RECORDING ORTHOPEDIC JAW MOVEMENTS .4. THE ROTATIONAL COMPONENT DURING MASTICATION

The recording and analysis of mastication provides information on neur omuscular engrams, and hence avoidance mechanisms. Avoidance mechanism s are pathologic movement patterns which are developed to avoid occlus al interferences during functional movements. Evaluation of hinge-axis rotation permits selective quantitative analysis of a complex movemen t pattern. The objective of this study was to determine the amount of hinge axis rotation in mastication using computerized axiography. Furt hermore, the distance of the condyles from reference position (RP) at maximum rotation was evaluated and the chronological sequence of trans lation and rotation was investigated. The mean value for the rotationa l angle of the mandible (gamma) during mastication was 14.1 degrees in the volunteers and 13.44 degrees in the patients. The linear spatial distance from RP amounted to a mean of 6.57 mm on the right side and 6 .21 mm on the left in the volunteers. In the patients, the measurement s were 6.33 mm on the right side and 6.7 mm on the left. In most cases , maximum rotation did not correspond with maximum translation. The ch ronological sequence of maximum excursion was not constant.