Electrochemical corrosion and hydrophilicity of anodized titanium versus Co-Cr removable partial denture frameworks

Cobalt chromium molybdenum (Co-Cr-Mo) alloys have long been the material of choice for removable partial denture (RPD) frameworks because of their mechanical strength and rigidity. However, despite their clinical reliability, they are susceptible to corrosion in the oral environment, leading to ion release, discoloration, and biocompatibility concerns. The development of titanium alloys, particularly anodized Ti-6Al-4V, provides an opportunity to overcome these limitations through superior corrosion resistance, surface hydrophilicity, and enhanced esthetics achieved by interference coloration.

This in vitro study aimed to compare the electrochemical corrosion resistance and surface wettability of anodized titanium (Ti-6Al-4V) frameworks with untreated Ti-6Al-4V and Co-Cr-Mo alloys fabricated for removable partial denture applications.

Disk-shaped specimens (n=20 per group) were fabricated by direct metal laser sintering (EOS M100; EOS GmbH Electro Optical Systems) using Ti-6Al-4V, anodized Ti-6Al-4V, and Co-Cr-Mo alloys. Surfaces were standardized by sequential grinding (400 to 2400 grit; Buehler) and polishing with 1-µm diamond paste; Allied HighTech. Specimens were ultrasonically cleaned in ethanol and air dried. Anodization was performed using a DC power supply (TP12001X; TekPower) in a 0.5-M trisodium phosphate electrolyte at 72 V for 2 minutes, resulting in a light pink oxide film simulating gingival shade. Electrochemical testing in artificial saliva (pH 6.5) was conducted using a galvanostat (Reference 600+; Gamry instruments) to assess open-circuit potential (OCP), potentiodynamic polarization (Tafel), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Surface wettability was determined using a contact angle goniometer; Ramé-Hart Instrument Co. Data were analyzed using 1-way ANOVA with the Tukey post hoc test (α=.05) after confirming normality (Shapiro-Wilk) and homogeneity of variance (Levene test).

Anodized Ti-6Al-4V showed markedly improved electrochemical performance, with the most noble OCP (0.29 V), lowest corrosion current density (7.18×10⁻⁸ A/cm²), and highest polarization resistance (5.4×10⁵ Ω·cm²). Ti-6Al-4V exhibited intermediate behavior, while Co-Cr-Mo presented the most active OCP and highest Icorr with the lowest Rp. These findings were supported by CV and EIS analyses, confirming superior passivation in the anodized group. Contact angle measurements confirmed significantly greater hydrophilicity for anodized Ti-6Al-4V (25 ±5 degree) than untreated Ti-6Al-4V (75 ±5 degree) and Co-Cr-Mo (85 ±5 degree).

Anodization significantly enhanced corrosion resistance and surface hydrophilicity compared with untreated Ti-6Al-4V and Co-Cr-Mo alloys. These findings suggest anodized titanium's clinical potential as a durable and esthetically superior alternative for RPD frameworks.