Effect of thermocycling immersion times on bond of ceramometals

Objective: The aim of this study was to evaluate the shear bond strength of Co-Cr(Bego-Germany) and Ni-Cr(Bego-Germany) metal alloys and the VM13 ceramic (VITA Zahnfabrik-Germany), both submitted to different thermocycling immersion`s time. Method: 30 metal-ceramic specimens were confectioned and standardized in cylindrical format. The shear bond strength test was evaluated in the specimens without thermocycling (G1) and after submitting them to thermocycling with 3.000 cycles (5ºC/55ºC±1) with different times of immersion: G2(30 '), G3(1 '). Shear bond strength tests were performed by using a special device to concentrate the strength at the metal/ceramic interface during the test using an Universal testing machine. The load was applied until the fracture of the specimens. Results: The results (MPa) observed for the experimental conditions showed for Co-Cr (mean±SD): G1- 85,68±21,20; G2- 74,71±6,15; G3-76,05±26,33; and for NiCr: G1- 101,02±13,55; G2- 74,71±6,15; G3- 70,04±20,26. The data was statistically analyzed by ANOVA (two-way) and Tukey(p<0,05) testxs. It was verified that the values of the G3 were lower compared with the G1 and the results didn't show significant statistic differences between G2 and G1. Conclusions: The authors concluded that the thermocycling immersion`s time of 1 minute influenced the values of shear bond strength for the groups.