[Difference in the path between the incisal point and the tracer of simple mandibular movement recording apparatuses during the mandibular movement in the sagittal plane].

In order to study the difference in the path between the incisal point and its tracers, which were LED or a magnet, for two types of mechanism used in ready-made simple mandibular movement recording apparatuses, we calculated their locations during the rotally opening or protrusion of the mandible in the sagittal plane. The movement of the LED tracer was larger than that of the incisal point during the rotally opening movement, and its magnification ratio increased with increased opening. During the protrusion, the difference in their movements was affected by the balance of the inclination of the condyle path and the incisal path, and the movement of the tracer expanded vertically but contracted horizontally as the inclination of the incisal path was increased. The movement of magnet tracer was larger than that of the incisal point during the opening movement, but its magnification ratio decreased as the degree of opening increased. During the protrusion, the horizontal movement of the tracer was smaller than that of the incisal point, and its magnification ratio decreased as the inclination of incisal path became smaller. Its vertical movement was similar to that of the incisal point.