Calcium phosphate fluorides

Inorganic salts that contain halogens are usually soluble. They commonly occur as simple, single, negatively charged anions in soil. There are two common exceptions to this generalization. First, fluorine is commonly found bonded to phosphate in insoluble minerals called apatites, which are calcium phosphate fluorides. 

Table 36.4 shows that the presence of fluoride ions enhances the rate and extent of remineralization. Increasing the fluoride concentration had no further effect. This supports the idea that fluoride helps to reduce caries by enhancing the remineralization of microscopic enamel lesions so that they never become clinically detectable. If fluoride is not available the lesions increase in size until they can be seen on X-ray examination. Similarly small enamel lesions can be made to disappear from radiographs following the use of recaldfying mouthwashes. At present these are based on calcium phosphate-fluoride solutions adjusted to... 

Valentinite, see Antimony(III) oxide Verdigris, see Copper acetate hydrate Vermillion, see Mercury(II) sulflde Villiaumite, see Sodium fluoride Vitamin B3, see Calcium (+)pantothenate Washing soda, see Sodium carbonate 10-water Whitlockite, see Calcium phosphate Willemite, see Zinc silicate(4—)... 

Phosphoms oxyfluoride is a colorless gas which is susceptible to hydrolysis. It can be formed by the reaction of PF with water, and it can undergo further hydrolysis to form a mixture of fluorophosphoric acids. It reacts with HF to form PF. It can be prepared by fluorination of phosphoms oxytrichloride using HF, AsF, or SbF. It can also be prepared by the reaction of calcium phosphate and ammonium fluoride (40), by the oxidization of PF with NO2CI (41) and NOCl (42) in the presence of ozone (43) by the thermal decomposition of strontium fluorophosphate hydrate (44) by thermal decomposition of CaPO F 2H20 (45) and reaction of SiF and P2O5 (46). 

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. 

Modem production of elemental phosphoras uses a technique similar to the metallurgical processes described in Chapter 20. Apatite is mixed with silica and coke and then heated strongly in the absence of oxygen. Under these conditions, coke reduces phosphate to elemental phosphoms, the silica forms liquid calcium silicate, and the fluoride ions in apatite dissolve In the liquid calcium silicate. The reactions are not fully understood, but the stoichiometry for the calcium phosphate part of apatite is as follows ... 

The progress of precipitation is revealed by the concentration/time curves for zinc and phosphate, since both these species are present initially in solution. There should be maxima for the soluble aluminium, calcium and fluoride which are extracted from the glass, but because of the early onset of precipitation these are not observed. Precipitation is accompanied by an increase in pH when it reaches 1-8, at which juncture 50% of both zinc and phosphate have been precipitated, the cement paste gels (5 minutes after preparation). 

Kim, C.Y., Clark, A.E. and Hench, L.L. (1992) Compositional dependence of calcium-phosphate layer formation in fluoride bioglasses. Journal of Materials Science, 26, 1147-1161. 

CCP in milk is mentioned in connection with casein above (Section VI.C). Fluorapatite is a major constituent of phosphate rocks, and a constituent, probably important, of human tooth enamel for those whose drinking water contains significant amounts of naturally occurring or added fluoride. Fluorapatite is significantly less soluble than hydroxyapatite - the relationship between the solubilities of fluorapatite and hydroxyapatite parallels (but is much less extreme than) that between calcium fluoride (Ksp — 3.9 x 10 11 mol3 dm-9) and calcium hydroxide (Ksp = 7.9 x 10 6 mol3 dm 9). Calcium diphosphate, Ca2P207, is believed to be the least soluble of the calcium phosphates. 

Reaction with calcium triphosphate fluoride yields calcium dihydrogen phosphate, a component of superphosphate fertilizer ... 

Concerning synthetic fluoridated calcium phosphate biomaterials (i.e. fluorapa-tites, fluorhydroxyapatites, carbonated fluorhydroxyapatites and other calcium... 

The hydrolysis of Cap2 in solutions containing phosphates and carbonate ions results in the formation of fluor-, fluor-hydroxy- or fluor-carbonate-apatites. Fluor and fluor-hydroxy- apatites can also be formed by the hydrolysis of dicalcium phosphate (anhydrous or dihydrate), DCPAor DCPD, respectively, in solutions containing fluoride ions [121] or from the hydrolysis of any other calcium phosphate salt. 

Fluorhydroxyapatite solid solutions can be prepared by the sol-gel method [134,135]. Cheng et al. reported the control of fluoride content in fluorhydroxyapatite solid solutions by the amounts of triethanolamine (N(CH2CH20H)3) and trifluoroacetic acid (CF3COOH) in the mixed ethanol solutions of Ca(N03)2 and P0(CH2CH20H)x(0H)3 x with a Ca/P ratio of 1.67 [134]. After evaporation of the mixed ethanol solution at 150°C on a hot plate, the powder obtained, comprising a homogeneous mixture of calcium nitrate crystallites and amorphous calcium phosphates, is then heated at 500 or 900°C for 1 h to be transformed into the pure apatitic phase. 

Other coating processes involving fluoridated apatite have been investigated to improve the long-term adhesion and promote osteointegration of cementless titanium-based metal implants pulsed laser deposition, electron beam deposition and ion beam sputter deposition techniques, and sol-gel methods, for example. They lead to fluor-containing calcium phosphates (apatites in most cases) with different compositions and crystallinity states. 

A.A. Mirtchi, J. Lemaitre, E. Munting, Calcium phosphate cements Effect of fluorides on the setting and hardening of beta-tricalcium phosphate-dicalcium phosphate-calcite cements. Biomaterials 12 (1991) 505-510. 

I. Manjubala, T.S. Kumar, Preparation of biphasic calcium phosphate doped with magnesium fluoride for osteoporotic applications, J. Mater. Sci. Lett. 20 (2001) 1225-1227. 

P. Venkateswarlu, L. Singer, W.D. Armstrong, Determination of ionic (plus ionizable) fluoride in biological fluids. Procedure based on adsorption of fluoride ion on calcium phosphate. Anal. Biochem. 42 (1971) 350-359. 

Acetylene Dichloride Acetylene Tetrachloride Acetylenogen Acetyl Hydroperoxide Acetyl Peroxide Solution Acid Ammonium Carbonate Acid Ammonium Fluoride Acid Calcium Phosphate... 

Calcium Arsenate Calcium Phosphate Calcium Carbide Calcium Chlorate Calcium Chloride Calcium Chloride Calcium Chloride Calcium Chromate Calcium Chromate Calcium Chromate Calcium Cyanide Calcium Peroxide Calcium Fluoride Calcium Hydroxide Calcium Hypochlorite Calcium Phosphate Calcium, Metallic Calcium Nitrate Calcium Nitrate Calcium Oxide Calcium Peroxide Calcium Phosphate Calcium Phosphate Calcium Phosphide Calcium Resinate Calcium Resinate Calcium Resinate Calcium Phosphate Mercuric Chloride Mercurous Chloride... 

Monoethanolamine Ethylamine Ethylene Glycol Vinyl Fluoride Ethylene Glycol Calcium Phosphate Isobutylamine Monoisopropanolamine Isopropylamine Methylamne Methylcrazine Nitric Oxide Pentaerythritol... 

The majority of the phosphoric acid is made by the wet process, which involves reaction of calcium phosphate or the mixed calcium fluoride-calcium phosphate ores with sulfuric acid. 

Teeth have a transparent outer layer of enamel which is about 2 mm thick, and an inner layer of white dentine which surrounds the innermost pulp cavity where the nerves are located. Both the enamel and the dentine are calcium phosphate, a mineral that can exist in various forms, that of the enamel layer being hydroxyapatite, which is one of the hardest naturally occurring minerals. When this is exposed to fluoride it forms an even harder mineral fluoroapatite. Unfortunately both this and hydroxyapatite are slightly porous and this is why teeth become stained by chemicals such as polyphenols and other dark coloured substances that are present in coffee, tea, red wine, bilberries, blueberries, and cigarette smoke. (Staining can also be caused by tetracycline antibiotics, especially when taken by children whose teeth are developing. This type of discoloration is permanent, which is why such antibiotics are now only prescribed for adults.)... 

The raw material from which phosphorus and its compounds are prepared is calcium phosphate, either in the form of natural phosphate rock or in bone ash. For laboratory preparations bone ash is preferable since it is practically free from fluorides and compounds of iron. This bone ash may be assumed to be 80 per cent... 

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