Composition and buffer capacity of pooled starved plaque fluid from caries-free and caries-susceptible individuals

The composition of pooled starved plaque fluid from six population samples, grouped according to age (8-11, 12-16, 8-17, 18-22 years) and caries status (caries-free, CF, DMFS = 0; caries-susceptible, CS, DMFS greater than 10), was determined by means of ion chromatography. Prior to plaque collection, all subjects abstained from oral hygiene for 48 hours and fasted overnight. In addition, selected subjects also received a dental prophylaxis one week prior to plaque collection. Plaque samples from each group were pooled under mineral oil and centrifuged at 15,000 g (ambient temperature) for 45 minutes. Supernatants were then analyzed for organic acids, inorganic anions, and mono- and divalent cations. Plaque fluid samples from CF and from the CS subgroups were also titrated with standard HCl for exploration of the inherent buffer capacity. The ions Na+ NH4+, K+, Ca2+, Mg2+, Cl-, phosphate, and carbonate were present in all samples analyzed. Formic, acetic, propionic, butyric, and trace amounts of isobutyric and isovaleric acids were detected, with acetic and propionic acids comprising between 85 and 94% of the total acids. Little (less than 1 mmol/L) to no succinic or lactic acid was detected in starved plaque fluid. No apparent difference was detected in the composition and saturation status of pooled starved plaque fluid from CF and CS individuals. These results suggest that caries susceptibility is not necessarily correlated with the plaque fluid composition of pooled starved plaque. In addition, no apparent difference in the inherent buffer capacities of these samples could be detected, consistent with the noted similarities in composition.(ABSTRACT TRUNCATED AT 250 WORDS)