Effect of artificial aging and surface treatment on bond strengths to dental zirconia

The objective of this project was to study the influence of artificial aging and surface treatment on the microtensile bond strengths (fiTBS) between zirconia and a phosphate monomer-based self-adhesive cement. Thirty zirconia disks (IPS e.max ZirCAD, Ivoclar Vivadent) were randomly assigned to two aging regimens: AR, used as received, which served as a control, and AG, artificial aging to simulate low-temperature degradation. Subsequently, the disks of each aging regimen were assigned to three surface treatments: NT, no surface treatment; CO, surface silicatization with CoJet sand (3M ESPE); and ZP, zirconia surface treated with Z-Prime Plus (Bisco Inc). Thirty discs were made of Filtek Z250 (3M ESPE) composite resin and luted to the zirconia discs using RelyX Unicem (3M ESPE). The specimens were sectioned with a diamond blade in X and Y directions to obtain bonded beams with a cross-section of 1.0 ± 0.2 mm. The beams were tested in tensile mode in a universal testing machine at a speed of 0.5 mm/min to measure μTBS. Selected beams were selected for fractographic analysis under the SEM. Statistical analysis was carried out with two- way analysis of variance and Dunnett T3 post hoc test at a significance level of 95c/<. The mean μTBS for the three AR subgroups (AUNT, AR-CO, and AR-ZP) were significantly higher than those of the corresponding AG groups (p 0.0001). Both AR-CO and AR-ZP resulted in statistically significant higher mean bond strengths than the group AR-NT (p <0.006 and p<0.0001, respectively). Both AG- CO and AG-ZP resulted in statistically significant higher mean bond strengths than the group AG-NT (both at p< 0.0001). Overall, AG decreased mean nTBS. Under the SEM, mixed failures showed residual cement attached to the zirconia side of the beams. CO resulted in a characteristic roughness of the zirconia surface. AR-ZP was the only group for which the amount of residual cement occupied at least 50# of the interface in mixed failures.