A review: neural control of mastication in humans as influenced by food texture.

This review summerizes recent approaches to the physiology of the masticatory system in humans that aim to understand how the process is influenced by the material properties of foods. The centerpiece is a group of experiments that show that the rate of breakdown of food in human mastification depends principally on the combination of two mechanical properties of foods: toughness(R) and modulus of elasticity (E). Two mechanical indices are constructed from these properties: the square root of their product, (ER)0.5, is predicted to explain the resistance to an incisal bite, while the square root of their ratio, (R/E)0.5 is predicted to control the rate of fragmentation during a postcanie bite. Evidence for the latter is reviewed, which also appears to modulate the activity of jaw closing muscles and the extent of lateral mandibular movement during mastication. These studies provide a quantified link between the food stimulus and the physiological response of the mastiatory system for which we know of no parallel. Attempts to extend this analysis have been made by psychophysical investigations of food texture. These support some sensitivity to the mechanical index that we have identified, but are not conclusive. Finally, we provide a chart summarizing physiological responses to food texture that could interest dentists, food scientists and also those interested in the analysis of dentition and diet in mammals.