Narrow Results

The material composition and surface structure of dental and orthopaedic implants have important effects on integration of the implants with the surrounding bone, and at the same time, the release of the constituent elements of the implants into the surrounding tissues. It is the aim of this paper to study the degree of release of Ti in relation to the surface roughness of the implants. For this purpose, screw shaped implants were prepared with two different surface topographies; one group was left as-machined, i.e. as machine-turned surface, and the second group was blasted with 25 µm Al₂O₃ particles. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The as-machined surfaces had an average surface roughness (S_a) of 0.96 µm and the blasted surfaces had an S_a value of 1.16 µm. The implants were inserted into rabbit bone for 1 year. Six samples (three of each type) were prepared for PIXE analysis. The PIXE analysis was done using proton beams from a tandem type accelerator. with an energy of 2 MeV. The results show that at distances of about 2 mm from implant surface, titanium release into hard tissues was found at similar amounts for the as-machined and the blasted implants inserted in the tibia.

The material composition and surface structure of dental and orthopaedic implants influence the integration in bone, and, at the same time, the release of the constituent elements of the implants into the surrounding tissues. Titanium, titanium alloys (Ti-6Al-4V) and other materials which are considered to be biocompatible materials, release metal ions into the surrounding tissues. This may affect the appropriate biological response of the tissues to the implanted materials. The toxicity of some of the constituent elements of these implants, e.g. vanadium, is a matter of serious concern. In this paper, the experimental data on application of PIXE to biomedical-implant research are presented. Two groups of samples were prepared for PIXE analysis. The first group consisted of the specimens that were retrieved from the tissues around implants in 28 rats. The second group consisted of specimens that were sliced and polished to a thickness of a few 10 µm, while keeping the interface between the implant, cortical bone, bone marrow, and soft tissues intact. The implants of the second group, 10 specimens with between 6 and 20 measurement points on each specimen, were used for specifically obtaining the distribution of the released elements with reference to the implant tissue interface, using ion micro beam. The implantation time ranged from 12 weeks to 52 weeks.

A thin passive titanium dioxide, in its stoichiometric form, has a very high corrosion resistance, but the same conclusion can not be made on corrosion resistance of a surface which is not stoichiometrically titanium dioxide, or even a surface which is a composition of various elements and oxides. In practice, the implants available on the market have an oxide surface contaminated with other elements. The aim of this paper is to correlate clinical observations that show the deterioration of Ti made implants after certain period of insertion in the patients, and in vitro corrosion resistance of Ti implants with surface passive oxide layer. For this purpose, surface analysis of the retrieved failed implants were performed and in vivo animal experiments with relation to ion release from implants were done. Finally, on the basis of the clinical observation, in vivo animal test, and in vitro electrochemical corrosion test, a model is proposed to explain the corrosion and ion release from the Ti implant.

Nickel ion release from NiTi shape memory alloy is an issue for biomedical applications. This study was planned to study the effect of C${}^{+}$ implantation on nickel ion release and affinity of calcium phosphate precipitation on NiTi alloy. Four annealed samples are chosen for the present study; three samples with oxidation layer and the fourth without oxidation layer. X-ray diffraction (XRD) spectra reveal amorphization with ion implantation. Proton-induced X-ray emission (PIXE) result shows insignificant increase in Ni release in simulated body fluid (SBF) and calcium phosphate precipitation up to $8\times 10^{13}$ions/cm². Then Nickel contents show a sharp increase for greater ion doses. Corrosion potential decreases by increasing the dose but all the samples passivate after the same interval of time and at the same level of $V_{\mathrm{\text{SCE}}}$ in ringer lactate solution. Hardness of samples initially increases at greater rate (up to $8\times 10^{13}$ions/cm${}^2)$ and then increases with lesser rate. It is found that $8\times 10^{13}$ions/cm² ($\approx 10^{14})$ is a safer limit of implantation on NiTi alloy, this limit gives us lesser ion release, better hardness and reasonable hydroxyapatite incubation affinity.