Retention of Cemented Lithium Disilicate Crowns on Zirconia Implant Abutments

Objectives: To evaluate the effect of surface pre-treatment on the retentive strength of CAD/CAM lithium disilicate (IPS e.max, IPS) crowns bonded to custom zirconia implant abutment replicas (ZrAbut) using three resin cements after thermocycling.
Methods: Ninety-six IPS crowns (n=8) were milled and bonded to 96 ZrAbut using Panavia 21 (P21), Multilink Hybrid Abutment (MHA), and RelyX Ultimate (RXU) adhesive resin cements. In the experimental group, 48 ZrAbut were treated with 50μm aluminum oxide at 1 bar for 20s prior to bonding whereas the ZrAbut were not treated in the control group. All of the samples were stored at 37°C in 100% humidity for 24h. Forty-eight samples were then subjected to thermocycling (ISO11405). Retentive strength (RS, MPa) was measured using a pull-out test with a universal testing machine at a crosshead speed of 0.5 mm/min. Means and standard deviations of retentive strength were calculated, and means were compared using a three-way analysis of variance and a Tukey-Kramer PLSD test.
Results: Means (table) with the same superscripted letters are not different statistically. Within the 24h-aging group, RS for all experimental groups was significantly higher (p<0.01) than control except for P21 where there was no difference between the experimental and control groups (p>0.05). Within the thermocycling group, all cements in the experimental group displayed significantly higher RS than the control.
Conclusions: Pre-treatment of custom zirconia implant abutments with 50μm aluminum oxide prior to bonding IPS crowns significantly increased bond strength of MHA and RXU cements significantly after 24h aging, but not P21. Pre-treatment significantly increased bond strength of all three cements after thermocycling.