Relationship between skeletal Class II and Class III malocclusions with vertical skeletal pattern

ABSTRACT Objective: The purpose of this study was to establish the association between sagittal and vertical skeletal patterns and assess which cephalometric variables contribute to the possibility of developing skeletal Class II or Class III malocclusion. Methods: Cross-sectional study. The sample included pre-treatment lateral cephalogram radiographs from 548 subjects (325 female, 223 male) aged 18 to 66 years. Sagittal skeletal pattern was established by three different classification parameters (ANB angle, Wits and App-Bpp) and vertical skeletal pattern by SN-Mandibular plane angle. Cephalometric variables were measured using Dolphin software (Imaging and Management Solutions, Chatsworth, Calif, USA) by a previously calibrated operator. The statistical analysis was carried out with Chi-square test, ANOVA/Kruskal-Wallis test, and an ordinal multinomial regression model. Results: Evidence of association (p< 0.05) between sagittal and vertical skeletal patterns was found with a greater proportion of hyperdivergent skeletal pattern in Class II malocclusion using three parameters to assess the vertical pattern, and there was more prevalent hypodivergence in Class III malocclusion, considering ANB and App-Bpp measurements. Subjects with hyperdivergent skeletal pattern (odds ratio [OR]=1.85-3.65), maxillary prognathism (OR=2.67-24.88) and mandibular retrognathism (OR=2.57-22.65) had a significantly (p< 0.05) greater chance of developing skeletal Class II malocclusion. Meanwhile, subjects with maxillary retrognathism (OR=2.76-100.59) and mandibular prognathism (OR=5.92-21.50) had a significantly (p< 0.05) greater chance of developing skeletal Class III malocclusion. Conclusions: A relationship was found between Class II and Class III malocclusion with the vertical skeletal pattern. There is a tendency toward skeletal compensation with both vertical and sagittal malocclusions.

摘要 研究目的：本研究旨在明确矢状向与垂直向骨骼型之间的关联，并评估哪些头影测量（cephalometric）指标可用于预测骨性Ⅱ类或Ⅲ类错𬌗畸形的发生风险。研究方法：本研究为横断面研究，纳入548名18~66岁受试者的治疗前头颅侧位X线片（女性325名，男性223名）。矢状向骨骼型通过三项不同分类参数判定：ANB角、Wits值及App-Bpp值；垂直向骨骼型通过SN-下颌平面角判定。头影测量指标由经过校准的操作者使用Dolphin软件（Imaging and Management Solutions，美国加利福尼亚州查茨沃斯市影像与管理解决方案公司）完成测量。统计学分析采用卡方检验、方差分析（ANOVA）/Kruskal-Wallis检验及有序多项回归模型。研究结果：结果显示矢状向与垂直向骨骼型存在显著关联（p<0.05）：采用三项垂直向评估参数时，Ⅱ类错𬌗患者中高角骨骼型占比更高；结合ANB角与App-Bpp值的测量结果，Ⅲ类错𬌗患者中低角骨骼型更为常见。具有高角骨骼型（优势比（odds ratio, OR）=1.85~3.65）、上颌前突（OR=2.67~24.88）及下颌后缩（OR=2.57~22.65）的受试者，发生骨性Ⅱ类错𬌗的风险显著升高（p<0.05）。与此同时，上颌后缩（OR=2.76~100.59）及下颌前突（OR=5.92~21.50）的受试者，发生骨性Ⅲ类错𬌗的风险显著升高（p<0.05）。研究结论：本研究发现骨性Ⅱ类、Ⅲ类错𬌗畸形与垂直向骨骼型存在关联，垂直向与矢状向错𬌗畸形均存在骨骼代偿倾向。