Association of free arginine and lysine concentrations in human parotid saliva with caries experience.

We determined the free-amino acid content of stimulated parotid (ductal) saliva from two groups of adult subjects whose caries experiences were markedly different. The levels of free arginine and free lysine in the parotid saliva of caries-free adults were significantly higher than those found in the parotid saliva of individuals with a history of dental decay. There was no correlation, however, between the levels of these amino acids and the DMFS score within the caries-susceptible groups. Microbial catabolism of dibasic amino acids contributes to the neutralization of plaque acids and may partially account for the higher resting plaque pH observed in caries-free subjects. Alternatively, the elevations observed in free levels of arginine and lysine may reflect a systemic alteration in amino acid metabolism which is common to the caries-free group of subjects.