Fresagem em Zircônia: efeito do uso prolongado das brocas sobre a topografia superficial

Abstract

Objective: to evaluate the influence of diamond burs wear used to mill zirconia structures by the CAD/CAM system on the zirconia surface. Methods: 201 specimens were milled, using pre-sintered zirconia blocks, with dimensions of 8mm in diameter x 1,5mm in height by means of CAD/CAM technology (Amann Girrbach, Koblach-Austria). The sample milling process was performed using a set of three diamond burs, which were used until the end of useful life of 1.0 diamond bur, controlled by CAD/CAM system. After the milling process, the sintering process was carried out, followed by the polishing process, using mounted stones. The diamond burs were evaluated in scanning electron microscopy (SEM) before and after the milling process. Samples were also evaluated in SEM after the milling process. In addition, the surface roughness of the samples was evaluated using a non-contact optical profilometer to assess their topographic characteristics. Results: the SEM analysis of the diamond burs showed that at the end of the milling process, the diamonds of active zone were reduced. The SEM evaluation of the specimens showed similar surface grooves characteristics from the first to the last specimen. Optical microscopy revealed a Ra variation of 0,47 to 2,82 μm, with a mean roughness of 1.60 μm. Conclusion: The wear of the diamond burs during the milling process did not influence the surface roughness of the zirconia. However, the surface roughness obtained by the CAD/CAM milling process exceed the clinical acceptability threshold (0.2 μm).