EFFECT OF SUCROSE CONCENTRATION ON THE CARIOGENIC POTENTIAL OF POOLEDPLAQUE FLUID FROM CARIES-FREE AND CARIES-POSITIVE INDIVIDUALS

Pooled plaque samples were obtained from (1) coronal surfaces of two g roups of caries-free (CF) subjects, (2) coronal 'white-spot' surface a reas of a group of caries-positive (CP) subjects, and (3) exposed, sou nd root surfaces of root caries-free (RCF) and root caries-positive (R CP) 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 flu id was then isolated from each plaque sample by centrifugation and ana lyzed for inorganic ions, organic acids, and pH values. With increasin g sucrose concentration: (1) plaque fluid pH and the degree of saturat ion (DS) with respect to tooth mineral decreased; (2) the pH and DS va lues of CP and RCP samples were consistently lower than those of CF an d RCF samples, respectively; (3) plaque fluid lactic acid concentratio ns increased and were consistently higher in the CP and RCP samples th an in the CF and RCF samples, respectively, and (4) plaque fluid lacti c acid concentrations leveled off between 1 and 5% sucrose; this occur red at lower sucrose concentrations with CP and RCP samples than with CF and RCF samples, respectively. RCP samples contained consistently h igher levels of mutans streptococci than RCF samples. The chemical com position of plaque fluids, following sucrose exposure, were found to c orrelate well with caries history. The observed differences in lactic acid concentrations in samples from CF and CP subjects are discussed w ith regard to differences in microbiological composition and possible differences in plaque permeability to sucrose.