[Relationship between occlusal condition and the changes of bolus property during mastication]

The purpose of this study was to clarify the relationship between occlusal condition and changes of bolus property during mastication. The methods and results were as follows. Subjects were selected according to the classification of anterior-posterior occlusal condition of the first molars (Angle' Class I, II, III group). 1. Evaluation of the relationship between occlusal condition and subjective chewing difficulty based on a questionnaire survey using a visual analog scale (VAS): Class II and Class III groups showed significantly higher subjective chewing difficulty compared to the Class I group. 2. Evaluation of the relationship between occlusal condition and changes of bolus property (chewiness) during mastication: In the Class II and Class III groups, the decrease in chewiness during the initial phase of mastication was significantly low compared to that in the Class I group. 3. To verify the results of 2, we examined bolus destruction for different loading directions using FEM and evaluated the differences among the three groups. We also investigated the correlation of the actual jaw movement and the masticatory efficiency according to the loading direction in the three groups: In the Class II and III groups, actual jaw movement was not significantly correlated with the most efficient loading direction in bolus destruction compared to that in the Class I group. These results indicate the correlation between occlusal condition and changes of bolus property during mastication. The subjective chewing difficulty may be one mediating factor. The efficiency of bolus destruction during mastication may also be associated with the relationship between occlusal condition and bolus property.