The Influence of Initial Breakage on Size Reduction during Habitual Chewing of a Solid Test Food

Objectives Food comminution during chewing is due to intra-oral particle selection and subsequent breakage. Under conditions of habitual chewing and a nearly complete selection, the influence of initial breakage on particle size reduction was studied in trials with a first chewing cycle (N = 1) from a sequence of randomized trials with various cycle numbers. Furthermore, relationships were examined between degree of fragmentation from breakage (r-fr), molar maximal bite force (MBF) and chewing efficiency (the number of cycles needed to half the initial particle size, N(1/2-Xo)). Design Thirty-one subjects with a natural dentition chewed samples of 2 half-cubes (9.6 × 9.6x4.8 mm) of Optosil®, using sequences with 1-7 cycles, in 2-10 randomized trials; 10 trials with one cycle. Particle size distributions by underweight, characterized by median particle size, X50, were obtained using sieving. N(1/2-Xo) was derived from the log(X50)-log(N) relationship. and r-fr from the cumulative distribution of underweight fractions of damaged particles for N = 1. MBF was determined on both sides of the jaw using a force transducer and averaged. Conclusions A strong, decreasing regression occurred in X50 at N = 1 with r-fr (R2 = 0.934, p