Comparison of maxillomandibular asymmetries in adult patients presenting different sagittal jaw relationships

ABSTRACT Objective: The present study aims at using cone beam computed tomography (CBCT) to analyze the maxillomandibular characteristics present in adults with mandibular asymmetries and different sagittal jaw relationships. Methods: 360 patients were selected and divided into three groups (Class I, Class II, and Class III), with 120 individuals per group. The groups were then subdivided according to the intensity of lateral deviation of the gnathion point, into: 1) relative symmetry, 2) moderate asymmetry, and 3) severe asymmetry. Three planes of reference were established in the CBCT images and several measurements were taken to compare the bilateral skeletal differences between the intensities of asymmetry for the different sagittal jaw relationships. Results: When the groups were compared by the intensity of asymmetry, significant differences among patients with relative symmetry and moderate to severe asymmetry were found. This was especially noticed for severe asymmetry, suggesting that the deviation of the chin did not constitute the only morphological alteration for these patients, especially because a series of measurements showed significant bilateral differences. When comparing sagittal jaw relationships, the only significant finding was the vertical positioning of the gonion between Class II and III patients with severe asymmetry. Conclusions: When comparing the three sagittal jaw relationships with the same intensity of asymmetry, most maxillofacial aspects were quite similar. The only difference was found for patients with severe asymmetry, as the individuals with Class II showed greater bilateral difference in the vertical positioning of the gonion, when compared to patients with Class III.

摘要 目的：本研究拟采用锥形束计算机断层扫描（cone beam computed tomography, CBCT），分析伴下颌偏斜且存在不同矢状向颌骨关系的成年患者的上下颌骨特征。方法：选取360例患者，分为安氏Ⅰ类（Class I）、安氏Ⅱ类（Class II）与安氏Ⅲ类（Class III）共3组，每组120例。随后根据颏点（gnathion point）的侧偏程度，将每组进一步细分为：1）相对对称组；2）中度偏斜组；3）重度偏斜组。在CBCT影像中建立3个参考平面，并开展多项测量，以对比不同矢状向颌骨关系下，不同偏斜程度的双侧骨骼差异。结果：按偏斜程度进行组间比较时，相对对称组与中度、重度偏斜组患者间存在显著差异，其中重度偏斜组的差异尤为显著。这提示颏部偏斜并非此类患者唯一的形态学改变，因多项测量指标均显示存在显著的双侧骨骼差异。在对比不同矢状向颌骨关系时，唯一具有统计学意义的发现为：伴重度偏斜的安氏Ⅱ类与安氏Ⅲ类患者，其下颌角点（gonion）的垂直位置存在显著差异。结论：对偏斜程度相同的三类矢状向颌骨关系患者进行比较时，多数颌面特征无显著差异。仅在重度偏斜患者中存在差异：与安氏Ⅲ类患者相比，安氏Ⅱ类患者的下颌角点垂直位置的双侧差异更为显著。