## 4 Discussion  
The present study aimed to evaluate the influence on the bone-to-implant contact (BIC) of non-thermal low-pressure argon plasma (NTLP-ArP) over two different implant surfaces: a mechanized implant surface, with a smooth surface (Ra \(<\) 0.5 \(\upmu\)m) and a resorbable blast media (RBM) surface that was moderately rough (Ra 1.0-2.0 \(\upmu\)m) [16]. It is widely known that the osteoblast activity is increased with micro-roughness ranging between 1 and 100 \(\upmu\)m when compared with untreated or smooth surfaces [17]. This is the reason why the industry develops new surface treatment techniques to achieve adequate topography, roughness, or chemical composition characteristics to improve cell viability and biocompatibility [2]. Regarding the chemical composition, [PERSON] et al. [18] showed that the TiO\({}_{2}\) surface treatment and composition influence the wettability and surface free energy, affecting the protein adsorption. In the cited study, the machined (smooth) surface showed a minimal area occupied by cells or connective tissue growing around. In addition, the cells cultured on rougher surfaces presented attributes of more differentiated osteoblasts [18]. However, these new surfaces which allow quick osseointegration present some disadvantages, like the presence of trace elements, such as metals, ions, detergents, or lubricants deposited on the surface [19] that may affect the body's response during the osseointegration process, leading to the undesirable formation of inflammatory tissue surrounding the implant [20; 21]. Recent research lines suggest the use of some techniques capable of enhancing the surface characteristics without modifying the topography or roughness features, as is the case with NTLP-ArP. Oseointegration represents a dynamic process both during its establishment and its maintenance. Several factors have been related to primary stability during the establishment phase, including local bone quality and quantity, and implant macro-design [22; 23; 24]. All of these come together in an adequate primary stability. In the early phase, the macro-design of the implant plays an essential role in primary stability. This primary stability is due to the strong contact and friction between the thread shape and the bone [25]. The bone formation begins with the angiogenesis process, and is initiated in the concavities rather than convexities of the implant threads due to the higher concentration of vessels inside these concavities. However, the precise mechanism is not yet completely elucidated. It seems that because the environment formed inside the cavities promotes mechanical forces, the concentration of gradients of chemotactic molecules and blood clot retention could drive vascular and bone cell migration [26]. The space created between the threads (called the chamber) is filled by the blood clot that is progressively replaced by a connective matrix with mesenchymal cells and surrounded by blood vessels [27]. The thread geometry not only affects the distribution of stress forces around the implant, but it also directly influences the size of the chamber and, indirectly, the bone healing. Therefore, the width, the length, and the thread shape all play an important role [28; 29]. In general, bone healing phases have been studied in animal models [25; 30; 31; 32; 33; 34]. In human studies, it was shown that the percentage of newly formed bone attached to the implant surface increased with time [35; 36]. One week after insertion, the osteoid deposit can be observed with areas of newly formed bone. This new bone gradually increases during the second week with the presence of osteoblasts and blood vessels. Meanwhile, in some pitch regions of the thread (areas that were responsible for primary mechanical stability), the bone tissue exhibited signs of bone remodeling [25]. Some studies have evaluated how the microtopography may affect the cellular response showing that local tissue growth is proportional to the substrate curvature, directly affecting the osteoblast behavior [37].