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Nowadays, application of implants as a new method for replacing extracted teeth have been improved. So, many researches have been performed for improving the characteristics of implants. The aim of this study was to design and produce a desired coating in order to obtaining two goals including; improvement of the corrosion behavior of metallic endodontic implant and the bone osseointegration simultaneously. Stainless steel 316L (SS), cobalt-chromium alloy (Vit) and commercial pure titanium (cpTi) were chosen as metallic substrates and hydroxyapatite coating (HAC) were performed by plasma-spraying (PS) process on three different substrates. A novel double layer Hydroxyapatite/Titanium (HA/Ti) composite coating composed of a HA top layer and a Ti under layer was prepared using PS and physical vapor deposition (PVD) process respectively on SS. Structural characterization techniques including XRD, SEM and EDX were utilized to investigate the microstructure, morpholgy and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens behavior as an indication of biocmpatibility. Results indicated that the cpTi possesses the highest and SS the lowest corrosion resistance (highest corrosion current density) between uncoated substrates. This trend was independent to the type of physiological environment. The HA coating decreased the corrosion current density of HA coated metallic implants but did not change that trend. HAC acted as a mechanical barrier on the metallic substrate but could not prevent the interaction between metallic substrate and environment completely. The HA/Ti composite coating improved the corrosion behavior of SS. The corrosion current density of HA/Ti coated SS decreased and was exactly similar to single HA coated cpTi in physiological solutions. The results indicated that HA/Ti composite coated SS could be used as an endodontic implant and two goals including improvement of corrosion resistance (biocompatibiiity) and bone osseointegration could be obtained simultaneously.

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. Purpose: 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. Results: 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. Conclusion: 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. [ABSTRACT FROM AUTHOR]