Effects of variously processed starch on pH of human dental plaque.

The aim of this investigation was to study the effect of starch in various cereal products on pH of human dental plaque in vivo as compared to availability to the alpha-amylase of starch in vitro. Three separate experimental series were performed including: 1) rye and wheat products, 2) wheat products processed under both mild and severe conditions, and 3) wheat products with and without added sucrose. The pH drop in dental plaque was studied after a mouthrinse in groups of 10 subjects. Solutions of glucose or sucrose were used as references. No differences were found between boiled rye and boiled wheat, nor between rye bread and wheat bread. Severely popped wheat resulted in the greatest pH drop, followed, in order, by drum-dried and extrusion-cooked products. Mildly steam-flaked and mildly dry-autoclaved products induced comparable small pH falls. Sucrose-sweetened wheat products resulted in lower plaque pH values compared to unsweetened products. This effect was most pronounced with a mildly processed sample. In all three series, the glucose and sucrose reference solutions showed the greatest pH drop. In conclusion, all processing methods increased the fermentability of starch in human dental plaque in vivo. Thus, the more severe the processing conditions the more prominent the pH falls. The pH drop in plaque in vivo correlated (r = 0.96 in Series 1 and r = 0.92 in Series 2) with the rate of starch hydrolysis with alpha-amylase in vitro.