Effect of phosphotungstic acid on surface properties and bond strength of resin cement to zirconia

Background: The purpose of this in vitro study was to evaluate the effect of phosphotungstic acid pre-treatment on the surface properties of zirconium oxide ceramics and the microtensile bond strength (µTBS) between zirconium oxide ceramics and resin cement. Methods A total of 26 sintered zirconia blocks were randomly divided according to surface pre-treatment into four groups; group C (n = 6): no treatment (control), group S (n = 6): air-borne particle abrasion followed by Silano Pen treatment, group P1 (n = 7): Phosphotungstic acid 1gm/ 50 mL, and group P2 (n = 7): Phosphotungstic acid 2gm/50 mL. From each group, one zirconia block was examined using X-Ray Diffraction and scanning electron microscope. Also, one zirconia block from groups P1 and P2 was examined using Fourier-transform infrared spectroscopy. A total of 20 zirconia blocks were bonded to corresponding pre-constructed composite blocks using adhesive resin cement. Each zirconia-composite assembly was sectioned to obtain microbars of 1 mm 2 . A 20 microbars from each group were selected and aged (3500 thermocycles between 5°C and 55°C), then the µTBS test was performed using a universal testing machine (0.5 mm/min). The µTBS results was analyzed using one-way ANOVA test. Results Group P2 recorded the highest µTBS (23.824 ± 5.9 MPa) between all studied groups, while Group C recorded the lowest µTBS (12.19 ± 4.67 MPa). One-way ANOVA revealed a significant difference ( P  < 0.05) between all groups. The mode of failure was predominantly adhesive in Groups C, P1, and S, while group P2 showed cohesive and adhesive failures. Conclusions The phosphotungstic acid (2gm/50 mL) improved the bond strength of zirconia ceramics without phase transformation and composition changes.