Comparison of Methods for Monitoring Changes in the pH of Human Dental Plaque

Abstract

Changes in human dental plaque pH can be used to obtain estimates of the acidogenic potential of ingested foods. The presence of acid in plaque is influenced by a large number of host, microbial, and substrate factors. Several useful methods have been developed for monitoring changes in plaque pH. Plaque sampling involves repeated removal of small samples of plaque from a number of teeth at intervals after food ingestion, dispersion of the sample, and in vitro measurement of pH. Touch electrode methods utilize glass or antimony microelectrodes, which are placed onto plaque in situ where direct readings can be obtained. Telemetry methods involve placement of glass microelectrodes or ion-sensitive field effect transistors within the dentition. Plaque is allowed to accumulate, and pH changes can subsequently be transmitted with radio or wire. Each of the methods has clear advantages and limitations. The methods have been simultaneously compared in human volunteers using solutions of fermentable carbohydrate. Inter-method differences in response were observed depending upon the site of measurement. Data obtained from caries-prone surfaces via telemetry showed lower pH minima and retarded returns to resting pH levels. The technology is available for controlled comparative plaque pH studies, with the method of choice depending upon the goals of the investigation. It is essential that the results be compared to data obtained with other models designed to evaluate the cariogenic potential of foods.

Counteractive Balancing of Transcriptome Expression Involving CodY and CovRS in Streptococcus pyogenes

“…A common route of GAS infection is invasion through the pharynx (51), where the cells are challenged with environmental fluctuations affecting not only the pH or ionic composition of the mucosal bathing saliva but also the availability of nutrients (9). Food intake is followed by a sharp decline in pH due to acid production by resident oral lactobacilli (49). GAS requires adaptation to effectively compete with the resident flora and initiate the infection process.…”

Food Starches and Dental Caries

“…Different plaque pH methods-such as the "sampling" technique, the touch/microtouch technique, and the indwelling/telemetric method have been used (Harper et a)., 1985b; Lingstrom et )., 1993b). These methods yield pH profiles with different shapes and pH minima (Schachtele and Jensen, 1982;Lingstrbm et a. 1993b).…”

The Effect of Lowering the pH on the Composition and Metabolism of a Community of Nine Oral Bacteria Grown in a Chemostat

“…Although the resting pH of plaque is around neutrality, the pH falls to below pH 5-0 within minutes of the ingestion of dietary carbohydrates (Schachtele & Jensen, 1982), while the pH at the base of a carious lesion is frequently around 4.0, and may be as low as 3.2 (Dirksen et al, 1963). In our study, when the pH fell to pH 4.1, with the exception of L. casei, the viable count of each species fell, although the numbers of S. mutans were less affected than those of other populations, particularly S. sanguis and F. nucleaturn (Table 1, Fig.…”

“…In the aetiology of dental caries, the growth and metabolism of bacteria at low external pH values are of prime importance. These low pH values occur regularly in plaque after the ingestion and metabolism of dietary sugars; for an example, see Schachtele & Jensen (1982). Consequently, we have studied the effect of lowering the pH on the behaviour of a community of oral bacteria growing initially at pH 7.0.…”