Abstract
The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.
Highlights
All-ceramic systems have been used as an esthetic alternative to porcelain-fused-to-metal (PFM) crowns and fixed partial dentures (FPD)
Artificial enamel abraded against porcelain (BL) had significantly higher material loss (0.217 mm3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other
Artificial enamel abraded against veneered crows (BL) had significantly higher material loss (0.217 mm3 ± 0.015) than those abraded against monolithic zirconia crows, polished (PM - 0.167 mm3 ± 0.02) and glazed (GM - 0.101 mm3 ± 0.03)
Summary
All-ceramic systems have been used as an esthetic alternative to porcelain-fused-to-metal (PFM) crowns and fixed partial dentures (FPD). Zirconia ceramics present superior mechanical properties than the other systems, due to its high flexural strength of 900 - 1400 MPa [1], that allows for the manufacturing of FPDs in high masticatory load areas. Zirconia presents three different crystalline configurations depending on the temperature range: Monoclinic, from room temperature to 1170 ̊C; tetragonal, from 1170 ̊C to 2370 ̊C; and cubic, at temperatures above 2370 ̊C. The tetragonal phase is related to the strongest mechanical properties of zirconia [2] and needs to be stabilized at room temperature. The stabilization of tetragonal zirconia at room temperature depends on the addition of oxides such as calcium (CaO), magnesium (MgO), Yttrium (Y2O3) or Ceria (CeO2) [3]. Yttria-tetragonal zirconia polycrystal (Y-TZP) is a zirconia-based ceramic stabilized with 3 mol% yttria
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