不同拔牙方式对骨性Ⅱ类错[牙合]畸形Bolton指数及咬合关系的影响

The effect of different tooth extraction patterns on Bolton index and occlusal relationship of skeletal ClassⅡmalocclusion

目的探讨不同的前磨牙拔除方式对骨性Ⅱ类错[牙合]畸形Bolton指数及咬合关系的影响。方法筛选62例符合研究标准的骨性Ⅱ类错[牙合]畸形患者的记存石膏模型,通过iTero Element扫描仪将石膏模型转换为数字化模型,每一例模型均按照常见的4种前磨牙拔除方式进行数字化拔牙,并进行拔牙后的排牙实验,计算拔牙前后的Bolton指数,并对排牙实验所建立的咬合关系进行评估,探索其变化规律。结果对于骨性Ⅱ类患者,四种前磨牙拔除方式均会导致Bolton指数全牙比明显减小,且相比于上4下4和上4下5的拔牙方式,上5下4和上5下5的方式会导致Bolton指数全牙比减小更多(P<0.001)。对于骨性Ⅱ类患者,在建立磨牙中性关系的基础上进行排牙实验,上4下4和上4下5的拔牙方式获得的前牙覆盖均值在正常值范围内(<3 mm);上5下4和上5下5的拔牙方式获得的前牙覆盖均值大于正常值(>3 mm),且差异具有显著统计学意义(P<0.001)。结论对于骨性Ⅱ类错[牙合]畸形的患者,上4下4和上4下5的拔牙方式更有利于使拔牙后Bolton指数全牙比趋于正常,也更有利于建立更良好的咬合关系。

Objective To investigate the effect of different premolar extraction patterns on Bolton index and occlusal relationship of skeletal ClassⅡmalocclusion.Methods The plaster models of 62 patients with skeletal ClassⅡmalocclusion were selected and converted into digital models by iTeroElement scanner.Each model was simulated by the four premolar extraction pattrens,and tooth arrangement test was performed after tooth extraction.The Bolton index before and after tooth extraction was calculated,and the occlusal relationship after tooth arrangement was evaluated to explore its law.Results All the four premolar extraction patterns resulted in a significant decrease in the Bolton index over-all ratio in skeletal ClassⅡpatients,and compared with the extraction patterns of 4/4 and 4/5,the patterns of 5/4 and 5/5 resulted in a greater decrease in the Bolton index over-all ratio(P<0.001).For skeletal classⅡmalocclusion,the tooth arrangement test was conducted on the basis of establishing the neutral relationship of first molar.The average value of anterior teeth over-jet obtained by patterns of 4/4 and 4/5 was within the normal range(<3 mm).The average value obtained by patterns of 5/4 and 5/5 was greater than the normal range(>3 mm),and the difference was statistically significant(P<0.001).Conclusion The premolar extraction patterns of 4/4 and 4/5 are more conducive to normalizing the Bolton index over-all ratio and establishing the better occlusal relationship for skeletal ClassⅡmalocclusion.