Variations in corpus and ramus measurements based on gonial angles in adult complete dentate mandibles

This study aimed to reveal differences in the mandibular corpus and ramus measurements, volume (VOM), and gross weight of the mandible (GWOM) between the low and high gonial angles (L-GA and H-GA, respectively) in adult mandibles, and to evaluate the correlations between GAs and the measurement variables. Twenty-nine dried adult human complete dentate mandibles (L-GA ≤ 120°: 13 mandibles; H-GA: 125° ≥ GA: 16 mandibles) were measured using a lateral radiograph image-processing system, digital Vernier calipers, and an electric balance. The total length of the mandible (TLOM), corpus length (mental foramen– gonion [MeF’-Go’], mental foramen–mandibular foramen [MeF’-MaF’], and mandibular foramen–gonion [MaF’-Go’]), inter-ramus (bicondylar, bicoronion, and bigonion) widths (BiCoW, BiCorW, and BiGoW), GA width (GAW), condylar perpendicular height (CPH), the VOM, and GWOM were measured. Data were assessed using the exact binomial test, Mann–Whitney U test and Pearson’s correlation coefficient test. The MeF’- Go’ and MaF’-Go’, three inter-ramus widths, GAW, CPH, VOM, and GWOM in the L-GA group were significantly larger than those in the H-GA group. Significant negative correlations were found between GA size and multiple variables other than TLOM and BiCorW. Therefore, GA size was closely related to the enlarged morphometric dimensions of both the GA and the mandibular ramus in the posterior region of the mandibular corpus, as well as the volume and weight of the mandible, but it was not related to TLOM. These results indicate that the evaluation of GA size is useful for strategic dental treatment.