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Dhital S, Rodrigues C, Zhang Y, Kim J. Viscoelastic finite element evaluation of transient and residual stresses in dental crowns: Design parametric study. J Mech Behav Biomed Mater 2019; 103:103545. [PMID: 31760273 DOI: 10.1016/j.jmbbm.2019.103545] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 11/14/2019] [Accepted: 11/18/2019] [Indexed: 10/25/2022]
Abstract
Porcelain-veneered zirconia (PVZ) are one of the popular choice for crown restorations. Veneer layer of these dental restorations, however, is susceptible to chipping and delamination due to the development of transient and residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effect of material property mismatch, veneer to core thickness ratio, and cooling rate on these transient and residual stresses of PVZ restorations. Three-dimensional viscoelastic finite element modelling (VFEM) was performed. The VFEM model was developed using the UEXPAN subroutine in ABAQUS software and was validated for transient and residual stresses in a sandwich seal problem with experimental data available. A good agreement between the simulated VFEM results and experimental data was obtained. Using validated VFEM, two PVZ systems (PM9/zirconia and ZirPress/zirconia), three veneer to core thickness ratios (2:1, 1:1 and 1:2), and two cooling rates controlled slow cooling at 1.74E-5 W/mm2°C (i.e. ~30 °C/min) and fast bench cooling at 1.74E-4 W/mm2°C (i.e. ~300 °C/min) were used. The results showed that PM9/zirconia has smaller thermal contraction mismatch, resulting in lesser residual stress (33.36 MPa) as compared to ZirPress/zirconia (37.94 MPa) for controlled cooling and 2:1 veneer to core ratio. In addition, in both systems with the decrease in veneer thickness, we observed a decrease in residual stresses developed. We also observed some effect of cooling rate on residual stresses. The controlled cooling resulted in lower residual stress (24.35 MPa) for PM9/zirconia with a 1:1 veneer to core thickness ratio as compared to bench cooling (28.04 MPa). The effect of cooling rate was more evident on transient stresses. For instance, in the PM9/zirconia with 1:1 thickness ratio model, the difference in transient stresses was 9.93 MPa between controlled and bench cooling. Therefore, properties such as elastic modulus and coefficient of thermal contraction (CTC), as well as the thickness ratio and cooling rate all play an important role in transient and residual stresses developed in the studied ceramic systems.
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Affiliation(s)
- Sukirti Dhital
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd, U-3037, Storrs, CT, 06269, USA
| | - Camila Rodrigues
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY, 10010, USA; Post-Graduation Program in Dental Sciences, Federal University of Santa Maria, 1184 Floriano Peixoto St, Santa Maria, RS, 97015-372, Brazil
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY, 10010, USA
| | - Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd, U-3037, Storrs, CT, 06269, USA.
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Investigations into the interface failure of yttria partially stabilised zirconia - porcelain dental prostheses through microscale residual stress and phase quantification. Dent Mater 2019; 35:1576-1593. [PMID: 31522759 DOI: 10.1016/j.dental.2019.08.098] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 08/15/2019] [Indexed: 11/22/2022]
Abstract
OBJECTIVES Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional toughness. Within these components the residual stress and crystallographic phase of YPSZ close to the interface are highly influential in the primary failure mode; near interface porcelain chipping. In order to improve present understanding of this behaviour, characterisation of these parameters is needed at an improved spatial resolution. METHODS In this study transmission micro-focus X-ray Diffraction, Raman spectroscopy, and focused ion beam milling residual stress analysis techniques have, for the first time, been used to quantify and cross-validate the microscale spatial variation of phase and residual stress of YPSZ in a prosthesis cross-section. RESULTS The results of all techniques were found to be comparable and complementary. Monoclinic YPSZ was observed within the first 10μm of the YPSZ-porcelain interface with a maximum volume fraction of 60%. Tensile stresses were observed within the first 150 μm of the interface with a maximum value of ≈300 MPa at 50 μm from the interface. The remainder of the coping was in mild compression at ≈-30MPa, with shear stresses of a similar magnitude also being induced by the YPSZ phase transformation. SIGNIFICANCE The analysis indicates that the interaction between phase transformation, residual stress and porcelain creep at YPSZ-porcelain interface results in a localised porcelain fracture toughness reduction. This explains the increased propensity of failure at this location, and can be used as a basis for improving prosthesis design.
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Kim J, Dhital S, Zhivago P, Kaizer MR, Zhang Y. Viscoelastic finite element analysis of residual stresses in porcelain-veneered zirconia dental crowns. J Mech Behav Biomed Mater 2018; 82:202-209. [PMID: 29621687 DOI: 10.1016/j.jmbbm.2018.03.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 03/12/2018] [Accepted: 03/15/2018] [Indexed: 11/29/2022]
Abstract
The main problem of porcelain-veneered zirconia (PVZ) dental restorations is chipping and delamination of veneering porcelain owing to the development of deleterious residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effects of cooling rate, thermal contraction coefficient and elastic modulus on residual stresses developed in PVZ dental crowns using viscoelastic finite element methods (VFEM). A three-dimensional VFEM model has been developed to predict residual stresses in PVZ structures using ABAQUS finite element software and user subroutines. First, the newly established model was validated with experimentally measured residual stress profiles using Vickers indentation on flat PVZ specimens. An excellent agreement between the model prediction and experimental data was found. Then, the model was used to predict residual stresses in more complex anatomically-correct crown systems. Two PVZ crown systems with different thermal contraction coefficients and porcelain moduli were studied: VM9/Y-TZP and LAVA/Y-TZP. A sequential dual-step finite element analysis was performed: heat transfer analysis and viscoelastic stress analysis. Controlled and bench convection cooling rates were simulated by applying different convective heat transfer coefficients 1.7E-5 W/mm2 °C (controlled cooling) and 0.6E-4 W/mm2 °C (bench cooling) on the crown surfaces exposed to the air. Rigorous viscoelastic finite element analysis revealed that controlled cooling results in lower maximum stresses in both veneer and core layers for the two PVZ systems relative to bench cooling. Better compatibility of thermal contraction coefficients between porcelain and zirconia and a lower porcelain modulus reduce residual stresses in both layers.
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Affiliation(s)
- Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd., U-3037, Storrs, CT 06269, United States.
| | - Sukirti Dhital
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd., U-3037, Storrs, CT 06269, United States
| | - Paul Zhivago
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, United States
| | - Marina R Kaizer
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, United States
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, United States
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ADM guidance-Ceramics: all-ceramic multilayer interfaces in dentistry. Dent Mater 2017; 33:585-598. [DOI: 10.1016/j.dental.2017.03.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 03/09/2017] [Indexed: 11/30/2022]
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Wendler M, Belli R, Petschelt A, Lohbauer U. Characterization of residual stresses in zirconia veneered bilayers assessed via sharp and blunt indentation. Dent Mater 2015; 31:948-57. [DOI: 10.1016/j.dental.2015.05.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 11/24/2022]
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Al-Amleh B, Neil Waddell J, Lyons K, Swain MV. Influence of veneering porcelain thickness and cooling rate on residual stresses in zirconia molar crowns. Dent Mater 2014; 30:271-80. [DOI: 10.1016/j.dental.2013.11.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Revised: 04/30/2013] [Accepted: 11/27/2013] [Indexed: 11/25/2022]
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Residual stresses in Y-TZP crowns due to changes in the thermal contraction coefficient of veneers. Dent Mater 2013; 29:594-601. [DOI: 10.1016/j.dental.2013.03.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 12/10/2012] [Accepted: 03/01/2013] [Indexed: 11/15/2022]
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Belli R, Monteiro S, Baratieri L, Katte H, Petschelt A, Lohbauer U. A Photoelastic Assessment of Residual Stresses in Zirconia-Veneer Crowns. J Dent Res 2012; 91:316-20. [DOI: 10.1177/0022034511435100] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Residual stresses within the veneer are linked to the high prevalence of veneer chipping observed in clinical trials of zirconia prostheses. We hypothesized that the thermal mismatch between the zirconia infrastructure and the veneer porcelain, as well as the rate used for cooling zirconia-veneer crowns, would be directly proportional to the magnitude of residual stresses built within the veneer layer. Two porcelains with different coefficients of thermal expansion were used to veneer zirconia copings, to create high or low thermal mismatches. The crowns were cooled according to a fast- or a slow-cooling protocol. The retardation of polarized light waves was used to calculate the residual stress magnitude and distribution across the veneer, according to the photoelasticity principle, in 1.0-mm-thick crown sections. While thermal mismatch was an important factor influencing the maximum stress development in the veneer, cooling rate had a minor role. Curved surfaces were preferential sites for stress concentration regardless of thermal mismatch or cooling rate.
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Affiliation(s)
- R. Belli
- Universidade Federal de Santa Catarina, Florianópolis, Brazil
- University of Erlangen, Glueckstrasse 11, Erlangen, 91054, Germany
| | - S. Monteiro
- Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - L.N. Baratieri
- Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | | | - A. Petschelt
- University of Erlangen, Glueckstrasse 11, Erlangen, 91054, Germany
| | - U. Lohbauer
- University of Erlangen, Glueckstrasse 11, Erlangen, 91054, Germany
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Choi JE, Waddell JN, Swain MV. Pressed ceramics onto zirconia. Part 2: Indentation fracture and influence of cooling rate on residual stresses. Dent Mater 2011; 27:1111-8. [DOI: 10.1016/j.dental.2011.08.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 06/14/2011] [Accepted: 08/17/2011] [Indexed: 10/17/2022]
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Mainjot AK, Schajer GS, Vanheusden AJ, Sadoun MJ. Residual stress measurement in veneering ceramic by hole-drilling. Dent Mater 2011; 27:439-44. [DOI: 10.1016/j.dental.2010.12.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 11/04/2010] [Accepted: 12/08/2010] [Indexed: 10/18/2022]
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Arman Y, Zor M, Ali Güngör M, Akan E, Aksoy S. Elastic-plastic finite elements analysis of transient and residual stresses in ceramo-metal restorations. J Biomech 2009; 42:2104-10. [DOI: 10.1016/j.jbiomech.2009.05.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 05/17/2009] [Accepted: 05/24/2009] [Indexed: 10/20/2022]
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Swain M. Unstable cracking (chipping) of veneering porcelain on all-ceramic dental crowns and fixed partial dentures. Acta Biomater 2009; 5:1668-77. [PMID: 19201268 DOI: 10.1016/j.actbio.2008.12.016] [Citation(s) in RCA: 364] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 12/07/2008] [Accepted: 12/22/2008] [Indexed: 11/26/2022]
Abstract
The central argument of this study is that residual stresses developed during the preparation of all-ceramic crowns and fixed partial dentures coupled with contact-induced cracking are the origin of the excessive chipping observed in clinical applications. The aim of this paper is to provide a simple basic analysis of the causes of residual stress development in ceramics and identify the key thermo-mechanical parameters responsible for these stresses and the resultant contact-induced failure. For simplicity, a bilayer planar geometry is considered. The key outcomes are the critical role of thermo-elastic properties and the thickness of the structures. The approach is then used to evaluate the propensity for unstable cracking of a range of crown structures, including substructures of a range of ceramics, and to show that two specific combinations are most prone to this behaviour, namely porcelain fused to glass ceramics and zirconia substrates. In addition, a simple approach for the minimization of the likelihood for such behaviour and chipping is proposed.
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Abstract
Previous studies showed that residual compressive stresses induced by thermal tempering retarded the growth of surface cracks in bilayered porcelain disks. The objectives of the present study were: (1) to determine whether thermal tempering by air blasting reduces the length of cracks induced by microhardness indentation in metal-ceramic disks, and (2) to use visco-elastic finite element analyses to calculate transient and residual stresses in metal-ceramic disks. Ni-Cr-Be disks, 16 mm in diameter and 0.3 mm in thickness, were prepared with a 0.5-mm-thick layer of opaque porcelain and a 1.5-mm-thick layer of body porcelain. Metal-porcelain combinations were selected to provide a range of thermal contraction mismatch values. The disks were fired to the maturing temperature of body porcelain and then were subjected to three cooling procedures: (1) slow cooling in a furnace (SC), (2) cooling in air (FC), and (3) air tempering (T) by blasting the surface of the body porcelain with compressed air. The lengths of cracks induced in the surface of the body porcelain by a microhardness indenter were measured immediately after indentation at 20 points along diametral lines. The results of Tukey's multiple-contrast analyses indicated that the mean crack lengths of air-tempered specimens were significantly smaller (p < or = 0.05) than the crack lengths of the fast-cooled and slow-cooled groups. Except for one case, there were no statistically significant differences in the mean crack lengths between FC and SC specimens independent of thermal contraction mismatch. Residual tensile stresses were calculated for SC and FC specimens for all thermal contraction mismatch cases, with the largest values being associated with combinations containing the body porcelain with the smaller contraction coefficient. Calculations by use of the model confirmed that tempering induces large residual compressive stresses in the surface of body porcelain for all of the thermal contraction mismatch cases included in this study.
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Affiliation(s)
- P H DeHoff
- Department of Mechanical Engineering & Engineering Science, College of Engineering, University of North Carolina at Charlotte 28223, USA
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