Titanium Surfaces and Detoxification Procedures: Effects of Bacterial Biofilm and Citric Acid Exposure on Oxide Layer Behavior

Abstract

Detoxification with citric acid is an effective method of biofilm removal from titanium (Ti) dental implant surfaces affected by peri-implantitis, but its effects on Ti surface properties is not well understood. This study aimed at evaluating the surface characteristics and biological response to Ti after bacterial biofilm formation followed by citric acid detoxification. Ti specimens were immersed with oral bacteria under aerobic (Streptococcus mutans, Streptococcus sanguinis, Streptococcus salivarius and Aggregatibacter actinomycetemcomitans) and anaerobic (aerobic polyculture with Fusobacterium nucleatum and Porphyromonas gingivalis) conditions for 4 h or 7 days (n = 3). Immersion was followed by rubbing treatment with 0.9% saline or 40% citric acid for 8 min. Post-treatment, the surface morphology and microstructure were studied by optical microscopy and Raman spectroscopy, respectively. Osteoblast viability after 3 days on Ti post-treatment was assessed. Electrochemical testing revealed corrosion behavior post-treatment while X-ray photoelectron spectroscopy indicated oxide layer state. While signs of pitting and corrosion attack on Ti exposed to bacteria and/or detoxification were evident, no surface oxide phase changes were detected. Samples treated with citric acid had lower polarization resistance and higher corrosion rate after aerobic and anaerobic immersion. Samples exposed to bacteria and citric acid treatment had higher oxide thickness under aerobic but not anaerobic immersion after 4 h and 7 days. Osteoblast viability was not significantly affected by immersion and treatment. Within the study’s limitations, citric acid detoxification on Ti post-bacterial exposure is not expected to adversely change oxide composition, thickness, and corrosion behavior while maintaining host cell growth.