Monofluorophosphate, sodium

A number of salts of the monofluoro- and hexafluorophosphoric acids are known and some are commercially important. The salts of difluorophosphoric acid are typically less stable toward hydrolysis and are less well characterized. Sodium monofluorophosphate [7631-97-2] the most widely used dentifrice additive for the reduction of tooth decay, is best known (see Dentifrices). Several hexafluorophosphates can be prepared by neutralization of the appropriate base using hexafluorophosphoric acid. The monofluorophosphates are usually prepared by other methods (57) because neutralization of the acid usually results in extensive hydrolysis. 

The monofluorophosphates can be prepared by neutralization of monofluorophosphoric acid (1). Sodium monofluorophosphate [7631 -97-2] is prepared commercially (57) by fusion of sodium fluoride and sodium metaphosphate, and the potassium monofluorophosphate [14104-28-0] can be prepared similarly. Insoluble monofluorophosphates can be readily prepared from reaction of nitrate or chloride solutions with sodium monofluorophosphate. Some salts are prepared by metathetical reactions between silver monofluorophosphate [66904-72-1] and metal chlorides. 

They readily dissolve metal oxides and are effective metal surface cleaners and fluxes (see Metal surface treatments). They also have bactericidal and fungicidal properties (74). However, the main commercial appHcation among monofluorophosphates is of sodium monofluorophosphate ia dentifrices. 

Sodium monofluorophosphate, mp 625°C, is soluble ia water to the extent of 42 g/100 g solution. The pH of a 2% solution is between 6.5 and 8.0. Dilute solutions are stable indefinitely ia the absence of acid or cations that form iasoluble fluorides. 

Sodium monofluorophosphate is used ia most dentifrices at a concentration of 0.76 wt % which produces the desired fluoride level of 1000 ppm although one extra strength dentifrice has 1.14 wt % and 1500 ppm F. Although the mechanism of its efficacy ia reducing dental decay is not completely understood (75), it almost certainly reacts with the apatite of the tooth converting it to fluoroapatite which is less soluble ia mouth acids (see Dentifrices). 

The JnitedSfates Pharmacopeia (76) specifications for sodium monofluorophosphate require a minimum of 12.1% fluoride as PO F (theoretical 13.2%) and a maximum of 1.2% fluoride ion reflecting unreacted sodium fluoride. Analysis for PO F is by difference between total fluoride ia the product less fluoride ion as determined by a specific ion electrode. The oral LD q of sodium monofluorophosphate ia rats is 888 mg/kg. 

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. 

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

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. 

Daily doses studied have ranged from 9 to 22.6 mg of fluoride over time periods of 1-4 years [98]. These trials were particularly concerned with the use of slow-release NaF [112,113] or sodium monofluorophosphate preparations [114,115], and they generally led to reductions in the incidence of bone fracture, as shown in Table 3. In addition, they typically caused increased bone density at the neck of the femur, the femoral condyle and the lower spine [98] (Table 3). 

G. Silverman, The sensitivity reducing effect of brushing with a potassium nitrate-sodium monofluorophosphate dentifrice, Compend. Contin. Educ. Dent. 6 (1985) 131-133. 

J.Y. Reginster, L. Meurmans, B. Zegels, C. Gossete, The effect of sodium monofluorophosphate plus calcium on vertebral fracture rate in postmenopausal women with moderate osteoporosis. A randomized, controlled trial, Ann. Intern. Med. 

Anticavity toothpaste for sensitive teeth Sodium monofluorophosphate Sensodyne cool gel Cellulose gum Aqueous... 

The addition of fluoride ions to domestic water supplies (by addition of NaF) is now widespread and has resulted in a dramatic decrease in dental cavities. Fluoridated toothpastes, containing either tin(II) fluoride or sodium monofluorophosphate (MFP, Na2FP03), are also recommended to strengthen tooth enamel. 

Fluoride is a potent stimulator of trabecular bone formation. Sodium monofluorophosphate was given to 48 patients with osteoporosis due to glucocorticoids (more than 10 mg of prednisone equivalents/day). Patients were randomly allocated to 1 g of calcium carbonate (control) or 200 mg of sodium monofluorophosphate plus 1 g of... 

Rizzoli R, Chevalley T, Slosman DO, Bonjour JP. Sodium monofluorophosphate increases vertebral bone mineral density in patients with corticosteroid-induced osteoporosis. Osteoporos Int 1995 5(l) 39-46. 

A simpler and technologically superior approach is the measurement of the direct electrical conductance. The background conductivity of the mobile phase is electronically subtracted, not requiring a suppressor device. One example of direct conductivity detection is the simultaneous determination of potassium nitrate and sodium monofluorophosphate in dentrifices [76]. Alendronate, a bisphonate, can be directly detected in intravenous solutions and tablets using an anion-exchange column and conductivity detection [77]. Another example, from one of the author s (JA) laboratory is shown in Figure 5.3. Direct conductivity detection makes it possible to selectively detect choline in the presence of an equal molar amount of an antibiotic which is not detected. 

Sodium metaperiodate, 1 170 Sodium metaphosphates, 3 88, 103 Na2P309-6H20, 3 104 (NaPOsli, 3 104 Sodium monofluorophosphate,... 

As a result, the need for SnF2 has decreased from 500,000 lbs/year to less than 20,000 lbs/year. While sodium monofluorophosphate still being comparatively less expensive, it has a worldwide market of over two million pounds/year. The comparative study of Hayden shows that sodium monofluorophosphate is approximately twice as effective as NaF in inhibiting acid production in a saliva-glucose mixture [105], It is believed that the cavity prevention provided by fluoride ions is due to the replacement of hydroxyle group in hydroxyapatite, Ca5(P04)30H of the tooth by fluoride ions to forms more insoluble fluoroapatite, Ca5(P04)3F [106],... 

Sodium monofluorophosphate is produced commercially by fusion of sodium fluoride with sodium metaphosphate. 

Sodium monofluorophosphate is highly soluble in water (42 g Na2P03F per 100 g solution). Dilute aqueous solutions of Na2P03F can be stored indefinitely and its melting point is 625°C. 

Sodium fluoride as an ingredient in dentifrices has been the subject of a number of clinical investigations. Recent studies of sodium fluoride dentifrices formulated to ensure ready availability of fluoride ions have shown anticaries benefits similar to those obtained in clinical caries trials with dentifrices containing stannous fluoride and sodium monofluorophosphate. 

James, P.M. Anderson, R.J. Beal, J.F. Bradnock, G. A 3-year clinical trial of the effect on dental caries of a dentifrice containing 2% sodium monofluorophosphate. Commun. Dent. Oral Epidemiol. 1977, 5 (2), 67-72. 

Sodium fluoride is utilized in the manufacture of organofluoro-compounds (halogen exchange reaction), as a preservative, and as a source of fluorine for toothpaste additives (sodium monofluorophosphate). 

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