Moustafa N Aboushelib1, Albert J Feilzer, Cees J Kleverlaan. 1. Department of Dental Materials Science, Academic Center for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, The Netherlands. mabou@acta.nl
Abstract
OBJECTIVE: The aim of this study was to analyze and to compare the fracture type and the stress at failure of clinically fractured zirconia-based all ceramic restorations with that of morphologically similar replicas tested in a laboratory setup. METHODS: Replicas of the same shape and dimensions were made for 19 crowns and 17 fixed partial dentures, all made of veneered zirconia frameworks, which fractured during intra-oral service. The replicas were statically loaded by applying axial load in a universal testing machine. The principles of fractography were used to identify the location and the dimensions of the critical crack and to estimate the stress at failure. Failure was classified according to origin and type (P<0.05 was considered significant). RESULTS: Clinically fractured restorations failed due to either: delamination of the veneer ceramic (28.2+/-9MPa), defects at core veneer interface (27.7+/-6MPa), the generation of Hoop stresses (884.3+/-266MPa), radial cracking (831MPa), or fracture of the connector (971+/-343MPa). The replicas failed by mainly by cone cracking of the veneer ceramic (52.4+/-34.8MPa) or by fracture of the connector (1098.9+/-259MPa). The estimated stress at failure was significantly higher for the replicas compared to the clinically fractured restorations (F=6.8, P<0.01). SIGNIFICANCE: Within limitations of this study, careful design of fracture strength test would lead to more clinically relevant data. The performance of zirconia veneered restorations could be further improved with careful design considerations.
OBJECTIVE: The aim of this study was to analyze and to compare the fracture type and the stress at failure of clinically fractured zirconia-based all ceramic restorations with that of morphologically similar replicas tested in a laboratory setup. METHODS: Replicas of the same shape and dimensions were made for 19 crowns and 17 fixed partial dentures, all made of veneered zirconia frameworks, which fractured during intra-oral service. The replicas were statically loaded by applying axial load in a universal testing machine. The principles of fractography were used to identify the location and the dimensions of the critical crack and to estimate the stress at failure. Failure was classified according to origin and type (P<0.05 was considered significant). RESULTS: Clinically fractured restorations failed due to either: delamination of the veneer ceramic (28.2+/-9MPa), defects at core veneer interface (27.7+/-6MPa), the generation of Hoop stresses (884.3+/-266MPa), radial cracking (831MPa), or fracture of the connector (971+/-343MPa). The replicas failed by mainly by cone cracking of the veneer ceramic (52.4+/-34.8MPa) or by fracture of the connector (1098.9+/-259MPa). The estimated stress at failure was significantly higher for the replicas compared to the clinically fractured restorations (F=6.8, P<0.01). SIGNIFICANCE: Within limitations of this study, careful design of fracture strength test would lead to more clinically relevant data. The performance of zirconia veneered restorations could be further improved with careful design considerations.
Authors: Marina Amaral; Regina F Villefort; Renata Marques Melo; Gabriel K R Pereira; Yu Zhang; Luiz Felipe Valandro; Marco Antonio Bottino Journal: J Mech Behav Biomed Mater Date: 2017-03-07
Authors: Martin Rosentritt; Felix Heidtkamp; Helmut Hösl; Sebastian Hahnel; Verena Preis Journal: Clin Oral Investig Date: 2015-06-09 Impact factor: 3.573