Clinical and microscopic analysis of the incidence of a fourth canal and its trajectory in the maxillary first molar

Objective: This study evaluated the incidence of a fourth canal in the mesiobuccal root of maxillary first molars, investigating the importance of microscopic analysis of its trajectory in relation to the mesiobuccal canal. Methods: The analysis was performed of 65 randomly extracted maxillary first molars, with previous endodontic coronal opening, obtained from the Univille University tooth bank. The teeth were numbered and kept hydrated in distilled water. Compensatory wear was performed to widen the cavity in the mesiobuccal direction, foreseeing the presence of the mesiopalatal canal. A dental microscope was used to confirm presence of a groove (or “fin”) and orifices in canals in the mesiobuccal root, and evaluate the presence of anastomosis between the root canals, following the modified method of Stropko1. Results: The incidence of the fourth canal (52.3%) was higher when microscopically observed, than clinically observed (29.3%). The results achieved by the modified method of Stropko demonstrated that most root canals (67.6%) presented union. Conclusion: There was higher incidence of the mesiopalatal canal (52.3%) observed in the microscopic analysis when compared with that observed in the clinical analysis (29.2%). The drying method allowed confirmation of union between canals in 67.6% of teeth. The combination of information achieved by radiographic examination of the trajectories of the mesiobuccal root and microscopic evaluation by the drying method allows the professional to gain better knowledge of the tooth under treatment, providing.