Early Stannous Fluoride Formulations

More than 50 years have now passed since it was definitely established that fluoride in drinking water prevents caries in children. The next significant preventive breakthrough came when it was shown that fluoride can provide topical, as well as systematic, benefits in combating dental decay. Sodium fluoride was the first topically applied fluoride compound to be tested. Primarily through the efforts of Muhler and his associates at Indiana University in the early 1950s ( e.g.., J Dent Res 33:33 <ETH> 49, 1954 ) stannous fluoride became the second topical agent to gain wide professional acceptance. The element tin or stannum (Latin ) and its reactive ionic form, stannous, are occasionally used interchangeably in the dental literature.

Stannous fluoride (SnF2 ) was selected from a large number of fluoride salts, including lead, iron, zirconium and potassium fluoride, that were tested for their effect on reducing enamel solubility. In laboratory experiments, the presence of the stannous ion with fluoride produced an enamel surface that was less acid soluble than surfaces treated with other fluoride compounds, including sodium fluoride.

Initial in-office treatments involved the use of solutions containing 8-10 percent stannous fluoride. Although clinically effective, high concentration stannous fluoride solutions were found to have some major disadvantages. The solution becomes cloudy soon after mixing due to the formation of tin hydroxide. The preparation also has an astringent taste that many patients find difficult to accept. Pigmentation of teeth following topical application has also been reported. A brown discoloration occurred occasionally in "white spot" lesions, in plaque, and around the margins of some restorations. For these reasons, in-office application of 8-10% stannous fluoride was superseded by 1.23% acidulated phosphate fluoride (APF) and 2% neutral sodium fluoride topical gels. An analysis of the results of anticaries trials involving these three agents, however, shows equivalent effectiveness.

Although less fluoride is deposited on tooth surfaces with stannous fluoride than with either sodium fluoride or APF topicals, several tin compounds are formed ( e.g., tin oxides, tin hydroxyphosphate and tin fluorophosphate ) which may explain reduction effect of stannous fluoride systems. The fact that stannous fluoride reacts differently with enamel than do APF solutions led to a rebirth in stannous fluoride office use in the early 1970s. Investigators found that the use of a combination rinse containing both APF and SnF2 solutions effectively enhanced fluoride retention on treated tooth surfaces. Currently, several manufacturers offer this combination office rinse containing 0,31% APF and 1.64% SnF2 for use following root scaling and as an alternative to topical gels.