Abstract
The rate of sugar clearance from the mouth would seem to be an important parameter in caries susceptibility. Such clearance is by dilution with saliva and periodic swallowing. A mathematical model of this process has been developed which incorporates a variable salivary flow rate dependent on salivary sugar concentration and in which swallowing is treated as an incomplete syphon. The parameters in the model include the amount of sugar in the mouth at time zero (S), the unstimulated salivary flow rate, the maximum sugar-stimulated flow rate, the delay between taste stimulation and development of a steady stimulated flow rate, the taste theshold for sugar, the sugar concentration in a saturated solution, the volume of saliva in the mouth initially and the volume in the mouth before swallowing (VMAX) and immediately after swallowing (RESID). The most important parameters affecting clearance appear to be the unstimulated salivary flow rate and the volumes of saliva in the mouth immediately before and after swallowing. Surprisingly, the value of S was of lesser importance, mainly because as S increased, so did the stimulated flow rate which increased the rate of clearance. This result is in keeping with the finding of the Vipeholm study that increasing the amount of nonretentive forms of carbohydrate in the diet had minimal effects on caries. The model is of value for assessing the relative importance of the various parameters affecting clearance and may help to account for differences in caries susceptibility between individuals with apparently similar intakes of carbohydrates. This study appears to be the first to identify the importance of RESID and VMAX in salivary sugar clearance.