Tailoring the Bioactivity of Titanium by Plasma Sprayed Hydroxyapatite-Bioglass Composite Coating

Abstract

Titanium and its alloys are widely used as a potential implant material due to their excellent mechanical and corrosion resistant properties. However, the bioinertness of titanium results in poor osseointegration of the implant which may result in failure. To improve osseointegration on titanium, several surface modification techniques using plasma spraying, chemical vapour deposition, etc have been carried out. Hydroxyapatite and bioglass coating has been proved to be one of the best coatings to improve surface bioactivity. Bonding strength of hydroxyapatite is more as compared to bioglass while bioactivity of bioglass is higher than hydroxyapatite. To improve the implant stability and bioactivity, composite of hydroxyapatite and bioglass containing SiO2–Na2O–CaO–P2O5 system was used as coating material. Micro plasma spray technique was used for coating different composition of the composite on commercially pure titanium substrate. The processing parameters were maintained at 2kW power, 7.3 g/min of feed rate and the current parameter was varied at 35A and 40A respectively. The coated specimens were characterized using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. It was observed that there was no phase contamination on the coated specimens. The SEM micrographs revealed that the coated specimens exhibited microporoes on its surface. The in-vitro bioactivity study was performed by immersing the specimen in simulated body fluid (SBF) for 7 and 14 days. The immersed specimens were characterized using SEM and XRD to confirm apatite formation. It was evident that the results showed dense apatite formation on the coated specimens indicating enhanced bioactivity. From this study it is evident that composite (HAp+BG) coating showed more bioactivity than hydroxyapatite coating.