The effect of different tooth extraction patterns on Bolton index and occlusal relationship of skeletal Class Ⅱ malocclusion
Objective To investigate the effect of different premolar extraction patterns on Bolton index and occlusal relationship of skeletal Class Ⅱmalocclusion.Methods The plaster models of 62 patients with skeletal ClassⅡmalocclusion were selected and con-verted into digital models by iTeroElement scanner.Each model was simulated by the four premolar extraction pattrens,and tooth ar-rangement 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 classⅡmal-occlusion,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 pat-terns of 5/4 and 5/5 was greater than the normal range(＞3 mm),and the difference was statistically significant(P＜0.001).Conclu-sion The premolar extraction patterns of 4/4 and 4/5 are more conducive to normalizing the Bolton index over-all ratio and establis-hing the better occlusal relationship for skeletal Class Ⅱ malocclusion.
orthodonticsskeletal Class Ⅱ malocclusionorthodontic extraction treatmentBolton indextooth arrangement test
NETL
NSTL
万方数据
