Root Canal Morphometry of the Maxillary and Mandibular Permanent Second Molars Among Mongolians: A Retrospective Study

Introduction The overall success of root canal treatment depends on the dentist's knowledge of the anatomy of the root canal system, which is complex and varies in shape, making it difficult to remove organic tissue and reduce the microbial load - especially in the permanent second molar. A C-shaped canal configuration is most commonly found in the mandibular second molar. Therefore, careful radiographic evaluation may be helpful in diagnosing the root canal configuration prior to treatment. This study aims to examine the root canal morphometry of the maxillary and mandibular permanent second molars. Methods The retrospective study was conducted using CBCT images taken in the Department of Oral and Maxillofacial Radiology, Central Dental Hospital, Mongolian National University of Medical Sciences (MNUMS), Ulaanbaatar, Mongolia, after receiving ethical approval from the MNUMS Research Council (2024/3-02). CBCT images were selected according to the inclusion criteria and analyzed using OnDemand3D software (Cybermed Inc., Seoul, South Korea). The root canal morphometric parameters of the permanent second molar included the number of roots, the number of root canals, the root canal configuration based on Vertucci's classification, and C-shaped canals based on Melton's classification. The prevalence of C-shaped canal classifications was calculated across all selected cases. Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 27 (Released 2019; IBM Corp., Armonk, NY, USA). Results Among the 96 CBCT images of individuals aged 15-57 who met the inclusion criteria for this study, a total of 332 permanent second molars - 174 maxillary and 158 mandibular - were analyzed. When we determined the number of roots and root canals of the permanent second molars, the findings revealed that 83 (25%) had a single-rooted tooth, 143 (43%) had two-rooted, and 105 (32%) had three-rooted teeth. Regarding the number of root canals, 21 (6.4%) of them had one, 103 (31.3%) had two, 191 (57.5%) had three, and 16 (4.8%) had four canals (p < 0.05). According to Vertucci's classification, the root canal configuration of the maxillary second molars was as follows: Type I (84.2%), Type II (1.9%), Type III (0.2%), Type IV (11.3%), Type V (1.4%), and Type VIII (1%). The configuration for mandibular second molars included Type I (59.1%), Type II (4.6%), Type III (2.8%), Type IV (25.8%), Type V (5.4%), and Type VIII (2.3%). The prevalence of C-shaped canals in permanent second molars, classified using Melton's system, was 11.4% in the maxilla and 29.1% in the mandible. According to the classification of C-shaped canal types, C1 type was found in 55%, C2 type in 18%, C3 type in 15%, and C4 type in 12% of cases. Conclusion Mongolians have mostly three-rooted teeth with three canals in the maxillary and two-rooted teeth with three canals in the mandibular second molars. Vertucci's Type I canal configuration was predominant, and C-shaped canals were more frequently observed in the mandible than in the maxilla.