A comparison of the shear bond strength between two zirconia cores cores on two porcelains porcelains proposed by the manufacturing company in two syhstems of VITA and IVOCLAR

This study aims at comparing and analyzing the shear bond strength of the two zirconia cores on two porcelains proposed by the manufacturing company in two systems of VITA and IVOCLAR In this laboratory study, at first, the tooth-like brass sample was made by the CNC machine. Then, using the CAD CAM machine, 20 zirconia cores of Vita in Ceram YZ Cubes and 20 zirconia cores of IPS e. max zirCAD were provided. Half of the cores were provided using Vita VM9 porcelain and the other half were veneered with the use of IPS e. max ceram. In groups one to four, Vita Core and Veneer, Vita Core and Ivoclar Veneer, Ivoclar Core and Vita Veneer, and Ivoclar Core and Veneer were used respectively. Afterwards, the samples were put under the static force in the Universal Test machine (UTM) with the speed of 0/5 mm per minute to bring about fracture. The type of fracture was determined by electronic microscope. Schmitz-Schulmeyer Test was applied to evaluate the shear bond strength of core-veneer. In order to analyze the data, Two-Way ANOVA and logestic regression were carried out using SPSS 19 (α=0. 05). The rate of shear bond strength for groups one to four were 10.85±2.67, 10.35±3.30, 10.35±3.30 and 6.72±2.47 mega pascal respectively. The type of core had no effects on shear bond strength (P=0. 869), but the veneer kind was important in the rate of shear bond strength (P=0.027). The Vita veneer showed a higher level of shear bond strength. After the microscopic evaluation, samples showed a combination of the cohesive fracture at the veneer layer and mixed (cohesive, adhesive) fracture at the edge of the two layers; No adhesive fracture between the zirconia cores and veneers was observed. The results show that the shear bond strength of zirconia core and the covering porcelain veneers and the fracture type are not influenced by the core type, but are affected by the type of veneer.