The effects of anodization and instrumentation on titanium abutment surface characteristics and biofilm formation

To assess the impact of anodization and instrumentation on titanium abutment surface characteristics (surface roughness and wettability) and biofilm formation (viability and mass).

Titanium discs were obtained from pre-milled abutment blanks made of titanium-6aluminum-7niobium alloy. Polished samples were divided into three groups: un-anodized, gold-anodized, and pink-anodized. Instrumentation methods included no-instrumentation, air polishing, and titanium scaling treatment. Surface roughness was measured using an optical profilometer, and wettability was determined by measuring the contact angles using the sessile drop method with an optical tensiometer. Biofilm formation by Streptococcus sanguinis was evaluated based on the biofilm viability and mass. The biofilm viability was evaluated through colony-forming unit counting (CFU/mL), and biofilm mass was assessed with crystal violet staining (mean absorbance measured at 490 nm, in optical density values). Sample surfaces before and after biofilm formation were also examined by scanning electron microscope (SEM). Two-way ANOVA was performed to determine the group differences, and Spearman's correlation (ρ) was used to analyze the correlation among surface roughness, wettability, and CFU/mL (α = 0.05).

Pink anodization significantly increased surface roughness (0.38 ± 0.07 µm, p < 0.001) compared to un-anodized samples (0.25 ± 0.01 µm), while gold anodization did not (0.24 ± 0.03 µm, p = 0.301). Among pink-anodized groups, air polishing resulted in significantly lower surface roughness (0.33 ± 0.08 µm) compared to titanium scaling (0.51 ± 0.11 µm, p < 0.001) and no instrument treatment (0.38 ± 0.07 µm, p = 0.050). Anodization significantly increased wettability (p < 0.001), while instrumentation with a titanium scaling decreased it (p < 0.001). The combination of un-anodized samples and titanium scaling treatment showed the lowest wettability with the highest contact angle (70.72 ± 2.63°). The biofilm viability, measured by CFU/mL, was significantly inhibited by anodization (p < 0.001) and air polishing (p < 0.001) while promoted by titanium scaling (p < 0.001). Gold-anodized titanium discs subjected to air polishing exhibited the lowest CFU/mL (279,420 ± 16,300), while un-anodized samples instrumented with a titanium scaler had the highest CFU/mL (945,580 ± 13,580). Biofilm mass, quantified by optical density values, was significantly inhibited by anodization (p < 0.001) as well as air polishing (p = 0.001). A moderate negative correlation was observed between CFU and wettability (ρ = -0.55, p < 0.001).

Gold- and pink-anodized titanium surfaces were more hydrophilic, leading to less biofilm formation than un-anodized ones. Biofilm formation was inhibited by air polishing while promoted by titanium scaling. Gold anodization combined with air polishing had the least biofilm formation and can be considered the preferred abutment anodization/instrumentation combination.