OBJECTIVETo investigate the biomechanical changes with different directions distraction at midface.

METHODSAn anteriorly directed 500 g force was applied to the floor of apertura piriforms in different directions to the occlusal plane. Three-dimensional finite element analysis was used to evaluate the biomechanical change of craniofacial complex.

RESULTSAs the force direction was moved downward, the sagittal distraction length of the craniofacial complex decreased and vertical movement changed from upward to downward. The craniofacial complex was moved anteriorly when the downward force was applied about 20-30 degrees to the occlusal plane. The forces could generate the uniform stress distribution in the craniofacial sutures and avoid counterclockwise rotation of the maxilla.

CONCLUSIONSThe craniofacial complex can be effectively distracted anteriorly when the downward force is applied to the floor of aperture piriforms in direction of 20-30 degrees to the occlusal plane.