University of Detroit Mercy, Graduate Orthodontics, School of Dentistry, Detroit, MI, USA.
University of Detroit Mercy, Graduate Orthodontics, School of Dentistry, Detroit, MI, USA.
Int Orthod. 2021 Mar;19(1):51-59. doi: 10.1016/j.ortho.2020.11.003. Epub 2020 Dec 10.
The objective of this study was to investigate the effects of maxillary central incisor (U1) inclination changes on alveolar bone and root length in the 20 Class II division 1 and 20 Class II division 2 (CII div1, CII div2) Caucasian adolescents treated without extraction.
Forty U1s from each group were assessed for root length and alveolar variables at the crestal, mid-root, and apical levels using sagittal sections obtained from CBCT images pre- and post-treatment. Mixed MANOVAs, Repeated measures MANOVAs, Pearson correlations, and regression analyses were performed.
The facial bone height did not change significantly after an average of 15 degrees of proclination in the CII div2 group, whereas a statistically significant decrease in the palatal bone height was noted. However, in the CII div1 group, a statistically significant reduction in the facial and palatal bone height was observed with mild crown retroclination. Both groups had a significant decrease in total bone thickness at all levels, more decrease in the CII div2 group after treatment. No statistically significant difference in root length was observed between the groups during treatment.
The findings support that the flaring of retroclined U1s as a process for normalizing U1 inclination did not harm the facial alveolar bone height in the CII div2 non-extraction treatment. Crown proclination itself was not correlated to the amount of root resorption in Class II div1&2 non-extraction treatments in adolescents.
本研究旨在探讨上颌中切牙（U1）倾斜度变化对未经拔牙治疗的 20 例安氏Ⅱ类 1 分类（CII div1）和 20 例安氏Ⅱ类 2 分类（CII div2）白种青少年牙槽骨和牙根长度的影响。
在治疗前后的 CBCT 图像矢状切片上，分别对每组的 40 颗 U1 进行根长和牙槽变量的评估，包括牙槽嵴顶、根中、根尖水平。采用混合 MANOVA、重复测量 MANOVA、Pearson 相关分析和回归分析进行统计分析。
CII div2 组平均前倾 15 度后，面骨高度无明显变化，而腭骨高度明显下降。然而，在 CII div1 组，随着轻度冠倾后，面骨和腭骨高度均显著下降。两组在所有水平的总骨厚度均显著减少，CII div2 组治疗后减少更为明显。治疗过程中两组的牙根长度均无显著差异。
研究结果支持，作为正常化 U1 倾斜度的过程，将后倾的 U1 展开，不会损害 CII div2 非拔牙治疗中面牙槽骨高度。在青少年非拔牙治疗的安氏Ⅱ类 1 分类和 2 分类中，冠倾本身与根吸收量无关。
