Relationship between the hexosamines of human saliva and dental plaque

Abstract

Optimum conditions for hydrolysis of submandibular, sublingual, parotid and whole saliva for the estimation of total hexosamine were determined and the Elson-Morgan method adapted for total hexosamine estimation and for estimation of individual hexosamines after column chromatography. Sublingual saliva contained approximately 200 μg total hexosamine/ml, submandibular saliva 15–100 μg/ml, and parotid saliva 50–150 μg/ml. Very little of this hexosamine was lost on incubation with the bacteria of dental plaque. The glucosamine:galactosamine ratio for submandibular saliva was 1.5–4.0 and for sublingual saliva 1.5–2.7. Parotid saliva contained glucosamine almost exclusively, galactosamine being detected only occasionally and in very small quantities. Dental plaque contained 0.3% total hexosamine on a wet weight basis which consisted of glucosamine, galactosamine and muramic acid in the approximate ratios 8:2:1. The muramic acid arises from the bacterial cell walls and the large excess of the other hexosamines indicates that they are present in the plaque matrix, not in the bacteria. It is postulated that the hexosamines of dental plaque arise from the salivary glycoproteins which consist mainly of blood-group substances.