Masticatory efficiency determined with direct measurement of food particles masticated by subjects with natural dentitions.

The size of soya particles masticated by 10 subjects with natural teeth were directly measured by means of a graphic digitizer and a computer at a varied number of masticatory strokes. The statistical parameters were calculated by computer and a test of normality was used for estimating the frequency distribution. It was found that the frequency distribution of chewed particle size was a positive skew state; its shape was asymmetric, wide, and flat. After natural logarithm transformation the distribution tended toward normal. Increasing the number of masticatory strokes decreased the mean and median of the distribution (p less than 0.01) and did not change the coefficient of variation, skewness, and kurtosis (p greater than 0.05). The results show that the distribution of chewed particle size tends toward a normal logarithmic distribution; the distribution shapes at various numbers of strokes are the same; these parameters can be used for determining masticatory efficiency. Direct measurement of the particles is more convenient and reliable than dyeing particles or fractionating the particles in a sieve system.