Primary study on the change of the second molar malocclusion due in orthodontic treatment

Objective The purpose of this study was to investigate the incidence of the second molar malocclusion in orthodontic patients and post-treatment patients to find out the differences between these two groups,and then analysis the reasons.Methods The samples for this study were obtained from 10 to 16 year-old orthodontic patients.The samples were divided into two groups(study group and control group)according to the eruption of the second molar.Study group consisted of 222 subjects whose second molar didn′t erupt before treatment,and erupted during orthodontic treatment.Control group consisted of 474 subjects whose second molar erupted completely before treatment.The incidence of the second molar malocclusion was investigated in each group by panoramic radiographs,then the differences of these two groups were analyzed with Chi-square test.ResultsThe incidence of malocclusion of second molar was 70% in control group.The analysis of malocclusion of upper second molar showed that the incidence of buccal malposition was the highest(36.27%),and the incidence of lingual malposition was the highest(31.65%) in lower second molar malocclusion.The incidence of malocclusion of second molar was 79.73% in study group.The data showed that the incidence of mesioclination,distoclination and impaction of lower second molar became higher after treatment.Conclusions The incidence of malocclusion of second molar was high in orthodontic treatment.Dentists should consider the status of the second molar of the orthodontists when they make a diagnosis,and make treatment planning.