Nonetheless, in vitro studies showed that Y-TZP exhibited higher flexural strength of 900–1200 MPa 7,9) and higher fracture toughness (K ic) of 5–9 MPa-m 1/2 because of transformation toughening 7,8,10) .Tensile stresses generated by an imminent crack at a crack tip induce a transformation of Y-TZP crystals from the metastable tetragonal phase to the monoclinic phase.Factors that cause chip-off fracture are related to the thickness and toughness of veneering porcelain, restoration geometry such as lack of proper veneering porcelain support, inadequate framework design, location of contact areas, and bond strength of veneering porcelain to zirconia 11,14) . reported that the bond strength of porcelain to zirconia was lower than that of porcelain to metal 14) .On the adhesion of resin cements to zirconia, it has seen significant improvements through the use of primers and surface modification treatments developed specifically for zirconia-resin bonding 15-20) .
Non-zirconia-based ceramics have been used for bridges and implant superstructures that exceed 4 units —including the molar teeth 8) .
On the other hand, the use of metals in PFM restorations gives rise to gingival discolorations and metal-related allergies 4-6) .
All-ceramic restorations can solve these problems triggered by the use of metals in PFM restorations.
Phase transformations were evaluated by X-ray diffraction (XRD).
Small cylinders of Panavia F2.0 resin cement were fabricated and placed on treated surfaces; samples were incubated at 37°C for 24 hours and were then subjected to microtensile tester for measurement of microshear bond strength.