The composition of the aqueous phase in human dental plaque

Abstract

Plaque fluid was separated from plaque collected from dental students. The mean values found in plaque fluid ± S.D. were: Na 35.1 mM ± 9.0, K 61.5 mM ± 13.5, Ca 6.5 mM ± 2.1, Mg 3.7 mM ± 1.1, Pi 14.2 mM ± 3.1, total carbohydrate (glucose) 13.9 mM ± 2.3, protein 1.49 g% ± 0.06, aF − 2.0 μM ± 0.7, pH 6.54 ± 0.26. All parameters (H + and F − excepted) were at a higher concentration in plaque fluid than in saliva or (Na excepted) gingival fluid. Two possible mechanisms for maintaining the higher plaque concentrations relative to saliva, in an open system, are discussed. The major free amino acids in plaque fluid are glutamate, aspartate and alanine. “Ammonia” is present at about 18 mM. It is concluded that the chemical composition of the plaque fluid is different from that of saliva, gingival fluid and bacteriological nutrient media which are used to study plaque organisms in vitro. The method is readily applicable to in-vivo plaque studies on the permeability and retention of substances with a therapeutic potential and in-vitro studies on the composition and properties of plaque fluid.