Retrospective CBCT-based anatomical assessment of mandibular first and second molars: a cross-sectional study with...

Immediate implant placement in mandibular molar sockets can shorten treatment and reduce the number of surgical interventions, but the anatomy of the posterior mandible may limit implant positioning and increase surgical risk. This study evaluated six cone-beam computed tomography (CBCT)-derived anatomical parameters in mandibular first and second molars. This retrospective cross-sectional study included 25 CBCT scans from 25 adults, providing 100 molar sites (#36, #37, #46, and #47). Buccal bone thickness, crestal bone width, crestal bone height loss, vertical bone height, root apex-to-inferior alveolar canal (IAC) distance, and interradicular distance were measured. The data were analyzed using 2 × 2 repeated-measures analyses of variance with molar type and side as within-subject factors. Pairwise comparisons were Holm-adjusted. Inter-examiner reliability was evaluated using intraclass correlation coefficients. Inter-examiner reliability was excellent for all parameters (ICC range, 0.907-0.988). Second molars had greater buccal bone thickness (mean difference, 0.352 mm; 95% CI, 0.186-0.518; p < 0.001) and crestal bone width (0.786 mm; 95% CI, 0.367-1.205; p = 0.001). First molars had greater vertical bone height (1.724 mm; 95% CI, 1.050-2.398; p < 0.001), root apex-to-IAC distance (0.802 mm; 95% CI, 0.261-1.343; p = 0.005), and interradicular distance (0.924 mm; 95% CI, 0.655-1.193; p < 0.001). Crestal bone height loss did not differ significantly by molar type. Mandibular first and second molars demonstrated distinct CBCT-derived anatomical patterns in this selected dentate sample. These measurements may be informative for preoperative anatomical assessment. Their value for selecting implant dimensions or osteotomy positions, or predicting clinical outcomes, was not evaluated.