The flow rate of unstimulated human labial gland saliva

Although the minor salivary glands contribute an important fraction of the resting flow of saliva, which may be particularly relevant in xerostomia, there is currently no precise method of measuring the flow from individual glands or recording the number of active glands in a given area. These experiments were devised to test a photographic method of assaying labial gland saliva and to see whether subjects of different ages had differing flow rates and/or numbers of glands. Unstimulated saliva secretion from labial salivary glands was measured in healthy non-medicated subjects aged 20 to 55 years by a photographic method. The number of glands in a unit area, the individual gland flow rates, and the flow rates per unit area were assessed. There was a high correlation between flow rate per unit area as measured by this method and measurements from weighing filter paper before and after absorption of the saliva droplets when the latter method could be used. The mean flow rate for 22 subjects was 2.35 +/- 1.65 microL/min over the whole area photographed. Subjects with higher flow rates had both more active glands and a higher rate of secretion from individual glands. There was no correlation between either number of active glands in a unit area or of flow rate and age in the age range represented by these subjects.