Morphological Variations of the Posterior Mandible: Proposing a Classification for Ridge Morphology Based on...

This study sought to assess the morphological variations of the posterior mandible and propose a classification for ridge morphology based on cone-beam computed tomography (CBCT) data. This retrospective, cross-sectional study evaluated 130 CBCT scans of patients with edentulous mandibles. Qualitative variables including lingual and crestal concavity, vertical, horizontal and angular limitations, and ridge morphology were assessed at 631 sites on CBCT scans of 87 males and 43 females. A classification for ridge morphology in the posterior mandible was proposed based on the collected data. The kappa coefficient was calculated to assess the intra-observer agreement, and data were analyzed using the chi-square test and Pearson's correlation test. The frequency of lingual concavity increased from the anterior towards the posterior region relative to the mental foramen (P < 0.05). The maximum frequency of lingual concavity (11.1%) was noted at 21 mm distance from the mental foramen while its minimum frequency (4.1%) was noted at 5 mm from the mental foramen (P < 0.05). Ridge morphology, defined as ridge angulation < 15°, no lingual or crestal concavity, no limitation in width, and 8-10 mm height, had the highest frequency. Its suggested treatment plan included a 10-mm implant without width limitation or severe angulation. The majority of common morphologies had no width limitation with ridge angulation < 15°. Height limitation was only present in two of them, which can be resolved by placement of a short implant or ridge augmentation.