Crystallography of Octacalcium Phosphate

Crystallography of tetracalcium phosphate

“…The cell constants of octacalcium phosphate, which is known to have a structural relationship to hydrox yapatite [5], are also listed in table 1. It is apparent that th e unit-cell lengths , band c, and the enclosed angle, CI', are very nearly the same for all three salts_ It was this similarity between the dimensions of octacalcium phosphate and hydroxyapatite, that was initially taken [6] to indi cate that the two salts were struc turally related. This was later verified by the structure determination of octacalcium phosphate [5].…”

Prosthetic Aortic Valves: A Surgical and Bioengineering Approach

“…In slightly acidic calcium phosphate solutions the monoclinic DCPD is formed (Bets & Posner, 1974;Brown & Lehr, 1959). OCP is formed by the hydrolysis of DCPD in solutions of pH 5-6 and may also be precipitated heterogeneously upon TCP (Brown et al, 1957). HAP is the thermodynamically most stable phase and often, when precipitated in the presence of foreign ions, substitution of calcium, phosphate and/or hydroxyls by some of these ions take place.…”

“…Calcification consists as already mentioned in the formation of sparingly soluble salts of calcium phosphate due to the presence of high levels of calcium and phosphate in blood serum (Schneck, 1995). Although the calcific deposits consist of apatitic calcium phosphate (HAP containing mainly carbonate, fluoride, magnesium and sodium) the formation of transient precursor phases such as DCPD and OCP is possible, as in vitro studies have shown (Brown et al, 1957;Heughebaert et al, 1983;Moreno & Varughese, 1981). The formation of calcium phosphates on porcine heart valves to a percentage of 30-50% is responsible for their dysfunction after 12-15 years due to stenosis or insufficiency (Narasaraju & Rao, 1979).…”

Nature and transformation of crystalline phosphates produced by interaction of phosphate fertilizers with slightly acid and alkaline soils

“…After the mixture had been allowed to cool and stand overnight, the remaining CagHgCPO^^G'SHgO was found to have been converted to Ca]^o(OH)2(PO^.)g. A transformation from CaHP04*2H20 to CagH^CPO^^G'SH^O to Ca]^o(OH)2(POi^)5 is thought to occur in dental calculus (Brown et a]^., 1957). CaHP0^"21l20 can also form a more basic phosphate by reaction with dilute fluoride solutions to produce fluorapatite [CaioF2(P04)g] (Kurmies, 1953).…”

“…Carlstrom (1955) and Neuman and Neuman (1958) questioned the existence of the species, but X-ray studies by Brown et al (1957) and Bjerrum (1958) established CagH2(PO^)5-51120 as a unique compound. CagH2(PO^)5*51120 has frequently been found in systems more basic than dicalcium phosphate (Arnold, 1950;Tovborg Jensen and Hansen, 1957;Hayek et al, 1960;Bjerrum, 1949), and it is now known that dental calculus contains this phosphate (Tovborg Jensen and Hansen, 1.957;Howies, 1958;MacGregor and Brown, 1965;Saxton, 1968).…”