In Vitro Effect of Acidic Challenges on the Physical Properties of Dental Prosthesis Artificial Teeth

Abstract Objective: To evaluate the effect of immersion and acid challenge with cola drink on color change (ΔE), Vickers hardness (VHN) and surface roughness (Ra) of artificial acrylic resin teeth. Material and Methods: The artificial teeth were divided into 6 groups (n= 8): TC (Trilux/Control), BC (Biotone/Control), TAC (Trilux/Acid challenge), BAC (Biotone/Acid challenge), TI (Trilux/Immersion) and BI (Biotone/Immersion). The teeth were embedded in acrylic resin and the labial side was serially polished to provide appropriate flat surface. The samples of TC, BC, TI, BI groups were immersed in artificial saliva and cola drink (coke) for 7 days, respectively. The acid challenge was performed with immersion of samples in coke for 5 min, and subsequently immersion in artificial saliva for 2h. This cycle was repeated at 4 times/day, during 7 days. The tests of VHN, ΔE and Ra were analyzed before and after the challenge and immersion groups. Data was analyzed by ANOVA, Tukey and T test (α = 0.05). Results: There was no difference in Ra values between groups after treatments. However, there was a decrease in VHN for all groups. BI (19.2 ± 0.3) presented significantly lower hardness than BAC (19.5 ± 0.9) and BC (20.2 ± 0.5). Groups BI (2.18 ± 0.41) and TI (1.50 ± 0.43) had statistically higher ΔE compared to the other groups. Conclusion: The hardness of resin teeth decreased after acid challenges, but the roughness surface was not affected. The color was more affected by the times of exposure in cola beverage and remineralization in artificial saliva, which were associated to the material degradation (AU).

Surface roughness and bond strength between Y-TZP and self-adhesive resin cement after air particle abrasion protocols.

The aim of this study was to evaluate the influence of different air particle abrasion (APA) protocols-with variations in particle types, duration of application, and the distance between the device tip and the ceramic-on the surface roughness (SR) of zirconia-based ceramic (yttria-stabilized tetragonal zirconia polycrystal [Y-TZP]) and the shear bond strength (SBS) between Y-TZP and resin cement. In total, 135 sintered Y-TZP blocks were polished and divided into 9 groups according to 3 factors: particle (alumina vs alumina coated with silica), duration (5 vs 10 seconds), and distance (contact vs 10 mm away). All 3 factors significantly influenced the SR values between the experimental groups and the control group. For SBS, only the particle type was a statistically significant factor. Results showed that air particle abrasion with silica-coated alumina resulted in higher SBS, even though the SR values associated with those groups were not the highest.

Can application of universal primers alone be a substitute for airborne-particle abrasion to improve adhesion of resin cement to zirconia?

PURPOSE: To determine whether universal primers alone can deliver similar levels of adhesion of resin cement to zirconia ceramic when compared to their application in conjunction with airborne-particle abrasion. MATERIALS AND METHODS: Sintered zirconia blocks (N = 160) (Lava, 3M ESPE), (5.25 × 5.25 × 3 mm3) were embedded in acrylic resin, polished, and randomly distributed into 16 groups (n = 10 per group), according to the factors "universal primer" (8 levels) and "air-particle abrasion" (2 levels): 1. ctr: control, without application of a universal primer; 2. AP: Alloy Primer; 3. MP: Monobond Plus; 4. MZP: Metal Zirconia Primer; 5. MZ: MZ Primer; 6. Sg: Signum Zirconia Bond; 7. SbU: Singlebond Universal; 8. ZP: Z Prime Plus. The universal primers were also used after air abrasion (A) of zirconia to form the following 8 groups: Ctr-A, AP-A, MP-A, MZP-A, MZ-A, Sg-A, SbU-A, and ZP-A. After ultrasonic cleaning, air abrasion was performed using Al2O3 particles (110 µm, 2.5 bar, 20 s at 10 mm) in a chairside air-abrasion device. After ultrasonic cleaning again, universal primers were applied according to each manufacturer's recommendation. The resin cement (RelyX ARC, 3M ESPE) was built up incrementally and photopolymerized on the zirconia surface using a silicone mold (Ø = 3.5, height = 3 mm). All specimens were stored in distilled water (60 days at 37°C) and then subjected to shear bond strength testing (SBS) in a universal testing machine (1 mm/min). On a separate set of zirconia specimens, contact angle measurements were made using the sessile drop technique with a goniometer after the application of universal primers on control and air-abraded zirconia surfaces. Data (MPa) were analyzed using one-way ANOVA, Tukey's test, and Student's t-test (α = 0.05). RESULTS: When universal primers were used alone, SbU presented significantly higher mean SBS (19.5 ± 5.8) that did the other primers (0 to 9.9 ± 6.6) (p = 0.001). When air abraded, the groups AP-A (14.1 ± 6.1), MP-A (15.9 ± 5.4), ZP-A (16.9 ± 7.3), SG-A (19.1 ± 2.1), SbU-A (12 ± 1.5) showed significant differences (p = 0.03). Adhesive performance of all universal primers was enhanced after air abrasion, with the exception of the SbU and MZ primers. After air abrasion, contact angle measurements were lower for the each primer (without air abrasion: 28.9 to 83.9; with air abrasion: 27.1 to 63.0), except for MZP. CONCLUSION: Air abrasion with 110 µm Al2O3 followed by universal primer application increased the bond strength of tested resin cement to zirconia, with the exception of SbU and MZ.