Hydrogen ion activity in dental plaques of hamsters during metabolism of sucrose, glucose and fructose

Hamsters receiving a high sucrose diet were infected orally with strains of Streptococcus mutans, known to induce dental microbial plaque formation and caries in these animals, or a strain of Odontomyces viscosus, which causes the accumulation of plaque deposits in the gingival sulcus but does not induce coronal caries lesions. Glass micro-electrodes were used to follow the pH changes following the application of concentrated or dilute solutions of sucrose, glucose, or fructose to the plaques in situ. The hydrogen ion activity of Strep. Mutans-induced plaque deposits increased rapidly upon the application of carbohydrate solutions, readily attaining pH values of 5.0 or lower. Plaques formed as a result of O.viscosus infection produced acid at a slower rate and to a lesser extent (minimum pH 5.4, average 6.4). Plaque deposits resulting from the indigenous oral microflora were scanty and produced very little acid (minimum pH 5.8, average 7.0). The amount of carbohydrate applied and the size of the plaque also influenced the rate and extent of hydrogen-ion activity change. Fructose was fermented at a slightly slower rate than glucose or sucrose by the plaques of animals infected with Strep. mutans. However, the relative ability of these carbohydrates to serve as substrates for acid production did not correlate with their reported relative efficacy as cariogenic dietary substrates, indicating that additional factors are involved in the development of caries in the hamster. Des hamsters, soumis á une alimentation riche en saccharose, sont infectés, par voie buccale, á l'aide de diverses espèces de Streptococcus mutans, induisant la formation de plaque dentaire microbienne et des caries chez l'animal, et une espèce d'Odontomyces viscosus, qui provoque des dépôts de plaque dans le sillon gingival, mais n'induit pas de lésions carieuses coronaires. Des microélectrodes de verre sont utilisées pour suivre les changements de pH, consécutifs á l'application aux plaques in situ de solutions concentrées ou diluées de saccharose, glucose et fructose. L'activité en ion hydrogène de plaques formées par Strep. mutans augmente rapidement après application de solutions sucrées, atteignant facilement des valeurs de 5,0 ou plus basses. Les plaques formées par O. Viscosus produisent de l'acide plus lentement et á un degré moindre (minimum pH 5,4, moyenne 6,4). Les dépôts de plaque, formés par la flore buccale endogène, sont rares et produisent peu d'acide (pH le plus bas 5,8, mo