Phosphates hydroxyapatite

Calcium phosphate Hydroxyapatite Ca10(OH)2(PO4)6 Flocculated boiler sludge, as a result of residual hardness. 

Some phosphate-cycle reactions are shown below, and, although for the sake of simplicity only calcium phosphate is shown as a precipitant, depending on the operational circumstances, the reaction produces either tricalcium phosphate, hydroxyapatite, or a combination of both salts. 

Arthropathies associated with crystals deposition are acute gouty arthritis, chronic gout and chronic tophaceous gout due to monosodium urate crystals. Then there is acute pseudogout and chronic pyrophosphate arthropathy caused by calcium pyrophosphate dehydrate crystals. Acute calcific periarthritis, acute hydroxylapatite arthritis and chronic hydroxyapatite arthritis including Milwaukee-shoulder-knee syndrome are due to basic calcium-phosphate-hydroxyapatite crystals. 

Calcium phosphate (hydroxyapatite) Proteins, polynucleotides, nucleic acids... 

The most important bio-active materials are calcium phosphate, hydroxyapatite and glass ceramics. 

The spaces between the ends of the tropocollagen molecules in a collagen fiber (see Fig. 4) are the nucleation sites for the deposition of a form of calcium phosphate, hydroxyapatite, in bone formation. Further hydroxyapatite is added until the nucleation sites grow and join with one another to form the mature bone structure. 

Key Words Biomineralization, Solid-state NMR, Biominerals, Calcium phosphate, Hydroxyapatite, Bone, Dentin, Ca-43 NMR, P-31 NMR, HAp. 

Fig. 9 Tricalcium phosphates (hydroxyapatite). Tricaphos, a spray-dried product (A), and Tritab, prepared by roller compaction (B).

Calcium phosphate A family of calcium phosphate ceramics including aluminum calcium phosphate, ferric calcium phosphate, hydroxyapatite and tricalcium phosphate (TCP), and zinc calcium phosphate which are used to substitute or augment bony structures and deliver drugs. Glass-ceramics A glass crystallized by heat treatment. Some of those have the ability to form chemical bonds with hard and soft tissues. Bioglass and Ceravital are well known examples. 

Calcium phosphates, particularly apatite, figure prominently in products which cau be categorised in (2), (3) or (4). Bone substitutes for dental or paediatric use can be made from tricalcium phosphate, hydroxyapatite or other P205-containing compounds. In some cases, strengths can be made to exceed that of bone although the synthetic products are usually more brittle thau the latter [17-25]. Both dense and porous products find uses as well as coatings which are plasma-sprayed or sputtered on to metallic implants. 

Unfortunately, bacteria in plaque (resulting from not brushing) shift the equilibrium toward demineralization (shown in the figure), and a cavity can begin to form. Scientists realized that fluoride encourages remineralization in teeth by replacing hydroxyl ions in nature s calcium phosphate (hydroxyapatite). The substitution changes the hydroxyapatite to fluorapatite, which is more acid resistant. 

Approximately 10% of the human population (with regional differences indicating both genetic and environmental factors [33]) is affected by the formation of stones or calculi in the urinary tract. Urolithiasis is not only a painful condition, but also causes annual costs to the health system in the order of billions of dollars in the USA alone [34, 35]. Based on their composition, structure and location in the urinary tract, renal stones have been classified into 11 groups and their formation mechanisms have been discussed together with alterations in urinary parameters and metabolic risk factors for renal lithiasis [35]. Approximately 70% of these stones contain calcium oxalate monohydrate (COM) and dihydrate as major components, while other calculi are composed of ammonium magnesium phosphate (struvite), calcium phosphates (hydroxyapatite and brushite), uric acid and urates, cystine and xanthine. An accurate knowledge of the solubilities of these substances is necessary to understand the cause of renal or bladder calculi formation and find ways towards its prevention and treatment [36]. 

Williams et al. [74] have developed a thermodynamic model of saliva which is able to simulate the distribution and speciation of metal ions in this biological fluid. The model predicts that in the pH range of 5-6, saliva becomes supersaturated with respect to calcium phosphates in the order octacalcium phosphate < hydroxyapatite < fluoroapatite. This indicates that under normal conditions, no demineralisation of teeth should occur. However, dietary acids are detrimental and are thus normally neutralised by increased secretion of saliva. 

Rock phosphate (hydroxyapatite) used to be applied to soil as a source of phosphorus fertilizer. Why is this source of phosphorus relatively ineffective What is done to it to make it a good source of phosphorus fertilizer ... 

The most obvious requirement for calcium in the body is in the mineral of bones and teeth — a complex mixture of calcium carbonates and phosphates (hydroxyapatite) together with magnesium salts and fluorides. An adult has about 1.2 kg of calcium in the body, 99% of which is in the skeleton and teeth. This means that calcium requirements are especially high in times of rapid growth — during infancy and adolescence, and in pregnancy and lactation. 

Calcium Phosphate, Hydroxyapatite, and Poly(d,l-lactic acid)... 

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