It has been tremendous documentation concerning the effects of mechanical stress on the periodontium. However, the results remain controversial. It may be due to the variations derived from different types, duration, or magnitute of stress. The types of stress include abnormal chewing habits, orthodontic force, occlusal overloading, jiggling force, and also the strong load such as motor-car accidents. In addition, various animal models, examination parameters and study methods may also lead to different results. The purpose of this comprehensive review is to evaluate the influences of the mechanical stress on the periodontal tissues.