PurposeFiring protocols influence the mechanical properties of dental ceramics. This study examin... more PurposeFiring protocols influence the mechanical properties of dental ceramics. This study examined the impact of altering the cooling rate of mono‐ and multilayered 5 mol% yttria‐partially stabilized zirconia (5Y‐PSZ) on their strength.Materials and methodsNinety specimens (width × length × thickness = 10 × 20 × 2 mm) were prepared using 5Y‐PSZ monolayer (Mo: Cercon‐xt) and 5Y‐PSZ multilayered (Mu: Cercon‐xt ML) blocks. Randomly distributed specimens were sintered at the recommended firing schedule for three different categories of cooling rates (n = 15/group): slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). A universal testing machine with four‐point bending test was used to measure the flexural strength (σ). The microstructure, fracture characteristics, and chemical composition were evaluated by scanning electron microscope and energy‐dispersive spectroscopy. The monoclinic, tetragonal, and cubic phases were investigated using X‐ray diffraction. Two‐way ANOVA and post hoc Bonferroni comparisons were applied to determine the σ, (), and Weibull analysis was performed to determine the Weibull modulus (m) and characteristic strength (σ0).ResultsThe highest σ and σ0 (MPa) were seen for MuN (454.2 ± 62.0, 480.8 ± 62.9) followed by MuS (453.5 ± 52.6, 476.4 ± 54.3) and MoS (451.5 ± 44.5, 471.2 ± 46.6), whereas MuF had the lowest σ and σ0 (379.8 ± 50.2, 401.6 ± 51.3). The σ value of S‐cooling (452.5 ± 47.9) was higher than those for N‐cooling (443.4 ± 61.3) and F‐cooling (382.3 ± 58.0). The m‐value for MoS was the highest (11.4 ± 3.6), whereas that for MoF was the lowest (6.1 ± 1.6). Different cooling rates resulted in a significant difference in σ values (p < 0.05).ConclusionsS‐ and N‐cooling resulted in significantly higher flexural strength than that obtained by F‐cooling. Increasing the cooling rate of 5Y‐PSZ resulted in smaller grain size, less grain boundary integration, and higher t‐ to m‐transformation, leading to lower strength. Therefore, a slow and normal cooling rate was recommended to achieve the optimum strength for 5Y‐PSZ.
Journal of Esthetic and Restorative Dentistry, 2022
ObjectiveTo evaluate masking ability of different types and thicknesses of ceramics upon various ... more ObjectiveTo evaluate masking ability of different types and thicknesses of ceramics upon various substructures.Materials and MethodsDiscs (Ø 12 mm, thickness 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 mm) were prepared from Bruxzir‐Anterior® (Bc), Celtra‐DUO® (Cc), and Vita‐Suprinity® (Vc) (n = 15/group). Substructures (2 mm thickness) were prepared from natural dentine (Ds), tetracycline‐stained dentine (Ts), zirconia (Zs), resin composite (Rs), and cast metal (Ms). A spectrophotometer was used to measure the CIE L*a*b* color coordinates of a specimen. Masking ability was determined from the color difference (∆E00) of ceramics between before‐ and after combining with substructure using ANOVA and Bonferroni test (α = 0.05). ∆E00 value was compared with acceptable clinical threshold (∆E00 = 1.8) and an ideal threshold (∆E00 = 0.8).ResultsType‐thickness of ceramics and substructures were significantly affected ∆E00. Ts significantly influenced ∆E00 more than Rs, Ms, Zs, and Ds. N...
This study investigated the biaxial flexural strength of monolithic zirconia after being subjecte... more This study investigated the biaxial flexural strength of monolithic zirconia after being subjected to various post-sintering processes. Fifty-eight zirconia discs (1.2±0.2 mm thickness and 14±0.2 mm diameter)were randomly divided into four groups:1) As glazed (AG), receiving only a surface glaze;2) Finished and polished (FP)3) Finished, polished, and overglazed (FPO);and 4)Finished, polished, and heat-treated (FPHt); Biaxial flexural strength was tested, giving means of± SD of 1,626.43±184.38, 1,734.98±136.15, 1,636.92±130.11 and 1,590.78 ±161.74 MPa for the AG, FP, FPO and FPHt groups, respectively.There was no statistical significance among the tested groups (p>0.05); however, the FP group demonstrated the highest flexural strength.Overglazing and heat treatment after polishing did not decrease flexural strength,though the complexity of both the equipment and the procedures necessitated inconvenient post-processing protocol for this clinical situation.
This study evaluated the influence of three porcelain veneering techniques (conventional sintered... more This study evaluated the influence of three porcelain veneering techniques (conventional sintered, heat-pressed, CAD-fused) veneered to three Yttrium stabilized zirconia (Y-TZP) core materials (IPS emax ZirCAD (Zz), inCoris TZI (Zi), Cercon (Zc) on flexural strength. Y-TZP blanks (45 each) were prepared and fully sintered into disk shape (10 ±0.05 mm in ɸ, 0.5±0.01 mm thickness). Each type of cores was veneered with IPS emax Ceram (Pc) for conventional sintered technique, with IPS emax Zirpress (Ph) for heat-pressed technique, and with IPS emax CAD (Pf) for CAD-fused technique. Samples were adjusted on the veneer and glaze to result in 10±0.05 mm in ɸ and 1.5±0.01 mm thickness. Flexural strength was performed using piston on three balls technique at a cross head speed of 0.5 mm/min. Biaxial flexural strength was calculated using Roark and Young formulas and the reliability was analyzed using Weibull distribution. The biaxial flexural strength (Mean±SD; MPa) and Weibull modulus (m) w...
Introduction. Monolithic zirconia is able to achieve certain aesthetic, but its durability in res... more Introduction. Monolithic zirconia is able to achieve certain aesthetic, but its durability in resisting fracture has been questioned, as fractures often originate from margins of restoration. This study determined fracture resistance of highly translucent monolithic zirconia crowns with different margin designs in terms of marginal thickness and collar height.Materials and Methods. Zirconia blanks (Ceramill® Zolid HT+) were selected for the fabrication of zirconia crowns according to different designs, including varying margin thicknesses (light chamfer, CL; heavy chamfer, CH) and collar heights (no collar, NC; low collar, LC; high collar, HC), which resulted in CLNC, CLLC, CLHC, CHNC, CHLC, and CHHCgroups (15 crowns each). The crowns were seated on a metal die and loaded vertically through round end punch (θ = 10 mm), contacting with inclined planes of cusp in a testing machine with crosshead speed of 0.2 mm/min until fracture. Videos with a rate of 50 frames/second were used to re...
Objectives Firing protocols influence optical properties of dental ceramics. Effects of varying c... more Objectives Firing protocols influence optical properties of dental ceramics. Effects of varying cooling rates of monochrome and multilayer 5 mol% yttria-stabilized tetragonal polycrystalline (5YTZP) on optical properties are subjected for investigation. Materials and Methods Ninety specimens (width, length, thickness = 10 × 20 × 2 mm) were prepared from monochrome (Mo: Cercon xt) and multilayer (Mu: Cercon xt ML with cervical (C) and incisal (I) zoning) 5YTZP. Specimens were sintered and randomly treated with three cooling rates (n = 15/group): slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). Color appearance (∆EW), color appearance difference (∆E diff), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were evaluated in CIEL*a*b* (Commission International de I'Eclairage) system. ∆E diff was achieved from the coordinate difference of specimen to VITA classic shade A2. Microstructures and compositions were evaluated by scanning elect...
PurposeFiring protocols influence the mechanical properties of dental ceramics. This study examin... more PurposeFiring protocols influence the mechanical properties of dental ceramics. This study examined the impact of altering the cooling rate of mono‐ and multilayered 5 mol% yttria‐partially stabilized zirconia (5Y‐PSZ) on their strength.Materials and methodsNinety specimens (width × length × thickness = 10 × 20 × 2 mm) were prepared using 5Y‐PSZ monolayer (Mo: Cercon‐xt) and 5Y‐PSZ multilayered (Mu: Cercon‐xt ML) blocks. Randomly distributed specimens were sintered at the recommended firing schedule for three different categories of cooling rates (n = 15/group): slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). A universal testing machine with four‐point bending test was used to measure the flexural strength (σ). The microstructure, fracture characteristics, and chemical composition were evaluated by scanning electron microscope and energy‐dispersive spectroscopy. The monoclinic, tetragonal, and cubic phases were investigated using X‐ray diffraction. Two‐way ANOVA and post hoc Bonferroni comparisons were applied to determine the σ, (), and Weibull analysis was performed to determine the Weibull modulus (m) and characteristic strength (σ0).ResultsThe highest σ and σ0 (MPa) were seen for MuN (454.2 ± 62.0, 480.8 ± 62.9) followed by MuS (453.5 ± 52.6, 476.4 ± 54.3) and MoS (451.5 ± 44.5, 471.2 ± 46.6), whereas MuF had the lowest σ and σ0 (379.8 ± 50.2, 401.6 ± 51.3). The σ value of S‐cooling (452.5 ± 47.9) was higher than those for N‐cooling (443.4 ± 61.3) and F‐cooling (382.3 ± 58.0). The m‐value for MoS was the highest (11.4 ± 3.6), whereas that for MoF was the lowest (6.1 ± 1.6). Different cooling rates resulted in a significant difference in σ values (p < 0.05).ConclusionsS‐ and N‐cooling resulted in significantly higher flexural strength than that obtained by F‐cooling. Increasing the cooling rate of 5Y‐PSZ resulted in smaller grain size, less grain boundary integration, and higher t‐ to m‐transformation, leading to lower strength. Therefore, a slow and normal cooling rate was recommended to achieve the optimum strength for 5Y‐PSZ.
Journal of Esthetic and Restorative Dentistry, 2022
ObjectiveTo evaluate masking ability of different types and thicknesses of ceramics upon various ... more ObjectiveTo evaluate masking ability of different types and thicknesses of ceramics upon various substructures.Materials and MethodsDiscs (Ø 12 mm, thickness 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 mm) were prepared from Bruxzir‐Anterior® (Bc), Celtra‐DUO® (Cc), and Vita‐Suprinity® (Vc) (n = 15/group). Substructures (2 mm thickness) were prepared from natural dentine (Ds), tetracycline‐stained dentine (Ts), zirconia (Zs), resin composite (Rs), and cast metal (Ms). A spectrophotometer was used to measure the CIE L*a*b* color coordinates of a specimen. Masking ability was determined from the color difference (∆E00) of ceramics between before‐ and after combining with substructure using ANOVA and Bonferroni test (α = 0.05). ∆E00 value was compared with acceptable clinical threshold (∆E00 = 1.8) and an ideal threshold (∆E00 = 0.8).ResultsType‐thickness of ceramics and substructures were significantly affected ∆E00. Ts significantly influenced ∆E00 more than Rs, Ms, Zs, and Ds. N...
This study investigated the biaxial flexural strength of monolithic zirconia after being subjecte... more This study investigated the biaxial flexural strength of monolithic zirconia after being subjected to various post-sintering processes. Fifty-eight zirconia discs (1.2±0.2 mm thickness and 14±0.2 mm diameter)were randomly divided into four groups:1) As glazed (AG), receiving only a surface glaze;2) Finished and polished (FP)3) Finished, polished, and overglazed (FPO);and 4)Finished, polished, and heat-treated (FPHt); Biaxial flexural strength was tested, giving means of± SD of 1,626.43±184.38, 1,734.98±136.15, 1,636.92±130.11 and 1,590.78 ±161.74 MPa for the AG, FP, FPO and FPHt groups, respectively.There was no statistical significance among the tested groups (p>0.05); however, the FP group demonstrated the highest flexural strength.Overglazing and heat treatment after polishing did not decrease flexural strength,though the complexity of both the equipment and the procedures necessitated inconvenient post-processing protocol for this clinical situation.
This study evaluated the influence of three porcelain veneering techniques (conventional sintered... more This study evaluated the influence of three porcelain veneering techniques (conventional sintered, heat-pressed, CAD-fused) veneered to three Yttrium stabilized zirconia (Y-TZP) core materials (IPS emax ZirCAD (Zz), inCoris TZI (Zi), Cercon (Zc) on flexural strength. Y-TZP blanks (45 each) were prepared and fully sintered into disk shape (10 ±0.05 mm in ɸ, 0.5±0.01 mm thickness). Each type of cores was veneered with IPS emax Ceram (Pc) for conventional sintered technique, with IPS emax Zirpress (Ph) for heat-pressed technique, and with IPS emax CAD (Pf) for CAD-fused technique. Samples were adjusted on the veneer and glaze to result in 10±0.05 mm in ɸ and 1.5±0.01 mm thickness. Flexural strength was performed using piston on three balls technique at a cross head speed of 0.5 mm/min. Biaxial flexural strength was calculated using Roark and Young formulas and the reliability was analyzed using Weibull distribution. The biaxial flexural strength (Mean±SD; MPa) and Weibull modulus (m) w...
Introduction. Monolithic zirconia is able to achieve certain aesthetic, but its durability in res... more Introduction. Monolithic zirconia is able to achieve certain aesthetic, but its durability in resisting fracture has been questioned, as fractures often originate from margins of restoration. This study determined fracture resistance of highly translucent monolithic zirconia crowns with different margin designs in terms of marginal thickness and collar height.Materials and Methods. Zirconia blanks (Ceramill® Zolid HT+) were selected for the fabrication of zirconia crowns according to different designs, including varying margin thicknesses (light chamfer, CL; heavy chamfer, CH) and collar heights (no collar, NC; low collar, LC; high collar, HC), which resulted in CLNC, CLLC, CLHC, CHNC, CHLC, and CHHCgroups (15 crowns each). The crowns were seated on a metal die and loaded vertically through round end punch (θ = 10 mm), contacting with inclined planes of cusp in a testing machine with crosshead speed of 0.2 mm/min until fracture. Videos with a rate of 50 frames/second were used to re...
Objectives Firing protocols influence optical properties of dental ceramics. Effects of varying c... more Objectives Firing protocols influence optical properties of dental ceramics. Effects of varying cooling rates of monochrome and multilayer 5 mol% yttria-stabilized tetragonal polycrystalline (5YTZP) on optical properties are subjected for investigation. Materials and Methods Ninety specimens (width, length, thickness = 10 × 20 × 2 mm) were prepared from monochrome (Mo: Cercon xt) and multilayer (Mu: Cercon xt ML with cervical (C) and incisal (I) zoning) 5YTZP. Specimens were sintered and randomly treated with three cooling rates (n = 15/group): slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). Color appearance (∆EW), color appearance difference (∆E diff), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were evaluated in CIEL*a*b* (Commission International de I'Eclairage) system. ∆E diff was achieved from the coordinate difference of specimen to VITA classic shade A2. Microstructures and compositions were evaluated by scanning elect...
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