[Growth of the facial skeleton and biomechanics of the stomatognathic system].

Biomechanical analysis of the stomatognathic system yields that the linkage between posterior and anterior guidance can be modelled by a link quadrangle (throttle crank) with closed linkage. Within this gear system the biochemical ideal position of the couple-line (functional length of the mandible) possesses a special meaning in centric occlusion: Along this line the gear system can be stretched without altering its essential mechanical properties. Interindividual comparison of the arrangement of mandibulary and maxillary structures related to the ideal initial position of the couple-line presents interindividual constants of arrangement and of growth. It is possible to define an individual, non-orthogonal system of coordinates. Its origin represents the individual center of growth. During growth special skeletally defined points run along radius vectors of this center. The rate of growth can depend on the angle between radius vector and couple-line.