On the physicochemistry of plaque calcification and the phase composition of dental calculus.

Abstract

The main constituents of human dental calculus are a carbonate containing apatite and a Mg and Zn containing Whitlockite. A third important component is octocalcium phosphate. If the salivary pH is low enough, human dental calculus can also contain dicalcium phosphate dehydrate. According to the physicochemical model of calculus formation, dental calculus must contain calcite as the main component in animals having a high salivary pH.This hypothesis appeared to be valid for a salivary pH of 8 or higher (dogs, miniature pigs, domestic pigs). The physicochemical model implies that resting plaque has certain periods in which it has a higher pH than the saliva and the crevicular fluid in which it is bathed. Literature data provide evidence of such a higher pH, probably caused by proteolysis resulting in the formation of urea, ammonia, and amines by the plaque bacteria. The importance of this mechanism is supported by the fact that protease activity in saliva and dental calculus index are correlated positively (Watanabe et al. 1982). Finally, the importance of saliva as a source of urea and the application of urea rinses in dentistry are discussed.