上颌前方牵引对恒牙早期骨性Ⅲ类错[牙合]上、下颌骨宽度影响的三维模拟分析

The influence of three-dimensional maxillary protraction simulation on dental and basal arch width coordination in early permanent dentition skeletal ClassⅢmalocclusion

目的:应用颅面部锥形束CT(CBCT)对恒牙早期骨性Ⅲ类错[牙合]上、下颌后牙倾斜角度、牙弓及基骨弓宽度进行分析,通过模拟上颌前方牵引矫治,分析上、下颌矢状向变化对上、下颌骨宽度协调关系的影响,对骨性Ⅲ类错[牙合]前方牵引治疗中上颌牙弓扩大的必要性进行探讨。方法:选择2016年1月—2021年1月于上海交通大学医学院附属第九人民医院口腔正畸科就诊的恒牙早期骨性Ⅲ类错[牙合]患者20例,Ⅰ类个别正常患者20例,共40例。所有患者治疗前均拍摄颅面部CBCT,使用Mimics 20.0软件测量2组患者第一磨牙的颊舌向倾斜度,上、下磨牙牙弓宽度及磨牙间基骨弓宽度。对Ⅲ类错[牙合]患者上颌前方牵引进行三维模拟,对上、下颌骨矢状关系改变后的牙弓和基骨弓宽度进行测量。采用SPSS 21.0软件包对数据进行统计学分析。结果:Ⅲ类错[牙合]患者上颌磨牙颊侧倾斜,下颌磨牙舌侧倾斜(P<0.01);Ⅲ类和Ⅰ类错[牙合]患者下颌基骨弓宽度无显著差异,上颌基骨弓宽度Ⅲ类患者显著小于Ⅰ类患者(P<0.01),上、下颌基骨弓宽度差Ⅲ类患者显著小于Ⅰ类患者(P<0.01);而上、下颌牙弓宽度2组间无显著差异。上颌模拟前移3 mm时,Ⅲ类错[牙合]患者上颌牙弓宽度显著大于下颌(P<0.05);上颌模拟前移4 mm时,上、下颌牙弓宽度差Ⅲ类患者显著大于Ⅰ类患者(P<0.05);上颌模拟前移2 mm时,上颌基骨弓宽度和上、下颌基骨弓宽度差Ⅲ类患者显著小于Ⅰ类患者(P<0.05);前移3 mm时,上颌基骨弓宽度和上、下颌基骨弓宽度差无统计学差异。结论:恒牙早期骨性Ⅲ类患者表现出一定程度的上颌基骨宽度不足,上颌磨牙颊向和下磨牙舌向代偿性倾斜;但在上颌前牵引矫形治疗中,上、下牙弓和基骨弓宽度的协调程度随着上颌前移及下颌后下旋转的量而改变。上、下颌骨的矢状向变化是上颌骨是否需要扩弓的重要参考因素之一,如变化量超过3 mm,多数患者不需要在前方牵引治疗中配合上颌扩弓。

PURPOSE:To evaluate the effects of three-dimensional maxillary protraction simulation using cone-beam CT(CBCT)on the width of the upper and lower jaws in early permanent dentition patients with skeletal ClassⅢmalocclusion.METHODS:Twenty skeletal ClassⅢmalocclusion and 20 skeletal Class I patients according to the inclusion criteria from the Department of Orthodontics,Shanghai Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine between January 2016 and January 2021,were selected in this study.CBCT images were taken in all patients before treatment,and Mimics 20.0 software was used to measure the buccal-lingual inclination of the first molars and the width of the dental and basal arch of two groups of patients.Three-dimensional segmentation and maxillary forward movement simulation were performed to evaluate the dental and basal arch width after the sagittal relationship between the maxilla and mandible were changed.SPSS 21.0 software package was used for statistical analysis of the data.RESULTS:The maxillary molars inclined buccally and the mandibular molars inclined lingually in ClassⅢpatients(P<0.01);there was no significant difference in the width of the mandibular basal arch between ClassⅢand Class I,but the width of the maxillary base arch in ClassⅢwas significantly smaller than that in ClassⅠ(P<0.01),the difference between the maxillary and mandibular base arch widths of ClassⅢwas significantly smaller than that of class I(P<0.01);however,there was no significant differences in the width of the maxillary and mandibular dental arches between the two groups.During the maxillary protraction simulation in ClassⅢpatients,the width of the maxillary dental arch of ClassⅢwas significantly larger than that of the mandible when the maxilla was moved 3 mm forward(P<0.05).The width of maxillary basal arch and the difference between upper and lower basal arch width were still smaller than that of Class I when moving 2 mm(P<0.05);but when the forward movement was 3 mm,there were no significant difference in maxillary basal arch width and maxillomandibular basal coordination between ClassⅢand ClassⅠ(P>0.05).CONCLUSIONS:Skeletal ClassⅢpatients in early permanent dentition showed some insufficient development of maxillary basal arch width and buccal inclination of maxillary molars.During maxillary protraction treatment,the width of dental and basal arch change significantly with the amount of maxillary forward movement and mandibular rotation.The sagittal change of the upper and lower jaws is one of the most important factors to decide whether the maxillary expansion is needed.If the change exceeds 3mm,maxillary expansion might not be necessary.