Correlation between the presence of MB2 in maxillary first molars and distolingual canals or severely curved root canals in mandibular first molars

BACKGROUND: This study aimed to investigate the prevalence of the second mesiobuccal root canal (MB2) in maxillary first molars (MaxFMs) and the severely curved distolingual canals (SC) in mandibular first molars (ManFMs) within a Shanghai population, and to evaluate the correlation between their occurrences. MATERIALS AND METHODS: A total of 1104 MaxFMs and 1104 ManFMs were ana- lyzed using CBCT images retrieved from the CBCT database of patients in Huashan Hospital affiliated to Fudan University, Shanghai. The root canal morphology was recorded, and the correlation between the prevalence of specific canal types was analyzed using Stata 13.0 software. RESULTS: The prevalence of MB2 in the 1104 MaxFMs and of distolingual canals (DLs) in the 1104 ManFMs was 41.85% and 40.85%, respectively, with Vertucci Type IV being the most frequent configuration for both. The prevalence of SC was 14.49%. In the MB2-present group, the prevalence of DLs in ipsilateral ManFMs was 50.43%, while that of SC was 11.26%. Conversely, in the MB2-absent group, the prevalence of DLs in ManFMs was significantly lower (33.96%), whereas the prevalence of SC was significantly higher (16.82%). The presence of MB2 in MaxFMs was positively correlated with DLs in ManFMs (r = 0.61), but negatively correlated with the occurrence of SC (r = -0.07). These findings indicate that SCs are more likely to occur in ManFMs when MB2 is absent in MaxFMs. At the individual level, patients with MB2 were more likely to possess DLs (p = 0.02), indicating that complex root canal morphologies tend to co-occur within the same individual. CONCLUSIONS: In a Shanghai-based patient population, the prevalence of MB2 in MaxFMs was positively correlated with the occurrence of DLs in ManFMs. However, no such correlation was observed with the presence of SC.