Papers by Keyword: Octacalcium Phosphate

Abstract: The present study was designed to investigate whether porous titanium (Ti) having Young’s modulus similar to bone has osteoconductive characteristics in rat critical-sized calvarial bone defect. The effect of coating by octacalcium phosphate (OCP) was also examined. OCP is known as a precursor of initial mineral crystals of biological apatite in bones and teeth. Ti powder was prepared by plasma rotating electrode process in an Ar atmosphere. Then, porous Ti disks, 8 mm in diameter with 1 mm thick, were obtained using the particles ranging from 300 to 500 +m, by sintering at 1573 K without applied pressure. The disks had about 35 vol% in porosity and about 10 GPa in Young’s modulus which corresponds to that of human cortical bone. Newly formed bone was observed so as to fill the pore up at 12 weeks, confirming the ability to conduct the ingrowths of the bone tissue. Although in vitro study showed that proliferation of mouse bone marrow stromal ST-2 cells was inhibited on the dishes coated by OCP rather than the control dish, OCP coating on porous Ti seemed to stimulate the bone formation in vivo. Taken together, it seems likely that porous Ti having Young’s modulus similar to bone shows osteoconductive characteristics to conduct bone ingrowths. OCP could be a potential coating agent to assist bone regeneration on porous Ti.

Abstract: Our previous study showed that synthetic octacalcium phosphate (OCP) enhanced bone regeneration more than hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Recently, we have engineered a composite of synthetic OCP and collagen (OCP/Collagen), which improved the handling performance and synergistically enhanced bone regeneration up to eight weeks after implantation. The present study investigated whether the regenerated bone by OCP/Collagen could be stable for long period. OCP/Collagen sponge was prepared from pepsin-digested atelocollagen isolated from the porcine dermis and OCP granules. A standardized critical-sized defect was made in the rat calvarium, and an OCP/Collagen was implanted into the defect. Five rats were fixed at twenty-four weeks after implantation and examined radiographically and histologically. Radiographic examination showed that radiopaque figure was occupied throughout the defect, whereas OCP/Collagen itself was no radiopacity before implantation. Histological examination showed that newly formed bone was observed throughout the defect in OCP/Collagen. The implanted OCP/Collagen tended to be resorbed and was replaced by newly formed bone. The regenerated bone was stable and matured. The present study indicated that bone regeneration by the implantation of OCP/Collagen was stable for long-term periods. Application of OCP/Collagen without both cell transplantation and exogenous osteogenic cytokines would result in cost-effective bone regenerative therapy in the future.

Abstract: Titania (TiO2) thin films were fabricated on titanium (Ti) substrates at low temperatures by electron cyclotron resonance (ECR) plasma oxidation, and the relationship among the oxidization conditions, crystal structure and osteoconductive property was investigated. Amorphous TiO2 films were obtained below 300°C and crystallized rutile-type TiO2 films were obtained above 400°C. The XRD peak intensity of rutile TiO2 increased with increasing oxidation temperature. Mixtures of octacalcium phosphate (OCP) and Dicalcium phosphate dihydrate (DCPD) peaks were observed after calcification. The intensity of the OCP and DCPD peaks after calcification increased with increasing oxidation temperature. The ECR plasma was significantly effective to prepare crystallized TiO2 films at low temperatures.

Abstract: Biological mineralization proceeds within an organic matrix and is induced and controlled by extracellular, highly acidic matrix macromolecules. Our group has recently prepared organic-inorganic nanocomposite coatings by a strategy that closely mimics these processes. The strategy involves depositing a matrix of polyelectrolyte multilayers (PE MLs), alternating with layers of amorphous calcium phosphate (ACP) particles, then "in situ" growing nanosized apatite crystals within that matrix [1, 2]. Here we describe the results of biological "in vitro" and "in vivo" testing of these materials.

Abstract: In the production of artificial bone and tooth implants, coating of the surfaces of hard, but bioinert materials (metals, polymers) with calcium phosphate crystals has been used to improve bioactivity and facilitate osteointegration. Recently low temperature methods, involving precipitation from aqueous solutions (biomimetic precipitation) including coprecipitation of specific organic macromolecules (growth hormones, enzymes, proteins) have been developed. In this paper an alternative approach is presented, which consists in first laying down a matrix consisting of polyelectrolyte multilayers (PE MLs) alternating with layers of amorphous calcium phosphate (ACP) particles and subsequently growing calcium phosphate crystals upon/within the multilayers. This attractive approach leads to the formation of a new class of true organic-inorganic nanocomposite coatings. In a previous communication we have shown preliminary results, which point to the feasibility of this approach [1]. Here we describe in detail the design, synthesis and characteristics of the thus obtained nanocomposite coatings.

Abstract: The present study presents the relevance of X-ray diffraction analysis using synchrotron light in the identification of phases with low intensity peaks. Niobium sheets were coated with monetite and then converted to hydroxyapatite in an alkali solution. Octacalcium phosphate was identified as an intermediate phase in the conversion monetite-hydroxyapatite.

Abstract: It has been shown that fluoride ions enhance OCP hydrolysis into Ca-deficient apatite and that fluoridation in hydroxyapatite (HA) affects osteoblast activity. The present study was designed to investigate whether fluoridated Ca-deficient apatite (F-HA) formed via OCP enhances bone regeneration. F-HA was obtained through hydrolysis of the OCP in a solution containing 2 ppm fluoride at 37 °C and pH 7.4. A standardized critical-sized defect was made in the rat calvarium, and granules of F-HA were implanted into the defect. Five rats from each group were fixed through four to twelve weeks after implantation. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed that F-HA corresponded well to apatite structure. In week four, new bone matrix was formed around F-HA. In week twelve of F-HA group, newly formed bone matrix was more abundant, whereas the implanted F-HA was unresorbed and still remained. A statistical analysis in week twelve showed that the newly formed bone in the defect with F-HA was higher than that with untreated group. The fact that new bone was directly formed on F-HA implant suggests F-HA formed via OCP could be used as a bone substitute material.

Abstract: Dense hydroxyapatite (HA) and hydroxyapatite/tricalcium (HA/TCP) were immersed in Fast calcified solution (FCS) at 37°C in constant temperature culture box for 7 days. It was observed that the phase components of dense ceramics affected the composition, crystallinity and phase components of formed apatites on the surface of ceramics. It is a mixture of hydroxyapatite with a strong preferential crystallographic direction of 002 and octacalcium phosphate (OCP) on the surface of HA/TCP ceramics, whereas only an HA phase was detected on the surface of HA ceramics.