Computed tomography evaluation of mandibular incisor bony support in untreated patients

Introduction: In this study, we aimed to verify, via computed volumetric tomography, a correlation between the morphology of the mandibular symphysis and the various facial types. Methods: From a sample of 148 digital volumetric tomographs, the subjects were classified as either short face (25 subjects), normal face (27 subjects), or long face (28 subjects) according to the average values of their Frankfort-mandibular plane angle. The 80 healthy subjects were between 12 and 40 years of age. Tomography was carried out using NewTom 3G volume scanner (QRsr1, Verona, Italy). The following parameters were measured on the sections corresponding to the 4 mandibular incisors: height, thickness, and area of the entire symphysis; height, thickness, and area of the cancellous bone of the symphysis; distance of the vestibular and lingual cortices from the apices of the 4 incisors; and possible inclination of each mandibular incisor, expressed in degrees. The F test or analysis of variance (ANOVA) and the Tukey HSD Test were subsequently used. Results: The total thickness of the symphysis was greater in the short-face subjects than in the long-face subjects. No statistically significant differences in the total and cancellous areas of the symphysis were found between the 3 facial types. In all 3 groups, the total and cancellous heights and areas were greater at the central incisors than at the lateral incisors. Conclusions: There is a statistically significant relationship between facial type and the total thickness of the mandibular symphysis. � 2010 by the American Association of Orthodontists.