Corrosion Behaviour and Biocompatibility of Titanium Screws Produced by Powder Injection Moulding (PIM) for Temporary Applications

Production of small and geometrically complex parts is a typical application of powder injection molding (PIM) process. The production of parts by PIM can produce a final texture with high roughness. The roughness is an important factor of the adhesion of the human cell on the implant. This intrinsic factor can facilitate high bone - implant fixation, but it reduces the corrosion resistance of implants. A design of a temporary screw probe adapted to peculiarities of this production process was proposed to use in implants as well as in electrochemical essays. This study aims at studying the effect of surface roughness on bone attachment of titanium implants and their corrosion resistance in a saline environment. Temporary implants were produced by PIM to characterize the influence of the temperature of sintering on the self-release process of the samples. The samples were classified into three groups according to sintering temperature (1250, 1270 and 1300°C). Screws were inserted in tibiae of New Zealand white rabbits (Oryctolagus cuniculus). After 4, 8 and 12 weeks the fixation in the bone was evaluated by histomorphometry (all threads along the implant and the three best consecutive threads were analyzed). An average surface recovery of 65 % after 12 weeks of implantation was obtained. Accelerated corrosion tests point to possible susceptibility to crevice corrosion of the sintered implants. Here, we compared some of the recent patents related to corrosion behavior and biocompatibility of titanium screws produced by PIM.