An investigation into the prevalence of Streptococcus mutans in Wistar rats, its relationship to the initiation of dental caries, and the effect upon its presence of the diet fed before weaning

A comparison of the acid-base and aciduric properties of various serotypes of the bacterium Streptococcus mutans associated with dental plaque

Of the 20 strains tested, Strep. mutans Ingbritt (c), LM-7(e), QP50 -1(f) and K-1R(d/g) produced the largest decreases in pH with glucose, sucrose and starch whereas E-49(a), OMZ-61(a), FA-1(b), BHT(b), GS-5(c) and OMZ-176(d/g) produced the least. In the absence of saliva, catabolism of starch was less than catabolism of either glucose or sucrose but, with saliva present, the differences were considerably reduced. The strains varied in ability to accumulate and degrade stored polysaccharide (a means of producing a more acidic pH), but without relation to serotype. No strains showed pH-rise activity with saliva supernatant, sialin or urea but the b serotypes showed pH rise with arginine and lysylarginine . All strains showed activity from endogenous substrates. Aciduricity was determined by assessing the ability to grow on brain-heart-infusion agar adjusted to pH 5.0 to 7.0. All strains grew better at pH 7.0 than 5.0. Among the least aciduric strains were those of b serotype which being among those least able to decrease the pH with fermentable carbohydrate and the only one to raise pH with arginine and arginine peptide, suggested that this serotype might appear more often in caries-free than in caries-active plaques and in plaques showing a less acidic Stephan pH response. The acid-base and aciduric properties of the non-b serotype strains indicated that any one or more of these could be associated with caries-active plaques.

Effect of topically-applied solutions of iodine, sodium fluoride, or chlorhexidine on oral bacteria and caries in rats

Antibacterial levels of iodine, chlorhexidine or sodium fluoride were topically applied to the molar teeth of rats. The effect of these agents on buccal and sulcal caries, as well as on certain oral bacterial populations was assayed. All three agents exerted a significant cariostatic effect which was site specific. Buccal caries incidence and reductions appeared correlated to S. mutans counts, while sulcal caries was better correlated to total cultivable counts. These studies suggested that the simultaneous application of iodine and NaF might exert an additive cariostatic effect.

Sources of variability in rat caries studies: weaning age and diet fed during tooth eruption

A factorial design (2x2) was used to study the caries effect of two diets (starch based versus stock) fed to rat dams and their litters, and also of variations in the weaning age (19 versus 25 days). Higher and reproducible caries scores were obtained in rats which were fed a purified starch-based diet, weaned at 19 days of age, and subsequently given a cariogenic challenge.