Surface Bioactivation of Cobalt-base Alloy during Investment Casting Process

Statement of Problem: Cobalt-base alloys are widely used for fabrication of dental structures and dental and orthopedic surgical implants due to their biocompatibility. Application of coatings on the implants with bioactive materials improves their fixations in human body. Performing the operation during the casting process is very interesting due to the economical benefits and higher quality. The aim of this study was surface bioactivation of the dental Co-Cr-Mo alloy via performing the bioactive coating on the surface of the alloy during the investment casting process and evaluating the properties of the coating.Methods and Material: In the present experimental research, the Co-Cr-Mo alloy (ASTM F-75) specimens were poured into the molds prepared via investment mold technique. The internal surface of the molds was previously coated with hydroxyapatite powder via painting coating method. The obtained specimens were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and optical microscopy. The prepared specimens were immersed in simulated body fluid (SBF) at 37 °C for 4 weeks in order to evaluate the bioactivity of the surface of the specimens. A desired coating enriched with phosphor and calcium with a thickness of 100-160 micrometer was formed on the surface of Co-Cr-Mo alloy. Formation of bone-like apatite on the surface of coated Co-Cr-Mo alloy specimen, after 4 week immersion in SBF, was the indication of surface bioactivity of the obtained specimens. Preparation of hydroxyapatite coating during the investment casting process is an economical method to form a bioactive surface on the metallic cast implants. The surface bioactivity of the dental and orthopeadic implants can promote the osteointegration and better biological fixation.