Meeting Abstract
P1.107 Thursday, Jan. 3 The relationship of mandibular strain to variance in the chew cycle phase slow close in Cebus capucinus REED, D.A.*; ROSS, C.F.; University of Chicago; University of Chicago dreed@uchicago.edu
The variance in chew cycle phase durations during mammalian mastication is typically used as evidence for active modulation. A system which combines high-resolution, three-dimensional kinematics with electromyography and bone strain has been developed to investigate the relationship between this variance and variance in food material properties. Chewing on tough foods (i.e. dry apricot, dry date, dry pineapple) elicits on average a 120 ms increase in cycle duration compared to chewing on nuts (i.e. almonds, peanuts, cashews) during the first five chews of a chew sequence. Slow close duration on tough foods was also on average 40 ms longer for the first five chews when compared to chewing on nuts. This increase in slow close duration was significantly correlated with the higher cycle time of tough foods, accounting for 47.6% of the measured variance. In addition, chewing tough foods elicited an average 1.26 mm increase in vertical excursion of the molar during slow close independent of food item size. This increased vertical excursion was significantly correlated with both the increased slow close duration and the increased cycle duration of tough foods, accounting for 64% of the variance in the former but only 18% of the variance in the latter. Using mandibular strain as a surrogate for the onset of bite force, we can begin to investigate if this increase in vertical excursion is an active or passive response to tooth-food-tooth contact. It was found that the onset of mandibular strain occurs prior to the onset of SC and is affected by food type. However, the onset of a rapid loading phase occurring prior to peak strain is invariant relative to the fast close slow close transition. This suggests that the time between initial food contact and onset of rapid bite force production is affected by food material properties.
