Effect of Sucrose Concentration on the Cariogenic Potential of Pooled Plaque Fluid from Caries-Free and Caries-Positive Individuals

Abstract

Pooled plaque samples were obtained from (1) coronal surfaces of two groups of caries-free (CF) subjects, (2) coronal 'white-spot' surface areas of a group of caries-positive (CP) subjects, and (3) exposed, sound root surfaces of root caries-free (RCF) and root caries-positive (RCP) subjects. The plaque samples were obtained before and 3 min after a 1 min rinse with a 0.5, 1, 2, 5 and 10% sucrose solution. Plaque fluid was then isolated from each plaque sample by centrifugation and analyzed for inorganic ions, organic acids, and pH values. With increasing sucrose concentration: (1) plaque fluid pH and the degree of saturation (DS) with respect to tooth mineral decreased; (2) the pH and DS values of CP and RCP samples were consistently lower than those of CF and RCF samples, respectively; (3) plaque fluid lactic acid concentrations increased and were consistently higher in the CP and RCP samples than in the CF and RCF samples, respectively, and (4) plaque fluid lactic acid concentrations leveled off between 1 and 5% sucrose; this occurred at lower sucrose concentrations with CP and RCP samples than with CF and RCF samples, respectively. RCP samples contained consistently higher levels of mutants streptococci than RCF samples. The chemical composition of plaque fluids, following sucrose exposure, were found to correlate well with caries history. The observed differences in lactic acid concentrations in samples from CF and CP subjects are discussed with regard to differences in microbiological composition and possible differences in plaque permeability to sucrose.