Bonding Resin to Zirconia Ceramic--Which Method Is Best? Bond Strength of Resin Cements to a Zirconia Ceramic With Different Surface Treatments

Objective: To evaluate the effect of different metal primers and surface treatment methods on the bond strength of 2 resin cements to yttrium-stabilized tetragonal zirconia (Y-TZP) ceramic material. Methods: 240 cylindrical dentin specimens were cut from extracted human third molars. The same number of zirconia ceramic (Cercon) plates were made and assigned to 24 groups based on combinations of surface treatment, metal primer, and resin cement. The ceramic plates were treated in 1 of 3 ways: ultrasonic cleaning with isopropyl alcohol (control), air abrasion with 50-μm aluminum oxide particles, or Er:YAG laser irradiation. Each type of surface treatment was followed by Alloy Primer, Metal Primer II, Metaltite, or no coating (control). The dentin cylinders were bonded to the various substrates using either the self-etch cement system Panavia 2.0 or the etch-and-rinse system Calibra. Microshear bond strengths of the bonded specimens were determined using a miniature load testing device. Results: Air abrasion tended to improve bond strengths. Laser irradiation tended to have no effect but did significantly decrease bond strength in one treatment group. Metal primers tended to increase bond strengths. Differences in bond strengths between the 2 types of resin cement were generally not significant. Conclusions: Air abrasion and special functional monomers that chemically bond to zirconia can improve adhesion of resin cements to zirconia ceramics. Reviewer's Comments: Zirconia cannot be etched and silanated in the same way that feldspathic porcelain can, so alternative methods for resin bonding must be determined. A variety of metal primers have been developed in recent years. These contain special monomers including MDP (which has been used in Panavia and Clearfil for many years) that improve bonding of resins to metal alloys. Zirconia, of course, is a metal oxide, so it makes sense to test whether metal primers might improve the bond of resins to zirconia. This study used various combinations of ceramic surface treatment, type of metal primer, and type of resin cement. Thus, it generated a large volume of data that can be difficult to sort through. However, the clinically relevant findings are obvious. First, air abrasion of zirconia ceramic using 50-μm aluminum oxide particles improves adhesion of resin cements. Second, the use of a metal primer might further improve adhesion. (Reviewer-Edward J. Swift, Jr, DMD, MS).