Layer characteristics in strength-gradient multilayered yttria-stabilized zirconia

Inokoshi, Masanao; Liu, Hengyi; Yamamoto, Mao; Tonprasong, Watcharapong; Benino, Yasuhiko; Minakuchi, Shunsuke; Zhang, Fei; Meerbeek, Bart Van; Zhang, Fei

doi:10.1016/j.dental.2023.03.015

Cited by 19 publications

(2 citation statements)

References 27 publications

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“…Consistent with prior findings, these results support the correlation between Y 3+ content and flexural strength. These findings align with previous studies [48][49][50] reporting that the variation in Y 3+ content led to different c-ZrO 2 and t-ZrO 2 phase compositions and, concomitantly, a difference in flexural strength.…”

Section: Discussionsupporting

confidence: 92%

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials

Labetić,

Klaser,

Skoko

et al. 2024

Materials

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Nowadays, yttria (Y3+)-stabilized ZrO2 (Y-TZP) is the most commonly used material in dental prosthetics. Y-TZP dental ceramics are mainly stabilized via the addition of 3 mol% yttrium oxide (Y2O3). These ceramics exhibit excellent mechanical properties, including high flexural strength, fracture toughness, elastic modulus, etc. Some manufacturers have recently introduced a new class of dental materials with multilayer composition with the aim of combining the advantages of adding more or less Y2O3 to the ceramic composition in one Y-TZP material. The flexural strength values of multilayer Y-TZP may vary depending on the dimensions of the specimen, layer distributions, and especially the layer exposed on the maximum tension side, i.e., loading configuration. Although previous studies have examined the flexural strength of separate Y-TZP layers, capturing the flexural strength of multilayer Y-TZP is still challenging. However, one should keep in mind that multilayer flexural strength is important for clinical indications. The objective of this study is to compare the flexural strength of three distinct multilayer translucent Y-TZP materials made up of layers with different Y3+ contents. Rectangular samples (2 mm × 2 mm × 16 mm) were prepared from CAD/CAM discs using the milling machine Programill PM7 (Ivoclar Vivadent AG). Milled bars were tested for flexural strength in a three-point bending test (ISO 6872:2015) using a universal testing machine (Inspekt Duo 5kN; Hegewald & Peschke, Nossen, Germany) at a crosshead speed of 0.5 mm/min. Representative samples of each type of material were selected for quantitative and qualitative analysis of the microstructure. Representative samples of each type of material were selected for structural, mechanical, and microstructural analyses.

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Section: Discussionsupporting

confidence: 92%

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials

Labetić,

Klaser,

Skoko

et al. 2024

Materials

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“…However, because the cubic phase does not have the property of transformation toughening, the flexural strength values of these zirconia materials is lower [ 30 ]. Nowadays, there are also multilayer materials combining several types of zirconia in one milling disk (translucent layers located in the area of the incisal edges/cusp tips) and thus exhibiting a strength/translucency gradient [ 31 ]. However, for monolithic zirconia single crowns and FPDs made of 2nd generation zirconia, it has been shown that a facial veneer in the anterior and premolar region can achieve high patient satisfaction with regard to restoration esthetics without measurably increasing the restorations’ risk of technical complications [ 28 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures

Bömicke,

Boisserée,

Rammelsberg

et al. 2024

Clin Oral Invest

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Objectives The aim of this study was to compare failure load and initial damage in monolithic, partially veneered, and completely veneered (translucent) zirconia cantilevered fixed partial dentures (CFPDs), as well as completely veneered metal-ceramic CFPDs under different support and loading configurations. Materials and methods Eight test groups with anatomically congruent CFPDs (n = 8/group) were fabricated, differing in CFPD material/support structure/loading direction (load applied via steel ball (Ø 6 mm) 3 mm from the distal end of the pontic for axial loading with a 2-point contact on the inner cusp ridges of the buccal and oral cusps and 1.3 mm below the oral cusp tip for 30° oblique loading): (1) monolithic zirconia/CoCr abutment teeth/axial, (2) monolithic zirconia/CoCr abutment teeth/oblique, (3) partially veneered zirconia/CoCr abutment teeth/axial, (4) partially veneered zirconia/CoCr abutment teeth/oblique, (5) completely veneered zirconia/CoCr abutment teeth/axial, (6) completely veneered CoCr/CoCr abutment teeth/axial (control group), (7) partially veneered zirconia/implants/axial, and (8) partially veneered zirconia/natural teeth/axial. Restorations were artificially aged before failure testing. Statistical analysis was conducted using one-way ANOVA and Tukey post hoc tests. Results Mean failure loads ranged from 392 N (group 8) to 1181 N (group 1). Axially loaded monolithic zirconia CFPDs (group 1) and controls (group 6) showed significantly higher failure loads. Oblique loading significantly reduced failure loads for monolithic zirconia CFPDs (group 2). Initial damage was observed in all groups except monolithic zirconia groups, and fractography revealed design flaws (sharp edges at the occlusal boundary of the veneering window) in partially veneered zirconia CFPDs. Conclusions Monolithic zirconia CFPDs might be a viable alternative to completely veneered CoCr CFPDs in terms of fracture load. However, oblique loading of monolithic zirconia CFPDs should be avoided in clinical scenarios. Design improvements are required for partially veneered zirconia CFPDs to enhance their load-bearing capacity. Clinical relevance Monolithic zirconia may represent a viable all-ceramic alternative to the established metal-ceramic option for CFPD fabrication. However, in daily clinical practice, careful occlusal adjustment and regular monitoring should ensure that oblique loading of the cantilever is avoided.

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The Composition of Graded Dental Zirconias

Maharishi,

Horkley,

Unruh

et al. 2024

JOM

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Zirconia dental ceramics have evolved from uniform blocks of 3 mol.% yttria (3Y) to strength- and color-graded blocks containing 3 mol.% and 5 mol.% components. Relatively little is known about the graded materials’ compositions and microstructures. Concerns have been raised about aging and degradation. This study investigated the microstructure, elemental composition, and phase content of different zones of strength- and color-graded zirconia blocks using scanning electron microscopy, x-ray fluorescence, and x-ray diffraction. Specimens were made from green-state blocks using CAD/CAM machining and sintering. Two strength- and color-graded zirconia materials had different grain sizes, elemental compositions, and phase contents between their top and bottom zones, these data being internally consistent as well as being broadly consistent with prior compositional physical property data. A color-graded zirconia material did not exhibit substantial differences between its top and bottom zones, consistent with expectations and previously published data. Modeling phase content for complex yttria-doped zirconia crystal systems with multiple heterogeneous crystal lattices from XRD data was inherently difficult, which may account for the ranges among previously published data; authors should describe detailed methodologies. Detailed compositional data at the scale of the microstructure is needed to relate composition to phase content, physical behavior, including crack evolution.

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Layer characteristics in strength-gradient multilayered yttria-stabilized zirconia

Cited by 19 publications

References 27 publications

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures

The Composition of Graded Dental Zirconias

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