双期矫治Ⅱ类错（牙合）第二期减数病例特征分析

Skeletal and dental features of extraction cases in the second phase of two-phase treated Class Ⅱ malocclusion

目的 分析比较双期矫治Ⅱ类错（牙合）畸形患者第二期减数与非减数病例的骨性及牙性特征.方法 选择21例双期矫治以下颌后缩为主的Ⅱ类错（牙合）临床疗效满意病例,头影测量比较拔牙组和不拔牙组各冶疗阶段骨性及牙性因素的差异,从而分析第二期减数病例的特征.结果 1.治疗前拔牙组与不拔牙组矢状向、垂直向骨型、上、下切牙位置及覆盖均无差异（P＞0.05）.2.矢状向骨型：不拔牙组第一期治疗Wits埴改善较拔牙组显著（P＜0.05）.第二期治疗中不拔牙组SNB增大（P＜0.05）,Wits值减小（P＜0.05）,表现利于矢状向骨型改善的生长型.垂直向骨型：拔牙组第二期治疗中MP-SN减小.3.下切牙：经第一期治疗后两组下切牙均唇倾（P＜0.05）,拔牙组LI-NB增大显著（P＜0.001）.第二期治疗不拔牙组LI-NB进一步增大（P＜0.01）,而拔牙组有效回收下切牙（P＜0.05）.结论 1.通过治疗前的骨性、牙性特征不能判断第二期治疗是否需要减数.2.经第一期治疗矢状向骨型改善有限、下切牙唇倾过多的病例第二期拔牙可能性大.3.对于表现为不利于矢状向Ⅱ类骨型改善的垂直生长型病例,第二期减数利于垂直向控制.

Objective To investigate the skeletal and dental features of extraction cases in the second phase of two-phase treated Class Ⅱ malocclusion. Methods Twenty-one two-phase treated Class Ⅱ cases with satisfied treatment results were chosen （11 extraction cases and 10 non-extraction cases）. The sagittal skeletal pattern, vertical skeletal pattern, incisors＇ position and overjet were examined from cephalograms before treatment （T0）, at the end of phase Ⅰ treatment （T1） and at the end of phase 2 treatment （T2）. Results （1） There was no difference in skeletal and dental factors between extraction and non-extraction groups before treatment （T0） （P 〉 0. 05）. （2） In nonextraction group, improvement of Wits in the first phase was significant than that in extraction group （P〈0. 05）. SNB increased and wits decreased significantly in the second phase of treatment in nonextraction group （P〈0. 05）, which indicated favorable growth pattern. （3） MP-SN was reduced approaching statistical significance （P=0. 052） in extraction group in the second phase of treatment.（4） In the first-phase treatment, reduction of U1-NA was significant in non-extraction group （P〈0. 05）. （5） In the first-phase treatment, LI-NB was significantly increased （P〈0. 001） in extraction group. （6） The overjet at the end of treatment （T2） was less in extraction group than that in non-extraction group, which indicated over-correction. Conclusions （1） Decision can not be made only according to the skeletal and dental factors before treatment. （2） Extraction and over-correction in the second phase may be considered for those cases which show limited improvement of sagittal skeletal pattern after the first phase of treatment. （3） Extraction may be considered if upper incisors are not much retracted while lower incisors are much proclined during the first-phase treatment. （4）Extraction in the second phase may be considered for cases with vertical growth pattern, which could benefit vertical control and achievement of balanced Tweed triangle by lower incisors＇ retraction.