Effects of multiple firings on the microstructure of zirconia and veneering ceramics

Alkurt, Murat; Duymuş, Zeynep Yesïl; Gundogdu, Mustafa

doi:10.4012/dmj.2015-429

Cited by 12 publications

(8 citation statements)

References 29 publications

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“…It is important to remember that during manufacturing restorations that are consisted of a zirconia substructure covered with a feldspathic ceramic using the layering technique, explored herein, its usual to execute many firing cycles during the application of the 1st dentin layer, 2nd dentin layer, enamel, and/or even finally with the glaze material to achieve the final thickness of restauration [9]. So, our data corroborate that such processing would inherently lead to alterations of color, optical characteristics, and also potentially impact the mechanical properties of the future restoration, in accordance with prior studies [9,22,23,24]. In fact, a previous study [22] reported that veneering ceramics fired 10 times showed higher density and less porosity than those fired twice.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, it is fundamental that veneering ceramics (such as feldspathic) have good mechanical properties through appropriate confection and firing processes. It is already known that the multiple firing cycles of the veneering feldspathic ceramic applied over zirconia cores can effectively improve its hardness [8,9]. Also, according to Hasssija et al [10], repeating firings did not affect the color parameters of ceramics with metal core.…”

Section: Introductionmentioning

confidence: 92%

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Fatigue behavior and colorimetric differences of a porcelain-veneered zirconia: effect of quantity and position of specimens during firing

et al. 2021

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Purpose: To evaluate the influence of quantity and positioning of veneered zirconia specimens during firing of porcelain on their fatigue performance and colorimetric differences. Methods: Bilayer discs (Ø=15 mm) were made, following ISO 6872 guidelines, using a Y-TZP core (yttria-stabilized tetragonal zirconia polycrystal ceramic; VITA In-Ceram YZ) and a feldspathic veneering material (VITA VM9), being both layers with 0.7 mm thickness. Y-TZP discs were sintered, the veneering material was applied over it, and the bilayer specimens were fired according to two factors (n=20): 'quantity' (1 or 5 samples per firing cycle; G1 and G5 groups respectively) and 'positioning' of the specimens inside the furnace (center or periphery of the refractory tray; G5C and G5P groups, respectively). The CIEL*a*b* parameters were recorded with a spectrophotometer and the color difference (ΔE 00) and translucency (TP 00) were calculated using CIEDE2000 equations. The step-stress fatigue test was performed with the veneer facing down (region of tensile stress concentration), 10 Hz frequency, initial tension of 20 MPa for 5,000 cycles, followed by steps of 10,000 cycles using a step size of 10 MPa, up to 100 MPa; data from strength and number of cycles for failure were recorded for statistical analysis. Results: Unacceptable color differences (ΔE 00 >1.8) were observed comparing G5C vs. G1 (quantity) and G5C vs. G5P (positioning), meanwhile translucency parameters were not affected. Besides, only the 'quantity' factor influenced the fatigue performance (G1>G5C). None of the tested specimens survived beyond 90N and/or 75000 cycles. Conclusions: The quantity and position of the specimens during firing influence the final color of porcelain-veneered zirconia, and firing one specimen per cycle improved the fatigue performance of the bilayer system.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Fatigue behavior and colorimetric differences of a porcelain-veneered zirconia: effect of quantity and position of specimens during firing

et al. 2021

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“…Nonetheless, other studies evaluating monolithic porcelain specimens, observed that increasing number of firings can improve hardness, density, and decrease porosity. 45,46 Among the included studies, only one evaluated the effect of glaze firing on bilayer specimens. 25 The experimental groups included one that was just polished and another polished and self-glazed, which presented higher flexural strength.…”

Section: Discussionmentioning

confidence: 99%

Do thermal treatments affect the mechanical behavior of porcelain-veneered zirconia? A systematic review and meta-analysis

et al. 2019

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Objectives.-A systematic review of in vitro studies was conducted to assess the effect of thermal treatments on flexural strength or critical load to failure of porcelain-veneered zirconia (PVZ). Sources.-Literature searches were performed up to June 2018 in PubMed/MEDLINE, Scopus and Web of Science databases, with no publication year or language limits. Data.-From 393 relevant studies, 21 were selected for full-text analysis, from which 7 failed to meet the inclusion criteria. The 14 remaining papers were included for the systematic review: 8 for meta-analysis and 6 restricted to descriptive analyses. Hand searching of reference lists resulted in no additional papers. Study selection.-In vitro studies using PVZ specimens testing the influence of thermal treatments on the fracture resistance to monotonic or cyclic loading. Papers evaluating cooling rate were divided into those applying fast cooling from above the porcelain glass transition temperature (T g), or from below it. Meta-analyses were performed separately for flexural strength and critical load to failure, using random effects at a 5% significance level. Conclusions.-Delaying furnace opening at a temperature below the porcelain T g is advised for PVZ restorations, in order to improve their fracture resistance. Additional information is required to confirm the apparently beneficial effect of self-glaze and repeated veneer firings on the mechanical properties of these restorations. Finally, in order to obtain conclusive and relevant evidence regarding thermal treatments and the fracture resistance of PVZs, future studies should concentrate on anatomically-correct crown specimens.

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“…2 Previous studies indicated that multiple firings have effects on the microhardness and flexural strength of zirconia; 10 mechanical properties and microstructure of veneering ceramics; 2 and the bond strength between veneering ceramic and zirconia framework. 11,12 Also, different firing procedures were reported to cause alterations in microstructural properties and surface characteristics of zirconia 9,13 and were associated with clinical performance and longevity of zirconia restorations. 14 Another factor considered to influence the clinical performance of zirconia restorations is the bond strength between luting material and restoration.…”

Section: Introductionmentioning

confidence: 99%

“…In simple clinical procedures, zirconia restorations usually undergo 2 to 5 firings after sintering for veneering procedure. 9 However, multiple firings may be required to correct the occlusion, marginal adaptation, contours or color of the veneering porcelain. 2 Previous studies indicated that multiple firings have effects on the microhardness and flexural strength of zirconia; 10 mechanical properties and microstructure of veneering ceramics; 2 and the bond strength between veneering ceramic and zirconia framework.…”

Section: Introductionmentioning

confidence: 99%

Impact of multiple firings and resin cement type on shear bond strength between zirconia and resin cements

et al. 2020

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The aim of this study was to evaluate the effect of multiple firings on the bond strength between yttriatetragonal zirconia polycrystals (Y-TZP) and 2 types of resin cements. MATERIALS AND METHODS. Sixty 3Y-TZP specimens (LAVA Frame Multi) were divided into 3 groups depending on the following firing procedures: (1) 2-firing cycles, (2) 5-firing cycles, (3) 10-firing cycles. Two samples from each group were investigated by using SEM to determine the morphological changes. All specimens were treated with 125 μm airborne-particle abrasion and the surface roughness of each specimen was measured. The specimens from each firing group were then further divided into 2 subgroups (n = 9) to apply 2 types of resin cement (MDP-free resin cement: RelyX Unicem-RU, and MDP containing resin cement: Panavia F 2.0-PA). The shear bond strength (SBS) test was performed and failure types of all the debonded specimens were classified by using a stereomicroscope as adhesive, cohesive, and mixed. The statistical analysis of surface roughness and SBS data were performed by using 1-way ANOVA and 2-way ANOVA followed by Tukey-HSD tests (α=.05). Failure modes were calculated as a percentage for each group. RESULTS. The bond strength of RU and PA to the specimens obtained with 2 firings were not statistically different from each other (P=.1). However, the SBS values of PA were found to be significantly higher than RU for the specimens obtained with 5 and 10 firing cycles (P=.001 and P=.02, respectively). Surface roughness analysis revealed no statistical difference between groups (P=.2). The SEM analysis of samples fired 5-and 10-times showed irregularities and boundary loss in zirconia grains, and empty spaces between zirconia grains. CONCLUSION. The bond strength of PA cement was higher than that of RU to the zirconia subjected to repeated firings (5 and 10 firing cycles). When zirconia is subjected to multiple firings, using MDP-containing resin cement can be recommended.

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Effects of multiple firings on the microstructure of zirconia and veneering ceramics

Cited by 12 publications

References 29 publications

Fatigue behavior and colorimetric differences of a porcelain-veneered zirconia: effect of quantity and position of specimens during firing

Fatigue behavior and colorimetric differences of a porcelain-veneered zirconia: effect of quantity and position of specimens during firing

Do thermal treatments affect the mechanical behavior of porcelain-veneered zirconia? A systematic review and meta-analysis

Impact of multiple firings and resin cement type on shear bond strength between zirconia and resin cements

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