Effects of multiple firing processes on the mechanical properties of lithium disilicate glass-ceramics produced by two different production techniques

• Published in: The Journal of prosthetic dentistry Vol. 125; no. 3; pp. 527.e1 - 527.e7
• Main Authors: Ozdogan, Alper, Ozdemir, Hatice
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-03-2021
• Subjects: Ceramics; Computer-Aided Design; Dental Porcelain; Dentistry; Materials Testing; Surface Properties
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/j.prosdent.2020.10.016

Repeated firings cause materials to be exposed to additional heat treatments. The effect of these additional heat treatments on the mechanical properties of lithium disilicate glass-ceramics is not fully known.
The purpose of this in vitro study was to determine the effects of repeated firing on the mechanical properties of lithium disilicate glass-ceramics produced by 2 different techniques, press and computer-aided design and computer-aided manufacturing (CAD-CAM).
Eighty rectangular (25×4×2 mm) lithium disilicate glass-ceramic specimens were used in this study, 40 produced by heat pressing and 40 by milling, and divided into 4 groups (n=10) with a different number of veneer porcelain firings (1 to 4). After firing, the Vickers hardness, flexural strength (3-point bend test), and fracture toughness were determined, and the specimens were analyzed with an environmental scanning electron micrograph. Data were analyzed with analysis of variance (ANOVA) (α=.05).
The repeat firing processes did not affect the flexural strength of the specimens in either group (P>.05), while the surface hardness and fracture toughness were significantly changed (P<.05).
Increasing the number of firings adversely affected the mechanical properties of lithium disilicate glass-ceramics.