###### Abstract  
Aim of the present study was to investigate the bacterial adhesion to titanium (Ti) implant surfaces, different for composition and topographic features. Grade 4 and 5 turned (T-4, T-5), and mildly acid-etched (MA-4, MA-5) Ti 6 \(\times\) 1 mm disks were topographically analyzed by scanning electronic microscopy and 3D profilometry. Bacterial cultures (_Streptococcus sanguinis_) were in vitro seeded and, after two and six hours, adherent bacteria were quantified by colony-forming unit (CFU) counting. Ti samples were also exposed to the oral environment of six periodonotally healthy volunteers and, after 12 h, the formed biofilm was evaluated by CFU counting. Inter-group differences were tested by the Mann-Whitney U-Test (\(\alpha\) = 0.05). MA surfaces were significantly rougher than T ones, whereas no difference between grade 4 and grade 5 disks was detected. Significantly higher in vitro bacterial adhesion for MA than T disks was shown at two and six hours. Significantly higher values of CFU counting for MA than T surfaces and for grade 5 than grade 4 disks were found at the 12 h-ex vivo test. Bacterial adhesion showed to be sensitive to both Ti surface topography and composition, with possible implications on peri-implant tissue health maintenance.  
dental implants; bacterial adhesion; surface properties Article  
Bacterial Adhesion to Grade 4 and Grade 5 Turned and Mildly Acid-Etched Titanium Implant Surfaces: An In Vitro and Ex Vivo Study  
[PERSON], [PERSON], [PERSON], [PERSON], L.  
Furthermore, chemical surface properties and Ti composition also may affect the biological behavior and, besides, chemical, topographic and biological features have been demonstrated to be linked to each other [4].  
The main Ti alloy commonly used is the so-called commercially pure Ti, cpTi [11]. It is available in four grades numbered 1 to 4, according to the purity and the processing oxygen content [12], with the grade 4 cp-Ti, having the highest oxygen content (around 0.4%) and the best overall mechanical strength, which is most widely used for dental implants [11; 12]. Another Ti alloy used for manufacturing of surgical and, especially, prosthetic implant components is the Ti-6 Al-4V, also called grade 5 Ti, that shows superior strength, lower Young's modulus and acceptable biological properties [13].  
Little data about the effect of Ti composition on bacterial adhesion are available to date, with contrasting results. [PERSON] et al. [14], for instance, demonstrated significantly more _Porphyromonas gisigivalis_ attached on cp-Ti disks than on Ti-6 Al-4V alloy disks after six hours of anaerobic incubation. Differently, [PERSON] et al. [15] showed that grade 4 Ti surfaces were significantly less attractant for the _P. gingivalis_ than grade 5 Ti machined and laser-treated surfaces, whereas they found no detectable difference on sandblasted specimens.  
Such studies, however, were limited by the use of an exclusively in vitro mono-species experimental model, whereas the effect of both Ti composition and topography on the biofilm formation occurring in conditions closer to those of the oral cavity are lacking to date.  
Thus, the aim of the present study is to evaluate the interaction of oral bacteria with differently composed and treated Ti implant surfaces, and to verify how surface chemical and topographic properties may affect both bacterial adhesion in vitro, and biofilm formation ex vivo.