Abstract: Objective　To provide reference for clinical application?of miniplate implants assisting maxillary complex for maxillary protraction treatment. Methods　Establish the three-dimensional finite element model of the maxillary complex?with two types（L/Y）of modified miniplate implant .500g/side was applied to each?modified miniplate implant?respectively，the derection?was forward and downward?between?0°~50° degrees to the occlusion plane,we analyzed the trend of maxillary displacement.?Results　The application of two types(L/Y) of modified miniplate implants showed that the displacement of the maxilla?were basically consistent；In the application of modified miniplate implants to assist the maxillary protraction treatment, the maxillary dentition has a tendency to narrow；When pulling the maxilla forward and downward,and the angle to the occlusal plane was at 0-20 °,the maxilla rotated counterclockwise. When the angle was at 30-50 °, the maxilla rotates clockwise..Conclusions　1. The morphology of the modified micro-titan plate implants do not affect the displacement of the maxilla in the maxillary protraction treatment.2.The maxillary dentition become narrower after maxillary protraction treatment.3. The displacement trend of maxilla vary with the direction of traction, when the traction direction forward and downward at the angle of 0-20 °, there is a counterclockwise rotation in the maxilla,it benefit to deep crossbite patients;when at 30-50°, there is a clockwise rotation in the maxilla,it benefit to crossbite patients who accompany open bite.

Key words: maxillary protraction, threedimensional finite element, miniplate implant anchorage, maxillary retrusion