关键词: 前牵引, 矫治方向, 反作用力, 颞下颌关节, 三维有限元

Abstract:

Objective    To offer a scientific basis for treating Class Ⅲ malocclusion more well，and avoid injuring TMJ，a three-dimensional finite element model （FEM） of craniomaxillofacial complex was used to analyse the influence of the reactive force on TMJ when protraction direction magnified clockwise. Methods    A healthy young male volunteer was selected；establish a complete three-dimensional （3-D） finite element model，which included TMJ；imitate the force pattern of maxillary protraction；exert a given force on chin；change the direction clockwise；the stress distribution and displacement on jaw and TMJ were analysed. Results    Stress distribution： the biggest stress points appeared in the loading position chin after loading nodal force from different angle. The stess in the contact region，such as the glenoid fossa，condylar head and neck，was also relatively concentrated. Under the action of different angle，the maxilla and mandible both produced contact stress. Displacement：in a certain angle on the nodal force，the model produced tiny displacement change，the largest position displacement in loading part. Conclusion    （1）Protraction appliance does produce reactive force on mandible and TMJ when making maxilla forward，so we need to consider both the two aspects；（2）The traditional way of boosting does not seem to be the best choice，and from the two aspects of action and reaction，40°is superior to 37°。

Key words: protraction, protraction direction, reactive force, temporomandibular joint, three-dimensional （3-D） finite element