Key Engineering Materials Vols. 361-363

Abstract: Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.

Abstract: The aim of this study was to evaluate potential effects of DNA-coatings on calcium phosphate (CaP) nucleation from simulated body fluids (SBF) and subsequently the effects of DNA-coatings and SBF-immersed DNA coatings on the behavior of osteoblast-like cells. DNAcoatings demonstrated to enhance the nucleation and deposition of CaP from SBF compared to titanium controls. The behavior of osteoblast-like cells was affected on SBF-immersed DNAcoatings, showing an increased deposition of the extracellular matrix protein osteocalcin compared to titanium controls. These results indicate bone-bonding capacity of DNA-coatings, which needs to be confirmed using future animal experiments.

Abstract: Titanium is well known as an implant material having excellent biocompatibility and mechanical properties for use in bone substitute. In the present study, to enhance the biocompatibility of titanium, its surface was modified by hydrothermal treatment using dilute alkaline solution. After hydrothermal treatment, anatase predominantly formed on a titanium surface. The anatase phase showed high crystallinity and c-axis orientation. The anatase layers with leaf-like and pyramid-like forms were observed on titanium autoclaved at 120 °C and 240 °C, respectively. The anatase formation and its morphology were significantly related to the autoclaving temperature. To estimate the cellular compatibility of the autoclaved titanium, mouse osteoblast-like cells (MC3T3-E1 cells) were cultured on the autoclaved titanium surface. After 7- days culturing, the number of the cells harvested from the autoclaved titanium was higher than that from untreated titanium. The surface modification of titanium by hydrothermal treatment involved the proliferation of the cells on its surface.

Abstract: Titanium dental implants presenting different blasted surfaces and an OCP coated surfaces have been implanted in the femoral epiphysis of rabbits. A comparable osseointegration has been observed for the titanium implants blasted either with alumina or biphasic calcium phosphates particles whatever the delay of implantation (2 or 8 weeks). A higher bone to implant contact has been observed for the SLA and OCP coated implants as compared to the grit-blasted groups.

Abstract: The aim of this study was to deposit an adherent apatite coating on titanium substrate using a two-step chemical deposition method. First, titanium substrates were immersed in an acidic solution containing calcium and phosphate ions, resulting in the deposition of a monetite (CaHPO4) coating. Second, the monetite crystals were converted to apatite by hydrolysis in NaOH solution. Composition and morphology of the initial and final coatings were identified using X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS). The final coating was porous and the apatite crystals were agglomerated and followed the outline of the large monetite crystals. The average tensile bond of the coating was 5.2 MPa and cohesion failures were observed more frequently than adhesion failures. The coating adhesion measured using scratch test was 13.1N. In conclusion, this study showed the potential of a two-step chemical deposition method for depositing an adherent coating of apatite at low temperatures.

Abstract: Apatite formation on the surface of materials in body environment is an essential condition to show osteoconduction after implantation in bony defects. This study reports the novel technique for providing the apatite-forming ability to titanium metals by only controlling the spatial gap and thermal oxidation. Two pieces of titanium thermally oxidized at 400 °C were set together like V-letter with varied mouth opening. They showed the formation of apatite on both facing surface after exposure to a simulated body fluid (SBF) proposed by Kokubo and his colleagues, when the gap was less than approximately 600 μm. Moreover, specimens with micro-grooves of 500 μm in depth and 200-1000 μm in width was able to form apatite in SBF with in 7 days, after they were thermally oxidized at 400 oC. These results indicated that the titanium metals were provided with apatite-forming ability, i.e. osteoconduction, due to controlled gap with thermally oxidized surface. Hence, we conclude that bioactive titanium substrate showing osteoconduction can be produced by designed machining followed by thermal oxidation at an appropriate temperature.

Abstract: An apatite layer was successfully formed on titanium substrates by electrochemical deposition under a pulse current in a metastable calcium phosphate solution, which had 1.5 times the ion concentrations of a normal simulated body fluid, but did not contain MgCl2·6H2O, at 40 °C for 30, 60, 90 and 120 minutes at the average current density of 10 mA/cm2. The thickness of the apatite layer was increased with increasing deposition time. The pulse-current deposition produced the thicker apatite layer than the direct-current deposition, and gave some effects on the surface morphology of the apatite. The pre-treatment using acid solution gave a better adhesive between apatite and substrate. It is expected that the present electrochemical deposition under a pulse current will be useful to rapidly coat apatite on metallic materials.

Abstract: When producing implant materials, achievement of optimal bioactivity and biocompatibility are essential. Nanocoatings can provide an efficient cost effective way to alter the interactions of the implant material with its destined “host” environment. Nanocoatings of sol-gel derived carbonated hydroxyapatite (HAp) and zirconia were produced in this study. The surfaces were characterised by Fourier transform infrared spectroscopy (FTIR) and light microscopy. Cell adhesion, proliferation and viability, as well as expression of alkaline phosphatase (ALP is an indicator of bone formation) were assessed as indicators of biocompatibility. Our results have shown that sol-gel derived nano crystalline HAp acts as an ideal surface for implant coatings.