Functional conditions of the mandible: theory and physiology

The functional conditions of the mandible are differentiated according to t he number of kinematic degrees of freedom assigned to each mandibular movem ent. One degree of freedom: pro- and retrusive occlusal border movement. Th e interplay of the TMJs with the occluding teeth determines a compulsory co urse which corresponds to a 4-bar-chain guidance. 2 degrees of freedom: fre e sagittal mouth movement without tooth contact. Using graphic recordings o f cyclic mandibular movements, the mobile hinge axis is identified as a man dibularly fixed line which is not directly categorized as a part of an anat omical structure. In the maxillary coordinate system, its movement describe s a cylinder; sagittally, it describes a circle. The mandibular positions a re clearly identifiable with 2 angles. The in vivo measurements show that n euromuscularly healthy systems supply the mandible with anticipatory guidan ce. 3 degrees of freedom: bolus function. The articular space in the TMJ is utilized.