“…Tin and lead are exam ples of ions with a strong solubility-reducing effect on the enamel in vitro which, howev er, does not seem to lead to any appreciable caries reduction in animal or clinical experi ments with the possible exception of some SnF2 applications. Regarding stannous fluo ride, a 33-43% caries reduction was achieved in a fluoridated community by dai ly mouthrinsing for 2 years [Radike et al, 1973], Houwink et al [1974] found a caries reduction by treatment twice a year with a 4% SnF, solution for 9 years. Caries reduc tions of about 25% were obtained in 2-to 3-year studies with SnF2 dentifrices [Slack et al, 1971, Fanning et al, 1968Zacherl, 1972].…”