The biomechanical relation between incisal and condylar guidance in man.

The arrangement, form and movement of incisal and condylar guidance allow representation of the stomatognathic system by a gearing with positive drive and closed linkage. Because of problems of stability, this gearing has to be a throttle crank. Therefore, the stomatognathic elements have to fulfill the condition of Grashoff. The analysis of 14 Class I patient data confirms this condition and yields that their stomatognathic systems seem to be determined by only two parameters. The properties of these systems are largely independent of the jaw's growth if the momentary growth takes place in the direction of the initial inclination of hinge-axis movement out of centric relation.