Influence of fluoride on the biotribocorrosion behaviour of titanium covered with biofilms

The use of dental implants has been increasing exponentially over the last few decades, making it essential to understand their degradation behaviour in the oral environment. Dental implants are generally made out of titanium (Ti) because of its outstanding biocompability and high corrosion resistance. Even though the degradation of Ti, in vivo, is minimal due to its ability to develop a highly stable passive oxide layer (TiO2); Ti is not inert to corrosive attack and presents poor wear resistance. Several studies have already been done on the corrosion and wear behaviour of titanium in artificial saliva and fluoride solutions. However, the microbial effect on the corrosion and wear of metallic biomaterials still remains unknown. The major novelty of this work relies on the first ever evaluation of the combined behaviour of wear and corrosion, process known as tribocorrosion, of Ti dental implants covered by biofilms in artificial saliva with different fluoride solutions. Therefore, the main aims of this work are: - to assess the effect of surface topography on the microbial adhesion and biofilm formation; - to evaluate the biotribological behaviour of Ti samples covered with mixed biofilms of Candida albicans and Streptococcus mutans, in artificial saliva solutions in the absence or presence of different fluoride concentrations; - to study the influence of mixed biofilms on the biotribocorrosion behaviour of Ti under an artificial saliva solution with fluoride; - to analyze the biocorrosion behaviour of Ti samples covered with mixed biofilms in artificial saliva solutions in the absence or presence of different fluoride concentrations