Quantitative 3D Assessment of Iatrogenic Damage During Class II Cavity Preparations by Dental Students

The aim of this study was to visually and quantitatively determine the extent of iatrogenic damage on the approximal surface of teeth caused by dental students during Class II cavity preparation, and to develop and apply a 3D modeling workflow for the precise quantitative assessment of such damage.

A total of 101 patients (mean age:34.6) with Class II caries and intact adjacent tooth surfaces participated in the study. Teeth requiring endodontic treatment and adjacent teeth with caries were excluded. Cavity preparations were performed by third-, fourth-, and fifth-year undergraduate dental students under supervisor approval. Alginate impressions were taken, and Type IV dental stone models were produced. Damage assessment was performed using stereomicroscopy by 2 independent calibrated examiners, followed by quantitative 3D analysis using intraoral scanning (3Shape TRIOS 3) and Rhinoceros 8 CAD software. Damage was assessed in terms of morphology, buccolingual and cervico-occlusal width, and surface area. Statistical analysis included Chi-square tests, Mann-Whitney U tests, and Spearman's correlation (P < .05).

Iatrogenic damage was observed on 90.1% of adjacent teeth. There were no significant differences in damage morphology among student levels (P = .960), and also no significant differences in buccolingual width, cervico-occlusal width, or surface area between different training levels (P > .05). The average buccolingual width of damages was 2.40 ± 1.42 mm, the cervico-occlusal width was 1.77 ± 1.03 mm, and surface area was 4.66 ± 4.35 mm² of damages. X morphology (a combination of multiple defects) showed significantly higher than other morphologies (P < .05). Strong positive correlations existed between damage widths and surface area (r = 0.906 and r = 0.0872, both P < .001).

This study demonstrates that 3D modeling provides objective quantification of iatrogenic damage during dental training. The high prevalence of damage (90.1%) indicates the need for enhanced protective protocols, improved visual access techniques, and integration of 3D assessment methods in dental curricula. The strong correlation between damage dimensions suggests that width measurements can predict total damage extent, enabling early intervention strategies.

The use of 3D modeling provides an advanced quantitative assessment of iatrogenic damage, offering potential for improved clinical training and technique refinement. The strong positive correlations between damage width and surface area (r = 0.906 and r = 0.872) have critical clinical implications for long-term adjacent tooth prognosis, increased bacterial retention, secondary caries risk and restoration failure. The significantly greater dimensions of X morphology damage translate directly to compromised enamel integrity, potentially requiring prophylactic restoration or enhanced preventive protocols.