In vitro and in vivo study of a sodium chloride impregnated microarc oxidation-treated titanium implant surface

Microarc oxidation (MAO) has been well-documented as an advantageous surface coating technique to improve implant osseointegration. Nevertheless, its strong susceptibility to bacteria critically impedes the development of MAO in clinical trials. Aimed at the efficient inhibition of bacterial invasion of MAO treated titanium (MAO-Ti) implants, a composite coating created by applying sodium chloride (NaCl) on a MAO-Ti implant surface layer was designed herein with the capacity to resist a broad spectrum of bacteria. In the present study, 10% NaCl was impregnated onto an optimized MAO-Ti implant to achieve a composite NaCl-MAO-Ti coating. First, Staphylococcus aureus (S. aureus), a frequently detected pathogen associated with peri-implantitis, was employed as an in vitro model. The visualization and quantification of S. aureus adhering to MAO-Ti and NaCl-MAO-Ti surfaces after incubation for 2, 4 and 24 h was described. Secondly, in an animal experiment, MAO-Ti and NaCl-MAO-Ti implants were placed into the tibia of male goats and these implants remained in situ for 9 weeks. The peri-implant soft tissue reactions, epithelial down growth and microorganisms separated from the inflammatory exudates were assessed during the whole process. The results of the in vitro study revealed that the NaCl-MAO-Ti implant surface significantly decreased the adhesion and multiplication of S. aureus compared to the untreated MAO-Ti. Moreover, the animal experiment established that the NaCl-MAO-Ti implants caused less peri-implant soft tissue infection and ultimately reduced the occurrence of peri-implantitis. Taken together, these data suggest that NaCl impregnated MAO-Ti implant products can effectively lower the risk of peri-implantitis and simultaneously preserve the osseointegration capacity of the MAO coating, which may help facilitate the application of NaCl-MAO-Ti implants in clinic trials.