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The aim of this study was to evaluate the bond strength between an yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic and a luting agent when submitted to plasma etching surface treatment before and after thermocycling (TC) with 3000 cycles of 5°C-55°C. The null hypothesis was that the surface treatments and thermocycling would not influence the bond strength. A total of 160 Y-TZP ceramic blocks in 2 sizes (10 size 1 and 10 size 2 blocks in each group) were distributed into 8 groups: group C (control), no surface treatment; group C-TC, TC without prior surface treatment; group SAO, sandblasting with aluminum oxide (Al2O3); group SAO-TC, sandblasting with Al2O3 followed by TC; group SAOS, sandblasting with silica-coated Al2O3; group SAOS-TC, sandblasting with silica-coated Al2O3 followed by TC; group PE, plasma etching; and group PE-TC, plasma etching followed by TC. In each group, size 1 blocks were cemented to size 2 blocks to fabricate specimens for microshear bond strength testing (n = 10 per group). Cementation followed surface treatments (except in control groups) and preceded any TC. All specimens were cemented using a luting agent that contained 10-meth-acryloyloxydecyl dihydrogen phosphate (MDP). The specimens were submitted to a microshear bond strength test and the means were analyzed with a 2-factor analysis of variance and Tukey test. Group PE showed the highest bond strength value before thermocycling (17.31 MPa). After thermocycling, the highest value was observed in the SAO-TC group (9.73 MPa), and statistically significant differences were observed between SAOS-TC and SAO-TC (P < 0.05) and PE-TC and SAO-TC (P < 0.05). Plasma etching improved the bond strength values between the Y-TZP ceramic and MDP-containing luting agent before thermocycling. After thermocycling, all groups showed lower bond strength values., Competing Interests: Disclaimer: The authors report no conflicts of interest pertaining to any of the products or companies discussed in this article.

Purpose: This study evaluated the spatial and functional roughness parameters on air-abraded zirconia as a function of particle type and deposition pressure., Materials and Methods: Polished zirconia blocks (Cercon, Degussa/Dentsply) (N=30) with dimensions of 5 × 4 × 4 mm3 were air abraded according to 2 factors: a) particle type - 30-μm silica-coated alumina (CoJet) or alumina particles (45 μm); b) deposition pressure (1.5, 2.5 and 4.5 bar). Roughness parameters (Sdr, Vi, Sci and Svi) were measured in an optical profilometer (Wyko NT 1100) at the center of the air-abraded area (301.3 × 229.2 μm). Two measurements were made for each parameter from each surface. The means of each group were analyzed by 2-way ANOVA followed by Tukey's adjustment test and Student's t-test (alpha = 0.05)., Results: Both the particle type (p < 0.05) and deposition pressure (p < 0.05) significantly affected the roughness parameters. Interaction terms were significant except for Sci and Svi. With the increase in pressure from 1.5 to 4.5 bar, Sdr (CoJet 1.5: 15.7 ± 0.2; CoJet 4.5: 26.6 ± 0.2; alumina 1.5: 14.7 ± 0.2; alumina 4.5: 24.4 ± 0.2) and Vi (CoJet 1.5: 0.66 ± 0.01; CoJet 4.5: 1.37 ± 0.07; alumina 1.5: 0.62 ± 0.02; alumina 4.5: 1.19 ± 0.02) parameters showed a significant increase with both alumina and CoJet particles. Mean Sci values (CoJet 1.5: 1.62 ± 0.01, CoJet 4.5: 1.49 ± 0.02; alumina 1.5: 1.6 ± 0.03; alumina 4.5: 1.42 ± 0.04) and SVi (CoJet 1.5: 0.98 ± 0.01, CoJet 4.5: 0.112 ± 0.01; alumina 1.5: 0.98 ± 0.01, alumina 4.5: 0.12 ± 0.01) decreased significantly (p < 0.05) with the increase in pressure from 1.5 to 4.5 bar. The pressure increase from 2.5 to 4.5 bar did not cause any significant difference (p > 0.05) in these parameters for either particle type., Conclusion: Considering roughness parameters for micromechanical retention and parameters for adsorption mechanisms of adhesion, zirconia surfaces presented better morphological features when air abraded with silica-coated alumina than alumina particles at pressures higher than 1.5 bar. Particle deposition at 2.5 bar may be preferable to 4.5 bar pressure for avoiding possible deposition-related damage on zirconia, as there were no significant differences for the functional parameters.

The aim of this study was to evaluate the effect of novel surface treatments of Y-TZP ceramics on initial shear bond strengths to resin cement. Eighty-four samples (7 x 6 x 5 mm) were randomly divided into 6 groups (n=14): Group1 (G1), no treatment; Group 2 (G2), air-borne particle abrasion with silica-coated aluminum oxide particles; Group 3 (G3), vitreous application 1 + etching with hydrofluoric acid; Group 4 (G4), vitreous application 1 + tribosilicatization; Group 5 (G5), vitreous application 2 + etching; Group 6 (G6), vitreous application 2 + tribosilicatization. Surface roughness (Ra) evaluation was performed by optical profilometry, scanning electron microscopy, and X-ray spectroscopy. The samples were silanized, and resin cement cylinders (3 x 2 mm) were built on the treated surfaces, light-cured and submitted to shear testing (1 mm/min). The failure mode was evaluated by SEM. Bond strength data were statistically analyzed using 1-way ANOVA and Tukey's test (α=0.05). Bond strength results were significantly affected by surface treatments (P = 0.0001). G5 and G3 presented increased Ra parameters and showed highest bond strength results (17.8 ± 5.5 and 13.3 ± 4.1, respectively). Failure modes were mainly mixed in all groups except for G1. The results confirmed that the approach of coating surface-conditioned Y-TZP with a vitreous material increased the initial shear bond strength to resin cement.

The purpose of this study was to evaluate the effect of different heat-treatment strategies for a ceramic primer on the shear bond strength of a 10-methacryloyloxydecyl-dihydrogen-phosphate (MDP)-based resin cement to a yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. Specimens measuring 4.5 × 3.5 × 4.5 mm(3) were produced from Y-TZP presintered cubes and embedded in polymethyl methacrylate (PMMA). Following finishing, the specimens were cleaned using an ultrasound device and distilled water and randomly divided into 10 experimental groups (n=14) according to the heat treatment of the ceramic primer and aging condition. The strategies used for the experimental groups were: GC (control), without primer; G20, primer application at ambient temperature (20°C); G45, primer application + heat treatment at 45°C; G79, primer application + heat treatment at 79°C; and G100, primer application + heat treatment at 100°C. The specimens from the aging groups were submitted to thermal cycling (6000 cycles, 5°C/55°C, 30 seconds per bath) after 24 hours. A cylinder of MDP-based resin cement (2.4 mm in diameter) was constructed on the ceramic surface of the specimens of each experimental group and stored for 24 hours at 37°C. The specimens were submitted to a shear bond strength test (n=14). Thermal gravimetric analysis was performed on the ceramic primer. The data obtained were statistically analyzed by two-way analysis of variance and the Tukey test (α=0.05). The experimental group G79 without aging (7.23 ± 2.87 MPa) presented a significantly higher mean than the other experimental groups without aging (GC: 2.81 ± 1.5 MPa; G20: 3.38 ± 2.21 MPa; G100: 3.96 ± 1.57 MPa), showing no difference from G45 only (G45: 6 ± 3.63 MPa). All specimens of the aging groups debonded during thermocycling and were considered to present zero bond strength for the statistical analyses. In conclusion, heat treatment of the metal/zirconia primer improved bond strength under the initial condition but did not promote stable bonding under the aging condition.

Objectives: To test the hypothesis that multiple firing and silica deposition on the zirconia surface influence the bond strength to porcelain., Materials and Methods: Specimens were cut from yttria-stabilized zirconia blocks and sintered. Half of the specimens (group S) were silica coated (physical vapor deposition (PVD)) via reactive magnetron sputtering before porcelain veneering. The remaining specimens (group N) had no treatment before veneering. The contact angle before and after silica deposition was measured. Porcelain was applied on all specimens and submitted to two (N2 and S2) or three firing cycles (N3 and S3). The resulting porcelain-zirconia blocks were sectioned to obtain bar-shaped specimens with 1mm(2) of cross-sectional area. Specimens were attached to a universal testing machine and tested in tension until fracture. Fractured surfaces were examined using optical microscopy. Data were statistically analyzed using two-way ANOVA, Tukey's test (α=0.05) and Weibull analysis., Results: Specimens submitted to three firing cycles (N3 and S3) showed higher mean bond strength values than specimens fired twice (N2 and S2). Mean contact angle was lower for specimens with silica layer, but it had no effect on bond strength. Most fractures initiated at porcelain-zirconia interface and propagated through the porcelain., Significance: The molecular deposition of silica on the zirconia surface had no influence on bond strength to porcelain, while the number of porcelain firing cycles significantly affected the bond strength of the ceramic system, partially accepting the study hypothesis. Yet, the Weibull modulus values of S groups were significantly greater than the m values of N groups., (Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)