Calcium hydroxy apatite

Calcium hydroxy apatite contains the phosphate and hydroxyl groups. Using calcinm hydroxide as the precipitant, the chemical reaction is ... 

Again, as in previous chapters, the best place to investigate for determining the modes of removal is the table of solubility products constants as shown in Table 14.1. A precipitation product that has the lowest K p means that the substance is the most insoluble. As shown in the table, the phosphate ion can be precipitated using a calcium precipitant producing either Ca5(P04)3(0H)(j) or Ca3(P04)2. Of these two precipitates, Ca5(P04)3(0H)(j) has the smaller K p of 10" thus, it will be used as the criterion for the precipitation of phosphates. Ca5(P03)3(OH)(j) is also called calcium hydroxy apatite. 

Solubility product constant of calcium hydroxy apatite phosphate... 

The D-vitamins are a group of fat soluble materials with high antirachitic activity. Rickets is a disease of infancy caused by faulty calcium hydroxy apatite deposition in the growing bone. It was Palm 140) in 1890 who found that the disease responded favorably to irradiation of patient s food or skin by sunlight or ultraviolet light. Mellanby 113) in 1919 first reported the presence of an antirachitic factor in cod-liver oil. This discovery encouraged research on the isolation of the active principle in fish-liver oil, but the low natural concentration of the vitamin made isolation very difficult. 

Calcium Phosphates And Calcified Tissues. Precipitation in the system Ca(0H)2 - H3PO4 - H2O can lead to the formation of several calcium phosphates (shown in Table IV), of which hydroxy-apatite 0HA is the most stable above a pH of about 4.1. The relative stabilities are illustrated in Figure 12. 

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. 

Phosphates are valuable fertilizers. Phosphate rock itself (tricalcium phosphate, Cag(P04)o, and hydroxy-apatite) is too slightly soluble to serve as an effective source of phosphorus for plants. It is accordingly converted into the more soluble substance calcium dihydrogen phos phate, Ca(HoP04)o. This may be done by treatment with sulfuric add ... 

Keeping teeth clean requires toothpaste, a mixture of detergents and abrasives, which are hard substances that help remove unwanted materials on the tooth surface. The structure of tooth enamel is essentially that of a stone composed of calcium carbonate (CaCOj) and calcium hydroxy phosphate [apatite—GajQ(PO )g(OH)2], Despite being the hardest substance in the human body, tooth enamel is readily attacked by acids. Because the decay of some food particles produces acids, it is important to keep teeth clean. 

Most of the data available on this topic refer to hydroxyapatite deposited by plasma spraying. Although compounds may form at the metal/hydroxy-apatite interface, particularly in the case of titanium, their existence has not been unequivocally demonstrated. Titanium phosphates and phosphides, as well as calcium titanates, may exist, but they probably form very thin layers. The large surface roughness, caused by grit blasting of the substrate prior to hydroxyapatite deposition, is another factor that renders identification of any interfacial compounds by surface analysis techniques difficult. 

Mineralization is a phenomenon where the body deposits calcium salts, such as hydroxy apatite on/within the device (intrinsic) or in the fibrotic encapsulation (extrinsic). Note that all implanted devices have been reported to be subject to mineralization, regardless of the materials used. At present there is really no good, predictive accelerated test method, although implant in adolescent rats appears to be about as good as is available. Explants are evaluated by SEM and EDS for calcium deposition. 

A mixture of tri-calcium phosphate and hydroxy-apatite (Florex), exhibited a fluoride removal capacity of 600 mg/L and is regenerated with 1.5% sodinm hydroxide solution. Owing to high attritional losses, Florex was not snccess-... 

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