Biochemical aspects of calculus formation

In an effort to identify factors responsible for individual variations in the amount and rate of salivary calculus formation, submaxillary and parotid secretions were examined from twenty heavy and twenty light calculus formers. The samples were assayed for total calcium, magnesium and phosphorus and for lysozyme and acid phosphatase activity. Individual and pooled submaxillary and parotid samples from five heavy and five light calculus formers were compared by polyacrylamide disc electrophoresis, immunoelectrophoresis, immunodiffusion and adsorption on hydroxyapatite. Reciprocal adsorption was also carried out on antisera to the submaxillary saliva from the two clinical groups. The mean calcium concentration of submaxillary saliva was significantly higher in heavy calculus formers than light formers. In the group of heavy formers, 75% of the values were above 10 mg%; in light formers, 20%. There were no significant differences in submaxillary magnesium and phosphorus or parotid calcium and phosphorus. Lysozyme activity, but not acid phosphatase was significantly lower in heavy formers, suggesting that alteration of bacterial cell walls can affect calculus formation. The electrophoretic and immunochemical studies strongly suggest that there are no proteins present in saliva of heavy calculus formers that are absent in light formers. There were, however, differences in quantities of the various salivary proteins in different individuals. Although no quantitative differences characteristic of heavy or light calculus formers as a group could be discerned, variation was sufficient to warrant further quantitative study.