Calcium phosphate ceramics, phases

A number of spectacular applications in structural studies of glasses were reported employing the INADEQUATE experiment.174 175 The basic sequence and different modifications were discussed in Section 2.2.2. Smith and coworkers176 used 31P refocused INADEQUATE MAS NMR experiment for searching the length of phosphate chain and quantification of crystalline phases in ternary sodium calcium phosphate ceramic of composition (CaO)0.4(Na20)0.i(P205)o.5. 

While preparing bioceramic samples from various commercial materials available on the market, we have come across hardly predictable properties of the end product, like crystallinity degree, phase composition and, following, bioactivity and mechanical characteristics. One of the disadvantages while purchasing commercial calcium phosphate powders or commercial calcium phosphate ceramic materials is insufficient information about s5mthesis conditions of these calcium phosphates, raw materials and in which proportions these materials are taken. 

Kokubo T, Kim HM, Kawashita M, Takadama H, Miyazaki T, Uchida M, Nakamura T (2000) Nucleation and growth of apatite an amorphous phases in simulated body fluid. Glass Sci Technol 73 247-254 Kon M, Miyamoto Y, Asaoka K, Ishikawa K, Lee HH (1998) Development of calcium phosphate cement for rapid crystallization to apatite. Dental Mater J 17 223-232 Kondo K, Okuyama M, Ogawa H, Shibata Y, Abe Y (1984) Preparation of high strength apatite ceramics. J Am Ceram Soc 67 222-223... 

Glass-ceramics are also used for dental prosthetics. These materials are primarily based on either lithium disilicate or calcium phosphate glasses. Machinable glass-ceramics based on fluoromica phases have also been developed for machined inlays. All of these materials must be stained to match the surrounding teeth to be acceptable to the patient. 

DNase, a well characterized and biologically specific enzyme with therapeutic value in the treatment of cystic fibrosis, was chosen as a model agent for studying the effects on an enzymatic bio/molecule of surface immobilization on nanocrystalline ceramic particulates. As the data show, and consistent with previous observations, DNase exhibits a marked retention of biological activity when surface immobilized on the solid phase of a colloid comprised of polyhydroxyl oligomeric films investing degradable calcium-phosphate nanoparticles. 

For elucidation of the role of substituents in adhesion of ceramic materials, these monomers have, thus, been evaluated in terms of adhesion strength toward calcium metaphosphate ceramic (CMP) as a new type of castable ceramic. CMP, like tooth enamel, is a calcium phosphate material derived from the glass with a basic composition of 49Ca052P205. As shown by a cross-section microscopic photograph of CMP in Fig. 1, CMP consists of both crystalline and glass phases, and the crystalline rods are oriented toward the surface. The structure is quite similar to that of tooth enamel, in which the enamel crystalline rods also grow toward the tooth surface. 

Interestingly, the composition, phase, morphology, and placement of hydroxyapatite will influence the speed and extent of bone growth. Since the resorption process is siuface-driven by the adsorption of osteoblasts, the ultimate solubility of a ceramic will be directly related to its surface area - i.e., crystal size and density. In addition, careful cmitrol of processing parameters is necessary to prevent thermal decomposition of hydroxyapatite into other soluble calcium phosphate phases (e.g., tricalcium phosphate, Ca3(P04)2, tetracalcium phosphate, Ca4(P04)20, and CaO), which... 

Calcium phosphate-based ceramics constitute, at present, the preferred bone substitute in orthopedic and maxillofacial surgery. They are very sirttilar to the mineral phase of the bone, by their stracture and/or their chemical composition. Calcium phosphates usually found in ceramics are ... 

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