To elucidate the relationship between masticatory performance and the size of denture foundations in complete denture wearers, 28 complete denture wearers (average age: 75.6±4.8 yrs) whose dentures were developed by one dentist using the same methods and materials were selected. The size of lower denture foundations in each patient were analyzed by the “replica method” newly developed by our department. Replica of each denture foundation was made by silicone impression material filling in the mucosal surface of the lower complete denture and cutting by rubbing the denture border.
The basal area (flat plane cut and rubbed denture border) of residual ridge replica were measured by the digitizer, and volume (weight of replica/specific gravity of silicone impression material) and height (volume/basal area×2) were calculated.
Voluntary maximal clenching force, masticatory efficiency, and cross-sectional area of masseter muscle in complete denture wearers were measured by occlusal force meter (Nihon Koden, Co.), sieving method, and CT-scan.
The results were as follows:
1. The height of residual ridge decreased significantly in relation to aging (p<0.05). But the basal area and volume of residual ridge did not depend on aging.
2. When voluntary maximal clenching force and basal area as well as volume and height of residual ridge replica were dependent variables, and masticatory performance was an independent variable, multiple correlation coefficient (R) as a means of multiple regression analysis was 0.834 (p<0.001).
Partial correlation coefficients (β) of each dependent variable were 0.640 (voluntary maximal clenching force:p<0.01), 0.531 (basal area of residual ridge:p<0.01), 0.489 (height of residual ridge: p<0.05), 0.321 (volume of residual ridge:p<0.05), and they were significant statistically.
3. Voluntary maximal clenching force decreased significantly in relation to aging. The cross-sectional area of masseter muscles by CT-scan did not decrease significantly in relation to aging.