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Surface roughness of five different dental ceramic core materials after grinding and polishing
Umeå University, Faculty of Medicine, Department of Odontology, Dental Materials Science.
Umeå University, Faculty of Medicine, Department of Odontology, Prosthetic Dentistry.
Umeå University, Faculty of Medicine, Department of Odontology, Dental Materials Science.
2006 (English)In: Journal of Oral Rehabilitation, ISSN 0305-182X, E-ISSN 1365-2842, Vol. 33, no 2, 117-124 p.Article in journal (Refereed) Published
Abstract [en]

In clinical practice, core materials can be exposed after adjustments are made to previously-luted all-ceramic restorations. The purpose of this study was to evaluate the surface roughness of five different dental ceramic core materials after grinding and polishing. Five different ceramic core materials, Vita In-Ceram Alumina, Vita In-Ceram Zirconia, IPS Empress 2, Procera AllCeram, and Denzir were evaluated. Vita Mark II was used as a reference material. The surface roughness, Ra value (mum), was registered using a profilometer. The measurements were made before and after grinding with diamond rotary cutting instruments and after polishing with the Sof-Lex system. The surface of representative specimens was evaluated qualitatively using scanning electron microscopy (SEM). Results were statistically analysed using analysis of variance (anova) supplemented with Scheffe's and Bonferroni multiple-comparison tests. Before grinding, Procera AllCeram and Denzir had the smoothest surfaces, while IPS Empress 2 had the coarsest. After grinding, all materials except IPS Empress 2 became coarser. Polishing with Sof-Lex provided no significant (P > 0.05) differences between Denzir, Vita Mark II and IPS Empress 2 or between Procera AllCeram and In-Ceram Zirconia. There were no significant differences (P > 0.05) either between the ground and the polished Procera AllCeram or In-Ceram Alumina specimens. Polishing of Denzir, IPS Empress 2 and In-Ceram Zirconia made the surfaces smoother compared with the state after grinding, whereas the polishing effect on Procera AllCeram and In-Ceram Alumina was ineffective. The findings of the SEM evaluation were consistent with the profilometer readings.

Place, publisher, year, edition, pages
2006. Vol. 33, no 2, 117-124 p.
Keyword [en]
all-ceramic crowns, alumina, dental ceramics, dental polishing, finishing, lithium disilicate, Y-TZP, zirconia
National Category
URN: urn:nbn:se:umu:diva-12427DOI: 10.1111/j.1365-2842.2006.01546.xPubMedID: 16457671OAI: diva2:152098
Available from: 2007-12-13 Created: 2007-12-13 Last updated: 2010-10-08Bibliographically approved
In thesis
1. On dental ceramics and their fracture: a laboratory and numerical study
Open this publication in new window or tab >>On dental ceramics and their fracture: a laboratory and numerical study
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2010. 53 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 113
Dental ceramics, Finite element analysis, Fixed partial denture, Fracture, Numerical modeling, Surface treatment
National Category
Biomaterials Science
Research subject
urn:nbn:se:umu:diva-36590 (URN)978-91-7459-037-1 (ISBN)
Public defence
2010-10-29, Sal 260, byggnad 3A, Norrlands universitetssjukhus, Umeå, 13:00 (Swedish)
Available from: 2010-10-08 Created: 2010-10-05 Last updated: 2011-10-11Bibliographically approved

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