Virtual Reality-Based Mirror Guidance for Indirect Vision Training in Minimally Invasive Endodontic Access Cavity Preparation Among Dental Students: Randomized Controlled Crossover Trial.

Abstract

Background: Minimally invasive endodontics requires precise visualization to preserve tooth structure, often relying on indirect vision with a dental mirror-a challenging skill for dental students. Although virtual reality (VR) simulators provide immersive environments for dental training, most existing systems primarily focus on procedural simulation and haptic feedback, with limited capabilities for real-time mirror positioning and indirect visual guidance.

Objective: The aim of this study was to evaluate verbal, visual, and haptic VR-based mirror guidance for indirect vision during minimally invasive endodontic access cavity preparation.

Methods: Eligible fourth-year preclinical dental students were recruited through institutional email invitations and public announcements. A randomized controlled crossover trial was conducted with 30 participants, who completed all VR sessions in a simulation laboratory under direct investigator supervision to ensure standardized implementation of the training protocol. Participants performed simulated maxillary first molar access cavity preparations under 4 VR mirror guidance conditions-verbal guidance, visual guidance, haptic guidance, and no guidance-following a randomized 4 × 4 Latin square sequence with a 48-hour washout period between sessions. The primary outcome was outcome error score. Exploratory secondary outcomes included operating area visibility, operating area obstruction, operator posture error, task completion time, and Virtual Reality System Usability Questionnaire score. Outcomes were analyzed using linear mixed-effects models accounting for the crossover design. Estimated marginal mean differences (MDs) with 95% CIs and partial eta-squared (ηp²) effect sizes were reported, with Bonferroni-adjusted pairwise comparisons used to account for multiple comparisons.

Results: Guidance modality significantly affected the primary outcome, outcome error score (F_3,84=20.34; P<.001; ηp²=0.421). Compared with no guidance, outcome error scores were significantly lower with verbal (MD -0.50, 95% CI -0.76 to -0.24), visual (MD -0.68, 95% CI -0.94 to -0.42), and haptic guidance (MD -0.63, 95% CI -0.89 to -0.37; all adjusted P<.001). Guidance modality also significantly affected operating area visibility (F_3,84=12.31; P<.001; ηp²=0.305). Compared with no guidance, visibility duration was significantly greater with verbal (MD 37.79, 95% CI 11.15-64.43 seconds; adjusted P=.001), visual (MD 59.15, 95% CI 32.51-85.79 seconds; adjusted P<.001), and haptic guidance (MD 31.52, 95% CI 4.90-58.15 seconds; adjusted P=.01). No significant differences were detected for operating area obstruction, operator posture error, task completion time, or usability.

Conclusions: VR-based mirror guidance improved the outcome error score and increased operating area visibility during minimally invasive endodontic access cavity preparation. Verbal, visual, and haptic guidance resulted in fewer outcome errors and greater operating area visibility than no guidance, while no significant differences were detected in other performance measures or usability. These findings demonstrate the potential of diverse feedback modalities to provide effective guidance for indirect vision and inform future development of adaptive VR training systems using 1 or more modalities to suit learner needs.

Trial registration: Thai Clinical Trials Registry TCTR20260126008; https://www.thaiclinicaltrials.org/show/TCTR20260126008.