Stannous fluoride

Stannous fluoride is used in toothpastes and dental rinses to protect tooth enamel from attack by bacteria—cavities (also known as dental caries). It was the first fluoride used for that purpose, in the toothpaste Crest. 

Stannous fluoride (STAN-us FLOR-ide) is a lustrous, white crystalline solid with a salty and bitter taste. The only application of any consequence for stannous fluoride is as an additive in toothpastes. Its function is to strengthen tooth enamel and reduce the rate of tooth decay. 

Stannous flouride. Green atoms are tin and turquoise atom is flourine. publishers 

Stannous fluoride is made commercially by reacting stannous oxide (SnO) with hydrofluoric acid (H2F2) in an oxygen-free environment. 

The primary use of stannous fluoride is in toothpastes, dental rinses, and fluoride treatments for teeth. Fluorides prevent tooth decay in two ways. First, fluorides kill bacteria that cause tooth decay. Second, fluorides react with other chemicals in the mouth to make new enamel to replace enamel destroyed by bacteria or worn away by mechanical processes. Studies suggest that stannous fluoride also has other beneficial effects, including preventing gingivitis (inflammation of the gums) and bad breath. 

Stannous fluoride does have some disadvantages as an additive in tooth care products. For example, it has a somewhat bitter and unpleasant taste. Today, a number of 

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Tm II)fiuoride, Snp2, stannous fluoride. M.p. 213°C. Formed from Sn and aqueous HF. Forms complexes, e.g. MSnFj. Used in toothpastes. 

The main binary tin fluorides are stannous fluoride and stannic fluoride. Because the stannous ion,, is readily oxidized to the stannic ion,, most reported tin and fluorine complexes are of tin(IV) and fluorostannates. Stannous fluoroborates have also been reported. 

Stannous fluoride [7783-47-3] Snp2, is a white crystalline salt that has mp 215°C (1), bp 850°C, and is readily soluble in water and hydrogen fluoride. At 20°C stannous fluoride dissolves in water to a concentration of 30—39% in anhydrous hydrogen fluoride to 72—82% (2—4). 

The pH of a freshly prepared 0.4% solution of stannous fluoride is between 2.8 and 3.5. Initially clear aqueous solutions become cloudy on standing owing to hydrolysis and oxidation. The insoluble residue is a mixture containing stannous and stannic species, fluoride, oxide, oxyfluorides, and hydrates. 

Stannous fluoride probably was first prepared by Scheele in 1771 and was described by Gay-Lussac and Thenard in 1809. Commercial production of stannous fluoride is by the reaction of stannous oxide and aqueous hydrofluoric acid, or metallic tin and anhydrous hydrogen fluoride (5,6). Snp2 is also produced by the reaction of tin metal, HP, and a halogen in the presence of a nitrile (7). 

Stannous fluoride is used in dentifrices and dental preparations. The OSHA permissible exposure limit (44) and ACGIH (45) estabUshed TLV for fluoride is 2.5 mg/m of air. 

Of the large volume of tin compounds reported in the Hterature, possibly only ca 100 are commercially important. The most commercially significant inorganic compounds include stannic chloride, stannic oxide, potassium staimate, sodium staimate, staimous chloride, stannous fluoride, stannous fluoroborate, stannous oxide, stannous pyrophosphate, stannous sulfate, stannous 2-ethyUiexanoate, and stannous oxalate. Also important are organotins of the dimethyl tin, dibutyltin, tributyltin, dioctyltin, triphenyl tin, and tricyclohexyltin families. 

Halides. The tin haUdes of the greatest commercial importance are stannous chloride, stannic chloride, and stannous fluoride. Tin hahdes of less commercial importance are stannic bromide [7789-67-5], stannic iodide [7790-47-8], stannous bromide [10031-24-0], and stannous iodide [10294-70-9] ( ) ... 

The principal commercial use of stannous fluoride is in toothpaste formulations and other dental preparations, eg, topical solutions, mouthwash, chewing gum, etc, for preventing demineralization of teeth (21—23) (see Dentifrices). 

Other studies of the toxicity of stannous fluoride, sodium pentafluorostannite, sodium pentachlorostannite, sodium chlorostannate, stannous sulfide [1314-95-0] stannous and stannic oxides, stannous pyrophosphate [15578-26 ] stannous tartrate [815-85-0] and other inorganic tin compounds are reviewed in References (dh—12. The OSHA TLV standard for inorganic tin compounds is two milligrams of inorganic tin compounds as tin per cubic meter of air averaged over an eight-hour work shift (47). 

Eluoride added to a compatible dentifrice base at a level of 1000 ppm has been clinically proven to reduce the incidence of dental caries by about 25% on average, even in areas where the water supply is fluoridated (4). Elevation to 1500 ppm increases the protection. Sources of fluoride approved for use in dentifrices are sodium fluoride [7681-49-4] (0.22%), sodium monofluorophosphate (0.76%), and stannous fluoride [7783-47-3] (0.41%). The Eood and Dmg Administration regulates fluoridated dentifrices as dmgs and has estabUshed parameters for safe and effective products. CompatibiUty of the fluoride with the abrasive is an important requirement. 

Chelation control was postulated for the reaction between 2,3-[isopropylidenebis(oxy)] propanal and allyl iodide/stannous fluoride which proceeded with useful erythro selectivity92. 

The most recognized toothpaste ingredient is probably the class of compounds known as fluorides. Stannous fluoride was the first to be used in toothpaste because, unlike sodium fluoride, it did not lose its effectiveness when combined with the abrasive most common at the time, calcium phosphate. Later, sodium mono-fluorophosphate came into popular use because it too could be used with the common abrasives. 

Stannous fluoride can be used with abrasives that contain calcium, which prevents sodium fluoride from being effective. Sodium monofluorophosphate was developed to avoid infringing on the Crest patent. 

The active part of the molecule is the fluoride ion, which is why two other fluorine-containing compounds, stannous fluoride (tin fluoride) and sodium monofluorophosphate, are also used. 

An unfortunate characteristic of early zinc polycarboxylate cements was the early development of elastomeric characteristics- cobwebbing -in the cement pastes as they aged, thus shortening working time (McLean, 1972). Improvements in cement formulation, the addition of stannous fluoride to the oxide powder (Foster Dovey, 1974, 1976) and modifications in the polyacid have eliminated this defect. However, the cements have to be mixed at quite a low powder/liquid ratio, 1 -5 1 0 by mass, when used for luting. 

Chamberlain Powers, 1976 Jendresen Trowbridge, 1972). The addition of stannous fluoride to the cement increases dissolution, but this is an advantage rather than a disadvantage, for the fluoride released is taken up by neighbouring enamel (Bitner Weir, 1973). 

The most important modification of these materials was the discovery of the effect of adding stannous fluoride (Foster Dovey, 1974, 1976). Originally added to provide fluoride release, it was found to improve the mixing qualities of the cement and to increase strength by about 50 %. This is reflected also in improved adhesion to enamel and dentine (Section 5.7.4). 

Foster, J. F. Dovey, E. H. (1974). Surgical cements of improved compressive strength containing stannous fluoride and polyacrylic acid. US Patent 3,856,737. 

Fluoride is found in some zinc phosphate cements, generally as stannous fluoride. The cements are weaker and have less resistance to dissolution than normal zinc phosphate cements (Myers, Drake Brantley, 1978 Williams et al., 1979). They release fluoride over a long period (de Freitas,... 

Gursin, A. V. (1965). A study of the effect of stannous fluoride incorporated in a dental cement. Journal of Oral Therapeutics and Pharmacology, 1, 630-6. 

Skibell, R. B. Shannon, I. L. (1973). Addition of stannous fluoride to orthodontic cement. International Journal of Orthodontics, 11, 131-5. 

Wei, S. H. Y. Sierk, D. L. (1971). Fluoride uptake by enamel from zinc phosphate cement containing stannous fluoride. Journal of the American Dental Association, 83, 621—4. 

In another study, oscillating rheometry was used to examine the effect of adding various simple metal salts to glass-ionomer cements (Crisp, Merson Wilson, 1980). It was found that cement formation for certain glasses which react only slowly with poly(acrylic acid) could be accelerated significantly by certain metal salts, mainly fluorides such as stannous fluoride and zinc fluoride. Some non-reactive glasses could be induced to set by the addition of such compounds. 

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