Studies on Dental Plaque. I. The Effect of Different Concentrations of Glucose on the pH of Dental Plaque in Vivo

¹ Department of Biochemistry, University of Manitoba, Winnipeg, Canada

The effect of different concentrations of glucose on the pH obtained in saliva-glucose mixtures on incubation for 24 hours has been studied. With increasing concentrations of glucose, a greater pH fall was produced until a maximum was reached at approximately 5 per cent, but, with progressively higher glucose concentrations, this pH fall became progressively less.

By the local application of glucose to selected plaque areas in situ, the effects of different glucose concentrations under various conditions on the pH of these plaques were studied. Under these conditions, the results clearly pointed to a cause-and-effect relationship between the presence of glucose and the pH fall in these plaques; i.e., adding glucose caused a pH fall, while removing the added glucose gave a pH rise.

When glucose was added continuously over a period of time, the fasting steady-state pH was disturbed to a new lower level, this level being determined by the concentration of the glucose added. Increasing the glucose concentration resulted in a corresponding decrease in the pH level of the new steady state until a maximum decrease was obtained with a concentration of 5 per cent. With a glucose concentration of 50 per cent, the pH level of the steady state was raised. The possible reasons for this inhibition at high glucose concentrations, as in vitro, were discussed, along with the above observations in relation to the properties and kinetics of these systems.

When the glucose concentration was allowed to decrease from various initial levels, it was found that as the glucose concentration fell, the plaque pH also fell at first but then rose as the glucose concentration fell still further. If during this fall the glucose concentration remained above a certain critical level for a long enough time, the pH minimum could be reached. It was pointed out that the longer the glucose concentration during its fall was above this critical level, the longer the plaque could be at its minimum pH value.

A method based on observations made in the present study was suggested for studying the effect of a given substance on the metabolism of the acidogenic bacteria in a given dental plaque at different pH levels in vivo.

This article has been cited by other articles:

				I. Kleinberg A MIXED-BACTERIA ECOLOGICAL APPROACH TO UNDERSTANDING THE ROLE OF THE ORAL BACTERIA IN DENTAL CARIES CAUSATION: AN ALTERNATIVE TO STREPTOCOCCUS MUTANS AND THE SPECIFIC-PLAQUE HYPOTHESIS Crit. Rev. Oral. Biol. Med., March 1, 2002; 13(2): 108 - 125. [Abstract] [Full Text]