Translucency and Biaxial Flexural Strength of Monolithic Zirconia as Affected by Sintering Speeds (original) (raw)
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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).
Egyptian Dental Journal
Statement of Problem: Since ultra high translucent cubic zirconia was evolved in the market, comparison were made with high translucent tetragonal zirconia regarding translucency and flexural strength after thermal aging. Aim of This Study : The aim of this study is to detect translucency and flexural strength changes of two different zirconia materials before and after aging. Material and Methods: Forty Zirconia samples (n=20) from each type (Cubic and Tetragonal Zirconia) were prepared then autoclaved. The aging parameter was set to a temperature of 134 C° and a pressure of 2 bar for 10 hours of aging. A spectrophotometer device was used for measurement of translucency and contrast ratio of each group. Piston and three supporting balls test were used for flexural strength test. Results: The results showed that Zirconia type (regardless of aging) had a statistically significant effect on mean translucent parameter and flexural strength. Aging had a statistically significant effect on mean translucent parameter and flexural strength except for the cubic zirconia which showed non-significant lower flexural strength after aging. Conclusion: Aging (regardless of Zirconia type) had a statistically significant effect on mean translucent parameter and flexural strength. Flexural strength of cubic zirconia was not significantly affected by aging.
Evaluation of Translucency and Biaxial Flexural Strength of Different Ceramic Materials
Al-Azhar Journal of Dental Science
Objective: To evaluate Translucency and Flexural strength of four ceramic materials Lithium disilicate (Emax), translucent zirconia (Bruxizir), Ultra translucent zirconia (Katana ST) and Zirconia reinforced lithium silicate (Suprinity), using two thickness, 0.5 mm and 1mm. Materials and Methods: Blocks of four CAD/CAM esthetic restorative materials (emax, suprinity, bruxzir and katana) were used to prepare 80 samples (disks) with the following dimensions: 10mm x 0.5mm and 10mm x 1mm for suprinity and emax ceramic material & 12mm x 0.6mm and 12mm x 1.2mm for Bruxzir and katana ceramic material. Using IsoMet 4000 micro saw by a diamond disk 0.6 mm thickness with cutting speed 2500 rpm. Then all the disks were crystallized and sintered. One Ceramic disc of each material were examined under a Reflective spectrophotometer (Model RM200QC, X-Rite, Neu-Isenburg, Germany) to determine the translucency for each disk. After that each disk was subjected to a biaxial flexural strength test. Results: For translucency test, at 0.5mm the highest value was found with Vita Suprinity (21.71±1.59), followed by Emax (17.89±3.47), then Bruxzir (13.27±1.86) while the lowest value was found with Katana ST (11.57±2.45). while at 1mm the highest value was found with Emax (14.78±1.63), followed by Vita Suprinity (14.65±1.58), then Katana ST (10.59±2.16) while the lowest value was found with Bruxzir (10.42±1.56). Otherwise for biaxial flexural strength, at 0.5 mm the highest value was found with bruxzir (194.04±59.50), followed by Katana ST (191.66±63.71), then suprinity (163.96±28.86), while the lowest value was found with Emax (113.70±26.76). while at 1mm the highest value was found with Katana ST (605.47±115.98), followed by Bruxzir (588.40±111.39), then Emax (474.62±68.36) while the lowest value was found with Vita Suprinity (419.50±76.96). Conclusion: Increasing thickness affect the flexural strength of ceramic material positively, while it affects the translucency negatively except for katana. Different ceramic material exhibited variable translucency and flexural strength values depending on their composition. Lithium disilicate materials show more translucency and lower flexural strength than zirconia materials.
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).
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+.
Biaxial Flexural Strength of Different Monolithic Zirconia upon Post-Sintering Processes
European Journal of Dentistry
Objective Different post-sintering processes are expected to be a reason for alteration in the strength of zirconia. This study evaluated the effect of post-sintering processes on the flexural strength of different types of monolithic zirconia. Materials and Methods A total of 120 classical- (Cz) and high-translucent (Hz) monolithic zirconia discs (1.2 mm thickness and 14 mm in Ø) were prepared, sintered, and randomly divided into four groups to be surface-treated with (1) as-glazed (AG); (2) finished and polished (FP); (3) finished, polished, and overglazed (FPOG); and (4) finished, polished, and heat-treated (FPHT) technique (n = 15). Biaxial flexural strength (σ) was determined on a piston-on-three ball in a universal testing machine at a speed of 0.5 mm/min. Statistical Analysis Analysis of variance, and post hoc Bonferroni multiple comparisons were determined for significant differences (α = 0.05). Weibull analysis was applied for survival probability, Weibull modulus (m), and ...
The Journal of Contemporary Dental Practice
Aim: The aim of this in vitro study was to evaluate the effect of accelerated artificial aging (AAA) and fatigue on the biaxial flexural strength (BFS) of three types of monolithic hightranslucency zirconia restorations compared with conventional low-translucency zirconia restorations. Materials and methods: Four groups of 20 disc-shaped specimens (10 × 1.2 mm) were made from the following computeraided design and computer-aided manufacturing (CAD/CAM) zirconia blocks: Low-translucency zirconia (Ceramill ZI-LT) as a control, and three brands of high-translucent zirconia (Lava Plus, Ceramill Zolid White, and Copran Monolithic HT). Ten discs from each group were subjected to the BFS test using the universal testing machine. The other 10 discs from each group were subjected to AAA (thermocycling, 3,500 cycles) and fatigue (250,000 cycles) before the fracture test. The definitive fracture load was recorded, and the BFS was calculated in accordance with International Organization for Standardization (ISO) 6872. The data were analyzed with one-way analysis of variance (ANOVA), Scheffe post hoc, and Mann-Whitney U test. Data analyses were evaluated at a significance level of p ≤ 0.05. Results: Significant differences were detected in the BFS among the four groups before AAA and fatigue. The mean BFS was highest with Ceramill ZI (935.3 ± 47.1 MPa), and least in Ceramill Zolid White (685.7 ± 32.6 MPa). After AAA and fatigue, significant differences were reported where the mean of BFS was highest with Copran Zr-i Monolithic HT (777.5 ± 21.2 MPa), and least in Ceramill Zolid White (576.0 ± 36.3 MPa).
Egyptian dental journal, 2022
Purpose: The ultimate appearance of all ceramic restorations is significantly influenced by color and translucency. The performance of the restoration is significantly influenced by flexural strength. This study's objective was to assess how various shading methods affected the color, translucency, and flexural strength of monolithic zirconia ceramic as it aged. Materials and Methods: Thirty zirconia discs with a diameter of 12mm and thickness of 1mm were divided into two groups of 15 discs each according to the technique of shading, the first group was constructed from A2 pre-shaded zirconia while the second group was constructed from unshaded zirconia that was shaded by immersion in A2 coloring liquid. Aging was done using acetic acid 4% for both groups. Color and translucency were measured using a spectrophotometer before and after artificial aging. Flexural strength was measured using a universal testing machine before and after aging. Data were collected, tabulated, and statistically analyzed. Results: Color change of both pre-shaded and liquid-shaded zirconia were within the clinically acceptable range (1.7±0.3) and (1.9±0.3) respectively and there was no significant difference in translucency between both groups' P value (0.253). Flexural strength increased from (921.9±73.3) before aging to (1025.1±178.5) after aging with pre-shaded zirconia while it decreased from (938.6±32.7) before aging too (899±54.5) after aging with liquid shaded zirconia but this difference was statistically non-significant. Conclusion: The shading technique had no noticeable effect on color, translucency, or flexural strength before or after aging.
Ceramics International, 2017
The fabrication of zirconia dental restorations is a time-consuming process due to traditional slow sintering schemes; zirconia (Y-TZP) produced by these conventional routes are predominantly opaque. Novel speed sintering protocols have been developed to meet the demand for time and cost effective chairside CAD/CAM-produced restorations, as well as to control ceramic microstructures for better translucency. Although the speed sintering protocols have already been used to densify dental Y-TZP, the wear properties of these restorations remain elusive. Fast heating and cooling rates, as well as shorter sintering dwell times are known to affect the microstructure and properties of zirconia. Thus, we hypothesize that speed sintered zirconia dental restorations possess distinct wear and physical characteristics relative to their conventionally sintered counterparts. Glazed monolithic molar crowns of translucent Y-TZP (inCoris TZI, Sirona) were fabricated using three distinct sintering profiles: Super-speed (SS, 1580 °C, dwell time 10 min), Speed (S, 1510 °C, dwell time 25 min), and Long-term (LT, 1510 °C, dwell time 120 min). Microstructural, optical and wear properties were investigated. Crowns that were super-speed sintered possessed higher translucency. Areas of mild and severe wear were observed on the zirconia surface in all groups. Micropits in the wear crater were less frequent for the LT group. Groups S and SS exhibited more surface pits, which caused a scratched steatite surface that is associated with a greater volume loss. Tetragonal to monoclinic phase transformation, resulting from the sliding wear process, was present in all three groups. Although all test groups had withstood thermo-mechanical challenges, the presence of hairline cracks emanating from the
Molecules
Translucent zirconia is becoming the material of choice for the esthetic restorative material. We aimed to evaluate the surface structure, phase determination, translucency, and flexural strength of 5Y-TZP Zirconia (Katana STML Block and Disc) between the regular sintering and the speed sintering with and without low-temperature degradation (LTD). A total of 60 zirconia discs (30 per group; regular sintering and speed sintering) were used in this study. A CAM machine was used to mill cylinders out of the zirconia blanks and then cut into smaller discs. For the speed sintering, the zirconia blocks were milled into smaller discs. The zirconia discs were subjected to regular and speed sintering with and without LTD. Scanning electron microscopy was used to characterize the zirconia specimens and the zirconia grain size. Furthermore, the zirconia specimens were analyzed for elemental analysis using energy dispersive spectroscopy and phase identification using X-ray diffraction. The zirc...