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Fracture behaviour of zirconia FPDs substructures: fractographic analysis of zirconia
Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap. Umeå universitet, Medicinska fakulteten, Institutionen för odontologi. (Biomaterial)
Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap. (Biomaterial)
2010 (Engelska)Ingår i: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 37, nr 4, s. 292-299Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

 The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three-unit heat-treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) after loaded to fracture. Four three-unit HIPed Y-TZP-based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three-unit heat-treated machined HIPed Y-TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove.

Ort, förlag, år, upplaga, sidor
Blackwell Publishing Ltd , 2010. Vol. 37, nr 4, s. 292-299
Nyckelord [en]
ceramics, fixed partial denture, fractographic analysis, machined surface, Y-TZP, zirconia
Nationell ämneskategori
Odontologi
Forskningsämne
odontologi
Identifikatorer
URN: urn:nbn:se:umu:diva-31637DOI: 10.1111/j.1365-2842.2009.02057.xISI: 000275206600009PubMedID: 20085616Scopus ID: 2-s2.0-77954353775OAI: oai:DiVA.org:umu-31637DiVA, id: diva2:293637
Tillgänglig från: 2010-02-12 Skapad: 2010-02-12 Senast uppdaterad: 2024-01-17Bibliografiskt granskad
Ingår i avhandling
1. On dental ceramics and their fracture: a laboratory and numerical study
Öppna denna publikation i ny flik eller fönster >>On dental ceramics and their fracture: a laboratory and numerical study
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Background Surface treatments and irregularities in the surfaces may affect the fracture of ceramics. The effects of various treatments on the surface texture of different types of ceramic cores/substructures was therefore qualitatively, quantitatively and numerically evaluated. Since fractures in ceramics are not fully understood, the fracture behavior in dental ceramic core/substructures was also studied using both established laboratory methods and newly developed numerical methods.

Methods The surfaces of dental ceramic cores/substructures were studied qualitatively by means of a fluorescence penetrant method and scanning electron microscopy, quantitatively evaluated using a profilometer and also numerical simulation. In order to study fracture in zirconia-based fixed partial denture (FPD) frameworks, fractographic analysis in combination with fracture tests and newly developed two-dimensional (2D) and three-dimensional (3D) numerical modeling methods were used. In the numerical modeling methods, the heterogeneity within the materials was described by means of the Weibull distribution law. The Mohr–Coulomb failure criterion with tensile strength cut-off was used to judge whether the material was in an elastic or failed state.

Results Manual grinding/polishing could smooth the surfaces on some of the types of dental ceramic cores/substructures studied. Using the fluorescence penetrant method, no cracks/flaws apart from milling grooves could be seen on the surfaces of machined zirconia-based frameworks. Numerical simulations demonstrated that surface grooves affect the fracture of the ceramic bars and the deeper the groove, the sooner the bar fractured. In the laboratory tests the fracture mechanism in the FPD frameworks was identified as tensile failure and irregularities on the ceramic surfaces could act as fracture initiation sites. The numerical modeling codes allowed a better understanding of the fracture mechanism than the laboratory tests; the stress distribution and the fracture process could be reproduced using the mathematical methods of mechanics. Furthermore, a strong correlation was found between the numerical and the laboratory results.

Conclusion Based on the findings in the current thesis, smooth surfaces in areas of concentrated tensile stress would be preferable regarding the survival of ceramic restorations, however, the surfaces of only some of the ceramic cores/substructures could be significantly affected by manual polishing. The newly developed 3D method clearly showed the stress distribution and the fracture process in ceramic FPD frameworks, step by step, and seems to be an appropriate tool for use in the prediction of the fracture process in ceramic FPD frameworks.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå universitet, 2010. s. 53
Serie
Umeå University odontological dissertations, ISSN 0345-7532 ; 113
Nyckelord
Dental ceramics, Finite element analysis, Fixed partial denture, Fracture, Numerical modeling, Surface treatment
Nationell ämneskategori
Biomaterialvetenskap
Forskningsämne
odontologi
Identifikatorer
urn:nbn:se:umu:diva-36590 (URN)978-91-7459-037-1 (ISBN)
Disputation
2010-10-29, Sal 260, byggnad 3A, Norrlands universitetssjukhus, Umeå, 13:00 (Svenska)
Opponent
Handledare
Tillgänglig från: 2010-10-08 Skapad: 2010-10-05 Senast uppdaterad: 2018-06-08Bibliografiskt granskad

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Kou, WenSjögren, Göran

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