The role of human salivary acidic proline-rich proteins in the formation of acquired dental pellicle in vivo and their fate after adsorption to the human enamel surface.

The pellicles formed on fragments of human dental enamel worn on a palatal appliance for 1 min to 24 h were removed by acid extraction and the total amounts of protein and of acidic proline-rich proteins were determined. The percentage of total extracted protein constituted by the proline-rich proteins increased during the first hour of formation to about 37 per cent. Little difference was seen in total proline-rich protein between pellicles formed in a 1 and a 24-h period, but there was a gradual degradation of the proteins. There was no preferential retention of the N- or C-terminal parts of the proteins. Extracts of old acquired dental pellicle contained less than 0.1 per cent proline-rich proteins and pellicles more than 24 h old showed degradation of the adsorbed proline-rich proteins; there is no indication that the N-terminal part which contains the known biological activities was retained to a greater extent than the C-terminal part.