Analysis of residual saliva and minor salivary gland secretions in patients with dry mouth

Abstract

The importance of oral mucosal wetness in the condition of dry mouth and the role of salivary proteins in proper oral function are acknowledged. A negative correlation between mucosal wetness and the protein concentration of residual saliva has been reported in normosalivators. Here, to examine the suggestion that a reduction in residual salivary volume leads to a concomitant elevation of its protein concentration, the amount of residual saliva and minor salivary gland secretions, and their protein concentrations, were measured in hyposalivators and normosalivator controls. A Periotron 8000® micro-moisture meter was used to measure the thickness of the mucosal film at six selected mucosal surfaces and the minor salivary gland secretion rate at two mucosal surfaces. The unstimulated whole salivary flow rate was measured by the spitting method. The total protein concentration of all salivary samples was measured by bicinchoninic acid assay. The hyposalivators had significantly lower amounts of residual saliva and minor salivary gland secretions than the normosalivators at all selected mucosal sites except the soft palate. In both groups, the site with the thinnest coat of residual saliva was the anterior hard palate and the wettest site was the anterior dorsal mucosa of the tongue. The protein concentration of residual saliva was significantly higher in hyposalivators than normosalivators. In the minor salivary gland secretions there was no significant difference in protein concentration between the normo- and hyposalivators. When the hyposalivators were divided into two subgroups according to their severity of dryness, the reduction of residual salivary volume and the elevation of protein concentration were more apparent in the group with the more severe dry mouth. Collectively, these results indicate that oral mucosal wetness is associated with the flow rate of unstimulated whole saliva. The function of the minor salivary glands was less affected and relatively well preserved in patients with dry mouth. The increased protein concentration of residual saliva in the hyposalivators appeared to be the result of decreased salivary volume.