Buffering Capacity in Human Dental Plaque Fluid

Abstract

The buffering capacity was determined in the extracellular aqueous phase of 24-hour plaque samples obtained from dental students. The mean pH of five control samples of plaque fluid was 6.54 ± 0.26 SD. In the range pH 6–5, the mean buffering capacity was 3.2 × 10^––4 mol ΔaH⁺/mol H⁺ added while in the range pH 5–4 it was 1.8 × 10^––3 mol ΔaH⁺/mol H⁺ added, indicating a reduction in buffering at the lower pH range. Buffering between pH 5 and pH 4 was essentially reversible, while between pH 6 and pH 5, it was associated with the irreversible loss of a component which precipitated out. Buffering above pH was also associated with the irreversible loss of a component. It was concluded that at least three buffer components occur in plaque fluid and that rinsing with deionised water reduced the buffering capacity in plaque fluid.

Composition of Human Plaque Fluid

“…Clearly, the calculated titration curve is in reasonable agreement with the experimental points; consequently, most of the buffer capacity of the PF is here ascribed to the presence of carboxylic anions. The buffer capacity of the PF in the titration range, expressed as the number of moles of strong acid required to lower the pH value from 5.0 to 4.0, was 12.8 nmol of H+/mg wet plaque weight, assuming PF to be 35% of the wet plaque weight (Jenkins, 1966;Edgar and Tatevossian, 1971); this is in good agreement with the value reported by Tatevossian (1977). The correspondence between the experimental points and the calculated curve, shown in Fig.…”

“…The correspondence between the experimental points and the calculated curve, shown in Fig. 2, does not preclude the contribution of other constituents, such as proteins and polyamines, known to exist in the PF (Tatevossian and Newbrun, 1981;Vratsanos and Mandel, 1985); in this respect, we observed that the fluid became cloudy at a pH value of 4.38, most probably due to the precipitation of proteins, as suggested by other investigators (Tatevossian, 1977). Nevertheless, the contribution of other constituents, different from the organic acids, to the buffer capacity of the PF appears to be minor.…”

“…Comparison of the buffer capacity of PF reported here and by other investigators (Tatevossian, 1977) with those reported for whole plaque (Stralfors, 1950) indicates that the former is much smaller (by a factor of about four). In a previous investigation (Rankine et al, 1985), it was pointed out that there were increases in the calcium and phosphorus concentrations of the plaque fluid in situ, when rinsed with sucrose solutions, and that the enhancement of those concentrations was consistent with the presence of a solid phase in plaque containing those two elements.…”

The Interpretation of CO2 Equilibration Data to Obtain Plaque Fluid Buffer Capacities, and Comparison with Results Obtained by Titration

“…This is the pattern we observed by titration (Shellis and Dibdin, 1988); Tatevossian (1977) and Margolis et al (1988) have recorded similarly shaped acid titration profiles between the initial pH and pH 4. Since the data of Carey et al cover a restricted pH range, little can be deduced from their data about the buffering/pH profile.…”

Diffusion of Radio tracers in Human Dental Plaque

“…For this reason, the sodium salts of the solutes were used throughout this series. Variations in the degree of dissociation of these solutes in plaque fluid at pH 6.5 ± 0.3 [Tatevossian, 1977] appear not to be the relevant factor in these studies.…”