Experimental and Finite Element Study of Residual Thermal Stresses in Veneered Y-TZP Structures

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Departmental Papers (Dental)
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Porcelain-veneered zirconia
Residual thermal stresses
Cooling rates
Specimen geometries
Vickers indentation method
Finite element analysis
Dentistry
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Tanaka, Carina B.
Harisha, Hossam
Baldassarri, Marta
Wolff, Mark S.
Tong, Hui
Meira, Josete B.C.
Zhang, Yu
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Abstract

The main complications of zirconia-based laminated systems are chipping and delamination of veneering porcelain, which has been found to be directly associated with the development of residual thermal stresses in the porcelain layer. This study investigates the effects of cooling rate and specimen geometry on the residual stress states in porcelain-veneered zirconia structures. Bilayers of three different shapes (bars, semi-cylindrical shells, and arch-cubic structures) with 1.5 mm and 0.7 mm thickness of dentin porcelain and zirconia framework, respectively, were subjected to two cooling protocols: slow cooling (SC) at 32 °C/min and extremely-slow cooling (XSC) at 2 °C/min. The residual thermal stresses were determined using the Vickers indentation method and validated by finite element analysis. The residual stress profiles were similar among geometries in the same cooling protocol. XSC groups presented significantly higher tensile stresses (p = 0.000), especially for curved interfaces. XSC is a time-consuming process that showed no beneficial effect regarding residual stresses compared to the manufacturer recommended slow cooling rate.

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2016-05-15
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Journal of the American Dental Association
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At the time of publication, author Mark Wolff was affiliated with New York University College of Dentistry. Currently, (s)he is a faculty member at the School of Dental Medicine at the University of Pennsylvania
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