Bonding Effectiveness to Zirconia With Different Surface Treatments

Objectives: To evaluate the reliability and micro-tensile bond strength (μTBS) of different mechanical surface treatments and adhesive strategies to zirconia.
Methods: 360 specimens of translucent zirconia (Prettau Anterior, Zirkonzahn) were fabricated and randomly assigned into three groups according to the mechanical surface treatment: (1) as-sintered (control), (2) sandblasted with aluminum oxide particles (50μm, 3bar, 15s), and (3) sandblasted with silica-modified aluminum oxide – Cojet sand (30μm, 3bar, 15s). Each group was further divided in three sub-groups, according to the adhesive strategy: (ZD) Z-Prime Plus/Duolink Universal (Bisco), (SR) ScotchBond Universal/Relyx Ultimate (3M ESPE), (P) Panavia SA Cement Plus (Kuraray). Two identically pre-treated specimens were bonded together. After the adhesive protocol, the specimens were stored in distilled water (37°C, 24h) and then subjected to a μTBS test. Failed bonded areas were examined by stereomicroscopy and SEM. EDS analysis was also performed. Data were statistically analyzed (two-way ANOVA and Weibull analysis) at a significance level of 5%.
Results: μTBS values were significantly influenced by the type of mechanical surface treatment (p<0.001) and the interaction between surface treatment and adhesive strategy (p<0.001). The adhesive strategies did not significantly affect the μTBS (p=0.051). Al₂O₃ and Cojet presented significantly higher μTBS values compared to the as-sintered groups (p<0.05). Al₂O₃ treated specimens showed significantly higher μTBS values than Cojet (p<0.05). When subjected to pre-treatment with Al₂O₃ the SR adhesive strategy presented significantly lower μTBS values when compared to other strategies. Weibull analysis results showed that is less reliable to adhere as-sintered zirconia than mechanically pre-treated zirconia. Failure mode analysis was in line with the μTBS data (as-sintered=50% adhesive; (2)=75% mixed; (3)=70% mixed).
Conclusions: Mechanical surface treatments significantly enhanced the μTBS between zirconia and resin cements. Al₂O₃ showed significant better results than Cojet. The choice of adhesive strategy was not significant, regardless of the mechanical surface treatment.