Morphology and classification of the second mesiobuccal canal in maxillary first molars: a cone-beam computed tomography analysis in a Chinese population

Abstract Background Understanding the tooth anatomy is crucial for ensuring effective endodontic treatment. This study investigated the root canal morphology of the second mesiobuccal (MB2) canal in maxillary first molars (MFMs) in a Chinese population using cone-beam computed tomography (CBCT). Methods This study evaluated 486 MFMs with MB2 canals from 285 participants undergoing CBCT examination and determined the Vertucci’s classification and position of the MB2 canal orifice. The prevalence of the MB2 canal was correlated with the sex, age, and tooth side. The correlations between the prevalence of the MB2 canal and sex and tooth side were assessed using the Fisher's exact test. The chi-square test was used for evaluating the correlation between the prevalence of the MB2 canal and age. Results The number of type II, III, IV, V, VI, VII, and other root canals in the MFMs was 30.9%, 0.6%, 65.0%, 1.2%, 1.2%, 0.4%, and 0.6%, respectively. Among the 201 cases with bilateral inclusion, 87.6% showed consistent canal configuration. Results of the first clear apparent position (FCAP) of the MB2 canals showed that 434, 44, and 3 teeth had FCAP at the upper, middle, and bottom one-third of the root, respectively. The FCAPs of the MB2 canal in the MFMs with types II, IV, and VI, as well as types III and V canals showed significant differences ( p <0.05). The horizontal distance between the MB1 and MB2 canal orifices in the type II canals of MFMs was significantly lesser than those in the type IV canals of MFMs ( p < 0.01). The longitudinal distance between the pulp chamber floor plane and MB2 canal orifice significantly correlated with age ( p < 0.05). Conclusions The morphology of the mesiobuccal root canal in the MFMs is complex. Complete understanding of the anatomical morphology of the root canal combined with the CBCT and dental operating microscope is necessary for the accurate detection of the MB2 canal and consequently improved success rate of root canal treatment. Our study findings can help endodontists improve endodontic treatment outcomes.