Abstract: Objective To compare the clinical effects of using two different positions of micro-screw implants in the treatment of dental and skeletal maxillary protrusion patients requiring extraction of premolar orthodontic?therapy. Methods 38 patients with indications were selected. According to the implantable height of micro-screw implants in maxillary molar region, the patients were divided into High position group (20 cases) and Low position group (18 cases) . The data before and after treatment were analyzed statistically. Results The upper anterior teeth of all the patients got obvious retraction and intrusion. The data of U1-SN/(°) ，U1-PP/(°) decreased significantly(P＜0.05)after operation , while the High position group’s decreased more(P＜0.05). The results showed that High position group lost more anterior teeth torque. The distance of U6-PP decreased(P＜0.05) while High position group’s decreased significantly(P＜0.05), indicating that we got posterior teeth intruded, and High position group is effective. Conclusions Both methods could be effective in the treatment of dental and skeletal maxillary protrusion . More retraction of the upper anterior teeth and the maxillary retraction could come out from Low position group.Better vertical control could be got from High position group，from which we obtained more intrusion of posterior teeth, more counter clockwise rotation of the mandible.

Key words: Micro-implant anchorage, Mixed maxillary protrusion, Retraction, Intrusion.