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Bawazir M, Lim C, Arnés-Urgellés P, Lu M, Huang H, Zhang Y. Brittle-Ductile Threshold in Lithium Disilicate under Sharp Sliding Contact. J Dent Res 2024; 103:839-847. [PMID: 38877734 PMCID: PMC11307199 DOI: 10.1177/00220345241256279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2024] Open
Abstract
Computer-aided design (CAD)/computer-aided manufacturing (CAM) milling and handpiece grinding are critical procedures in the fabrication and adjustment of ceramic dental restorations. However, due to the formation of microfractures, these procedures are detrimental to the strength of ceramics. This study analyzes the damage associated with current brittle-regime grinding and presents a potential remedy in the application of a safer yet still efficient grinding regime known as "ductile-regime grinding." Disc-shaped specimens of a lithium disilicate glass-ceramic material (IPS e.max CAD) were obtained by cutting and crystallizing the lithium metasilicate CAD/CAM blanks (the so-called blue blocks) following the manufacturer's instructions. The discs were then polished to a 1 µm diamond suspension finish. Single-particle micro-scratch tests (n = 10) with a conical diamond indenter were conducted to reproduce basic modes of deformation and fracture. Key parameters such as coefficient of friction and penetration depth were recorded as a function of scratch load. Further, biaxial flexure strength tests (n = 6) were performed after applying various scratch loads to analyze their effects on ceramic strength. Scanning electron microscopy (SEM) and focused ion beam (FIB) were used to characterize surface and subsurface damage. Statistical analysis was performed using one-way analysis of variance and Tukey tests. While the SEM surface analysis of scratch tracks revealed the occurrence of both ductile and brittle removal modes, it failed to accurately determine the threshold load for the brittle-ductile transition. The threshold load for brittle-ductile transition was determined to be 70 mN based on FIB subsurface damage analyses in conjunction with strength degradation studies. Below 70 mN, the specimens exhibited neither strength degradation nor the formation of subsurface cracks. Determination of the brittle-ductile thresholds is significant because it sets a foundation for future research on the feasibility of implementing ductile-regime milling/grinding protocols for fabricating damage-free ceramic dental restorations.
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Affiliation(s)
- M. Bawazir
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Restorative Dentistry Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
| | - C.H. Lim
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - P. Arnés-Urgellés
- School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD, Australia
| | - M. Lu
- School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD, Australia
| | - H. Huang
- School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD, Australia
- School of Advanced Manufacturing, Sun Yat-sen University (Shenzhen Campus), China
| | - Y. Zhang
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Salah K, Sherif AH, Mandour MH, Nossair SA. Optical effect of rapid sintering protocols on different types of zirconia. J Prosthet Dent 2023; 130:253.e1-253.e7. [PMID: 37330359 DOI: 10.1016/j.prosdent.2023.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 05/07/2023] [Accepted: 05/09/2023] [Indexed: 06/19/2023]
Abstract
STATEMENT OF PROBLEM Rapid sintering protocols are available for the fabrication of zirconia restorations, but whether rapid sintering influences color or translucency is unclear. PURPOSE The purpose of this in vitro study was to investigate the effect of different rapid sintering protocols on the color and translucency of cubic and tetragonal zirconias. MATERIAL AND METHODS Sixty disk-shaped specimens of 1-mm-thick cubic (DD CubeX2) and tetragonal (DD Bio ZX2) zirconia were investigated. Specimens of each type of zirconia were divided into three groups: conventional, speed, and superspeed sintering protocols. The conventional group of each zirconia type served as the control for calculating color differences. Translucency for each group was assessed by the translucency parameter and contrast ratio. Two-way analysis of variance was used for statistical analysis of the data (α=.05). RESULTS The translucency of cubic and tetragonal zirconia decreased after speed and superspeed sintering (P<.001). Superspeed sintering resulted in a greater color change than speed sintering (P<.001). CONCLUSIONS Rapid sintering protocols produced a significant effect on the color and translucency of cubic and tetragonal zirconias.
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Affiliation(s)
- Kerolos Salah
- Former Postgraduate student, Department of Fixed Prosthodontics, Faculty of Oral and Dental Medicine, Future University, New Cairo, Egypt.
| | - Ashraf Hussein Sherif
- Professor, Department of Fixed Prosthodontics, Faculty of Oral and Dental Medicine, Future University, New Cairo, Egypt
| | - Mona H Mandour
- Professor, Department of Crown and Bridge, Faculty of Dental Medicine, Al-Azhar University, Girls' Branch, Cairo, Egypt
| | - Shereen Ahmed Nossair
- Assistant Professor, Department of Fixed Prosthodontics, Faculty of Oral and Dental Medicine, Future University, New Cairo, Egypt
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Machry RV, Dapieve KS, Cadore-Rodrigues AC, Werner A, de Jager N, Pereira GKR, Valandro LF, Kleverlaan CJ. Mechanical characterization of a multi-layered zirconia: Flexural strength, hardness, and fracture toughness of the different layers. J Mech Behav Biomed Mater 2022; 135:105455. [PMID: 36148725 DOI: 10.1016/j.jmbbm.2022.105455] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 08/30/2022] [Accepted: 09/06/2022] [Indexed: 10/31/2022]
Abstract
This study compared the flexural strength under monotonic (static - sσ) and cyclic load application (fatigue - fσ), hardness (H) and fracture toughness (KIC) of different layers of a multi-layered zirconia (IPS e.max ZirCAD MT Multi, Ivoclar). Each layer was sectioned, classified into three groups according to yttria content (4-YSZ, 4/5-YSZ and 5-YSZ), and shaped on samples for flexural strength and fracture toughness tests (bars: 1.0 × 1.0 × 11 mm); and Vickers hardness test (plates: 1.5 × 4.0 × 5.0 mm). Flexural strength under monotonic load application (sσ; n = 10) was obtained through two different devices (three-point-bending and ball-in-hole device) and fatigue flexural strength (fσ; n = 15; initial load: 10 N; step-size: 5 N; 10,000 cycles/step) was assessed using a ball-in-hole device under cyclic load application. Vickers hardness test (n = 5), fracture toughness test (n = 10), and additional analyzes (Finite Element Analysis - FEA, Energy-dispersive X-ray spectroscopy - EDS and Scanning Electron Microscopy - SEM) were also performed. No differences were found between the different devices in the monotonic flexural strength test, and FEA showed similar tensile stress distribution for the two devices. 4-YSZ showed higher values of flexural strength under monotonic and cyclic load application modes (sσ = 1114.73 MPa; fσ = 798.84 MPa), and fracture toughness (KIC = 3.90 MPa√m). 4/5-YSZ had an intermediate sσ; however, fσ was similar to 5-YSZ (404.00-429.36 MPa) and KIC similar to 4-YSZ (KIC = 3.66 MPa√m). No statistical differences were found for hardness and Weibull modulus for fatigue flexural strength data. The amount of yttria in the layer compositions increased from 4-YSZ to 5-YSZ, and larger zirconia crystals were observed in the topographic images of 5-YSZ. Failures in the flexural strength and toughness tests started from the face subjected to tensile stress. Different layers of the multi-layered zirconia blank presented distinct mechanical properties. 4-YSZ (cervical layer) presented the highest flexural strength under monotonic and cyclic loads (fatigue), and higher fracture toughness even similar to the transition layer (4/5-YSZ). Hardness was similar between the layers. The ball-in-hole device performed similarly to the three-point bending device and can be used as an alternative to the traditional method.
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Affiliation(s)
- Renan Vaz Machry
- MSciD-PhD Post-Graduate Program in Oral Science, Faculty of Odontology, Federal University of Santa Maria, 1000 Roraima Av., Santa Maria, Rio Grande do Sul, Brazil.
| | - Kiara Serafini Dapieve
- MSciD-PhD Post-Graduate Program in Oral Science, Faculty of Odontology, Federal University of Santa Maria, 1000 Roraima Av., Santa Maria, Rio Grande do Sul, Brazil.
| | - Ana Carolina Cadore-Rodrigues
- MSciD-PhD Post-Graduate Program in Oral Science, Faculty of Odontology, Federal University of Santa Maria, 1000 Roraima Av., Santa Maria, Rio Grande do Sul, Brazil.
| | - Arie Werner
- Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Noord-Holland, Netherlands.
| | - Niek de Jager
- Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Noord-Holland, Netherlands.
| | - Gabriel Kalil Rocha Pereira
- MSciD-PhD Post-Graduate Program in Oral Science, Faculty of Odontology, Federal University of Santa Maria, 1000 Roraima Av., Santa Maria, Rio Grande do Sul, Brazil.
| | - Luiz Felipe Valandro
- MSciD-PhD Post-Graduate Program in Oral Science, Faculty of Odontology, Federal University of Santa Maria, 1000 Roraima Av., Santa Maria, Rio Grande do Sul, Brazil.
| | - Cornelis Johannes Kleverlaan
- Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, Noord-Holland, Netherlands.
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Thickness and internal adjustment of monolithic resin composite milled crowns: Effect on the load-bearing capacity under fatigue. J Mech Behav Biomed Mater 2022; 134:105407. [DOI: 10.1016/j.jmbbm.2022.105407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/23/2022] [Accepted: 07/26/2022] [Indexed: 11/24/2022]
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