Effect of sintering time on biaxial strength of zirconium dioxide

Hjerppe, Jenni; Vallittu, Pekka K.; Fröberg, Kaj; Lassila, Lippo

doi:10.1016/j.dental.2008.05.011

Cited by 96 publications

(97 citation statements)

References 21 publications

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“…In that study, interestingly after aging in water even increased values were found (1308 MPa (Hjerppe et al, 2009). In the clinical situations, the presence of dentin under a zirconia FDP and sealing the two materials with a cement layer may yield to more favorable stress distribution than testing an unsupported disc specimen under flexural load according to ISO norms.…”

Section: Discussionmentioning

confidence: 64%

Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading

Özcan

Melo

Souza

et al. 2013

Journal of the Mechanical Behavior of Biomedical Materials

104

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This study evaluated the effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading. Disc-shaped zirconia specimens (Ø: 15mm, thickness: 1.2mm) (N=32) were submitted to one of the air-particle abrasion protocols (n=8 per group): (a) 50 m Al2O3 particles, (b) 110 m Al2O3 particles coated with silica (Rocatec Plus), (c) 30 m Al2O3 particles coated with silica (CoJet Sand) for 20s at 2.8bar pressure. Control group received no air-abrasion. All specimens were initially cyclic loaded (×20,000, 50N, 1Hz) in water at 37°C and then subjected to biaxial flexural strength testing where the conditioned surface was under tension. Zirconia surfaces were characterized and roughness was measured with 3D surface profilometer. Phase transformation from tetragonal to monoclinic was determined by Raman spectroscopy. The relative amount of transformed monoclinic zirconia (FM) and transformed zone depth (TZD) were measured using XRD. The data (MPa) were analyzed using ANOVA, Tukey's tests and Weibull modulus (m) were calculated for each group (95% CI). The biaxial flexural strength (MPa) of CoJet treated group (1266.3±158(A)) was not significantly different than that of Rocatec Plus group (1179±216.4(A,B)) but was significantly higher than the other groups (Control: 942.3±74.6(C); 50 m Al2O3: 915.2±185.7(B,C)). Weibull modulus was higher for control (m=13.79) than those of other groups (m=4.95, m=5.64, m=9.13 for group a, b and c, respectively). Surface roughness (Ra) was the highest with 50 m Al2O3 (0.261 m) than those of other groups (0.15-0.195 m). After all air-abrasion protocols, FM increased (15.02%-19.25%) compared to control group (11.12%). TZD also showed increase after air-abrasion protocols (0.83-1.07 m) compared to control group (0.59 m). Air-abrasion protocols increased the roughness and monoclinic phase but in turn abrasion with 30 m Al2O3 particles coated with silica has increased the biaxial flexural strength of the tested zirconia. 942.3±74.6 C ; 50 µm Al 2 O 3 : 915.2±185.7 B,C ). Weibull modulus was higher for control (m=13.79) than those of other groups (m=4. 95, m=5.64, m=9.13 for group a, b and c, respectively). Surface roughness (R a ) was the highest with 50 µm Al 2 O 3 (0.261 µm) than those of other groups (0.15-0.195 µm). After all air-abrasion protocols, F M increased (15.02-19.25%) compared to control group (11.12%). TZD also showed increase after air-abrasion protocols (0.83-1.07 µm) compared to control group (0.59 µm). Air-abrasion protocols increased the roughness and monoclinic phase but in turn abrasion with 30 µm Al 2 O 3 particles coated with silica has increased the biaxial flexural strength of the tested zirconia.

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Section: Discussionmentioning

confidence: 64%

Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading

Özcan

Melo

Souza

et al. 2013

Journal of the Mechanical Behavior of Biomedical Materials

104

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“…Future studies therefore should provide at least 95% CI if not global test results for the estimates, as the absolute values cannot be analysed without any information on 95% CI reliably. At this stage, the results of this study cannot be compared with those of others due to the lack of information on the estimation methods and 95% CI (Hjerppe et al, 2009;Ashkanani et al,2008). Nevertheless, estimation methods should be taken into consideration when interpreting data limited number of specimens.…”

Section: Discussionmentioning

confidence: 93%

“…Only a few studies described how Weibull analysis for flexural strength measurements of ceramics was performed (Bona et al, 2003). In the majority of the studies, it was stated that the variability of the flexural strength values was determined by Weibull-analysis or Weibull analysis was performed for all of the groups (Hjerppe et al, 2009;Ashkanani et al,2008) without mentioning whether LS/ML was used or not. When LS is used, definition of the plotting positions has to be explicitly described (mean or median rank).…”

Section: Discussionmentioning

confidence: 99%

Evaluation of flexural strength of hipped and presintered zirconia using different estimation methods of Weibull statistics

Stawarczyk¹,

Özcan²,

Trottmann³

et al. 2012

Journal of the Mechanical Behavior of Biomedical Materials

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OBJECTIVES: This study determined the flexural strength of one hipped and eight presintered zirconia and evaluated the results using different estimation methods of Weibull statistics. MATERIALS AND METHODS: Presintered zirconia specimens were prepared in white state and sintered according to each manufacturer's instructions. One hipped zirconia acted as the control group. The specimens were loaded in a Universal Testing Machine (ISO 6872, 2008). Data were analysed using "normal" (Levene test, one-way ANOVA, Scheffé test) and "Weibull distribution" estimated by either Least Squares (LS) (mean (Excel) and median rank (MINITAB)), Maximum Likelihood (ML) (MINITAB) or ML (MINITAB) with a correction of BS EN 843-5 (2006) (862; 1009)). The highest Weibull modulus estimated by LS for mean and median rank was observed with LZ (8.9 and 9.8(7.5; 12.9), respectively) and the lowest with ZE (5.1 and 5(3; 8.2), respectively). According to ML and MLC estimation, the control group showed the highest (10.1(6.6; 15.6), 9.2(5.8; 14.2), respectively), and CZ the lowest (5.6(3.8; 8.2), 5.0(3.2; 7.8), respectively) Weibull modulus. No differences in estimates of standard deviations of the normal distribution and the estimates of Weibull moduli for different estimation methods were found between all tested groups. CONCLUSIONS: Flexural strength of the tested hipped zirconia was higher than those of presintered ones according to both normal and Weibull distribution. LS (median rank) and ML estimates can be compared by a global test and by means of 95% CI. For corrected ML estimates the 95% CI can be interpreted. Estimate calculations in Excel (LS, mean rank) provides information on 95% CI for the Weibull parameters. (862;1009)). The highest Weibull modulus estimated by LS for mean and median rank was observed with LZ (8.9 and 9.8(7.5;12.9), respectively) and the lowest with ZE (5.1 and 5(3;8.2), respectively).According to ML and MLC estimation, the control group showed the highest (10.1(6.6;15.6), 9.2(5.8;14.2), respectively), and CZ the lowest (5.6(3.8;8.2), 5.0(3.2;7.8), respectively) Weibull modulus. No differences in estimates of standard 3 deviations of the normal distribution and the estimates of Weibull moduli for different estimation methods were found between all tested groups.Conclusions: Flexural strength of the tested hipped zirconia was higher than those of presintered ones according to both normal and Weibull distribution. LS (median rank) and ML estimates can be compared by a global test and by means of 95% CI. For corrected ML estimates the 95% CI can be interpreted. Estimate calculations in EXCEL (LS, mean rank) provides on information on 95% CI for the Weibull parameters.

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“…Translucency of zirconia can be affected by sintering parameters [26]. It has been previously reported that during sintering process, the heat rate did not show an influence on the mechanical properties of zirconia [27]. On the other hand, one study showed that the holding time during the sintering process caused grain expansion [28].…”

Section: Introductionmentioning

confidence: 99%

The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio

et al. 2012

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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 (N = 198; n = 22 per group) was measured according to ISO 6872: 2008. The contrast ratio (N = 90; n = 10 per group) was measured according to ISO 2471ISO : 2008. Grain sizes and microstructure of different groups were investigated (N = 9, n = 1 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 (r = -0.313, p < 0.001) and the contrast ratio values (r = -0.96, p < 0.001). CONCLUSIONS: The results of this study showed that the increase in sintering temperature increased the contrast ratio, but led to a negative impact on the flexural strength. CLINICAL RELEVANCE: Considering the flexural strength values and Weibull moduli, the sintering temperature for the zirconia tested in this study should not exceed 1,550°C. 20]. In fact, the stability of the complete system consisting both the zirconia framework and the veneering ceramic is of clinical importance.In order to decrease the costs and at the same time overcome the chipping problem, it is possible today to produce zirconia FDPs without veneering ceramic.Such monolithic zirconia FDPs require higher translucency with superior mechanical properties especially when they are to be used in the anterior region. Framework translucency is therefore one of the primary factors with respect to aesthetic properties in the selection of dental materials [21,22]. The translucency of dental ceramic is highly dependent on light scattering [23]. When the majority of light passing through a ceramic is intensely scattered and diffusely reflected, the material would appear opaque. However, if only part of the light is scattered and most of it is diffusely transmitted, the material would appear translucent where Y B was the value with a black background, and Y w was the value with a white background. In all calculations, 0 was considered as totally transparent and 1 as

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Effect of sintering time on biaxial strength of zirconium dioxide

Cited by 96 publications

References 21 publications

Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading

Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading

Evaluation of flexural strength of hipped and presintered zirconia using different estimation methods of Weibull statistics

The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio

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