2020 年 11 巻 2 号 p. 98-102
Aims: Since the root canal system of the molars is particularly complex, the success of root canal treatment (RCT) depends on knowledge of its morphology. A distolingual root (DLR), which is also called radix entomolaris1, is a known type of mandibular first molar; however, its incidence and the prevalence of its treatment have not been elucidated in the Japanese population. The purpose of this study was to determine the DLR incidence in mandibular first molars and the prevalence of RCT in mandibular first molars in the Japanese population on cone-beam computed tomography (CBCT). Material and Methods: A total of 150 patients (male: 53, female: 97; age range: 11-85 years) who underwent CBCT examinations at our hospital between November 2019 and February 2020 were included in the study. Images that captured mandibular first molars (n=171) were continuously extracted. The number of three-rooted mandibular first molars with a separate DLR, history of RCT, and presence of radiolucency at the apex were examined to analyze DLR incidence and the prevalence of RCT. Result: The incidence of DLR was 30.4% (male: 30.5%, female: 30.4%) in this patient cohort. A history of RCT was identified in 34.5% of all teeth; of which 24.6% were characterized by radiolucency at the apex. Of the 59 teeth with a history of RCT, 71.2% were treated unsuccessfully, as characterized by the presence of an apical lesion. More specifically, failure of RCT was observed in 47.5% of mesiobuccal (MB) roots, 50.9% of mesiolingual (ML) roots, 50.9% of distal (D) or distobuccal (DB) roots, and 70.0% of DLR alone. Conclusions: The results of the present study show that the incidence of DLR in mandibular first permanent molars on CBCT in a Japanese population was 30.4%. The rate of RCT failure characterized by radiolucency at the apex was 71.2%; specifically, failure rates for MB, ML, D or DB, and DLR alone were 47.5%, 50.9%, 50.9%, and 70.0%, respectively.
