The effects of food fragmentation index on mandibular closing angle in human mastication

Jaw movements were recorded using a three-dimensional magnetic sensing syst em (Sirognathograph, Siemens) rn 10 human volunteers while chewing standard ized volumes of 15 food types, ranging from soft cheeses to hard nuts. The maximum horizontal amplitude inside the chewing loop (width of the loop), t he height of the loop (vertical amplitude) and the closing angle made by th e jaw during the late closing phase of the cycle relative to the vertical w ere calculated. The most highly significant correlation was between the clo sing angle and the square root of the ratio of two mechanical properties of the food - the toughness (R) and modulus of elasticity (E)(r = -0.85, p < 0.001). The width of the chewing loop was also significantly correlated wit h the above combination of food properties (r = -0.75. p < 0.01) whereas th e vertical amplitude was not. Thus, the mechanical properties of foods appe ar to influence the pattern of mandibular movements in human mastication si milarly to their reported effect on food breakdown rates and anterior tempo ralis activity during mastication. (C) 2000 Elsevier Science Ltd. All right s reserved.