## 1 Introduction  
Dating back to the first studies conducted by Professor [PERSON], the process of dental implant screw osseointegration has been recognized as an interfacial process that is controlled by the events that occur at the interface between the host tissue and the implant surface [1]. In the bone surrounding dental implants, cell behavior is determined by the treated surface of the implant [1; 2; 3].  
As a consequence, scientific research has devoted a lot of effort to the study of the superficial chemical and physical properties of implant screws and their effects on the osseointegration process [4; 5; 6; 7; 8; 9].  
Surface features considered most important are:  
* the chemical composition of the surface. Dental implants are mostly made of titanium which is an extremely biocompatible material thanks to its passivation. The surface, however, is unique in that it has a chemical composition that is not only dictated by the material it is made of, but also by peculiarly being a boundary layer (contact with the external atmosphere and the related effects),as well as all the processes that the device undergoes in its realization: turning, surface treatment, cleaning, packaging [10]. As a consequence, the surface chemical composition of implant screws is a separate variable and must always be independently verified;
* the topography of the surface: while the surface of the first generation implant screws was substantially only turned (machined), the current surfaces are roughened in a controlled way by means of processes that stimulate peri-implant bone regeneration through the effect of the roughness on the biological behavior of peri-implant tissues (affecting blood and its components, inflammatory cells, osteogenic cells). The surface treatments of dental implant screws have undergone an evolutionary process over the years, which has led to well-defined and widely studied topographies whose characteristics are usually defined quantitatively by roughness parameters.  
The study of the properties listed above is of great importance for understanding the characteristics of a dental implant and for assessing the accuracy and awareness adopted in the production process given the extensive and varied options available today.  
Moreover, not only an increasing number of surface modifications are constantly introduced but also different treatments are often applied in the different areas of the implant body in order to improve osseointegration in the apical portion while reducing the risk for plaque accumulation in the coronal part and favoring soft tissue integration [11; 12; 13; 14].  
In addition, recently, implants made of other materials, including zirconia, have been developed, the surfaces of which need to be further investigated [15; 16].  
The choice of the implant device to be inserted in a specific clinical case cannot prescind from the knowledge of the implant characteristics that might affect the clinical outcome.  
For these reasons, the surface characteristics of 5 different commercially available dental implants were studied in this investigation.  
This work was intended to measure surface properties deemed important for the intended clinical purpose of 5 different types of dental implants. In particular, the assessments took into consideration the chemical composition of the implant surface and the topography of the surface quantified by the roughness values.