Morphological Evaluation of Second Maxillary Molars with Fused Root by Cone-Beam Computed Tomography

The most important cause of failed root canal treatment is poor preparation and obturation of canals, as well as untreated canals. Therefore, understanding the anatomy of the root canal system is the key to the success of root canal treatment. The present study aimed to investigate the morphology of the root canal system of maxillary second molars with fused roots.

In this in vitro study, 50 maxillary second molars with fused roots were mounted, and Cone-beam computed tomography (CBCT) images were obtained. The samples were evaluated for mesiobuccal root canal system based on Vertucci classification, presence of second and third mesiobuccal canals, presence of isthmus between canals, C-shaped anatomy, root connection status, and minimum dentin thickness in the middle third. The data were analyzed using Kruskal-Wallis, Mann-Whitney, and Fisher's exact tests, and a p-value of 0.05 was considered statistically significant.

The most common anatomy was type 1 (42%), followed by types 4 and 6 (16%) and type 2 (14%). The second mesiobuccal and third mesiobuccal canals were observed in 58% and 4% of cases. Isthmus was observed between 11(22%) canals. Moreover, 3 (6%) teeth had C-shaped anatomy. The most common root connection was related to palatal and distobuccal root connection (42%), followed by the connection of all three roots (18%). The minimum dentin thickness in the middle third of the root was obtained at 0.64 mm.

As evidenced by the results of the present study, maxillary second molars with fused roots have a complex root canal system. Furthermore, there was no relationship between root connection and the presence or absence of the second mesiobuccal canal.