title: Experimental and finite element study of residual thermal stresses in veneered Y-TZP structures.
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.
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA; Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Carina B
authors.initials: CB
authors.lastname: Tanaka
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA.
authors.forename: Hossam
authors.initials: H
authors.lastname: Harisha
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA.
authors.forename: Marta
authors.initials: M
authors.lastname: Baldassarri
authors.affiliation: Department of Cariology and Comprehensive Care, Associate Dean for Pre-doctoral Clinical Education, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Wolff
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, Hunan 410083, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tong
authors.affiliation: Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Josete B C
authors.initials: JB
authors.lastname: Meira
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
keywords: Cooling rates; Finite element analysis; Porcelain-veneered zirconia; Residual thermal stresses; Specimen geometries; Vickers indentation method