Association between Bolton discrepancy and Angle malocclusions

This study aimed to assess and compare the overall and anterior ratios of tooth size discrepancies in all Angle malocclusion groups. The following null hypothesis (H0) was tested: no difference between tooth size discrepancies (overall and anterior) would be observed among Angle malocclusion groups. The sample comprised of 711 pre-orthodontic treatment study casts of Brazilian patients with a mean age of 17.42 years selected from private practices in Brazil. The casts were divided into 3 groups according to the type of malocclusion: Class I (n = 321), Class II (n = 324), and Class III patients (n = 66). The measurement of the greatest mesiodistal width of the teeth was performed using a centesimal precision digital caliper directly on the study casts, from the distal surface of the left first molar to the distal surface of the right first molar. The overall and anterior ratios between the maxillary and mandibular teeth were evaluated using Bolton’s method. The following statistical tests were applied: chi-square, independent t-test, and one-way ANOVA. Results showed that all Angle malocclusions groups exhibited a ratio compatible with those recommended by Bolton. With respect to the overall and anterior ratios among the malocclusion groups, no statistically significant differences were found. The null hypothesis was accepted because the results showed no differences in the overall and anterior ratios of tooth size discrepancies among different Angle malocclusion groups.

本研究旨在评估并比较所有安氏错𬌗畸形（Angle malocclusion）组的牙量不调全牙比与前牙比。本研究检验了如下无效假设（H0）：不同安氏错𬌗畸形组之间，牙量不调的全牙比与前牙比均无差异。研究样本取自巴西私人诊所，共纳入711例正畸治疗前的研究模型，受试者为巴西患者，平均年龄17.42岁。根据错𬌗畸形类型将模型分为3组：安氏I类（n = 321）、安氏II类（n = 324）与安氏III类（n = 66）。采用百分精度数显游标卡尺直接在研究模型上测量牙齿近远中最大宽度，测量范围从左侧第一磨牙远中面至右侧第一磨牙远中面。采用博尔顿分析法（Bolton’s method）评估上下颌牙量的全牙比与前牙比。本研究采用的统计学检验方法包括卡方检验（chi-square）、独立样本t检验（independent t-test）以及单因素方差分析（one-way ANOVA）。结果显示，所有安氏错𬌗畸形组的牙量比均符合博尔顿推荐的标准。就错𬌗畸形组间的全牙比与前牙比而言，未发现具有统计学意义的差异。由于不同安氏错𬌗畸形组的牙量不调全牙比与前牙比均无差异，因此接受本研究的无效假设。