Journal of Dental Research, Vol 67, 438-446, Copyright © 1988 by International & American Associations for Dental Research Online Journals
Analysis of the buffering systems in dental plaque
R. P. Shellis and G. H. Dibdin
MRC Dental Group, Dental School, Bristol, United Kingdom.
A semi-micro method was used for investigation of the buffering properties
of whole plaque, plaque fluid, and washed plaque bacteria. Artifacts
associated with titration of samples containing live bacteria were noted
and their effects estimated. All three sample types showed minimal
buffering in the region of neutrality, with much stronger buffering in the
regions pH 4-5.5 and pH 8-9. For the range pH 4-7, almost 90% of the total
buffer capacity of plaque appeared to be accounted for by macromolecules of
bacterial cell walls and plaque matrix. Extracellular buffers in plaque
fluid removable by centrifugation contributed up to 11%. These buffers
(probably soluble proteins, peptides, organic acids, and phosphate) are,
potentially at least, capable of exchange with saliva. In vitro,
bicarbonate (dissolved in the extracellular fluid) contributed only 2-5% of
total buffering; there was no evidence of formation of carbamino compounds.
However, in vivo, salivary bicarbonate may be important as a continually
replenished source of additional buffering.
