Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

Abstract

The objective of this work was to evaluate biaxial-flexural-strength (σ f ), Vickers hardness (HV), fracture toughness (K Ic ), Young's modulus (E), Poisson's ratio (ν) and porosity (P) of two commercial glass-ceramics, Empress (E1) and Empress 2 (E2), as a function of the hot-pressing temperature. Ten disks were hot-pressed at 1065, 1070, 1075 and 1080 °C for E1; and at 910, 915, 920 and 925 °C for E2. The porosity was measured by an image analyzer software and σ f was determined using the piston-on-three-balls method. K Ic and HV were determined by an indentation method. Elastic constants were determined by the pulse-echo method. For E1 samples treated at different temperatures, there were no statistical differences among the values of all evaluated properties. For E2 samples treated at different temperatures, there were no statistical differences among the values of σ f , E, and ν, however HV and K Ic were significantly higher for 910 and 915 °C, respectively. Regarding P, the mean value obtained for E2 for 925 °C was significantly higher compared to other temperatures.

The effect of slurry preparation methods on biaxial flexural strength of dental porcelain

“…As a consequence, higher porosity is expected due to the larger amount of space between powder particles following the evaporation of the water, reducing the efficacy of the viscous flow sintering process and resulting in higher porosity levels. 23,25 The porosity level may not be the sole factor affecting the flexural strength of dental ceramics, since a previous study 39 showed that glassceramics with significantly higher porosity (due to processing at higher temperatures) possessed statistically similar flexural strengths to glassceramics with lower porosity levels. It is important to consider that the flexural strength of brittle materials is determined by the flaw population of the tested material, and therefore, the present study showed that the one-step technique produced in a less favorable flaw population resulted in decreased mechanical behavior.…”

“…14,38 Open porosity volume was calculated following the determination of the apparent density based on the Archimedes water displacement method. 39 Statistical analysis was conducted using a descriptive approach based in the maximum and minimum values of calculated biaxial flexural strength. The Kolmogorov-Smirnov (KS) test was applied to determine if the Weibull model was an adequate distribution for the experimental data obtained for both groups.…”

Effect of Pre-Crystallization on Lithium Disilicate Glass-Ceramics Fabricated by Different Processes

“…One all-ceramic system is lithium disilicate glass ceramic (Li 2 Si 2 O 5 ), currently used for dental restorations for mainly dental crowns, bridges and veneers because of its excellent mechanical properties, longevity and esthetic characteristics [4][5][6][7][8][9][10][11] . Lithium disilicate glass ceramic has superior optical properties by itself.…”

“…The CAD/CAM restorations are better-fitting, more durable and more natural looking (multi-colored and translucent, similar to natural teeth) than previously machined restorations. In addition, CAD/CAM technology has enabled dental clinicians to restore teeth using ceramic material in a single appointment 9 . Meanwhile, hot pressing technology, which most technicians are usually familiar with, demonstrates the ability to produce dental restorations effectively due to a wide variety of pressable and inexpensive ceramics that are available 1,16 .…”

Characterisation and Properties of Lithium Disilicate Glass Ceramics in the SiO2-Li2O-K2O-Al2O3System for Dental Applications

“…In general, glass ceramics can be produced by melting glass and converting the substance into a uniform nucleation and growth of fine-grained ceramics by controlled crystallization process, in which the crystalline phases are nucleated and grown in glass via heat treatment [3][4][5]. Lithium disilicate glass ceramic, in particular the Li 2 O-SiO 2 system, is the first material classified as glass ceramic discovered by Stookey as having better mechanical properties over base glass [6].…”