Comportamento de fratura de sistemas para restaurações cerâmicas

Abstract

Materials such as the alumina-based zircônia-reinforced glass-infiltrated ceramic (In-Ceram Zirconia) and the yttria partially stabilized tetragonal zirconia ceramic (Y-TZP) are considered the best options to replace metal frameworks (IE). However, the clinical behavior of these materials is still not clear. Thus, the objective of this study was to evaluate the effect of the type of IE material in the fracture behavior of prosthetic crowns. Specimens were fabricated using a metal die simulating a prepared tooth. Four groups were evaluated (n=10): YZ-C YTZP IE produced by CAD-CAM (In-Ceram YZ, Vita); IZ-C In-Ceram Zirconia (Vita) IE produced by CAD-CAM; IZ-S In-Ceram Zirconia (Vita) IE produced by slip-casting; MC metal IE (control). The IE were veneered with porcelain and cemented over the dies with resin cement. Specimens were tested until fracture using a universal testing machine with the compressive load being applied with a 30º angle by a spherical piston, in 37 ºC distilled water. Fractography was performed using a stereomicroscope and a SEM. Data were analyzed with Anova and Student-Newman-Keuls test (α=0.05). Significant differences were found between the groups (p=0.022). MC showed the highest mean fracture load, statistically similar to YZ-C and different from IZ-C and IZS groups. There was no statistical difference between YZ-C, IZ-C and IZ-S. MC and YZ-C showed, as failure mode, porcelain chipping. For IZ-C and IZ-S, both chipping and total failure, involving the porcelain and IE, were observed. The specimens fracture behavior was in agreement with the behavior reported for clinical failures. It was concluded that YZ-C and MC crowns present superior fracture load and a more favorable failure mode than In-Ceram Zircônia crowns, regardless of the fabrication type (CAD-CAM or slip-casting)