The relationship between the biochemical composition of dental plaque from both approximal and free smooth surfaces of teeth and subsequent 3-year caries increment in adolescents.

The biochemical composition of both types of plaque and the subsequent caries increment were investigated in 39 males aged 11-12 years at the time of plaque collection. The calcium concentration of free smooth-surface plaque was inversely related to both total and approximal 3-year DFS increment (p less than 0.01). A relationship between calcium concentrations in approximal plaque and subsequent caries was restricted to the 3-year increment on approximal surfaces (p less than 0.05). There was evidence for a direct relationship between caries increment and both magnesium and organic phosphorus concentrations in plaque on the free smooth surfaces only (p less than 0.05). In contrast, a direct relationship between total caries increment and both total and intracellular carbohydrate concentrations reached statistical significance for approximal plaque only (p less than 0.05). Regression analysis indicated that the combination of the calcium and inorganic phosphorus concentrations of free smooth-surface plaque and the intracellular carbohydrate concentrations of approximal plaque explained 40% of the variation in subsequent caries increment.