Avaliação da resistência à fratura de coroas totais confeccionadas pelo Sistema Zirkonzahn®, em função de diferentes agentes de cimentação

Abstract

The aim of this study was to evaluate the fracture resistance of allceramic zirconia crowns, submitted to thermal and mechanical fatigue. Sixty bovine incisors were prepared to receive complete-coverage all-ceramic crowns. The crowns were fully made with zirconia Y-TZP using the CAD/CAM (Computer-Aided Design / Computer-Aided Manufacturing) Zirkonzahn® system. The specimens were assigned to four groups (n=15) according to each luting agent used: G1 -zinc phosphate; G2 -resin cement; G3 -glass ionomer cement; and G4 -resin-modified glass ionomer cement. The crowns were cemented using a pneumatic press with a static load of 9 kgf and submitted to an aging thermal/mechanical fatigue test, considering 60,000 cycles for the mechanical (load: 84 N -frequency: 4 Hz) and 125 cycles (4 -55 °C) for the thermal mode. The fracture resistance test was carried out using a load machine (Instron) at a speed of 1 mm/min. Data were submitted to ANOVA and Tukey test. Fracture resistance of the crowns luted with resin modified glass ionomer was observed to be significantly lower (1182,68 N ± 112,24) than that of the crowns luted with zinc phosphate cement (1448,51 N ± 182,32) and glass ionomer (1389,86 N ± 126,88) (p <0.05). No statistically significant difference was found between G1 and G3 (p> 0.05). The crowns in G2 showed no significant difference (1358,15 N ± 272,95) from those in the other groups. The fracture resistance of zirconia crowns was influenced by the luting agents.