A double-blind, crossover design study was performed on 29 young adults to test the effectiveness of 0.1% SnF2 mouthrinse (250 ppmF-) on plaque formation using clinical and microbiological criteria. Participants were assigned to either a placebo or SnF2 rinse which was used twice daily for 5 days. After an interim recovery period of 2 days, the participants used the alternate rinse in a similar manner for another 5 days. Clinical data collected at the end of each experimental period included Gingival Index (GI), and plaque scores. Supragingival plaque removed from each subject at the end of the experimental periods was weighed and then microbial enumeration was performed. Results showed that after SnF2 rinses, there were statistically significant reductions (P < 0.01) in plaque wet weight, number of bacteria per milligram plaque (CFU/mg), and total number of bacteria per sample (Total CFU). Visual plaque scores (PS) showed a significant (P < 0.05) but small reduction as a result of SnF2 rinse. No significant difference in gingival inflammation was noted. It is apparent from this study that, besides the well-documented ability of SnF2 to increase the resistance of teeth to demineralization, this agent is capable of reducing plaque formation. Long-term studies are indicated to examine usefulness of SnF2 in the control of early periodontal disease.

The growth of bacteria on stainless steel wires was used as a model to investigate which properties of SnF2 produced anti-bacterial effects against S. mutans. Wire-adherent bacteria were exposed for one min, twice a day, to various fluoride or control compounds having similar ions, pH, valence, or atomic weights. After two days, the thickness of adherent bacteria was scored visually, and the decrease in pH of the growth medium was determined. Bacteria from each wire were then dried, weighed, and analyzed for metal content. Electron microscopy and electron microprobe were used to identify the location of heavy metal deposits in the bacteria. Only SnF2 dramatically altered S. mutans growth and metabolism, and this anti-bacterial effect was associated with a large uptake of tin into the bacterial cells. The fluoride salts of sodium, lead, zinc, and copper had little influence on S. mutans growth in this test system. The pH of the various fluoride salts or controls generally had no effect on the activity of the test compounds, except for the noted inactivation of SnF2 at elevated pH's. Since SnF4 did not alter the growth or metabolism of S. mutans, a unique property of SnF2--possibly the reactivity in an aqueous environment--may be responsible for its anti-bacterial properties.

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A clinical study was conducted on four adults to compare the relative efficacy of 0.2% chlorhexidine digluconate and 0.1% stannous fluoride (SnF2). Using a crossover experimental design, subjects rinsed twice daily for 5 days with SnF2 and then, after a 2-day interim recovery period, for 5 days with chlorhexidine. Statistically significant differences (P less than 0.05) in the relative efficacy of the two agents were found. Chlorhexidine was more effective in reducing Gingival and Plaque Indices, plaque wet weight and bacterial Colony Forming Units, calculated both per subject and per group.

Twenty-two adults, considered to have high caries activity, rinsed for one yr with either SnF2 or acidulated NaF mouthrinses. Total colony-forming units and numbers of S. mutans and lactobacilli were estimated from saliva samples. Large reductions were found in the number of recoverable S. mutans in subjects rinsing with SnF2 but not in the NaF group.