The effects of different concentrations of sucrose, fructose, and glucose on pH changes by Streptococcus mitior in an artificial mouth

The aim of this study was to determine the effects of the initial sucrose (S) concentration, as well as those of fructose (F), glucose (G), and invert sugar (F/G), on the pH developed by a layer of S. mitior, to represent dental plaque, in an artificial mouth which simulates the process of oral sugar clearance. At S, F. G, and F/G concentrations of 2% and with normal oral sugar clearance rates, the bacteria produced a smaller pH fall from S than from the other sugars; at initial concentrations of 20%, however, the differences were not significant. With constant S concentrations of 0.5-35%, the minimum pH reached was 4.03 +/- 0.14 (S.D.); with S concentrations of 50% and above, slightly but significantly higher values (4.41 +/- 0.34) occurred. However, with normal sugar clearance, the pH fall was much less than with a constant concentration and was dependent on the S concentration over the range of 0-10%, but was independent at higher concentrations. Exposure of the bacteria to S for as short a period as two min during normal sugar clearance gave a nearly maximum pH fall. This suggests that rinsing the mouth with water more than two min after consumption of sucrose in liquid form will have very little effect in reducing the pH fall in dental plaque. A more appropriate method for reducing acid formation by dental plaque would be consumption of a salivary stimulant which would increase the flow rate and buffer capacity of the saliva.