Journal of Dental Research, Vol 69, 1332-1336, Copyright © 1990 by International & American Associations for Dental Research Online Journals
Plaque fluid as a bacterial milieu
W. M. Edgar and S. M. Higham
School of Dentistry, University of Liverpool, England.
Studies of the extracellular, free concentrations of substrates, growth
factors, inhibitors, and end-products of metabolism to which the intact
plaque microflora is exposed in situ can assist in the understanding of
factors controlling plaque pathogenicity. Information is becoming
increasingly available from analysis of fluid separated by centrifugation
of plaques collected at various intervals after an intra-oral pulse of
dietary or experimental substrate, or different procedures or treatments
having cariostatic potential. Such analytical results give more information
than those obtained by analysis of aqueous or other extracts, because they
yield values of substrate concentration representing those occurring at the
bacterial cell surface. The largest body of information concerns
extracellular levels of acid end-products of sugar catabolism in relation
to food quality or sequence, and of amino acids and other products of
nitrogen metabolism, in relation to studies of the detailed metabolic
events of the Stephan curve, and of the demineralizing effect of the plaque
environment. Areas where little information is available and which merit
further study include plaque clearance of salivary and other components
with anti-caries activity (e.g., antibodies, enzymes, fluorides, cations,
other antimicrobials, etc.), and substrate concentrations to determine
gradients for diffusion into and out of plaque.
