A Comparative Study of Hydroxyapatite Coating Produced with Plasma Electrolytic Oxidation and Hydrothermal Treatment on Titanium Alloys: Ti6Al4V and Ti6Al7Nb for Dental Implants

Abstract

Titanium and Titanium alloys are considered perfect materials for applications in a human body, such as artificial joints and dental implants.  Ti6Al4V is a very common alloy used for dental implants, owing to its good mechanical properties and corrosion resistance. Nevertheless, because of uncertainties regarding the toxicity of vanadium and its influence on the human body, other titanium alloys containing no vanadium and retaining suitable properties are used. The aim of this study is to compare two viable titanium alloys, Ti6Al4V and Ti6Al7Nb, and to attain on their surface hydroxyapatite (HA) coating improving the osseointegration, as it simulates a human bone. In this work Ti6Al4V and Ti6Al7Nb were oxidized in a water solution of calcium acetate (Ca(CH3COO)2) and calcium glycerophosphate (Ca(PO4CH(CH2OH)2) by Plasma   Electrolytic Oxidation (PEO) for 20 minutes and then were hydrothermally treated (HTT) in water (pH=7) and in KOH solution (pH=11) for 2 hours at 200°C  in a pressurized reactor. The surface morphologies, elemental composition and phase components were characterized by Scanning Electron Microscopy, Energy Dispersive Spectroscopy and X-Ray Diffraction, respectively. The surface roughness was measured by Atomic Force Microscope (AFM) and thickness measurements were made by SEM and thickness gauge.  Also, corrosion tests were made to evaluate the corrosion behavior of the two alloys.