Correlations between functional and occlusal tooth-surface areas and food texture during natural chewing sequences in humans.

The dental-arch surfaces preferentially used in mastication were studied by measuring functional and occlusal surface areas and comparing these to the number of chews required to swallow foods of different texture properties. The functional surface of the teeth was defined as the total area of visible wear facets on post-incisal teeth, adding to it the contacting areas of restored teeth where no facets were visible. Occlusal surface area was taken as the total area of the occluding parts of post-incisal teeth. Both surfaces were measured with computer image processing on dental-stone casts of the teeth of 31 young adults. Functional surface areas (mean 168 mm(2), four quadrants) were positively correlated with occlusal surface areas (mean 739 mm(2), four quadrants). The left:right area ratios were more variable for functional than for occlusal surfaces. Functional surface-area ratios markedly different from 1.0 might reflect functional side-preponderance of masticatory activity. Correlations between tooth surface area and the number of cycles were examined with five different food samples of known texture during side-imposed mastication. Depending on the elastic moduli of the foods, significant negative correlations were found between the left:right ratios of functional or occlusal surface areas and the left:right ratios of cycle numbers. The rheological properties of the food particles chewed were assumed to be the key factor in the correlations with either the functional or anatomical occlusal surfaces.