Calcium and phosphate in human dental plaque and their concentrations after overnight fasting and after ingestion of a boiled sweet.

The concentrations of ionized and total Ca inorganic and total phosphate were determined in the same pooled samples of fluid separated from 24 h plaque collected from volunteers at least 1 h after a mid-morning snack. About half the total concentration of Ca was ionized (1.53 mM, SD 0.73, n = 36). The mean total Ca concentration (2.88 mM, SD = 0.89, n = 34) was about half that reported previously. The inorganic phosphate was in the range reported previously and comprised about 80 per cent of the total pool of soluble phosphate. A small but significant pool of organic phosphate comprised about 20 per cent of the total phosphate. There were no differences in any of these measurements between plaque-fluid samples pooled from upper buccal posterior teeth and from other sites. The product ([Ca ion] X [inorganic phosphate]) in plaque fluid greatly exceeded saturation levels with respect to potential solid phases present at the enamel surface. Five adults provided overnight-fasted dental plaque for one year to examine the effects of ingesting a boiled sweet on the plaque Ca and phosphate when collected 15 min later. There were no significant differences between fasting control and post-sweet levels of plaque-fluid Ca (ionized and total) and phosphate (inorganic and total). In the post-sweet residue, there were lower total phosphate but not Ca concentrations; the variability in these measurements may explain the unexpected depletion of the organic pool of phosphate in the residue.