From Virtual Reality to Reality: Fine‐Tuning the Taxonomy for Extended Reality Simulation in Dental Education

ABSTRACT

Introduction

Digital simulation in dental education has substantially evolved, addressing several educational challenges in dentistry. Following global lockdowns and sustainability concerns, dental educators are increasingly adopting digital simulation to enhance or replace traditional training methods. This review aimed to contribute to a uniform taxonomy for extended reality (XR) simulation within dental education.

Methods

This scoping review followed the PRISMA and PRISMA‐ScR guidelines. PubMed/MEDLINE, EMBASE, Web of Science and Google Scholar were searched. Eligible studies included English‐written publications in indexed journals related to digital simulation in dental/maxillofacial education, providing theoretical descriptions of extended reality (XR) and/or immersive training tools (ITT). The outcomes of the scoping review were used as building blocks for a uniform of XR‐simulation taxonomy.

Results

A total of 141 articles from 2004 to 2024 were selected and categorised into Virtual Reality (VR), Mixed Reality (MR), Augmented Reality (AR), Augmented Virtuality (AV) and Computer Simulation (CS). Stereoscopic vision, immersion, interaction, modification and haptic feedback were identified as recurring features across XR‐simulation in dentistry. These features formed the basis for a general XR‐simulation taxonomy.

Discussion

While XR‐simulation features were consistent in the literature, the variety of definitions and classifications complicated the development of a taxonomy framework. VR was frequently used as an umbrella term. To address this, operational definitions were proposed for each category within the virtuality continuum, clarifying distinctions and commonalities.

Conclusion

This scoping review highlights the need for a uniform taxonomy in XR simulation within dental education. Establishing a consensus on XR‐related terminology and definitions facilitates future research, allowing clear evidence reporting and analysis. The proposed taxonomy may also be of use for medical education, promoting alignment and the creation of a comprehensive body of evidence in XR technologies.

1. Introduction

The development of digital simulation in dental education emerged as a strategy to cope with imperative simodontal challenges. Limitations associated with extracted teeth for training, challenging recruitment of patients, curriculum overcrowding, and shortages of teachers in dental schools are recurrently reported in the literature. Furthermore, with the continuous aim to improve quality and growing accountability requirements for schools, the need to provide evidence of clinical competence together with the striving for patient‐free clinical assessments has drastically pushed forward technological innovation for dental training [1, 2, 3, 4, 5].

Following several worldwide lockdowns, current climate changes and growing sustainability requirements in dental training, dental educators have drastically changed their teaching strategies [5, 6, 7, 8]. Digital simulation technologies are increasingly being implemented in dental schools, complementing or replacing traditional preclinical and clinical training. These technologies offer opportunities such as haptics, rotative views, real‐time feedback and objective assessment, providing students with unlimited opportunities for practice at their own pace, without producing disposables or waste [4, 9, 10, 11, 12, 13]. These opportunities also facilitate training within the model of deliberate practice, essential for achieving expert performance outcomes, involving structured tasks with well‐defined goals, continuous feedback and ample opportunities for repetition, which are feasible in simulated digital environments as preparation for a clinical task [2, 13, 14].

At this point in the development and implementation of digital simulation in dentistry, different training systems, including desktop pcs, haptic desktops, digitally enhanced phantom heads, along with digital dental trainers based on haptic virtual reality (VR), augmented reality (AR) and mixed reality (MR), have been consistently addressed in the literature with the collective term of VR‐simulation [12, 15, 16, 17]. Several authors have delivered some theoretical structure to the matter of digital simulation in dental education. However, the variety of approaches reported in the literature entangles an accurate description of the available technologies, thus building up a puzzling body of evidence that challenges both device and research outcomes comparison [3, 12, 16, 18].

The conventional understanding of a VR environment is frequently addressed as a completely synthetic digital world in which the operator is entirely immersed, and interaction is achievable. The following three features are therefore key to defining VR: complete synthesis, immersion and interaction. Where VR and the real world merge, arises the concept of Mixed Reality (MR). MR includes several types of hybrid environments and is defined as any case in which an otherwise real environment is ‘augmented’ by means of virtual objects [19, 20]. The concepts of Extended Reality (XR) and Immersive Training Tools (ITT) gradually become prominent in the literature as more accurate collective terms for the different digital simulation options in healthcare training.

These concepts fit the understanding of a ‘virtuality continuum’ moving from reality to virtuality and the immersion prerequisite when it comes to digital simulation trainers [21, 22, 23, 24, 25].

The broad hardware differences between the available simulation devices and the various technologies incorporated, add another dimension of complexity when it comes to describing and comparing XR simulation for research purposes or to make educational choices [3, 21, 26]. Two main hardware components constitute the base of dental XR‐simulation: an ergonomic multi‐sensory collocation platform that facilitates an immersive interaction between the operator and the virtual environment and a haptic device to provide stable and high‐fidelity force/torque feedback to the operator's hand [27].

Defining key concepts and terms is critical in scoping reviews. In dentistry, however, the categories of XR‐simulation often intersect and are not distinctly defined [18]. Carroll et al. [28] also showed that 70% of the related articles in medical digital simulation either ‘misidentified or misclassified’ simulation types, highlighting the ambiguity surrounding proper definitions. Similarly, Kardong‐Edgren et al. [29] also noted that the terminology for VR in the field of medicine lacks consistency.

The present scoping review was conducted to assess the current use of XR‐related taxonomy in dental education research in order to generate a definitional uniformity. This involves examining how different XR technologies are described in dental education research and determining the feasibility of achieving a general description framework.

2. Materials and Methods

This review was peer‐reviewed and designed following the Preferred Reporting Items for Systematic reviews and Meta‐Analyses (PRISMA) and PRISMA extension for Scoping Reviews (PRISMA‐ScR) guidelines for conducting systematic scoping reviews [30, 31]. The study protocol was developed based on the PRISMA protocol guidelines (PRIMA‐p) and registered on the Open Science Framework (https://osf.io/ys849) [30]. PubMed/MEDLINE, EMBASE and Web of Science were searched in July 2024. Additional research was also carried out in the grey literature using Google Scholar, as well as a manual search on reference lists of the included studies. An online software reference manager (EndNote X7, Thomson Reuters, Philadelphia, PA) was used to collect references and remove duplicate articles.

2.1. Eligibility Criteria

Peer‐reviewed, English‐written publications in indexed journals, referring to development, implementation, assessment and/or research regarding digital simulation in dental/maxillofacial education were included in this review, without any limitations regarding study design or year of publication. Each study must include a theoretical description of XR and/or the investigated ITT.

2.2. Exclusion Criteria

Articles regarding digital simulation outside the dental/maxillofacial field, not providing definitions or a theoretical frame about the systems researched, and reports about the use of XR for dental phobia or any other purpose that did not involve dental education were excluded from this selection.

2.3. Selection of Sources of Evidence

The performed search strategy included the different variations of XR and hardware in dental ITT, together with their different applications in dental education. (Table 1) The selection was carried out in two phases. In phase one, three dentists/teachers experienced with XR‐simulation in dentistry, independently screened titles and abstracts of all identified references. In phase two, the same three reviewers applied the eligibility criteria to the full texts. Any disagreement was solved by a consensus discussion. The final selection was based on the full text of the publication. Collected data items included author, year, XR definition, used hardware and systems, and related description.

TABLE 1.

General search strategy.

(“computer simulation”[tiab] OR “motion tracking”[tw] OR “augmented reality”[tiab] OR “virtual reality”[tiab] OR “mixed reality”[tiab]) AND (“force feedback”[tw] OR haptic*[tw] Or depth[tw] OR perception[tw] OR 3D [tw] OR stereoscopic[tw] OR immer*[tw] OR scan*[tw]) AND (dentistry[MeSH Terms] OR oral surgery[MeSH Terms] OR prosthodontics[MeSH Terms] OR orthodontics[MeSH Terms] OR endodontics[MeSH Terms] OR cariology[tw] OR crown[tw] OR preparation[tw] OR implant*[tiab] OR dent*[tiab] OR restorat*[tiab] OR exodont*[tiab] OR stomatol*[tiab] OR oral*[tw]) AND (educat*[tw] OR didact*[tw] OR learn*[tw] OR teach*[tw] OR train*[tw] OR licenc*[tw] OR test*[tw] OR assess*[tw])

A systematic narrative synthesis was completed with information presented in the text and tables to summarise and explain the characteristics and findings of the included studies. The narrative synthesis explored the relationship and findings both within and between the included studies to build general definitions for XR in dental education and achieve a uniform description of the existing technologies within the frame of the presented taxonomy. Atlas.ti (GmbH, Berlin, Germany) was used for this analysis.

3. Results

The literature search provided 1.197 results from 3 search engines: 485 from PubMed, 437 from Embase and 275 from Web of Science. Of these results, 838 were excluded during the title filtering process, leaving 359. After that, 52 duplicate studies were excluded, leaving 307. In the final screening, 166 papers were excluded after reviewing the full‐text articles. Afterwards, the reference lists were reviewed and assessed for eligibility, leaving 141 articles for the final review (Figure 1). The relevant articles spanned a period from 2004 to 2024. The selected studies were related to digital simulation in dental/maxillofacial education, including a theoretical description of XR.

FIGURE 1.

Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) flowchart illustrating the process used in the selection of specific articles.

The selected studies were categorised based on the type of simulation: VR, MR, including AR, augmented virtuality (AV) and, finally, computer simulation (CS). (Figure 2).

FIGURE 2.

Virtuality continuum adaptation from Milgram & Kishino [19] (a) Augmented Reality (AR) – SimtoCare Dente (SimtoCare, Vreeland, the Netherlands). (b) Virtual Reality (VR) – Simodont Dental Trainer (Nissin, Nieuw Vennep, the Netherlands).

Within each category, definitions and/or descriptions were extracted and are presented in Table 2.

TABLE 2.

Categorisation of selected studies.

Type of simulation	Countries	Years	N	References
Virtual Reality (VR)	Japan, Taiwan, China, Thailand, India, Korea, Israel, Iran, Saudi Arabia, Pakistan, Austria, Poland, Switzerland, England, France, the Netherlands, Italy, Portugal, Germany, Finland, the United States, Canada, Australia, Brazil, Mexico, Cyprus, Latvia, Qatar, Turkey	2004–2024	95	[2, 9, 16, 18, 20, 21, 22, 24, 26, 27, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117]
Mixed Reality (MR)	Austria, Italy, Portugal, Germany, England, Japan, the United States, Cyprus, Qatar, Singapore	2016–2024	13	[16, 20, 21, 24, 39, 74, 75, 96, 98, 99, 114, 118, 119]
Augmented Reality (AR)	Spain, Poland, Austria, England, Germany, Switzerland, Italy, Portugal, Serbia, Pakistan, Korea, Taiwan, Iran, China, Australia, the United States, Canada, Brazil, France, Qatar, Turkey, Saudi Arabia	2004–2024	50	[3, 16, 20, 21, 24, 37, 38, 39, 44, 48, 49, 50, 51, 53, 54, 55, 58, 60, 65, 66, 71, 74, 88, 89, 99, 102, 105, 107, 108, 109, 111, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137]
Augmented Virtuality (AV)	France, Qatar	2019, 2024	2	[18, 36]
Computer Simulation (CS)	Germany, France, England, the United States, Mexico, China, Saudi Arabia	2007–2022	9	[9, 22, 36, 47, 138, 139, 140, 141, 142]

Ninety‐five (n = 95) studies included a definition/description of VR. The most recurrent features within these definitions were stereoscopic (3D) visualisation of models and/or environments (n = 51) and different degrees of user immersion (n = 42), including complete immersion systems, semi‐immersion systems and non‐immersion systems. The ability of the user to interact with the simulated models (n = 47), and tactile sensation or haptic feedback (n = 29) were also repeatedly mentioned. The ability of the user to modify the virtual models was only mentioned in a smaller group of studies (n = 9) and different VR‐devices were mentioned: VR‐dental‐simulation‐devices (n = 6), VR‐Headsets (n = 27), VR‐desktop‐devices (n = 9) and smartphones (n = 2).

MR was only defined in thirteen (n = 13) of the selected studies, mainly as a blend between the physical and the virtual worlds. Fifty (n = 50) of the selected articles provided a definition of AR within dental or maxillofacial education. In these definitions, the most relevant features included AR as a combination, blend or superimposition of digital information on the real world (n = 47) that enhances, enriches or augments the real world with digital elements (n = 41) and allows interaction with the user (n = 16). These digital elements can be merely informative (textual or numerical data) but mostly include 3D models (n = 12). The concept of augmented virtuality (AV) is only mentioned twice (n = 2) as the inclusion of real elements in a virtual environment, digitally imposing an image of the user in the virtual environment, enhancing in this way the virtual world.

CS or desktop simulation was also described in nine (n = 9) of the selected articles. CS was mostly used as an umbrella term for computer‐assisted simulation in general (n = 6), while only three (n = 3) articles approached CS as desktop training modules.

General features of XR‐simulation in dentistry are presented in Table 3. XR features that were recurrently found in the reviewed literature included stereoscopic (3D) vision, users' immersion, interaction, modification possibilities and the presence of haptic feedback. These features are generally part of the description of XR devices and provide a standardisation ground, that is building blocks, for XR taxonomy in dentistry.

TABLE 3.

Digital simulation in dental education within the virtuality continuum and main available features.

Simulation type Features	Virtual reality	Mixed Reality		Computer Simulation
		Augmented Reality	Augmented Virtuality
Stereoscopic vision	Available	Available	Available	Not available
Immersion	Complete/Semi	Complete/Semi	Complete/Semi	None
Interaction	Direct manipulation of virtual models	Direct manipulation of virtual models	Direct manipulation of virtual models	Mouse/keyboard/touch screen manipulation of virtual models
Haptic feedback	Available	Available	May or may not be available	May or may not be available
Modification	Direct modification of virtual models	Direct modification of virtual models	Direct modification of virtual models	Editing software

Source: Adaptation from Saghiri, Vakhnovetsky & Nadershahi [18].

3.1. Stereoscopic Vision

The concept of stereoscopic vision is related to the ability to provide 3D images through binocular vision. To achieve the reception of 3D images by the human eyes in a digital environment, two identical images with a slight difference in the focus position with respect to the horizontal plane, positioned side by side, are projected using a polarised filter, which may be given by 3D glasses or a screen [92]. The result of this process provides the user with the perception of depth, which has a dominant effect on the feeling of immersion [79, 92, 143]. Several XR‐simulation devices in dental education are equipped with stereoscopic displays, for example Simodont Dental Trainer, SimtoCare Dente and Virteasy (HRV Simulation, Changé, France).

3.2. Immersion

This feature defines the degree of perception of the virtual world by the user. The higher the level of immersion, the deeper the user's mental engagement and the stronger the feeling of being in an authentic environment. To provide a high degree of immersion to the user in simulated dental procedures, various technological tools are used, such as optical devices that provide stereoscopic vision, devices for tracking movements (body, head) and haptic technology. The different degrees of immersion of the user have been defined as complete immersion, semi‐immersion and non‐immersion systems [3, 27, 53].

3.3. Interaction

In the field of digital dentistry, the concept of interaction refers to the ability of the user to perform different actions on a virtual object projected in a digital device, such as rotation, translation, increase or decrease of the size, selection or discarding. This interaction can be performed, among others, by using hands on a touch screen, a computer mouse, a keyboard, haptic gloves, virtual instruments and motion‐tracking devices [21, 51].

3.4. Modification

The term modification refers to the ability of the user to transform, in terms of shape and volume, a virtual object according to the task to perform. It differs from interaction in the capability of creating something new or delivering a new outcome from an existing model; that is, to say the capability to transform a digital model instead of only manipulating it [51].

3.5. Haptic Technology

The term ‘haptic’ means relating to or proceeding from the sense of touch [143]. In XR simulation it is possible to translate tactile sensations to the user and allow them to feel digital objects programmed under volumetric algorithms. A manipulation device is required to deliver force feedback; this is normally a robotic arm able to apply a degree of opposing force to the user along the x, y and z axes [52]. A remarkable characteristic is that the force feedback can vary depending on the simulated scenario, specifically in XR simulation for dental education, as there are several kinds of interaction algorithms made to replicate specific scenarios such as drilling into different dental tissues, ultrasound scaling or bone drilling [81]. This technology allows the users to interact with a 3D object and also bring modifications into the virtual world. Several authors have related the use of haptic technology to XR dental simulators as a crucial factor for successful implementation, users' acceptance and performance [33, 37, 42, 50]. McAlphin et al. [56] mentioned that a haptic‐enhanced XR simulator provides accurate skill training by means of hand‐eye coordination, the sense of resistance, touch and direct feedback.

4. Discussion

Articles included in this scoping review provided a wide definition range regarding the different environments available in dentistry within the virtuality continuum and their characteristic features. Although many authors agreed on the main features of XR‐simulation for dental education, the encountered classification and description of the different systems reported were widely dissimilar, challenging the consolidation of a general taxonomy for XR‐simulation while complicating evidence appraisal and comparisons between systems.

Available generic definitions from the XR‐engineering world may differ from those available for simulation in dentistry. This is due to the specificity of the simulated procedures and their characteristics in dentistry. To achieve a general taxonomy of XR‐simulation in dental education, features that were recurrently found in the reviewed literature were used as building blocks to achieve a general definition of AR, VR, MR, AV and CS in dentistry. These features included stereoscopic (3D) vision, different levels of user's immersion, interaction, modification possibilities and the presence of haptic feedback. Together with traditional definitions of XR, which originated from computer sciences, [19] general definitions of the different components of the virtuality continuum were formulated to facilitate a better understanding of the available evidence.

Based on this review, VR is frequently used in dental education as an umbrella term for all forms of XR‐simulation environments. The conventionally held view of a VR environment is a completely synthetic world in which the participant is totally immersed and able to interact with. Such a world may mimic the properties of some real‐world environments, either existing or fictional; however, it can also exceed the bounds of physical reality [1, 19, 90, 109]. What may be overlooked in this definition, however, is that the VR label is also frequently used in association with a variety of other environments, to which total immersion and complete synthesis do not necessarily pertain but which fit somewhere else along a virtuality continuum [17, 19, 61]. VR can be defined, therefore, specifically for dental education, as a completely synthetic world with stereoscopic vision in which the participant is totally immersed and able to interact with haptic feedback while also being able to modify virtual objects. An example of a VR dental simulator is the Simodont Dental Trainer. (Figure 2a) This simulator uses 3D glasses and a 3D display to acquire stereoscopic vision and an arm with haptic feedback connected to an air rotor to simulate hardness [92]. As mentioned before, when using the term VR to describe a system, it is important that there is a complete immersion of the user in the virtual environment [19, 20].

MR was only defined in thirteen of the selected studies, mainly as a blend between the physical and the virtual worlds. MR is the merging of the real and virtual worlds. The most straightforward way to view a MR environment is one in which objects from both the real and the virtual world are presented together within a single display, that is, anywhere between the extremes of the virtuality continuum [18, 19]. A rather uniform vision about MR was found in this scoping review; however, a more specific classification including AR and AV might be necessary to improve taxonomical accuracy in the literature. The level of immersion in the MR environment can be complete, semi‐immersive or non‐immersive depending on how the environment is displayed while the objects within the environment can be interacted with and modified. Immersion, interaction and modification can all be achieved on different levels in dental MR‐simulation, depending on the instruments available in the different environments, such as VR‐headsets, haptic feedback or specific cutting/rotary instruments [16, 20, 21, 22, 24, 39, 74, 96, 97].

Within the definitions or descriptions used in the selected literature for AR, the most frequent description found included AR as a superimposition of digital information into the real world that enhances or augments the real world with digital elements and allows interaction with the user, in line with the general definition of AR. These digital elements can be merely informative (textual or numerical data) but mostly include 3D models [19]. In consequence, an operational definition of AR in dental simulation includes any simulated environment in which an otherwise real environment is ‘augmented’ by means of virtual (computer generated) dentistry‐related objects. AR is often used in a digital simulation environment, superimposing virtual objects on real structures, allowing users to visualise the virtual content, such as surgical plans or anatomical structures, superimposed on the real surgical field [51, 58, 89, 144]. SimtoCare Dente is an accurate example of an AR‐dental trainer in which digital models are projected on a real phantom head for context and physical support in order to provide a close‐to‐reality experience [13]. (Figure 2b) On the other hand, AV can be defined as a subclass of MR in which a virtual environment is augmented by means of superimposed representations of real objects. The virtual environment and its objects can interact with the digital representation of real objects and be modified. In both AR and AV, the virtual environment and/or objects can be manipulated and modified; what changes is the original environment that is being augmented [3, 16, 18, 20, 21, 24, 36, 37, 39, 44, 49, 50, 51, 53, 54, 55, 58, 60, 65, 66, 71, 74, 88, 90, 120, 121, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137].

Finally, CS is an umbrella term used for computer‐assisted simulation in general, which presents a digital training environment where stereoscopic vision and immersion are not available as objects are displayed in a single screen. Interaction of the user with digital objects is only provided through mouse, keyboard or touch screen manipulation, although haptic feedback might be present through simple force feedback devices [9, 36, 47, 116, 117, 118]. CS has, however, not been placed in the virtuality continuum for dental XR simulation as it lacks any degree of immersion (Figure 2).

Agreeing on a general taxonomy for XR‐simulation in dental education provides the opportunity to review available literature from a standard perspective while correctly formulating and referring to simulation research in the future. Furthermore, it would be interesting to also carry out this exercise for XR‐technologies in the medical education domain to align terminologies between healthcare education and dentistry and allow the construction of a collective body of evidence.

Achieving a uniform taxonomy for XR simulation for dental education could also support the selection of suitable devices for the diverse needs of different dental schools. The present review focused on the taxonomy for XR technology in dental education and did not summarise the learning outcomes of XR training or the effect of the different components of this technology on the learning process, which could also support the selection of devices. Future research should consider longitudinal studies to describe the learning process with XR simulation including long‐term skill retention, transferability to clinical settings. Future reviews could also incorporate publications in other languages and a more diverse number of search engines.

Standardising XR terminology and methodologies through the development of guidelines and collaborative efforts will enhance comparability and consistency across studies, thus improving the generalisability of the findings. Enhancing technological accessibility by exploring cost‐effective solutions and improving usability can reduce barriers to adoption. Comprehensive studies on user experience and the development of robust training and support systems will also help maximise the potential of XR technologies in dental education.

5. Conclusion

This scoping review highlighted the challenges in establishing a general taxonomy for extended reality (XR) simulation in dental education. While agreement was found among authors regarding the main features of XR‐simulation, such as stereoscopic vision, immersion, interaction, haptic feedback and modification of digital models, there was a lack of consensus in the general definitions within the virtuality continuum. Virtual reality (VR) was commonly used as an umbrella term for several XR‐simulation environments, even though it encompasses a completely synthetic world where users are fully immersed, interact with the environment and can modify virtual objects. The presented taxonomy offers opportunities to relate findings more precisely to the specific technologies, avoiding misinterpretation of evidence. Mixed reality (MR) combines real and virtual worlds, allowing various levels of immersion, interaction and modification. Augmented reality (AR) augments the real world with virtual objects, enabling interaction and modification of the augmented environment. Augmented Virtuality (AV) augments a virtual environment with representations of real objects, offering similar interaction and modification capabilities.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.