抄録
We evaluated differences in angulation among the first, second, and third molars on panoramic radiographs, at the initial examination, in a group where the mandibular third molar erupted properly and in a group where it was impacted, in cases that had received non-extraction orthodontic treatment. In addition, we assessed how the angulations changed of the first, second and third molars between the two groups during orthodontic treatment. Developing third molars undergo important angulation changes to erupt successfully. In this study, we selected cases where the posttreatment records indicated that the third molar was classified as stage G or H according to the Demirjian staging of tooth development. At stage G, the root walls are parallel but the apices remain open. At stage H, the apical tips of the roots are completely closed. We found that the long axes of the first, second, and third molars in the erupted group were upright during orthodontic treatment. We found that the third molars were initially tipped, and that a small change in angulation during orthodontic treatment may negatively influence third molar eruption. Holding back or distally tipping the lower first and second molars by full appliance orthodontic treatment in the mandible might increase the possibility of third molar impaction. (J Osaka Dent Univ 2018; 52: 45-50)
