In vitro investigations indicated that Y-TZP holds flexural strength ranging from 900-1200 MPa and fracture toughness of 5-10 MPa/m2. However, as reported by Sailer et al. the failure incidence for zirconia ceramic restoration in 3 and 5 years turned out to be 13.0% and 15.2%, respectively [10]. Short-term and mid-term clinical observations indicate that chipping and fragmentation of veneering porcelain were the most common reasons for the failure of all-ceramic restorations. To decreasing the risk of chipping, it is crucial to improve the bond strength between zirconia and veneering porcelain [11-13]. In