Investigation of chewing patterns in deep-bite malocclusions before and after orthodontic treatment.

A knowledge of chewing provides a better understanding of normal jaw movement and can help form a basis for assessing the effects of malocclusion on jaw function. This study was conducted to describe the effects of deep-bite malocclusion on masticatory function and to determine what changes may occur with orthodontic correction. Five subjects, each exhibiting deep overbite in the early permanent or adult dentition, were selected for this study. Two subjects had Class II, Division 1 malocclusions, and the other three had Class I malocclusions. By means of the "replicator system" jaw movements during border movements and unilateral chewing were recorded and analyzed by computer plots. The typical chewing pattern of all five subjects was characterized by midsagittal opening, wide lateral closing movements, tooth gliding, and a pause at the intercuspal position and during swallowing. Comparison of these findings with chewing data from normal children in previous studies indicated that the deep-bite malocclusion did not create a major disturbance in chewing. Some differences between the preoperative and postoperative condition were noted, however. Prior to treatment, three subjects showed a nearly vertical chewing cycle which avoided tooth contact at the border path. Following treatment, all subjects showed a greater coincidence between the closing chewing path and the lateral border movement. This indicated more gliding tooth contact after treatment. Following deep-bite correction, the border paths showed a refinement of the intercuspal position (IP) and an increased steepness in lateral tooth guidance near IP. The total vertical component of tooth guidance was reduced by treatment.