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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Analysis of thermal distributions in veneered zirconia and metal restorations during firing

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Author(s):
Benetti, Paula [1] ; Kelly, John Robert [2] ; Della Bona, Alvaro [3]
Total Authors: 3
Affiliation:
[1] Univ Passo Fundo, Sch Dent, Rio De Janeiro - Brazil
[2] Univ Connecticut, Dept Reconstruct Sci, Farmington, CT - USA
[3] Univ Passo Fundo, Postgrad Program Dent, Rio De Janeiro - Brazil
Total Affiliations: 3
Document type: Journal article
Source: Dental Materials; v. 29, n. 11, p. 1166-1172, NOV 2013.
Web of Science Citations: 28
Abstract

Objective. The present work evaluated the thermal behavior of porcelain-metal and porcelain-zirconia restorations during fast and slow firing and cooling. Methods. All-ceramic (porcelain on zirconia) and porcelain-fused-to-metal (PFM) molar crowns were fabricated with 1 or 2 mm porcelain thickness. Thermocouples were attached to the cementation (Ti) and occlusal (T4) surfaces of the restoration and embedded at the framework-porcelain interface (T2) and inside the porcelain (T3) to acquire temperature readings by time. Slow heating was set as 45 degrees C/min and fast heating as 140 degrees C/min. For fast cooling, the furnace was opened immediately after the holding time. Slow cooling was effected by opening the furnace when it reached 50 degrees C below the T-g. Porcelains T-g were calculated for each cooling rate. Results. Slow heating rate was measured at T4 as being 30 degrees C/min while fast heating at T4 was 100 degrees C/min. The measured cooling rates within the porcelain (T2) around the To range were 20 degrees C/min and 900 degrees C/min for slow and fast cooling, respectively. During slow cooling, similar temperatures were found for both zirconia and metal crowns. Remarkable temperature gradients were observed for the fast cooled all-ceramic crown (T1-T4= 100 degrees C) and, of lower magnitude for PFM (T1-T4 = 30 degrees C). To of porcelains increase with faster cooling rates. Signcance. Slow cooling appears to be especially important for all-ceramic crowns to prevent high magnitude thermal gradients, which could influence cracking and fracture of the porcelain. (C) 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. (AU)