1
|
Shrestha R, Reddy N, Fredeen S, Zhang Y, Kim J. Functionally graded bi-material interface for Porcelain Veneered Zirconia dental crowns: A study using viscoelastic finite element analysis. Dent Mater 2024; 40:1267-1281. [PMID: 38876830 PMCID: PMC11260237 DOI: 10.1016/j.dental.2024.06.007] [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] [Received: 03/27/2024] [Revised: 05/30/2024] [Accepted: 06/03/2024] [Indexed: 06/16/2024]
Abstract
OBJECTIVES During the manufacturing of Porcelain Veneered Zirconia (PVZ) dental crowns, the veneer-core system undergoes high-temperature firing cycles and gets fused together which is then, under a controlled setting, cooled down to room temperature. During this cooling process, the mismatch in thermal properties between zirconia and porcelain leads to the development of transient and residual thermal stresses within the crown. These thermal stresses are inherent to the PVZ dental crown systems and render the crown structure weak, acting as a precursor to veneer chipping, fracture, and delamination. In this study, the introduction of an intermediate functionally graded material (FGM) layer at the bi-material interface is investigated as a potentially viable alternative for providing a smoother transition of properties between zirconia and porcelain in a PVZ crown system. METHODS Anatomically correct 3D crown models were developed for this study, with and without the FGM layer modeled at the bi-material interface. A viscoelastic finite element model was developed and validated for an anatomically correct bilayer PVZ crown system which was then used for predicting residual and transient stresses in the bilayer PVZ crown. Subsequently, the viscoelastic finite element model was further extended for the analysis of graded sublayers within the FGM layer, and this extended model was used for predicting the residual and transient stresses in the functionally graded PVZ crown, with an FGM layer at the bi-material interface. RESULTS The study showed that the introduction of an FGM layer at the bi-material interface has the potential to reduce the effects from transient and residual stresses within the PVZ crown system relative to a bilayer PVZ crown structure. Furthermore, the study revealed that the FGM layer causes stress redistribution to alleviate the stress concentration at the interfacial surface between porcelain and zirconia which can potentially enhance the durability of the PVZ crowns towards interfacial debonding or fracture. SIGNIFICANCE Thus, the use of an FGM layer at the bi-material interface shows a good prospect for enhancing the longevity of the PVZ dental crown restorations by alleviating the abrupt thermal property difference and relaxing thermal stresses.
Collapse
Affiliation(s)
- Rupesh Shrestha
- Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - Niyati Reddy
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA 19104, USA
| | - Steven Fredeen
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA 19104, USA
| | - Yu Zhang
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA 19104, USA.
| | - Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA.
| |
Collapse
|
2
|
Bonfante EA, Calamita M, Bergamo ETP. Indirect restorative systems-A narrative review. J ESTHET RESTOR DENT 2023; 35:84-104. [PMID: 36688803 DOI: 10.1111/jerd.13016] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 01/24/2023]
Abstract
OBJECTIVE The background and clinical understanding of the properties of currently available indirect restorative systems and fabrication methods is, along with manufacturer and evidence-based literature, an important starting point to guide the clinical selection of materials for tooth and/or implant supported reconstructions. Therefore, this review explores most indirect restorative systems available in the market, especially all-ceramic, along with aspects of manufacturing process, clinical survival rates, and esthetic outcomes. OVERVIEW Progressive incorporation of new technologies in the dental field and advancements in materials science have enabled the development/improvement of indirect restorative systems and treatment concepts in oral rehabilitation, resulting in reliable and predictable workflows and successful esthetic and functional outcomes. Indirect restorative systems have evolved from metal ceramics and polymers to glass ceramics, polycrystalline ceramics, and resin-matrix ceramics, aiming to improve not only biological and mechanical properties, but especially the optical properties and esthetic quality of the reconstructions, in attempt to mimic natural teeth. CONCLUSIONS Based on several clinical research, materials, and patient-related parameters, a decision tree for the selection of indirect restorative materials was suggested to guide clinicians in the rehabilitation process. CLINICAL SIGNIFICANCE The pace of materials development is faster than that of clinical research aimed to support their use. Since no single material provides an ideal solution to every case, professionals must continuously seek information from well designed, long-term clinical trials in order to incorporate or not new materials and technological advancements.
Collapse
Affiliation(s)
- Estevam A Bonfante
- Department of Prosthodontics and Periodontology, Bauru School of Dentistry - University of São Paulo, Bauru, SP, Brazil
| | - Marcelo Calamita
- Department of Restorative Dental Sciences at the University of Florida, Gainesville, Florida, USA
| | - Edmara T P Bergamo
- Department of Prosthodontics and Periodontology, Bauru School of Dentistry - University of São Paulo, Bauru, SP, Brazil
| |
Collapse
|
3
|
Cho MH, Seol HJ. Optical Properties, Microstructure, and Phase Fraction of Multi-Layered Monolithic Zirconia with and without Yttria-Gradient. MATERIALS (BASEL, SWITZERLAND) 2022; 16:41. [PMID: 36614380 PMCID: PMC9821384 DOI: 10.3390/ma16010041] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/12/2022] [Accepted: 12/19/2022] [Indexed: 06/17/2023]
Abstract
The differences in the optical properties of multi-layered zirconia with and without yttria-gradient are not fully understood. This study aimed to evaluate and compare the optical properties, related microstructures, and phase fractions of multi-layered zirconia with and without yttria-gradient. For this, multi-layered zirconia of 5 mol% yttria (5Y) stabilized (Katana STML) and 4Y/5Y stabilized (e.max MT Multi) were cut layerwise, sintered, and analyzed using the opalescence parameter (OP), average transmittance (AT%), translucency parameter (TP), and contrast ratio (CR). The average grain size and phase fractions were obtained from field-emission scanning electron micrographs and X-ray diffraction patterns, respectively. Although the TP values of Katana STML and e.max MT Multi did not show a significant difference (except for transition layer 1), the results of AT and CR showed that the translucency of e.max MT Multi was slightly higher than that of Katana STML (p < 0.05). The opalescence gradient was higher in Katana STML than in the e.max MT Multi. In both zirconia types, translucency increased from the dentin to enamel layer based on the AT, TP, and CR results, while OP decreased (p < 0.05). The higher translucency from the dentin to enamel layer in Katana STML was caused by the pigmentation gradient, while in e.max MT Multi, it was caused by the difference in phase fraction and the pigmentation gradient.
Collapse
Affiliation(s)
- Mi-Hyang Cho
- Department of Dental Lab, Wonkwang Health Science University, Iksan-si 54538, Republic of Korea
| | - Hyo-Joung Seol
- Department of Dental Materials, Dental and Life Science Institute, School of Dentistry, Pusan National University, Yangsan-si 50612, Republic of Korea
| |
Collapse
|
4
|
Jeong JI, Shin HJ, Kwon YH, Seol HJ. Effect of Cooling Rate on Mechanical Properties, Translucency, Opalescence, and Light Transmission Properties of Monolithic 4Y-TZP during Glazing. MATERIALS 2022; 15:ma15124357. [PMID: 35744423 PMCID: PMC9228759 DOI: 10.3390/ma15124357] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 06/10/2022] [Accepted: 06/17/2022] [Indexed: 11/16/2022]
Abstract
A standard cooling rate has not been established for glazing; therefore, the effects of the cooling rate on the properties of zirconia need to be evaluated to predict outcomes in clinical practice. 4Y-TZP glazed at three different cooling rates was analyzed to estimate the effect of cooling rate during glazing on the mechanical and optical properties. Hardness tests, field-emission scanning electron microscopy analysis, X-ray diffraction analysis, flexural strength measurement, and optical property evaluations were performed. When 4Y-TZP was glazed at a higher cooling rate (Cooling-1) than the normal cooling rate (Cooling-2), there was no significant difference in grain size, flexural strength, average transmittance, and translucency parameters. The hardness was slightly reduced. The opalescence parameter was reduced for the 2.03 mm thick specimens. When 4Y-TZP was glazed at a lower cooling rate (Cooling-3) than the normal cooling rate, there was no significant difference in hardness, grain size, flexural strength, and translucency parameters. In addition, the average transmittance and opalescence parameters were slightly reduced for the 0.52 and 2.03 mm specimens, respectively. The effects of the cooling rate during glazing on the mechanical and optical properties of 4Y-TZP appear to be minimal and clinically insignificant. Therefore, even if the cooling rate cannot be strictly controlled during glazing, the clinical outcomes will not be significantly affected.
Collapse
|
5
|
Hensel J, Reise M, Liebermann A, Buser R, Stawarczyk B. Impact of multiple firings on fracture load of veneered zirconia restorations. J Mech Behav Biomed Mater 2022; 130:105213. [DOI: 10.1016/j.jmbbm.2022.105213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 03/23/2022] [Accepted: 03/26/2022] [Indexed: 11/17/2022]
|
6
|
Fardin VP, Bonfante G, Coelho PG, Bergamo ETP, Bordin D, Janal MN, Tovar N, Witek L, Bonfante EA. Residual stress estimated by nanoindentation in pontics and abutments of veneered zirconia fixed dental prostheses. J Appl Oral Sci 2022; 30:e20210475. [PMID: 35476114 PMCID: PMC9041093 DOI: 10.1590/1678-7757-2021-0475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 01/10/2022] [Accepted: 01/19/2022] [Indexed: 11/22/2022] Open
Abstract
Glass ceramics' fractures in zirconia fixed dental prosthesis (FDP) remains a clinical challenge since it has higher fracture rates than the gold standard, metal ceramic FDP. Nanoindentation has been shown a reliable tool to determine residual stress of ceramic systems, which can ultimately correlate to failure-proneness. OBJECTIVES To assess residual tensile stress using nanoindentation in veneered three-unit zirconia FDPs at different surfaces of pontics and abutments. METHODOLOGY Three composite resin replicas of the maxillary first premolar and crown-prepared abutment first molar were made to obtain three-unit FDPs. The FDPs were veneered with glass ceramic containing fluorapatite crystals and resin cemented on the replicas, embedded in epoxy resin, sectioned, and polished. Each specimen was subjected to nanoindentation in the following regions of interest: 1) Mesial premolar abutment (MPMa); 2) Distal premolar abutment (DPMa); 3) Buccal premolar abutment (BPMa); 4) Lingual premolar abutment (LPMa); 5) Mesial premolar pontic (MPMp); 6) Distal premolar pontic (DPMp); 7) Buccal premolar pontic (BPMp); 8) Lingual premolar pontic (LPMp); 9) Mesial molar abutment (MMa); 10) Distal molar abutment (DMa); 11) Buccal molar abutment (BMa); and 12) Lingual molar abutment (LMa). Data were assessed using Linear Mixed Model and Least Significant Difference (95%) tests. RESULTS Pontics had significantly higher hardness values than premolar (p=0.001) and molar (p=0.007) abutments, suggesting lower residual stress levels. Marginal ridges yielded higher hardness values for connectors (DPMa, MMa, MPMp and DPMp) than for outer proximal surfaces of abutments (MPMa and DMa). The mesial marginal ridge of the premolar abutment (MPMa) had the lowest hardness values, suggesting higher residual stress concentration. CONCLUSIONS Residual stress in three-unit FDPs was lower in pontics than in abutments. The outer proximal surfaces of the abutments had the highest residual stress concentration.
Collapse
Affiliation(s)
- Vinicius Pavesi Fardin
- Universidade de São PauloFaculdade de Odontologia de BauruDepartamento de Prótese e PeriodontiaBauruSão PauloBrasilUniversidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Prótese e Periodontia, Bauru, São Paulo, Brasil.
| | - Gerson Bonfante
- Universidade de São PauloFaculdade de Odontologia de BauruDepartamento de Prótese e PeriodontiaBauruSão PauloBrasilUniversidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Prótese e Periodontia, Bauru, São Paulo, Brasil.
| | - Paulo G. Coelho
- New York University College of DentistryDepartment of BiomaterialsNew YorkUnited StatesNew York University College of Dentistry, Department of Biomaterials, New York, United States.
- New York University TandonSchool of EngineeringDepartment of Mechanical and Aerospace EngineeringBrooklynNew YorkUnited StatesNew York University Tandon, School of Engineering, Department of Mechanical and Aerospace Engineering, Brooklyn, New York, United States.
- New York University Grossman School of MedicineHansjörg Wyss Department of Plastic SurgeryNew YorkUnited StatesNew York University Grossman School of Medicine, Hansjörg Wyss Department of Plastic Surgery, New York, United States.
| | - Edmara T. P. Bergamo
- Universidade de São PauloFaculdade de Odontologia de BauruDepartamento de Prótese e PeriodontiaBauruSão PauloBrasilUniversidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Prótese e Periodontia, Bauru, São Paulo, Brasil.
| | - Dimorvan Bordin
- Universidade de GuarulhosGuarulhosSão PauloBrasilUniversidade de Guarulhos (UNG) – UNIVERITAS, Guarulhos, São Paulo, Brasil.
| | - Malvin N. Janal
- New York University College of DentistryDepartment of Epidemiology and Health PromotionNew YorkUnited StatesNew York University College of Dentistry, Department of Epidemiology and Health Promotion, New York, United States.
| | - Nick Tovar
- New York University College of DentistryDepartment of BiomaterialsNew YorkUnited StatesNew York University College of Dentistry, Department of Biomaterials, New York, United States.
| | - Lukasz Witek
- New York University College of DentistryDepartment of BiomaterialsNew YorkUnited StatesNew York University College of Dentistry, Department of Biomaterials, New York, United States.
- New York UniversityNYU Tandon School of EngineeringDepartment of Biomedical EngineeringBrooklynNYUnited StatesNew York University, NYU Tandon School of Engineering, Department of Biomedical Engineering, Brooklyn, NY, United States.
| | - Estevam A. Bonfante
- Universidade de São PauloFaculdade de Odontologia de BauruDepartamento de Prótese e PeriodontiaBauruSão PauloBrasilUniversidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Prótese e Periodontia, Bauru, São Paulo, Brasil.
| |
Collapse
|
7
|
Dhital S, Rodrigues C, Zhang Y, Kim J. Metal-ceramic and porcelain-veneered lithium disilicate crowns: a stress profile comparison using a viscoelastic finite element model. Comput Methods Biomech Biomed Engin 2022; 25:412-423. [PMID: 34289770 PMCID: PMC9903966 DOI: 10.1080/10255842.2021.1955869] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/08/2021] [Accepted: 07/12/2021] [Indexed: 02/09/2023]
Abstract
Metal-ceramics (MC) are one of the oldest dental restorative systems, which are considered to be the gold standard for full crown restoration. Porcelain-veneered lithium disilicate (PVLD), on the other hand, are newer material systems that have shown high survival rate in clinical follow-ups but needs to be studied more. This study compares the stresses developed in the single crowns made from newer PVLD system against those with MC configuration. For this comparison, influence of the layer thickness and cooling rates is also taken into consideration. An experimentally validated viscoelastic finite element model (VFEM) has been developed to predict the stress profile in these systems. Three-dimensional rotationally symmetric crowns were analyzed using this validated model for both material systems, three veneer to core thickness ratios (2:1, 1:1, 1:2), and two cooling rates: slow cooling at 1.74E-5 W/mm2K (∼30 K/min) and fast cooling at 1.74E-4 W/mm2K (∼300 K/min). PVLD showed lower values of transient and residual stresses than MC. The maximum tensile residual stresses in MC systems were observed in the cusp area, whereas those in PVLD were located in the central fossa. With the reduction in veneer layer, there was reduction in residual stress in MC; however, the veneer thickness had little to no effect in PVLD. The effect of cooling rate was also evident as slow cooling resulted in lower residual and tensile stresses for both material systems.
Collapse
Affiliation(s)
- Sukirti Dhital
- Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT, USA
| | - Camila Rodrigues
- Graduate Program in Dental Sciences, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Yu Zhang
- Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, PA, USA
| | - Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT, USA
| |
Collapse
|
8
|
Shelar P, Abdolvand H, Butler S. On the behaviour of zirconia-based dental materials: A review. J Mech Behav Biomed Mater 2021; 124:104861. [PMID: 34600431 DOI: 10.1016/j.jmbbm.2021.104861] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 11/28/2022]
Abstract
Zirconia-based dental materials are extensively used in clinical practice due to their tooth-like appearance, biofunctionality, biocompatibility, and affordability. However, premature clinical failures of veneering porcelains raise a concern about their integrity. Extensive studies have been performed over a decade to resolve this issue, but it is challenging to reference all information effectively. A single source identifying the significance of potential parameters on material performance has not previously been available. An evidence-based meta-narrative review technique was used to review the characteristic parameters that can affect the overall behaviour of zirconia-based materials. Keywords were chosen to assess manuscripts based on scientific coherence with this paper's research objective. Online keyword searches were carried out on ScienceDirect, PubMed, and SAGE databases for relevant published manuscripts from year 1985-2020.261 out of 3170 identified manuscripts were included. A total of 10 parameters were identified and classified into the material, manufacturing, and geometric aspects. The effect of every parameter was reviewed on the performance of the material. A discrepancy in findings was observed and is attributed to the fact that there is no standard methodology. This review acts as a single source that summarizes various parameters' contribution to zirconia-based dental materials' performance. This review facilitates manufacturing improvements by accounting for every parameter's effect on overall performance.
Collapse
Affiliation(s)
- Prashant Shelar
- Department of Mechanical & Materials Engineering, Western University, London, Ontario, Canada
| | - Hamidreza Abdolvand
- Department of Mechanical & Materials Engineering, Western University, London, Ontario, Canada
| | - Sheila Butler
- Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada.
| |
Collapse
|
9
|
Rodrigues CS, Dhital S, Kim J, May LG, Wolff MS, Zhang Y. Residual stresses explaining clinical fractures of bilayer zirconia and lithium disilicate crowns: A VFEM study. Dent Mater 2021; 37:1655-1666. [PMID: 34481666 DOI: 10.1016/j.dental.2021.08.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 08/24/2021] [Accepted: 08/25/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To understand the stress development in porcelain-veneered zirconia (PVZ) and porcelain-veneered lithium disilicate (PVLD) crowns with different veneer/core thickness ratios and cooling rates. To provide design guidelines for better performing bilayer restorations with the aid of Viscoelastic Finite Element Method (VFEM). METHODS The VFEM was validated by comparing the predicted residual stresses with experimental measurements. Then, the model was used to predict transient and residual stresses in the two bilayer systems. Models with two different veneer/core thickness ratios were prepared (2:1 and 1:1) and two cooling protocols were simulated (Fast: ∼300 °C/min, Slow: ∼30 °C/min) using the heat transfer module, followed by stress analysis in ABAQUS. The physical properties of zirconia, lithium disilicate, and the porcelains used for the simulations were determined as a function of temperature. RESULTS PVLD showed lower residual stresses than PVZ. The maximum tensile stresses in PVZ were observed in the cusp area, whereas those in PVLD were located in the central fossa. The 1:1 thickness ratio decreased stresses in both layers of PVZ. Slow cooling slightly decreased residual stresses in both systems. However, the cooling rate effect was more evident in transient stresses. SIGNIFICANCE Slow cooling is preferable for both systems. A thinner porcelain layer over zirconia lowers stresses throughout the restoration. The different stress distributions between PVZ and PVLD may affect their failure modes. Smaller mismatches in modulus, CTE, and specific heat between the constituents, and the use of low Tg porcelains can effectively reduce the deleterious transient and residual tensile stresses in bilayer restorations.
Collapse
Affiliation(s)
- Camila S Rodrigues
- Department of Dental Materials and Prosthodontics, Institute of Science and Technology, São Paulo State University, 777 Eng. Francisco José Longo Av, 12245-000, São José dos Campos, SP, Brazil
| | - Sukirti Dhital
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd., U-3037, Storrs, CT 06269, USA
| | - Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd., U-3037, Storrs, CT 06269, USA
| | - Liliana Gressler May
- Department of Restorative Dentistry, School of Dentistry, Federal University of Santa Maria, 1000 Roraima Av., T Street, Building 26F, 97105-900, Santa Maria, RS, Brazil
| | - Mark S Wolff
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th Street, Philadelphia, PA 19104, USA
| | - Yu Zhang
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th Street, Philadelphia, PA 19104, USA.
| |
Collapse
|
10
|
Oliveira AR, Jodha KS, Marocho SS, Galhano GA. Characterization of Reinforced and Unreinforced Glass-Ceramic Veneers. Oper Dent 2021; 46:339-347. [PMID: 34251455 DOI: 10.2341/20-067-l] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2020] [Indexed: 11/23/2022]
Abstract
This study aimed to characterize the surface topography, effect of polishing on surface roughness, residual stresses, and hardness in two glass-ceramic veneers. Fifty-two (52) upper incisors were collected, prepared, and scanned for ceramic veneers. Half of the teeth were restored with veneers made up of feldspathic ceramic (FE), and the other half with zirconia-reinforced lithium silicate ceramic (SZ). All the veneers were designed and milled using a CAD/CAM system and later cemented following the manufacturer's guideline. An optical microscope analyzed the topography of the specimens before and after polishing. The surface roughness was measured using the roughness meter (n=12) and the topographical analysis was carried out using an atomic force microscope (n=6). The residual stresses and Vickers' hardness were evaluated by the indentation method in a micro-hardness indenter (n=6). The surface roughness was analyzed using a three-way analysis of variance (ANOVA) followed by a post hoc Tukey test. The Student t-test was used to compare the residual stresses and hardness between the two ceramics. The topographical analysis revealed that both glass-ceramic veneers had similar percentages of specimens with cracks, before (34.6%) and after (42.3%) polishing. The surface roughness decreased after polishing (p<0.001), and the polishing smoothed out the surface of the veneers. The zirconia-reinforced lithium silicate veneer had a lower roughness as compared to the feldspathic one after polishing, while the residual stresses (p=0.722) and hardness (p=0.782) were statistically similar for both ceramic veneers.
Collapse
|
11
|
Meirelles PD, da Rocha LS, Pecho OE, Della Bona A, Benetti P. Intraoral repair of a chipped porcelain-zirconia restoration. J ESTHET RESTOR DENT 2020; 32:444-450. [PMID: 32442351 DOI: 10.1111/jerd.12592] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 04/09/2020] [Accepted: 04/20/2020] [Indexed: 01/18/2023]
Abstract
OBJECTIVE Ceramic fracture is an undesirable outcome of the rehabilitation with fixed partial dentures (FPD), mainly because it may involve additional cost and clinical time for intraoral repair or replacement of the restoration. This clinical report describes a 5 years survival intraoral repair of a chipped porcelain veneered zirconia framework restoration using a resin-based composite. CLINICAL CONSIDERATIONS A FPD of porcelain veneered zirconia was made. After 18 months, the FPD presented a porcelain chip (porcelain fracture without exposure to the zirconia structure) on the buccal side of the pontic. An epoxy resin replica of the fractured surface was obtained and was examined under scanning electron microscopy. Fracture origin was found at the cervical area of the pontic. Intraoral repair by bonding the chipped fragment back in place was performed. After 15 days, the porcelain fragment debonded without patient knowledge and the fragment was lost. Then, intraoral repair using composite resin to restore the fractured area was performed and is still in function to date. CONCLUSIONS Based on the 5-years survival of the performed intraoral repair, the composite resin reconstruction technique has shown to be an adequate alternative treatment for fractured FPD. CLINICAL SIGNIFICANCE A resin composite repair of the fracture site can be performed in one clinical session, using much less time and cost than for the replacement of FPD. This clinical case survived 5 years to date.
Collapse
Affiliation(s)
- Potira Dalques Meirelles
- Post-Graduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil
| | - Larissa Simião da Rocha
- Post-Graduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil
| | - Oscar E Pecho
- Post-Graduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil
| | - Alvaro Della Bona
- Post-Graduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil
| | - Paula Benetti
- Post-Graduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil
| |
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
Effect of cooling protocol on mechanical properties and microstructure of dental veneering ceramics. Dent Mater 2019; 35:1498-1505. [DOI: 10.1016/j.dental.2019.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/28/2019] [Accepted: 07/15/2019] [Indexed: 02/04/2023]
|
14
|
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.
Collapse
|
15
|
Bergamo ET, Bordin D, Ramalho IS, Lopes AC, Gomes RS, Kaizer M, Witek L, Bonfante EA, Coelho PG, Del Bel Cury AA. Zirconia-reinforced lithium silicate crowns: Effect of thickness on survival and failure mode. Dent Mater 2019; 35:1007-1016. [DOI: 10.1016/j.dental.2019.04.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 02/12/2019] [Accepted: 04/12/2019] [Indexed: 10/26/2022]
|
16
|
Wendler M, Belli R, Lohbauer U. Factors influencing development of residual stresses during crystallization firing in a novel lithium silicate glass-ceramic. Dent Mater 2019; 35:871-882. [DOI: 10.1016/j.dental.2019.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 03/04/2019] [Accepted: 03/06/2019] [Indexed: 12/12/2022]
|
17
|
Jikihara AN, Tanaka CB, Ballester RY, Swain MV, Versluis A, Meira JBC. Why a zero CTE mismatch may be better for veneered Y-TZP structures. J Mech Behav Biomed Mater 2019; 96:261-268. [PMID: 31075747 DOI: 10.1016/j.jmbbm.2019.04.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/25/2019] [Accepted: 04/26/2019] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Compare residual stress distribution of bilayered structures with a mismatch between the coefficient of thermal expansion (CTE) of framework and veneering ceramic. A positive mismatch, which is recommended for metal-ceramic dental crowns, was hypothesized to contribute to a greater chipping frequency in veneered Y-TZP structures. In addition, the multidirectional nature of residual stresses in bars and crowns is presented to explore some apparent contradictions among different studies. METHODS Planar bar and crown-shaped bilayered specimens with 0.7 mm framework thickness and 1.5 mm porcelain veneer thickness were investigated using finite element elastic analysis. Eight CTE mismatch conditions were simulated, representing two framework materials (zirconia and metal) and six veneering porcelains (distinguished by CTE values). Besides metal-ceramic and zirconia-ceramic combinations indicated by the manufacturer, models presenting similar mismatch values (1 ppm/°C) with different framework materials (metal or zirconia) and zirconia-based models with metal-compatible porcelain veneers were also tested. A slow cooling protocol from 600 °C to room temperature was simulated. The distributions of residual maximum and minimum principal stresses, as well as stress components parallel to the long axis of the specimens, were analysed. RESULTS Planar and crown specimens generated different residual stress distributions. When manufacturer recommended combinations were analysed, residual stresses obtained for zirconia models were significantly higher than those for metal-based models. When zirconia frameworks were combined with metal-compatible porcelains, the residual stress values were even higher. Residual stresses were not different between metal-based and zirconia-based models if the CTE mismatch was similar. SIGNIFICANCE Some conclusions obtained with planar specimens cannot be extrapolated to clinical situations because specimen shape strongly influences residual stress patterns. Since positive mismatch generates compressive hoop stresses and tensile radial stresses and since zirconia-based crowns tend to be more vulnerable to chipping, a tensile stress-free state generated with a zero CTE mismatch could be advantageous.
Collapse
Affiliation(s)
- Alice N Jikihara
- Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil
| | - Carina B Tanaka
- School of Mechanical and Manufacturing Engineering, UNSW, Sydney, NSW, Australia
| | - Rafael Y Ballester
- Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil
| | - Michael V Swain
- Bioengineering, AMME, Faculty of Engineering, University of Sydney, Sydney, NSW, Australia
| | - Antheunis Versluis
- Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Josete B C Meira
- Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
| |
Collapse
|
18
|
Do thermal treatments affect the mechanical behavior of porcelain-veneered zirconia? A systematic review and meta-analysis. Dent Mater 2019; 35:807-817. [PMID: 30846374 DOI: 10.1016/j.dental.2019.02.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Accepted: 02/13/2019] [Indexed: 11/21/2022]
Abstract
OBJECTIVES A systematic review of in vitro studies was conducted to assess the effect of thermal treatments on flexural strength or critical load to failure of porcelain-veneered zirconia (PVZ). SOURCES Literature searches were performed up to June 2018 in PubMed/MEDLINE, Scopus and Web of Science databases, with no publication year or language limits. DATA From 393 relevant studies, 21 were selected for full-text analysis, from which 7 failed to meet the inclusion criteria. The 14 remaining papers were included in the systematic review: 8 for meta-analysis and 6 restricted to descriptive analyses. Hand searching of reference lists resulted in no additional papers. STUDY SELECTION In vitro studies using PVZ specimens testing the influence of thermal treatments on the fracture resistance to monotonic or cyclic loading. Papers evaluating cooling rate were divided into those applying fast cooling from above the porcelain glass transition temperature (Tg), or from below it. Meta-analyses were performed separately for flexural strength and critical load to failure, using random effects at a 5% significance level. CONCLUSIONS Delaying furnace opening at a temperature below the porcelain Tg is advised for PVZ restorations, in order to improve their fracture resistance. Additional information is required to confirm the apparent beneficial effect of self-glaze and repeated veneer firings on the mechanical properties of these restorations. Finally, in order to obtain conclusive and relevant evidence regarding thermal treatments and the fracture resistance of PVZs, future studies should concentrate on anatomically-correct crown specimens.
Collapse
|
19
|
Thermal induced deflection of a porcelain-zirconia bilayer: Influence of cooling rate. Dent Mater 2019; 35:574-584. [PMID: 30738621 DOI: 10.1016/j.dental.2019.01.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 01/05/2019] [Accepted: 01/18/2019] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the thermal expansion of a porcelain (VM9) and tetragonal zirconia (Y-TZP) as well as the deflection upon re-heating and cooling of a bilayer fabricated from these two materials after slow and rapid cooling during initial fabrication. METHODS The coefficient of thermal expansion (CTE) of bulk porcelain and Y-TZP as well as bilayer beam deflection was measured with a novel non-contact optical dilatometer. The influence of cooling rate during initial fabrication of the porcelain-zirconia bilayer and the bulk porcelain during subsequent heating and cooling is investigated. Specimens were heated to 900°C in the dilatometer, well in excess of the glass transition temperature (Tg) and softening temperature (Ts) of the porcelain. RESULTS The thermal expansion of the porcelain above Tg exhibits a threefold increase in CTE over that observed below Tg. Observations of the bilayer deflection reflect the difference in the CTE of the component materials and enable Tg and Ts temperatures for the porcelain to be estimated. Initial cooling rate of the porcelain and porcelain-YTZP bilayer was found to have a profound influence on the subsequent response to slow reheating and cooling as well as the resultant residual deflection. SIGNIFICANCE The estimation of the residual stress and potential for chipping of porcelain-zirconia dental restorative systems should not be based solely on thermal expansion data measured below Tg.
Collapse
|
20
|
Lunt AJG, Chater P, Kleppe A, Baimpas N, Neo TK, Korsunsky AM. Residual strain mapping through pair distribution function analysis of the porcelain veneer within a yttria partially stabilised zirconia dental prosthesis. Dent Mater 2018; 35:257-269. [PMID: 30502963 DOI: 10.1016/j.dental.2018.11.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 10/31/2018] [Accepted: 11/14/2018] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Residually strained porcelain is influential in the early onset of failure in Yttria Partially Stabilised Zirconia (YPSZ) - porcelain dental prosthesis. In order to improve current understanding it is necessary to increase the spatial resolution of residual strain analysis in these veneers. METHODS Few techniques exist which can resolve residual stress in amorphous materials at the microscale resolution required. For this reason, recent developments in Pair Distribution Function (PDF) analysis of X-ray diffraction data of dental porcelain have been exploited. This approach has facilitated high-resolution (70μm) quantification of residual strain in a YPSZ-porcelain dental prosthesis. In order to cross-validate this technique, the sequential ring-core focused ion beam and digital image correlation approach was implemented at a step size of 50μm. This semi-destructive technique exploits microscale strain relief to provide quantitative estimates of the near-surface residual strain. RESULTS The two techniques were found to show highly comparable results. The residual strain within the veneer was found to be primarily tensile, with the highest magnitude stresses located at the YPSZ-porcelain interface where failure is known to originate. Oscillatory tensile and compressive stresses were also found in a direction parallel to the interface, likely to be induced by the multiple layering used during fabrication. SIGNIFICANCE This study provides the insights required to improve prosthesis modelling, to develop new processing routes that minimise residual stress and ultimately to reduce prosthesis failure rates. The PDF approach also offers a powerful new technique for microscale strain quantification in amorphous materials.
Collapse
Affiliation(s)
- Alexander J G Lunt
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom.
| | - Philip Chater
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom
| | - Annette Kleppe
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom
| | - Nikolaos Baimpas
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom
| | - Tee K Neo
- Specialist Dental Group, Mount Elizabeth Orchard, #08-03/08-08/08-10, 228510, Singapore
| | - Alexander M Korsunsky
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom
| |
Collapse
|
21
|
Bearing capacity of ceramic crowns before and after cyclic loading: An in vitro study. J Mech Behav Biomed Mater 2018; 87:197-204. [DOI: 10.1016/j.jmbbm.2018.07.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 11/21/2022]
|
22
|
Zhang Y, Lawn BR. Evaluating dental zirconia. Dent Mater 2018; 35:15-23. [PMID: 30172379 DOI: 10.1016/j.dental.2018.08.291] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 08/19/2018] [Accepted: 08/21/2018] [Indexed: 10/28/2022]
Abstract
OBJECTIVES To survey simple contact testing protocols for evaluating the mechanical integrity of zirconia dental ceramics. Specifically, to map vital material property variations and to quantify competing damage modes. METHODS Exploratory contact tests are conducted on layer structures representative of zirconia crowns on dentin. RESULTS Sharp-tip micro- and nano-indentations were used to investigate the roles of weak interfaces and residual stresses in veneered zirconia, and to map property variations in graded structures. Tests with blunt sphere indenters on flat specimens were used to identify and quantify various critical damage modes in simulated occlusal loading in veneered and monolithic zirconia. SIGNIFICANCE Contact testing is a powerful tool for elucidating the fracture and deformation modes that control the lifetimes of zirconia dental ceramics. The advocated tests are simple, and provide a sound physical basis for analyzing damage resistance of anatomically-correct crowns and other complex dental prostheses.
Collapse
Affiliation(s)
- Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
| | - Brian R Lawn
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| |
Collapse
|
23
|
Furtado de Mendonca A, Shahmoradi M, Gouvêa CVDD, De Souza GM, Ellakwa A. Microstructural and Mechanical Characterization of CAD/CAM Materials for Monolithic Dental Restorations. J Prosthodont 2018; 28:e587-e594. [PMID: 30121945 DOI: 10.1111/jopr.12964] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2018] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To determine and compare the microstructure, flexural strength, flexural modulus, fracture strength, and microhardness of four types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials for monolithic dental restorations. MATERIALS AND METHODS A lithium disilicate (LD; IPS e.max CAD), a zirconia-reinforced lithium silicate (ZLS; VITA Suprinity), a hybrid high-performance polymer (HPP) composite resin (GC Cerasmart), and a hybrid polymer-infiltrated ceramic network (PICN) material (VITA Enamic) were used to manufacture monolithic ceramic posterior crowns (n = 10) that were adhesively cemented on resin-based composite dies and loaded until fracture. In addition, 40 rectangular bars (n = 10) were milled and polished for three-point flexural strength testing. Microhardness (Vickers indentation), as well as quantitative (energy dispersive spectroscopy) and qualitative (scanning electron microscopy) structural analysis were conducted on fracture surfaces. Data were analyzed by one-way ANOVA and Tukey HSD post-hoc test (p = 0.05). RESULTS Mechanical testing results showed that the material type has a significant effect on the fracture strength (p < 0.0001) of the monolithic crowns with ZLS and LD presenting significantly higher fracture strength than the PICN and HPP hybrid materials. LD showed the highest flexural strength (p < 0.0001) followed by ZLS, HPP, and PICN, respectively. The lowest flexural modulus and hardness were presented by HPP whereas ZLS had the highest flexural modulus and hardness. The LD presented the highest modulus of resilience and the PICN the lowest. CONCLUSIONS All CAD/CAM crown materials exhibited high values of fracture and flexural resistance, making them suitable materials for posterior full-crown restorations. Glass-ceramics suffered more from catastrophic and nonreparable fracture patterns, whereas minimal chipping and type II fracture patterns were more common in hybrid materials. The combination of more flexibility, less stiffness, and increased softness with satisfactory flexural and fracture strength values observed in PICN and HPP makes these two hybrid materials suitable choices for chairside monolithic crown fabrication.
Collapse
Affiliation(s)
| | - Mahdi Shahmoradi
- Oral Rehabilitation & Dental Biomaterials and Bioengineering, The University of Sydney, Sydney, Australia
| | | | - Grace M De Souza
- Department of Clinical Sciences, University of Toronto, Toronto, Canada
| | - Ayman Ellakwa
- Oral Rehabilitation & Dental Biomaterials and Bioengineering, The University of Sydney, Sydney, Australia
| |
Collapse
|
24
|
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.
Collapse
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
| |
Collapse
|
25
|
Ebadian B, Mosharraf R, Abbasi M. Effect of ceramic cooling protocols and zirconia coloring on fracture load of zirconia-based restorations. Dent Res J (Isfahan) 2018; 15:17-24. [PMID: 29497443 PMCID: PMC5806426 DOI: 10.4103/1735-3327.223612] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Background: Residual thermal stresses in dental porcelains can cause clinical failure. Porcelain cooling protocols may affect the amount of residual stresses within porcelain and also porcelain–zirconia bond strength. The objective of this study was to assess the effect of cooling protocols on the fracture load of porcelain veneered zirconia restorations. Materials and Methods: Forty zirconia bars (31 mm × 6.5 mm × 1.35 mm ± 0.1 mm) were fabricated by computer-aided design and computer-aided manufacturing technology. Half of the specimens were immersed in the coloring agent for 2 min before sintering (yellow group). Thus, the specimens were divided into two groups of white (W) and yellow (Y) samples (n = 20). Heat-pressed ceramic was applied to all bars. After pressing, half of the samples in each group were immediately removed from the oven (fast cooling) while the other specimens remained in the partially open door (30%) oven until the temperature reached to 500°C. Samples were thermocycled for 5000 cycles and subjected to modified four-point flexural strength test by a universal testing machine at a crosshead speed of 0.5 mm/min. Two-way ANOVA, One-way ANOVA followed by post hoc Tukey honest significant difference tests were used for data analysis (α = 0.05). Results: Fractures were cohesive in all samples (within the porcelain adjacent to the interface). Two-way ANOVA showed that the effect of cooling protocol on the fracture load of samples was statistically significant (P < 0.001). In addition, the fracture load of W and Y groups was significantly different (P < 0.001). The white slow group showed the highest fracture load (179.88 ± 23.43 N). Conclusion: Slow cooling protocol should be preferably applied for zirconia restorations. Coloring agent used in this study had a significant negative effect on fracture load.
Collapse
Affiliation(s)
- Behnaz Ebadian
- Department of Prosthodontics, Dental Implant Research Center, School of Dentistry, Isfahan University of Medical Science, Isfahan, Iran
| | - Ramin Mosharraf
- Department of Prosthodontics, Dental Material Research Center, School of Dentistry, Isfahan University of Medical Science, Isfahan, Iran
| | - Mahsa Abbasi
- Department of Prosthodontics, School of Dentistry, Shahrekord University of Medical Science, Shahrekord, Iran
| |
Collapse
|
26
|
Askari E, Flores P, Silva F. A particle swarm-based algorithm for optimization of multi-layered and graded dental ceramics. J Mech Behav Biomed Mater 2018; 77:461-469. [DOI: 10.1016/j.jmbbm.2017.10.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 09/27/2017] [Accepted: 10/02/2017] [Indexed: 10/18/2022]
|
27
|
Fardin VP, Bonfante EA, Coelho PG, Janal MN, Tovar N, Witek L, Bordin D, Bonfante G. Residual stress of porcelain-fused to zirconia 3-unit fixed dental prostheses measured by nanoindentation. Dent Mater 2017; 34:260-271. [PMID: 29258696 DOI: 10.1016/j.dental.2017.11.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 08/12/2017] [Accepted: 11/09/2017] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To evaluate the residual stress (nanoindentation based on hardness) of fatigued porcelain-fused to zirconia 3-unit fixed dental prostheses (FDP) with different framework designs. METHODS Twenty maxillary 3-unit FDP replacing second-premolar (pontic) were fabricated with conventional framework-design (even-thickness of 0.5mm and 9mm2 connector area) and modified framework-design (thickness of 0.5mm presenting lingual collar connected to proximal struts and 12mm2 connector area). Connector marginal ridges were loaded and the fractured and suspended FDPs were divided (n=3/each) into: (1) Fractured zirconia even-thickness (ZrEvenF); (2) Suspended zirconia even-thickness (ZrEvenS); (3) Fractured zirconia with modified framework (ZrModF); (4) Suspended zirconia with modified framework (ZrModS); (5) Non-fatigued FDP with conventional framework design (Control). The FDPs were nanoindented at 0.03mm (Region of Interest (ROI) 1), 0.35mm (ROI 2) and 1.05mm (ROI 3) distances from porcelain veneer outer surface with peak load 4000μN. The Linear Mixed Analysis of Variance (ANOVA) Model on ranks and Least Significant Difference Test on ranks (95%) were used. RESULTS Highest rank hardness values were found for Control group and ZrModS, whereas the lowest values were found in ZrModF. Statistical differences (p=0.000) were found among all groups except for comparison between ZrModS and Control group (p=0.371). Hardness between ROIs were statistically significant different (p<0.001) where ROI 1 presented the lowest values. SIGNIFICANCE Framework-design modification did not influence the residual stress of porcelain-fused to zirconia fatigued 3-unit FDP. Whereas fractured FDPs showed the highest residual stress compared to suspended and control FDPs. Residual stress increased as nanoindented away from framework.
Collapse
Affiliation(s)
- Vinicius P Fardin
- Department of Prosthodontics, University of Vila Velha, Vila Velha, ES, Brazil; Department of Prosthodontics and Periodontology, University of São Paulo - Bauru School of Dentistry, Bauru, SP, Brazil.
| | - Estevam A Bonfante
- Department of Prosthodontics and Periodontology, University of São Paulo - Bauru School of Dentistry, Bauru, SP, Brazil
| | - Paulo G Coelho
- Department of Biomaterials and Biomimetics, New York University, New York, NY, USA; Hansjörg Wyss Department of Plastic Surgery, NYU Langone Medical Center, New York, NY, USA
| | - Malvin N Janal
- Department of Epidemiology and Health Promotion, New York University College of Dentistry, New York, NY, USA
| | - Nick Tovar
- Department of Biomaterials and Biomimetics, New York University, New York, NY, USA
| | - Lukasz Witek
- Department of Biomaterials and Biomimetics, New York University, New York, NY, USA
| | - Dimorvan Bordin
- Department of Operative Dentistry, Guarulhos University, Guarulhos, SP, Brazil
| | - Gerson Bonfante
- Department of Prosthodontics and Periodontology, University of São Paulo - Bauru School of Dentistry, Bauru, SP, Brazil
| |
Collapse
|
28
|
de Mello CC, Bitencourt SB, dos Santos DM, Pesqueira AA, Pellizzer EP, Goiato MC. The Effect of Surface Treatment on Shear Bond Strength between Y-TZP and Veneer Ceramic: A Systematic Review and Meta-Analysis. J Prosthodont 2017; 27:624-635. [DOI: 10.1111/jopr.12727] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2017] [Indexed: 11/27/2022] Open
Affiliation(s)
- Caroline Cantieri de Mello
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| | - Sandro Basso Bitencourt
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| | - Daniela Micheline dos Santos
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| | - Aldiéris Alves Pesqueira
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| | - Eduardo Piza Pellizzer
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| | - Marcelo Coelho Goiato
- Department of Dental Materials and Prosthodontics, Aracatuba Dental School; UNESP - Univ Estadual Paulista; Campus of Aracatuba Sao Paulo Brazil
| |
Collapse
|
29
|
Using glass-graded zirconia to increase delamination growth resistance in porcelain/zirconia dental structures. Dent Mater 2017; 34:e8-e14. [PMID: 29183670 DOI: 10.1016/j.dental.2017.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/04/2017] [Accepted: 11/08/2017] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their tendency to delaminate along the P/Z interface remains a practical problem so that assessing and improving the interfacial strength are important design aspects. This work examines the effect of modifying the zirconia veneering surface with an in-house felspathic glass on the interfacial fracture resistance of fused P/Z. METHODS Three material systems are studied: porcelain fused to zirconia (control) and porcelain fused to glass-graded zirconia with and without the presence of a glass interlayer. The specimens were loaded in a four-point-bend fixture with the porcelain veneer in tension. The evolution of damage is followed with the aid of a video camera. The interfacial fracture energy GC was determined with the aid of a FEA, taking into account the stress shielding effects due to the presence of adjacent channel cracks. RESULTS Similarly to a previous study on PFZ specimens, the fracture sequence consisted of unstable growth of channel cracks in the veneer followed by stable cracking along the P/Z interface. However, the value of GC for the graded zirconia was approximately 3 times that of the control zirconia, which is due to the good adhesion between porcelain and the glass network structure on the zirconia surface. SIGNIFICANCE Combined with its improved bonding to resin-based cements, increased resistance to surface damage and good esthetic quality, graded zirconia emerges as a viable material concept for dental restorations.
Collapse
|
30
|
Figueiredo VMGD, Pereira SMB, Bressiani E, Valera MC, Bottino MA, Zhang Y, Melo RMD. Effects of porcelain thickness on the flexural strength and crack propagation in a bilayered zirconia system. J Appl Oral Sci 2017; 25:566-574. [PMID: 29069155 PMCID: PMC5806690 DOI: 10.1590/1678-7757-2015-0479] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 03/10/2017] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). MATERIAL AND METHODS Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. RESULTS The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor "thickness of the porcelain" was statistically significant (p=0.001) and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. CONCLUSION The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.
Collapse
Affiliation(s)
- Viviane Maria Gonçalves de Figueiredo
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Materiais Odontológicos e Prótese, São Jose dos Campos, SP, Brasil
| | - Sarina Maciel Braga Pereira
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Materiais Odontológicos e Prótese, São Jose dos Campos, SP, Brasil
| | - Eduardo Bressiani
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Odontologia Restauradora, São Jose dos Campos, SP, Brasil
| | - Márcia Carneiro Valera
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Odontologia Restauradora, São Jose dos Campos, SP, Brasil
| | - Marco Antônio Bottino
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Materiais Odontológicos e Prótese, São Jose dos Campos, SP, Brasil
| | - Yu Zhang
- New York University, College of Dentistry, Biomaterials and Biomimetics, New York, USA
| | - Renata Marques de Melo
- Univ. Estadual Paulista, Instituto de Ciência e Tecnologia de São José dos Campos, Departamento de Materiais Odontológicos e Prótese, São Jose dos Campos, SP, Brasil
| |
Collapse
|
31
|
Abstract
A survey of the development of dental ceramics is presented to provide a better understanding of the rationale behind the development and clinical indications of each class of ceramic material. Knowledge of the composition, microstructure, and properties of a material is critical for selecting the right material for specific applications. The key to successful ceramic restorations rests on material selection, manufacturing technique, and restoration design, including the balancing of several factors such as residual stresses, tooth contact conditions, tooth size and shape, elastic modulus of the adhesives and tooth structure, and surface state.
Collapse
Affiliation(s)
- Yu Zhang
- Department of Biomaterials and Biomimetics, NYU College of Dentistry, 433 First Avenue, Room 810, New York, NY 10010, USA.
| | - J Robert Kelly
- Department of Biomedical Engineering, University of Connecticut Health Center, Mailstop 1615, 263 Farmington Avenue, Farmington, CT 06030-1615, USA
| |
Collapse
|
32
|
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]
|
33
|
Investigation on Indentation Cracking-Based Approaches for Residual Stress Evaluation. MATERIALS 2017; 10:ma10040404. [PMID: 28772765 PMCID: PMC5506943 DOI: 10.3390/ma10040404] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 04/05/2017] [Accepted: 04/06/2017] [Indexed: 11/17/2022]
Abstract
Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS. A generalized analytical model that accounts for the crack shape and its change is presented. To assess these analytical models and to gain detailed insight into the crack evolution, an extended finite element (XFE) model is established. XFE analysis results show that the crack shape is generally not semi-circular and affected by RS and that tensile and compressive RS have different effects on the crack evolution. Parameter studies are performed to calibrate the generalized analytical model. Comparison of the results calculated by the analytical models with XFE results reveals the inaccuracy inherent in the previous analytical models, namely the neglect of (the change of) the crack aspect-ratio, in particular for tensile RS. Previous models should therefore be treated with caution and, if at all, used only for compressive RS. The generalized model, on the other hand, gives a more accurate description of the RS, but requires the crack depth.
Collapse
|
34
|
Fabris D, Souza JC, Silva FS, Fredel M, Mesquita-Guimarães J, Zhang Y, Henriques B. THERMAL RESIDUAL STRESSES IN BILAYERED, TRILAYERED AND GRADED DENTAL CERAMICS. CERAMICS INTERNATIONAL 2017; 43:3670-3678. [PMID: 28163345 PMCID: PMC5289668 DOI: 10.1016/j.ceramint.2016.11.209] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Layered ceramic systems are usually hit by residual thermal stresses created during cooling from high processing temperature. The purpose of this study was to determine the thermal residual stresses at different ceramic multi-layered systems and evaluate their influence on the bending stress distribution. Finite elements method was used to evaluate the residual stresses in zirconia-porcelain and alumina-porcelain multi-layered discs and to simulate the 'piston-on-ring' test. Temperature-dependent material properties were used. Three different multi-layered designs were simulated: a conventional bilayered design; a trilayered design, with an intermediate composite layer with constant composition; and a graded design, with an intermediate layer with gradation of properties. Parameters such as the interlayer thickness and composition profiles were varied in the study. Alumina-porcelain discs present smaller residual stress than the zirconia-porcelain discs, regardless of the type of design. The homogeneous interlayer can yield a reduction of ~40% in thermal stress relative to bilayered systems. Thinner interlayers favoured the formation of lower thermal stresses. The graded discs showed the lowest thermal stresses for a gradation profile given by power law function with p=2. The bending stresses were significantly affected by the thermal stresses in the discs. The risk of failure for all-ceramic dental restorative systems can be significantly reduced by using trilayered systems (homogenous or graded interlayer) with the proper design.
Collapse
Affiliation(s)
- Douglas Fabris
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Júlio C.M. Souza
- CMEMS-UMinho, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal
- School of Dentistry (DODT), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900, Florianópolis/SC, Brazil
| | - Filipe S. Silva
- CMEMS-UMinho, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal
| | - Márcio Fredel
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Joana Mesquita-Guimarães
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York University, New York, USA
| | - Bruno Henriques
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
- School of Dentistry (DODT), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900, Florianópolis/SC, Brazil
| |
Collapse
|
35
|
Aurélio IL, Dorneles LS, May LG. Extended glaze firing on ceramics for hard machining: Crack healing, residual stresses, optical and microstructural aspects. Dent Mater 2017; 33:226-240. [DOI: 10.1016/j.dental.2016.12.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/07/2016] [Accepted: 12/08/2016] [Indexed: 11/29/2022]
|
36
|
Nakonieczny DS, Ziębowicz A, Paszenda ZK, Krawczyk C. Trends and perspectives in modification of zirconium oxide for a dental prosthetic applications – A review. Biocybern Biomed Eng 2017. [DOI: 10.1016/j.bbe.2016.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
37
|
Influence of interlayer design on residual thermal stresses in trilayered and graded all-ceramic restorations. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2016; 71:1037-1045. [PMID: 27987657 DOI: 10.1016/j.msec.2016.11.087] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 10/24/2016] [Accepted: 11/23/2016] [Indexed: 11/21/2022]
Abstract
Residual thermal stresses are formed in dental restorations during cooling from high temperature processing. The aim of this study was to evaluate the influence of constructive design variables (composition and interlayer thickness) on residual stresses in alumina- and zirconia-graded restorations. Restorations' real-like cooling conditions were simulated using finite elements method and temperature-dependent material properties were used. Three different designs were evaluated: a bilayered restoration (sharp transition between materials); a trilayered restoration with a homogenous interlayer between core and veneer; and a trilayered restoration with a graded interlayer. The interlayer thickness and composition were varied. Zirconia restorations presented overall higher thermal stress values than alumina ones. Thermal stresses were significantly reduced by the presence of a homogeneous interlayer. The composition of the interlayer showed great influence on the thermal stresses, with the best results for homogeneous interlayers being observed for porcelain contents in the composite ranging between 30%-50% (vol.%), for both alumina and zirconia restorations. The interlayer's thickness showed a minor contribution in the thermal stress reduction. The graded interlayer showed an optimized reduction in restorations' thermal stresses. The use of graded interlayer, favoring enhanced thermal stress distributions and lower magnitude is expected to reduce the risk of catastrophic failure.
Collapse
|
38
|
Meirelles PD, Spigolon YO, Borba M, Benetti P. Leucite and cooling rate effect on porcelain-zirconia mechanical behavior. Dent Mater 2016; 32:e382-e388. [PMID: 27707502 DOI: 10.1016/j.dental.2016.09.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 05/12/2016] [Accepted: 09/03/2016] [Indexed: 10/20/2022]
Abstract
OBJECTIVE This study investigated the influence of the cooling protocol on the mechanical behavior of Y-TZP veneered with porcelain with different compositions. The tested hypotheses were: (1) Y-TZP infrastructures veneered with porcelain containing leucite in its composition presents higher flexural strength (σ) and reliability (m), and (2) slow cooling protocol results in greater σ and m. METHODS A total of 120 bilayer porcelain-Y-TZP bar-shaped specimens were prepared with the dimensions of 1.8mm (0.8mm Y-TZP±1.0mm porcelain)×4.0mm×16.0mm. Specimens were divided into four groups (n=30) according to the porcelain composition (containing or not leucite) and cooling protocol. Fast cooling was performed by opening the furnace chamber at sintering temperature. For the slow cooling, the chamber was maintained closed until it reached the room temperature. Specimens were tested in three-point bending with the porcelain surface under tension using a universal testing machine, in 37°C water, at 0.5mm/min crosshead speed. Data were analyzed by two-way ANOVA, Tukey post-hoc test (α=0.05) and Weibull. RESULTS Y-TZP veneered with porcelains with different microstructural composition presented similar σ and m values (p=0.718). The cooling protocol had no influence on the σ and m values of the experimental groups (p=0.718). Cracking represented 95% of failures, whereas the initial flaw propagated from the porcelain surface towards the interface. SIGNIFICANCE Y-TZP veneered with porcelain containing or not leucite present similar mechanical behavior and, at 1-mm thickness, is not sensitive to the cooling protocol.
Collapse
Affiliation(s)
- P D Meirelles
- University of Passo Fundo, Post-Graduate Program in Dentistry, Passo Fundo, RS, Brazil
| | - Y O Spigolon
- University of Passo Fundo, Post-Graduate Program in Dentistry, Passo Fundo, RS, Brazil
| | - M Borba
- University of Passo Fundo, Post-Graduate Program in Dentistry, Passo Fundo, RS, Brazil
| | - P Benetti
- University of Passo Fundo, Post-Graduate Program in Dentistry, Passo Fundo, RS, Brazil.
| |
Collapse
|
39
|
Wendler M, Belli R, Petschelt A, Lohbauer U. Spatial distribution of residual stresses in glass-ZrO 2 sphero-cylindrical bilayers. J Mech Behav Biomed Mater 2016; 60:535-546. [DOI: 10.1016/j.jmbbm.2016.03.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 11/28/2022]
|
40
|
Fabris D, Souza JC, Silva FS, Fredel M, Mesquita-Guimarães J, Zhang Y, Henriques B. The bending stress distribution in bilayered and graded zirconia-based dental ceramics. CERAMICS INTERNATIONAL 2016; 42:11025-11031. [PMID: 28104926 PMCID: PMC5241077 DOI: 10.1016/j.ceramint.2016.03.245] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The purpose of this study was to evaluate the biaxial flexural stresses in classic bilayered and in graded zirconia-feldspathic porcelain composites. A finite element method and an analytical model were used to simulate the piston-on-ring test and to predict the biaxial stress distributions across the thickness of the bilayer and graded zirconia-feldspathic porcelain discs. An axisymmetric model and a flexure formula of Hsueh et al. were used in the FEM and analytical analysis, respectively. Four porcelain thicknesses were tested in the bilayered discs. In graded discs, continuous and stepwise transitions from the bottom zirconia layer to the top porcelain layer were studied. The resulting stresses across the thickness, measured along the central axis of the disc, for the bilayered and graded discs were compared. In bilayered discs, the maximum tensile stress decreased while the stress mismatch (at the interface) increased with the porcelain layer thickness. The optimized balance between both variables is achieved for a porcelain thickness ratio in the range of 0.30-0.35. In graded discs, the highest tensile stresses were registered for porcelain rich interlayers (p=0.25) whereas the zirconia rich ones (p=8) yield the lowest tensile stresses. In addition, the maximum stresses in a graded structure can be tailored by altering compositional gradients. A decrease in maximum stresses with increasing values of p (a scaling exponent in the power law function) was observed. Our findings showed a good agreement between the analytical and simulated models, particularly in the tensile region of the disc. Graded zirconia-feldspathic porcelain composites exhibited a more favourable stress distribution relative to conventional bilayered systems. This fact can significantly impact the clinical performance of zirconia-feldspathic porcelain prostheses, namely reducing the fracture incidence of zirconia and the chipping and delamination of porcelain.
Collapse
Affiliation(s)
- Douglas Fabris
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Júlio C.M. Souza
- CMEMS-UMinho, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal
- School of Dentistry (DODT), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900, Florianópolis/SC, Brazil
| | - Filipe S. Silva
- CMEMS-UMinho, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal
| | - Márcio Fredel
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Joana Mesquita-Guimarães
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York University, New York, USA
| | - Bruno Henriques
- Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil
- School of Dentistry (DODT), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900, Florianópolis/SC, Brazil
| |
Collapse
|
41
|
Tanaka CB, Harisha H, Baldassarri M, Wolff MS, Tong H, Meira JB, Zhang Y. Experimental and finite element study of residual thermal stresses in veneered Y-TZP structures. CERAMICS INTERNATIONAL 2016; 42:9214-9221. [PMID: 27087734 PMCID: PMC4831075 DOI: 10.1016/j.ceramint.2016.03.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The main complications of zirconia-based laminated systems are chipping and delamination of veneering porcelain, which has been found to be directly associated with the development of residual thermal stresses in the porcelain layer. This study investigates the effects of cooling rate and specimen geometry on the residual stress states in porcelain-veneered zirconia structures. Bilayers of three different shapes (bars, semi-cylindrical shells, and arch-cubic structures) with 1.5 mm and 0.7 mm thickness of dentin porcelain and zirconia framework, respectively, were subjected to two cooling protocols: slow cooling (SC) at 32 °C/min and extremely-slow cooling (XSC) at 2 °C/min. The residual thermal stresses were determined using the Vickers indentation method and validated by finite element analysis. The residual stress profiles were similar among geometries in the same cooling protocol. XSC groups presented significantly higher tensile stresses (p = 0.000), especially for curved interfaces. XSC is a time-consuming process that showed no beneficial effect regarding residual stresses compared to the manufacturer recommended slow cooling rate.
Collapse
Affiliation(s)
- Carina B. Tanaka
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA
- Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil
| | - Hossam Harisha
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA
| | - Marta Baldassarri
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA
| | - Mark S. Wolff
- Department of Cariology and Comprehensive Care, Associate Dean for Pre-doctoral Clinical Education, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA
| | - Hui Tong
- School of Metallurgy and Environment, Central South University, Changsha, Hunan 410083, PR China
| | - Josete B.C. Meira
- Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA
| |
Collapse
|
42
|
Tripathi A, Bagchi S, Singh J, Gaurav V, Pal Singh Negi M. Effect of Different Firing Temperatures on Structural Changes in Porcelain. J Prosthodont 2016; 27:290-298. [PMID: 27123849 DOI: 10.1111/jopr.12484] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2016] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To study the structural changes occurring in the dental porcelain mass fired at various firing temperatures using scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectroscopy. Also, additional tests, namely compressive strength, abrasion resistance analysis, and the amount of oxides released, were conducted at different firing temperatures. MATERIALS AND METHODS Six groups (40 specimens in each group) of porcelain mass were prepared. The dimensions and weight of all the specimens were kept constant. The specimens were then heat treated at different firing temperatures (660°C, 760°C, 860°C, 900°C, 960°C, 990°C). Half of the specimens of each group were subjected to a compressive strength test on a universal testing machine and then finely ground using an electrochemical grinder to prepare for XRD analysis. The other half of the specimens was weighed to analyze the amount of oxides released after each firing cycle. Following this, the specimens underwent an abrasion resistance test on a Nanovea Tribometer. The unaltered surface was scanned using SEM. The data (numerical and graphical) for all the tests were recorded and analyzed using one-way ANOVA and post hoc Tukey test. RESULTS The specimens fired at 900°C exhibited superior compressive strength and abrasion resistance. The quantity of oxides released by the specimens fired at 900°C was the least compared to specimens heat treated at the other firing temperatures. XRD analysis proved that the oxide released by the porcelain mass was calcium aluminum chromium oxide. Also, the fewer peaks obtained in the XRD graphs of specimens fired at 900°C signified lesser porosities in the porcelain specimens. SEM analysis depicted a homogeneous mass of porcelain at 900°C. CONCLUSION All the above findings validate the objective of studying the physical and internal structural changes of dental porcelain when subjected to an increasing firing temperature gradient. The specimens fired at 900°C exhibited superior strength and abrasion resistance. SEM analysis depicted a homogeneous mass of dental porcelain, implying that firing was complete at 900°C.
Collapse
Affiliation(s)
- Arvind Tripathi
- Dean, Postgraduate Studies and Research, Saraswati Dental College and Hospital, Lucknow, India
| | - Soumyojeet Bagchi
- Department of Prosthodontics, Saraswati Dental College and Hospital, Lucknow, India
| | - Juhi Singh
- Department of Prosthodontics, Saraswati Dental College and Hospital, Lucknow, India
| | - Vivek Gaurav
- Indian Institute of Technology, Saharanpur Campus, Roorkee, India
| | | |
Collapse
|
43
|
Sinavarat P, Anunmana C, Muanjit T. Simplified method for determining fracture toughness of two dental ceramics. Dent Mater J 2016; 35:76-81. [PMID: 26830826 DOI: 10.4012/dmj.2015-147] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This study compared the fracture toughness values (KIC), which were derived from simplified techniques: the indentation fracture (IF), the indentation strength (IS), and fractographic approach to that from a standard testing using surface cracks in flexure (SCF). Forty bar specimens, twenty IPS Empress(®) Esthetic and twenty IPS e.max(®)Ceram were prepared. Ten specimens in each material were tested by IF technique, IS technique and fractographic approach, and additional 10 specimens were tested by the SCF technique. This study showed that the mean KIC derived from fractographic approach were not significantly different from that of the SCF in both materials (p>0.05) whereas the mean KIC from indentation techniques rarely agreed with those of the standard technique. The KIC determination is sensitive to the methods used that affect accuracy. Consequently, test selection should be based on a sound understanding and inherent limitations of each technique.
Collapse
|
44
|
Chantranikul N, Salimee P. Biaxial flexural strength of bilayered zirconia using various veneering ceramics. J Adv Prosthodont 2015; 7:358-67. [PMID: 26576251 PMCID: PMC4644776 DOI: 10.4047/jap.2015.7.5.358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 08/03/2015] [Accepted: 09/23/2015] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (α=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. RESULTS It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. CONCLUSION From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength.
Collapse
Affiliation(s)
- Natravee Chantranikul
- Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Prarom Salimee
- Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| |
Collapse
|
45
|
Ramos GF, Monteiro EBC, Bottino M, Zhang Y, de Melo RM. Failure Probability of Three Designs of Zirconia Crowns. INT J PERIODONT REST 2015; 35:843-9. [PMID: 26509988 PMCID: PMC4671273 DOI: 10.11607/prd.2448] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This study used a two-parameter Weibull analysis for evaluation of the lifespan of fully or partially porcelain-/glaze-veneered zirconia crowns after fatigue test. A sample of 60 first molars were selected and prepared for full-coverage crowns with three different designs (n = 20): traditional (crowns with zirconia framework covered with feldspathic porcelain), modified (crowns partially covered with veneering porcelain), and monolithic (full-contour zirconia crowns). All specimens were treated with a glaze layer. Specimens were subjected to mechanical cycling (100 N, 3 Hz) with a piston with a hemispherical tip (Ø = 6 mm) until the specimens failed or up to 2 × 10⁶ cycles. Every 500,000 cycles, the fatigue tests were interrupted and stereomicroscopy (10×) was used to inspect the specimens for damage. The authors performed Weibull analysis of interval data to calculate the number of failures in each interval. The types and numbers of failures according to the groups were: cracking (13 traditional, 6 modified) and chipping (4 traditional) of the feldspathic porcelain, followed by delamination (1 traditional) at the veneer/core interface and debonding (2 monolithic) at the cementation interface. Weibull parameters (β, scale; η, shape), with a two-sided confidence interval of 95%, were: traditional-1.25 and 0.9 × 10⁶ cycles; modified-0.58 and 11.7 × 10⁶ cycles; and monolithic-1.05 and 16.5 × 10⁶ cycles. Traditional crowns showed greater susceptibility to fatigue, the modified group presented higher propensity to early failures, and the monolithic group showed no susceptibility to fatigue. The modified and monolithic groups presented the highest number of crowns with no failures after the fatigue test. The three crown designs presented significantly different behaviors under fatigue. The modified and monolithic groups presented less probability of failure after 2 × 10⁶ cycles.
Collapse
Affiliation(s)
- G. Freitas Ramos
- Institute of Science and Technology, São Paulo State University (UNESP), Sao Jose dos Campos, Brazil
| | | | - M.A. Bottino
- Institute of Science and Technology, São Paulo State University (UNESP), Sao Jose dos Campos, Brazil
| | - Y. Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA
| | - R. Marques de Melo
- Institute of Science and Technology, São Paulo State University (UNESP), Sao Jose dos Campos, Brazil
| |
Collapse
|
46
|
de Lima E, Meira JBC, Özcan M, Cesar PF. Chipping of Veneering Ceramics in Zirconium Dioxide Fixed Dental Prosthesis. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/s40496-015-0066-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
47
|
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]
|
48
|
Pang Z, Chughtai A, Sailer I, Zhang Y. A fractographic study of clinically retrieved zirconia-ceramic and metal-ceramic fixed dental prostheses. Dent Mater 2015; 31:1198-206. [PMID: 26233469 DOI: 10.1016/j.dental.2015.07.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 04/26/2015] [Accepted: 07/08/2015] [Indexed: 11/16/2022]
Abstract
OBJECTIVES A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia-ceramic and metal-ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia-ceramic systems occurred more frequently than those in metal-ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. METHODS Vinyl-polysiloxane impressions of 12 zirconia-ceramic and 6 metal-ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3±2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. RESULTS Among the 12 zirconia-ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal-ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. SIGNIFICANCE Zirconia-ceramic and metal-ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia-ceramic FDPs relative to their metal-ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia-ceramic FDPs.
Collapse
Affiliation(s)
- Zhen Pang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA
| | - Asima Chughtai
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA
| | - Irena Sailer
- Division of Fixed Prosthodontics and Occlusion, School of Dental Medicine, University of Geneva, 19 rue Barthélemy-Menn, CH-1205 Geneva, Switzerland
| | - Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
| |
Collapse
|
49
|
Bankoğlu Güngör M, Yılmaz H, Karakoca Nemli S, Turhan Bal B, Aydın C. Effect of surface treatments on the biaxial flexural strength, phase transformation, and surface roughness of bilayered porcelain/zirconia dental ceramics. J Prosthet Dent 2015; 113:585-95. [DOI: 10.1016/j.prosdent.2014.12.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 11/27/2014] [Accepted: 12/01/2014] [Indexed: 10/23/2022]
|
50
|
Špehar D, Jakovac M. New Knowledge about Zirconium-Ceramic as a Structural Material in Fixed Prosthodontics. Acta Stomatol Croat 2015; 49:137-44. [PMID: 27688396 PMCID: PMC4988823 DOI: 10.15644/asc49/2/7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 05/22/2015] [Indexed: 02/04/2023] Open
Abstract
Dental ceramics represents a major structural material in fixed prosthodontics. Increasing demands for esthetics led to development of new ceramic materials in order to eliminate the use of metal framework and for all ceramic restorations with mechanical properties to withstand high occlusal forces. Out of all the present ceramic materials, zirconium-ceramic has the best mechanical properties, and is the only material that can be used for longer span fixed dental restorations. Despite its excellent mechanical properties, to achieve great esthetics, due to absence of translucency, zirconium-dioxide cannot be used as a single material and needs veneering with more esthetic ceramic. When introduced in dental medicine, it was considered an almost ideal material for fixed prosthodontics, but clinical use and in vivo and in vitro studies showed many problems which still persist despite the improvements.
This review aims to reveal new developments in zirconium-ceramics and technical procedures which could increase clinical performance and longevity of these restorations.
Collapse
Affiliation(s)
| | - Marko Jakovac
- – Department of Prosthodontics, School of Dental Medicine University of Zagreb
| |
Collapse
|