Diagnostic Performance of Magnification and Ultrasonic Troughing in Detecting Second Mesiobuccal Canals: A Two-Factor...

Background The detection of the second mesiobuccal (MB2) canal in maxillary first molars remains a major challenge in endodontic practice because of complex root canal anatomy and frequent calcification. This controlled experimental study evaluated the diagnostic performance of magnification and ultrasonic troughing, applied alone or in combination, for MB2 canal detection. Methods A total of 208 extracted human maxillary first molars were randomly allocated into four groups (n = 52 each): direct visual method (DVM) without troughing, DVM with troughing, dental operating microscope (DOM) without troughing, and DOM with troughing. A two-factor experimental design was used to assess the independent and combined effects of magnification and ultrasonic troughing. After standardized access preparation, MB2 detection was evaluated clinically and verified by root cross sections. Detection rates were compared using chi-square tests with post hoc pairwise comparisons, and multivariable binary logistic regression was performed. Results MB2 canal detection rates differed significantly among groups (p < 0.001). The lowest detection rate was observed with the DVM without troughing (21/52, 40.4%), whereas the highest rate was observed with the DOM with troughing (46/52, 88.5%). Intermediate detection rates were observed with troughing alone (30/52, 57.7%) and magnification alone (35/52, 67.3%). Magnification (OR = 3.90, p < 0.001) and ultrasonic troughing (OR = 2.54, p = 0.003) were independently associated with improved MB2 detection. Conclusions Magnification and ultrasonic troughing independently improved MB2 canal detection in maxillary first molars, with the highest diagnostic performance achieved when both techniques were combined. These findings may improve clinical decision-making during the detection of MB2 canals in routine endodontic practice.