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Karevan Y, Eldafrawy M, Herman R, Sanchez C, Sadoun M, Mainjot A. Do all ceramic and composite CAD-CAM materials exhibit equal bonding properties to implant Ti-base materials? An Interfacial Fracture Toughness Study. Dent Mater 2024:S0109-5641(24)00218-5. [PMID: 39107223 DOI: 10.1016/j.dental.2024.07.014] [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: 06/04/2024] [Revised: 07/19/2024] [Accepted: 07/23/2024] [Indexed: 08/09/2024]
Abstract
OBJECTIVES To compare the interfacial fracture toughness (IFT) with or without aging, of four different classes of CAD-CAM ceramic and composite materials bonded with self-adhesive resin cement to titanium alloy characteristic of implant abutments. METHODS High translucent zirconia (Katana; KAT), lithium disilicate-based glass-ceramic (IPS. emax.CAD; EMX), polymer-infiltrated ceramic network material (PICN) (Vita Enamic; ENA), and dispersed filler composite (Cerasmart 270; CER) were cut into equilateral triangular prisms and bonded to titanium prisms with identical dimensions using Panavia SA Cement Universal. The surfaces were pretreated following the manufacturers' recommendations and developed interfacial area ratio (Sdr) of the pretreated surfaces was measured. IFT was determined using the Notchless Triangular Prism test in a water bath at 36 °C before and after thermocycling (10,000 cycles) (n = 40 samples/material). RESULTS IFT of the materials ranged from 0.80 ± 0.25 to 1.10 ± 0.21 MPa.m1/2 before thermocycling and from 0.71 ± 0.24 to 1.02 ± 0.25 MPa.m1/2 after thermocycling. There was a statistical difference between IFT of CER and the two top performers in each scenario: KAT and EMX before aging, and KAT and ENA after aging. Thermocycling significantly decreased IFT of EMX. The Weibull modulus of IFT was similar for all materials and remained so after thermocycling. Sdr measurements revealed that ENA (7.60)>Ti (4.97)>CER (2.85)>KAT (1.09)=EMX (0.96). SIGNIFICANCE Dispersed filler CAD-CAM composite showed lower performance than the other materials. Aging only affected IFT of Li-Si glass-ceramic, whereas zirconia and PICN performed equally well, probably due to their chemical bonding potential and surface roughness respectively.
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Affiliation(s)
- Yousef Karevan
- Dental Biomaterials Research Unit (d-BRU), Institute of Dentistry, University of Liège (ULiège), Liège, Belgium
| | - Maher Eldafrawy
- Dental Biomaterials Research Unit (d-BRU), Institute of Dentistry, University of Liège (ULiège), Liège, Belgium
| | - Raphael Herman
- Dental Biomaterials Research Unit (d-BRU), Institute of Dentistry, University of Liège (ULiège), Liège, Belgium
| | - Christelle Sanchez
- Department of Fixed Prosthodontics, Institute of Dentistry, University of Liège Hospital (CHU), Liège, Belgium
| | | | - Amélie Mainjot
- Department of Fixed Prosthodontics, Institute of Dentistry, University of Liège Hospital (CHU), Liège, Belgium.
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Gil-Pozo A, Astudillo-Rubio D, Ferrando Cascales Á, Inchingolo F, Hirata R, Sauro S, Delgado-Gaete A. Effect of gastric acids on the mechanical properties of conventional and CAD/CAM resin composites - An in-vitro study. J Mech Behav Biomed Mater 2024; 155:106565. [PMID: 38718723 DOI: 10.1016/j.jmbbm.2024.106565] [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: 02/21/2024] [Revised: 04/29/2024] [Accepted: 04/30/2024] [Indexed: 05/28/2024]
Abstract
OBJECTIVES Dental erosion in patients with gastroesophageal reflux disease (GERD) is a current and frequent condition that may compromise the mechanical properties and clinical durability of resin-based composites (RBCs). This study assessed the mechanical properties of conventional and computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs subsequent to simulated gastric acid aging. MATERIALS AND METHOD Three conventional and three CAD/CAM composites were assessed. They were divided into an experimental group (exposed to simulated gastric acid aging) and a control group (no aging). Both groups were analyzed for Vickers microhardness (VHN), wear and flexural strength over a period of six months. The failure rate probability for each RBC was calculated through the Weibull cumulative distribution function (m). Statistical analysis was conducted using repeated measures ANOVA, 3-way ANOVA, a non-parametric Kruskal-Wallis and U Mann-Whitney tests (α = 0.05). RESULTS The mechanical properties of all the RBCs dropped significantly after aging (p < 0.05). Lower VHN and flexural strength values, along with greater wear values were evident in the experimental groups, though the effects of the treatment varied between RBCs. The Weibull m of all the RBCs decreased over time. CONCLUSION Conventional RBCs might show greater reduction in mechanical properties compared to CAD/CAM RBCs when exposed to gastric acid attack. Thus, CAD/CAM composites may represent a suitable choice for the treatment of patients presenting erosive issues.
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Affiliation(s)
- Alexandra Gil-Pozo
- Division of Prosthodontics, School of Dentistry, Universidad Católica de Cuenca, 010107, Cuenca, Ecuador.
| | - Daniela Astudillo-Rubio
- Division of Prosthodontics, School of Dentistry, Universidad Católica de Cuenca, 010107, Cuenca, Ecuador.
| | - Álvaro Ferrando Cascales
- Department of Biomaterials Engineering, Faculty of Medicine, UCAM, Universidad Católica de Murcia, Campus de los Jerónimos, 135 Guadalupe, 30107, Murcia, Spain.
| | - Francesco Inchingolo
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124, Bari, Italy.
| | - Ronaldo Hirata
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, 10010, USA.
| | - Salvatore Sauro
- Dental Biomaterials and Minimally Invasive Dentistry, Departamento de Odontología, Facultad de Ciencias de la Salud, Universidad CEU-Cardenal Herrera, C/Del Pozo ss/n, Alfara del Patriarca, 46115, Valencia, Spain.
| | - Andrés Delgado-Gaete
- Division of Prosthodontics, School of Dentistry, Universidad Católica de Cuenca, 010107, Cuenca, Ecuador.
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Mayinger F, Ender A, Strickstrock M, Elsayed A, Nassary Zadeh P, Zimmermann M, Stawarczyk B. Impact of the sintering parameters on the grain size, crystal phases, translucency, biaxial flexural strength, and fracture load of zirconia materials. J Mech Behav Biomed Mater 2024; 155:106580. [PMID: 38759588 DOI: 10.1016/j.jmbbm.2024.106580] [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: 03/12/2024] [Revised: 05/06/2024] [Accepted: 05/10/2024] [Indexed: 05/19/2024]
Abstract
OBJECTIVES To investigate the influence of the zirconia and sintering parameters on the optical and mechanical properties. METHODS Three zirconia materials (3/4Y-TZP, 4Y-TZP, 3Y-TZP) were high-speed (HSS), speed (SS) or conventionally (CS) sintered. Disc-shaped specimens nested in 4 vertical layers of the blank were examined for grain size (GS), crystal phases (c/t'/t/m-phase), translucency (T), and biaxial flexural strength. Fracture load (FL) of three-unit fixed dental prostheses was determined initially and after thermomechanical aging. Fracture types were classified, and data statistically analyzed. RESULTS 4Y-TZP showed a higher amount of c + t'-phase and lower amount of t-phase, and higher optical and lower mechanical properties than 3Y-TZP. In all materials, T declined from Layer 1 to 4. 3/4Y-TZP showed the highest FL, followed by 3Y-TZP, while 4Y-TZP showed the lowest. In 4Y-TZP, the sintering parameters exercised a direct impact on GS and T, while mechanical properties were largely unaffected. The sintering parameters showed a varying influence on 3Y-TZP. Thermomechanical aging resulted in comparable or higher FL. CONCLUSION 3/4Y-TZP presenting the highest FL underscores the principle of using strength-gradient multi-layer blanks to profit from high optical properties in the incisal area, while ensuring high mechanical properties in the lower areas subject to tensile forces. With all groups exceeding maximum bite forces, the examined three-unit FDPs showed promising long-term mechanical properties.
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Affiliation(s)
- Felicitas Mayinger
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
| | - Andreas Ender
- Division of Computerized Restorative Dentistry, Clinic of Conservative and Preventive Dentistry, Center of Dental Medicine, University of Zurich, Plattenstrasse 11, 8032, Zurich, Switzerland
| | - Monika Strickstrock
- Faculty of Engineering and Computer Science, Material Science and Analysis, University of Applied Sciences Osnabrück, Albrechtstraße 30, 49076, Osnabrück, Germany
| | - Adham Elsayed
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Parissa Nassary Zadeh
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Marcus Zimmermann
- Division of Computerized Restorative Dentistry, Clinic of Conservative and Preventive Dentistry, Center of Dental Medicine, University of Zurich, Plattenstrasse 11, 8032, Zurich, Switzerland
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
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Hoffmann M, Stawarczyk B, Günster J, Zocca A. Influence of additives and binder on the physical properties of dental silicate glass-ceramic feedstock for additive manufacturing. J Mech Behav Biomed Mater 2024; 155:106563. [PMID: 38678747 DOI: 10.1016/j.jmbbm.2024.106563] [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: 02/15/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
OBJECTIVES The aim of the study was to investigate the impact of organic additives (binder, plasticizer, and the cross-linking ink) in the formulation of water-based feedstocks on the properties of a dental feldspathic glass-ceramic material developed for the slurry-based additive manufacturing technology "LSD-print." MATERIAL AND METHODS Three water-based feldspathic feedstocks were produced to study the effects of polyvinyl alcohol (AC1) and poly (sodium 4-styrenesulfonate) (AC2) as binder systems. A feedstock without organic additives was tested as the control group (CG). Disc-shaped (n = 15) and bar (n = 7) specimens were slip-cast and characterized in the green and fired states. In the green state, density and flexural strength were measured. In the fired state, density, shrinkage, flexural strength (FS), Weibull modulus, fracture toughness (KIC), Martens parameters, and microstructure were analyzed. Disc-shaped and bar specimens were also cut from commercially available CAD/CAM blocks and used as a target reference (TR) for the fired state. RESULTS In the green state, CG showed the highest bulk density but the lowest FS, while the highest FS in the green state was achieved with the addition of a cross-linking ink. After firing, no significant differences in density and a similar microstructure were observed for all slip-cast groups, indicating that almost complete densification could be achieved. The CAD/CAM specimens showed the highest mean FS, Weibull modulus, and KIC, with significant differences between some of the slip-cast groups. SIGNIFICANCE These results suggest that the investigated feedstocks are promising candidates for the slurry-based additive manufacturing of restorations meeting the class 1a requirements according to DIN EN ISO 6871:2019-01.
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Affiliation(s)
- Moritz Hoffmann
- Department of Prosthetic Dentistry, Dental School, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, Dental School, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Jens Günster
- Division 5.4 Advanced Multi-materials Processing, Bundesanstalt für Materialforschung und -prüfung, Unter Den Eichen 87, 12205, Berlin, Germany; Institute of Non-Metallic Materials, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, Germany
| | - Andrea Zocca
- Division 5.4 Advanced Multi-materials Processing, Bundesanstalt für Materialforschung und -prüfung, Unter Den Eichen 87, 12205, Berlin, Germany
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Osuchukwu OA, Salihi A, Ibrahim A, Audu AA, Makoyo M, Mohammed SA, Lawal MY, Etinosa PO, Isaac IO, Oni PG, Oginni OG, Obada DO. Weibull analysis of ceramics and related materials: A review. Heliyon 2024; 10:e32495. [PMID: 39021991 PMCID: PMC11252889 DOI: 10.1016/j.heliyon.2024.e32495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 06/03/2024] [Accepted: 06/05/2024] [Indexed: 07/20/2024] Open
Abstract
It has been realized throughout the years that an ideal combination of high toughness, hardness and strength is required in many engineering applications that need load-bearing capabilities. Ceramics and related materials have significant constraints for structural and particular non-structural applications due to their low toughness and limited strength while having substantially superior hardness than typical metallic materials. For example, hydroxyapatite (HAp) has gained attention for applications in orthopaedic implants, dental materials, drug delivery, etc. Researchers have continued to strive to produce HAp materials with reliable properties within the acceptable Weibull modulus (m) for load bearing. The Weibull analysis (WA) is a statistical analysis adopted widely in reliability applications to detect failure periods. Researchers have confirmed it to be an effective technique to get results on the reliability of materials at a moderately low rate with assured reliability of the material or component. This review summarizes the WA and the steps in the Weibull method for its reliability analysis to predict the failure rate of ceramics like HAp and other related materials. Also, the applications of WA for these materials were reviewed. From the review, it was discovered that Weibull distribution is proven to confer to the feeblest-link concept. For brittle materials, it was revealed that the Weibull Modulus ranges from 2 to 40, and environment, production processes, and comparative factors are well-thought-out contributing factors for reliability. In addition, the confidence interval can be up to 95 %. The frequently used technique for reliability valuation is to syndicate the Weibull statistics. Also, a very narrow distribution is desirable to offer the expected likelihood. Furthermore, when paired with trials, Monte Carlo simulations prove to be a very helpful tool for forecasting the dependability of different estimate techniques and their optimization. Finally, if the equivalent m is anticipated to be high, it signifies that the material has a high degree of homogeneity of properties and high reliability. WA can find application in predicting the dependability and lifetime of materials, making it widely utilized in engineering and other disciplines. It is especially useful for analysing data in which the likelihood of failure per unit of time varies over time.
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Affiliation(s)
- Obinna Anayo Osuchukwu
- Department of Mechanical Engineering, Bayero University, Kano, 700241, Nigeria
- Multifunctional Materials Laboratory, Shell Office Complex, Department of Mechanical Engineering, Ahmadu Bello University, Zaria, 810222, Nigeria
| | - Abdu Salihi
- Department of Mechanical Engineering, Bayero University, Kano, 700241, Nigeria
| | - Abdullahi Ibrahim
- Department of Mechanical Engineering, Bayero University, Kano, 700241, Nigeria
| | | | - Mahdi Makoyo
- Department of Mechanical Engineering, Bayero University, Kano, 700241, Nigeria
| | | | - Mohammed Y. Lawal
- Mechanical Engineering Department, Nigerian Defence Academy, Kaduna, PMB 2109, Nigeria
| | - Precious Osayamen Etinosa
- Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | - Ibitoye Opeyemi Isaac
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | - Peter Gbenga Oni
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | | | - David Olubiyi Obada
- Department of Mechanical Engineering, Ahmadu Bello University, Zaria, 810222, Nigeria
- Africa Centre of Excellence on New Pedagogies in Engineering Education, Ahmadu Bello University, Zaria, 810222, Nigeria
- Multifunctional Materials Laboratory, Shell Office Complex, Department of Mechanical Engineering, Ahmadu Bello University, Zaria, 810222, Nigeria
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Hoffmann M, Mayinger F, Stawarczyk B. Influence of different surface finishing procedures of strength-gradient multilayered zirconia crowns on two-body wear and fracture load: Lithium silicate or leucite glazing versus polishing? J Mech Behav Biomed Mater 2024; 150:106307. [PMID: 38071838 DOI: 10.1016/j.jmbbm.2023.106307] [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: 10/01/2023] [Revised: 11/29/2023] [Accepted: 12/03/2023] [Indexed: 01/09/2024]
Abstract
OBJECTIVES To examine the influence of different finishing procedures on the surface roughness, wear resistance and fracture load of strength-gradient multilayered zirconia. MATERIALS AND METHODS Zirconia crowns (Multilayer 3D pro; n = 96) were manufactured and treated with a lithium-silicate- (LISI_S), leucite-based glaze spray (LEU_S), leucite-based glaze mass (LEU_M) or polished (POL). Natural molars (CG; n = 24) acted as a control. Roughness was determined on flat glazed specimens (n = 28). Two-body wear was examined by digitalizing and matching the occlusal surface before and after thermo-mechanical aging (6,000 thermal and 1,200,000 chewing cycles). The groups were split to measure fracture load initially and after aging. Kolmogorov-Smirnov, Spearman correlation, Kruskal-Wallis-H, Levene's test, one-way ANOVA with Scheffé post-hoc and Weibull modulus were computed. RESULTS POL presented the lowest and LEU_S the highest roughness. Following POL, no ceramic loss was observed. LISI_S, LEU_S and LEU_M showed lower ceramic wear than the CG. The lowest wear of the antagonist was observed for the CG. LISI_S showed a lower antagonistic wear than LEU_S, LEU_M and POL. LISI_S, LEU_S, LEU_M and POL showed higher fracture load values and Weibull moduli than the CG. Artificial aging did not impact the fracture load or Weibull moduli. SIGNIFICANCE With glazed groups showing height losses closer to the CG, glazing should be preferred to polishing when approximating the wear behavior of a natural dentition. Finishing of monolithic zirconia by glazing with a lithium silicate-based spray is recommended to preserve the antagonists. All examined zirconia crowns presented sufficient mechanical properties to withstand masticatory forces, even after prolonged aging.
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Affiliation(s)
- Moritz Hoffmann
- Department of Prosthetic Dentistry, Dental School, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
| | - Felicitas Mayinger
- Department of Prosthetic Dentistry, Dental School, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, Dental School, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
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Mayinger F, Meinen J, Coldea A, Zimmermann M, Stawarczyk B. Digital versus conventional veneering of zirconia and cobalt chromium crowns: Fracture load before and after thermomechanical aging. J Prosthet Dent 2023; 130:251.e1-251.e8. [PMID: 37244796 DOI: 10.1016/j.prosdent.2023.04.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 04/28/2023] [Accepted: 04/28/2023] [Indexed: 05/29/2023]
Abstract
STATEMENT OF PROBLEM To complement the digital workflow for manufacturing fixed dental prostheses, both high-strength frameworks and esthetic veneers should be designed and fabricated digitally. However, how the fracture load of digitally veneered restorations compares with conventionally fabricated restorations is unclear. PURPOSE The purpose of this in vitro study was to examine the fracture load of digitally and conventionally veneered zirconia and cobalt chromium crowns initially and after thermomechanical aging. MATERIAL AND METHODS Milled zirconia and cobalt chromium copings for a maxillary canine were fabricated (N=96). Digital veneers were milled and connected to the copings with a sintered ceramic slurry. The conventional veneers were fabricated by using a master mold, and the crowns were bonded to the cobalt chromium abutments. Half the specimens were subjected to 6000 thermal (5 °C to 55 °C, 60 seconds) and 1 200 000 mechanical (50 N, 1.5 Hz, 0.7 mm lateral movement) cycles opposed by steatite antagonists, and the fracture load was determined. Fracture types were categorized, and scanning electron microscopy performed. The data were analyzed with a 3-way global univariate analysis of variance, t test, the Pearson chi-squared test, and the Weibull modulus (α=.05). RESULTS Unlike the framework material (P=.316) and artificial aging (P=.064), the veneering protocol affected the fracture load (P=.007). Digital veneers (range: 2242 to 2929 N) led to lower values than conventional veneers (range: 2825 to 3166 N), which was significant for aged cobalt chromium copings (P=.024; 2242 versus 3107 N). Conventionally veneered crowns showed lower Weibull moduli after thermomechanical aging (range: 3.2 to 3.5) than initially (range: 7.8 to 11.4). The copings of all the zirconia specimens fractured, while chipping occurred with the cobalt chromium specimens. CONCLUSIONS The high fracture load values of the veneered crowns, even after simulated 5-year aging, indicated sufficient mechanical properties (nearly 4-fold the average occlusal force of 600 N) for the successful clinical application of digitally veneered zirconia and cobalt chromium copings.
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Affiliation(s)
- Felicitas Mayinger
- Research Associate, Department of Prosthetic Dentistry, Dental School, Ludwig Maximilian University of Munich, Munich, Germany.
| | - John Meinen
- Dental Technician, Department of Prosthetic Dentistry, Dental School, Ludwig Maximilian University of Munich, Munich, Germany
| | - Andrea Coldea
- Research Associate, Department of Prosthetic Dentistry, Dental School, Ludwig Maximilian University of Munich, Munich, Germany
| | - Marcus Zimmermann
- Dental Technician, Division of Computerized Restorative Dentistry, Clinic of Conservative and Preventive Dentistry, Center of Dental Medicine, University of Zürich, Zürich, Switzerland
| | - Bogna Stawarczyk
- Professor, Department of Prosthetic Dentistry, Dental School, Ludwig Maximilian University of Munich, Munich, Germany
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Durán CR, Gancedo-Caravia DL, González VV, Losada CG. Push out bond strength of hydraulic cements used at different thicknesses. BMC Oral Health 2023; 23:81. [PMID: 36750823 PMCID: PMC9906962 DOI: 10.1186/s12903-023-02758-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 01/22/2023] [Indexed: 02/09/2023] Open
Abstract
BACKGROUND The aim of this study was to compare the pushout bond strength (POBS) of three hydraulic cements, when used at thicknesses of 3 and 5 mm. METHODS 78 root slices of 3 and 5 mm of thickness were obtained from human teeth. Cylindrical cavities of 1.4 mm of diameter were drilled and filled with Biodentine (BD), Totalfill Root Repair paste (TF) or ProRoot MTA White (PMTA). Pushout tests were performed 21 days later. The fracture pattern of each sample was also analyzed. POBS data were analyzed with Welch and Brown-Forsythe and Tamhane's post hoc tests and a Weibull analysis was also performed. RESULTS In the 3 mm group, TF showed significantly lower bond strength than BD and PMTA. In the 5 mm group, BD showed significantly higher bond strength than TF. Both BD and TF showed higher bond strength when the thickness of the sample increased, while PMTA did not. CONCLUSIONS TF and BD achieve higher pushout bond strength resistance when used at a thickness of 5 mm than at 3 mm, while the mean resistance of PMTA is less influenced by the thickness. At 5 mm of thickness, BD and PMTA exhibit similar resistance to displacement. However, the behavior of BD is more predictable than that of its predecessor. BD is a reliable hydraulic cement for clinical situations where thick cavities need to be filled and displacement resistance plays an important role. Clinicians need to consider choosing specific hydraulic cements according to the thickness of material to be used.
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Affiliation(s)
- C. Ruiz Durán
- grid.4795.f0000 0001 2157 7667Department of Consevative and Prosthetic Dentistry, School of Dentistry, Complutense University, Pza de Ramón y Cajal s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - Dra L. Gancedo-Caravia
- grid.4795.f0000 0001 2157 7667Department of Consevative and Prosthetic Dentistry, School of Dentistry, Complutense University, Pza de Ramón y Cajal s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - V. Vera González
- grid.4795.f0000 0001 2157 7667Department of Consevative and Prosthetic Dentistry, School of Dentistry, Complutense University, Pza de Ramón y Cajal s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - C. González Losada
- grid.4795.f0000 0001 2157 7667Department of Consevative and Prosthetic Dentistry, School of Dentistry, Complutense University, Pza de Ramón y Cajal s/n, Ciudad Universitaria, 28040 Madrid, Spain
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Jungbauer R, Hammer CM, Edelhoff D, Proff P, Stawarczyk B. Impact of different pretreatments and attachment materials on shear bond strength of indirectly bonded brackets using CAD/CAM transfer trays to monolithic zirconia. Dent Mater 2023; 39:170-180. [PMID: 36610899 DOI: 10.1016/j.dental.2022.12.006] [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: 05/23/2022] [Revised: 12/23/2022] [Accepted: 12/24/2022] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Investigating the impact of different pretreatment methods, attachment materials and aging regimens on shear bond strength (SBS) between zirconia and indirectly bonded brackets using CAD/CAM transfer trays. METHODS Zirconia substrates were conditioned with silica coated alumina (CoJet) and a) Clearfil Ceramic Primer Plus (CF), b) RelyX Ceramic Primer (RXP), c) Futurabond U (FU). Brackets were virtually placed, transfer tray designed (OnyxCeph) and 3D-printed for indirect bonding with a) Transbond LV (TBL), b) Nexus NX3 (NX3), c) Maximum Cure (MC). SBS testing was performed with a universal testing machine after 24 h, 500 thermal cycles, 90 d. Directly bonded brackets to human enamel using Transbond XT Adhesive served as control. The adhesive remnant index (ARI) was evaluated. Data was analyzed with Shapiro-Wilk, Kruskal-Wallis and Dunn's post-hoc test with Bonferroni correction, Chi2 test (p < 0.05), and the Weibull modulus was calculated. RESULTS SBS ranged from 0.1 to 15.5 MPa and were influenced mostly by the attachment material. NX3 generally showed the highest values (9.5-15.8 MPa). Initially RXP/TBL and FU/TBL presented the lowest values (4.3/4.8 MPa). Aging regimens reduced SBS of MC irrespective of pretreatment, after 90 d values ranged from 0.1 to 0.9 MPa. ARI 1 was predominant in all MC groups and FU/NX3, 2 and 3 in the other groups. Weibull moduli ranged between 0.15 (MC/RXP/500 TC) and 6.24 (NX3/RXP/500 TC). SIGNIFICANCE MC seems not to be suitable for indirect bonding using CAD/CAM transfer trays to zirconia. NX3 showed similar SBS values compared to the control, TBL lower.
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Affiliation(s)
- Rebecca Jungbauer
- Department of Orthodontics, University Medical Centre Regensburg, Regensburg, Germany; Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.
| | - Christian M Hammer
- Institute of Functional and Clinical Anatomy, Friedrich Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Daniel Edelhoff
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
| | - Peter Proff
- Department of Orthodontics, University Medical Centre Regensburg, Regensburg, Germany
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
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Delgado AH, Sauro S, Lima AF, Loguercio AD, Della Bona A, Mazzoni A, Collares FM, Staxrud F, Ferracane J, Tsoi J, Amato J, Neuhaus KW, Ceballos L, Breschi L, Hannig M, Melo MA, Özcan M, Scotti N, Opdam N, Yamaguchi S, Paris S, Turkun LS, Doméjean S, Rosa V, Palin W, Schwendicke F. RoBDEMAT: A risk of bias tool and guideline to support reporting of pre-clinical dental materials research and assessment of systematic reviews. J Dent 2022; 127:104350. [PMID: 36341980 DOI: 10.1016/j.jdent.2022.104350] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 10/10/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVES To develop a risk of bias tool for pre-clinical dental materials research studies that aims to support reporting of future investigations and improve assessment in systematic reviews. METHODS A four-stage process following EQUATOR network recommendations was followed, which included project launch, literature review, Delphi process and the tool finalization. With the support of the European Federation of Conservative Dentistry (EFCD) and the Dental Materials Group of the International Association for Dental Research (DMG-IADR), a total of 26 expert stakeholders were included in the development and Delphi vote of the initial proposal. The proposal was built using data gathered from the literature review stage. During this stage, recent systematic reviews featuring dental materials research, and risk of bias tools found in the literature were comprehensively scanned for bias sources. The experts thus reached a consensus for the items, domains and judgement related to the tool, allowing a detailed guide for each item and corresponding signalling questions. RESULTS The tool features nine items in total, spread between 4 domains, pertaining to the following types of bias: bias related to planning and allocation (D1), specimen preparation (D2), outcome assessment (D3) and data treatment and outcome reporting (D4). RoBDEMAT, as presented, features signalling questions and a guide that can be used for RoB judgement. Its use as a checklist is preferred over a final summary score. CONCLUSION RoBDEMAT is the first risk of bias tool for pre-clinical dental materials research, supported and developed by a broad group of expert stakeholders in the field, validating its future use. CLINICAL SIGNIFICANCE This new tool will contribute the study field by improving the scientific quality and rigour of dental materials research studies and their systematic reviews. Such studies are the foundation and support of future clinical research and evidence-based decisions.
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Affiliation(s)
- António Hs Delgado
- Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Monte de Caparica, Almada 2829-511 Portugal; Department of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, UK.
| | - Salvatore Sauro
- Dental Biomaterials and Minimally Invasive Dentistry, Department of Dentistry, Cardenal Herrera-CEU University, CEU Universities, Valencia, Spain
| | - Adriano F Lima
- Dental Research Division, Paulista University, Sao Paulo, Brazil
| | - Alessandro D Loguercio
- Department of Restorative Dentistry, School of Dentistry, State University of Ponta Grossa, PR, Brazil
| | - Alvaro Della Bona
- Postgraduate Program in Dentistry, School of Dentistry, University of Passo Fundo, Passo Fundo, RS, Brazil
| | - Annalisa Mazzoni
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna-Alma Mater Studiorum, Bologna, Italy
| | | | - Frode Staxrud
- Nordic Institute for Dental Materials (NIOM), Oslo, Norway
| | - Jack Ferracane
- Department of Restorative Dentistry, Oregon Health & Science University, 2730 S. Moody Avenue Portland, OR 97201, Oregon, USA
| | - James Tsoi
- Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR
| | - Julia Amato
- Department of Periodontology, Endodontology and Cariology, University Center for Dental Medicine Basel UZB, University of Basel, Basel, Switzerland
| | - Klaus W Neuhaus
- Department of Periodontology, Endodontology and Cariology, University Center for Dental Medicine Basel UZB, University of Basel, Basel, Switzerland; Department of Dermatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Laura Ceballos
- Nursing and Stomatology Department, Health Sciences Faculty, Rey Juan Carlos University, Alcorcón, Madrid, Spain
| | - Lorenzo Breschi
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna-Alma Mater Studiorum, Bologna, Italy
| | - Matthias Hannig
- Clinic of Operative Dentistry, Periodontology and Preventive Dentistry, Saarland University, 66421 Homburg, Germany
| | - Mary Anne Melo
- Division of Operative Dentistry, Department of General Dentistry, University of Maryland School of Dentistry, 650 West Baltimore St, Baltimore, MD 21201, USA
| | - Mutlu Özcan
- University of Zürich, Division of Dental Biomaterials, Center for Oral Medicine, Clinic for Reconstructive Dentistry, Zürich, Switzerland
| | - Nicola Scotti
- Department of Surgical Sciences, Dental School Lingotto, University of Turin, Turin, Italy
| | - Niek Opdam
- Radboud University Medical Centre, Department of Dentistry, Radboud Institute for Health Sciences, Nijmegen, The Netherlands
| | - Satoshi Yamaguchi
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
| | - Sebastian Paris
- Department of Operative, Preventive and Paediatric Dentistry, Center of Oral Health Sciences, Charité - Universitätsmedizin Berlin, Germany
| | - Lezize Sebnem Turkun
- Department of Restorative Dentistry, Ege University School of Dentistry, 35100 Bornova/Izmir Turkey
| | - Sophie Doméjean
- CHU Estaing, Service d'Odontologie, Clermont-Ferrand, France; Université Clermont Auvergne, UFR d'Odontologie, Clermont-Ferrand, France; Centre de Recherche en Odontologie Clinique EA 4847, Clermont-Ferrand, France
| | - Vinicius Rosa
- Faculty of Dentistry, National University of Singapore, Singapore; ORCHIDS: Oral Care Health Innovations and Designs Singapore, National University of Singapore, Singapore
| | - William Palin
- Dental and Biomaterials Sciences, School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, UK
| | - Falk Schwendicke
- Department of Operative and Preventive Dentistry, Charité - Universitätsmedizin Berlin, Germany, Aßmannshauser Str. 4-6, 14199 Berlin, German
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Elraggal A, Aboushelib M, Abdel Raheem IM, Afifi RR. Effect of surface treatments on biaxial flexural strength, fatigue resistance, and fracture toughness of high versus low translucency zirconia. BMC Oral Health 2022; 22:412. [PMID: 36123676 PMCID: PMC9487058 DOI: 10.1186/s12903-022-02431-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 09/05/2022] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Mechanical surface treatments can deteriorate the mechanical properties of zirconia. This study evaluated and compared the biaxial flexural strength, fracture toughness, and fatigue resistance of high translucency (HT) to low translucency (LT) zirconia after various mechanical surface treatments. METHODS Four hundred eighty zirconia discs were prepared by milling and sintering two HT (Katana and BruxZir) and LT (Cercon and Lava) zirconia blocks at targeted dimensions of 12 mm diameter × 1.2 mm thickness. Sintered zirconia discs received one of the following surface treatments: low-pressure airborne particle abrasion (APA) using 50 µm alumina particles, grinding using 400 grit silicon carbide paper, while as-sintered specimens served as control. Internal structure and surface roughness were evaluated by scanning electron microscope (SEM) and a non-contact laser profilometer, respectively. Half of the discs were tested for initial biaxial flexural strength, while the rest was subjected to 106 cyclic fatigue loadings, followed by measuring the residual biaxial flexural strength. Fractured surfaces were examined for critical size defects (c) using SEM to calculate the fracture toughness (KIC). The effect of surface treatments, zirconia type, and cyclic fatigue on the biaxial flexural strength was statistically analyzed using three-way analysis of variance (ANOVA) and Tukey HSD post hoc tests (α = 0.05). Weibull analysis was done to evaluate the reliability of the flexural strength for different materials. RESULTS The initial biaxial flexural strength of LT zirconia was significantly higher (p < 0.001) than that of HT zirconia in all groups. While low APA significantly increased the biaxial flexural strength of LT zirconia, no significant change was observed for HT zirconia except for Katana. Surface grinding and cyclic fatigue significantly reduced the flexural strength of all groups. High translucency zirconia reported higher fracture toughness, yet with lower Weibull moduli, compared to LT zirconia. CONCLUSION LT zirconia has higher biaxial flexural strength, yet with lower fracture toughness and fatigue resistance, compared to HT zirconia. Low-pressure APA has significantly increased the biaxial flexural strength in all zirconia groups except BruxZir. Grinding was deteriorating to biaxial flexural strength and fracture toughness in all zirconia types. Cyclic fatigue has significantly decreased the biaxial flexural strength and reliability of HT and LT zirconia.
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Affiliation(s)
- Alaaeldin Elraggal
- Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.
| | - Moustafa Aboushelib
- grid.7155.60000 0001 2260 6941Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt
| | - Islam M. Abdel Raheem
- grid.7155.60000 0001 2260 6941Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt
| | - Rania R. Afifi
- grid.7155.60000 0001 2260 6941Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt
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Mayinger F, Buser R, Laier M, Schönhoff LM, Kelch M, Hampe R, Stawarczyk B. Impact of the material and sintering protocol, layer thickness, and thermomechanical aging on the two-body wear and fracture load of 4Y-TZP crowns. Clin Oral Investig 2022; 26:6617-6628. [PMID: 35840737 DOI: 10.1007/s00784-022-04616-5] [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: 03/03/2022] [Accepted: 07/04/2022] [Indexed: 11/03/2022]
Abstract
OBJECTIVES The aim of this study is to investigate the influence of the material and corresponding sintering protocol, layer thickness, and aging on the two-body wear (2BW) and fracture load (FL) of 4Y-TZP crowns. MATERIALS AND METHODS Multi-layer 4Y-TZP crowns in three thicknesses (0.5 mm/1.0 mm/1.5 mm) were sintered by high-speed (Zolid RS) or conventional (Zolid Gen-X) sintering. 2BW of ceramic and enamel antagonist after aging (1,200,000 mechanical-, 6000 thermal-cycles) was determined by 3D-scanning before and after aging and subsequent matching to determine volume and height loss (6 subgroups, n = 16/subgroup). FL was examined initially and after aging (12 subgroups, n = 16/subgroup). Fractographic analyses were performed using light-microscope imaging. Global univariate analysis of variance, one-way ANOVA, linear regression, Spearman's correlation, Kolgomorov-Smirnov, Mann-Whitney U, and t test were computed (alpha = 0.05). Weibull moduli were determined. Fracture types were analyzed using Ciba Geigy table. RESULTS Material/sintering protocol did not influence 2BW (crowns: p = 0.908, antagonists: p = 0.059). High-speed sintered Zolid RS presented similar (p = 0.325-0.633) or reduced (p < 0.001-0.047) FL as Zolid Gen-X. Both 4Y-TZPs showed an increased FL with an increasing thickness (0.5(797.3-1429 N) < 1.0(2087-2634 N) < 1.5(2683-3715 N)mm; p < 0.001). For most groups, aging negatively impacted FL (p < 0.001-0.002). Five 0.5 mm specimens fractured, four showed cracks during and after aging. CONCLUSIONS High-speed sintered crowns with a minimum thickness of 1.0 mm showed sufficient mechanical properties to withstand masticatory forces, even after a simulated aging period of 5 years. CLINICAL RELEVANCE Despite the manufacturer indicating a thickness of 0.5 mm to be suitable for single crowns, a minimum thickness of 1.0 mm should be used to ensure long-term satisfactory results.
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Affiliation(s)
- Felicitas Mayinger
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
| | - Ramona Buser
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany.,Department of Reconstructive Dentistry and Gerodontology, University of Bern, Freiburgstrasse 7, 3007, Bern, Switzerland
| | - Maximilian Laier
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Lisa Marie Schönhoff
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Matthias Kelch
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Rüdiger Hampe
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, Dental School, LMU Munich, Goethestraße 70, 80336, Munich, Germany
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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]
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Jungbauer R, Proff P, Edelhoff D, Stawarczyk B. Impact of different pretreatments and attachment materials on shear bond strength between monolithic zirconia restorations and metal brackets. Sci Rep 2022; 12:8514. [PMID: 35595815 PMCID: PMC9123180 DOI: 10.1038/s41598-022-12542-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 05/11/2022] [Indexed: 11/25/2022] Open
Abstract
To investigate the influence of different pretreatment methods, attachment materials and artificial aging on shear bond strength (SBS) between monolithic zirconia and metal brackets. Zirconia substrates were pretreated with silica coated alumina (CoJet) and (1) clearfill ceramic primer plus (CF), (2) RelyX ceramic primer (RXP), (3) Futurabond U (FU). The brackets were bonded with (1) Transbond XT Adhesive (TB), (2) BrackFix Adhesive (BF), (3) bracepaste adhesive (BP). SBS was tested after 24 h, 500 thermal cycles, 90 d at 37 °C with a universal testing machine. SBS values reached from 8.3 to 16.9 MPa. The Weibull moduli ranged between 0.37 (RXP combined with BP after 90 d) and 7.42 (CF combined with TB after 24 h). The pretreatment with FU after 90 d, independent of the attachment material, and RXP with BF resulted in the lowest SBS values 8.3–9.9 MPa, the combination of RXP or CF with TB showed the highest (13.2–16.9 MPa) independent of aging. After FU pretreatment the proportion of ARI 1 and 0 was higher, of ARI 3 lower as after CF and RXP pretreatment. All tested combinations showed sufficiently high SBS values for clinical use. Pretreatment with FU presented the lowest values after 90 days.
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Affiliation(s)
- Rebecca Jungbauer
- Department of Orthodontics, University Medical Centre Regensburg, Regensburg, Germany. .,Department of Prosthetic Dentistry, LMU Munich, Munich, Germany.
| | - Peter Proff
- Department of Orthodontics, University Medical Centre Regensburg, Regensburg, Germany
| | - Daniel Edelhoff
- Department of Prosthetic Dentistry, LMU Munich, Munich, Germany
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15
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Micovic Soldatovic D, Liebermann A, Huth KC, Stawarczyk B. Fracture load of different veneered and implant-supported 4-UNIT cantilever PEEK fixed dental prostheses. J Mech Behav Biomed Mater 2022; 129:105173. [DOI: 10.1016/j.jmbbm.2022.105173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/04/2022] [Accepted: 03/07/2022] [Indexed: 11/16/2022]
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Kelch M, Stawarczyk B, Mayinger F. Chemical and mechanical properties of dual-polymerizing core build-up materials. Clin Oral Investig 2022; 26:4885-4896. [PMID: 35344103 PMCID: PMC9276564 DOI: 10.1007/s00784-022-04455-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 03/10/2022] [Indexed: 11/03/2022]
Abstract
OBJECTIVES To investigate the chemical (degree of conversion (DC)) and mechanical properties (Martens hardness (HM), elastic indentation modulus (EIT), and biaxial flexural strength (BFS)) of four dual-polymerizing resin composite core build-up materials after light- and self-polymerization. MATERIALS AND METHODS Round specimens with a diameter of 12 mm and a thickness of 1.5 mm were manufactured from CLEARFIL DC CORE PLUS (CLE; Kuraray), core·X flow (COR; Dentsply Sirona), MultiCore Flow (MUL; Ivoclar Vivadent), and Rebilda DC (REB; VOCO) (N = 96, n = 24/material). Half of the specimens were light-polymerized (Elipar DeepCure-S, 3 M), while the other half cured by self-polymerization (n = 12/group). Immediately after fabrication, the DC, HM, EIT, and BFS were determined. Data was analyzed using Kolmogorov-Smirnov, Mann-Whitney U, and Kruskal-Wallis tests, Spearman's correlation, and Weibull statistics (p < 0.05). RESULTS Light-polymerization either led to similar EIT (MUL; p = 0.119) and BFS (MUL and REB; p = 0.094-0.326) values or higher DC, HM, EIT, and BFS results (all other groups; p < 0.001-0.009). When compared with the other materials, COR showed a high DC (p < 0.001) and HM (p < 0.001) after self-polymerization and the highest BFS (p = 0.020) and Weibull modulus after light-polymerization. Positive correlations between all four tested parameters (R = 0.527-0.963, p < 0.001) were found. CONCLUSIONS For the tested resin composite core build-up materials, light-polymerization led to similar or superior values for the degree of conversion, Martens hardness, elastic indentation modulus, and biaxial flexural strength than observed after self-polymerization. Among the tested materials, COR should represent the resin composite core build-up material of choice due to its high chemical (degree of conversion) and mechanical (Martens hardness, elastic indentation modulus, and biaxial flexural strength) properties and its high reliability after light-polymerization. The examined chemical and mechanical properties showed a positive correlation. CLINICAL RELEVANCE The chemical and mechanical performance of dual-polymerizing resin composite core build-up materials is significantly affected by the chosen polymerization mode.
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Affiliation(s)
- Matthias Kelch
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany.
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany
| | - Felicitas Mayinger
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany
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YALÇINKAYA M, BİRGÖREN B. Shortest Confidence Intervals for Weibull Modulus for Small Samples in Materials Reliability Analysis. GAZI UNIVERSITY JOURNAL OF SCIENCE 2022. [DOI: 10.35378/gujs.916270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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de la Macorra JC, Romero B. Full mapping tensile bond strength of luting in search for differences due to centripetal curing shrinkage. Dent Mater 2022; 38:e69-e82. [PMID: 35241293 DOI: 10.1016/j.dental.2022.02.008] [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: 08/09/2021] [Revised: 12/21/2021] [Accepted: 02/19/2022] [Indexed: 11/16/2022]
Abstract
OBJECTIVES testing if hypothetical transverse centripetal strains due to polymerization contraction of luting materials produce differential alterations in its bonding to luted structures, depending on distances to the center of the luting mass, and if this effect is C-factor related. Two hypotheses were tested: (1) there is a statistically significant decreasing relationship between the bonding strength and the transverse distances to the center of the luting material, and (2) there is a statistically significant difference between bonding strengths among luting spaces with different configuration factors. METHODS 10 PMMA (15 mm Ø) pairs of cylinders were cemented (Scotchbond Universal adhesive & Relyx Universal, both chemically cured) in a compliant setup under two (20 and 70 N) luting forces forming 2 groups (5 samples each), resulting in different C-factors. Whole samples were sectioned in x and y directions obtaining non-trimmed beams from all along the luting surfaces. Their relative positions in each sample were assessed before separating and categorized (10 categories) according to their distances to the center of the sample. All beams were tested in tension and, because of their uneven bonding areas and to balance its influence, UTS results were transformed into UTSres. First hypothesis was tested trough a linear relationship between UTSres and distances to vertical centers per samples. Second hypothesis was tested using Mann-Whitney U tests to compare UTSres between groups, along all categories. Further Weibull analysis was applied. RESULTS ANOVA's p of the regression UTSres - categories were statistically significant for all samples in group 70 N and for all except one in group 20 N: first hypothesis is partially maintained. Although Mann-Whitney tests p comparing UTSres of both groups for all categories but the first were statistically significant this hypothesis was maintained relying in Weibull analysis. SIGNIFICANCE bonded attachment of cemented materials decreases from centers to outbounds in plane, extensive surfaces, and this decrease is C-factor related.
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Affiliation(s)
- José C de la Macorra
- Conservative Dentistry and Buccofacial Prosthesis Department, School of Dentistry. Complutense University, 28040 Madrid, Spain.
| | - Beatriz Romero
- School of Dentistry, Complutense University, 28040 Madrid, Spain
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Winter A, Schurig A, Odenthal AL, Schmitter M. Impact of different layers within a blank on mechanical properties of multi-layered zirconia ceramics before and after thermal aging. Dent Mater 2022; 38:e147-e154. [DOI: 10.1016/j.dental.2022.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 01/12/2022] [Accepted: 03/15/2022] [Indexed: 11/29/2022]
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Postpolymerization of a 3D-printed denture base polymer: Impact of post-curing methods on surface characteristics, flexural strength, and cytotoxicity. J Dent 2021; 115:103856. [PMID: 34695506 DOI: 10.1016/j.jdent.2021.103856] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/30/2021] [Accepted: 10/20/2021] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE This study investigated the influence of postpolymerization of a three-dimensional (3D) printed denture base polymer. The effect of post-curing methods on surface characteristics, flexural strength, and cytotoxicity was evaluated. METHODS A total of 172 specimens were additively manufactured using one denture base material (V-Print dentbase, VOCO) and further post-cured by different light-curing devices, including Otoflash G171 (OF), Labolight DUO (LL), PCU LED (PCU), and LC-3DPrintbox (PB), respectively. Polymethyl methacrylate resin (PalaExpress Ultra) was used as a reference (REF). Afterward, surface topography was observed using scanning electron microscopy, and surface roughness was measured (n = 6). Furthermore, flexural strength was tested (n = 20). Cytotoxicity was evaluated by the extract and direct contact tests. The data were analyzed using the Kolmogorov-Smirnov test and one-way ANOVA followed by Tukey's multiple comparisons and Kruskal-Wallis tests (p < 0.05). RESULTS The different post-curing methods applied did not significantly influence surface topography and roughness (Ra). Meanwhile, specimens post-cured by PCU (162.3 ± 44.16 MPa) and PB (171.2 ± 34.41 MPa) showed significantly higher flexural strength than those post-cured by OF (131.3 ± 32.87 MPa) and REF (131.2 ± 19.19 MPa), respectively. Additionally, various post-curing methods effectively decreased the cytotoxic effects of 3D-printed denture base polymer. CONCLUSIONS Different post-curing methods did not significantly alter the Ra values of the 3D-printed denture base material. However, flexural strength was significantly affected by the postpolymerization methods, which might be attributed to the different wavelengths of post-curing devices. In addition, various postpolymerization methods reduced the cytotoxic effects of the 3D-printed denture base polymer. CLINICAL SIGNIFICANCE Flexural strength of additively manufactured denture bases depends on the postpolymerization strategy. Therefore, an appropriate post-curing method is required to optimize the flexural strength of 3D-printed denture materials.
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Time-dependent degree of conversion, Martens parameters, and flexural strength of different dual-polymerizing resin composite luting materials. Clin Oral Investig 2021; 26:1067-1076. [PMID: 34342762 PMCID: PMC8791875 DOI: 10.1007/s00784-021-04091-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 07/19/2021] [Indexed: 12/02/2022]
Abstract
Objective To investigate the degree of conversion (DC), Martens hardness (HM), elastic indentation modulus (EIT), and biaxial flexural strength (BFS) of six dual-polymerizing resin composite luting materials initially and after 2 and 7 days of aging. Materials and methods Specimens fabricated from Bifix QM (BIF; VOCO), Calibra Ceram (CAL; Dentsply Sirona), DuoCem (DUO; Coltène/Whaledent), G-CEM LinkForce (GCE; GC Europe), PANAVIA V5 (PAN; Kuraray Europe), and Variolink Esthetic DC (VAR; Ivoclar Vivadent) (n = 12 per material) were light-polymerized through 1 mm thick discs (Celtra Duo, Dentsply Sirona). DC, HM, and EIT were recorded directly after fabrication, and after 2 and 7 days of aging. As a final test, BFS was measured. Univariate ANOVAs, Kruskal–Wallis, Mann–Whitney U, Friedman, and Wilcoxon tests, and Weibull modulus were computed (p < 0.05). Results While CAL presented low DC, HM, EIT, and BFS values, DUO and BIF showed high results. Highest Weibull moduli were observed for VAR and DUO. DC and Martens parameters increased between the initial measurement and 2 days of aging, while aging for 7 days provided no further improvement. Conclusions The choice of dual-polymerizing resin composite luting material plays an important role regarding chemical and mechanical properties, especially with patients sensitive to toxicological issues. DUO may be recommended for bonding fixed dental prostheses, as it demonstrated significantly highest and reliable results regarding DC, HM, and BFS. As DC and HM showed an increase in the first 48 h, it may be assumed that the polymerization reaction is not completed directly after initial polymerization, which is of practical importance to dentists and patients. Clinical relevance The chemical and mechanical properties of dual-polymerizing resin composite luting materials influence the overall stability and long-term performance of the restoration.
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Di Giglio S, Agüera A, Pernet P, M'Zoudi S, Angulo-Preckler C, Avila C, Dubois P. Effects of ocean acidification on acid-base physiology, skeleton properties, and metal contamination in two echinoderms from vent sites in Deception Island, Antarctica. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 765:142669. [PMID: 33268256 DOI: 10.1016/j.scitotenv.2020.142669] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/23/2020] [Accepted: 09/25/2020] [Indexed: 06/12/2023]
Abstract
Antarctic surface waters are expected to be the first to experience severe ocean acidification (OA) with carbonate undersaturation and large decreases in pH forecasted before the end of this century. Due to the long stability in environmental conditions and the relatively low daily and seasonal variations to which they are exposed, Antarctic marine organisms, especially those with a supposedly poor machinery to eliminate CO2 and protons and with a heavily calcified skeleton like echinoderms, are hypothesized as highly vulnerable to these environmental shifts. The opportunities offered by the natural pH gradient generated by vent activities in Deception Island caldera, Western Antarctic Peninsula, were used to investigate for the first time the acid-base physiologies, the impact of OA on the skeleton and the impact of pH on metal accumulation in the Antarctic sea star Odontaster validus and sea urchin Sterechinus neumayeri. The two species were sampled in four stations within the caldera, two at pH (total scale) 8.0-8.1 and two at reduced pH 7.8. Measured variables were pH, alkalinity, and dissolved inorganic carbon of the coelomic fluid; characteristic fracture force, stress and Young's modulus using Weibull statistics and Cd, Cu, Fe, Pb and Zn concentrations in the integument, gonads and digestive system. Recorded acid-base characteristics of both studied species fit in the general picture deduced from temperate and tropical sea stars and sea urchins but conditions and possibly confounding factors, principally food availability and quality, in the studied stations prevented definitive conclusions. Reduced seawater pH 7.8 and metals had almost no impact on the skeleton mechanical properties of the two investigated species despite very high Cd concentrations in O. validus integument. Reduced pH was correlated to increased contamination by most metals but this relation was weak. Translocation and caging experiments taking into account food parameters are proposed to better understand future processes linked to ocean acidification and metal contamination in Antarctic echinoderms.
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Affiliation(s)
- S Di Giglio
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, CP 160/15, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium.
| | - A Agüera
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, CP 160/15, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium; Institute of Marine Research in Norway, Austevoll Research Station, Sauganeset 16, 5392, Norway
| | - Ph Pernet
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, CP 160/15, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium
| | - S M'Zoudi
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, CP 160/15, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium
| | - C Angulo-Preckler
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, Tromsø, Norway
| | - C Avila
- Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology and Biodiversity Research Institute (IRBio), Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona, Catalonia, Spain
| | - Ph Dubois
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, CP 160/15, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium
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Impact of varying step-stress protocols on the fatigue behavior of 3Y-TZP, 4Y-TZP and 5Y-TZP ceramic. Dent Mater 2021; 37:1073-1082. [PMID: 33849757 DOI: 10.1016/j.dental.2021.03.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 03/08/2021] [Accepted: 03/28/2021] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To test the impact of three varying step-stress protocols on the fatigue behavior of two 3Y-TZP, one 4Y-TZP and one 5Y-TZP zirconia materials. METHODS Eight specimens per zirconia material (N = 32) were selected for static testing to determine the start load for dynamic tests (30% of the mean value of static fracture load). 45 specimens per material (N = 180) were used for dynamic load tests using three step-stress protocols: 1. 50 N/5000 cycles; 2. 5% of static load/5000 cycles, and 3. 10 N/1000 cycles. Following materials were tested: 3Y-TZP(<0.25 Al2O3) (O: opaque) 3Y-TZP(<0.05 Al2O3) (T: translucent), 4Y-TZP(<0.01 Al2O3) (ET: extra translucent) and 5Y-TZP(<0.01 Al2O3) (HT: high translucent). The specimens (4 ± 0.02 × 3 ± 0.02 × 45 mm) were placed centrally on the support rolls and the load was applied perpendicularly over the 4 mm specimen side (∼4-point flexural strength according to the DIN 6872:2019). Data was analyzed with Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé-test, Chi-square-test, Kaplan-Meier with Log-Rank-test and two-parametric Weibull analysis (p < 0.05). RESULTS The step-stress protocols showed no impact on the fracture load or Weibull modulus within one zirconia material. However, the zirconia materials T, ET and HT showed differences in cycle number to fracture between the step-stress protocols (T: 3 > 2 > 1; ET: 2 > 3 > 1; HT: 2, 3 > 1) with lowest cycle number to fracture for protocol 1. Within one step-stress protocol, the cycle number to fracture varied according to the zirconia material as follows: 1: T, O ≥ O, ET > HT; 2: ET > O, T, HT; 3: O, T, ET > HT. Cracking started at the tensile side of the specimens at all times. All specimens showed typical compression curls (single or double). Fragmentation patterns were similar for all materials with a lot of crack branching and fragmentation due to secondary cracks indicating high energy fractures. SIGNIFICANCE Dynamic fatigue tests seem to provide important information on the long-term stability of zirconia materials. Zirconia materials with higher opacity seem to be more robust towards varying step-stress protocols than translucent zirconia materials. Regarding expenditure of time, a step-stress protocol with a load increase of 50 N every 5000 cycles seems favorable to gain information on the long-term stability of zirconia materials.
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Schönhoff LM, Lümkemann N, Buser R, Hampe R, Stawarczyk B. Fatigue resistance of monolithic strength-gradient zirconia materials. J Mech Behav Biomed Mater 2021; 119:104504. [PMID: 33845296 DOI: 10.1016/j.jmbbm.2021.104504] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/24/2021] [Accepted: 03/29/2021] [Indexed: 11/18/2022]
Abstract
PURPOSE Evaluation of the effect of three different dynamic fatigue protocols on the fracture resistance of two monolithic strength-gradient zirconia materials. MATERIALS AND METHODS A total of 240 specimens (3 × 4 × 45 mm) was milled from two different layers (incisal and middle) of two types of strength-gradient zirconia blanks (IPS e. max ZirCAD MT Multi A2 vs. IPS e. max ZirCAD Prime A2), resulting in 60 specimens per material and layer group (IPS e. max ZirCAD MT Multi A2: incisal (MI), middle (MM); IPS e. max ZirCAD Prime A2: incisal (PI), middle (PM)). Each group was divided into one static (n = 15) and three dynamic fatigue protocols (N = 45, n = 15): i. 50 N increase every 5000 cycles ii. Increase by 5% of static fracture load every 5000 cycles iii. 10 N increase every 1000 cycles until facture. All specimens were loaded until facture in CeraTest 2 k. Kaplan-Meier, Log-Rank and Chi-squared-test as well as Weibull statistics were performed. A fractographic analysis was performed. The specimens were classified according to the number of crack origins and evaluated using the Ciba-Geigy table. RESULTS With regard to the fracture load, in the static loading MI and PI showed a higher fracture load and in dynamic fatigue protocol 2 PI showed a lower fracture load. The number of cycles until fracture only differed within three groups: MM and MI survived a higher number of cycles in dynamic fatigue protocol 2; PI survived a higher number of cycles in dynamic fatigue protocol 2 than in protocol 1. Within dynamic fatigue protocols, PM resisted the highest number of cycles in protocol 1 and 3 and MI in protocol 2. Comparing groups, Weibull modulus differed only within the static loading, with PI showing lower values than MM and MI. Within the material groups, MI showed higher values in static loading than in dynamic fatigue protocol 1 and 2, and PI showed higher values in the dynamic fatigue protocol 3 than in static loading. With regard to fracture patterns, no differences were found between the groups. CONCLUSIONS Dynamic fatigue protocols provide clinically relevant information on the long-term stability and reliability of monolithic strength-gradient zirconia materials. However, no definitive instructions for dynamic testing can be provided from this investigation.
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Affiliation(s)
- Lisa Marie Schönhoff
- Dental Material Unit, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Nina Lümkemann
- Dental Material Unit, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Ramona Buser
- Dental Material Unit, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany; Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Rüdiger Hampe
- Dental Material Unit, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany
| | - Bogna Stawarczyk
- Dental Material Unit, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
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Stawarczyk B, Mandl A, Liebermann A. Modern CAD/CAM silicate ceramics, their translucency level and impact of hydrothermal aging on translucency, Martens hardness, biaxial flexural strength and their reliability. J Mech Behav Biomed Mater 2021; 118:104456. [PMID: 33740686 DOI: 10.1016/j.jmbbm.2021.104456] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/05/2021] [Accepted: 03/08/2021] [Indexed: 10/21/2022]
Abstract
OBJECTIVES To investigate the impact of hydrothermal aging on Martens parameter (Martens hardness: HM/elastic indentation modulus: EIT) and biaxial flexural strength (BFS) of recently available CAD/CAM silicate ceramics. METHODS 220 specimens (diameter: 12 mm, thickness: 0.95 mm) were fabricated from six CAD/CAM ceramics in two translucency levels (LT/HT): (a) two lithium disilicate (Amber Mill, ABM; IPS e.max CAD, IEM), (b) one lithium metasilicate (Cetra Duo, CEL), (c) one lithium alumina silicate (n!ce, NIC), and (d) two leucite ceramics (Initial LRF Block, LRF; IPS Empress CAD, IPR). HM/EIT and BFS were measured initially and after hydrothermal aging (134 °C/0.2 MPa/100 h) in an autoclave. The Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé test, Kruskal-Wallis-test, Mann-Whitney-U-test with Bonferroni correction and Weibull statistics were performed (α = 0.05). RESULTS CEL and IEM showed the highest and the leucite ceramics the lowest Martens parameter. Within HT, ABM and NIC were in same initial HM value range with CEL and IEM. ABM and NIC showed lower initial EIT values than CEL and IEM, however higher than IPR. The lowest aged values were analyzed for ABM. After aging, Martens parameter decreased for LRF, ABM, and CEL. IEM showed the initial highest BFS, followed by ABM. NIC and LRF showed the lowest BFS. IEM and ABM presented the highest aged BFS. Hydrothermal aging increased BFS values for LRF (HT), IPR, CEL (HT), and NIC (HT) compared to the initial values. CAD/CAM leucite ceramics showed higher Weibull modul values compared to lithium silicate ceramics. SIGNIFICANCE The well-considered selection of ceramics in relation to the areas of indication has the highest influence on the long-term stability of restorations: CAD/CAM lithium disilicate ceramics presented the highest and leucite ceramics the lowest mechanical properties, whereas the reliability was better for leucite than for lithium silicate ceramics.
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Affiliation(s)
- Bogna Stawarczyk
- Department of Prosthetic Dentistry, LMU Munich, Munich, Germany.
| | - Alicia Mandl
- Department of Prosthetic Dentistry, LMU Munich, Munich, Germany
| | - Anja Liebermann
- Department of Prosthetic Dentistry, LMU Munich, Munich, Germany
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Influence of surface treatments and cyclic fatigue on subsurface defects and mechanical properties of zirconia frameworks. Dent Mater 2021; 37:905-913. [PMID: 33691991 DOI: 10.1016/j.dental.2021.02.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 02/16/2021] [Accepted: 02/24/2021] [Indexed: 11/22/2022]
Abstract
OBJECTIVES To evaluate the effect of laser fused and air abraded fluorapatite particles on flexural strength σf and fracture toughness (KIC) of Yttria tetragonal zirconia polycrystal (Y-TZP). METHODS 160 polished Y-TZP bars received one of the following surface treatments: airborne particle abrasion (APA) with fluorapatite glass-ceramics (FGC), APA with tribochemical silica-coated alumina (CoJet), laser fused FGC using Nd:YAG Laser (FGC + Laser), while as-sintered polished specimens served as control. Initial flexural strength σfI was measured to half of the specimens, while the rest underwent cyclic fatigue (1,000,000 cycle of 15N load and 3 s contact time) followed by measuring residual flexural strength σfR. Fractographic analysis was performed and KIC was calculated. The effect of surface treatment and fatigue on flexural strength was statistically analysed using 2-way ANOVA (α = 0.05). Weibull probability was measured to assess the reliability of flexural strength. RESULTS The highest σf before or after the fatigue was reported for the control group while the lowest was for FGC + Laser group. Cyclic fatigue significantly decreased the flexural strength of all groups except for FGC + Laser group. There was no significant difference between the KIC between the control and FGC groups, however, a significant reduction of KIC was found in the CoJet group, while FGC + Laser reported the significant lowest value compared to all groups (P = 0.00). SIGNIFICANCE Fluorapatite glass-ceramic powder offers a promising alternative for particle abrasion of zirconia-based frameworks.
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Spintzyk S, Geis-Gerstorfer J, Bourauel C, Keilig L, Lohbauer U, Brune A, Greuling A, Arnold C, Rues S, Adjiski R, Sawada T, Lümkemann N, Stawarczyk B, Ilie N, Frankenberger R, Dudek MC, Strickstrock M, Begand S. Biaxial flexural strength of zirconia: A round robin test with 12 laboratories. Dent Mater 2020; 37:284-295. [PMID: 33358016 DOI: 10.1016/j.dental.2020.11.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 09/02/2020] [Accepted: 11/21/2020] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The aim of this interlaboratory round robin test was to prove the robustness of the DIN EN ISO 6872:2019 and to identify the influence of processing and testing variations. METHODS Each of the 12 laboratories participated (A-L) received 60 (n = 720) assigned zirconia specimens. All participants seperated the specimens from the blanks, sintered them, polished half of all specimens and performed the biaxial flexural test (DIN EN ISO 6872:2019). The surface roughness was determined by using tactile measuring device. Fractographic examination was performed under scanning-electron-microscopy (SEM). Data was analysed using Kolmogorov-Smirnov-, Kruskal-Wallis-, Mann-Whitney-U-test and two-parametric Weibull statistic (p < 0.05). RESULTS The results for both preparation methods (as-fired and polished) showed significant differences for some participants. The values for as-fired groups ranged between 513 (I) and 659 (E) MPa. H showed higher Weibull modulus than C, E and I. Within polished groups flexural strengths values from 465 (L) to 1212 (E) MPa were observed, with a tendency to clustered groups A, I, J, L (465-689 MPa) and remaining groups (877-1212 MPa). E presented the highest and H the lowest Weibull modulus. Within A and J, no impact of the preparation method on flexural strength values was observed. Within L, as-fired specimens showed higher flexural strength than polished ones. The flexural strength increase did only associate to a certain extent with measured surface roughness. Fractography showed defect populations depending on polishing techniques, associated to the strength level, especially for polished groups. Reduced strength is related to machining defects, regardless of the surface state. SIGNIFICANCE DIN EN ISO 6872:2019 can be seen as guidance to biaxial flexural strength testing but additional effort is necessary to ensure interlaboratory comparability. Calibrated furnaces and reliable sintering conditions are mandatory requirements together with detailed specifications on finishing or polishing procedures. Biaxial flexural testing is really a matter of understanding specimen preparation, alignment and mechanical testing by itself. DIN EN ISO 6872:2019 should further recommend reporting of mean surface roughness along with any biaxial flexural strength data. Fractography is a mandatory tool in interpretation and understanding of strength data.
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Affiliation(s)
- Sebastian Spintzyk
- University Hospital Tübingen, Section "Medical Materials Science & Technology", Osianderstr. 2-8, 72076 Tuebingen, Germany.
| | - Jürgen Geis-Gerstorfer
- University Hospital Tübingen, Section "Medical Materials Science & Technology", Osianderstr. 2-8, 72076 Tuebingen, Germany
| | - Christoph Bourauel
- University Hospital Bonn, Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111 Bonn, Germany
| | - Ludger Keilig
- University Hospital Bonn, Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111 Bonn, Germany
| | - Ulrich Lohbauer
- University of Erlangen-Nuremberg, Dental Clinic 1 - Operative Dentistry and Periodontology, Glueckstrasse 11, 91054 Erlangen, Germany
| | - Annike Brune
- Hannover Medical School, Clinic for Dental Prosthetics, Carl-Neuberg-Straße 1, 30625 Hannover, Germany
| | - Andreas Greuling
- Hannover Medical School, Clinic for Dental Prosthetics, Carl-Neuberg-Straße 1, 30625 Hannover, Germany
| | - Christin Arnold
- Department of Prosthodontics, School of Dental Medicine, Martin-Luther-University, Magdeburger Str. 16, 06112 Halle (Saale), Germany
| | - Stefan Rues
- Department of Prosthodontics, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany
| | - Ranko Adjiski
- Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany
| | - Tomofumi Sawada
- Department of Prosthodontics, University Hospital Tübingen, Osianderstr. 2, -8, 72076 Tübingen, Germany
| | - Nina Lümkemann
- Department of Prosthetic Dentistry, University Hospital, Dental School, Ludwig-Maximilians-University Munich, Goethestraße 70, 80336 Munich, Germany
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, Dental School, Ludwig-Maximilians-University Munich, Goethestraße 70, 80336 Munich, Germany
| | - Nicoleta Ilie
- Department of Operative Dentistry and Periodontology, University Hospital, Dental School, Ludwig-Maximilians-University Munich, Goethestraße 70, 80336 Munich, Germany
| | - Roland Frankenberger
- Department of Operative Dentistry, Endodontics and Pediatric Dentistry, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, 35039 Marburg, Germany
| | - Marie-Christine Dudek
- Department of Operative Dentistry, Endodontics and Pediatric Dentistry, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, 35039 Marburg, Germany
| | - Monika Strickstrock
- Faculty of Engineering and Computer Science, Material Science and Analysis, University of Applied Sciences Osnabrück, Albrechtstrasse 30, Osnabrück 49076, Germany
| | - Sabine Begand
- Fraunhofer Institute for Ceramics Technologies and Systems IKTS, Michael-Faraday-Str. 1, 07639 Hermsdorf, Germany
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Mayinger F, Reymus M, Liebermann A, Richter M, Kubryk P, Großekappenberg H, Stawarczyk B. Impact of polymerization and storage on the degree of conversion and mechanical properties of veneering resin composites. Dent Mater J 2020; 40:487-497. [PMID: 33342921 DOI: 10.4012/dmj.2019-394] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To investigate the degree of conversion (DC), Martens hardness (HM), elastic indentation modulus (EIT), and flexural strength (FS) of veneering resin composites (SR Nexco Paste (NP), Ceramage Incisal (CI), Gradia Plus (GP); n=60/group) cured with different polymerization devices (bre.Lux Power Unit, Labolight DUO, Otoflash G171, LC-3DPrint Box, PCU LED; n=12/subgroup) after storage. Otoflash G171 and Labolight DUO showed increased DC/HM/EIT. CI presented the lowest DC and highest HM/EIT. NP showed the highest DC and lowest HM/EIT. Within Otoflash G171, Laboligth DUO and PCU LED, highest FS was observed for CI. Storage did not affect DC/HM/EIT for specimens cured with Otoflash G171 or Labolight DUO. With storage not showing an influence on the tested parameters for polymerization devices that otherwise presented superior results, increased storage time cannot be recommended. For the tested resin composites, this study observed a high/low degree of conversion to coincide with respectively low/high amounts of fillers/mechanical properties.
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Affiliation(s)
| | - Marcel Reymus
- Department of Conservative Dentistry and Periodontology, University Hospital, LMU Munich
| | - Anja Liebermann
- Department of Prosthetic Dentistry, University Hospital, LMU Munich
| | | | | | | | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, LMU Munich
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Evaluation of translucency, Marten's hardness, biaxial flexural strength and fracture toughness of 3Y-TZP, 4Y-TZP and 5Y-TZP materials. Dent Mater 2020; 37:212-222. [PMID: 33267975 DOI: 10.1016/j.dental.2020.11.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/20/2020] [Accepted: 11/02/2020] [Indexed: 11/20/2022]
Abstract
OBJECTIVES Testing and comparing of different non-shaded zirconia materials (3Y-TZP, 4Y-TZP and 5Y-TZP) on optical and mechanical properties. MATERIALS AND METHODS Zirconia materials (N = 320, Opaque O, Translucent T, Extra Translucent ET, High Translucent HT) were investigated on translucency, Martens parameter, biaxial flexural strength, Chevron-Notch-Beam (CNB) fracture toughness (KIC) and grain size. The grain size was analyzed using a scanning electron microcopy (SEM). Univariate ANOVA, post-hoc Scheffé, partial eta-squared, Kolmogorov-Smirnov-, Kruskal-Wallis- and Mann-Whitney-U-tests (p < 0.05) were performed. The reliability of flexural strength was calculated with two-parametric Weibull analysis and 95 % confidence level. RESULTS The translucency of ET and HT increased with the thermo-mechanical aging (p < 0.001). The zirconia material and aging had no impact on the Martens hardness and the indentation modulus. ET showed the highest flexural strength values after initial and thermo-mechanical aging (p < 0.001 - 0.683). All four materials showed the highest flexural strength after thermo-mechanical aging after 1.2 Mio cycles. Thermo-mechanically (1.2 Mio cycles) aged HT presented the highest Weibull modulus (m = 15.0) regardless of aging. Within initial groups, T (p ≤ 0.001) showed the highest fracture toughness, followed by O (p ≤ 0.001), ET (p < 0.003) and HT (p ≤ 0.001). SIGNIFICANCE Translucency of ET and HT increases with thermo-mechanical aging. Chevron-Notch-Beam (CNB) is a valid alternative to the single-edge-V-notched beam (SEVNB) method for testing fracture toughness.
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Mayinger F, Lümkemann N, Musik M, Eichberger M, Stawarczyk B. Comparison of mechanical properties of different reinforced glass-ceramics. J Prosthet Dent 2020; 127:146-153. [PMID: 33168175 DOI: 10.1016/j.prosdent.2020.06.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/11/2020] [Accepted: 06/11/2020] [Indexed: 11/24/2022]
Abstract
STATEMENT OF PROBLEM Data concerning the mechanical properties of the newly developed lithium disilicate ceramic HS10PC are lacking. PURPOSE The purpose of this in vitro study was to investigate the flexural strength (FS), Martens hardness (HM), indentation modulus (EIT), fracture load (FL), and wear resistance (WR) of HS10PC compared with those of the established glass-ceramics IPS e.max Press and IPS Empress Esthetic. MATERIAL AND METHODS Four pressable glass-ceramics were examined: HS10PC (estetic ceram ag), IPS e.max Press low translucency (LT) and high translucency (HT; Ivoclar Vivadent AG), and IPS Empress Esthetic (ES; Ivoclar Vivadent AG). For each material, a total of 85 specimens were fabricated. Specimens were subdivided into 4 groups for FS (n=30), HM, EIT (n=10), and FL measurement according to the Voss test after artificial aging in an autoclave (n=15), artificial aging in a mastication simulator (n=15), and no artificial aging (n=15). In addition, WR (n=10) was measured after 240 000, 600 000, and 1 200 000 masticatory cycles. Data were statistically analyzed using the global univariate ANOVA, the Scheffé post hoc and paired t tests, and Weibull distribution (α=.05). RESULTS HT showed the highest FS, while ES presented the lowest FS of all groups (P<.001). ES showed lower values for HM (P<.001), EIT (P<.001), and FL for specimens treated in an autoclave and mastication simulator (P<.001) compared with all other groups. An increase in the wear of the ceramic and enamel antagonist between 240 000 and 1 200 000 masticatory cycles was observed for all groups (P<.001). After 1 200 000 masticatory cycles, HS10PC presented less wear of the ceramic than the other 3 materials (P=.003). CONCLUSIONS The newly developed lithium disilicate ceramic HS10PC showed comparable results with the established IPS e.max Press for FS, HM, EIT, FL, and WR. Lithium disilicate ceramics presented higher mechanical results than the leucite-reinforced ES, with all the ceramics showing similar results for the WR of the enamel antagonist.
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Affiliation(s)
- Felicitas Mayinger
- Research Associate, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.
| | - Nina Lümkemann
- Research Associate, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
| | - Martyna Musik
- Research Associate, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
| | - Marlis Eichberger
- Dental Technician, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
| | - Bogna Stawarczyk
- Head of Dental Material Research, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany
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Michailova M, Elsayed A, Fabel G, Edelhoff D, Zylla IM, Stawarczyk B. Comparison between novel strength-gradient and color-gradient multilayered zirconia using conventional and high-speed sintering. J Mech Behav Biomed Mater 2020; 111:103977. [DOI: 10.1016/j.jmbbm.2020.103977] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 07/03/2020] [Accepted: 07/05/2020] [Indexed: 11/29/2022]
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Jerman E, Wiedenmann F, Eichberger M, Reichert A, Stawarczyk B. Effect of high-speed sintering on the flexural strength of hydrothermal and thermo-mechanically aged zirconia materials. Dent Mater 2020; 36:1144-1150. [PMID: 32620333 DOI: 10.1016/j.dental.2020.05.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/19/2020] [Accepted: 05/24/2020] [Indexed: 01/19/2023]
Abstract
OBJECTIVE To investigate the influence of high-speed and conventional sintering on the flexural strength (FS) of three zirconia materials initial and after artificial aging. METHODS Milled zirconia specimens (3Y-TZP: ZI and Zolid; 4Y-TZP: Zolid HT+; Amann Girrbach AG; N = 288, n = 96/group) were sintered in a high-speed sintering protocol (final temperature 1580 °C, n = 48/subgroup) or a conventional sintering protocol (control group, final temperature 1450 °C, n = 48/subgroup). FS was tested initially and after artificial aging (10 h in an autoclave or 1,200,000 chewing cycles; n = 16/subgroup). Univariate ANOVAs, post-hoc Scheffé, partial eta-squared, Kolmogorov-Smirnov-, Kruskal-Wallis- and Mann-Whitney-U-test were performed (p < 0.05). RESULTS ZI showed the highest and HT+ the lowest FS, regardless of the sintering protocols and aging regimens (p < 0.001). High-speed sintered HT+ showed higher initial FS than the control group (p < 0.001). ZI (p < 0.001-0.004) and Zolid (p < 0.001-0.007) showed higher FS after thermo-mechanical aging. High-speed sintered HT+ showed higher FS in the initial stage (p < 0.001). The Weibull modulus of the three thermo-mechanically aged materials was negatively influenced by high-speed sintering. SIGNIFICANCE As shorter sintering times represent a cost and time efficient alternative, high-speed sintering is a valid alternative to conventional sintering protocols.
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Affiliation(s)
- Eva Jerman
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians University, Goethestrasse 70, 80336 Munich, Germany.
| | - Felicitas Wiedenmann
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians University, Goethestrasse 70, 80336 Munich, Germany
| | - Marlis Eichberger
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians University, Goethestrasse 70, 80336 Munich, Germany
| | - Axel Reichert
- Research & Development, Amann Girrbach AG, Herrschaftswiesen 1, 6842 Koblach, Austria
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians University, Goethestrasse 70, 80336 Munich, Germany
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Di Giglio S, Spatafora D, Milazzo M, M'Zoudi S, Zito F, Dubois P, Costa C. Are control of extracellular acid-base balance and regulation of skeleton genes linked to resistance to ocean acidification in adult sea urchins? THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 720:137443. [PMID: 32325563 DOI: 10.1016/j.scitotenv.2020.137443] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 06/11/2023]
Affiliation(s)
- Sarah Di Giglio
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, 1050 Bruxelles, Belgium.
| | - Davide Spatafora
- Department of Earth and Marine Science (DiSTeM), Università degli studi di Palermo, 90146 Palermo, Italy
| | - Marco Milazzo
- Department of Earth and Marine Science (DiSTeM), Università degli studi di Palermo, 90146 Palermo, Italy
| | - Saloua M'Zoudi
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, 1050 Bruxelles, Belgium
| | - Francesca Zito
- Consiglio Nazionale Delle Ricerche, Istituto per la Ricerca e per l'Innovazione Biomedica (IRIB), Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Philippe Dubois
- Laboratoire de Biologie Marine, Université Libre de Bruxelles, 1050 Bruxelles, Belgium.
| | - Caterina Costa
- Consiglio Nazionale Delle Ricerche, Istituto per la Ricerca e per l'Innovazione Biomedica (IRIB), Via Ugo La Malfa 153, 90146 Palermo, Italy.
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STAWARCZYK B, LIEBERMANN A, ROSENTRITT M, POVEL H, EICHBERGER M, LÜMKEMANN N. Flexural strength and fracture toughness of two different lithium disilicate ceramics. Dent Mater J 2020; 39:302-308. [DOI: 10.4012/dmj.2019-045] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Bogna STAWARCZYK
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich
| | - Anja LIEBERMANN
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich
| | | | - Hubertus POVEL
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich
| | - Marlis EICHBERGER
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich
| | - Nina LÜMKEMANN
- Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich
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Stawarczyk B, Dinse L, Eichberger M, Jungbauer R, Liebermann A. Flexural strength, fracture toughness, three-body wear, and Martens parameters of pressable lithium-X-silicate ceramics. Dent Mater 2020; 36:420-430. [PMID: 32007315 DOI: 10.1016/j.dental.2020.01.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/26/2019] [Accepted: 01/14/2020] [Indexed: 11/24/2022]
Abstract
OBJECTIVES To test and compare five pressable lithium-X-silicate-ceramics on their mechanical and wear properties. METHODS Specimens were pressed and prepared from: i. Amber Press (AP), ii. Celtra Press (CP), iii. Initial LiSi Press (IL), iv. Livento Press (LP), and v. IPS e.max Press (IE). Four-point flexural strength (FS), SEVNB fracture toughness (KIC), three-body wear (3BW), Martens hardness (HM) and indentation modulus (EIT) were measured. For CP, FS and HM were measured with and without additional Power Firing. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA followed by Scheffé test, Kruskal-Wallis-H-, Mann-Whitney-U-, and Spearman-Rho-test (p < 0.05). The Weibull modulus was calculated using the maximum likelihood estimation method. RESULTS AP and CP presented higher FS than IL. LP presented the highest Weibull modulus. CP showed lower KIC values than AP, and AP was not significant compared to LP and IE. The most 3BW material loss was observed for CP. CP revealed higher HM values than the remaining ceramics. IL presented lower EIT compared to AP and CP. The following correlations were observed between the test parameters: 3BW with FS (r = 0.279, p = 0.015), with HM (r = -0.378, p = 0.001), and with EIT (r = -0.344, p = 0.004); EIT with FS (r = 0.203, p = 0.028); and HM with FT (r = -0.223, p = 0.027) and EIT (r = 0.884, p < 0.001). No correlations were observed between FS and KIC (r = 0.046; p = 0.346). SIGNIFICANCE AP followed by LP showed the highest and IL followed by CP the lowest properties tested. Power Firing of CP improved the flexural strength. Ceramics with high flexural strength and Martens parameters showed lower wear. Materials with high Martens hardness presented lower fracture toughness values and ones with high indentation modulus showed high flexural strength.
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Affiliation(s)
- Bogna Stawarczyk
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, 80336 Munich, Germany.
| | - Lina Dinse
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, 80336 Munich, Germany
| | - Marlis Eichberger
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, 80336 Munich, Germany
| | - Rebecca Jungbauer
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, 80336 Munich, Germany
| | - Anja Liebermann
- Department of Prosthetic Dentistry, University Hospital, LMU Munich, 80336 Munich, Germany
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Prechtel A, Stawarczyk B, Hickel R, Edelhoff D, Reymus M. Fracture load of 3D printed PEEK inlays compared with milled ones, direct resin composite fillings, and sound teeth. Clin Oral Investig 2020; 24:3457-3466. [PMID: 31989370 DOI: 10.1007/s00784-020-03216-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 01/17/2020] [Indexed: 02/04/2023]
Abstract
OBJECTIVE The objective of this in vitro study was to investigate fracture load, fracture types, and impact of chewing simulation of human molars restored with 3D printed indirect polyetheretherketone (PEEK) inlays and compare these with milled indirect PEEK inlays, direct resin composite fillings, and sound teeth. MATERIALS AND METHODS A total of 112 molars with form congruent class I cavities were restored with (n = 16/group) 3D printed indirect PEEK inlays via fused layer manufacturing (FLM): (1) Essentium PEEK (ESS), (2) KetaSpire PEEK MS-NT1 (KET), (3) VESTAKEEP i4 G (VES), (4) VICTREX PEEK 450G (VIC), (5) milled indirect PEEK inlays JUVORA Dental Disc 2 (JUV), and (6) direct resin composite fillings out of Tetric EvoCeram (TET). Sound teeth (7) acted as positive control group. Half of the specimens of each group (n = 8) were treated in a chewing simulator combined with thermal cycling (1.2 million × 50 N; 12,000 × 5 °C/55 °C). Fracture load and fracture types of all molars were determined. Statistical analyses using Kolmogorov-Smirnov test and two-way ANOVA with partial eta squared (ηp2) followed by Scheffé post hoc test, chi square test and Weibull modulus m with 95% confidence interval were computed (p < 0.05). RESULTS ESS and TET demonstrated the lowest fracture load with a minimum of 956 N, whereas sound molars showed the highest values of up to 2981 N. Chewing simulation indicated no impact (p = 0.132). With regard to Weibull modulus, KET presented a lower value after chewing simulation than JUV, whereas TET had the highest value without chewing simulation. All indirect restorations revealed a tooth fracture (75-100%), direct resin composite fillings showed a restoration fracture (87.5%), and 50% of the sound teeth fractured completely or had cusp fractures. CONCLUSIONS All 3D printed and milled indirect PEEK inlays as well as the direct resin composite fillings presented a higher fracture load than the expected physiological and maximum chewing forces. CLINICAL RELEVANCE 3D printing of inlays out of PEEK via FLM provided promising results in mechanics, but improvements in terms of precision and esthetics will be required to be practicable in vivo to represent an alternative dental material.
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Affiliation(s)
- Alexander Prechtel
- Department of Prosthetic Dentistry, Ludwig-Maximilians-Universität Munich, Goethestrasse 70, 80336, Munich, Germany.
| | - Bogna Stawarczyk
- Department of Prosthetic Dentistry, Ludwig-Maximilians-Universität Munich, Goethestrasse 70, 80336, Munich, Germany
| | - Reinhard Hickel
- Department of Conservative Dentistry and Periodontology, Ludwig-Maximilians-Universität Munich, Goethestrasse 70, 80336, Munich, Germany
| | - Daniel Edelhoff
- Department of Prosthetic Dentistry, Ludwig-Maximilians-Universität Munich, Goethestrasse 70, 80336, Munich, Germany
| | - Marcel Reymus
- Department of Conservative Dentistry and Periodontology, Ludwig-Maximilians-Universität Munich, Goethestrasse 70, 80336, Munich, Germany
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Using virtual samples to improve learning performance for small datasets with multimodal distributions. Soft comput 2019. [DOI: 10.1007/s00500-018-03744-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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JANSEN JU, LÜMKEMANN N, SENER B, STAWARCZYK B. Comparison of fracture toughness measurements for zirconia materials using two test methods. Dent Mater J 2019; 38:806-812. [DOI: 10.4012/dmj.2018-361] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Jan Ulrich JANSEN
- Department of Prosthetic Dentistry, Dental Material Unit, Ludwig-Maximilians-University Munich
| | - Nina LÜMKEMANN
- Department of Prosthetic Dentistry, Dental Material Unit, Ludwig-Maximilians-University Munich
| | - Beatrice SENER
- Periodontics and Cardiology, Clinic for Preventive Dentistry, University of Zurich
| | - Bogna STAWARCZYK
- Department of Prosthetic Dentistry, Dental Material Unit, Ludwig-Maximilians-University Munich
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Mohammed E M, Abd El-Rah DAES. A New High Accurate Estimation Method for Evaluating the Daily Solar Energy by Nested Percentiles Algorithm. ASIAN JOURNAL OF SCIENTIFIC RESEARCH 2019; 12:480-487. [DOI: 10.3923/ajsr.2019.480.487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Sawada T, Wagner V, Schille C, Spintzyk S, Schweizer E, Geis-Gerstorfer J. Effect of slow-cooling protocol on biaxial flexural strengths of bilayered porcelain-ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) disks. Dent Mater 2018; 35:270-282. [PMID: 30522698 DOI: 10.1016/j.dental.2018.11.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 11/13/2018] [Accepted: 11/15/2018] [Indexed: 10/27/2022]
Abstract
OBJECTIVE The present study investigated the biaxial flexural strengths of bilayered ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) disks with various layering porcelains veneered using a slow-cooling protocol. METHODS Five porcelain materials (VITA VM9, Cercon Ceram Kiss, and Vintage ZR with experimental coefficient of thermal expansions; CTEs of 8.45, 9.04, and 9.61ppm/°C) were veneered on Ce-TZP/A disks and slow-cooled after firing to fabricate bilayered specimens (core-to-porcelain thickness: 0.8mm/1.5mm). Biaxial flexural strengths of the specimens with the porcelain layer in tension were tested based on the piston-on-three-ball method (ISO 6872:2008). The data were statistically analyzed using Weibull distribution and Fisher's exact test. RESULTS Tensile stresses were observed in the entire porcelain layer while compressive stress at the surface of the Ce-TZP/A layer shifted to tensile stress at the interface between the materials. The cases of small CTE mismatches between the materials showed high Weibull characteristic strengths at the internal and external surfaces of the specimens, except the VM9 group (CTE: 9.0-9.2ppm/°C). The maximum tensile stress was observed on the surface of the porcelain layer, where cracks originated and continuously propagated into the Ce-TZP layer. The Ce-TZP/A fractured into two pieces for large CTE mismatches between the materials, resulting in significantly lower flexural strengths than those fracturing into three pieces for small CTE mismatches. SIGNIFICANCE Flexural strengths and fracture behaviors of bilayered porcelain-Ce-TZP/A disks were influenced by the CTE mismatches, and a small CTE mismatch between the materials was preferred when using a slow-cooling protocol.
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Affiliation(s)
- Tomofumi Sawada
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany; Department of Biomedical Engineering, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba-cho, Shiwa-gun, Iwate 028-3694, Japan.
| | - Verena Wagner
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Christine Schille
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Sebastian Spintzyk
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Ernst Schweizer
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Jürgen Geis-Gerstorfer
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
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Nassary Zadeh P, Lümkemann N, Sener B, Eichberger M, Stawarczyk B. Flexural strength, fracture toughness, and translucency of cubic/tetragonal zirconia materials. J Prosthet Dent 2018; 120:948-954. [PMID: 29807742 DOI: 10.1016/j.prosdent.2017.12.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 12/20/2017] [Accepted: 12/20/2017] [Indexed: 11/28/2022]
Abstract
STATEMENT OF PROBLEM The development of zirconia materials with optimized properties has been rapid, and studies comparing the mechanical and optical properties of recently introduced zirconia with lithium disilicate materials are limited. PURPOSE The purpose of this in vitro study was to compare the mechanical and optical properties of cubic/tetragonal zirconia materials with those of a lithium disilicate ceramic. MATERIAL AND METHODS Specimens were fabricated from 6 different noncolored zirconia materials: Ceramill Zolid FX (CZ), CopraSmile (CS), DD cubeX2 (DD), NOVAZIR MaxT (NZ), priti multidisc ZrO₂ (PD), and StarCeram Z-Smile (SC), and 1 lithium disilicate ceramic as a control, IPS e.max Press LT A2 (CG). Four-point flexural strength (N=105/n=15) and fracture toughness using the single-edge V-notched beam (N=105/n=15) were examined according to International Organization for Standardization standard 6872:2015. Translucency (N=70/n=10) was evaluated with an ultraviolet spectrophotometer. Grain size (N=6/n=1) of zirconia was investigated by using scanning electron microscopy. Data were analyzed using the Kolmogorov-Smirnov test, multivariate analysis, 1-way analysis of variance, followed by the post hoc Scheffé test and Kruskal-Wallis and Mann-Whitney U tests, and Weibull analysis, using the maximum likelihood estimation method at 95% confidence level (α=.05). RESULTS Zirconia materials showed higher mechanical and lower optical properties than CG (P<.001). No differences were observed among the zirconia materials with respect to flexural strength (P=.259) or fracture toughness (P=.408). CG and CS showed significantly higher Weibull modulus than SC and PD. The lowest translucency values were measured for NZ and SC, followed by CS, DD, and PD (P<.001). CZ showed the highest translucency values (P<.001). The lowest grain sizes were found for NZ, DD, and SC; the largest were shown for CS (P<.001). CONCLUSIONS Cubic/tetragonal zirconia showed better mechanical properties than lithium disilicate ceramic. However, the optical properties and the reliability of zirconia are lower than those of lithium disilicate ceramic.
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Affiliation(s)
- Parissa Nassary Zadeh
- Assistant Professor, Department of Prosthetic Dentistry, Hospital of the University of Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Nina Lümkemann
- Materials Engineer, Department of Prosthetic Dentistry, Hospital of the University of Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Beatrice Sener
- Medical Technologist Assistant, Clinic for Preventive Dentistry, Periodontics and Cardiology, University of Zurich, Zurich, Switzerland
| | - Marlis Eichberger
- Certified Dental Technician, Department of Prosthetic Dentistry, Hospital of the University of Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Bogna Stawarczyk
- Head of Dental Materials Unit, Department of Prosthetic Dentistry, Hospital of the University of Munich, Ludwig Maximilian University of Munich, Munich, Germany.
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Sawada T, Schille C, Zöldföldi J, Schweizer E, Geis-Gerstorfer J, Spintzyk S. Influence of a surface conditioner to pre-sintered zirconia on the biaxial flexural strength and phase transformation. Dent Mater 2018; 34:486-493. [PMID: 29301652 DOI: 10.1016/j.dental.2017.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/19/2017] [Accepted: 12/15/2017] [Indexed: 10/18/2022]
Abstract
OBJECTIVES To assess the influence of a surface conditioner applied to pre-sintered yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on the biaxial flexural strength and phase transformation. METHODS Conditioner-coated specimens (12mm diameter×0.8mm thickness) were prepared by application of a slurry conditioner using a brush on pre-sintered Y-TZP discs, followed by sandblasting with 50-μm Al2O3 after sintering (C-SB) or no further treatment (C-NT). The remaining conditioner-free specimens were subjected to sandblasting before sintering (NC-SB) or were maintained without treatment (NC-NT). Surface roughness measurements and scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray spectroscopy (SEM-EDX) were performed for surface characterizations. The phase transformation of Y-TZP was identified by X-ray diffraction (XRD), and the biaxial flexural strength was measured using the piston-on-three-ball test according to ISO 6872:2015. The data were analyzed using nonparametric Kruskal-Wallis tests and Weibull distributions with the maximum likelihood estimation. RESULTS Sandblasting resulted in significantly rougher surfaces, irrespective of conditioner application. Conditioner layers were observed on surfaces in the C-NT and C-SB specimens. Monoclinic contents were present in a very small amount in the C-SB specimens. Both median biaxial flexural and characteristic strengths of all specimens exceeded ISO 6872:2015 requirements (Class 5: >800MPa), except the NC-SB specimens which showed significantly the lowest strength (p<0.001). Although no statistical difference was observed in Weibull modulus among the specimens (p=0.598), the NC-SB specimens showed the highest. SIGNIFICANCE Surface conditioner application does not affect the biaxial flexural strength and phase stability of Y-TZP and can be considered practical for clinical use.
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Affiliation(s)
- Tomofumi Sawada
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Christine Schille
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Judit Zöldföldi
- Institute for Materials Science, University of Stuttgart, Pfaffenwaldring 2b, 70569 Stuttgart, Germany.
| | - Ernst Schweizer
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Jürgen Geis-Gerstorfer
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
| | - Sebastian Spintzyk
- Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
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Two Independent Prospectively Planned Blinded Weibull Statistical Analyses of Flexural Strength Data of Zirconia Materials. MATERIALS 2016; 9:ma9070512. [PMID: 28773635 PMCID: PMC5456914 DOI: 10.3390/ma9070512] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 05/17/2016] [Accepted: 06/20/2016] [Indexed: 11/16/2022]
Abstract
Zirconia as a restoration dental material are gaining attention because of their high mechanical properties and good biocompatibility. Therefore, investigation of the flexural strength of zirconia is of great interest. For this purpose, Weibull statistics for description of the material reliability are frequently used. The aim of this work was to present a blinded data set to two independent statisticians for two parallel statistical analyses in order to find an optimal statistical approach for analysis of in-vitro measured flexural strength data of zirconia materials. A prospectively planned independent blinded statistical analysis implementing three quality control actions “blinded data set”, “independent statistical analyses” and “parallel manuscript writing” was designed. Statistical analysis paths taken by both biostatisticians differed. They arrived at complementary results. The major difference was caused by two alternative distributional assumptions (Weibull/Normal) and alternative fitting methods (LS/ML). The parallel statistical analysis and manuscript writing approach on a blinded data set greatly supported our choice of statistical methods for analysis of flexural strength results of zirconia materials.
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An approach to scaling size effect on strength of quasi-brittle biomedical materials. J Mech Behav Biomed Mater 2016; 62:428-432. [PMID: 27266476 DOI: 10.1016/j.jmbbm.2016.05.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Revised: 05/13/2016] [Accepted: 05/18/2016] [Indexed: 11/20/2022]
Abstract
Two-parameter Weibull statistics is commonly used for characterizing and modeling strength distribution of biomedical materials and its size dependence. The calibrated scale parameter and shape factor are usually sensitive to specimen size. Since Weibull statistics is subject to the weakest link postulate, this work proposed to directly resort to the weakest-link formulation for the cumulative failure probability to characterize size effect on strength distribution of quasi-brittle biomedical materials. As a preliminary examination, the approach was assessed by two sets of published strength data. It shows that the resultant expression for the cumulative probability follows either Weibull distribution or other type of distributions. The calibrated model parameters are independent of specimen size, so they can be used to transfer strength distribution from one set of specimens to another set of specimens with geometrical similarity under same loading mode. These initial results motivate a more comprehensive validation of the proposed approach to proceed via a larger set of case studies covering different quasi-brittle biomedical materials over a wider range of size variation.
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Schatz C, Strickstrock M, Roos M, Edelhoff D, Eichberger M, Zylla IM, Stawarczyk B. Influence of Specimen Preparation and Test Methods on the Flexural Strength Results of Monolithic Zirconia Materials. MATERIALS 2016; 9:ma9030180. [PMID: 28773307 PMCID: PMC5456702 DOI: 10.3390/ma9030180] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 02/09/2016] [Accepted: 03/02/2016] [Indexed: 11/16/2022]
Abstract
The aim of this work was to evaluate the influence of specimen preparation and test method on the flexural strength results of monolithic zirconia. Different monolithic zirconia materials (Ceramill Zolid (Amann Girrbach, Koblach, Austria), Zenostar ZrTranslucent (Wieland Dental, Pforzheim, Germany), and DD Bio zx2 (Dental Direkt, Spenge, Germany)) were tested with three different methods: 3-point, 4-point, and biaxial flexural strength. Additionally, different specimen preparation methods were applied: either dry polishing before sintering or wet polishing after sintering. Each subgroup included 40 specimens. The surface roughness was assessed using scanning electron microscopy (SEM) and a profilometer whereas monoclinic phase transformation was investigated with X-ray diffraction. The data were analyzed using a three-way Analysis of Variance (ANOVA) with respect to the three factors: zirconia, specimen preparation, and test method. One-way ANOVA was conducted for the test method and zirconia factors within the combination of two other factors. A 2-parameter Weibull distribution assumption was applied to analyze the reliability under different testing conditions. In general, values measured using the 4-point test method presented the lowest flexural strength values. The flexural strength findings can be grouped in the following order: 4-point < 3-point < biaxial. Specimens prepared after sintering showed significantly higher flexural strength values than prepared before sintering. The Weibull moduli ranged from 5.1 to 16.5. Specimens polished before sintering showed higher surface roughness values than specimens polished after sintering. In contrast, no strong impact of the polishing procedures on the monoclinic surface layer was observed. No impact of zirconia material on flexural strength was found. The test method and the preparation method significantly influenced the flexural strength values.
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Affiliation(s)
- Christine Schatz
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, Munich 80336, Germany.
| | - Monika Strickstrock
- Faculty of Engineering and Computer Science, Material Science and Analysis, University of Applied Sciences, Hochschule Osnabrück, Albrechtstrasse 30, Osnabrück 49076, Germany.
| | - Malgorzata Roos
- Department of Biostatistics, Epidemiology Biostatistics and Prevention Institute, University of Zurich, Hirschengraben 84, Zurich 8001, Switzerland.
| | - Daniel Edelhoff
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, Munich 80336, Germany.
| | - Marlis Eichberger
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, Munich 80336, Germany.
| | - Isabella-Maria Zylla
- Faculty of Engineering and Computer Science, Material Science and Analysis, University of Applied Sciences, Hochschule Osnabrück, Albrechtstrasse 30, Osnabrück 49076, Germany.
| | - Bogna Stawarczyk
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University Munich, Goethestrasse 70, Munich 80336, Germany.
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Evaluation of mechanical and optical behavior of current esthetic dental restorative CAD/CAM composites. J Mech Behav Biomed Mater 2016; 55:1-11. [DOI: 10.1016/j.jmbbm.2015.10.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 10/06/2015] [Accepted: 10/12/2015] [Indexed: 11/22/2022]
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Stawarczyk B, Frevert K, Ender A, Roos M, Sener B, Wimmer T. Comparison of four monolithic zirconia materials with conventional ones: Contrast ratio, grain size, four-point flexural strength and two-body wear. J Mech Behav Biomed Mater 2015; 59:128-138. [PMID: 26751707 DOI: 10.1016/j.jmbbm.2015.11.040] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 11/17/2015] [Accepted: 11/23/2015] [Indexed: 12/28/2022]
Abstract
OBJECTIVES To test the mechanical and optical properties of monolithic zirconia in comparison to conventional zirconia. MATERIALS AND METHODS Specimens were prepared from: monolithic zirconia: Zenostar (ZS), DD Bio ZX(2) hochtransluzent (DD), Ceramill Zolid (CZ), InCoris TZI (IC) and a conventional zirconia Ceramill ZI (CZI). Contrast ratio (N=75/n=15) was measured according to ISO 2471:2008. Grain sizes (N=75/n=15) were investigated with scanning electron microscope. Four-point flexural strength (N=225/n=15/zirconia and aging regime) was measured initially, after aging in autoclave or chewing simulator (ISO 13356:2008). Two-body wear of polished and glazed/veneered specimens (N=108/n=12) was analyzed in a chewing simulator using human teeth as antagonists. Data were analyzed using 2-/1-way ANOVA with post-hoc Scheffé, Kruskal-Wallis-H, Mann-Whitney-U, Spearman-Rho, Weibull statistics and linear mixed models (p<0.05). RESULTS The lowest contrast ratio values were found for ZS and IC and CZ. IC showed the largest grain size followed by DD and CZI. The smallest grain size was observed for ZS followed by CZ. There was no correlation between grain size and contrast ratio. The aging regime showed no impact on flexural strength. All non-aged and autoclave-aged specimens showed lower flexural strengths than the control group CZI. Within groups aged in chewing simulator, ZS showed significantly lower flexural strength than CZI. CZI showed higher material and antagonist wear than monolithic polished and glazed groups. Glazed specimens showed higher material and antagonist loss compared to polished ones. There was no correlation between roughness and wear. CONCLUSIONS Monolithic zirconia showed higher optical, but lower mechanical properties than conventional zirconia.
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Affiliation(s)
- Bogna Stawarczyk
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University of Munich, Germany.
| | - Kathrin Frevert
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University of Munich, Germany
| | - Andreas Ender
- Clinic of Preventive Dentistry, Periodontology and Cariology, Center of Dental Medicine, University of Zurich, Switzerland
| | - Malgorzata Roos
- Department of Biostatistics, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Switzerland
| | - Beatrice Sener
- Clinic of Preventive Dentistry, Periodontology and Cariology, Center of Dental Medicine, University of Zurich, Switzerland
| | - Timea Wimmer
- Department of Prosthodontics, Dental School, Ludwig-Maximilians-University of Munich, Germany
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Brouers F. The Burr XII Distribution Family and the Maximum Entropy Principle: Power-Law Phenomena Are Not Necessarily “Nonextensive”. ACTA ACUST UNITED AC 2015. [DOI: 10.4236/ojs.2015.57073] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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