Bonding Orthodontic Resin Cement to Zirconium Oxide Under Load/Thermocycling

Objectives: Evaluate the microshear bond strength (µSBS) of orthodontic resin cement to monolithic zirconium oxide ceramic (MZ) under orthodontic load (OL) and thermo cycling effect(TC).
Methods: Glazed MZ (Zenostar, Ivoclar Vivadent) blocks were tested after air abrasion with 30-µm silica coated aluminum oxide (Al₂O₃) particles (CoJet, 3M Espe). All the specimens were randomly divided into 4 groups (n=15): G1, OL with TC; G2, OL without TC; G3, no OL with TC; and G4, no OL, no TC (control). After priming all specimen’s surfaces (Monobond-Plus, Ivoclar Vivadent) Orthodontic resin cement (Heliosit Orthodontic, Ivoclar Vivadent) was bonded using the Ultradent SBS system (2.3 mm cylinder) and light cured (Smartlite MAX, Dentsply, 1400 mW/cm², 40s). G1 and G2 were subjected to 70±15 g load perpendicular to the cylinder axis, G1 and G3 were thermo-cycled for 5000 cycles 5-55°C, 90s/cycle. G2 and G4 were stored in distilled water at 37±1°C.The bonded specimens were subjected to µSBS test (crosshead speed 0.5 mm/min). Data were analyzed using one-way ANOVA and Tukey studentized Range (HSD).
Results: Mean µSBS values (MPa) show there is a significant difference between the four groups (p<0.0001). Grouping by Tukey shows that G1 exhibited the highest µSBS (8.4±2.7 MPa), G4 (6.3±1 MPa) and G2 (5.8±1 MPa) as a group is second, and G2 and G3 (4.7±1 MPa) as a group was the lowest.
Conclusions: G1, which is the closest to clinical realty, yielded the best results. Note that the glazed surfaces were roughened with CoJet.

The authers thank Ivoclar Vivadent for donating the materials