前牙形态大小与正畸治疗后拥挤复发的关系

Relapse of Anterior Crowding after Orthodontic Treatment in Relation to Tooth Size and Morphology

【目的】了解前牙形态大小及接触点对正畸治疗后前牙拥挤复发的影响。【方法】以正常牙合作对照 ,测量分析10 4例矫治前前牙拥挤、矫治后以及维持后 2 4年牙模 ,测量其前牙不整齐指数 (IRID)、尖牙间宽度及计算其下切牙牙冠近远中径 /唇舌径 (MD/FL)比值 ,观察前牙区相邻牙之间接触形式。【结果】临床排列整齐 (IRID≤ 1 5mm )者 ,切牙MD/FL比值正常或偏小 ,临床排列不整齐 (IRID >3 5mm)者 ,切牙MD/FL比值偏大 ;旋转牙矫治后邻牙间以点接触形式居多 ,排列整齐的正常牙合及矫治后未复发的患者上下前牙邻接区为面接触。【结论】MD/FL比值偏大 ,前牙间点接触是导致矫治后不稳定因素之一。

Objective To evaluate the effects of the anterior teeth shape, size and anatomic contact points on relapse of crowding of the corrected teeth. Methods The study sample consisted of 104 cases with crowded, rotated anterior teeth before orthodontic treatment. The amount of crowding of dental casts, which were taken at the beginning(T1), at the end(T2) of treatment and at the postretention(T3) 2.4 years, were measured according to Little's irregularity index (IRID). Meanwhile the intercanine width were measured and the ratio value of the mandible incisors (mesiodistal length /faciolingual width, MD/FL) was calculated. The anatomic contact point of the anterior teeth were observed. Results Some relations were found between the IRID and the MD/FL Ratio. When IRID≤1.5 mm, the value of mandible incisor's MD/FL ratio was normal or slightly lower; when IRID>3.5 mm, the value of ratio was higher than that of normal; the corrected teeth that were crowding or rotating before treatment kept smaller point of contact between the anterior teeth and the normal occlusal teeth, or alignment anterior teeth after retention possessed good contact area.[Conclusion] The abnormal contact area of anterior teeth partly results from bigger value of the MD/FL ratio. The abnormal point of contact of the corrected teeth among the anterior area is one of unstable factors which make the corrected teeth relapse.