The crystallinity of lithium aluminosilicate(LAS) glass after crystallization were studied at different temperatures by X-ray diffractometry and the crystallinity of the standard glass ceramic with known crystal and g...The crystallinity of lithium aluminosilicate(LAS) glass after crystallization were studied at different temperatures by X-ray diffractometry and the crystallinity of the standard glass ceramic with known crystal and glass phases was examined. The crystallization mechanism of LAS glass was analyzed by the crystallinity, with a formula relating the crystallinity (X) and temperature (T). The results show that the calculated crystallinity of LAS glass by XRD increases with the crystallization temperature, in the range of 40%?50%, which is close to the calculated ones of standard samples with spodumene quartz ratio of 40%?70%. The activation energy of LAS glass is different within different temperature ranges; nEc is 125.44 kJ/mol at 710?810 ℃ and nEc is 17.42 kJ/mol at 810?980 ℃, which indicates different crystallization mechanisms. It has been proved that the required energy for crystallization of glass in the lower temperature range includes the interfacial energy between glass and crystalline phase and the free energy difference of atoms in structures of glass and crystal, and in the higher temperature ranges only the interfacial energy between glass and crystalline phase is considered.展开更多
The novel dental ceramics can be fabricated at lower temperatures when sol-gel derived lithium disilicate glass ceramics(LDGC)was used as an additive for yttria stabilized tetragonal zirconia polycrystalline(Y-TZP)cer...The novel dental ceramics can be fabricated at lower temperatures when sol-gel derived lithium disilicate glass ceramics(LDGC)was used as an additive for yttria stabilized tetragonal zirconia polycrystalline(Y-TZP)ceramics.The effect of LDGC on the sintering,mechanical,and translucent properties of Y-TZP ceramics was investigated in the present study.The results showed that the LDGC additive effectively improved the densification of Y-TZP at 1100℃,which was much lower than the sintering temperature for pure Y-TZP.When sintered at 1100℃,the Y-TZP with 1 wt%LDGC reached a relative density of 95.45%,and prossessed a flexural strength of 482.4 MPa and a fracture toughness of 5.94 MPa-m12.Moreover,its translucency was also improved.While,the addition of LDGC could result in an escape of yttrium atoms from the grain lattice of zirconia,which induced the tetragonal-monoclinic transformation of zirconia and abnormal growth of monoclinic grains.The escaped yttrium atoms diffused into the intergranular glass phase.The results indicated that the novel Y-TZP-LDGC ceramics has a great potential to be used for all-ceramic restorations.展开更多
目的：探讨CEREC椅旁计算机辅助设计（computer aided design,CAD）精确地确定冠边缘位置的方法。方法：报告1例采用CAD/CAM IPS e.max瓷块修复前牙（11、21）牙体缺损的病例,按照改良的美国公共卫生署（United States Public Health Se...目的：探讨CEREC椅旁计算机辅助设计（computer aided design,CAD）精确地确定冠边缘位置的方法。方法：报告1例采用CAD/CAM IPS e.max瓷块修复前牙（11、21）牙体缺损的病例,按照改良的美国公共卫生署（United States Public Health Service,USPHS）标准评价临床疗效。牙体预备后,通过CEREC口内扫描仪测量排龈前后游离龈缘（FGM）的变化。结果：取出排龈线30min后,FGM的变化趋于稳定,11和21的FGM分别根向退缩了0.2mm。各阶段复查结果表明：患牙无折断、劈裂及继发龋等不良现象。临床指标均达到A级标准。结论：二矽酸锂玻璃陶瓷用于前牙牙体缺损的修复可以取得理想的美学效果,远期疗效有待进一步观察。CEREC椅旁CAD精确设计冠边缘的位置方法可用于临床。展开更多
基金Project(2003C11030) supported by the High Science & Technique Brainstorm of Zhejiang Province, China
文摘The crystallinity of lithium aluminosilicate(LAS) glass after crystallization were studied at different temperatures by X-ray diffractometry and the crystallinity of the standard glass ceramic with known crystal and glass phases was examined. The crystallization mechanism of LAS glass was analyzed by the crystallinity, with a formula relating the crystallinity (X) and temperature (T). The results show that the calculated crystallinity of LAS glass by XRD increases with the crystallization temperature, in the range of 40%?50%, which is close to the calculated ones of standard samples with spodumene quartz ratio of 40%?70%. The activation energy of LAS glass is different within different temperature ranges; nEc is 125.44 kJ/mol at 710?810 ℃ and nEc is 17.42 kJ/mol at 810?980 ℃, which indicates different crystallization mechanisms. It has been proved that the required energy for crystallization of glass in the lower temperature range includes the interfacial energy between glass and crystalline phase and the free energy difference of atoms in structures of glass and crystal, and in the higher temperature ranges only the interfacial energy between glass and crystalline phase is considered.
基金supported by the Shanghai Committee of Science and Technology,China(No.17441904100).
文摘The novel dental ceramics can be fabricated at lower temperatures when sol-gel derived lithium disilicate glass ceramics(LDGC)was used as an additive for yttria stabilized tetragonal zirconia polycrystalline(Y-TZP)ceramics.The effect of LDGC on the sintering,mechanical,and translucent properties of Y-TZP ceramics was investigated in the present study.The results showed that the LDGC additive effectively improved the densification of Y-TZP at 1100℃,which was much lower than the sintering temperature for pure Y-TZP.When sintered at 1100℃,the Y-TZP with 1 wt%LDGC reached a relative density of 95.45%,and prossessed a flexural strength of 482.4 MPa and a fracture toughness of 5.94 MPa-m12.Moreover,its translucency was also improved.While,the addition of LDGC could result in an escape of yttrium atoms from the grain lattice of zirconia,which induced the tetragonal-monoclinic transformation of zirconia and abnormal growth of monoclinic grains.The escaped yttrium atoms diffused into the intergranular glass phase.The results indicated that the novel Y-TZP-LDGC ceramics has a great potential to be used for all-ceramic restorations.
文摘目的：探讨CEREC椅旁计算机辅助设计（computer aided design,CAD）精确地确定冠边缘位置的方法。方法：报告1例采用CAD/CAM IPS e.max瓷块修复前牙（11、21）牙体缺损的病例,按照改良的美国公共卫生署（United States Public Health Service,USPHS）标准评价临床疗效。牙体预备后,通过CEREC口内扫描仪测量排龈前后游离龈缘（FGM）的变化。结果：取出排龈线30min后,FGM的变化趋于稳定,11和21的FGM分别根向退缩了0.2mm。各阶段复查结果表明：患牙无折断、劈裂及继发龋等不良现象。临床指标均达到A级标准。结论：二矽酸锂玻璃陶瓷用于前牙牙体缺损的修复可以取得理想的美学效果,远期疗效有待进一步观察。CEREC椅旁CAD精确设计冠边缘的位置方法可用于临床。
