Abstract: The aim of the present study is to fabricate bone cement that could transform to carbonate apatite (CO3Ap) completely at body temperature. The powder phase of vaterite and dicalcium phosphate anhydrous (DCPA) was mixed with 0.8 mol/L of NaH2PO4, Na2HPO4, and Na3PO4 aqueous solution, respectively, with liquid to powder ratio (L/P ratio) of 0.45, 0.55, and 0.65. The paste was packed into split stainless steel mold, covered with the glass slide and kept at 37°C and 100% relative humidity for up to 96 hours (h). XRD analysis revealed that the cement became pure CO3Ap within 24 h for Na3PO4, 72 h for Na2HPO4, and 96 h for NaH2PO4, respectively. FT-IR results showed that all of the obtained specimens could be assigned to B-type CO3Ap. CHN analysis showed the carbonate content of the specimen were 10.4 ± 0.3% for NaH2PO4, 11.3 ± 0.7% for Na2HPO4, and 11.8 ± 0.4% for Na3PO4, respectively. Diametral tensile strength of the set CO3Ap cement was 1.95 ± 0.42 MPa for NaH2PO4, 2.53 ± 0.53 MPa for Na2HPO4, and 3.45 ± 1.53 MPa for Na3PO4, respectively. The set CO3Ap cement had low crystallinity similar to bone apatite since it was synthesized at body temperature. We concluded, therefore, that CO3Ap cement prepared from the present method has higher possibility to be used as an ideal bone replacement.
Abstract: Carbonate apatite showed an excellent bioresorbability through the remodeling process of bone. In the present study, we prepared self-setting carbonate apatite cement based on α-TCP. We tried two types of the cement powder formulations, that is, first one (F1) is α-TCP containing given amounts (10 to 50 mass%) of synthesized carbonate apatite and second one (F2) is α-TCP treated in 0.5M NaHCO3 for various times between 90 and 360 min. The cement powder was mixed with 0.25M Na2HPO4 to allow set at 37°C and 100% of relative humidity up to 1 day. XRD and FT-IR results showed formation of B-type carbonate apatite phase after setting in both of the formulations. With the formulation, F1, the carbonate content was increased with the treatment time and the maximum content was 4.1 mass%. DTS deacreased with the amount of cabonate apatite in the formulation, F1, however, it increased up to 9 MPa with treatment time in the formulation, F2.
Abstract: This study aims to improve the handling property of alpha-tricalcium (αTCP) cement. In order to improve the handling property, the effect of γ-poly-glutamic acid (γPGA) as a chelating agent was studied. γPGA is water soluble, biodegradable, nontoxic, and edible material. γPGA contains carboxyl group, so the chelating effect between Ca2+ ions released from calcium phosphate cement and carboxyl group of γPGA is prospected when it mixed with αTCP based cement. The results obtained in this study clearly demonstrated that the addition of γPGA into the αTCP cement was highly effective in controlling the handling property of αTCP cement.
Abstract: mplant fixation is correlated with direct bone apposition on the implant surface. In a former study it was reported that a new coating material enhances the bone-to-implant-contact in comparison to machined and rough surfaces. This study is aimed at clarifying the effect of an enhanced bone-to-implant-contact that is induced by a new coating material. The coating is produced by spin and spray coating and consists of a silica matrix, in which nanocrystalline hydroxyapatite is embedded. The coating material exhibits a high porosity in the micrometer and nanometer scale. Coated implants were inserted subcutaneously in Wistar Rats. The specimens were excised after 6 and 12 days. EDX and SEM analysis showed a reduction of the silica amount within 6 days. In accordance to former results of a bone grafting material with the same structure, this matrix change is responsible for an initial bone formation at early stages.
Abstract: Chemical structure of hydroxyapatite (HA) is very close to human bone which makes it compatible with the tissue of the human body. Its good biocompatibility makes it to be used extensively in many prosthetic applications, especially as a porous material for optimal bone in growth. Currently, this material is being deposited on bio-inert metallic implants and used as recovery parts in human body. In this present study a high-power plasma jet known as gas tunnel type plasma torch (GTTP), was used to produce HA and YSZ reinforced HA coatings on stainless steel substrate. In this study, microstructure, tribological properties and bioactivity of the GTTP sprayed HA and YSZ reinforced HA coatings was investigated. The XRD spectra of the as-sprayed coatings showed that the as-sprayed pure HA coating retained its crystalline HA phase similar to the initial feed stock HA powder, even though there existed a possibility for occurrence of decomposition during its in-flight in high temperature plasma zone. In the present case the decomposition processes of in-flight HA could be well controlled by means of selective operating parameters and unique nature of GTTP jet. The presence of un-melted particles and pores inside the coating microstructure play a vital role in the bonding strength of the coating.
Abstract: The present authors recently developed a new calcium phosphate (CaP) coating technique on an ethylene-vinyl alcohol copolymer substrate utilizing a laser-assisted biomimetic (LAB) process. In the present study, the LAB process was applied to a sintered hydroxyapatite (sHA) substrate for CaP coating. The LAB process was carried out by irradiating the sHA substrate immersed in a supersaturated CaP solution with a low-energy Nd-YAG pulsed laser. Within 30 min of irradiation, contiuous CaP layers with different morphologies were successfully formed on the laser-irradiated sHA surface. A submicron cavernous structure of the CaP layer was developed into a micron flake-like structure as the laser power increased from 1 to 3 W. This result suggests that the secondary nucleation and growth of CaP crystals were accelerated by laser irradiation in a power-dependent manner. Laser absorption by the sHA substrate and the resulting increase in ambient temperature locally near the surface should be responsible for the accelerated CaP nucleation and growth. The present CaP coating technique using the LAB process is simple and quick, hence it would be useful in orthopedic and dental applications as an on-demand surface-functionalization method for biomaterials consisting of sHA.
Abstract: HAp-nanoparticle-coated biodegradable polymer microspheres loaded with magnetic Fe3O4 particles can be successfully prepared by evaporating volatile oil (dichloromethane) from HAp-nanoparticle-stabilized oil droplets containing biodegradable polymer and Fe3O4 particles without any molecular surfactants or polymeric stabilizers. In this study it was found that the hydrophobic surface modification for the Fe3O4 particles was a key factor to prepare stable HAp-nanoparticle-stabilized oil droplets (and HAp-nanoparticle-coated polymer microspheres) loaded with magnetic Fe3O4 particles.
Abstract: This study aimed to create a thick hydroxyapatite (HAp) film on the surface of a human tooth by using a newly developed powder jet deposition (PJD) device for dental handpieces, and sought to examine the microstructural and mechanical properties of the resulting HAp film. The film was evaluated on three-dimensional view, surface roughness, Vickers hardness, and bonding strength before and after artificial aging through thermal cycling (555°C) for 500 cycles (30 sec for each cycle, 20 sec of dwell time).The HAp particles in the deposited film were densely packed, and the HAp films three-dimensional microstructure and its rough surface were maintained after thermal cycling. There was no significant difference in either the HAp films Vickers hardness or the bonding strength between the film and the enamel substrate before and after thermal cycling. The HAp films created in this study demonstrated excellent microstructural and mechanical properties even after the application of thermal stress. We demonstrated the possibility of using a new type of powder jet deposition (PJD) method we developed to form a new type of interface between the tooth and biomaterials. Consequently, we propose the use of this method in new dental treatments.
Abstract: mplants made of titanium and its alloys are widely used in dental and orthopedic fields due to their excellent chemical stability and mechanical properties. However, due to the bio-inert properties of titanium and its alloys, it is difficult to achieve a chemical bond with bone tissue and to form a new bond on the surface. To improve biocompatibility, surface treatments are often used to modify the chemical and morphological properties. Besides, the mussel-inspired molecule of 3,4-dihydroxy-L-phenylalanine (dopamine) shows excellent biological responses. The aim of this study is to investigate the physicochemical and biomedical properties of CaP porous coating with dopamine. The CaP porous coating was prepared on titanium by micro-arc oxidation, and then bio-inspired molecular of dopamine modified surface to improve the cell behavior. Characteristics of the morphology, chemical composition, and interfacial properties of dopamine-functionalized CaP porous architecture was performed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The osteoblastic cell behaviour, such as differentiation and morphology is evaluated. The nitrogen signal in XPS spectrum was indicated that the dopamine existed in the porous coating. The anatase and rutile phases of porous coating with dopamine were identified. Morphologies of porous coating with dopamine showed the uniform and three-dimensional structure. Cell culture experiments demonstrate that the porous coating with dopamine would improve cell behavior. All findings in this study indicated that CaP porous coating with dopamine have good bioactivity for clinical applications.
Abstract: Calcium phosphate (CaP) was formed on glutamic acid-modified nickel-free high-nitrogen stainless steel (HNS) by a chemical solution deposition method in neutral/alkaline solution. Modification of glutamic acid on the surface of HNS was performed using trisuccinimidyl citrate (TSC) as a linker. The glutamic acid-derived carboxyl groups introduced on HNS initiated rapid nucleation of CaP during each treatment at pH 7.3 or 8.9. X-ray diffraction analysis and Fourier transform infrared spectra showed each CaP deposited on glutamic acid-immobilized HNS after 24 hrs was identified as low-crystallinity calcium-deficient carbonate-containing hydroxyapatite (HAp). A significant difference in the microstructure between the two pH values was observed; HAp deposited at pH 7.3 was composed of plate-like crystals, whereas that at pH 8.9 was chestnut-like crystals. Therefore, the pH value of the solution played an effective role in controlling the microstructure of HAp deposited on glutamic acid-immobilized HNS.