OBJECTIVEThe purpose of this study is to assess the height and width of mandibular cross-sections and the thickness of cortical bone for young females in different vertical skeletal pattern by cone beam CT (CBCT) and determine the characteristics and differences of mandible among different vertical skeletal patterns.

METHODSA total of 64 females, aged from 19 to 40 years old, were enrolled from Department of Orthodontics of School of Stomatology of Shandong University. After examination with CBCT scan, they were divided into 3 groups according to the vertical skeletal patterns (14 in low-angle group, 31 in average-angle group and 19 in high-angle group). The mandibular morphology was evaluated according to the height and width of the mandibular cross-sections and the thickness of cortices. SPSS 16.0 was used to analyze the characteristics and differences of mandible among different vertical skeletal patterns.

RESULTSThe height of symphysis in the high-angle group was higher than that in the low-angle group, but the height of molars in the low-angle group was higher than that in the high-angle group (P<0.05). In the regions of anterior teeth and premolars, the width of upper one third of the mandibular cross-sections in the low-angle group was significantly larger than those in the high-angle group, while in the symphysis and lateral incisors regions, the width of lower one third of the mandibular cross-sections in the low-angle group was larger than those in the high-angle group (P<0.05). Except of the region of premolars, the cortical thickness of base in the low-angle group was significant thicker than those in the high-angle group (P<0.05). In the regions of canine, premolar and molar, the cortical thickness of buccal upper one third in the low-group was thicker than those in the high-angle group, but in the regions of canine and the second molar, the cortical thickness of buccal lower one third in the low-angle group was thi- cker than those in the high-angle group (P<0.05). In the regions of the symphysis, the cortical thickness of lingual lower one third in the low-angle group was thicker than those in the high-angle group (P<0.05), but in the regions of premolar and molar of lingual upper one third in the low-angle group was thicker than those in the high-angle group (P<0.05).

CONCLUSIONThe height and width of the cross-sections of the body of mandible differed more than thickness of cortical bone among the three different vertical skeletal patterns. The height of cross-sections decreases gradually from the anterior region to the posterior region in three groups. The width of cross-sections in the low-group is thicker than those in other two groups. The thickness of cortical bones decreases successively from low, average to high angle group.