CBCT evaluation of adolescent mandibular morphology in different classifications of facial type

The goal of this study is to use the improved imaging capability of cone-beam computerized tomography (CBCT) to investigate the relationship between vertical facial patterns and mandibular tooth-alveolar morphology in the adolescent population. Pre-treatment orthodontic records were obtained from the UNLV School of Dental Medicine archival dental records. One hundred and seventy three patients (72 males, 101 females) between the ages of 12 and 18 years were included in this study. Among these patients, 61 displayed the vertical growth pattern, 30 displayed the horizontal growth pattern, and 82 displayed the average growth pattern. The samples were categorized into 4 age groups for analysis: Group 1 (age 12 to 18), Group 2 (age 12 to 13), Group 3 (age 14 to 15), and Group 4 (age 16 to 18). Cross sectional slices of the mandible were developed from the cone-beam scans to evaluate cortical bone thickness, alveolar bone height, alveolar bone width, tooth inclination, and alveolar bone inclination at four locations. Each cross section was measured at 10 sites, which included 5 cortical bone thickness, 1 height, 2 width, 1 tooth inclination, and 1 bone inclination measurements. An analysis of variance (ANOVA) with post-hoc Scheffe statistical analysis was used with a significance level of p < 0.05. Results of this study indicated that in all age groups the hyperdivergent facial type generally had the thinnest cortical bone, the highest alveolar bone height at the anterior region of the mandible, and the narrowest alveolar bone width compared with the other two facial types. The hyperdivergent facial type had more upright lower incisor and more lingually inclined posterior teeth than the other facial types. The alveolar bone inclination generally followed the same angulation tendency as the tooth inclination. The results of this study indicates statistically significant differences exist in cortical bone thickness, alveolar bone height, alveolar bone width, tooth inclination, and bone inclination measurements between the various facial types in the adolescent population.