正畸治疗对第二磨牙错位萌出影响的初步研究

目的　调查正畸治疗中第二磨牙错位萌出与正畸门诊患者第二磨牙错位的发病率和分布规律，分析两者的不同之处及其相关因素。方法　选取10~16岁的正畸门诊患者，根据初诊时第二磨牙是否萌出分为2组。实验组为初诊时4个第二磨牙均未萌出，治疗结束时均已萌出，随机抽取样本222例；对照组为初诊时4个第二恒磨牙已萌出建牙合，随机抽取样本474例，在全景片和石膏模型上分析两组患者各类第二磨牙错牙合的发病率和分布规律，用卡方检验将2组数据进行横向对比。结果　 对照组第二磨牙总错牙合发病率为70％，上颌第二磨牙颊倾发病率最高（36.27％），下颌舌倾发病率最高（31.65％）。实验组第二磨牙总错牙合发病率为79.73%，正畸治疗后下颌磨牙近中倾斜、远中倾斜、阻生的发生率增加，深覆盖的发生率增加。结论　 正畸治疗患者第二磨牙错牙合发病率较高，要将第二磨牙纳入矫治计划，选择适当的矫治时机。

Primary study on the change of the second molar malocclusion due in orthodontic treatment

Objective The purpose of this study was to investigate the incidence of the second molar malocclusion in orthodontic patients and post-treatment patients to find out the differences between these two groups,and then analysis the reasons.Methods The samples for this study were obtained from 10 to 16 year-old orthodontic patients.The samples were divided into two groups（study group and control group）according to the eruption of the second molar.Study group consisted of 222 subjects whose second molar didn′t erupt before treatment,and erupted during orthodontic treatment.Control group consisted of 474 subjects whose second molar erupted completely before treatment.The incidence of the second molar malocclusion was investigated in each group by panoramic radiographs,then the differences of these two groups were analyzed with Chi-square test.ResultsThe incidence of malocclusion of second molar was 70% in control group.The analysis of malocclusion of upper second molar showed that the incidence of buccal malposition was the highest（36.27%）,and the incidence of lingual malposition was the highest（31.65%） in lower second molar malocclusion.The incidence of malocclusion of second molar was 79.73% in study group.The data showed that the incidence of mesioclination,distoclination and impaction of lower second molar became higher after treatment.Conclusions The incidence of malocclusion of second molar was high in orthodontic treatment.Dentists should consider the status of the second molar of the orthodontists when they make a diagnosis,and make treatment planning.