Determination of volumes of fluid in the mouth by fluoride dilution

A dilution technique, with fluoride as a marker, has been developed to measure the volume of saliva and other fluids in the mouth. Immediately after swallowing, a small amount of fluoride solution is placed in the mouth, mixed with the oral fluids, and expelled from the mouth. The fluoride concentration of the expelled oral fluid is measured and the volume of fluid in the mouth at the time of spitting calculated from the fluoride dilution. Mean values of 0.75 +/- (SD) 0.28 ml for males and 0.72 +/- (SD) 0.16 ml for females were recorded. The accuracy of the volume determination is about +/- 0.10 ml in vivo. This technique has provided a convenient and rapid means of determining saliva volumes. It could also be used to determine rates of secretion and may prove useful in the clinic for assessing a patient's salivary competence.