Journal of Dental Research, Vol 68, 1323-1327, Copyright © 1989 by International & American Associations for Dental Research Online Journals
The interpretation of CO2 equilibration data to obtain plaque fluid buffer capacities, and comparison with results obtained by titration
G. H. Dibdin and R. P. Shellis
MRC Dental Group, Dental School, Bristol, England.
Titration measurements of pooled plaque fluid buffering capacity (Shellis
and Dibdin, 1988), which showed a broadly defined minimum at pH 7, were
compared with recent curves published by Carey et al. (1988a), which they
obtained by an ultra-micro CO2-equilibration technique and which suggested
a quite different profile, peaking sharply at pH 7.1. When analyzed in a
different, more conventional way, the raw measurements in the latter study
become more consistent with our own results and with earlier findings of
Tatevossian (1977). In particular, we conclude that the peak at pH 7.1 is
an artifact, and that Carey et al. underestimated buffer capacities below
pH 6.4 and above pH 7.4. Rationales for the two modes of analysis are
compared, and possible reasons for the remaining differences between the
re-analyzed CO2-equilibration results and the titration results are
discussed. Suggestions for the improvement of the accuracy of the
CO2-equilibration technique are put forward.
