The influence of jaw rotation on the morphogenesis of malocclusion.

I n previous investigations, the peculiarities of the rotational patterns of the jaws during growth have been studied. ‘3 2, 4, *a It has been suggestedi that mandibular rotation may be a mechanism of adjustment of the mandible to the maxillary complex. Anterior mandibular rotation seems to be a process of shortening of the mandible related to specific changes in gonial angle and condylar growth direction,lg and posterior rotation seems to determine the maximum length of the mandible. Operational definitions were proposed, and the difference between positional and morphogenetic rotations was stressed.lg Furthermore, it was shown that the difference in amount of growth of the two jaws was compensated for in two ways: either mandibular rotation and/or changes in the relative positions of the jaws. A “balance mechanism” was found between these two phenomena when related to the difference in growth rate of the two jaws.‘” The different combinations of these three variables during mandibular growth are diagramed in Fig. 1. This study” revealed also that there are several possible mandibular responses to a single given initial condition. A further step would be to determine the relation of the rotation of both jaws to different groups of malocclusions. The purpose of the present investigation was to study the relationship between the rotational pattern, the intensity of facial growth, and the morphogenesis of malocclusion. Two main questions were raised: (1) Does one definite rotational pattern lead to only one type of malocclusion? (2) Is the morphogenetic origin of a particular type of malocclusion single or multiple with respect to the rotation and intensity of growth of both jaws?