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Nakamura K, Shishido S, Inagaki R, Kanno T, Barkarmo S, Svanborg P, Örtengren U. Critical evaluations on the crystallographic properties of translucent dental zirconia ceramics stabilized with 3-6 mol% yttria. Dent Mater 2024:S0109-5641(24)00181-7. [PMID: 38942711 DOI: 10.1016/j.dental.2024.06.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 06/17/2024] [Accepted: 06/18/2024] [Indexed: 06/30/2024]
Abstract
OBJECTIVES This study aimed to determine the crystalline phase composition of 3-6 mol% yttria-stabilized zirconia (3-6YSZ), specifically investigating the presence of tetragonal (t), cubic (c), and/or additional yttria-rich tetragonal (t') phase. METHODS Laboratory-fabricated specimens comprising 3-5YSZ, resembling translucent dental zirconia ceramics (TZ specimens), and a blend of 3YSZ and 8YSZ, representing a c-phase reference, were prepared. Additionally, 25 dental zirconia products stabilized with 3-6 mol% yttria were analyzed. Whole X-ray diffraction (XRD) patterns were obtained for Rietveld analysis, complemented by fine scanning in the 2θ region from 72º to 76º for qualitative phase analysis. Moreover, yttria concentrations in each specimen were determined using X-ray fluorescence (XRF) spectroscopy. RESULTS In the 2θ region from 72º to 76º, TZ and dental zirconia product specimens displayed four peaks attributed to t- and t'-phases, but the c-phase peak was absent. Rietveld analysis of the whole XRD patterns, utilizing a t-t' model, demonstrated the t-phase fraction ranging from 86 mass% in 3YSZ to 11 mass% in 6YSZ. Rietveld analysis appeared reliable, as the yttria contents calculated based on lattice parameters aligned well with those measured by XRF. This study established that dental 3-6YSZ consisted of yttria-lean t- and yttria-rich t'-phases. SIGNIFICANCE The present study enhances understanding of the crystalline structure of dental zirconia ceramics. Future crystallographic analyses of these ceramics should consider the presence of t- and t'-phases.
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Affiliation(s)
- Keisuke Nakamura
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980 8575, Japan; Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
| | - Shunichi Shishido
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980 8575, Japan
| | - Ryoichi Inagaki
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980 8575, Japan
| | - Taro Kanno
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980 8575, Japan
| | - Sargon Barkarmo
- Department of Prosthetic Dentistry/Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Per Svanborg
- Department of Prosthetic Dentistry/Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Ulf Örtengren
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden; Department of Material Science and Technology, Faculty of Odontology, Malmö University, SE-206 05 Malmö, Sweden
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Shishido S, Inagaki R, Kanno T, Svanborg P, Barkarmo S, Örtengren U, Nakamura K. Residual stress associated with crystalline phase transformation of 3-6 mol% yttria-stabilized zirconia ceramics induced by mechanical surface treatments. J Mech Behav Biomed Mater 2023; 146:106067. [PMID: 37567065 DOI: 10.1016/j.jmbbm.2023.106067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/13/2023]
Abstract
Monolithic dental prostheses made of 3-6 mol% yttria-stabilized zirconia (3-6YSZ) have gained popularity owing to their improved material properties and semi-automated fabrication processes. In this study, we aimed to evaluate the influence of mechanical surface treatments, such as polishing, grinding, and sandblasting, on the residual stress of 3-6YSZ used for monolithic prostheses in association with crystalline phase transformation. Plate specimens were prepared from five dental zirconia blocks: Aadva Zirconia ST (3YSZ), Aadva Zirconia NT (6YSZ), Katana HT (4YSZ), Katana STML (5YSZ), and Katana UTML (6YSZ). The specimens were either polished using 1, 3, or 9 μm diamond suspensions, ground using 15, 35, or 55 μm diamond discs, or sandblasted at 0.2, 0.3, or 0.4 MPa. The residual stress, crystalline phase, and hardness were analyzed using the cosα method, X-ray diffraction (XRD), and Vickers hardness test, respectively. Additionally, we analyzed the residual stress on the surfaces of monolithic zirconia crowns (MZCs) made of 4YSZ, 5YSZ, and 6YSZ, which were processed using clinically relevant procedures, including manual grinding, followed by polishing using a dental electric motor on the external surface, and sandblasting on the internal surface. Residual stress analysis demonstrated that grinding and sandblasting, particularly the latter, resulted in the generation of compressive residual stress on the surfaces of the plate specimens. XRD revealed that the ground and sandblasted specimens contained a larger amount of the rhombohedral phase than that of the polished specimens, which may be a cause of the residual stress. Sandblasting significantly increased the Vickers hardness compared to polishing, which may possibly be due to the generation of compressive residual stress. In the case of MZCs, compressive residual stress was detected not only on the sandblasted surface, but also on the polished surface. The difference in the residual stress between the plate and crown specimens may be related to the force applied during the automated and manual grinding and polishing procedures. Further studies are required to elucidate the effects of the compressive residual stress on the clinical performance of MZCs.
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Affiliation(s)
- Shunichi Shishido
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan.
| | - Ryoichi Inagaki
- Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
| | - Taro Kanno
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
| | - Per Svanborg
- Department of Prosthetic Dentistry / Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Sargon Barkarmo
- Department of Prosthetic Dentistry / Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Ulf Örtengren
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Keisuke Nakamura
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
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Erdinç G, Bülbül M, Özcan M. Fracture strength and energy-dispersive spectroscopy analysis of 3-unit fixed partial dentures fabricated from different monolithic zirconia materials. J Prosthet Dent 2023:S0022-3913(23)00178-6. [PMID: 37024356 DOI: 10.1016/j.prosdent.2023.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 03/08/2023] [Accepted: 03/09/2023] [Indexed: 04/08/2023]
Abstract
STATEMENT OF PROBLEM Mastication forces in different regions affect the survival of multiunit posterior restorations. The fracture strength of 3-unit posterior monolithic zirconia fixed partial dentures (FPDs) and their fracture patterns require investigation. PURPOSE The purpose of this in vitro study was to evaluate and compare the fracture strength and fracture pattern of 3-unit posterior FPDs fabricated from different monolithic zirconia materials. MATERIAL AND METHODS Thirty 3-unit FPDs were fabricated from BruxZir, FireZr, and Upcera (n=10 per group). Energy-dispersive spectroscopy analysis was performed on 2 selected specimens from each group. All specimens were exposed to a mastication simulator for 1.2×106 cycles and then monotonically loaded to fracture at a crosshead speed of 1 mm/min. The surfaces of a selected fractured specimen were examined at magnifications of ×25 and ×500 with scanning electron microscopy. Conformity to normal distribution was evaluated with the Shapiro-Wilk test. One-way analysis of variance was used to compare the normally distributed initial crack formation load F initial (Fi) and catastrophic failure strength F maximum (Fm) means by group. Weibull statistics were calculated by using the maximum likelihood estimation method. The chi-square test was used to compare shape and scale parameters (α=.05). RESULTS The mean Fm values were fail1878.9 N for Upcera, 2177.8 N for BruxZir, and 2229.4 N for FireZr. Upcera and BruxZir showed statistically significant differences for the Fm mean values (P=.039). The differences between the fracture type distributions according to the groups were statistically similar (P>.05). For Fi, Upcera presented the highest Weibull modulus value (2.199), FireZr had the lowest (1.594), while for Fm, BruxZir had the highest Weibull modulus value (9.267) and FireZr the lowest (6.572). CONCLUSIONS Using the zirconia materials BruxZir, FireZr, and Upcera resulted in high Fm values after aging procedures. With all materials, the fractures were most commonly found in the connector areas in the tested FPDs.
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Affiliation(s)
- Gülbahar Erdinç
- Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Karabük University, Karabük, Turkey.
| | - Mehmet Bülbül
- Professor, Department of Prosthodontics, Faculty of Dentistry, İstanbul Aydin University, İstanbul, Turkey
| | - Mutlu Özcan
- Professor and Head, Division of Dental Biomaterials, Clinic for Reconstructive Dentistry, Center for Dental and Oral Medicine, University of Zurich, Zurich, Switzerland
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Thickness and internal adjustment of monolithic resin composite milled crowns: Effect on the load-bearing capacity under fatigue. J Mech Behav Biomed Mater 2022; 134:105407. [DOI: 10.1016/j.jmbbm.2022.105407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/23/2022] [Accepted: 07/26/2022] [Indexed: 11/24/2022]
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Nawafleh N, Elshiyab S, Öchsner A, George R. In Vitro Fatigue and Fracture Load of Monolithic Ceramic Crowns Supported by Hybrid Abutment. Open Dent J 2021. [DOI: 10.2174/1874210602115010664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Objective:
This study evaluated the performance of zirconia and lithium disilicate crowns supported by implants or cemented to epoxy resin dies.
Methods:
Eigthy zirconia and lithium disilicate crowns each were prepared and assigned in four groups according to the crown material and supporting structure combinations (implant-supported zirconia, die-supported zirconia, implant-supported lithium disilicate, and die-supported lithium disilicate). Ten crowns in each group acted as control while the rest (n=10) underwent thermocycling and fatigue with 100 N loading force for 1.5 million cycles. Specimens were then loaded to fracture in a universal testing machine. Data were analysed using one-way ANOVA and Tukey multiple comparison test with a 95% level of significance.
Results:
No implants or crown failure occurred during fatigue. The mean fracture load values (control, fatigued) in newton were as follows: (4054, 3344) for implant-supported zirconia, (3783, 3477) for die-supported zirconia, (2506, 2207) for implant-supported lithium disilicate, and (2159, 1806) for die-supported lithium disilicate. Comparing the control with the corresponding fatigued subgroup showed a significantly higher fracture load mean of the control group in all cases. Zirconia showed a significantly higher fracture load mean than lithium disilicate (P=0.001, P<0.001). However, comparing crowns made from the same material according to the supporting structure showed no significant difference (P=0.923, P=0.337).
Conclusion:
Zirconia and lithium disilicate posterior crowns have adequate fatigue and fracture resistance required for posterior crowns. However, when heavy fatigue forces are expected, zirconia material is preferable over lithium disilicate. Zirconia and lithium disilicate implant-supported crowns cemented to hybrid abutments should have satisfactory clinical performance.
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Prott LS, Spitznagel FA, Bonfante EA, Malassa MA, Gierthmuehlen PC. Monolithic zirconia crowns: effect of thickness reduction on fatigue behavior and failure load. J Adv Prosthodont 2021; 13:269-280. [PMID: 34777717 PMCID: PMC8558575 DOI: 10.4047/jap.2021.13.5.269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/30/2021] [Accepted: 09/14/2021] [Indexed: 11/23/2022] Open
Abstract
PURPOSE The objective of this study was to evaluate the effect of thickness reduction and fatigue on the failure load of monolithic zirconia crowns. MATERIALS AND METHODS 140 CAD-CAM fabricated crowns (3Y-TZP, inCorisTZI, Dentsply-Sirona) with different ceramic thicknesses (2.0, 1.5, 1.0, 0.8, 0.5 mm, respectively, named G2, G1.5, G1, G0.8, and G0.5) were investigated. Dies of a mandibular first molar were made of composite resin. The zirconia crowns were luted with a resin composite cement (RelyX Unicem 2 Automix, 3M ESPE). Half of the specimens (n = 14 per group) were mouth-motion-fatigued (1.2 million cycles, 1.6 Hz, 200 N/ 5 – 55℃, groups named G2-F, G1.5-F, G1-F, G0.8-F, and G0.5-F). Single-load to failure was performed using a universal testing-machine. Fracture modes were analyzed. Data were statistically analyzed using a Weibull 2-parameter distribution (90% CI) to determine the characteristic strength and Weibull modulus differences among the groups. RESULTS Three crowns (21%) of G0.8 and five crowns (36%) of G0.5 showed cracks after fatigue. Characteristic strength was the highest for G2, followed by G1.5. Intermediate values were observed for G1 and G1-F, followed by significantly lower values for G0.8, G0.8-F, and G0.5, and the lowest for G0.5-F. Weibull modulus was the lowest for G0.8, intermediate for G0.8-F and G0.5, and significantly higher for the remaining groups. Fatigue only affected G0.5-F. CONCLUSION Reduced crown thickness lead to reduced characteristic strength, even under failure loads that exceed physiological chewing forces. Fatigue significantly reduced the failure load of 0.5 mm monolithic 3Y-TZP crowns.
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Affiliation(s)
- Lea Sophia Prott
- Department of Prosthodontics, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University, Düsseldorf, Germany
| | - Frank Akito Spitznagel
- Department of Prosthodontics, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University, Düsseldorf, Germany
| | - Estevam Augusto Bonfante
- Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo, Bauru, SP, Brazil
| | | | - Petra Christine Gierthmuehlen
- Department of Prosthodontics, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University, Düsseldorf, Germany
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Sadeqi HA, Baig MR, Al-Shammari M. Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems. MATERIALS 2021; 14:ma14216346. [PMID: 34771872 PMCID: PMC8585271 DOI: 10.3390/ma14216346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 10/15/2021] [Accepted: 10/20/2021] [Indexed: 11/24/2022]
Abstract
Fit accuracy and fracture strength of milled monolithic zirconia (Zi) and zirconia-reinforced lithium silicate (ZLS) crowns are important parameters determining the success of these restorations. This study aimed to evaluate and compare the marginal and internal fit of monolithic Zi and ZLS crowns, along with the fracture load, with and without mechanical aging. Thirty-two stone dies acquired from a customized master metal molar die were scanned, and ceramic crowns (16 Zi Ceramill Zolid HT+ and 16 ZLS Vita Suprinity) were designed and milled. Absolute marginal discrepancies (AMD), marginal gaps (MG), and internal gaps (IG) of the crowns, in relation to the master metal die, were evaluated using x-ray nanotomography (n = 16). Next, thirty-two metal dies were fabricated based on the master metal die, and crowns (16 Zi; 16 ZLS) cemented and divided into four groups of eight each; eight Zi with mechanical aging (MA), eight Zi without mechanical aging (WMA), eight ZLS (MA), and eight ZLS (WMA). Two groups of crowns (Zi-MA; ZLS-MA) were subjected to 500,000 mechanical cycles (200 ± 50 N, 10 Hz) followed by axial compressive strength testing of all crowns, until failure, and the values were recorded. Independent sample t tests (α = 0.05) revealed no significant differences between Zi and ZLS crowns (p > 0.05); for both internal and marginal gaps, however, there were significant differences in AMD (p < 0.005). Independent samples Mann–Whitney U and Kruskal–Wallis tests revealed significant differences between the two materials, Zi and ZLS, regardless of fatigue loading, and for the individual material groups based on aging (α = 0.05). Multiple comparisons using Bonferroni post-hoc analysis showed significant differences between Zi and ZLS material groups, with or without aging. Within the limitations of this study, the ZLS crown fit was found to be on par with Zi, except for the AMD parameter. As regards fracture resistance, both materials survived the normal range of masticatory forces, but the Zi crowns demonstrated greater resistance to fracture. The monolithic Zi and ZLS crowns seem suitable for clinical application, based on the fit and fracture strength values obtained.
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Affiliation(s)
- Haneen A. Sadeqi
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, P.O. Box 24923,
Safat 13110, Kuwait; (H.A.S.); (M.A.-S.)
| | - Mirza Rustum Baig
- Department of Restorative Sciences (Prosthodontics), Faculty of Dentistry, Kuwait University, P.O. Box 24923,
Safat 13110, Kuwait
- Correspondence:
| | - Mohammad Al-Shammari
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, P.O. Box 24923,
Safat 13110, Kuwait; (H.A.S.); (M.A.-S.)
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Nakamura K, Tarkeshi A, Niklasson A, Shishido S, Svanborg P, Barkarmo S, Örtengren U. Influence of crystalline phase transformation induced by airborne-particle abrasion and low-temperature degradation on mechanical properties of dental zirconia ceramics stabilized with over 5 mol% yttria. J Mech Behav Biomed Mater 2021; 125:104890. [PMID: 34673358 DOI: 10.1016/j.jmbbm.2021.104890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 10/05/2021] [Accepted: 10/10/2021] [Indexed: 11/30/2022]
Abstract
Monolithic dental prostheses fabricated from 5 mol% yttria-stabilized zirconia (5YZ) have been developed to improve the translucency of conventional 3 mol% yttria-stabilized zirconia. In this study, we aimed to evaluate the influence of airborne-particle abrasion (APA) and low-temperature degradation (LTD) on the mechanical properties of 5YZ in association with the crystalline phase transformation. In total, 120 disc-shaped specimens of two brands of 5YZ (Lava Esthetic and Katana UTML) were prepared. The specimens were divided into four groups (n = 15 for each group): (i) control, (ii) APA, (iii) LTD, and (iv) APA + LTD groups. APA was performed with 50 μm alumina particles, and LTD was induced by autoclaving at 134 °C for 50 h. The biaxial flexural strength of the specimens was assessed using a piston-on-three-ball test according to ISO 6872:2015, and Vickers hardness was determined using a microhardness tester. The crystalline phase was analyzed by the Rietveld refinement of X-ray diffraction patterns. APA significantly increased the flexural strength of the Lava Esthetic specimens, whereas LTD hardly affected the strength of both materials. APA and APA + LTD significantly increased the Vickers hardness of both materials. According to Rietveld analysis, the pseudocubic phase was predominant in both materials, i.e., 66 mass% and 81 mass% in the Lava Esthetic and Katana UTML specimens, respectively. APA induced the rhombohedral phase at approximately 37 mass% in both materials, while LTD induced the monoclinic phase at 2.8 mass% in the Lava Esthetic specimens and 0.9 mass% in the Katana UTML specimens. APA + LTD weakly affected the amount of the rhombohedral phase but slightly increased the amount of the monoclinic phase. These findings suggest that APA may improve the mechanical properties of 5YZ, particularly hardness, via the generation of the rhombohedral phase. In contrast, the influence of LTD on the mechanical and microstructural properties of 5YZ was limited.
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Affiliation(s)
- Keisuke Nakamura
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan.
| | - Aria Tarkeshi
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Alexander Niklasson
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Shunichi Shishido
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
| | - Per Svanborg
- Department of Prosthetic Dentistry/Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Sargon Barkarmo
- Department of Prosthetic Dentistry/Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Ulf Örtengren
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
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Tekin YH, Hayran Y. Fracture resistance and marginal fit of the zirconia crowns with varied occlusal thickness. J Adv Prosthodont 2020; 12:283-290. [PMID: 33149849 PMCID: PMC7604235 DOI: 10.4047/jap.2020.12.5.283] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 06/26/2020] [Accepted: 08/13/2020] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The present study aimed to evaluate the clinical applicability of monolithic zirconia (MZ) crowns of different thickness via determination of fracture resistance and marginal fit. MATERIALS AND METHODS MZ crowns with 0.5, 0.8, 1.0, and 1.5 mm thickness and porcelain fused to metal (PFM) crowns were prepared, ten crowns in each group. Marginal gaps of the crowns were measured. All crowns were aged with thermal cycling (5 - 55℃/10000 cycle) and chewing simulator (50 N/1 Hz/lateral movement: 2 mm, mouth opening: 2 mm/240000 cycles). After aging, fracture resistance of crowns was determined. Statistical analysis was performed with one-way ANOVA and Tukey's HDS post hoc test. RESULTS Fracture loads were higher in the PFM and 1 mm MZ crowns compared to 0.5 mm and 0.8 mm crowns. 1.5 mm MZ crowns were not broken even with the highest force applied (10 kN). All marginal gap values were below 86 µm even in the PFM crowns, and PFM crowns had a higher marginal gap than the MZ crowns. CONCLUSION The monolithic zirconia exhibited high fracture resistance and good marginal fit even with the 0.5 mm thickness, which might be used with reduced occlusal thickness and be beneficial in challengingly narrow interocclusal space.
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Affiliation(s)
- Yadel Hazır Tekin
- Department of Prosthodontic Dentistry, Faculty of Dentistry, Tokat Gaziosmanpasa University, Tokat, Turkey
| | - Yeliz Hayran
- Department of Prosthodontic Dentistry, Faculty of Dentistry, Tokat Gaziosmanpasa University, Tokat, Turkey
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Ellakwa A, Raju R, Sheng C, Rajan G, Prusty BG. Acoustic emission and finite element study on the influence of cusp angles on zirconia dental crowns. Dent Mater 2020; 36:1524-1535. [PMID: 32981750 DOI: 10.1016/j.dental.2020.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 08/04/2020] [Accepted: 09/06/2020] [Indexed: 10/23/2022]
Abstract
OBJECTIVE The effect of cusp angle on the load-carrying capacity and failure behaviour of BionZ Diamond zirconia crowns is carried out using experimental and numerical investigations. METHODS The experimental program using monolithic crowns were divided into three groups (n = 14) for three cusp angles, 60, 80 and 120 degrees and were tested to failure under the static load. A 2-channel acoustic emission (AE) system was used to monitor the failure process while the piezo sensors were attached to the rigid stainless-steel jig for recoding the AE events. Load-displacement and AE response were simultaneously monitored until failure of specimens. Parametric AE analysis was conducted for the factors such as amplitude, energy released, signal duration and cumulative counts, for each AE signal. Fast Fourier transform (FFT) was conducted to assess the frequency at failure. Linear finite element analysis (FEA) was carried out using commercial software Ansys Workbench 19.1 to present the stress distribution and failure modes. Post-failure surface morphology study was carried out using scanning electron microscopy (SEM) and statistical analysis was performed using Weibull analysis. RESULTS All the samples in three different groups have failed at the mid-line, splitting the zirconia crowns into two equal pieces. The load to failure was directly proportional to the cusp angle in crowns; 120° group had the highest load-carrying capacity of 2.93 ± 0.26 kN while 60 and 80° groups had a failure load of 2.46 ± 0.53 and 2.52 ± 0.16 kN, respectively. Parametric AE analysis revealed that the failure was instantaneous and 60-degree samples had higher AE signature. FE analysis showed the crack initiation at the occlusal surface of the crown which is in agreement with the SEM images. A close agreement of results for the load and stress distribution from FEA complemented with the experimental study. SIGNIFICANCE Optimisation of cusp-angle could help clinicians to accurately design the monolithic zirconia crown focussing on maximum load-carrying capacity, increasing the restoration life.
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Affiliation(s)
- Ayman Ellakwa
- Biomaterials Unit & Department of Prosthodontics and Oral Rehabilitation, Sydney Dental School, University of Sydney, Sydney, NSW 2010, Australia.
| | - Raju Raju
- School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
| | - Cai Sheng
- School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australia
| | - Ginu Rajan
- School of Electrical, Computer & Telecommunications Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
| | - B Gangadhara Prusty
- ARC Centre for Automated Manufacture of Advanced Composites, School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australia
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Harada A, Shishido S, Barkarmo S, Inagaki R, Kanno T, Örtengren U, Egusa H, Nakamura K. Mechanical and microstructural properties of ultra-translucent dental zirconia ceramic stabilized with 5 mol% yttria. J Mech Behav Biomed Mater 2020; 111:103974. [PMID: 32769070 DOI: 10.1016/j.jmbbm.2020.103974] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/02/2020] [Accepted: 07/03/2020] [Indexed: 11/27/2022]
Abstract
Monolithic dental prostheses fabricated from 3 mol.% yttria-stabilized zirconia (3YZ) are becoming increasingly popular. Recently, 5 mol.% yttria-stabilized zirconia (5YZ) which significantly improves the translucency of 3YZ has been prepared. However, its mechanical and microstructural properties, especially those affected by low-temperature degradation (LTD), have not been fully elucidated yet. The objective of the present study was to establish the relationship between the flexural strength of 5YZ with or without autoclave-induced LTD and its microstructural properties. For this purpose, a total of 320 bar-shaped specimens were cut from 5YZ and 3YZ blocks, and half of the specimens in each group were autoclaved at 134 °C for 50 h. Their flexural strengths were determined by conducting three-point bending tests, and the obtained results were analyzed by the Weibull statistical method. Grain sizes and crystalline structures of the specimens were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, respectively. Additionally, the LTD-induced phase transformation was examined by Raman microscopy and cross-sectional surface analysis. The characteristic strengths of 5YZ and 3YZ were approximately 620 and 950 MPa, respectively, and 5YZ was found to be more resistant to LTD in terms of phase transformation than 3YZ. However, a low amount of the monoclinic phase was detected even in 5YZ after 50 h of autoclaving, which significantly decreased its flexural strength and reliability. The results of SEM analysis revealed that 5YZ was composed of two distinct regions: a dominant matrix with large grains (median size: 0.8 μm) and scattered areas with small grains (median size: 0.4 μm). Phase transformation analysis and fractography data indicated that the small-grain region was strongly affected by LTD and likely represented a fracture origin. The described properties should be considered during the clinical application of monolithic 5YZ dental prostheses.
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Affiliation(s)
- Akio Harada
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, 980 8575, Japan
| | - Shunichi Shishido
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
| | - Sargon Barkarmo
- Department of Prosthetic Dentistry / Dental Materials Science, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Ryoichi Inagaki
- Tohoku University School for Dental Laboratory Technicians, Sendai, 980 8575, Japan
| | - Taro Kanno
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan
| | - Ulf Örtengren
- Department of Cariology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, SE-405 30, Gothenburg, Sweden
| | - Hiroshi Egusa
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, 980 8575, Japan
| | - Keisuke Nakamura
- Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan.
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12
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Nawafleh N, Bibars AR, Al Twal E, Öchsner A. Influence of Antagonist Material on Fatigue and Fracture Resistance of Zirconia Crowns. Eur J Dent 2020; 14:200-205. [PMID: 32311751 PMCID: PMC7274834 DOI: 10.1055/s-0040-1708228] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Objective
This study investigates the influence of the most commonly used indenter materials on fatigue survival and fracture resistance of zirconia crowns.
Materials and Methods
A total of 40 zirconia crowns were prepared using computer-aided design (CAD)/computer-aided manufacturing (CAM) technology: 30 crowns were divided into three experimental groups of 10 specimens and the last 10 specimens acted as the control group. The experimental groups were subjected to chewing simulation with simultaneous thermocycling. Three indenter materials (steatite ceramic, stainless steel, and tungsten carbide) with identical diameter were used to load the specimens. All crowns were then subjected to single load to fracture test in universal testing machine. Load was applied vertically with a crosshead speed of 1 mm/min until failure, and fracture load was recorded.
Statistical Analysis
Normal distribution of data was confirmed using the Shapiro–Wilk test. Descriptive statistics including means and standard deviations were determined for all groups. Differences between groups were tested using Dunnett’s test and paired sample
t
-test.
Results
Chewing simulation for 1.2 million cycles resulted in 100% survival. The highest mean fracture load was recorded for the control group and the lowest one was for the group fatigued with stainless steel indenter. Chewing simulation statistically significantly (
p
< 0.05) reduced the mean fracture load of the crowns fatigued with stainless steel and steatite ceramic indenter. However, the mean fracture load for the crowns fatigued with tungsten carbide was not significantly different from that of the control group.
Conclusion
Steatite ceramic and stainless steel indenters produced close results and significantly reduced fracture load of zirconia crowns. However, tungsten carbide indenter caused nonsignificant reduction in the fracture load of zirconia crowns.
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Affiliation(s)
- Noor Nawafleh
- Department of Applied Dental Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan
| | - Abdel Raheem Bibars
- Department of Applied Dental Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan
| | - Elina Al Twal
- Department of Applied Dental Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan
| | - Andreas Öchsner
- Faculty of Mechanical Engineering, Esslingen University of Applied Sciences, Esslingen, Germany.,Faculty of Engineering and Built Environment, University of Newcastle, Newcastle, Australia
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Bakitian F, Papia E, Larsson C, Vult von Steyern P. Evaluation of Stress Distribution in Tooth-Supported Fixed Dental Prostheses Made of Translucent Zirconia with Variations in Framework Designs: A Three-Dimensional Finite Element Analysis. J Prosthodont 2020; 29:315-322. [PMID: 31971307 DOI: 10.1111/jopr.13146] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2020] [Indexed: 11/29/2022] Open
Abstract
PURPOSE To evaluate the influence of the framework designs on the stress distribution within tooth-supported partially veneered fixed dental prostheses (FDPs) made of translucent zirconia under simulated loads using a three-dimensional finite element analysis (3D-FEA). MATERIAL AND METHODS For a linear 3D-FEA, simplified 3D solid models of prepared abutment teeth (first premolar and first molar) with different 3-unit FDPs were created. The models with different FDP designs-monolithic zirconia (control); semi-monolithic zirconia with 0.3 mm veneer thickness (SM0.3); semi-monolithic zirconia with 0.5 mm veneer thickness (SM0.5); semi-monolithic zirconia with 0.5 mm veneer thickness supported with cap design (SMC), and semi-monolithic zirconia with 0.5 mm veneer thickness supported with wave design (SMW)-were analyzed using 3D-FEA. The elastic properties of the components (bone, dentine, cement, translucent zirconia, and veneering porcelain) were obtained from the published data for FEA. Simulated static loading forces (300 N) were applied at 10° oblique direction over six points in the occlusal surfaces of the FDPs. Maximum principal stress, shear stress, and safety factor were calculated and analyzed among the different models. RESULTS Semi-monolithic with cap design showed the smallest maximum principal stress levels in the veneering porcelain compared to all other models (SM0.3, SM0.5, SMW). The SM0.3 had lower maximum principal stress levels in the veneering porcelain compared to SM0.5. Regarding stresses in the zirconia framework, all models had comparable results in maximum principal tensile stresses, except SMW had a lower value. Maximum principal stress levels were located in the veneer component of SM0.3, SM0.5, and SMW, whereas, such levels were observed in the cervical areas of the zirconia frameworks of SMC and control. The SM0.3 had the highest maximum shear stress levels at the zirconia-veneer interface, while SMW had the lowest shear values. The 3D-FEA models with different FDP designs showed different minimum safety factor levels. CONCLUSIONS Framework and veneer designs play a significant role in the stress distribution of the partially veneered zirconia FDPs under loading. The FDPs with zirconia frameworks with cap design minimize the maximum principal tensile stress in the veneering porcelain. The FDPs with 0.3-mm-veneering porcelain show low maximum principal tensile stress in the veneering porcelain, but highest maximum shear stress at the zirconia-veneer interface. The FDPs with wave design of zirconia frameworks minimize the maximum shear stress considerably.
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Affiliation(s)
- Fahad Bakitian
- Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Malmö, Sweden.,Department of Restorative Dentistry, Faculty of Dentistry, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Evaggelia Papia
- Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Malmö, Sweden
| | - Christel Larsson
- Department of Prosthodontics, Faculty of Odontology, Malmö University, Malmö, Sweden
| | - Per Vult von Steyern
- Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Malmö, Sweden
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14
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Abstract
Zirconia‐based restorations are showing an increase as the clinicians’ preferred choice at posterior sites because of the strength and esthetic properties of such restorations. However, all‐ceramic restorations fracture at higher rates than do metal‐based restorations. Margin design is one of several factors that can affect the fracture strength of all‐ceramic restorations. The aim of this study was to assess the effect of preparation and crown margin design on fracture resistance. Four groups of bilayer zirconia crowns (with 10 crowns in each group) were produced by hard‐ or soft‐machining technique, with the following four different margin designs: chamfer preparation (control); slice preparation; slice preparation with an additional cervical collar of 0.7 mm thickness; and reduced occlusal thickness (to 0.4 mm) on slice preparation with an additional cervical collar of 0.7 mm thickness. Additionally, 10 hard‐machined crowns with slice preparation were veneered and glazed with feldspathic porcelain. In total, 90 crowns were loaded centrally in the occlusal fossa until fracture. The load at fracture was higher than clinically relevant mastication loads for all preparation and margin designs. The crowns on a chamfer preparation fractured at higher loads compared with crowns on a slice preparation. An additional cervical collar increased load at fracture for hard‐machined crowns.
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Affiliation(s)
- Anneli Skjold
- Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Christian Schriwer
- Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Marit Øilo
- Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, Bergen, Norway
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