Effects of maxillary protraction on the displacement of the maxilla

Ko, Jeong Seok; Kim, Jong Chul

Abstract

In the orthopedic therapy, the biomechanical analysis of the appliance is necessary to get a desirable orthopedic effect. The purpose of this study was to investigate the desirable direction and application position of the protraction force. The protraction force of 500g was applied to the first premolar or to the first molar. The direction of force application was paralell or 20degrees downward to the occlusal plane respectively. The stress distribution and the displacement within the maxilla was analyzed by a 3-dimensional finite element method. The findings obtained were as follows : 1. Protraction forces caused a counterclockwise rotation of the maxilla. 2. The degree of maxillary rotation was less when the force was applied 20degrees downward direction to the occlusal plane than when applied to the parallel direction. 3. The degree of rotation of maxilla was greater when the parallel force was applied to the 1st premolar than when applied to the first molar, whereas it was greater when force is applied 20degrees downward than at the first premolar. In conclusion, the 20degrees downward protraction from the first premolar induced the least counterclockwise rotation of the maxilla and was thought as the desirable direction and application position of the protraction force.