Análises da integridade da superfície de implantes dentais e da influência dos tratamentos de nitretação e amino-funcionalização na osteogênese

Dental implants receive surface treatments to create micro- and nanostructures on surface to increase the contacting area with bone, which favors osseointegration. However, the resistance of these structures in face of the friction against the bone tissue during the implant insertion is not evaluated yet. Thus, the objective in this study was to quantify by means of roughness parameters the surface wear caused by the insertion procedure in the bone tissue and to investigate the presence of loose titanium particles at bone-implant interface (Chapter 1); to evaluate the influence of plasma nitriding treatment on surface properties of titanium and on its biocompatibility (Chapter 2); and to investigate the protein adsorption in vitro and osteogenesis around amino-functionalized implants placed in rabbits (Chapter 3). In Chapter 1, roughness of three implants representing different geometries and surface treatments were evaluated by interferometry before and after insertion into bovine rib blocks. The blocks were also evaluated by microscopy to identify titanium particles at the interface. The amplitude of all roughness parameters were smaller after the insertion procedure for all implant groups and microscopic images revealed presence of loose titanium and aluminum particles at the interface, concentrated at the cortical crest. Therefore, it was concluded that moderately rough surfaces can release loose particles at the interface. In Chapter 2, titanium discs (12.7 × 2 mm) with moderately rough surface were nitrided by cold plasma. Human osteoblasts (SAOS-2) were cultivated on the discs for 1, 3, 5 and 7 days. Cell proliferation and differentiation were evaluated by MTS, production of alkaline phosphatase and by qPCR. It was observed that plasma nitriding increased the nitrogen content on surface, and also hardness, wettability and nanostructures. No significant difference between titanium and nitrided surface was seen on cell behavior. Therefore, it was concluded that nitriding treatment increase surface hardness and does not jeopardize the biocompatibility of titanium. In Chapter 3, titanium was amino-functionalized by 3-aminopropyltriethoxysilane. Protein profile was identified by mass spectroscopy after discs were immersed in human blood plasma for 3 h. To evaluate osteogenesis, titanium implants (3.75 × 6 mm) were placed in 10 New Zealand adult rabbits (1 in the femoral distal metaphysis and 2 in the tibial proximal metaphysis of both legs). The animals were sacrificed after 3 and 6 weeks and implants with adjacent bone were collected, fixed and included in resin blocks. After, 20 ?m thick slides were prepared at the central region of each implant and stained by toluidine blue. Histomorphometric analysis consisted of measuring the bone-to-implant contact (BIC). Treated surface exhibited higher amount of adsorbed proteins; however, lower relative abundance of fibronectin. No significant difference was identified between the groups for BIC values after 3 and 6 weeks. Therefore, amino-functionalization enhance protein adsorption but has no effect on early bone formation. (AU)