**2.1 Salivary clearance from different regions of the mouth**

### **2.1.1 Aim**

Very little research has been carried out on the rates of diffusion of substances into or from dental plaque in vivo. Primosch et al. (1986) studied topical fluoride distribution in the oral cavity and rates of clearance following different methods of dissolution of fluoride tablets. They found that after the chewing, sucking, or passive dissolution of the tablets, fluoride was not evenly distributed in the mouth, and that retention of fluoride was reduced by increased salivary flow rate. Thus, it would seem likely that the rate of renewal of the film of saliva over plaque must influence diffusion rates into and from plaque.

The aim of this study was to determine the velocity of the salivary film by determining the rate of diffusion of potassium chloride from an artificial plaque at different sites in the mouth.
