Effect of Speed Sintering on Low Temperature Degradation and Biaxial Flexural Strength of 5Y-TZP Zirconia (original) (raw)
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The Journal of Prosthetic Dentistry, 2019
STATEMENT OF PROBLEM: The lengthy sintering time of zirconia is costly and limits applications. The consequences of shortening the sintering time are mainly unknown. PURPOSE: The purpose of this in vitro study was to test and compare 2 high-speed sintering protocols and 1 conventional sintering protocol on the translucency, phase content, grain sizes, and flexural strength of 3 zirconia materials. MATERIAL AND METHODS: In total, 450 specimens of 3 zirconia materials-two were 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZPs), Ceramill ZI and Zolid (ZD), and a 4 mol% yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP), Zolid HT+ (n=150)-and 5 thicknesses (1.0, 1.5, 2.0, 2.5, and 3.0 mm; n=30) were sintered according to 2 high-speed sintering protocols (final temperature 1570°C and 1590°C; n=10) and a reference sintering protocol (1450°C; n=10). After measuring the monoclinic phase content with Raman spectrometry (n=3), the specimens were polished, and translucency was determined. The biaxial flexural strength of specimens with a thickness of 1.0 mm and 1.5 mm was tested (n=20). Statistical evaluation included 1-way ANOVA, the Kolmogorov-Smirnov, Kruskal-Wallis, Mann-Whitney-U, and Spearman-Rho tests and the Bonferroni correction (=.0011). RESULTS: For ZI, the sintering protocols did not affect the translucency or biaxial flexural strength. ZD and HT+ showed significantly lower translucency for high-speed sintering protocols (P.001), but the biaxial flexural strength remained the same after the high-speed sintering protocol at 1590°C. Grain sizes increased with increasing final sintering temperature for ZI and HT+, whereas translucency generally decreased with increasing material thickness. No monoclinic phase was detected in any group. CONCLUSIONS: The flexural strength was maintained with high-speed sintering but led to a decrease in translucency for ZD and HT+.
Effect of different sintering process on flexural strength of translucency monolithic zirconia
Journal of Clinical and Experimental Dentistry, 2018
Background: Sintering process is responsible for the strength of zirconia restoration. This study evaluated the effect of different sintering temperatures and sintered-holding times on flexural strength of translucency monolithic zirconia. Material and Methods: One hundred and thirty five zirconia bar specimens (width-length-thickness = 10×20×1.5 mm) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic and randomly divided into nine groups to be sintered at different temperatures [decreasing-(S D , 1350°C), regular-(S R , 1450°C), and increasing-(S I , 1550°C) sintering temperature] and different sintered-holding times [shortening-(H S , 60 min), regular-(H R , 120 min), and prolonged-(H P , 180 min) sintered-holding time]. Flexural strength was determined using three-point bending test in a universal testing machine at 1 mm/min crosshead speed. An analysis of variance (ANOVA) and Tukey's multiple comparisons were used to determine for statistically significant difference of flexural strength (α=0.05). Weibull analysis was applied for survival probability, Weibull modulus (m), and characteristics strength (σ o) of the flexural strength. The crystal sizes were microscopically examined using scanning electron microscope (SEM). The phase composition of zirconia was determined using X-ray diffraction (XRD).
Sintering Strategies for Dental Zirconia Ceramics: Slow Versus Rapid.
Purpose of Review Advances in zirconia ceramics have expanded their application in dentistry, necessitating faster delivery of zirconia-based restorations. With the introduction of high translucency grades of zirconia ceramics, the rapid sintering strategies that aim to reduce processing times can have a central impact on clinically relevant properties. The present review has surveyed the available literature evaluating the properties of rapidly sintered dental zirconia ceramics. Recent Findings Recent studies emphasize the evolution of sintering protocols for zirconia ceramics, especially highlighting differences between conventional sintering (CS) and rapid methods like speed (SS) and high-speed sintering (HSS). These modern rapid sintering techniques transform the microstructure of zirconia ceramics, impacting its translucency, flexural strength, and aging resistance. These properties exhibit variability based on zirconia type and chosen sintering process, with HSS showing particular promise. Summary Rapid sintering protocols offer efficient alternatives to traditional zirconia ceramic processing, with benefits in cost and time. Despite the recent findings, discrepancies persist within zirconia generations, calling for further standardization and investigation.
The Effect of Zirconia Sintering Temperature on Flexural Strength, Grain Size, and Contrast Ratio.
Objective This study investigated the effect of sintering temperatures on flexural strength, contrast ratio, and grain size of zirconia. Materials and Methods Zirconia specimens (Ceramill ZI, Amann Girrbach) were prepared in partially sintered state. Subsequently, the specimens were randomly divided into nine groups and sintered with different final sintering temperatures: 1,300°C, 1,350°C, 1,400°C, 1,450°C, 1,500°C, 1,550°C, 1,600°C, 1,650°C, or 1,700°C with 120 min holding time. Three-point flexural strength (N0198; n022 per group) was measured according to ISO 6872: 2008. The contrast ratio (N 090; n 010 per group) was measured according to ISO 2471: 2008. Grain sizes and microstructure of different groups were investigated (N09, n01 per group) with scanning electron microscope. Data were analyzed using one-way ANOVA with Scheffé test and Weibull statistics (p<0.05). Pearson correlation coefficient was calculated between either flexural strength or contrast ratio and sintering temperatures. Results The highest flexural strength was observed in groups sintered between 1,400°C and 1,550°C. The highest Weibull moduli were obtained for zirconia sintered at 1,400°C and the lowest at 1,700°C. The contrast ratio and the grain size were higher with the higher sintering temperature. The microstructure of the specimens sintered above 1,650°C exhibited defects. Sintering temperatures showed a significant negative correlation with both the flexural strength (r0−0.313, p<0.001) and the contrast ratio values (r0−0.96, p<0.001).
Aging resistance of highly translucent zirconia ceramics with rapid sintering
Journal of Oral Science, 2023
Purpose: Rapid sintering technology has become one of the most direct methods for shortening the manufacturing time of zirconia restorations. This study aimed to explore the aging resistance of rapid-sintered 5 mol% yttria-partially-stabilized zirconia (5Y-PSZ). Methods: Specimens were made from two types of 5Y-PSZ material and subjected to rapid sintering (RS) and conventional sintering (CS). After in vitro aging for 5 h, morphology observation, grain size measurement, and phase composition analysis were performed. The mechanical properties were evaluated by biaxial, three-point flexural tests, and the Vickers microhardness test. Results were analyzed by 3-way ANOVA. Results: Both the RS group and the CS group had a dense microstructure. The tested zirconia ceramics had different grain sizes, which were affected by the interaction between the sintering method and aging. Both groups revealed the same characteristic peaks of the cubic phase after aging. Regardless of the sintering method used, there was no significant difference in the mechanical properties of the tested zirconia before and after aging. Conclusion: The rapid-sintered 5Y-PSZ materials had a microstructure, phase composition and mechanical properties similar to those of conventional sintered materials. The characteristics of the materials prepared using the two sintering methods did not change significantly after aging.
Advances in Science and Technology, 2014
Ceramics for dental applications have become increasingly important in the last decades. Particularly, the introduction of yttria-stabilized zirconia tetragonal polycrystalline (Y-TZP) materials as an alternative to the manufacturing of dental implants and prosthesis has provided a powerful tool to meet the demands required for these replacements in terms of biocompatibility, toughness, hardness and optical properties. Several commercial Y-TZP materials are currently available on the market and strong efforts in research and development facilities are being carried out to improve processing of Y-TZP to fully consolidate odontological pieces. Novel processing methods for ceramic powder sintering, including Y-TZP, aim to reduce processing times and production costs significantly, while maintaining or even improving the resulting microstructure and mechanical properties of the material. One of these methods includes microwave sintering. The purpose of this study is to characterize and compare the resulting properties of Y-TZP materials after conventional sintering and the non-conventional method of microwave heating. In this work one commercial material and one laboratory-synthesized Y-TZP powder are considered. The results suggest that microwave sintering results, generally, in better mechanical properties of the material in terms of hardness and fracture toughness than conventional sintering.
Effect of sintering protocols on zirconia with various YTTRIA concentrations
2021
OBJECTIVES: To compare the effects of different sintering protocols on density, translucency, microstructure, crystallography, and biaxial flexural strength of different yttria concentrations of Tosoh zirconia materials (TZ-3YSB-E, TZ-3YB-E, Zpex, and Zpex Smile). MATERIALS AND METHODS: A total of 242 zirconia discs were manufactured from commercially available Tosoh zirconia powders. Zpex smile, Zpex, TZ-3YB-E, and TZ-3YSB-E were uniaxially dry pressed into cylindrical blocks using a 5/8-inch internal diameter steel die set under a hydraulic press load of 3,000 N (Carver Press). Blocks were partially sintered at 1000 °C and sectioned into discs with a thickness of 2 mm x 15 mm by an IsoMet 5000 section machine. The discs were fully sintered using three protocols: 1) regular sintering using Vita Zyrcomat T furnace at 1520 °C for 2 h (total cycle time of 7 h); 2) fast sintering using Sirona inFire HTC SPEED at 1540 °C for 30 min (total cycle time of ~1.5 h). 3) speed sintering using ...
Translucency and Biaxial Flexural Strength of Monolithic Zirconia as Affected by Sintering Speeds
Egyptian Dental Journal
Statement of the problem: Approaches towards reducing fixed prosthetic restoration fabrication times include; (CAD/CAM) chair side systems in addition to rapid sintering cycles, which can be carried out in minutes rather than hours in order to deliver zirconia-based restorations in one visit .However, limited information is available regarding the effect of rapid sintering on properties of monolithic translucent zirconia. Aim of the study: The aim of this study was to evaluate the effect of changing the sintering speed (classic, speed and super speed cycles) on translucency and biaxial flexural strength of monolithic translucent zirconia before and after thermodynamic aging. Materials & Methods: 36 monolithic translucent zirconia discs (10mm diameter×0.8mm thickness) were CAD/CAM fabricated from translucent zirconia blocks(In Coris TZI) and randomly divided into three main groups (n=12 each) according to the sintering speed; group I: samples sintered by classic sintering cycle (sintering at 1510°C for 120 min holding time & 8 hours total cycle time), group II: speed sintering (sintering at 1540°C for 25 min holding time & 2 hours total cycle time) and group III: super speed sintering (sintering at 1580°C for 10 min holding time representing the total firing cycle). In each group, half of the samples were evaluated in the non-aged condition (subgroup1, n=6) while the other half were evaluated after thermodynamic aging (subgroup2, n=6) in a chewing simulator. Translucency parameter (TP) and contrast ratio (CR) were measured using a digital reflective spectrophotometer. Biaxial flexural strength (MPa) was tested using piston on three ball technique in a universal testing machine. Representative sample from each subgroup was analyzed by Scanning electron microscope. Statistical analysis was performed using Two-way ANOVA and Tukey's post-hoc tests (P ≤ 0.05). Results: Two-way ANOVA revealed that sintering speed and thermodynamic aging had a statistically significant effect on mean (TP), (CR).Either before or after aging, classic cycle showed the statistically significantly highest mean (TP) & lowest (CR) values. On the other hand, biaxial flexural strength was statistically significantly affected by the sintering speed only and not by thermodynamic aging; the super speed cycle registered the lowest mean biaxial flexural strength before and after thermodynamic aging.
Acta Biomaterialia Odontologica Scandinavica, 2015
Objective: This study investigated the effect of different sintering temperatures and times on the flexural strength and grain size of zirconia. Material and methods: Zirconia specimens (In-Coris ZI, In-Coris TZI, 120 samples) were prepared in a partially sintered state. Subsequently, the specimens were randomly divided into three groups and sintered at different final sintering temperatures and for various durations: 1510 C for 120 min, 1540 C for 25 min and 1580 C for 10 min. Three-point flexural strength (for 120 samples, 20 samples per group) was measured according to the ISO 6872: 2008 standards. The grain sizes were imaged by scanning electron microscopy (SEM) and the phase transitions were determined by X-ray diffraction (XRD). The data were analyzed using one-way ANOVA and Duncan tests (p50.05). Results: The highest flexural strength was observed in ZI and TZI samples sintered at 1580 C for 10 min. The differences between the ZI samples sintered at 1510 C for 120 min and those sintered at 1540 C for 25 min were statistically insignificant. Also, TZI samples sintered at 1510 C for 120 min and those sintered at 1540 C for 25 min also did not show any statistically significant differences. There were no visible differences in the grain sizes between the ZI and TZI specimens. The XRD patterns indicated similar crystalline structure for both materials subjected to the three different procedures. Conclusions: The results of this study showed that experimented high sintering temperature and short sintering time combination increases the flexural strength of zirconia.
Advanced Materials Research, 2014
Zirconia-based ceramics exhibit excellent mechanical properties and biocompatibility in dental applications. However, the production of translucent zirconia that offers resemblance to real teeth remains a challenge. This study aims to fabricate zirconia compacts by cold isostatic pressing (CIP) and investigate the influence of sintering temperature on translucency, microstructure, hardness, and density of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Zirconia stabilized with 3 mol% yttria (3Y-TZP) was pressed by uniaxial pressing and later by CIP to produce green bodies in pellet form. Subsequently, the green bodies were sintered at different temperatures (1100 °C to 1300 °C). The specimens were then investigated in terms of translucency, density, and hardness. X-ray diffraction was also performed and the microstructure of the specimens was observed under a scanning electron microscope (SEM). Density and light transmittance tests results showed that zirconia sintered a...