Corrosion Behavior of Titanium Zirconium Dental Implant Alloy

Objectives: The superior biological properties of titanium and its alloys are mainly attributed to the protective titanium oxide layer (TiO2). Nevertheless, dental implants are exposed to a dynamic physiological environment that may affect the stability of this layer. In-vitro evidence indicated salivary pH, fluoride, and temperature affected corrosion resistance and surface properties of different titanium alloys. The objectives of this study are to compare the corrosion behavior and surface changes of titanium zirconium dental implant alloy at different salivary pH values. Methods: In this in-vitro study, three types of dental implant materials, commercially pure titanium (CpTi), titanium grade V (Ti6Al4V), and a recently introduced titanium zirconium implant alloy (TiZr/Roxolid®) were selected. Eighteen samples were divided into six testing groups based on the alloy type and the artificial saliva pH (3 and 6.5). All specimens were mechanically polished following metallographic protocol. Standard three-electrode electrochemical tests were conducted under a simulated controlled oral environment. For surface characterization, titanium surfaces were analyzed using light interferometry microscopy. One-way ANOVA, post hoc Tukey, and independent t-test were used to analyze the data (α = 0.05). Results: At pH 3.0, all specimens had a significantly higher corrosion rate (Icorr) compared to pH 6.5 (CpTi: P=.008; Ti6Al4V: P=.002; TiZr: P=.028). Ti15Zr alloy had significantly lower Icorr compared to CpTi (P=.001) and Ti6Al4V (P=.004) alloys at acidic pH. CpTi (P=.001) and Ti6Al4V (P=.003) alloys had a significantly slower passivation rate of the oxide layer (Ipass) at pH3. For corrosion potential (Ecorr) this indicates the tendency to resist corrosion. There was no statistically significant difference between the two pHs for Ti6Al4V (P>.05). For pH3, TiZr alloy had significantly higher Ecorr indicating less corrosion compared to both CpTi (P=.004) and Ti6Al4V (P=.009). Images obtained by light interferometry microscopy showed increased surface roughness after the corrosion process.Conclusion: Acidic saliva had a negative effect on the corrosion resistance of the most commonly used dental implant titanium alloys. TiZr alloy exhibited higher corrosion resistance compared to the other titanium groups. This positive electrochemical behavior might be attributed to the inert nature of the zirconium.