Analysis of residual saliva and minor salivary gland secretions.

Residual saliva and minor salivary gland secretions are important for the maintenance of oral mucosal wetness. Salivary proteins and glycoproteins are the major components of the oral mucosal film, which functions as a moisture retainer and a protective barrier. Here, the correlations between the amounts of residual saliva and minor salivary gland secretions and their protein concentrations were investigated in 30 normal healthy individuals. The thickness of the mucosal film was measured at six mucosal surfaces and minor salivary gland secretion rate was measured at two mucosal surfaces. The thickness of residual saliva was determined by placing filter-paper strips against the mucosa at each site for 5 s and then measuring the volume electronically with a Periotron 8000 micro-moisture meter. The unstimulated rate of minor salivary gland secretion was measured for 30 s by the same method. Unstimulated whole salivary flow rate was measured with the spitting method. The total protein concentration of all salivary samples was measured by bicinchoninic acid assay. Before the experiment, the intra-/inter-examiner reliability of the method using the Periotron and the filter-paper strips was investigated. With a range of 0.4256-0.8846, the intraclass correlation coefficient, measured within and between examiners, was indicative of good reliability. The oral mucosal site with the thinnest coat of residual saliva was the anterior hard palate. Mucosal wetness on the hard palate and buccal mucosa showed significant positive correlations with the unstimulated whole salivary flow rate and significant negative correlations with the total protein concentration of residual saliva. Mucosal wetness on the upper and lower labial mucosa also showed significant negative correlations with the total protein concentration of residual saliva. Mucosal wetness on the soft palate was correlated with the minor salivary gland secretion rate (r=0.477, P<0.01). Among the minor salivary glands, the secretion rate of soft palate glands in females showed a significant correlation with the unstimulated whole salivary flow rate (r=0.563, P<0.05) and a significant negative correlation with its total protein concentration (r=-0.525, P<0.05). These data suggested that oral mucosal wetness and minor salivary gland secretions could be influenced by various factors differently according to mucosal sites.