Abstract: Objective To study the dentofacial changes of adolescent patients with skeletal classⅡhyperdiverge malocclusion after the extraction of four premolars using MBT appliance and mini-screw implant. Methods 14 randomly selected adolescent patients with skeletal classⅡhyperdiverge cases were treated by MBT appliance and mini-screw implant. In order to evaluate the effect of the treatment, the cephalometric radiographs were taken before and after the treatment, and the data were analyzed statistically. Results Patient’s facial profile had been modified. Z angle increased. There were significant differences before and after the operation (P＜0.05). The angles of U1-SN and L1-MP decreased, while the distances of U1-NA and L1-MP adducted. There were significant differences before and after the operation (P＜0.05). Vertical dimension control between the maxilla and mandible was successfully achieved. The angle of SN-MP decreased. There were significant differences before and after the operation (P＜0.05). Conclusions Mini-screw anchorage and MBT appliance are effective in treating adolescent patients with skeletal classⅡ hyperdiverge cases, which can control the vertical distance between the maxilla and mandible, modify the soft tissue profile of patients, so as to achieve the goal of clinical hiding treatment and reduce the risk of orthognathic surgery.

Key words: adolescent, skeletal class Ⅱ, hyperdiverge, mini-screw, extraction