The Effect of Surface Pre-Treatment, Thermocycling, and Long-term Aging on the Tensile Bond Strength of Monolithic Lithium Disilicate Crowns Cemented to Zirconia Custom Implant Abutments

Objective: To evaluate the effect of surface pre-treatment on the retentive strength (RS) of CAD/CAM lithium disilicate (IPS e.max, e.max) crowns bonded to custom zirconia implant abutment replicas (ZrAbut) using three resin cements after thermocycling and long-term aging.;Methods: One hundred forty-four e.max crowns (n=8) were milled and bonded to 144 ZrAbut using Panavia 21 (P21), Multilink Hybrid Abutment (MHA), and RelyX Ultimate (RXU) adhesive resin cements. In the experimental group, 72 ZrAbut were treated with 50 mum aluminum oxide at 1 bar /14.5 psi 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 while another 48 were subjected to long-term aging for six months (ISO11405). Retentive Strength was measured in MegaPascals (MPa) using a pull-off 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 compared using three-way analysis of variance and Tukey-Kramer post-hoc test.;Results: Within the 24h-aging group, RS for all experimental groups was significantly higher (p<0.05) than control except for P21 where there was no difference between the experimental and control groups (p>0.05). Within the thermocycling and long-term aging groups, all cements in the experimental group displayed significantly higher RS than the control. Conclusions: Pre-treatment of custom zirconia implant abutments with 50 mum 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 and long-term aging.