## 1 Introduction  
Since titanium (pure or in alloys) began to be used as a dental implant material in the 1960s, the goal has been to improve the design and surface of the different implants available on the market, as well as to develop new implants that improve osseointegration behavior, aimed at shortening healing times or, for example, improving primary stability in the face of low-density bone.  
Grade IV (commercially pure) or alloy titanium implants are used currently, with the Ti6 Al4V alloy being the most widely used one [1]. Pure titanium has high strength, while type V, thanks to the presence of elements such as vanadium or aluminum, has high resistance to corrosion, fracture, and fatigue [2; 3; 4]. On the other hand, titanium alloys have better mechanical properties than pure titanium [5].  
When machined surfaces have been compared with implants with surface treatment, it has been observed that the latter improve osseointegration by increasing bone-implant contact and therefore long-term survival rate. This is partly due to the chemical composition of the implant and also to its topographical characteristics [6].  
The main surface treatment methods are sandblasting, acid etching (there may be a combination of the latter two techniques, which is called SLA), or anodic oxidation. [7].  
Sandblasting is based on the use of particles to modify the surface of the implant. These are generally medium grain particles (250-500 \(\upmu\)m). The aim is to create surface macro-roughness [8]. Particles of alumina, titanium oxide, and corundum are usually used [9].  
In recent years, the technique of sandblasting with resorbable biocearamic particles such as hydroxyapatite, calcium phosphate, or tracticulum phosphate has been developed. They all replace the use of alumina as a sanding material to prevent these particles from interfering with the subsequent osseointegration of the implant [10].  
On the other hand, double acid etching is based on the immersion of the implant for several minutes in a mixture of acids, such as hydrofluoric acid with nitric acid or sulphuric acid with hydrochloric acid [11]. It intends to create micro-roughness with a topography based on craters and microwells on the surface of the implant [8; 12]. This procedure allows not only to increase the roughness, but also to remove surface contaminating particles derived from sandblasting or its manufacture, as they may interfere (sometimes with a negative effect) with the osteoconductivity of titanium, regardless of its proven biocompatibility [9]. Furthermore, it is also possible to create homogeneous micro-roughness surfaces.  
Other more recent techniques seek to unify several of these techniques, either through sandblasting by combination of different biocearamic particles or through a subsequent acid etching. Although there are approximately 1300 commercially available products with different surface treatments on the market, the literature has not yet described the ideal surface to achieve the objectives mentioned above [13].  
This study aims to carry out two in vitro studies. The first one is a surface characterization and the second one is a cell viability assay. Both studies were followed by an in vivo study. The working hypothesis was the suitability of the different surfaces in terms of appropriate biocompatibility and osseointegration, as they represent the surfaces used usually.