Retention of zirconia crowns bonded with adhesive resin cements

Objectives: To measure retention of zirconia crowns cemented with an experimental (3M-ESPE) and 2 commercially available (Multilink Automix/Ivoclar, Panavia F2.0/Kuraray) cements under different surface preparation conditions (Table).

Methods: 50 extracted teeth (n=10) were embedded in brass holders and placed into a lathe to produce a uniform crown preparation (20 degree taper and 3mm height). An orientation groove was placed on the occlusal surface using a round bur and high-speed handpiece. Preparations were scanned using LAVA-COS (3M/ESPE) and the file sent to 3M ESPE Professional Lab where Lava Zirconia copings were milled. Each preparation was imaged with a digital microscope (Keyence/VHX-600) at 20X magnification to measure surface areas and calculate strength by dividing the failure load with bonded surface area. Finished crowns were fit to the preparation, margins checked for opening and fit (explorer does not catch). Crowns were randomly assigned to 5 groups (Table) and cemented following manufacturers' instructions.  A 2kg weight was placed on the crown during cementation. Margins were light cured. (Elipar S10/3M ESPE/1100mW/cm²). Specimens were stored (distilled water/37°C/24h), thermocycled (5-55°C/10,000cycles/15second dwell time) and load cycled using an acetyl stylus (20N/100,000cycles/1.2Hz). A metal rod was placed through the hole on the coping and attached to the upper member of an INSTRON (Model/5565) and loaded in tension (5mm/min) until debonding. Data were analyzed with ANOVA and Tukey/Kramer (p=0.05).

Results: (Mean±SD)

Materials/Manufacturer		Load (N)	Stress (MPa)
Exp.Cement/Sandblasted/50µ-Al203	3M ESPE	599.9±147.8	5.4±1.3
Exp.Cement/Sandblasted:50µ-Al203/Primed		716.6±110.5	6.5±1.2
Exp.Cement/Sandblasted:50µ-Al203+30µ-CoJet/Primed		635.2±210	5.1±1.6
Multilink Automix/ Sandblasted/50µ-Al203/Ivoclar Vivadent		393.3±158.2	3.4±1.4
Panavia F2.0/ Sandblasted/50µ-Al203/Kuraray		446.8±134	3.8±1

Conclusions: Multilink had lower retention compared to all experimental material groups (p<0.05). Difference in retention was also found for Panavia F2.0 and Experimental cement when applied on sandblasted and primed surface. Supported by a grant from 3M ESPE.