Effectiveness of Virtual Reality and Interactive Simulators on Dental Education Outcomes: Systematic Review

Abstract In recent years, virtual reality and interactive digital simulations have been used in dental education to train dental students before interacting with real patients. Scientific evidence presented the application of virtual technology in dental education and some recent publications suggested that virtual and haptic technologies may have positive effects on dental education outcomes. The aim of this systematic review was to determine whether virtual technologies have positive effects on dental education outcomes and to explore the attitudes of dental students and educators toward these technologies. A thorough search was conducted in PubMed, Scopus, MEDLINE (via EBSCO), The Cochrane Library (via Wiley), Web of Science Core Collection (via Thomson Reuters), and Dentistry and Oral Science source (via EBSCO) using the keywords (student, dental) AND (education, dental) AND (virtual reality) OR (augmented reality) OR (haptics) OR (simulation) AND (dentistry) OR (dental medicine). The quality of the reported information was assessed following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement for systematic reviews. A total of 73 publications were considered for this review. Fifty-two of the selected studies showed significant improvement in educational outcomes and virtual technologies were positively perceived by all the participants. Within the limitations of this review, virtual technology appears to improve education outcomes in dental students. Further studies with larger samples and longer term clinical trials are needed to substantiate this potential positive impact of various virtual technologies on dental education outcomes.

In recent years, virtual reality and interactive digital simulations have been used in dental education to train dental students before interacting with real patients. Scientific evidence presented the application of virtual technology in dental education and some recent publications suggested that virtual and haptic technologies may have positive effects on dental education outcomes. The aim of this systematic review was to determine whether virtual technologies have positive effects on dental education outcomes and to explore the attitudes of dental students and educators toward these technologies. A thorough search was conducted in PubMed, Scopus, MEDLINE (via EBSCO), The Cochrane Library (via Wiley), Web of Science Core Collection (via Thomson Reuters), and Dentistry and Oral Science source (via EBSCO) using the keywords (student, dental) AND (education, dental) AND (virtual reality) OR (augmented reality) OR (haptics) OR (simulation) AND (dentistry) OR (dental medicine). The quality of the reported information was assessed following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement for systematic reviews. A total of 73 publications were considered for this review. Fifty-two of the selected studies showed significant improvement in educational outcomes and virtual technologies were positively perceived by all the participants. Within the limitations of this review, virtual technology appears to improve education outcomes in dental students. Further studies with larger samples and longer term clinical trials are needed to substantiate this potential positive impact of various virtual technologies on dental education outcomes.

Introduction
In recent years, virtual reality (VR) simulations have been employed in dental education as an adjunctive to the traditional skill training curriculum to train dental students before interacting with actual patients. 1,2 Dental education differs from any other form of medical education as it is a combination of theory, laboratory, and clinical practice. The challenge in dental education arises from the fact that theoretical knowledge acquisition requires spatial imagination and the patient-centered training on traditional mannequin simulation does not resemble realistic clinical situations. 3 Preclinical and clinical training is of paramount importance for developing fine motor skills to prepare dental students to engage in the dental profession. Many of the required dental education competency skills are challenging to acquire, and mandates repeated training and long practice. 4 Since the breakthrough of the novel coronavirus SARS-Co-V-2 (severe acute respiratory syndrome coronavirus 2) in late 2019, 5 all essential activities were affected, calling for social distancing, and the traditional dental teaching models of one-on-one pedagogical design had to be partially replaced by digital or virtual setups to avoid the gathering of the youth in closed spaces.
VR is gaining acknowledgment as a valuable tool for training dental students, and its use by dental schools is rising worldwide. 6 VR is defined as a computer-generated medical simulation of a three-dimensional (3D) image or environment that uses software to create an immersive computer-generated environment. Users put on a head-mounted display that places them inside an experience, where they can engage with the setting and virtual characters in a way that feels real. VR could be beneficial in dental education, permitting a patient noncontact training environment. 1,2 Augmented reality (AR) is a superimposition of computer-generated graphics over a real-life scene. It differs from VR, which does not demonstrate natural conditions. AR refers to a form of technology that integrates both real and virtual elements in a combined experience and allows learners to visualize complex spatial relationships, abstract concepts, and experience phenomena that might have been impossible in the real world, especially in surgical procedures coaching. 7,8 Immersive virtual reality (IVR) is one form of AR where the user interacts with a digital 3D environment recreated through 360 degrees actual records. 9 Haptic technology (HT) is a more recent simulation that involves tactile sensation while interacting with computer-generated objects. Haptics means the sense of touch and consists of the science of incorporating the interaction with the external environment through contact. 2 Implementing these technologies in dental education motivated designers to create virtual teeth with and without pathology, multilayered and featured with different mechanical hardness for enhanced reality. 10,11 The applications of VR in dental education attracted the attention of researchers even in the early experimental stages. 7 It was suggested that it could enhance dental education compared with traditional teaching, 1 especially in the training of restorative dentistry, 12,13 and dental surgery, 14,15 although it may expand to include endodontics and orthodontics. [16][17][18] VR enabled the delivery of distant online lectures through 3D VR workplace. The flexibility of the technology allowed the attendees' active contribution and facilitated 3D understanding of surgery and related anatomy, despite the limitation of technical issues. 19 However, the results of VR effectiveness in dental education outcomes are controversial. Thus, this systematic review aimed to evaluate the effectiveness of VR simulations on dental education outcomes. The assessed results of VR interventions were knowledge, clinical skills, attitude, and satisfaction of both learners and educators.

Protocol and Eligibility Criteria
This systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. 20  The following search terms were used for identification of eligible studies: (student, dental) AND (education, dental) AND (VR) OR (AR) OR (haptics) OR (simulation) AND (dentistry) OR (dental medicine). Keywords were adjusted for use with each of the databases mentioned earlier. Further electronic search of the relevant articles in the Journal of Dental Education and the European Journal of Dental Education was performed while running our electronic search. The bibliographies of the revealed full texts, were manually searched for additonal studies.

Study Selection
The search results were combined in a single Mendeley library (Mendeley Desktop v1.19.6) and duplicates were excluded. Two authors independently screened titles, abstracts to identify potentially eligible studies. Exclusion criteria included preliminary reports, reports without an underlying study design, and studies describing the software or hardware of the virtual technology. One co-author retrieved full-text versions of the selected studies. Selected publications were independently reviewed by two investigators.

Data Collection
Customized forms following the guidelines of the Cochrane Consumers and Communication Review Group template for review authors, 21 were used to record the following data from the selected studies: • Characteristics of the study: study design, research country, and time of intervention (before-after). • Characteristics of the study participants: number of participants, stage of education (under or postgraduate), and year of study. • Virtual intervention applied: dental specialty where simulation was used, type of the system, and the source of virtual simulations: whether access to virtual simulation was from home or at academic laboratories. • The outcome investigated; subjective or objective assessment, and the tools used to measure the output. • Results of the selected studies.

Studies Included
The study selection process for inclusion in this review is summarized in ►Fig. 1 (diagram flow). The database search strategy identified 498 potentially eligible references. Twelve additional articles were included after review of references. Duplicates were excluded. After screening titles, abstracts, 437 articles were excluded applying the exclusion criteria. Eventually 73 studies were included in the review that included 5,275 participants.
The retrieved studies were categorized according to the field of dental education in which VR was applied. ►Fig. 2 shows the percentile representation of each dental specialty in the selected studies.

Description of the Study Characteristics Restorative Dentistry
Twenty-three of the selected studies applied VR in restorative dentistry with total included participants, n = 2,201, in which 62.1%, n = 1,367 were first year dental students. The detailed characteristics of the included studies are shown in ►Table 1. HT was the most used in 18 of the selected studies, 12,22-38 VR simulator in three studies [39][40][41] and AR, 13 and interactive video games, 42 one study each. Access to all these technologies was through academic laboratories except in one study. 13 In the selected studies, students' manual skills was the most common tested outcome represented in cavity preparations in 52.17%, n = 12, 13,24,25,[28][29][30][33][34][35]38,39,41 or geometric figures 34.78%, n = 8. 12,22,23,26,27,31,32,36 Other manual skills tested were dentin etching and resin bonding, 42 and zinc phosphate cement application, 40 one study each. Four studies assessed VR on theoretical knowledge. 13,37,40,42 Results showed significant difference in 14 of the selected studies in manual clinical skills 12,13,23,27,[29][30][31][34][35][36][38][39][40][41] and two studies in theoretical knowledge. 37,40 Endodontics Six of the selected studies applied VR in endodontic with total included participants, n = 189. Characteristics of the selected studies are shown in ►Table 2. HT was applied for access opening in three studies, [43][44][45] and surgical apicectomy in two studies. 14,15 VR simulation was used in one study to teach root canal anatomy. 46 Four studies showed significant better results of the virtual technology. 14,43,44,46 Students highly appreciated virtual training in one study, 15 although suggested modifications in spatial registration precision, FFB of different tissues, and more realistic models in another study. 45

Oral and Maxillofacial Surgery
Nine of the selected studies applied VR technologies in oral and maxillofacial surgery education with total included participants, n = 730. Characteristics of the selected studies are shown in ►Table 3. Virtual patient (VP) simulation was applied in four studies, [47][48][49][50] AR in three studies, [51][52][53] and IVR in two studies. 54,55 Results showed significant differences in all the selected studies except one study. 53 Participants positively appreciated the value of the VR in education, and the test groups reported significantly higher self-confidence.

Prosthodontics
Thirteen of the selected studies applied VR in prosthodontics with total included participants, n = 815. Characteristics of the selected studies are shown in ►Table 4.
All studies applied VR in fixed prosthodontics training and evaluation, except two studies: one in preclinical removable partial denture prosthodontics course, 56 and the second in teaching occlusion. 57 Manual skills of tooth preparation was evaluated in nine of the selected studies, 58-67 acquired knowledge in one study, 57 and students' perception in three studies. 3,56,59 Nine studies reported significant statistical differences of the VR scores. 57,58,60-67

Implantology
Five of the selected studies applied dental implant education with total included participants, n = 351. Characteristics of the selected studies are shown in ►Table 5. Implant placement manual skills were assessed in four studies, [68][69][70][71] and theoretical knowledge in two studies. 70,72 Results of all the selected studies showed significant improvement of implant education outcomes in both clinical skills and theoretical knowledge.

Oral and Maxillofacial Radiology
Two studies reported the application of VR in dental radiology education with total included participants, n = 84. Characteristics of the selected studies are shown in ►Table 6. Both studies reported significant improvement of students' skill to interpret spatial information in radiographs and acquisition of theoretical knowledge, although OSCE scores were insignificantly different. 73,74 Periodontology Two studies considered HT in periodontology with total included participants, n = 55. Characteristics of the selected studies are shown in ►Table 7. HT features were evaluated as high realistic in periodontal tasks, 75 and significantly improved pocket probing scores. 76

Pediatric Dentistry
Four studies applied VR in pediatric dentistry with total included participants, n = 295. Characteristics of the selected studies are shown in ►Table 8. Pediatric VP significantly improved behavior and communication management, 77 and AR significantly improved infiltrative anesthesia administration time. 78 Students highly perceived HT in the training on pediatric clinical tasks, 79 and VR superimposing 3D holograms in local anesthesia administration. 80

Orthodontics
One study considered VR in orthodontics education. The study applied Scenario Based Learning Interactive software (SBLi) on orthodontics postgraduates, n = 9. Participants reported a high acceptance rate of the package, greater confidence applying the clinical skills covered in the modules, and reduced contact time. 81

Miscellaneous Dental Skills
Eight studies applied virtual strategies in teaching miscellaneous dental skills; critical thinking, 82 professionalism, 83 scientific writing, 84 knowledge of home dental practice, 85 head and neck anatomy, 86 dental morphology, 87 dental diagnosis, 88 and social aspects of dental care delivery. 89 Total included participants were n = 543. Characteristics of the selected studies are shown in ►Table 9.

Discussion
The application of VR in dental education has evolved increasingly, and there is significant scientific evidence that describes different virtual setups in different dental educational modules. However, the actual significance of VR simulation on dental education outcomes is not entirely clear. Earlier, VR may have been considered luxurious or optional, nevertheless in the shadow of the global COVID-19 (coronavirus disease 2019) pandemic, dental students need to proceed with their curriculum without any setbacks of the physical presence. VR may provide an opportunity for dental students to build and retain theoretical and clinical dental expertise remotely.   This systematic review showed that VR significantly enhanced the acquisition of dental manual skills even in short periods of training and, to a lesser extent, retention of theoretical knowledge. Despite the fact that few studies reported longer periods of follow-up and reported insignificant differences between virtual and traditional groups. 39,48,49,74 The diversity in students' learning styles and motivation is the crucial challenge which course designers face. The introduction of virtual simulators in the dental curriculum and the utilization of its data to stratify dental students and predict their clinical performance would provide the opportunity to tailor the learning process to meet individual diversity in students' expertise and allow students to work at their own pace. In this context, the dental curriculum could provide an education that leads to the optimal performance of each student. 26 Based on the results of this review, five broad, interrelated areas of significance arose; first, the versatility of VR applications and the increased application in some dental disciplines over others; second, HT and its wide use in dental education; third, the development of virtual dental patients to enhance dental education; fourth, the value of digital real-time feedback; and fifth, the access of students to the virtual technology.
First, VR applied in dental education showed a wide range of devices and applied technologies ranging from VR simulation with or without immersive environment, haptic simulators with or without force feedback, AR devices, real-time digital mapping and evaluation, virtual mobile platforms, video games, and other forms of virtual packages. The diversity of the individualized detailed features reflects the fact that there are no well-known educational standards for dental simulators or associated exercises. Additionally, it is doubtful how the variable reliability of the simulator systems may affect dental education outcomes. 6 Taking into consideration the complexity of the required dental training to reach a high degree of clinical competence, most of the studies included in this review applied VR in restorative dentistry, prosthodontics, and oral and maxillofacial surgery.
In contrast, few studies represented pediatric dentistry, dental radiology, periodontology, and orthodontics. Restorative dental tasks might offer the feasibility of customization of the required assignments, whereas other dental disciplines may require higher customization and knowledge to fulfill specific field's requirements. 90 Second, this review showed that HT was the most used technology, especially in tasks that require drilling and tooth preparations, which agree with Towers et al. 6 HT offers an additional dimension to VR through the sense of touch and force feedback (FFB) of the different tooth-layered structure and bone. Thus, HT proved efficient in training junior dental students the hand-eye coordination and spatial reasoning skills. It also helped students improve the preparation accuracy, shortened the preparation time in the very early stages of training, and augmented a conservative preparation approach. 15,22,37,68 However, due to the unique character of dental procedures, FFB should be improved and included as an integral feature in any educational dental simulator to enhance the perception of the tooth structure and different layers of bone. Training with FFB provides a sense of realism and allows the learner to obtain the feel of an invasive procedure in a virtual learning environment. 23,27 Third, VP showed wide applications in dental education and had a significant positive impact on manual skills and     VR haptic simulator assessment score was a significant predictor of clinical crown performance Abbreviations: CES, competency exam scores; CCO, comparative crossover; CT, comparative trial; CST, cross sectional trial; DS, dental students; RCS, retrospective cohort study; RCT, randomized controlled trial; VR, virtual reality.
theoretical knowledge acquisition. VP reduced anxiety associated with real patient's management while executing a treatment plan, exposed students to an interactive learning experience, enriched self-assessed competence, and augmented confidence to deal with actual patients. As simulators offer flexibility in terms of time, this allowed the students to repeat the procedure until they demonstrate acceptable skill levels without violating real patients and eliminating the need for prolonged direct contact. [47][48][49]53,77 Still, VP for dental training requires further development to simulate the patient's oral environment of gingival tissues, saliva, tongue movements, and reflexes as gagging, cough, and head movements. Accordingly, it would aid in teaching emergency management in the dental setting. 75 Fourth, VR applications with real-time dental training and evaluation systems were very beneficial in acquiring motor skills in preclinical settings. It allowed instantaneous feedback of the students' performance, enhanced students' self-assessment, and correction and eliminated the subjectivity of evaluation. 59,64,65 Nevertheless, dental students indicated that the simulating devices' instructions and feedback should be adjunctive to but not a replacement to the faculty feedback. Faculty should be attentive to their responsibility in teaching young dentists, treating patients with individual needs, requiring empathy and informed consent for any treatment decision. The faculty's role-model function is essential when supervising students during patient treatment in clinical practices, complex problem solving, in-depth conceptual coverage, and peer interaction. Continuous training with faculty supervision and feedback is still an anticipated key to good dental education. Fifth, most of the studies applied VR through academic laboratories, a fact that should be reconsidered, and alternative mobile platforms should be developed. To benefit from the technology, the student must be physically present on the academic campus. This situation limits to a great extent the range of getting most of the benefit of the virtual technology due to the condensed academic timetables and the increased training times required. Meanwhile, curriculum designers should notice that virtual applications on personal computers and mobiles might leave the whole education process in the student's hands, for whom some can organize their time accordingly, while others cannot. Thus, supervisors and teachers must monitor the learning process since a lack of motivation in some students would downgrade the technology's benefit. 13 In this context, tutors should operate continuous assessment in the form of pop-up quizzes, group discussions, and scheduled assignments or presentations, which would eventually lead to a blended form of learning, highlighting the teacher's role. 48 Based on the results of this review, it is recommended that low-cost VR hard and software be made readily available to create safe and cost-effective interactive educational training, allowing learners and trainees instantaneous engagement through their personal computers or mobiles. It is advised to clarify learning contents and the extent to which conventional workflows should be taught, aside from the virtual content. One form of a teaching strategy that should be utilized on a wider scale is educational video games. This form of educational material elevated students' enthusiasm for learning and made learning an enjoyable process. 42,84 Young generations are more prominent in    adapting to new technologies and increasingly familiarized with video games, encouraging further development and improvements in this field to introduce education with more fun.

Limitations
Our study has several limitations. The retrospective nature of our review, incorporating data from published studies and not on individual patients, limits the availability of information on some issues as long-term follow-up of the students and the influence of VR on clinical practices. The search process revealed heterogenous studies addressing the systematic review's aim, and while meta-analysis was not feasible, we conducted a descriptive approach for identifying the effective outcome of virtual applications. Custom-made software was only used by authors who first described them, which is a significant flaw and could represent a conflict of interest in validating a new proposed system. Also, there was a lack of randomized clinical trials with a proper sample size calculation and other efforts to avoid major bias.

Conclusion
Advanced simulation technology improved the quality of dental education outcomes. It offered applications in different dental disciplines and various clinical procedures. HT enhanced manual skills and perceived self-confidence within few clinical sessions. The most remarkable improvement was the cavity walls convergence, pulpal floor, extension of class I, cavity outline, fewer pulpal exposure, and faster preparation. Students performed better in 3D than 2D vision, with FFB than without, and with a combined instructor and device feedback than with instructor or device feedback alone. Quality of crown preparation and implant placement improved over time after using VR with or without instructor's feedback. AR reinforced orthognathic surgical training, virtual apicectomies, and local anesthesia administration. Application of VR improved acquisition of theoretical knowledge to a lesser extent. The role of the teacher and verbal instructions cannot be ruled out.