Introduction: This study was designed to determine the prevalence of the second mesiovestibular canal (MB2), in maxillary first molars using the analysis of cone-beam tomography (CBCT) images.

Methods: A total of 1,173 tomographs were analyzed, of which 819 were considered valid, considering the following exclusion criteria: images showing internal or external root resorptions, canal calcification, full-coverage restorations, metallic restorations, and crowns, to avoid errors in the analysis. Before analysis, training, and calibration were conducted to detect the presence of the MB2 canal and the Vertucci classification.

Results: After tomographic analysis, the prevalence of the MB2 canal was 73%. According to Vertucci's classification, type II was the most frequent (51.3%), followed by type IV (19.2%). Types III, V, and VI showed low proportions (0.4%, 0.7%, and 1.5%, respectively). The prevalence of MB2 was (77.6%) in men and (70.3%) in women. Regarding age, MB2 was most common in the young group (89.7%), followed by individuals aged 31-45 years (80.9%), and was least common in those older than 46 years (65.9%). Statistical results highlight the importance of carefully examining the MB2 canal in all patients, without limitations based on criteria such as gender or age.

Conclusions: The use of cone-beam computed tomography (CBCT) as a diagnostic tool is of great importance. CBCT provides essential clinical information for endodontic treatment.