Evaluation of zirconia surface properties after blasting with different particle size

In this study, the effect of blasting with different sizes of aluminum oxide particles (Al₂O₃) on surface quality was evaluated on Y-TZP (yttria stabilized tetragonal zirconia) and bond strength between Y-TZP and resin cement after storage. In Chapter 1, sixty samples of Y-TZP were randomly divided into three groups according to the treatments: control (untreated) and blasting (standoff distance 10 mm, 90° angle, 2.5 bar for 15 seconds) with Al₂O₃ particles (45 μm or 150 μm). To evaluate the contact angle, nine specimens were submitted to Fringe Projection Phase Shifting (FPPS). To quantify the roughness (Ra), the specimens (n = 10) were measured in profilometer (Mitutoyo Surf Test SE 1700) and characterized by the atomic force microscope (MFA) and scanning electron microscope (SEM). The bond strength (BS) was evaluated after 24 hours and 6 months and the failure mode was evaluated in mixed, adhesive or cohesive. The data from Ra and contact angle were subject to one-way ANOVA and Tukey's test (α = 0.05) and data from BS was subject to two-way ANOVA) and Tukey's test (α = 0.05). Blasting increased the superficial Ra of the Y-TZP (ρ = 0.0001), however, the alumina blasting had no effect on the contact angle (ρ = 0.76). The storage time did not affect the RU values (ρ = 0.1753) but the blasting (ρ = 0.0004) and the interaction between blasting and storage time (ρ = 0.02) did. Control and 45μm- blasted groups presented similar values of BS between 24 hours and 6 months water storage, while the 150μm-blasted group presented the highest value of BS when evaluated in 24h, nonetheless, this bond strength was reduced in presence of water. In Chapter 2, sixty Y-TZP samples were randomly divided into 6 groups according to the surface treatments previously described. Half of the specimens were submitted to mechanical fatigue while the other half was stored for 24 hours for flexural strength test, conducted on a universal test machine and the data of Y-TZP fractured were obtained in Newton, then, converted to Mega Pascal. Phase transformation was analyzed by Micro- Raman spectroscopy and X-ray diffraction (XRD). for characterization of crystals and evaluation of phase transformation. The data from flexural strength were subject to two-way ANOVA Tukey's test (α = 0.05). Blasting increased flexural strength (ρ = 0.0307); however, the mechanical fatigue decreased it (ρ = 0.0005). All groups showed presence of tetragonal phase only. Blasting with Al₂O₃ particles increases Y-TZP flexural strength, but mechanical fatigue decreased this strength without causing phase transformation. Thus, blasting with 45μm particles Al₂O₃ promoted better flexural strength without causing phase transformation and provided a constant bond strength after 6 months. (author)