Effects of the orthodontic treatment on the mandibular third molar with different angulations

Objective To study the effect of different orthodontic treatment on impacted mandibular third molars.Methods Totally 79 adolescent patients were involved in the study.A total of 154 mandibular third molars were divided into four groups according to the mandibular third molar angulation and the extraction conditions.(1)Treatment without extraction,the angulation ≤30°.(2)Treatment without extraction,the angulation30°.(3)Treatment with extraction,the angulation ≤30°.(4)Treatment with extraction,the angulation30°.The pretreatment and posttreatment panoramic radiographs were measured to evaluate the change of angulation and the eruption space of mandibular third molar.Results The angulation of third molar reduced in the third group(P 0.05)while eruption space increased in all groups(P 0.05).The space increase in extraction groups was significantly larger than that in nonextraction groups(P 0.01).Conclusion Extraction in orthodontic treatment can improve the erection angle of mandibular third molar with smaller angulation.Compared to nonextraction treatment,extraction can increase the eruption space of mandibular third molar significantly,and promote the eruption of third molar.