Key Engineering Materials Vols. 396-398

Abstract: Hydroxyapatite (HAP) crystalline thin-coatings have been grown using a right angle RF magnetron sputtering approach at room temperature. The surface structural information of these biocompatible coatings at nanometer scales was obtained by glancing-incidence X-ray diffraction (GIXRD) with synchrotron radiation. The GIXRD spectra were obtained by fixed incidence theta angles at 0.5 and 1 degree. Structural profile analyses were performed over these nano-coating layers with reduced substrate interference. The coating thickness was calibrated by specular X-ray reflectivity (XRR) curves. Experiments have been performed on thin-coatings of HAP sputtered on silicon wafers and acid etched titanium discs at room temperature. GIXRD analysis has shown that all the principal peaks are attributed to a crystalline HAP. Previous tests of biocompatibility with osteoblasts cells have been encouraging studies on the surface of hydroxyapatite thin coatings prepared by opposing RF magnetron sputtering approach, as a promising candidate for bioimplant materials.

Abstract: When titanium and titanium alloys are used in prosthodontic devices, exposure to the oral environment may result in discoloration or corrosion. This phenomenon may be due to fluoride, found in prophylactic agents, or peroxide, which is either produced by inflammatory cells or present in denture cleaning agents. The aims of this study were to clarify the process of discoloration or corrosion of titanium in an oral environment, and investigate the reaction of surface titanium oxide to fluoride and hydrogen peroxide by analysis of electrochemical behavior and X-ray photoelectron spectroscopy. Surface oxide film on commercially pure titanium (CP-Ti) in fluoride-containing solution was dissolved and corroded. In the peroxide-containing solution, a gradual development and thickening of the surface oxide film with subsequent discoloration of the titanium was observed

Abstract: Hydroxyapatite (HA) films were deposited onto titanium (Ti) metal substrates by an electrodeposition method under a short-pulse current. Metastable calcium phosphate solution was used as the electrolyte. The ion concentration of the solution was 1.5 times that of human body fluid, but the solution did not contain magnesium ions at 36.5°C. We used an average current density of 0.01 A/cm2 and current-on time (TON) equal to current-off time (TOFF) of 10 ms, 100 ms, 1 s, and 15 s. The adhesive strength between HA and Ti substrates were relatively high at TON = TOFF = 10 ms. It is considered that small calcium phosphate crystals with low crystallinity were deposited on the Ti surface without reacting with other calcium phosphate crystals, H2O, and HCO3– in the surrounding environment. This resulted in relaxation of the lattice mismatch and enhancement of the adhesive strength between the HA crystals and Ti substrates.

Abstract: Although titanium metal has been used intensively in the last years as biomaterial in the medical and dental areas its surface is not bioactive. In this work, titanium metal was submitted to an alkali treatment in order to make the metal surface bioactive. The samples were submitted to alkaline treatment (AT) using NaOH 5M aqueous solution at 60°C for 24 h and after that they were heated thermically to stabilize the layer obtained with AT. The bioactivity of the samples was evaluated soaking them into the simulated body fluid (SBF) at 36,5°C for 28 days. The morphological, structural changes and the electrochemical characterization were analyzed using scanning electron microscopy, x-ray diffraction and electrochemical impedance spectroscopy (EIS), respectively. It was verified that after AT plus heat treatment (HT) a sodium titanate layer was formed on the samples surface and after the bioactivity tests an apatite layer was formed. Impedance analysis show that the resistance of film on Ti is high and this value increases when the sample is soaked in SBF. It means that the apatite (HPA) film is occurring and the value of the capacitance with the presence of the HPA film (Cp) values indicate that the film maintain a compact and uniform characteristics.

Abstract: The objective of this series of experiments was to evaluate the effect of bioceramic coatings/ incorporations on implant surfaces as a function of implant and surgical drilling design. Methods: A series of four in vivo studies were conducted utilizing the dog proximal tibia model. The models provided implants that remained from 2 to 5 weeks implantation time. The different studies comprised the placement of implants with intimate contact with bone following placement and implant designs that resulted in healing chambers. The various implant types presented surfaces with and without Ca- and P-based bioceramic incorporations. Biomechanical and histomorphometric measurements along with qualitative bone-implant interface morphology evaluation were performed. For all studies, one-way ANOVA at 95% level of significance was employed along with Tukey's post-hoc multiple comparisons. Results: Close contact between cortical and trabecular bone and all the different implant surfaces irrespective of implant fit (with and without healing chambers) showed that all surfaces were biocompatible and osteoconductive. In general, appositional bone healing was observed at all implant regions that were in intimate contact with bone immediately after placement, and an intramembranous-like healing occurred throughout the whole volume of the healing chambers. Irrespective of implant + surgical drilling design, the presence of Ca and P resulted in a bone morphology that showed primary osteonic structures at earlier times than uncoated surfaces. Conclusion: Irrespective of implant design and surgical drilling combination, the presence of Ca and P on the implant surface positively modulated early healing around endosseous implants.

Abstract: In this study, commercially pure titanium (Ti-cp) sheets grade 2 were used as substrates. To investigate the role of composition and characteristics of titanium surface oxides in cellular behavior of osteoblasts, the surface of titanium were modified by anodic oxidation with sulphuric acid. Subsequently were treated part of anodized samples with FN and cultured with osteoblast cells for 30, 120 and 240 minutes. The chemical composition and topography have influenced the interaction between fibronectin and substrate. Cells were found more associated to the surfaces that have been submitted to anodization and FN coating than to the related controls.

Abstract: The paper is an electrochemical study regarding the influence of different acid etching conditions on the corrosion behaviour of a new Ti based bioalloy with Nb, Ta and Zr. Open circuit, potentiodynamic and electrochemical impedance spectroscopy were the methods performed in a simulated body fluid (SBF) and a stability mechanism was discussed in terms of equivalent circuits.

Abstract: The Tissue Engineering appears with a modern proposal for the treatment of damages or diseases. The study of materials and methods for tissues and organs regeneration by the patient cells culture had been developed on the last years but still couldn’t be used for all different tissues. In this multidisciplinary research field, the present work joins the biodegradability of poly(ε-caprolactone) (PCL) with the osteoconductive properties of β-tricalcium phosphate (β-TCP) in order to create a composite which acts as a temporary support for cell culture without a second surgery to remove the biomaterial. This work evaluates three membranes types, obtained by casting in chloroform, on the biocompatibility and differentiation on mesenquimal stem cells (hMSC). These analyses showed cell viability with the rezasurin method and the alkaline phosphatase activity (ALP). DMA analyses, MEV and OPM were performed.

Abstract: Composites of calcinated bovine bone derived hydroxyapatite (HA) with 5, 7.5 and 10 wt % B2O3 were prepared by sintering. The production of HA from natural sources is preferred due to economical and time saving reasons. In this study scanning electron microscopy (SEM) investigations, microhardness and compression strength measurements were performed on composites. The experimental results indicated that compression strength and microhardness of HA-boron-oxide composites decrease when the content of boric acid and sintering temperature increase. The best mechanical properties achieved for 5 wt % addition of dehydrated boric acid. It was seen that at higher sintering temperatures, the compression strength and the microhardness decrease due to the very intensive pore formation. The results agree fairly well with microstructure analysis.

Abstract: Composites of calcinated bovine bone derived hydroxyapatite (HA) with 5 and 10 wt % SrCO3 were prepared by sintering. The production of HA from natural sources is preferred due to money and time saving reasons. In this study scanning electron microscopy (SEM) investigations and together with measurements of microhardness, density, and compression strength were performed. The experimental results indicated that compression strength and microhardness values of HA-Sr-oxide composites decrease when the content of SrCO3 and sintering temperature increase. The best compression strength values were achieved after sintering at 1000°C. It was seen that at higher temperatures the compression strength and the microhardness values decrease due to the pore formation. The pore formation is very important for scaffold formation for tissue engineering purposes.