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1.
Shinobu Yamauchi Shoko Miura Shin Kasahara Jirun Sun Hiroshi Egusa 《Journal of prosthodontic research》2019,63(2):184-192
Purpose
To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics.Methods
Layering and pressable ceramics without frames or on 0.8- and 1.2-mm-thick Y-TZP frames were fired with 5 schedules (normal and 4 customized conditions). The fracture toughness of the ceramics was measured at 0.5–2.5 mm from the frame by the indentation fracture method. Crystal structures at the measurement points were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Results
Under customized firing conditions, the fracture toughness of the layering ceramic significantly decreased, particularly near the frame. Use of a 1.2-mm-thick frame significantly decreased the fracture toughness of both layering and pressable ceramics compared to ceramics without the frame. The decreased fracture toughness only occurred close (0.5 and 1.0 mm) to the frame. XRD analysis showed identical diffraction patterns between points near and far from the frame, suggesting that the decreased fracture toughness was not due to crystal defects or impurities. SEM revealed many microcracks and large crystals in layering ceramic near the 1.2-mm-thick frame, possibly resulting from the thermal properties of the zirconia frame, such as large heat capacity and low thermal conductivity.Conclusions
Modification of the firing conditions from the manufacturer’s instructions and inclusion of a thick Y-TZP frame decreased the fracture toughness of veneering ceramics at the interface, suggesting that a thick frame would pose a potent fracture risk in veneering ceramics used for zirconia-based all-ceramic restorations. 相似文献2.
OBJECTIVES: The purpose of the current study was to examine the influence of simulated masticatory loading regimes, to which all-ceramic crown or bridge restorations will routinely be subjected during their service-life, on the performance of a yttria-stabilised tetragonal zirconia polycrystalline (Y-TZP) dental ceramic. METHODS: Ten sets of 30 Y-TZP ceramic discs (13 mm diameter, 1.48-1.54 mm thickness) supplied by the manufacturer were randomly selected. Six groups were loaded for 2000 cycles at 500 N (383-420 MPa), 700N (536-588 MPa) and 800 N (613-672 MPa) with three groups maintained dry and the remaining three groups loaded while immersed in water at 37+/-1 degrees C. A further two groups underwent extended simulated masticatory loading regimes at 80 N (61-67 MPa) for 10(4) and 10(5)cycles under dry conditions. The mean bi-axial flexure strengths, standard deviations and associated Weibull moduli (m) were determined. The surface hardness was also determined using the Vickers hardness indentation technique. RESULTS: No significant difference (P>0.05) was identified in the bi-axial flexure strength of the simulated masticatory loading regimes and the control specimens loaded dry or wet. A significant increase in m was identified for the Y-TZP specimens following loading while immersed in water (8.6+/-1.6, 8.5+/-1.6 and 10.3+/-1.9) compared with the control (7.1+/-1.3). However, the extended loading regime to 10(5)cycles resulted in a significant reduction in the m of the Y-TZP specimens (5.3+/-1.0) compared with the control. Localised areas of increased surface hardness were identified to occur directly beneath the spherical indenter. CONCLUSIONS: The occurrence of localised areas of increased surface hardness could be the result of either a transformation toughening mechanism or crushing and densification of the material beneath the indentor manifested as the formation of a surface layer of compressive stresses that counteracted the tensile field generated at the tip of a propagating crack which increased the Weibull modulus of the Y-TZP specimens. The reduced reliability of the Y-TZP specimens loaded to 80 N for 10(5)cycles was associated with the accumulation of subcritical damage as a result of the extended nature of loading. 相似文献
3.
The fracture strengths of stylized all-ceramic crowns manufactured using an yttrium-oxide-partially-stabilized (Y-TZP) zirconia ceramic core (Denzir) veneered with lithium disilicate glass-ceramics (IPS Empress 2 or IPS Eris) were evaluated. The Denzir cores were manufactured in two ways: either with different thickness in different parts of the restoration, called an 'adapted Denzir core'; or with a uniform core thickness of 0.5 mm. IPS Empress 2 all-ceramic crowns served as reference. There was no significant difference between the crowns with an 'adapted Denzir core' veneered with the two brands of glass-ceramics. No significant difference was seen between the crowns with a 0.5 mm Denzir core veneered with the two brands of glass-ceramics. The crowns with an 'adapted Denzir core' exhibited significantly higher values than those with a 0.5 mm Denzir core and than the IPS Empress 2 crowns used as reference. No significant differences were seen among the IPS Empress 2 crowns used as reference and the crowns with a 0.5 mm Denzir core. The mode of failure varied among the Empress 2 crowns and the crowns with a core of a Y-TZP zirconia ceramic. Long-term studies are necessary to assess the clinical performance of this restorative system. 相似文献
4.
《Dental materials》2014,30(10):1195-1203
ObjectiveThe aim of this study was to provide a design guideline for developing tetragonal yttria-stabilized zirconia with improved translucency.MethodsThe translucency, the in-line transmission in particular, of 3 mol.% yttria-stabilized tetragonal zirconia (3Y-TZP) has been examined using the Rayleigh scattering model. The theory predicts that the in-line transmission of 3Y-TZP can be related to its thickness with grain size and birefringence the governing parameters. To achieve a threshold value of translucency, the critical grain size of 3Y-TZP was predicted for various thicknesses (0.3–2.0 mm). The threshold value was defined by a measured average in-line transmission value of a suite of dental porcelains with a common thickness of 1 mm. Our theoretical predictions were calibrated with one of the very few experimental data available in the literature.ResultsFor a dense, high-purity zirconia, its in-line transmission increased with decreasing grain size and thickness. To achieve a translucency similar to that of dental porcelains, a nanocyrstalline 3Y-TZP structure was necessitated, due primarily to its large birefringence and high refractive index. Such a grain size dependence became more pronounced as the 3Y-TZP thickness increased. For example, at a thickness of 1.3 mm, the mean grain size of a translucent 3Y-TZP should be 82 nm. At 1.5 mm and 2 mm thicknesses, the mean grain size needed to be 77 nm and 70 nm, respectively.SignificanceA promising future for zirconia restorations, with combined translucency and mechanical properties, can be realized by reducing its grain size. 相似文献
5.
Merve Banko?lu Güng?r Handan Y?lmaz Cemal Ayd?n Se?il Karakoca Nemli Bilge Turhan Bal Tülay T?ra? 《The journal of advanced prosthodontics》2014,6(3):224-232
PURPOSE
The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials.MATERIALS AND METHODS
Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data.RESULTS
The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05).CONCLUSION
It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials. 相似文献6.
Objective. This study aimed to investigate the effects of different mechanical surface treatments of pre-sintered zirconium oxide (ZrO2) in an attempt to improve its bonding potential. Materials and methods. One hundred and twenty IPS e-max ZirCAD (Ivoclar Vivadent) pre-sintered zirconia blocks (7 mm diameter, 3 mm height) received six different surface treatments (n = 20): Group C was untreated (control); Group E was Er:YAG laser irradiated; Group N was Nd:YAG laser irradiated; Group SB was sandblasted, Group SN was sandblasted and Nd:YAG laser irradiated; and Group SE was sandblasted and Er:YAG laser irradiated. After the surface treatments, the average surface roughness (Ra, µm) of each specimen was determined with a profilometer, then all the specimens were sintered. The surface roughness values were analysed through one-way ANOVA and Tukey's test. Changes in the morphological characteristics of ZrO2 were examined through scanning electron microscopy (SEM). Results. Sintered sandblasted, Er:YAG laser treatment, sandblasted + Er:YAG laser and sandblasted + Nd:YAG laser irradiation resulted in a rougher surface than the other treatments. Conclusion. Nd:YAG laser irradiation alone was not effective in altering the zirconia surface morphology. 相似文献
7.
氧化铝纤维对牙科氧化锆陶瓷机械性能的影响 总被引:1,自引:0,他引:1
目的:氧化铝纤维增强牙科氧化锆陶瓷并测试其性能.方法:将氧化铝纤维按不同质量分数添加到牙科氧化锆粉体中烧结成陶瓷,测试不同氧化铝纤维含量对牙科氧化锆陶瓷强度的影响.结果:添加5%的氧化铝纤维所烧结的牙科复合陶瓷达到最好的力学性能,其抗弯强度(MPa)达到321.02±25.48.结论:添加5%氧化铝纤维的牙科复合氧化锆... 相似文献
8.
Hee-Kyung Kim Sung-Hun Kim Jai-Bong Lee Jung-Suk Han In-Sung Yeo Seung-Ryong Ha 《The journal of advanced prosthodontics》2016,8(1):37-42
PURPOSE
This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics.MATERIALS AND METHODS
One-hundred sixty-five monolithic zirconia specimens (16.3 mm × 16.3 mm × 2.0 mm) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (ΔE*ab) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffé test (α=.05).RESULTS
There were significant differences in CIE L* between Subgroup 0 and other subgroups in all groups. CIE a* increased (0.52<R2<0.73), while CIE b* decreased (0.00<R2<0.74) in all groups with increasing thickness reduction. Perceptible color differences (ΔE* ab>3.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups (R2>0.89, P<.001).CONCLUSION
Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics. 相似文献9.
The aim of the study was to evaluate the effect of amnesia in preschool children on their later acceptance of dental care. Forty-six 4-6-year-old children, who between 2 and 4 years previously had had primary incisors extracted because of trauma, were reexamined for dental health and acceptance of dental care. The extractions had been performed under rectal sedation with diazepam (0.7 mg/kg body weight). Information about dental treatment and degree of cooperation during the intervening period was obtained from records at the referring clinic. The parents were interviewed about their child's experience of amnesia concerning the extractions, background variables, and experiences of dental care before the follow-up examination. Amnesia concerning the extractions was reported in 85% of the children. Twenty-nine percent had on some occasion exhibited behavior management problems (BMP) during the intervening period. Lack of amnesia was significantly associated with BMP (P < 0.002). Children without amnesia concerning the extractions tended to accept dental care less well at the reexamination. Parents were able to predict their child's acceptance of dental care at the follow-up with a significant degree of success (P = 0.02). In conclusion, amnesia in preschool children concerning extractions seems to be essential to facilitate positive acceptance of future dental care. 相似文献
10.
Alexandra Grigore Stefanie Spallek Anselm Petschelt Benjamin Butz Erdmann Spiecker Ulrich Lohbauer 《Dental materials》2013