Plaque pH and Associated Parameters in Relation to Caries

Abstract

Intensified plaque acidogenicity in caries–prone subjects was reported many years ago, but emerging evidence has suggested that the relationship may not be as strong as once thought. We have now determined a range of acidogenicity variables in subjects having both caries prevalence and incidence data, and have included plaque mineral data in the analysis. pH measurements were made in 20 randomly selected subjects from a high–caries group (mean DMFS = 8.95) and 20 from a caries–free group of Beijing children aged 12 years participating in a caries prediction study. Subgroups with a 12–month DMFS increment ≥2 or = 0 were also formed from the two groups, respectively. Measurements were made with an iridium oxide electrode inserted between teeth 13/14, 23/24, 34/35 and 44/45, before and every 5 min for 30 min after rinsing with 10% sucrose, and the 4 resulting ‘Stephan curves’ averaged using a plaque pH analysis program. Supragingival plaque was collected from buccal and lingual smooth surfaces of posterior and upper anterior teeth and its acid extract analysed for Ca, P and F. Caries–free subjects (based on past experience) had a significantly higher maximum plaque pH and pH value after 30 min (reflecting a faster return to resting pH), a lower minimum enamel dissolution capacity of plaque and recorded less time below pH 7.0 than did high–caries subjects. No other differences were significant, including those of the principal acidogenic parameters ‘minimum pH attained after a sugar rinse’, ‘curve area below the critical pH of 5.5’ and ‘time below the critical pH’. Selection of the caries groups on the basis of both experience and incidence did not reveal significant differences in more parameters. Upper arch plaque was significantly more acidogenic than lower arch plaque, and there was a consistently strong association between upper and lower arch values in individuals. Ca, P and F in the subjects’ plaque had little or no influence on the principal acidogenic parameters. Our failure to find a relationship between caries prevalence or activity and these principal acidogenicity parameters may be related to differences between fissure and smooth surface plaque, temporal variations in acidogenicity and/or to use of F toothpaste during the 1–year observation period. These results support the view that factors such as the frequency of acidogenic episodes may be more important in caries progression than the degree of acidogenicity during any one episode.

Association of polymorphisms in the carbonic anhydrase 6 gene with salivary buffer capacity, dental plaque pH, and caries index in children aged 7–9 years

“…34 Children had been asked not to eat or drink for 3 h before the measurements. The measurement was only performed if the electrode was inserted into the biofilm.…”

Effect of Mild Acid on Gene Expression in Staphylococcus aureus

“…In other words, pH could be one of the factors that determine locale-specific gene expression patterns, since certain body sites are characterized by variations in pH from the homeostatic 7.4 ( Fig. 6) (5,10,16,21,22,31,41,53). Given the breadth of the MAS, plus the fact that the intracellular pH is maintained within very narrow limits, the pH differential must be sensed by one or more surface receptors and transduced to the interior of the cell.…”

Effect of Withdrawal of Fluoride-Containing Toothpaste on the Interproximal Plaque Microflora

“…There is no simple relationship between the concentration of fl uoride ions in plaque and microbial acid production. Vogel et al [2002] reported no correlation between fl uoride levels in plaque and lactic acid formation while Dong et al [1999] also found no differences in the concentration of acidsoluble fl uoride ions in the plaque of caries-free and highcaries groups of subjects.…”