Impact of Visual Magnification on MB2 Canal Detection in a Laboratory-Based Study Using Standardized 3D-Printed Maxillary Molars

Background: Missed second mesiobuccal second (MB2) canals are a recognized contributor to endodontic failure, and enhanced visualization may facilitate their detection. This study evaluated the influence of magnification devices and operator experience on MB2 detection using anatomically standardized 3D-printed maxillary first molar models. Methods: Fifty-nine endodontists and endodontic residents evaluated anatomically standardized TrueTooth® 3D-printed maxillary first molars incorporating Vertucci Type II and IV configurations. Participants were assigned to naked-eye (NE), dental loupe (DL; 3.5×), or dental operating microscope (DOM) visualization. Access cavity preparation and MB2 canal scouting times were recorded, and MB2 detection was confirmed by insertion of a size-10 K-file. Use of ultrasonic tips and long-shank burs was documented. Statistical analyses included two-way ANOVA for procedural time comparisons, chi-square or Fisher’s exact tests for categorical variables, and logistic regression to evaluate factors associated with MB2 detection (α = 0.05). Results: The overall MB2 detection rate was 49.2%. Detection varied by magnification modality, with rates of 25.0% for naked-eye visualization, 45.0% for dental loupes, and 70.0% for the dental operating microscope. In multivariable analysis using a parsimonious model, DOM use was associated with higher odds of MB2 detection; however, the confidence interval included unity, indicating a borderline association. MB2 detection rates were similar between endodontists and residents (50.0% vs. 47.6%), with no statistically significant difference between groups. Ultrasonic tip use was associated with a higher frequency of scouting-related perforations but did not improve detection. Operators who successfully detected MB2 completed scouting in significantly less time. Conclusions: Under controlled, anatomically standardized laboratory conditions, visual magnification, particularly use of the dental operating microscope, was associated with greater efficiency of MB2 canal detection and shorter scouting times, beyond non-significant trends related to operator experience. Although 3D-printed models do not fully replicate the mechanical and tactile properties of natural dentin, their reproducible anatomy allows reliable assessment of operator- and device-related factors in a controlled setting. Given the simulated environment and the presence of borderline statistical associations, these findings should be interpreted cautiously and should not be directly extrapolated to clinical outcomes without further validation in clinical studies.