Effects of repeated processing on the strength and microstructure of a heat-pressed dental ceramic

Gorman, Catherine M.; Horgan, Kate; Dollard, Ruth P.; Stanton, Kenneth T.

doi:10.1016/j.prosdent.2014.06.015

Cited by 34 publications

(51 citation statements)

References 23 publications

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“…Gorman et al 48) examined the effect of the repressing process on the strength and microstructure of IPS e.max Press, and reported that repressing of the ceramic remaining from the first pressing did not create a significant difference in hardness.…”

Section: Discussionmentioning

confidence: 99%

The effect of heat treatments applied to superstructure porcelain on the mechanical properties and microstructure of lithium disilicate glass ceramics

Özdemir

Özdoğan

2018

Dent. Mater. J.

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The aim of this study was to investigate that heat treatments with different numbers applied to superstructure porcelain whether effects microstructure and mechanical properties of lithium disilicate ceramic (LDC). Eighty disc-shaped specimens were fabricated from IPS e.max Press. Specimens were fired at heating values of porcelain in different numbers and divided four groups (n=5). Initial Vickers hardness were measured and X-ray diffraction (XRD) analysis was performed. Different surface treatment were applied and then Vickers hardness, surface roughness and environmental scanning electron microscopy (ESEM) analysis were performed. Data were analyzed with Varyans analysis and Tukey HSD test (α=0.05). Initial hardness among groups was no significant different (p>0.05), but hardness and surface roughness after surface treatments were significant different (p<0.05). Lithium disilicate (LD) peaks decrease depended on firing numbers. ESEM observations showed that firing number and surface treatments effect microstructure of LDC. Increasing firing numbers and surface treatments effect the microstructure of LDC.

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Section: Discussionmentioning

confidence: 99%

The effect of heat treatments applied to superstructure porcelain on the mechanical properties and microstructure of lithium disilicate glass ceramics

Özdemir

Özdoğan

2018

Dent. Mater. J.

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“…Fracture toughness was evaluated (n=30) by the indentation method proposed by Anstis 22 , using a microhardness tester (HMV-2, Shimadzu Corp., Kyoto, Japan) 4,11,18,20 . A load of 19,6N was applied for 20 seconds.…”

Section: Fracture Toughnessmentioning

confidence: 99%

“…A previous study reported that repeated heat pressing increased the size of crystals and porosities and decreased density, hardness, flexural strength and fracture toughness of lithium disilicate 12 . Other authors argued that mechanical properties of lithium disilicate were not significantly affected by repressing, although qualitative differences in the microstructure 11 . Another study that evaluated lithium disilicate and leucite based ceramics reported a decrease in porosities and a better crystal distribution after heat pressing, increasing flexural strength although the similar fracture toughness .…”

Section: Introductionmentioning

confidence: 99%

“…Heat pressing involves the use of heat and pressure to inject molten ceramic in an investment mold 8 . Several studies have evaluated the effect of heat pressing in the properties of different ceramic systems [8][9][10][11][12] . There is not a consensus about the effect of heat pressing at the mechanical properties and microstructure of ceramic.…”

Section: Introductionmentioning

confidence: 99%

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Fracture toughness of three heat pressed ceramic systems

et al. 2018

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Aim: The aim of this study was to evaluate fracture toughness by indentation method of three dental ceramics processed by heat pressing. The ceramics evaluated were fluorapatite glass ceramic (ZIR), glass ceramic containing leucite (POM) and leucite-reinforced glass ceramic (EMP). Materials and methods: Ninety disks (13mm of diameter x 4mm of thickness) and nine rectangular specimens (25x4x2mm) were made to evaluate, respectively, microhardness/fracture toughness (n=30) and elastic modulus (n=3). Samples were obtained by pressing ceramic into refractory molds. After polishing, Vickers microhardness was evaluated under 4,904N load for 20s. Elastic modulus was measured by impulse excitation technique. Data from microhardness and elastic modulus were used to calculate fracture toughness, after measuring crack length under 19,6N load applied for 20s. Results were evaluated by ANOVA and Tukey´s test. Results: Microhardness (VHN) of POM (637.9±53.6) was statistically greater (p<0.05) than ZIR (593.0±14. The results suggest that fluorapatite glass ceramic (ZIR) and leucite-reinforced glass ceramic (EMP) processed by heat pressing presented greater fracture toughness, improving clinical prognosis of metal free restorations.

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“…5 Resin cement may fill voids and microcracks, 21,22 while polymerization shrinkage might strengthen ceramic restorations, 23 thus resulting in higher fracture strength. The overall strength of restorative materials has been determined in laboratory tests 13,[15][16][17][18][24][25][26][27] by following questionable protocols [28][29][30] in which the fracture mechanism was not investigated or was different from clinical conditions. [31][32][33][34][35][36][37][38] If a laboratory test is performed following a protocol inconsistent with the clinical situation, the results may lead clinicians to make wrong choices related to the restorative technique and material and the cement and cementation technique.…”

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confidence: 99%