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Key WB, Jodha KS, Kaur N, Marocho SMS, Mecholsky JJ, Griggs JA. Fracture toughness and fractal analysis of ceramic benchmark materials. J Mater Sci 2022; 57:10051-10058. [PMID: 37711847 PMCID: PMC10501202 DOI: 10.1007/s10853-022-07308-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/05/2022] [Indexed: 09/16/2023]
Abstract
Previous studies have reported various methods of measuring the fracture toughness of brittle ceramics. The purpose of the present research was to use a new method of fractal dimension measurement on benchmark materials (silica glass, Viosil SX, Shin-Etsu, n = 13, and silicon nitride standard reference material, SRM2100, NIST, n = 10), to compare the fracture toughness calculated using different methods, and to study the effect of noise filtering on the fractal dimension and fracture surface roughness. Fracture toughness was determined using surface crack in flexure method according to ASTM C1421 and fractal analysis method. Fractal dimension was determined using the Minkowski Cover algorithm on atomic force microscope scans of epoxy replicas of fracture surfaces. The mean ± standard deviation of fracture toughness using surface crack in flexure method and fractals method were 0.97 ± 0.18 MPa·m1/2 and 1.03 ± 0.07 MPa·m1/2 for silica glass and 4.62 ± 0.14 MPa·m1/2 and 2.54 ± 0.07 MPa·m1/2 for silicon nitride, respectively. The mean ± standard deviation of fractal dimension was 2.17 ± 0.03 for silica glass and 2.13 ± 0.01 for silicon nitride. The mean ten-point roughness (Rz) before and after noise filtering was 89 ± 102 nm and 87 ± 101 nm for silica glass and 355 ± 132 nm and 357 ± 134 nm for silicon nitride, respectively. Noise filtering had no significance on the fracture surface roughness of the two materials. The newly developed fractal analysis method can be used to predict the baseline fracture toughness of specimens with unknown failure stress.
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Affiliation(s)
- W B Key
- Department of Biomedical Materials Science, University of Mississippi Medical Center, Room D528, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - K S Jodha
- Department of Biomedical Materials Science, University of Mississippi Medical Center, Room D528, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - N Kaur
- Department of Biomedical Materials Science, University of Mississippi Medical Center, Room D528, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - S M Salazar Marocho
- Department of Biomedical Materials Science, University of Mississippi Medical Center, Room D528, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - J J Mecholsky
- Department of Materials Science and Engineering, University of Florida, Gainesville, USA
| | - J A Griggs
- Department of Biomedical Materials Science, University of Mississippi Medical Center, Room D528, 2500 North State Street, Jackson, MS 39216-4505, USA
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Mecholsky JJ, Barrett AA, Jones CT, Pace KM, Nair UP. Fractographic analysis of separated endodontic file designs. J Mater Sci Mater Med 2020; 31:104. [PMID: 33140130 DOI: 10.1007/s10856-020-06432-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 09/24/2020] [Indexed: 06/11/2023]
Abstract
Endodontic rotary files are cutting instruments used to perform root canal procedures within a tooth interior. Focusing on quantitative fractographic analysis increases necessary, clinical performance understanding of file separation failure. This research employed controlled, dynamic testing to failure of commercial rotary files, analyzing the fractographic, forensic characteristics in relation to Weibull reliability determination, considering: (1) design analysis; (2) stress concentrations; (3) times to failure; (4) number of cycles to failure (NCF). Ex vivo testing included three file designs, each having constant tip size (0.035 mm), taper (0.06 mm/mm), and length (25 mm). Files were individually tested using an electric, torque-controlled handpiece, rotating within a standardized, simulated canal until fracture separation occurred. Fractographic analysis, including critical measurements, was conducted using the scanning electron microscope (SEM) (PhenomProX, PhenomWorld, NL). Weibull statistical analysis established reliability factors per design group. Fractographic analysis identified separation fractures, processing inclusions, flexural-fatigue striations, and stress concentrations at flute pitches. Calculated NCF median values (1277-EE; 899-VB; 713-PI) demonstrated significant statistical differences among groups (p < 0.001). Separated apical fragments yielded statistically significant differences (p ≤ 0.05) for varying file design groups. Weibull moduli among groups were statistically equivalent. Fractographic analysis exposed a presence of multiple failure factors in addition to defect distribution, governing cyclic fatigue failure originating at stress concentration points irrespective of file design. Fractographic analysis indicated that a change in file design, specifically at the working edges, in addition to improved surface finish, has the potential of reducing failures by lowering points of stress concentration and reducing fracture initiating surface cracks.
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Affiliation(s)
- J J Mecholsky
- Department of Materials Science & Engineering, Center for Dental Biomaterials, College of Engineering, University of Florida, Gainesville, FL, 32611-6400, USA.
- Center for Dental Biomaterials, Department of Materials Science & Engineering, College of Engineering, University of Florida, Gainesville, FL, 32611-6400, USA.
| | - A A Barrett
- Center for Dental Biomaterials, Department of Materials Science & Engineering, College of Engineering, University of Florida, Gainesville, FL, 32611-6400, USA
| | - C T Jones
- Department of Endodontics, College of Dentistry, University of Florida, Gainesville, FL, 32611-6400, USA
- Practice Limited to Endodontics, Melbourne, FL, USA
| | - K M Pace
- Department of Materials Science & Engineering, College of Engineering, University of Florida, Gainesville, FL, 32611-6400, USA
- Alight Solutions, Dallas, TX, USA
| | - U P Nair
- Practice Limited to Endodontics, Dallas, TX, USA
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Esquivel-Upshaw JF, Mecholsky JJ, Clark AE, Jenkins R, Hsu SM, Neal D, Ren F. Factors influencing the survival of implant-supported ceramic-ceramic prostheses: A randomized, controlled clinical trial. J Dent 2020; 103S:100017. [PMID: 34059304 PMCID: PMC9993352 DOI: 10.1016/j.jjodo.2020.100017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 02/29/2020] [Accepted: 04/08/2020] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVE The goals of this research are: (1) to determine the clinical survival of ceramic-ceramic 3-unit implant supported fixed dental prostheses (FDPs) compared with control metal-ceramic and; (2) to analyze the effects of design parameters such as connector height, radius of curvature of gingival embrasure, and occlusal veneer thickness. MATERIALS AND METHODS This randomized, controlled clinical trial enrolled 96 participants with 129 3-unit implant-supported FDPs. Participants were randomized to receive different design combinations to include FDP material, thickness of occlusal veneer ceramic, radius of curvature of gingival embrasure and connector height. Participants were recalled for 6 months, 1year and yearly thereafter for the next 5 years. FDPs were examined for evidence of fracture and radiographs were made to assess viability of implants. Fractographic analyses and Kaplan Meier survival analysis was used to analyze the data. RESULTS 27 FDPs, representing 21%, exhibited chipping fractures of the veneer during the 5-year observation period. There was no statistically significant effect of type of material, veneer thickness, radius of curvature of gingival embrasure and connector height on occurrence of fracture. Fractographic and occlusal analyses reveal that fractures originated from the occlusal surface and that occlusion was the most important factor in determining survival. Stresses calculated at failure demonstrated lower values compared with in vitro data. CONCLUSION Implant-supported ceramic-ceramic prosthesis is a viable alternative to metal-ceramic. Survival analysis for both materials were comparable and design parameters employed in this study did not affect survival as long as zirconia was used as the core material.
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Affiliation(s)
- J F Esquivel-Upshaw
- Division of Prosthodontics, Restorative Dental Sciences, University of Florida College of Dentistry, Gainesville, FL, United States.
| | - J J Mecholsky
- Department of Materials Science and Engineering, University of Florida Herbert Wertheim College of Engineering, Gainesville, FL, United States
| | - A E Clark
- Division of Prosthodontics, Restorative Dental Sciences, University of Florida College of Dentistry, Gainesville, FL, United States
| | - R Jenkins
- Dental Clinical Research Unit, University of Florida College of Dentistry Office of Research, Gainesville, FL, United States
| | - S M Hsu
- Division of Prosthodontics, Restorative Dental Sciences, University of Florida College of Dentistry, Gainesville, FL, United States
| | - D Neal
- Department of Neurosurgery, University of Florida College of Medicine, Gainesville, FL, United States
| | - F Ren
- Department of Chemical Engineering, University of Florida Herbert Wertheim College of Engineering, Gainesville, FL, United States
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Abstract
We suggest that the apparent interfacial fracture toughness (K(A)) may be estimated by fracture mechanics and fractography. This study tested the hypothesis that the K(A) of the adhesion zone of resin/ceramic systems is affected by the ceramic microstructure. Lithia disilicate-based (Empress2-E2) and leucite-based (Empress-E1) ceramics were surface-treated with hydrofluoric acid (HF) and/or silane (S), followed by an adhesive resin. Microtensile test specimens (n = 30; area of 1 +/- 0.01 mm(2)) were indented (9.8 N) at the interface and loaded to failure in tension. We used tensile strength (sigma) and the critical crack size (c) to calculate K(A) (K(A) = Ysigmac(1/2)) (Y = 1.65). ANOVA and Weibull analyses were used for statistical analyses. Mean K(A) (MPa.m(1/2)) values were: (E1HF) 0.26 +/- 0.06; (E1S) 0.23 +/- 0.06; (E1HFS) 0.30 +/- 0.06; (E2HF) 0.31 +/- 0.06; (E2S) 0.13 +/- 0.05; and (E2HFS) 0.41 +/- 0.07. All fractures originated from indentation sites. Estimation of interfacial toughness was feasible by fracture mechanics and fractography. The K(A) for the systems tested was affected by the ceramic microstructure and surface treatment.
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Affiliation(s)
- A Della Bona
- School of Dentistry, The University of Passo Fundo, PO Box 611, Passo Fundo, RS, 99001-970, Brazil.
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Abstract
Ceramic systems have limited long-term fracture resistance, especially when they are used in posterior areas or for fixed partial dentures. The objective of this study was to determine the site of crack initiation and the causes of fracture of clinically failed ceramic fixed partial dentures. Six Empress 2 lithia-disilicate (Li(2)O x 2SiO(2))-based veneered bridges and 7 experimental lithia-disilicate-based non-veneered ceramic bridges were retrieved and analyzed. Fractography and fracture mechanics methods were used to estimate the stresses at failure in 6 bridges (50%) whose fracture initiated from the occlusal surface of the connectors. Fracture of 1 non-veneered bridge (8%) initiated within the gingival surface of the connector. Three veneered bridges fractured within the veneer layers. Failure stresses of the all-core fixed partial dentures ranged from 107 to 161 MPa. Failure stresses of the veneered fixed partial dentures ranged from 19 to 68 MPa. We conclude that fracture initiation sites are controlled primarily by contact damage.
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Affiliation(s)
- B Taskonak
- Department of Restorative Dentistry, Division of Dental Biomaterials, Indiana University, School of Dentistry, 1121 W. Michigan St., Indianapolis, IN 46202, USA.
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Clupper DC, Mecholsky JJ, LaTorre GP, Greenspan DC. Sintering temperature effects on the in vitro bioactive response of tape cast and sintered bioactive glass-ceramic in Tris buffer. J Biomed Mater Res 2001; 57:532-40. [PMID: 11553883 DOI: 10.1002/1097-4636(20011215)57:4<532::aid-jbm1199>3.0.co;2-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Tape casting procedures were used to form thin polymeric sheets (100 microm thickness) loaded with bioactive glass particulate. Blanks were punched from the sheets, stacked, laminated, and heated in air to 500 degrees C to remove the organic phase. The resulting bioactive glass discs were sintered at 800 degrees C, 900 degrees C, or 1000 degrees C. Because the material is built up in layers and can be machined in the green state, such a processing technique can be used to form complex-shaped materials. The in vitro bioactivity of the tape cast sintered (TCS) bioactive glass-ceramic discs was then assessed in Tris buffer. The sample surface area to volume buffer (SA/V) ratio was approximately 0.1 cm(2)/mL. Tape cast bioactive glass-ceramic sintered at 900 degrees C and 1000 degrees C formed crystalline hydroxyapatite layers after 24 h in Tris buffer as indicated by FTIR, SEM, and EDS analysis. Decreasing the SA/V ratio to 0.013 cm(2)/mL allowed for the formation of crystalline hydroxyapatite layers on the surface of 800C TCS bioactive glass-ceramic. Given the dependence of the bioactive response as a function of the processing schedule and SA/V ratio, it may be possible to tailor the response to that desired in vivo or in vitro for tissue engineering studies. Biaxial flexural strength of TCS bioactive glass-ceramic increased with increasing sintering temperature. Strength of samples sintered at 1000 degrees C for 3 h increased from 87 to 120 MPa after 2 weeks' immersion in Tris buffer.
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Affiliation(s)
- D C Clupper
- University of Florida, Department of Materials Science and Engineering, Gainesville, Florida, USA.
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Abstract
Fractography is the analysis of fracture surfaces. Here, it refers to quantitative fracture surface analysis (FSA) in the context of applying the principles of fracture mechanics to the topography observed on the fracture surface of brittle materials. The application of FSA is based on the principle that encoded on the fracture surface of brittle materials is the entire history of the fracture process. It is our task to develop the skills and knowledge to decode this information. There are several motivating factors for applying our knowledge of FSA. The first and foremost is that there is specific, quantitative information to be obtained from the fracture surface. This information includes the identification of the size and location of the fracture initiating crack or defect, the stress state at failure, the existence, or not, of local or global residual stress, the existence, or not, of stress corrosion and a knowledge of local processing anomalies which affect the fracture process. The second motivating factor is that the information is free. Once a material is tested to failure, the encoded information becomes available. If we decide to observe the features produced during fracture then we are rewarded with much information. If we decide to ignore the fracture surface, then we are left to guess and/or reason as to the cause of the failure without the benefit of all of the possible information available. This paper addresses the application of quantitative fracture surface analysis to basic research, material and product development, and "trouble-shooting" of in-service failures. First, the basic principles involved will be presented. Next, the methodology necessary to apply the principles will be presented. Finally, a summary of the presentation will be made showing the applicability to design and reliability.
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Affiliation(s)
- J J Mecholsky
- Department of Materials Science and Engineering, University of Florida, Gainesville, USA
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Abstract
The principles of linear elastic fracture mechanics (LEFM) were developed in the 1950s by George Irwin (1957). This work was based on previous investigations of Griffith (1920) and Orowan (1944). Irwin (1957) demonstrated that a crack shape in a particular location with respect to the loading geometry had a stress intensity associated with it. He also demonstrated the equivalence between the stress intensity concept and the familiar Griffith criterion of failure. More importantly, he described the systematic and controlled evaluation of the toughness of a material. Toughness is defined as the resistance of a material to rapid crack propagation and can be characterized by one parameter, Kic. In contrast, the strength of a material is dependent on the size of the initiating crack present in that particular sample or component. The fracture toughness of a material is generally independent of the size of the initiating crack. The strength of any product is limited by the size of the cracks or defects during processing, production and handling. Thus, the application of fracture mechanics principles to dental biomaterials is invaluable in new material development, production control and failure analysis. This paper describes the most useful equations of fracture mechanics to be used in the failure analysis of dental biomaterials.
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Affiliation(s)
- J J Mecholsky
- Department of Materials Science and Engineering, University of Florida, Gainesville, USA
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