Development of surfaces anodically oxidized of titanium alloys and modified femtosecond laser and fatigue resistant

Abstract

The surface modification of implants aiming their osseointegration is a current theme and permeates many areas of research. It is therefore a challenge to obtain surfaces which ensure fixation asymptomatic of the material soon after surgery. Various physical, chemical and metallurgical processes are used to perform in a reliable, effective and reproductive way this modification. Nowadays, for orthopedic implants the state-of-art of this technology is represented by the use of a plasma spray for coating implantable components with pure titanium and hydroxyapatite. More recently, the laser process has been searched extensively, This process allows greater flexibility and reproducibility, besides producing nanostructured surfaces, which accelerate the osseointegration. However, all these processes have in common the effect of reducing the fatigue life of the components, which can lead to premature failure of implants.The idea of this project is to produce a surface highly osseointegrable that, simultaneously, keeps the fatigue life of the implants. It is based on producing a polished surface, which is first modified with the growth of an anodic oxide. Studies from our research group showed that this type of modification does not alter the fatigue life of the material, on the contrary, it may even increase it by introducing compressive residual stresses at the implant surface. Since this modification does not guarantee good surface characteristics for effective osseointegration, the anodic oxide formed will be modified in the sequence by femtosecond laser irradiation. Thus, there is the expectation that the modification is restricted to the anodic oxide formed and does not affect the substrate material, the main cause of the reduction in fatigue life observed in other processes. This idea is original and has not references in the technical literature.Thus, the application of laser anodically grown oxide on the surface of CP Ti and Ti-6Al-4V and Ti-6Al-7Nb intend to form nanoscale structures that would allow osteoconduction from the gene expression of osteoblasts.The process of growth of the oxide can be performed by anodization in phosphate buffer solution and then the oxide can be modified with laser with pulse duration on the order of 500 fentosegundos (ultrafast laser). Using this methodology aims to ensure the fatigue resistance of the material through the formation of oxide film on anatase allotropic form and modify this film by laser irradiation in order to form nanoscale structures on the surface and increase the effects of osteoblasts.The structure obtained will be analyzed by scanning electron microscopy to examine surface morphology, surface characteristics of interest underwent for evaluation of fatigue strength. The best results will be submitted to analysis of osteoconduction in vitro using human osteoblasts.In short, the goal is to find a highly osseointegrable surface while keeping the fatigue properties similar to those found on polished or anodically oxidized surfaces.