Influence of Film Thickness and Density on the pH of Glycolyzing Salivary Sediment and Dental Plaque

¹ Department of Dental Research, Tufts University School of Dental Medicine, Boston, Massachusetts

The pH's of samples of salivary sediment and dental plaque were investigated at steady state in glucose-bicarbonate buffer. Sediment thickness and density were studied for their influence on pH differentials between film and solution. Variations in these properties had little influence on pH differential attained after 2 hours' incubation. After 18 hours' incubation, variation of thickness over the usual range, from 0.2 to 0.6 mm., was found to be much more influential on pH differentials than was variation in the density from 5 to 12 per cent solid content. Preliminary studies were made of the influence of caries susceptibility of persons from whom saliva was obtained. Both the pH differential and its reduction by 0.01 per cent iodoacetate were studied with high-density sediments. The average pH differentials were the same for both types of saliva. pH differentials obtained from salivary sediment have questionable value as indices of caries susceptibility.