Surface morphology, roughness, and corrosion resistance of dental implants produced by additive manufacturing

Ti–6Al–4V alloy (ASTM F136) is the Ti alloy mainly used for machined dental and orthopedic implants. Additive manufacturing (AM) or additive layer manufacturing (ALM) is the industrial process name for 3D printing. The AM include some processes among them selective laser melting (SLM), and electron beam melting (EBM). The AM is used to make products with complex and customized geometries. However, these techniques have limitations in terms of surface finishing quality. Implants produced by AM have high roughness and the presence of partially unfused particles on the surface which decreases the reactions among the device and cells and proteins in the body environment. The objective of the present work is to compare the surface morphologies and corrosion resistance of machined and SLM Ti–6Al–4V samples before and after acid etching. The surface characterization was performed using scanning electron microscopy (SEM) and optical profilometry. The corrosion resistance was analyzed using open circuit potential (OCP), potentiodynamic polarization, chronoamperometry, and zero resistance amperometry. Galvanic corrosion of Ti–6Al–4V in contact with Co–Cr–Mo alloys was analyzed. The results showed that the presence of unfused particles on the Ti–6Al–4V SLM sample surface decreased the corrosion resistance. The hydrofluoric acid (HF) surface etching increased the corrosion resistance of the SLM samples. Ti–6Al–4V SLM treated with HF solution for 20 min showed the highest corrosion resistance and lowest roughness surface. After sanding, both machined and SLM Ti–6Al–4V samples showed similar corrosion resistance in the 0.9% NaCl electrolyte with and without fluoride.