Abrasives in foods and their effect on intra-oral processing: a two-colour chewing gum study.

In this study we suggest that the presence of abrasives in food items lead to physiologic responses that reduce the amount of tooth loss because of abrasion. Subjects were presented with two pairs of two-colour chewing gum, one sample had 0.5 g of an abrasive powder added. Subjects were instructed to chew for 10 or 20 chewing strokes and then remove the gum. After removal the chewing gum was placed in a plastic bag and flattened. Each pair of gums was compared on the basis of the amount of mixing observed. In all cases the addition of the abrasive powder resulted in slower chewing and less mixing. Salivary flow rate increased from a resting value of 0.6 to 0.9 mL min(-1) when stimulated by the non-abrasive gum to 1.1 mL min(-1) with the abrasive gum. This difference was significant (P < 0.05). We conclude that when abrasive particles are detected in the mouth, less bolus manipulation is performed and more saliva is secreted. These responses would have the effect of reducing loss of tooth substance at the expense of reduced cominution of the food.