Continuous analysis of parotid saliva during resting and short-duration simulated chewing.
Parotid saliva flow is increased by mastication and its composition is also modified. The aim of this work was to clarify the relationships between flow rate, pH and protein concentration, during resting and short-duration simulated chewing, using continuous and fractional saliva collections. Parotid saliva flow rate, pH and protein concentration, as it exits the Stensen's duct, were determined on seven subjects in response to one and 30 ipsilateral jaw clenches. To achieve this, we have developed a system able to collect parotid saliva and to measure continuously flow rate, pH and protein concentration and synchronised to the values at the exit of the duct. With increase in flow rate, pH increased linearly and its protein concentration decreased linearly with the logarithm of the flow rate. With an increase in flow rate from 50 to 500 microl/min, the pH increased from 5.8 to 7.0 and the protein concentration decreased from 1.0 to 0.7 g/l. Measurements made on parotid saliva fractions confirmed the variations in pH and protein concentration with flow rate and showed that alpha-amylase concentration was significantly related to both salivary conductivity and protein concentration. Continuous measurements of salivary flow and composition offer a simple and convenient way to determine the precise relationships between different types of oral stimulation and parotid salivary flow and composition.