an overview of the recent literature on the potential use of VR, AR, MR, AI and Robotics in the dental field.

3. Results

During the retrieval of the scientific literature on the potential uses of VR, AR, MR, AI and Robotics in the dental field, we found research from multiple disciplines, such as dental education, restorative dentistry, endodontics, dental surgery, preventive dentistry and dental phobia. This narrative review investigated not only the application of these devices, but also the efficacy on their use, comparing them with similar devices or traditional tools used during standard protocols.The findings presented below represent a summary of recent examined studies.

3.1. Applications in Teaching Dental Morphology

The study of anatomy is commonly performed by using static two-dimensional (2D) images such as lecture slides, textbooks and flashcards [12]. Since anatomical structures are in three-dimensions (3D), the comprehension of spatial relationships using such static 2D images may be difficult.

Through 3D virtual models, different anatomical structures may be visualized, making the learning experience more immersive than the traditional 2D and 3D methods [13]. The exploration of a virtual environment may help to develop spatial knowledge, reducing the gap between students who struggle to visualize spatial structures and those confident in their spatial ability [14]. In addition, Küçük et al. highlighted that dental students appear more interested in learning anatomical structures through a 3D model than through traditional 2D methods [15].

AR and VR may also be used to learn dental morphology and tooth features such as exterior shape, position, size and internal structure. Basing on software programs with interactive data set, the tooth can be selected, moved and visualized from different directions and angulations. Moreover, specific tooth structures can be made transparent such that the users can see beyond them or even navigate through the root canal. Reymus et al. tested the use of VR in teaching root canal anatomy and found that VR appears to be a valuable instrument suitable for training a student [16]. Thus, both VR and AR may be considered valuable platforms for teaching anatomy and promoting benefits such as increased learner immersion, even if there are no statistically significant differences regarding the amount of knowledge acquired by VR/AR and the traditional method [16].

3.2. Applications in Pre-Clinical Education

A significant proportion of dental education is dedicated to teaching clinical psychomotor skills, and often, the dentist trains directly on the patient [17]. Currently, dental schools use realistic patient simulators with dental models incorporated to simulate a dental treatment [18]. These simulators allow the instructors to demonstrate techniques aimed at improving the hand-eye coordination and manual dexterity of students. Moreover, during the activities on the simulators, dental students require constant tutor feedback on their work for understanding better the procedures before moving on to the subsequent procedures.

During the COVID-19 pandemic, limitations in pre-clinical education have been highlighted, as many dental students could not be trained at their university and lacked the direct support of the tutor. In this COVID-19 era, the most important issue for pre-clinical and clinical education is achieving the balance between the training of dental students and limiting the spread of infected cases [19,20]. It is for this reason, because of the development of innovative instruments to train and teach the basic clinical procedures to the dental students, that replicating dental reality as much as possible became of paramount importance.

Considering these aspects, AR, VR and MR represent innovative educational tools which allow self-education of the student. While the description of the tactile sensation of clinical procedures by the tutor may be difficult to explain using the traditional simulator, the presence of direct feedback and pressure sensors may be useful to overcome this problem by using VR or MR [21]. In a previous study by Eve et al., the performance on a simulated caries removal of undergraduate dental students was compared to prosthodontics residents using a novel haptic VR simulator [22]. Their results showed that efficiency, defined as percentage of carious lesion removed over drilling time, improved significantly over the experiment for both novice and experienced operators [22]. In addition, De Boer et al. examined the use of VR in dental education and highlighted a significant positive effect on the student performance and the appreciation of the 3D environment compared to 2D [23]. Similar to traditional simulators, VR or MR simulators provide digital teeth models, digital handpieces equipped with an air and water in-and-out system and different types of digital burs. In addition, these simulators may provide instant feedback for the students making full use of the lab training time and improving students’ manual dexterity skills before confidently moving onto clinical setting with patients. Table 2 summarizes and compares different dental simulators currently used [21].

3.3. Applications in Clinical Practice

The medical applications of AR are currently concentrated on different surgery types, including neurosurgery, laparoscopic surgery, and plastic surgery. In dentistry, AR is primary used in oral and maxillofacial surgery, dental implant placement and orthognathic surgery [24]. The development of AR devices allows the user to combine the medical information, medical data, and images to the reality. In contrast to conventional image-guided surgery, where a surgeon often looks away from the operative field to view the informative data, AR guidance systems provide real-time intraoperative information directly on the surgical fields and this may decrease the surgical risk [25].

In dental implant placement, AR has been shown to substantially improve a wide range of procedures. A dental implant positioning system with a graphically superimposed suggested position on the patient was introduced as early as 1995. The AR surgical navigation systems for implant placement were introduced using retinal imaging display such that the surgeon maintains the view of the operative field without looking away [26]. During implant placement, AR can act as automatic information filters that selectively display only the most relevant information to surgeons, thereby helping them concentrate fully on the implant placement thereby reducing time and additional costs [27].

Orthognathic surgery is one of the most widely used fields of AR applications in dentistry. The most important advantage of AR-based navigation systems for orthognathic surgery is the possibility to provide overlaid images of real surgical views and virtual surgical plans for guidance. The systems overlay these models onto real-time streaming video images to provide surgeons with preoperative planning and anatomical information. Different AR-based systems were introduced for the simulation of the reduction of mandibular angle and the simulation of the mandibular reconstructive surgery [28–30]. Innovative systems were also developed to simulate mandibulectomy and fibular transplant to the mandibular defect site using 3D patient mesh models. In addition, it allowed surgeons to test and find configurations of vessels and skin paddles[31]. Kim et al. used an AR-system to display overlaid images to allow surgeons to follow virtual surgical planswhen repositioning patient bones after maxillofacial osteotomies [32].

Even VR was applied in orthognathic surgery in order to train different procedures of orthognathic maxillofacial surgery. To better simulate the surgical procedures the VR system can include and replicate different functions such as bone sawing, drilling, and place fixation with haptic force feedback [28,33]. Moreover, in another VR-based simulation platform, the surgeon can interact with the virtual world naturally using his or her hands by means of a tracked hand-held controller [34].

3.4. Applications in Dental Phobia

It is estimated that 50–60% of individuals suffer from a specific fear of dental procedures and dental-related stimuli, or from a mild to severe grade of dental anxiety [35,36]. Fear-related behaviours are considered the most difficult aspect of dental patient management and may interfere with good dental care since the patient with dental phobia (named “odonto-phobia”) goes to the dentist when the clinical situation is severe. The therapeutic techniques, considered most effective in the treatment of phobias and fears, are the In Vivo Exposure Therapy (IVET) and the Virtual Reality Exposure Therapy (VRET). IVET is a technique based on direct patient confrontation with an object or series of anxious situations to reduce the consequent anxious reaction. This exposure therapy is considered the gold standard therapy in the treatment of specific fears related to the dental care situation [37]. Recently, VRET has become a viable alternative to IVET in the treatment of specific phobias [38]. Using computer-generated VR environments, the patient is gradually exposed to situations which are potentially sources of anxiety [39]. Compared to IVET, VRET is safer because the patients face the virtual representation of their threat more gradually in a controlled manner [40]. VRET is known to elicit a feeling of being “present” in the virtual environment, and this represents the main factor for the effectiveness of VRET [41]. Clinically, techniques such as cognitive–behavioural treatments, nitrous oxide, and intravenous sedatives administered during dental treatments have been found to minimize patient pain and discomfort during dental care [42,43]. In addition to these invasive methods, distracting patients with a movie has been shown to help reduce pain in some medical procedures and during laboratory studies of pain [44]. Following the same concept, VR can serve as an effective non-pharmacologic analgesic for dental pain [45]. Several studies reported that VR reduced their awareness of dental pain and that they were so absorbed in

the VR that they did not think often about their pain [46–48]. The patient’s inability to see the dental practitioner and instruments may be one advantage of VR. The effectiveness of VR distraction treatment may depend on how patients feel in the virtual environment [49]. For this reason, video stimulation and audio simulation may be detrimental in making the users’ experience more immersive and by trying to decrease the dental pain [8]. For VR application, it is advisable to produce sound in three dimensions, specifically in the binaural format.

The audio in three dimensions allows the users to hear the sound of objects according to their position in the virtual space. The use of the binaural format, which reproduces the immersive audio with simple headphones, without the aid of a complex hardware set up, will create a greater reality of the VR environment [8]. Consequently, the effectiveness of VR in distracting the patient from medical treatment will be greater. Hendrix et al. confirmed that 3D sound increases people’s sense of immersion in virtual reality [50]. The study showed that people felt more immersed in virtual realities with spatial sound than in virtual realities with non-spatial sound [50,51]. Moreover, the soundtrack in an immersive audio, more than the stereo format, increases the possibility of modifying the patient’s state of mind. Therefore, an adequate sonorization of the VR environment will favour a state of calm and relaxation.

3.5. Applications in Patient Education

Educational and motivational methods play an important role in informing individuals about their oral health status, including oral pathologies that affect oral tissues, thus helping to enhance their compliance with oral care at home. In particular, oral health education is effective in improving patient’s attitude and practice of oral hygiene, providing useful devices and techniques for dental plaque control, which may promote gingival health and decrease caries occurrence [52,53].

AR and VR can be considered important tools to educate old and young patients. The expected outcome in using VR and AR for oral home care is to provide a digital instrument to improve oral hygiene practice in children and adults, motivating the prevention of oral diseases and making educational practices attractive. Moreover, by using games or educational interfaces, VR and AR may become important accessories in the process of teaching and learning. Although few articles reported the application of VR in patient education, it seems to be an engaging learning tool, and patients who participated in the studies perceived it to be beneficial in understanding their health status [54,55]. Mainly in children, the advantage in using a game consists on: whenever the player executes the brushing technique incorrectly, the system provides a visual response which allows the patient to correct the brushing technique. However, further efforts to investigate the role of VR in education and oral health care should be explored in the future.

3.6. Dentist–Patient Communication Tools

Clinicians use several tools to collect different data in order to formulate the correct functional and aesthetic treatment plan such as [56]: physical examination, radiographs, study models, intraoral and extraoral photographs. Once the diagnosis has been made, the patient must be informed of the chosen therapeutic modalities, based on his clinical situation and on evaluating psychological and socio-economic aspects. Nevertheless, many patients may not have the necessary knowledge to understand the concepts illustrated for the treatment plan and the condition of their oral cavity; thus, it may be difficult for the dentist to persuade the patient to accept the proposed therapeutic option.

In this light, digital dentistry has led to the development of many innovative technologies that can aid the dentist in communicating with the patient; for example, the spread of digital technology has simplified the step of creating a set of facial and intraoral photographs, both in the production phase of the images and in their archiving. In addition to communication purposes, this allows the dentist to analyse the patient even after the actual visit, exchanging information with the dental laboratory and with colleagues who may participate in the execution of the therapies [57].

Currently, different devices can be used to improve such patient–operator communication, as diagnostic and virtual wax-up allow for the visualization of the possible prosthetic treatment. Predicting outcomes of the therapy offers many advantages in terms of communication, design and economics. Providing an image in which the result is represented may improve the relationship of trust with the patient and simplify the transmission of the necessary data to the dental technician.

3.7. Artificial Intelligence and Robotics

In addition to AR and VR, new technologies, such as AI and Robotics, have been applied in dentistry to improve the clinical practice [58]. AI is the ability of a machine to perform human tasks and revolves around its own intelligence to solve problems based on the learning of a specific set of data. AI refers to any machine or technology that can mimic human cognitive skills such as problem solving. The foundation of AI is to increase the ability of machines or its intelligence components to perform tasks with speed, low resources, accuracy, and precision. Machine learning is part of AI, which depends on algorithms to predict outcomes based on a dataset [59]. Algorithms are artificial neural networks, highly interconnected networks of computer processors inspired by biological nervous systems that function similarly to the human brain [60].

The most active areas of medical AI are diagnostics and prediction of prognoses. AI in the medical sector contributes significantly to helping decision making related to medical practice, while presenting a considerable level of potential for sound diagnosis and prediction [61,62]. It was proven that machine learning, based on data derived from the decisions of dental professionals, achieved significant performance [63]. For example, different studies intended to generate caries prediction models to facilitate the likelihood calculation of an individual developing dental caries based on clinical findings or demographic and lifestyle factors [63,64]. Another important feature is data mining, whose strength lies in the ability of finding causal relationships and comparisons that are innate in existing data [65]. The observations were obtained by data mining analysis, while the only role of dental professional was to collect and tabulate the data.

All the above studies proved the application of AI in the current dental field to diagnose and make prognoses through extrication of useful information from large amounts of medical records [65]. Again, data mining analysis performed on a bulk of restorative data of patients revealed that differences in the material of dental restorations serve as important factors determining the lifespan of a restoration [66]. Currently, studies applying machine learning based on artificial neural networks to dental treatment through analysis of dental magnetic resonance imaging, computed tomography, and cephalometric radiography are actively underway. AI-based systems are often used for designing software programs that try to simplify data management and diagnosis in dentistry. Mostly, they are clinical decision support systems that assist and guide experts to make better decisions [67] and aesthetic mock-up [68].

AI-based systems have been used for better diagnosis, treatment planning and for prognosis prediction. AI in dentistry started procuring its role with emergence of data computation and availability of large amounts of patient data. For instance, the information acquired by radiological exam can be analysed by an algorithm which may improve and help the diagnosis and treatment phases of oral pathology and disease in an automatic way [65]. Additionally, AI technology has demonstrated excellent results in the detection of dental caries [69,70], diagnosing oral squamous cell carcinoma [71], and evaluation of the correct working length in endodontics [72–74].

In adjunct to AI, robotics can represent the next frontier of dentistry. Robotics has been added to medicine since 1992, but only in 2001, a human-controlled robot, remotely located, was able to remove a dental caries, perform an endodontic treatment and execute a crown and bridge preparation [75].

In 2017, Yuan et al. demonstrated that robots’ tooth preparation skills, such as laminate veneer and crowns preparations, are as accurate as those of human dentists [76]. Recently, a mobile wire-bending machine was introduced, which is capable of creating a fixed orthodontic retainer wire by means of intraoral scan data in only four minutes [77]. Another remarkable opportunity enabled by robotics is computer-assisted surgery. Using this approach, a navigation system may

track the position of a surgical device in real time. The guidance to the dentist is realized by the device position projecting onto the digital image of the anatomic area of interest, providing help in real-time to follow the anticipated pathways and allowing the doctor to recognize possible interference with the neighbouring tissues. Currently, the most commonly used optical tracking systems are based on capturing the position of a series of light-emitting diodes mounted on a surgical device [77]. In the future, virtual robotic surgery will allow surgeons to operate patients in a different location.

4. Discussion

This narrative review depicts the potential application of VR, AR and MR, AI and Robotics in dentistry. The decision to provide a narrative review could be considered as a limitation of this study; however, it allows the provision of an accurate overview of the recent scientific literature on the potential use of VR, AR, MR, AI and Robotics in the dental field. The broad perspective might become lost using a systematic review, since it focuses on a specific query, as in PRISMA guidelines [78]. As reported in the scientific literature, a narrative review summarizes the literature in a way which is not explicitly systematic, but it is suited to addressing a topic in wider ways [10].

In the field of dental education, VR and AR can improve the teaching of dental morphology from both an economic and practical standpoint. The use of cadavers or synthetic recreations (silicone or plastic models) represents the current gold standard for studying head and neck anatomy in dental schools and postgraduate courses. AR and VR are reusable, unlike cadavers and synthetic recreations, making them more economically viable. They can also enhance visualization of anatomical structures, thereby improving understanding of dental structures. Furthermore, using these new technological approaches may promote students’ motivation and interest in learning.

The use of virtual simulators in professional education programs can allow students to refine their clinical skills without the risk of harming a patient during the learning process and, in this era of COVID-19, to certainly avoid potential infection [17]. Using VR, AR or MR simulators, a more realistic training could also support and reinforce ergonomics, thus improving the students’ preclinical experience [79]. The type of simulation chosen by the dental student can range from simple cavity preparation to more complex overlay or crown preparation. The virtual simulator may give direct feedback to the student and therefore improve clinical skills in a faster and safer manner. Although VR, AR and MR may improve the dental education, more information about their learning theories are required [80]. Makransky et al. investigated the process of learning of immersive reality systems and highlighted the need to develop learning theories by using a research-based theoretical model so that personnel such as students, teachers, and instructional designers would possess the correct knowledge for adopting such devices [80]. Moreover, a recent review revealed that few design-oriented studies constructed their VR applications based on a specific learning theory, which serves as technical development guidance [81].

Apart from dental education, AR and VR may help to reshape clinical dentistry. Computer-generated information may be superimposed on the surgical field using AR and VR [82]. These technologies may reduce the time needed for consulting digital information, but more importantly, they allow the clinician to focus on the patient.

The application of AR and VR in clinical practice may not only be useful for dental students and clinicians as previously discussed, but also for patients. AR and VR can present suitable specific non-invasive strategies to reduce dental anxiety and treat dental phobias, one of our society’s phobic conditions [38]. AR and VR could represent useful aids to manage or even overcome dental phobias, such as by using videogames or even by the total immersion of the patient into a virtual environment. These technologies can be used to implement oral health education strategies. For example, teaching toothbrushing techniques could become more feasible, effective, and accessible to children by linking learning with fun [83]. Consequently, AR and VR based-games may also be customized to correct brushing techniques after identifying mistakes [84]. These innovative technologies can improve communication between dental practitioners, dental technicians, patients, and the multidisciplinary team. VR allows the clinician to demonstrate to patients the expected clinical outcome via a total virtual simulation. However, AR may allow for an immediate interaction between the dentist and patient. An AR device can create a 3D model that can be placed directly in the patient’s mouth, therefore providing 3D visualization for aesthetic planning [85]. An AR system can share the operator’s reality with the dental technician or another specialist when formulating a treatment plan.

AI and Robotics represent the new frontiers of digital dentistry. The artificial nature of AI allows for the elimination of potential human error, bias and feelings such as fatigue, tiredness, and boredom, which can manifest after repetitive work [86]. Human intelligence is denoted by perception and interpretation. AI cannot replace human intelligence but can instead support human interpretation and action. AI machines develop problem-solving abilities through independent learning and by utilizing human senses and mechanisms of the human mind [61]. The realization of machines learning through a bio-inspired artificial neural network is a widely used method in AI [87]. These innovative features of AI can be applied to medical decision making, offering the possibility of helping clinicians obtain expert-level information [88]. As the use of AI increases in the medical field, the role of AI in dentistry may also expand and become a reliable and friendly tool used in daily practice.

While AI helps in developing diagnosis and prognosis, robotics can assist clinicians through computer-assisted interventions. Robot dental assistants and other applications are promising; however, critical challenges limit progress, such as high costs and complex operability of the systems. Further research is needed, as the latest changes in modern robot technology have not yet been fully introduced to dental research nor have they reached technological readiness and cost efficiency to enter the dental market [58].

Data provided by multiple digital technologies, such as photographs or 3D-tracking devices, radiographic information, or intraoral images, can be integrated using these novel technologies. This integrated digital information allows for the creation of a digital patient (“virtual patient”). A clinician can then use the “virtual patient” to directly develop a digital treatment plan on screen. Possible uses include the simulation of the procedures such as surgical navigation for implant placement, design of restorations, or navigated endodontics. Moreover, using different virtual patients can allow for a patient-centred approach driven by patient-centred outcomes.        Although this work made an overview of the potential use of VR, AR, MR, AI andRobotics in dentistry, information about their precise application in the different disciplines is still lacking. Moreover, limited data are available regarding the effect of such devices on the cognitive load of the users. While a recent systematic review reported a lower or equal cognitive load of these new devices with higher performance, when compared to more traditional conditions such as display- or paper-based instructions [89], data regarding the cognitive load during their clinical or educational applications are still missing. Ethical aspects, learning theories and cognitive load should be further investigated to better exploit their potential.

5. Conclusions

Modern digital technologies can potentially reshape dentistry both on an educational and clinical level. Students may improve their knowledge and practical skills. Dental clinicians may use these technologies as useful aids in their practice. Despite the promising development of AI and Robotics in dentistry, their actual application remains primarily experimental. Future research on digitalization in healthcare, especially dentistry, should certainly focus on improving AR, VR, AI and Robotics since they can all represent modern and strategic approaches that may ensure qualitative efficient dental care.

Author Contributions: Conceptualization, G.O. (Giovanna Orsini), R.M. and F.F.; methodology, R.M., F.V., V.T., F.F. and G.O. (Giovanna Orsini); validation, G.O. (Giulia Orilisi), F.F., A.P. and G.O.(Giovanna Orsini); formal analysis, R.M., V.T., F.V. and G.O. (Giulia Orilisi); investigation, R.M. and V.T.; resources, A.P. and G.O. (Giovanna Orsini); data curation, V.T., F.V. and G.O. (Giulia Orilisi); writing—original draft preparation, R.M. and F.V.; writing—review and editing, R.M., V.T., F.V., G.O.(Giulia Orilisi), F.F. and G.O. (Giovanna Orsini); visualization, F.V., F.F. and A.P.; supervision, A.P. and G.O. (Giovanna Orsini); project administration, A.P. and G.O. (Giovanna Orsini); funding acquisition, A.P. and G.O. (Giovanna Orsini). All authors have read and agreed to the published version of the manuscript.

Funding: SISOPD (Società Italiana Stomatologia, Odontoiatria e Protesi Dentaria—Italian Society of Dentistry, Stomatology and Prosthodontics) partially supported this study. The sponsor had no role in design, analysis, and interpretation of the study.

Data Availability Statement: The data presented in this study are available on request from the corresponding author.

Acknowledgments: The authors extend their gratitude to Valentina Ragni for their precious support in database searching. Andrell Hosein is kindly acknowledged for her support in English editing.

Conflicts of Interest: The authors declare no conflict of interest.

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21 Feb
info

Virtual and Augmented Reality: Changing Horizons in Dentistry

Abstract

Background: Augmented and virtual reality (AR-VR) is a fast developing technology that has been used in the field of medicine for a long time. It has also found its way in dentistry and the preliminary assessments so far have shown promising results. Aim: The presented scoping review was conducted with an aim of identifying the current applications of AR-VR in the field of dental training and education. The paper also highlights the presently available dental simulators, their features and areas of use. Result: It was found that AR-VR is not restricted to teaching of upcoming dentists but also helps practicing physicians to return to basics and refine their skills. Inclusion of haptics provides a realistic experience by simulating the tactile sensations. Instant feedback feature act as a source of motivation to cover the missed bases. Conclusion: AR-VR technology has numerous advantages in dental education and training. However, the currently available systems require imports and are bulky to be transported in difficult terrains. Thereby it is important that indigenous systems be developed that have enhanced feasibility to be used for training of Armed Forces for managing trauma cases encountered in the field.

Keywords: Virtual reality; Augmented reality; Dentistry

1.Introduction

Virtual Reality (VR) is a computer-generated environment that provides the user with a sense of realistic environment experience using 3-dimensional (3D) models to interact with. VR has been used in the field of research and medicine since more than 25 years but has received a recent boom with increasing interest of leading application and software companies1.

Comparatively, augmented reality (AR) is a more recent technology and has been used inter-disciplinarily for treatment and education purposes.1 In the field of medicine, VR has been used as diagnostic aid, as an assistance before and during surgical procedures, imparting education and training in procedures like laparoscopic surgeries, medical database visualisation, treatment and rehabilitation of patients with autism, phantom limb pain, psychiatric disorders, palliative care for cancer patients etc2–7. Adjunctive use of VR as a teaching module has shown improvement in student’s learning curve which has further encouraged institutes to adopt the same5.

In context of dental education, since the introduction of dentistry as a separate subject and specialisation, it has been taught via didactic methods which in recent years have been aided by audio-visual projections. Coming to practical dental skills, a student is required to hone their skills on plaster models, phantom heads and extracted teeth. Though these methods have been successful, they add to monetary constraints for students by reinvestments in plastic teeth and instruments. Also, these modes present with ideal teeth morphology and conditions, restricting teaching to standard preparations which is not always encountered in live patients. The students are also not able to have a practical experience of probable medical emergencies that can be encountered in a dental setup, therefore finding themselves in a fix under clinical situations. With the plethora of advantages provided by AR-VR technology and introduction of haptic feedback technology, it has thus become necessary that the technology finds its way in regular teaching curriculum8 . The presented paper is a scoping review of the currently employed applications of AR-VR systems in the field of dentistry for the purpose of student and practitioners training and their practical application at various levels.

2. VR and AR in the field of Dentistry

2.1 Operative Dentistry and Endodontics

Operative dentistry is regarded as the “bread and butter” of the profession since it involves addressing the most common patient chief complaint of tooth decay and associated pain9-10. As a student, one learns the basics by preparing different preparations on typhodonts which is then followed by refining of skills on extracted teeth and live patients. AR-VR technology will help in bridging this gap and make clinical transition a more fruitful experience. Comparing student’s knowledge and skills of cavity preparation, Llena et al.11 compared traditional teaching methods with those imparted using AR technology. Although no significant difference was found in the level of knowledge of the two groups, a significant difference was seen in terms of the skilled parameters. Students too rated their experience of using AR to be favourable although use of computers was preferred over use of mobiles. In contrast, Quinn et al. in their pilot study found that students did not favour the use of VR simulation devices and rather preferred it as an adjunct to conventional teaching methodology12. Evaluating the learning curve of students in the clinical procedure of access opening, Suenukarn et al.13 found that using haptic VR, novice fourth year dental students were able to learn and improve the procedure in merely two to three sessions.

This was seen to be faster and consistent compared to conventional way of learning and also provided students with bimanual dexterity and force utilisation assessment. Imber et al. too supported that the evaluations obtained on virtual simulator are as reliable as those seen on mannequins14. In their prototype software design, Sararit et al. 15 appraised user acceptability of VR simulator for managing endodontic emergencies. With a few roadblocks brought to the fore by a couple of users, most of the users encouraged the use of the simulator citing its purpose, design, feasibility and usefulness in learning emergency management. Dixon et al.16 showed the application of Virteasy Dental simulator for assessing 2 mm depth cavity on a simulated block of density similar to that of enamel. They concluded that clinically relevant qualitative feedback could be provided by the simulator’s use and can help the operator in developing more complex skills.

2.2 Tooth Preparation for Prosthetic Crown

After completion of the root canal treatment, most of the restored teeth need to be reinforced by a prosthetic crown to avoid the loss of the remaining tooth structure. Thus, tooth preparation for prosthetic crown is a common procedure that a dentist needs to be versed with. It is important that the preparation has minimal flaws so that the resultant crown has a higher rate of survival and service. Comparatively, maxillary preparations are more difficult that mandibular and the same becomes a challenging task when performed in patients without prior pre-clinical practice17. Thus, this calls for use of technological advances that would provide learning dentists with practice and performance evaluation of their preparations before proceeding to clinical work. Preppr, software developed at the University of Otago, New Zealand has been used to analyse all ceramic tooth preparation for mandibular molar by students with no prior practical knowledge about the same. It showed students performing better than those taught by conventional ways and was proposed to be included as part of dental simulator systems18.

2.3 Maxillofacial Surgery

A good maxillofacial surgeon requires thorough knowledge of structural anatomy and precise and neat movements to produce good surgical results. Getting a first-hand experience on cadavers or patients is not possible for all clinical scenarios and here AR-VR technology can work wonders. AR is being used as an adjunct in various maxillofacial surgeries like orthognathic surgeries, tumor surgeries, temporomandiular joint (TMJ) motion analysis and foreign body removal, osteotomies, minimally invasive biopsies, prosthetic surgeries and dental implants19. In one of the initial studies by Wagner et al. 20 head mounted display (HMD) were used by surgeons to visualise the super imposition of bone segment or soft tissue as a real-time overlay.

This provided them with increased visual access to perform a smoother surgery. In another study, high fidelity simulators were proposed to help surgeons learn the accurate osteotomy cuts for bilateral sagittal split osteotomy (BSSO)21.Pulijala et al. developed and validated VR surgery using Oculus Rift and Leap Motion devices for Le Fort I osteotomies wherein the trainee can interact with each armamentarium and know its application22. It consisted of a 360° operating room, spherical videos and computer generated 3D models of operating room which were seen as suitable training tools by the surgeons. However, inclusion of haptic force feedback and realistic interaction with 3D instrument models was identified as an area that required further work. Yu et al.23 in their preliminary attempt showcased the advantages of the discussed technology by performing virtually simulated orthognathic surgeries before operating on actual patients. This helped in forecasting the probable patient’s esthetic outcomes and surgical success. Ai et al.24 presented a proxy VR system integrated with volumetric rendering for cranial implants to be used with a desktop computer system. However, there isn’t any further literature available about the use of the same.

2.4 Dental Implant Placement Surgeries

Dental implants are being increasingly used for rehabilitation of partially and completely edentulous cases. Placing dental implant is a technique sensitive procedure that requires precision training. For successful placement, it is important that the implant is placed in precise location with adequate thickness of bone on all sides to avoid undue implant surface exposure. VR technology has been used as an aid for treatment planning and determining this defined location to provide a smoother and minimally invasive procedure25-26. Seipel et al.25 in their initial assessment, investigated the use of a low-cost stereoscopic display system and six degree of freedom in implant placement compared to three degrees of freedom in the virtual world. In a follow up study, treatment planning of the procedure was improved to provide the clinician with six degrees of freedom in real time using computed tomography (CT) images at the voxel level27. Kusumoto et al.28 and Ohtani et al.29 individually developed systems wherein they combined the CT images of jaw bone with a VR force feedback haptic device to provide inexperienced training dentists with a real experience by simulating the vibrations and sounds of bone drilling and contra-angled hand-piece. Xiaojun and team30 proposed a modular software namely Computer Assisted Preoperative Planning for Oral Implant Surgery (CAPPOIS) that aided in pre-operative planning of the procedure. The planned procedure could then be transferred to a haptic feedback device to conduct the same on virtual jawbones before performing the same on patients.

2.5 Dental Anesthesia Administration

Inferior alveolar nerve (IAN) block is one of the most commonly used blocks in the field of dentistry and has a high reported failure rate of 20 per cent – 25 per cent31. Causes of block failure can be either anatomical, pathological, pharmacological, physiological or inadequate technique.32 Anatomical and inadequate technique are two operator related factors that can be improved upon by having a thorough knowledge of the intra- and extra-oral anatomy and repeated practice. AR-VR technology with feedback provision can prove to be advantageous in this aspect. Correa et al. evaluated the user feedback of haptic-based VR anesthesia injection training simulator on two different virtual models32.Satisfactory training results were obtained however they highlighted the scope of improvement in terms of tactile feedback. Mladenovi et al33 too supported the use of AR simulator for teaching IANB and found significantly better results in the experimental group than the control group who were taught the technique the conventional way. They however did not comment on feedback limitations of the system.

3.Currently Available Dental Virtual Simulator Systems

Realising the importance of AR-VR technology in the field of medical and dental sciences, a wide range of commercial dental simulators are now available for the masses (Fig. 1). Some of these systems are being currently used for student training and have presented encouraging results.

3.1 DentSimTM

Introduced in 2004, DentSimTM is one of the first developed dental simulators. It utilises AR which can be integrated with the existing lab mannequin. Movement of student’s hand piece during preparation and the typhodont tooth are optically tracked and analysed in real time. The tracked images can be visualised in various angles by the student on computer screen while working on the plastic teeth34.Jasinevicius et al.35 found use of the dental simulator to significantly increase the number of preparations and reduce the average time taken by students to complete the same.

3.2 Voxel-Man

Voxel-Man simulator was first introduced for middle ear virtual surgery which simulator has microtomographically replicated real teeth and a force feedback enabled dental handpiece that allows students to work on their manual dexterity and improve problem solving skills. The device has high fidelity that differentiates in tactile sensations of enamel, dentin, pulp and carious tissue, giving a real-life experience. All the models and instruments are visualised on a high resolution 3D screen with access to a variety of high and low speed burs controlled via a foot pedal. With the help of virtual dental mirror, the tooth can be viewed from all sides, magnified and be visualised in cross-sectional images. Automatic skill assessment feature evaluates the work done by student comparing it with a predefined standard as a reference preparation. Thus, students are able to get an instant feedback on their work. As a pilot test model, Pohlenz et al.36 checked the simulator’s applicability as an additional learning modality and was highly recommended by students (92.7 %). In another study by Sternberg et al38 simulator was utilised for performing apicectomies comparing 2 trainee groups in preservation of vital structures while performing the procedure in pig cadaver model. Group that received prior training on simulator showed better performance than group directly performing on cadaver models.was later adapted for dental surgeries and includes carious lesions in various configurations36-37. The

3.3 PerioSim© Force Feedback Dental Simulator

PerioSim©, developed by Luciano at the University of Illinois,39-40 is a mannequin based haptic VR simulator designed for training and performance evaluation of students, hygienists and practicing dentists in periodontal probing and white spot caries detection. Its hardware components consist of PHANToMTM Desktop haptic device and a compact personal computer. The system allows the user to interact with 3D human mouth on computer screen while working with haptic device to have a lifelike interaction with teeth and gingiva. Students can view the clinical scenario from various angulations and work with various instrument positioning. In a study by Steinberg et al.41 establishing the evidence-of-concept for using PerioSim© as teaching aid, stated that images were more realistic for teeth and instruments than for gingiva. Also, tactile sensations were more pragmatic for teeth than for gingiva. With these improvements incorporated in future, PerioSim© was seen as a useful modality to be integrated as teaching aid and evaluating student’s skills.

3.4 Simodont® Dental Trainer

Nissin Simodont® is a haptics technology dental trainer by Moog Industrial Group, Amsterdam with courseware development by Academic Centre for Dentistry in Amsterdam42. Its hardware consists of a touch panel for user interaction, a 3D display viewer, projectors for stereo vision, a virtual mirror, handpiece gimbal and foot pedal. It provides with features of height adjustment and hand and finger rest for user comfort.

To enhance student learning, the courseware can be modified by teachers to provide already present or customised cases and build patient specific exercises. Based on student performance reports can be created and exact student work can also be reviewed. Tested by Bakr et al.43 at Griffith University, Australia, Simodont® was found as a useful supplementary teaching tool by teaching staff but had technical limitations of hardware and software. Checking the efficacy of the trainer in a randomised control trial, Al-Saud et al. concluded that combination of instructor guidelines and feedback from trainer showed better performance compared to either method used alone and thus advocated its use as an adjunct44. Checking the simulators applicability for pre-clinical paediatric dentistry training, Zafar et al.45 presented that the simulator can be adequately used as an adjunct for dental training.

3.5 BoneNavi System

Developed by Ohtani et al.29 in Japan, BoneNavi is a computer-aided implant surgery support system. The system combines the use of CT images of jawbones and a VR force feedback device to simulate implant placement and surgical guide development for implant placement. These CT images are used for individualised treatment planning and it practice before carrying out the actual procedure on patient. At present, no literature providing its validation has been reported.

3.6 Virteasy Dental

Virteasy Dental is a haptic simulator developed by HRV (Changé, France) in collaboration of multiple institutes one of which is the University of Sheffield46.It simulates a completely virtual environment which consists of a virtual patient to work upon in a virtual room. It includes teaching modules related to restorations, edodontics, prosthodontics, and implantology along with operator’s assessment. The editor feature of the simulator enables the user to themselves import the intra-oral scans and create the desired pathology to work upon. The simulator has shown positive results in terms of providing clinically relevant qualitative feedback16.

4. Individual Dental Education AssistantTM (IDEA)

Making its first appearance in 2011, IDEA is a prototype software, initially developed for cavity preparation, that can be installed on any computer system47. Equipped with a stylus having six degrees of freedom, it utilises a PHANTOM® haptic device (SensAble Technologies, Inc®) to simulate realism. The system also provides access to preinstalled modules for other procedures namely, ManualDexterity™, Scaling & RootPlanning™, OralMed™ and PreDenTouch™. The procedure of cavity preparation is done on geometric 3D shapes instead of actual images of the tooth. Installed feedback system measures time taken for the task, removal of desired amount of tissue and deviation from the desired activity48. In the initial evaluation of the simulator done by Gal et al. it was concluded that the software has much potential to be used both, by professionals as well as learning students47. However, it required further improvement concerning sensation simulation and required further inputs, from educators as well as students for its further enhancement.

4.1 SimImplanto

Introduced in 2016 by Pires et al., SimImplanto is a keyboard controlled Falcon haptic device that simulated oral rehabilitation of edentulous maxillary and or mandiblar space using implants49. 3D jaw models were obtained by scanned dental casts while CT scans were used to simulate various bone densities for implant placement and drilling resistance. No further data could be found in literature that can further comment on the simulator’s efficacy and applications.

4.2 Leonardo

Distributed by GEOTAR media, Russia, Leonardo dental simulator is a mannequin based simulator which tracks interventions on teeth models in real time and gives a comprehensive feedback of all procedures50-51. The training capability of the simulator includes history taking and anesthesia selection specific to a patient and also has the scope for customisation. The system tracks the total time taken for a procedure along with effective times, amount of healthy tissue removed and excess movements during the procedure. It uses Polhemus electromagnetic motion tracking technology to provide real time feedback and used real dental equipment equipped with tiny micro sensorsTM. At a time, the system can precisely track 6 sensors simultaneously and provide with instant feedback.

4.3 SimEx Computerised Dental Simulator (CDS-100)

A proprietary product by EPED Inc., CDS-100 combines dental simulation and evaluation in a virtual 3D environment.52 It aids in providing training to the learning dentists and can be used by practitioners to develop upon their skills. The simulator provides instant feedback and has the features of recording operating procedures that can be viewed at the users or evaluator’s will. The use of the simulator looks promising; however, there is no documented literature available that supports its use.

5. Conclusion

The few studies that have utilised the AR-VR technology in the field of dentistry have shown promising results for the future use of the technology. The currently available simulators too have presented positive user feedback however they all present scope for improvements. With increasing shift of the dental fraternity towards implant-based rehabilitation of the missing tooth/ teeth, it is important that the practicing dentist be thoroughly versed with the procedure and its probable complications during the procedure. This would be further advantageous if the training is instilled during the teaching years which currently takes a back seat due to lack of confidence gained from working on acrylic models which fail to simulate the clinical scenario. Incorporation of AR-VR technology in Armed Forces will help train the surgeons on perspective trauma cases which will help them in better handling of the actual cases in the field. Thus it is imperative that resources be put into development of AR-VR technology in the field of dentistry that are not only successful in providing real-life experience but are also handy enough to be used by students and dentists in difficult terrains, who find it difficult to visit the cities for the state-of-the-art learning.

Lt Col Amit Bhandari is an oral & maxillofacial surgeon and serving in the Indian Army since 2007. He is currently posted as the head of the Department of Dental Research and Implantology in DRDO-INMAS, New Delhi.

Contribution in the current study is conception, design, data acquisition, analysis and interpretation, drafted and critically revised the manuscript and gave final approval.

Dr Vanshika Jain is a dental undergraduate, working in the field of dentistry and research since 2018. She is currently working as a Senior Research Fellow in the Department of Dental Research and Implantology in DRDO-INMAS, New Delhi. Contribution in the current study is conception, design, data acquisition, analysis and interpretation, drafted and critically revised the manuscript, gave final approval.

 Dr Rashi Bhandari is a dental undergraduate. Currently she is running her private clinic in New Delhi. Contribution in the current study is conception, design, data acquisition, analysis and interpretation, drafted and critically revised the manuscript, gave final approval.

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