Fluoride can be delivered from several different fluoride sources. The three most popular sources of fluoride globally, which are all accepted by the US FDA as clinically effective, are:
stannous fluoride (SnF2)
sodium fluoride (NaF)
sodium monofluorophosphate (Na2PO3F)
The efficacy of fluoride as a caries preventive agent depends largely on its concentration and availability in the oral fluids to affect the demineralization/remineralization balance. Over the years, hundreds of clinical studies have been conducted to test the efficacy of fluoride dentifrices in caries prevention. In general, across all fluoride types, these studies show approximately a 25% reduction in caries over a nonfluoridated control dentifrice.22
Stannous fluoride. Stannous fluoride (SnF2; also called tin fluoride) was first formulated successfully into a dentifrice to deliver an anticaries benefit in the 1950s.11,12 Fluoride is highly reactive, and the challenge was finding an abrasive system that had low enough reactivity with fluoride to maintain the bioavailability of the fluoride. The formulation included 0.454% stannous fluoride and the abrasive calcium pyrophosphate; it was marketed as Crest® with Fluoristan® (Figure 2). While stannous fluoride also has the potential to deliver benefits related to the antibacterial properties of the ingredient, this early formulation only delivered an anticaries benefit based on the action of fluoride. In the 1990s, manufacturers developed methods to stabilize stannous fluoride formulations that delivered the antibacterial benefit of the ingredient as well.23,24
Sodium fluoride. Sodium fluoride (NaF) is a fluoride salt commonly used in dentifrices and oral rinses. Sodium fluoride delivers a highly reactive fluoride ion; therefore, formulating it with a compatible abrasive is critically important for achieving the anticaries benefit. The earliest fluoride dentifrices, formulated with NaF and calcium abrasives, provided essentially no anticaries efficacy.25,26 In the early 1980s, silica abrasives that were compatible with sodium fluoride became available and allowed dentifrices with NaF to be developed; these formulas were tested and proven to be clinically effective against caries.27,28
Sodium monofluorophosphate. Sodium monofluorophosphate (SMFP) was introduced into Colgate’s first fluoridated dentifrice and allowed this brand to obtain the ADA Seal of Acceptance for cavity protection in 1968 (Figure 6).29 Unlike sodium fluoride, SMFP is not an ionic fluoride salt, but rather a covalently bound compound that requires enzymatic activation by a salivary enzyme (alkaline phosphatase) to release bioavailable fluoride (Figure 7).30 Because of this lower reactivity, SMFP is compatible with more abrasives than other fluoride sources.29
Colgate® with SMFP.
Figure 7. Enzymatic activation of SMFP.
The covalent bond of SMFP must be broken to release bioavailable fluoride.