Biometric analysis of apical surgery-related anatomy of mandibular first molars: a cone-beam computed tomography study in a Mongoloid population

Objective To evaluate the apical surgery-related anatomy of two-rooted and three-rooted mandibular first molars (MFMs) in a Mongoloid population. Methods A total of 502 cone-beam computed tomographic images were used to evaluate the root configuration, the distance from the buccal bone to each root, root dimensions, and the complete root resection distance at the resection level for roots of MFMs. Results The prevalence of two-rooted and three-rooted MFMs was 85.1% and 14.9%, respectively. At the resection level, the distance from the buccal bone to the mesial and distal roots of two-rooted MFMs was 2.24 and 3.15 mm, respectively, while the distance was 2.44, 2.01, and 8.55 mm for the mesial, distobuccal, and distolingual roots of three-rooted MFMs, respectively. The distance from the buccal bone to each root was longer in men than in women. The largest distance for complete root resection was detected for the distal root in two-rooted MFMs and for the distolingual root in three-rooted MFMs. Conclusions The prevalence of three-rooted MFMs is common in the Mongoloid population. The distance from the buccal bone to root apex differs according to root configurations and sex. Surgical access to the distolingual root is difficult because of the long access distance.