The effect of cadmium on the normal tooth fissure plaque flora of Sprague-Dawley rats

Root surface caries subsequent to gingivectomy in rats inoculated with Streptococcus sobrinus (mutans) and Actinomyces viscosus

We studied the effect of oral infection with cariogenic micro-organisms on alveolar bone loss and root surface caries subsequent to gingivectomy in rats. Thirty-six rats were fed diet MIT 200 (67% sucrose); one-half, the controls, had antibiotics added to the diet. At ages 18, 19, and 21 days, the experimental group was orally infected with streptomycin-resistant Streptococcus sobrinus (mutans) 6715 and Actinomyces viscosus M-100. At age 30 days, all animals were subjected to a gingivectomy on maxillary and mandibular left quadrants. The experimental group was re-inoculated at age 36 days. Animals were killed seven weeks after surgery. Jaws were stained, and planimetric measurements of exposed root surface area and caries on lingual/palatal surfaces of 1st and 2nd molars were made from video images with a computer/digitizer. Compared with the non-operated contralateral quadrants, gingivectomy significantly increased exposed root surface area in the maxilla and in the mandible in both the control and experimental groups. Oral inoculation significantly increased exposed root surface in mandibular (but not maxillary) quadrants which had received a gingivectomy, but had no effect on non-gingivectomized quadrants. There was no caries in the control group, whereas ten rats in the experimental group had root surface caries lesions, all in quadrants which had received a gingivectomy. This rat model should prove useful in further studies of root surface caries.

The effects of cadmium on the growth of some oral microorganisms and their ability to bind cadmium

All seven oral Actinomycetaceae tested grew in broth containing 10 microgram/ml Cd. After 24 hours' growth A viscosus WVU 626 bound nearly 20 microgram Cd/mg dry wt. The amount of Cd bound varied during the growth cycle, being maximal (90 to 100 microgram/mg dry wt.) after 5 hours' growth. Addition of 50 microgram/ml chloramphenicol to actively growing cells inhibited further Cd binding. In contrast S mutans FA1 was greatly inhibited by 2.5 microgram/ml Cd and bound only 1.3 microgram Cd/mg after 24 hours' growth in broth containing 2.5 microgram/ml Cd.

The effects of fluoride on the percentage bacterial composition of dental plaque, on caries incidence, and on the in vitro growth of Streptococcus mutans, Actinomyces viscosus, and Actinobacillus sp

Administration of 250 mug/ml NaF in drinking water to rats reduced both caries incidence (P less than 0.001) and the percentage of S mutans (0.01 greater than P greater than 0.001) although the percentage of Actinobacillus sp. was increased (P less than 0.001). An Actinobacillus sp. and S mutans FA1 both proliferated in NaF broth only if the NaF greater than 10 mug/ml, which was associated with the inhibition of acid production.