 The initial movement inside this envelope is directed by the shape of the teeth in contact and the Glenoid Fossa/ Condyle shape.The outer extremities of this envelope are limited by muscles, ligaments and the acticular disc of the TMJ.Without the guidance of anterior incisors and canines, this envelope of function can be destructive to the remaining teeth resulting in periodontal trauma from occlusion seen as wear, fracture or tooth loosening and loss.