2001 Volume 22 Issue 2 Pages 144-153
Abstract : The habitual opening and closing motion of the mandible is not the same as that of the occlusal plane. When these two motions are illustrated on the sagittal and the horizontal planes, the occlusal plane has an angle to the mandibular motion in the sagittal plane, while it has an angle to the forward direction in the horizontal plane. Therefore, when we consider a vector which describes the motion in the small part of the occlusal plane, the vector can be decomposed into the upward and forward directions in the sagittal plane, and be decomposed into the forward and outward directions in the horizontal plane. As a result, this small part does not give rise to a simple compression load but a buckling load which is eccentric to the forward and outward directions. In other words, “bite” is not the compression load which pushes vertically the object with the force along the center axis of the object, but it is an action to mash and break food efficiently by the buckling load due to the force whose direction deviates from the center axis of the inhomogeneous object. Here we analyze the direction of the force of this buckling load and that of the force plane in the simplified habitual opening and closing motion, and examine them synthetically with unevenness of the occlusal surface form, the passive structure and the jaw position. In other words, we analyze “bite” scientifically from the point of view of mechanics and describe the outline how to make it useful for the dental clinic and show one clinical case.
