Locking up of food between posterior teeth and its influence on chewing efficiency

Food particles are intra-orally locked up between antagonistic posterior teeth, during each chewing cycle. Food locking up (FL) may enhance selection of particles for subsequent breakage, hence chewing efficiency (CE). The two aims were to determine FL, and to examine the relationship between FL and CE.

A spherical gum bolus (volume: 1.3 cm³) that undergoes plastic deformation rather than breakage, was used to determine FL in 20 young adults. Chewing such a bolus with initially a width-length ratio of 1, decreases this ratio, the more locking up elongates the bolus to a greater extent by pressing from the tongue, teeth, and a cheek. Before and after chewing randomly for 2-6 cycles (3 trials each), the bolus was scanned and its width-length ratio was determined using imaging. The number of chewing cycles needed to attain a width-length ratio of 0.5, N(0.5 W-L ratio) was a measure of FL. CE corresponded with the number of cycles needed to halve the initial particle size, N(1/2-Xo), when chewing samples of 2 half cubes (9.6 × 9.6 × 4.8 mm; sample volume: 0.88 cm³) of a solid artificial model food.

N(0.5 W-L ratio) and N(1/2-Xo) were on average 3.21 cycles (SD 1.14) and 4.04 cycles (SD 1.87) respectively. Whereas a relationship between CE and FL was lacking for subjects whose CE was worse than the median, a pronounced quadratic U-shaped relationship (R² = 0.75; p < 0.01) occurred for subjects whose CE was better. This relationship might reflect an interaction between two tongue functions: transport and subsequently FL of particles.