The New Age of Prosthodontics Education: Digital Prosthodontics and Simulation
Background: Dental education is rapidly changing with digital dentistry, particularly in prosthodontics, and augmented reality simulations along with haptic feedback have enhanced this transformation.
Results: This article reviews the features of one such device currently being piloted at the University of California, Los Angeles, School of Dentistry. The impact on student training and education is explored.
Practical implications: The future of learning in a virtual environment has the potential to transcend geographical boundaries.
Keywords: Haptic, simulation, training, augmented reality, education
Advancements in digital prosthodontics have shaped the practice of dentistry. It is no surprise that dental education models have also evolved, as recent technological advancements present promising enhancements to student education. For example, direct intraoral scanning has become more popular as its accuracy continues to improve, and digital impression techniques are being taught at the predoctoral level by more dental schools. Dental educators have the opportunity to highlight digital advancements and ensure student learning is benefited by the incorporation of haptic technology into dental school curriculums. The removable prosthodontics courses at the University of California, Los Angeles (UCLA), for example, cover fabrication of removable partial dental prosthesis frameworks and complete removable dental prostheses via digital design and manufacturing. In clinical fixed prosthodontics, students can scan preps and mill restorations for their patients.
While the advantages of digital dentistry are numerous at the clinical level, at the preclinical level, the scope of haptic technologies’ potential benefit is just beginning to be explored. [1,2] Digital dentistry may be incorporated into preclinical training by utilizing computer-aided design (CAD) software and practicing computer-aided manufacturing (CAM) workflows, and also with other technology that can simulate dental procedures to improve dexterity and standardize treatment and objectively evaluate performance. Historically, students in their first year of dental education begin practicing their manual dexterity on typodonts. Students then advance from desktop typodonts to mannequin heads that simulate a clinical setting. Typodonts simulate dental arches and are typically students’ introduction to drilling their first “tooth.” Typodonts sit in mannequin heads to teach students about appropriate clinical posture and ergonomics. Typodont teeth can be individually replaced and are even fabricated with artificial caries to teach students the difference between sound tooth structure and clinical tooth decay. While typodonts have been utilized in dental schools for many years, many experienced practitioners agree that these resin teeth are softer and cut differently than real teeth.
Virtual and augmented reality technologies have advanced and expanded their applications into the medical and dental arena. Augmented reality combines a real-world environment with computergenerated perceptual information.  It is no surprise that the dental field has recognized augmented realities’ potential to improve dental education. Haptic training simulators can be combined with other methods in preclinical dental skills development that may ease the transition into clinic.  These haptic training simulators may also improve training at the dental student and graduate student levels through patient-based workflows.
Haptic Training Simulators Applications in Prosthodontics
Based on technology from Fokker Aircraft’s pilot flight tests, haptic training simulators are the next-generation dental training tool.  It uses the latest technology available to create a realistic training experience that incorporates perception and manipulation of objects using the senses of touch and proprioception. The haptic training simulator creates an experience that mixes reality with virtual reality objects. It integrates an adjustable phantom head for hand and finger rests and a handpiece and mirror that is movable within a viewing field to simulate the bimanual use of these instruments. The handpiece can provide haptic feedback. This allows the trainee to learn tactile sensations as a bur cuts through the tooth in order to associate finger pressure, resistance with the depth cuts and visual cues of the simulated tooth preparations. [1,4] This haptic feedback is specialized to simulate the different sensations of prepping enamel versus dentin.  Because the trainee views the simulation through a fixed screen, the trainee is forced to practice proper ergonomics and indirect vision as needed (FIGURES 1 and 2).
Ultimately, this may help to minimize the gap between preclinical training to the clinical setting. Newer-generation haptic training simulators’ patentpending concepts and exercises set them apart from other simulators on the market. In light of new protocols in place in most dental schools due to the COVID-19 pandemic, these simulators’ application in prosthodontics has never been more relevant.
Benefits for Predoctoral Education
From a predoctoral education standpoint, a haptic dental simulator has multiple advantages over typodont-based preclinical learning. [7–10] Students typically start with benchtop preparations on a typodont to familiarize themselves with tools and equipment, such as handpieces or matrices, all with direct vision. They then progress to a phantom head mannequin, where those same typodonts are utilized to improve manual dexterity as well as familiarity with patient positioning, ergonomics and indirect vision. Downsides to the use of a phantom mannequin include: the costs associated with plastic teeth, where each practice session has a fee associated with it; expert evaluation of the procedure often occurs at the end with no evaluation during the procedure; and inhalation risks of the aerosolization of particles. There is also no pathology that is treated in these exercises. When introduced to haptic technology, dental students valued and appreciated the additional educational benefits the Simodont Dental Trainer can offer. 
Benefits Breakdown No Waste
With haptic simulators, there is no waste of typodont teeth. There is no need to waste time replacing teeth in the dental arch or spend money purchasing replacement teeth. Students can simply restart the preparation or exercise by selecting that function on the keypad.
Tactile Sensation of Enamel vs. Dentin vs. Caries
Unlike plastic teeth that do not feel or look like natural tooth structure, the caries preparation module provides tactile sensation that replicates enamel, dentin and caries. This added tactile sensation prepares students for real patient scenarios and gives them a better idea of what to expect before excavating real tooth decay.
Manual Dexterity and Posture
Unlike with typodonts, haptic simulators force students to posture themselves appropriately and use indirect vision.
Track Student Progress
The virtual reality simulator can record the entire exercise and provide evaluation or guidance of the performance during the exercise in order to pinpoint moments that may be corrected or adjusted. The volume of desired and undesired preparation can also be measured to provide immediate feedback to the student.
The various modules offered by SIMtoCARE are applicable to many levels of training, which include implant surgery among others. The results for all modules can be evaluated and stored for external assessment.
The modules related to manual dexterity (FIGURE 3) allow dental students to improve their basic dexterity and indirect vision by prepping shapes onto blocks. Indirect vision skills can also be practiced using the dental mirror tool. The exercises in this module contain various shapes with target material that needs to be removed. The target is surrounded by a leeway. The target and leeway are placed in a block-shaped container. The target needs to be drilled out accurately and the leeway is a tolerance zone. Touching the leeway with the bur is acceptable but should be avoided as much as possible. The container should not be drilled. The shapes in the exercises are channels, circles and crosses, with a leeway thickness of either 0.4 or 0.2 mm, offering various levels of difficulty. During the exercise, the elapsed time and percentages of material removed are recorded.
Within the operative dentistry module (FIGURE 4), students can practice caries preparations.  The tactile feedback changes as students prepare enamel, dentin and caries. The cases contain various teeth with different types of caries and different levels of difficulty. The first step is to analyze the caries problem and come up with a treatment plan. Subsequently, the treatment plan is executed and caries can be drilled out where applicable.
Within the prosthodontics module (FIGURE 5), students can perform exercises related to both fixed and removable prosthodontics. In regard to crown preparations, these haptic simulators allow the user to see the original shape of the tooth as they prep to visualize the amount of reduction they have completed. Students can also prepare fixed partial denture preparations to assess the path of draw as well as other indirect restorations such as inlays or onlays. Removable prosthodontics can also be part of the module, allowing trainees to practice rest seat and guide plane preparations.
The endodontics module allows the trainee to perform access cavities with visualization of the root canals. The cases contain various teeth that require different approaches for creating the access cavity. The first step is to analyze how the root canal can be best reached while preserving as much tooth structure as possible.
This module contains exercises with cases to train for implant placement (FIGURE 6), with various jaw models that require implants in different locations. The first step is to analyze the specific aspects of the location and plan the correct implant size and type. Next, the location and angle of the planned implant is determined then executed by preparing the osteotomy sites.
One of the major areas where patient-specific learning is lacking is surgically at the postgraduate level. The simulators allow residents to import patient CBCT files and practice implant placement. Surgical training in an augmented reality environment allows the user to drill into bone with differing quality and feel the difference in haptic force feedback when switching from one drill to the next.  Importing DICOM files into the software also allows the student to see their progress in different views of the imported CBCT. As real-time navigation is becoming more popular,  the steep learning curve associated with dynamic implant placement can be flattened with practice using dental simulator technology that provides immediate feedback during augmented reality implant placement.
Problem-Based, Patient-Specific Learning
This module contains exercises based on patient-specific scans. The haptic training simulator has the ability to import intraoral scans or scans of a dental cast of real patients. A digital dental cast is a life-size likeness of some desired form, formed from a scan of a material poured into a matrix or of an impression. Perhaps the most promising application of this technology is the ability to perform an anticipated treatment in a simulation and evaluate performance all prior to direct patient care. For example, prior to any student performing a procedure on an actual patient, they could import the case in the simulator and rehearse the preparation and steps virtually. In aviation, this is often referred to as briefings, an opportunity to rehearse the steps of a procedure you anticipate performing. This application may allow providers to practice treatment, reduce and anticipate errors and improve overall treatment outcome.
With the technology available using the simulators, educators may create custom “model” patients with the desired pathology that then allows students to treat the exercise as they would a real patient. Some programs may have questions associated with the patient for the student to answer, reinforcing theoretical knowledge and applying it in a clinical scenario. This allows students to practice and reinforce the critical thinking that is required during dental procedures on real patients. These exercises may get more complex as the students’ experience improves and may be applied to procedures in operative dentistry and fixed and removable prosthodontics.
These preoperative patient exercises may be evaluated by an expert to allow the trainee to have feedback on their performance prior to direct patient care and the rendering of irreversible changes.  This is particularly helpful for a student who may practice prepping their first patient’s crown on a virtual model prior to direct patient care or to visualize the necessary amount of tooth reduction needed for a super erupted tooth, a tilted tooth or a tooth in a severely crowded quadrant of the mouth. At the graduate level, residents can practice prepping fullmouth rehabilitations on their patient to help them with time management and prevention of technical errors that they may face in clinical practice.
An additional advantage of dental simulation technology is that all recorded data can be reviewed by the student, allowing them to self-assess and identify areas that need improvement. For each exercise within each module, data is collected that calculates the student’s ability to complete the task with accuracy and records the time it takes to complete each exercise. For example, in the operative module, the amount of caries removed is recorded. In the manual dexterity module, the percentage of material removed is recorded as well as the amount of unwanted object removal, providing feedback in real time. Another unique feature of these simulators is that students can export their completed exercises as a standard tessellation file (STL) and import these files into self-assessment software, such as E4D Compare, which can provide quantifiable feedback of a student’s work on the simulators compared to a control. This software could be used by faculty members as a mechanism to evaluate student work objectively and for students to use as a self-assessment tool.
Considerations and Conclusions
■ The important consideration of simulations are: Do they mimic real-life situations enough so that the training acquired during the exercises are applicable to the clinic setting and not detrimental?
■ Regarding early versus late exposure to dental simulators, one study showed that haptic simulators could be combined with other methods in preclinical dental skills development and that there is no clear evidence that early exposure to haptic feedback improves psychomotor skills in restorative dentistry.  Time of exposure should be explored in future studies.
As digital dentistry continues to advance, dental educators will continue to incorporate new technology into dental training. Ultimately, haptic dental simulators may ease the transition into the clinic for predoctoral dental students and aid in the improvement of clinical skills for graduate level trainees.