Simultaneous Distal Movement Of The Maxillary First And Second Premolars Can Be Achieved By Distal Movement Of The Maxillary First Molar Using A Headgear

Purpose: The purpose of this study was to investigate the precise effects of a headgear (HG) on the maxillary first premolar (U4), maxillary second premolar (U5), and maxillary first molar (U6).Materials and methods: The participants were divided into two groups: HG group and control group. The HG group consisted of 25 patients who were treated with an HG and maxillary lateral expansion. The control group consisted of 21 patients who received maxillary lateral expansion treatment. Movements of U4, U5, and U6 were measured using cone-beam computed tomography (CBCT). The mesiodistal positions of U4, U5, and U6 were assessed based on the vertical reference plane (VRP) defined by the landmarks of the maxilla.Results: Distal movement of U4, U5, and U6 was observed in the HG group, while mesial movement of U4, U5, and U6 was observed in the control group. Moreover, the positions of U4 and U5 were more distal than that of U6 in the HG group, while the positions of U4 and U5 were less mesial than that of U6 in the control group. The amount of distal movement of U4 and U5 was strongly correlated with that of U6 in the HG group.Conclusions: Simultaneous distal movement of U4 and U5 can be achieved with U6 distal movement using an HG in the early mixed dentition period. Moreover, the amount of distal movement of U4 and U5 was larger than that of U6. Hence, early orthodontic treatment using HG appears to be effective for correcting Class II malocclusion.