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- Okada, S, et al.
(författare)
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Synthesis and investigation of large crystals of (Cr1-xTMx)(3)B-4 with TM = Ti, V, Nb, Ta, Mo, and W
- 2000
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Ingår i: JOURNAL OF SOLID STATE CHEMISTRY. - : ACADEMIC PRESS INC. - 0022-4596. ; 154:1, s. 45-48
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of the ternary borides (Cr1-xTMx)(3)B-4 (TM = Ti, V, Nh, Ta, Mo, W) were grown by the flux method using molten aluminum as a solvent, The substances were subjected to chemical analyses and measurements of the unit cell parameters. Crystals
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| 4. |
- Harada, A., et al.
(författare)
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Mechanical and microstructural properties of ultra-translucent dental zirconia ceramic stabilized with 5 mol% yttria
- 2020
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Ingår i: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic dental prostheses fabricated from 3 mol.% yttria-stabilized zirconia (3YZ) are becoming increasingly popular. Recently, 5 mol.% yttria-stabilized zirconia (5YZ) which significantly improves the translucency of 3YZ has been prepared. However, its mechanical and microstructural properties, especially those affected by low-temperature degradation (LTD), have not been fully elucidated yet. The objective of the present study was to establish the relationship between the flexural strength of 5YZ with or without autoclave-induced LTD and its microstructural properties. For this purpose, a total of 320 bar-shaped specimens were cut from 5YZ and 3YZ blocks, and half of the specimens in each group were autoclaved at 134 °C for 50 h. Their flexural strengths were determined by conducting three-point bending tests, and the obtained results were analyzed by the Weibull statistical method. Grain sizes and crystalline structures of the specimens were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, respectively. Additionally, the LTD-induced phase transformation was examined by Raman microscopy and cross-sectional surface analysis. The characteristic strengths of 5YZ and 3YZ were approximately 620 and 950 MPa, respectively, and 5YZ was found to be more resistant to LTD in terms of phase transformation than 3YZ. However, a low amount of the monoclinic phase was detected even in 5YZ after 50 h of autoclaving, which significantly decreased its flexural strength and reliability. The results of SEM analysis revealed that 5YZ was composed of two distinct regions: a dominant matrix with large grains (median size: 0.8 μm) and scattered areas with small grains (median size: 0.4 μm). Phase transformation analysis and fractography data indicated that the small-grain region was strongly affected by LTD and likely represented a fracture origin. The described properties should be considered during the clinical application of monolithic 5YZ dental prostheses. © 2020 Elsevier Ltd
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| 5. |
- Nakamura, K., et al.
(författare)
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Reactions of dental pulp to hydrogen peroxide photolysis-based antimicrobial chemotherapy under ultraviolet-A irradiation in rats
- 2020
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Ingår i: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen peroxide photolysis-based antimicrobial chemotherapy that utilizes ultraviolet-A irradiation (UVA-H2O2 photolysis) has been previously proposed as a method of treatment of cariogenic biofilm. Therefore, in the present study, we aimed to assess time-dependent reactions in the dental pulp of rats after UVA-H2O2 photolysis. Maxillary first molars were treated. UVA irradiation (wavelength: 365 nm) with 3 wt% H2O2 was performed for 90 s at a radiant emittance of 500-2000 mW/cm(2) on the rats for 3 consecutive days or only 1 day. The animals were sacrificed at Days 1, 3, 7, and 21 after the treatment for the histological evaluation of inflammatory cells and immunohistochemistry of heat shock protein (HSP)-25, a marker of odontoblasts. Tertiary dentin formation was evaluated at Day 21 by histomorphometry and micro-CT analysis. UVA-H2O2 photolysis elicited little infiltration of inflammatory cells, but disturbances in the odontoblast layer and/or presence of localized degenerative tissue were observed on Day 3. This condition was followed by a healing process that was characterized by the reappearance of HSP-25 positive odontoblast-like cells at Day 7 and tertiary dentin formation at Day 21. The amount of tertiary dentin formed was dependent on the intensity of treatment; repeated UVA irradiations of H(2)O(2 )at 2000 mW/cm(2) resulted in the largest amount of tertiary dentin formation at the pulp horn regions. Our findings suggest that UVA-H2O2 photolysis treatment can be used to treat dental caries clinically because the post-treatment inflammatory reaction was minimal and tertiary dentin formation was substantial, which may prove effective in protecting dental pulp from external irritants. As a cautionary consideration, the radiant emittance of the UVA irradiation should be carefully optimized before clinical application.
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