Purpose: This in vitro study measured the adhesive properties of 10-MDP and MPE containing resin cements, using two types of zirconia surface treatments; selective infiltration etching(SIE) and airborne particle abrasion (APA) to translucent zirconia (3M, ESPE). Statement of Problem: Due to translucent zirconia modified composition (alumina content reduced to tenth of its weight) bonding strength to different resin cements after different surface treatments should be investigated adequately. Materials and Methods:Sixty sintered Lava plus high translucency disks(3M,ESPE)were randomly divided into three study groups according to their surface treatment: (a) polished surface (control group); (b) air borne particle abraded (grit blasted) with 50 µm aluminum trioxide (APA); and (c) selective infiltration etching (SIE). Zirconia disks (15x2mm) were then bonded to 60 composite resin disks (8x4mm) using two different resin composite cements (Clearfil SA and Rely X). Resin-zirconia adhesion strength was evaluated using the microshear bond strength test (MSBS) after 24 hour of storage in deionized water at 37˚C. One way ANOVA and Scheffé s posthoc tests were used to analyze the data (p<0.001). Then fractured samples were studied under SEM and classified according to failure pattern. Results: Different types of resin cement and surface treatment significantly influenced the MSBS (P<0.001). The highest mean MSBS values were recorded with MDP containing resin cement (Clearfil SA) in both SIE (26.18 ±1.12 MPa) and APA (21.67±1.34) groups. Bond strength values were reduced significantly in control group when using the two types of cements. Regarding failure pattern, MDP groups showed cohesive and MPE and control groups showed adhesive type. Conclusion: SIE and APA in combination with 10-MDP containing resin cement established a strong durable bond to zirconia substrates than MPE groups. SIE and APA showed significant higher bond strength values than control groups.

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