不同前磨牙拔除模式对安氏Ⅰ类病例下唇软组织的影响

目的：通过对拔除第一前磨牙和拔除第二前磨牙安氏Ⅰ类错病例治疗前后下唇软组织变化的比较,探讨两种拔牙模式的异同。方法：选取50例安氏Ⅰ类（骨性Ⅰ类）临界病例,随机分为两组,拔4个第一前磨牙和4个第二前磨牙病例各25例,按性别、年龄、骨面型、拥挤度严格配对,对治疗前后的头颅侧位X线片软组织的14项指标进行测量。结果：在相对X、Y轴的绝对值测量中,治疗前两组无任何统计学差异;治疗后第一前磨牙拔除组线距的明显增长表现在垂直方向上,而第二前磨牙拔除组表现在在水平方向上。在软组织测量项目中,治疗前第一前磨牙拔除组颏唇角和下唇厚度均大于第二前磨牙拔除组,组间差异有统计学意义（P〈0.05）。矫治后,拔除第一前磨牙组下唇倾角、下唇长、下唇基部厚度、颏唇沟深度增加,而颏唇角、下唇基角、下唇厚、下唇突度、下唇突凹点相对E线的距离减小。拔除第二前磨牙组颏唇角、下唇倾角、下唇基角、下唇基部厚度均增加,其中下唇倾角和下唇基部厚度的变化明显;下唇长、下唇突度、下唇突凹点相对E线的距离减少,而下唇厚基本不变。结论：拔除第一和第二前磨牙组在治疗前后下唇的各项软组织角度和线距变化均无统计学的差别。

Soft Tissue Changes of Low Lip with Different Premolar Extraction Patterns

Objective：To compare changes of the low lip soft tissue in patients with Class I malocclusion after extraction of either first premolars or second premolars. Methods：The pretreatment and posttreatment records of 50 patients were used in the study. 25 patients were involved extraction of first premolars and 25 patients were involved the extraction of second premolars. All patients were skeletal ClassⅠand matched by the gender,age,facial divergence and crowding. The lateral cephalometric radiographs taken before and after treatment were traced and measured. 14 typical values of soft tissue were measured in Winceph 7.0 software and statistical analysis was carried by Spss10.0 software. Results：The horizontal and vertical lines were not significant different in the two extraction groups before the treatment. But after the treatment the vertical changes of low lip were more apparent in the first premolar extraction group. In the soft tissue measurements,the values of mentolabial angle,thickness of low lip in the first extraction group were more than those in the second extraction group significantly before the treatment. After the treatment the patients of the first premolar extraction group had an increase in ∠B＇-LL-FH,length of low lip,thickness of low lip base and depth of mentolabial groove. At the same time,mentolabial angle,∠S-Ns-B＇,thickness of low lip,protruding of low lip and distances of LL-E line were diminished. But in the second extraction group mentolabial angle,∠B＇-LL-FH,∠S-Ns-B＇ and thickness of low lip base were increased and length of low lip,protruding of low lip and distances of LL-E line were diminished. And of all the changed values ∠B＇-LL-FH,thickness of low lip base were increased significantly（P0.05） . Conclusion：The low lips both changed remarkably after the treatment but there was no significant difference between the two premolar extraction groups.