Slow cooling protocol improves fatigue life of zirconia crowns

Author(s)

Paula, Vitor G. ^[1] ; Lorenzoni, Fabio C. ^[2] ; Bonfante, Estevam A. ^[1] ; Silva, Nelson R. F. A. ^[3] ; Thompson, Van P. ^[4] ; Bonfante, Gerson ^[1]

Affiliation

^[1] Univ Sao Paulo, Bauru Coll Dent, Dept Prosthodont, Bauru, SP - Brazil

^[2] UNIGRAN Univ, Dept Prosthodont, Dourados, MS - USA

^[3] Univ Fed Minas Gerais, Dept Restorat Dent, Belo Horizonte, MG - Brazil

^[4] Kings Coll London, Guys Hosp, Dept Biomat Biomimet & Biophoton, London - England

• Document type: Journal article
• Source: Dental Materials; v. 31, n. 2, p. 77-87, FEB 2015.
• Web of Science Citations: 19

Abstract

Objective. To compare the fatigue life and damage modes of zirconia crowns fabricated with and without framework design modification when porcelain veneered using a fast or slow cooling protocol. Methods. Composite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5 mm even thickness, Zr- C, n=20,) or modified (lingual margin of 1.0 mm thickness, 2.0 mm height connected to two proximal struts of 3.5 mm height,Zr-M, n=20). These groups were subdivided (n=10 each) according to the veneer cooling protocol employed: fast cooling (Zr-CFast and Zr-MFast) and slow cooling( Zr-CSlow and Zr-MSlow). Crowns were cemented and fatigued for 10(6) cycles in water. The number of cycles to failure was recorded and used to determine the interval databased 2-parameter probability Weibull distribution parameter Beta (beta) and characteristic life value Eta(eta). Results. 2-parameter Weibull calculation presented beta=5.53 and beta=4.38 for Zr-MFast and Zr-CFast,respectively. Slow cooled crowns did not fail by completion of 10(6) cycles, thereby Weibayes calculation was applied. Increased fatigue life was observed for slow cooled crowns compared to fast cooled ones. Groups Zr- MFast and Zr- MSlow presented no statistical difference. Porcelain cohesive fractures were mainly observed in fast cooled groups. Slow cooled crowns presented in some instances inner cone cracks not reaching the zirconia/veneer interface. Significance. Improved fatigue life in tandem with the absence of porcelain fractures were observed in slow cooled crowns, regardless of framework design. Crowns fast cooled chiefly failed by porcelain cohesive fractures. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 10/06152-9 - Reliability and fracture mode of fixed prosthesis made with indirect composites with and without CAD/CAM infrastructure over implant abutments
• Grantee: Estevam Augusto Bonfante
• Support Opportunities: Scholarships in Brazil - Post-Doctoral