First Step to Understand Jaw Movement −For the CAD/CAM Era−

Abstract

Jaw movement is a complex motion as translational (anterior-posterior, left-right, and upper-lower) and rotational (around each axis) motion of mandible in the three-dimensional space. The movement of the mandible observed from the maxilla is called mandibular movement, while the movement of the maxilla observed from the mandible is called complementary mandibular movement. Complementary mandibular movement is often not clearly distinguished from mandibular movement, even though it is frequently used in clinical practice, as in the case of articulator with incisal guide table attached to the mandible and condylar-type articulators.

In the present review, the authors addressed Gothic arch drawing in the horizontal plane, border movement trajectory in the sagittal plane, as well as the configuration of the articulator and its correspondence to jaw movement, and organized the mandibular movements and complementary mandibular movements so that the relationship and differences between them can be properly understood. In addition, in order to reproduce jaw movement as numerical model in the coming CAD/CAM era, the concepts of kinematic axis as a model of mandibular movement, complementary kinematic axis as a model of complementary mandibular movement, and intermaxillary axis as a model common to both mandibular movement and complementary mandibular movement are presented. Moreover, in order for readers to be able to calculate the mandibular and complementary mandibular pathways, and the respective axes at arbitrary positions using actual jaw movement data, the authors have carefully described the calculation procedure using Excel and devised a way for readers to experience jaw movement analysis.

Jaw movement is a 6-degree-of-freedom movement consisting of translational and rotational motion in three directions, but the present review focuses on 2-degree-of freedom and 3-degree-of-freedom jaw movements. It is hoped that this review will be the first step for readers who are learning to understand jaw movement.