Evaluation of Influence of Firing Cycle Numbers on Shear Bond Strength in three All-Ceramic Systems

One of the weakest areas of these restorations is core and veneering porcelain interface. Regarding the necessity of performing multiple firing procedures to achieve improved color and contour, the aim of this study was to investigate the influence of multiple firing on core-veneer bond strength in zirconium based all ceramic restorations. Three types of all-ceramic systems, Zirconia, IPS emax CAD and IPS emax Press were used to prepare 54 ceramic core, in diameter of 8mm. Zirconia and IPS emax CAD were fabricated by CAD/CAM technology and IPS emax press cores, by using of pressing technique. Compatible porcelain was applied on the cores, with diameter of 5mm. The specimens were devided into three groups (N=18 in each group) according to the number of firing cycles: 3, 5 and 7 times. Core-veneer shear bond strength was measured by Universal testing machine, by cross head speed of 0. 5mm/min. Two way ANOVA and Tukey post hoc tests were selected to analyze the datas. shear bond stregth mean values in zirconia,IPS emax CAD and IPS emax press cores were 30.7, 29.7 and 29.9 MPa. Shear bond strength mean values in firing cycles of 3, 5 and 7 were 33.2, 29.2 and 27.8 MPa. These results revealed significant differences. shear bond strength of zirconia and IPS emax press did not have significant difference. Increasing the number of firing cycles from 3 up to 7, results in decreasing core-veneer shear bond strength.