Citric acid reduces oral biofilm and influences the electrochemical behavior of titanium: An in situ and in vitro study

Background Citric acid (CA) has been suggested as an effective antimicrobial agent against biofilms formed on titanium. However, the antimicrobial effect of CA in biofilms formed in the oral environment and its effects on the physical properties of titanium surface remain unknown. Therefore, this study evaluated the antimicrobial effect of CA on in situ biofilm, whether this treatment favors the bacteria recolonization and its effect on the electrochemical properties of titanium. Methods In the in situ test, volunteers wore a palatal appliance containing titanium discs. After 7 days, the discs (N = 21) were exposed in vitro to the following treatments: immersion in 0.9% sodium chloride (control); 40% CA immersion; and 40% CA rubbing. Afterwards, these discs (N = 18) were exposed in vitro to new bacterial adhesion with Streptococcus sanguinis. New discs (N = 18) without biofilm were exposed to the treatments and subjected to electrochemical tests and surface characterization. Data were analyzed by one-way ANOVA followed by Tukey's HSD test. Results The CA groups showed a significant reduction (approximate to 5-log reduction) in the biofilm formed in situ compared with the control group (p < 0.05), but no difference was found between CA application methods (p = 0.680). The acid treatment did not favor the recolonization of bacteria (p = 0.629). CA treatment did not influence the polarization resistance and capacitance of the oxide film, but statistically enhanced the electrochemical stability of titanium. Conclusion Citric acid appears to be an effective clinical alternative for treatment of the main etiologic factor in dental implant failure, biofilm formation, enhancing electrochemical behavior of titanium.