一种新型牙科二硅酸锂玻璃陶瓷的微观结构分析

目的:分析牙科二硅酸锂玻璃陶瓷的微观结构,探讨其可能的自增韧机制。方法:使用X射线衍射仪分析一种新型二硅酸锂玻璃陶瓷及IPS e.max Press LT和MO瓷块的物相组成,并使用扫描电镜观察其表面特征和裂纹扩展方式。结果:3种玻璃陶瓷的主晶相均为Li2Si2O5,次晶相均为Li2SiO3和Li3PO4。Li2Si2O5晶体均呈棒状,交错排列,形成互锁微结构。新型玻璃陶瓷的晶体尺寸大于LT和MO瓷块,其表面孔隙缺陷较后两者少而深。裂纹在这3种玻璃陶瓷中主要沿着晶体间较薄弱的玻璃相扩展。结论:新型玻璃陶瓷与IPS e.max Press LT和MO瓷块的微观结构相似,长棒状的Li2Si2O5晶体所形成的互锁微结构,以及内部的残余应力可对其起到增强增韧的作用。     

二次熔融烧结法制备牙科用可切削云母基玻璃陶瓷

目的:通过二次熔融烧结法制备以云母为主晶相的牙科用可切削玻璃陶瓷。方法:在1500℃下熔融K2O-MgO-Al2O3-SiO2-F系统基础玻璃,其玻璃粉经过冷等静压成型后无压烧结获得牙科用可切削玻璃陶瓷。采用DTA-TGA确定基础玻璃的核化和晶化温度,采用XRD和SEM分析烧结体的物相组成和微观形貌,以及采用三点弯曲法和压痕法测定烧结体的力学性能。结果:K2O-MgO-Al2O3-SiO2-F系统的核化温度和晶化温度分别选择680℃和1020℃。烧结体的整体析晶比较缓慢,结晶度约为35.48%,主晶相为氟硅云母,晶体呈立方或扁平状,交错排列。烧结体的弯曲强度和断裂韧性分别为(144.50±9.75)MPa和(1.25±0.26)MPa.m1/2。结论:二次熔融烧结法制备的云母基玻璃陶瓷能够满足临床牙体缺损修复的要求。     

一种通用粘接剂对不同CAD/CAM可切削材料的短期粘接成绩

[摘要] 目的 评估一种通用粘接剂对于三种不同类型的CAD/CAM可切削材料的短期粘接成绩。方法 制作氧化钇稳定四方相氧化锆陶瓷,纳米复合陶瓷和二硅酸锂玻璃陶瓷试件各20枚,其中前两者进行喷砂处理,后者进行HF酸蚀处理。各组陶瓷再分为2亚组,分别使用（SBU）或不使用（Ctr）通用粘接剂Single Bond Universal。以上表面处理瓷片与复合树脂柱通过树脂水门汀粘接,制作粘接试件,37℃水储24ｈ后测试剪切粘接强度并记录断裂模式。喷砂处理的氧化锆陶瓷和纳米复合陶瓷,以及酸蚀处理的二硅酸锂玻璃陶瓷通过扫描电镜（SEM）观察表面微观形态。结果SEM观察显示酸蚀处理的二硅酸锂玻璃陶瓷,喷砂处理的氧化锆陶瓷和纳米复合陶瓷相对于粗化处理前呈现出粗糙的表面形态。三种经粗化处理的材料使用通用粘接剂表面处理后,剪切强度较未使用者显著增强。结论 通用粘接剂Single Bond Universal能够增强氧化钇稳定四方相氧化锆陶瓷,纳米复合陶瓷和二硅酸锂玻璃陶瓷三种类型CAD/CAM可切削材料的短期粘接强度。     

离子交换强韧化效应对CAD/CAM二硅酸锂玻璃陶瓷机械性能的影响

目的:探究锂-钠离子交换强韧化效应对CAD/CAM二硅酸锂玻璃陶瓷机械性能的影响。方法:制作50个CAD/CAM二硅酸锂玻璃陶瓷圆片状试件,晶化、打磨及抛光后,用4种不同的熔融硝酸钠离子交换工艺进行处理(n=10),分别检测离子交换前后样品的双轴弯曲强度、维氏硬度和断裂韧性。设置未交换组为空白对照。结果:CAD/CAM二硅酸锂玻璃陶瓷经过4种离子交换工艺处理后,机械性能都能够显著提升,以385℃/32 h组的强韧化效果最佳。结论:通过低温长时间的离子交换处理可以显著提升CAD/CAM二硅酸锂玻璃陶瓷的机械性能。     

二硅酸锂玻璃陶瓷与牛牙釉质磨损性能的体外实验研究

目的:研究模拟口腔环境下牛牙釉质与二硅酸锂玻璃陶瓷的磨损特性.方法:将18个长8 mm、直径3 mm的二硅酸锂玻璃陶瓷圆柱作为上颌磨头,分别与下颌二硅酸锂玻璃陶瓷或牛牙釉质试件配副,每组9个样本,利用摩擦磨损试验机,在人工唾液、室温环境、10 N载荷、转速100 r/min、回转半径2.5 mm、匀速圆周运动的条件下进行54万次循环磨损实验.在整个磨损周期中选取10个循环节点,用三维形貌仪测量每个节点下颌试件的磨损高度损失量并绘制相应磨损曲线,扫描电镜观察相应磨损阶段对应的磨损面微观形貌.结果:各循环节点牛牙釉质的磨损量均大于二硅酸锂玻璃陶瓷的磨损量(P＜0.05);实验循环周期内,牛牙釉质的磨损曲线呈现出“跑合期”、“稳定磨损期”、“剧烈磨损期”3个磨损阶段,而二硅酸锂玻璃陶瓷的磨损曲线呈现“跑合期”和“稳定磨损期”两个磨损阶段.2组的微观形貌也呈现出与磨损曲线相对应的阶段性动态衍化规律.结论:在模拟口腔环境下,牛牙釉质和二硅酸锂玻璃陶瓷的磨损行为均呈现出阶段性动态衍化规律;牛牙釉质的磨损量显著高于二硅酸锂的磨损量,提示应注意防止二硅酸锂玻璃陶瓷修复体对对颌天然牙的过度磨损.     

氧化磷含量对新型牙科玻璃陶瓷微观结构和强度的影响

目的：分析不同氧化磷含量对新型牙科二硅酸锂玻璃陶瓷微观结构和强度的影响。方法：通过调控Li2O、SiO2、K2O、Al2O3、ZrO2-P2O5玻璃系统中氧化磷（P2O5）的含量（0.5%,1.0%,1.5%和2.0%）,并进行相应的热处理,应用X射线衍射技术（XRD）,电子扫描显微术（SEM）分析制备的各组玻璃陶瓷的微观形貌,根据ISO6872标准测试玻璃陶瓷的弯曲强度,进行统计学分析。结果：各组玻璃陶瓷样本的主晶相均为二硅酸锂（Li2Si2O5）,随着P2O5含量的改变,析出晶体的形貌和分布有显著不同。1.0%组玻璃陶瓷具有最高的弯曲强度值。结论：通过调控P2O5含量,可制备具有高强度和适宜微观形貌的二硅酸锂玻璃陶瓷。     

氧化锆对二硅酸锂玻璃陶瓷力学性能的影响

目的:测定牙科氧化锆-二硅酸锂玻璃陶瓷复合材料(ZTCLDC)的力学性能,探讨氧化锆质量分数变化对ZTCLDC力学性能的影响及机制。方法:向制备好的二硅酸锂基础玻璃粉体中分别添加不同质量分数的ZrO(21%,2%,3%,4%),静压成型晶化热处理,每组中的半数试件进行牙科热压铸处理,分别测试热压铸前后的三点弯曲强度及断裂韧性;扫描电镜观察晶体微观结构;X射线衍射分析其晶相组成。结果:热压铸前,ZTCLDC抗弯强度和断裂韧性随ZrO2含量的增加而升高;热压铸后,ZTCLDC抗弯强度随ZrO2含量的增加而降低,ZrO2加入量为4%时,压铸后的断裂韧性最高为4.3 MPa.m1/2。结论:ZrO2对实验二硅酸锂玻璃陶瓷存在增韧效果,能够提高复合材料的断裂韧性。     

二硅酸锂和白榴石基玻璃陶瓷在模拟咀嚼循环下的耐磨性研究

目的：比较二硅酸锂和白榴石基玻璃陶瓷在模拟咀嚼循环的条件下磨损行为的演变。方法：采用热压铸造技术制备白榴石基玻璃陶瓷（IPS Empress Esthetic ETC1型铸瓷）和二硅酸锂玻璃陶瓷（IPS e．max Press HT型铸瓷）试件,分别与滑石瓷配副,磨损条件为加载力10 N、转速200 r／min,磨损进行100万转次,使用三维形貌扫描仪在每10转万次循环节点测量磨损体积量,扫描电镜观测表面微观形貌。结果：10万转次白榴石基陶瓷磨损量多于二硅酸锂陶瓷,20万至100万转次后两者没有统计学差异。白榴石基陶瓷表面犁沟与碎片剥脱后的粗糙面交错分布,二硅酸锂陶瓷表面以深且宽大的犁沟为主。随着时间的演变,两种陶瓷的犁沟状磨痕逐渐表浅。结论：白榴石基玻璃陶瓷在磨损初期磨损量多于二硅酸锂陶瓷,磨损中后期的磨损量没有显著性差异。     

二次烧结温度对牙科纳米氧化锆陶瓷抗弯强度影响的实验研究

目的研究二次烧结温度对纳米氧化锆陶瓷强度的影响。方法经初步烧结的氧化锆瓷块,在不同温度下进行第二次烧结,检测三点抗弯强度,X线衍射分析晶相,扫描电镜下观察试件的微观结构。结果当第二次烧结温度为1325℃时,材料的三点抗弯强度最高,达到(932±63)MPa。陶瓷主晶相为四方相,晶体大小均匀,排列紧密。结论经二次烧结的氧化锆瓷块具有足够的抗弯强度,能够满足口腔全瓷修复材料的要求。     

多次烧结对二硅酸锂玻璃陶瓷颜色和透光性的影响

目的 探究烧结次数对二硅酸锂玻璃陶瓷的颜色(△E)和透光性(τ)的影响。 方法 采用热压铸工艺制作二硅酸锂玻璃陶瓷(IPS e.max Press)片状试件(直径10mm,厚度1mm)30 个。打磨抛光后按照随机列表法将试件随机分为6 组,每组5 个。在烤瓷炉中分别烧结0(对照组)、1、2、3、4、5 次,用分光测色计和透光率测试仪分别测量各试件的色彩参数(L*a*b*)和透光性(τ), 并计算出色差(△E)。应用SPSS17.0 软件进行统计分析。每组中随机抽取2 个试件用X 线衍射仪(XRD) 分析其晶相组成。结果 试件反复烧结后的色差变化范围为0.88~2.45,明度值明显降低(P<0.05),a*、b*、τ 值明显增大(P<0.05)。 在多次烧结后试件的晶相保持不变,主晶相(Li₂Si₂O₅)的衍射峰强度增大。结论 烧结次数会影响二硅酸锂玻璃陶瓷基底冠的颜色和透光性,这可能与主晶相的晶体含量增加有关。     

Biaxial flexural strength and translucent characteristics of dental lithium disilicate glass ceramics with different translucencies

PurposeThe aim of this study was to evaluate the biaxial flexural strength and translucent characteristics of dental lithium disilicate glass ceramics with different translucencies.MethodsTwo heat pressed lithium disilicate glass ceramics (IPS e.max Press and an experimental ceramic) and one computer aided design/ computer aided manufacture (CAD/CAM) lithium disilicate glass ceramic (IPS e.max CAD) with different translucencies were evaluated. Disk-shaped specimens of each group were subjected to a biaxial flexural strength (BFS) test. Translucent parameters (TP) were also tested at 0.5 mm and 1.0 mm thickness, respectively. X-ray diffraction (XRD) and SEM were used for crystalline and microstructural analysis.ResultsBFS values of two heat pressed lithium disilicate glass ceramics were significantly higher than the CAD/CAM counterpart. No difference in BFS between two heat pressed glass ceramic was found. There were significant differences in BFS and TP values among the tested subgroups with different translucencies for IPS e.max Press and IPS e.max CAD. No difference in crystalline composition was found among the tested glass ceramics, but microstructure with shorter and wider crystal was revealed for IPS e.max CAD ceramics.ConclusionsLithium disilicate glass ceramics with different translucencies demonstrated different BFS and TP values.     

IPS-Empress 2 玻璃陶瓷结构及性能的研究

目的 研究新型IPS-Empress 2牙科高强度陶瓷的显微结构和机械性能。方法采用原子力显微镜、扫描电子显微镜和X射线衍射仪，分析IPS-Empress 2的显微结构和晶相，用三点弯曲实验和压痕法测试其弯曲强度和断裂韧性。结果IPS-Empress 2玻璃陶瓷主要由二硅酸锂晶体和磷酸锂晶体组成，二者形成相互交错的三维网络式结构；这种玻璃陶瓷在热压铸前后晶体相保持不变，其三点弯曲强度和断裂韧性分别为300MPa和3．1MPam^1/2。结论IPS-Empress 2玻璃陶瓷的高强度和韧性与高含量的二硅酸锂晶体、相互锁结的网络结构和裂纹偏转有关。     

Elastic constants, Vickers hardness, and fracture toughness of fluorrichterite-based glass-ceramics.

OBJECTIVES: To determine the elastic constants, Vickers hardness, and indentation fracture toughness of fluorrichterite glass-ceramics in the system SiO2-MgO-CaO-Na2O-K2O-F. METHODS: Five glass compositions were prepared with increasing sodium content. The compositions were melted at 1400 degrees C for 2 h and cast into 60 x 12 mm rods. Discs (1.5 x 12 mm) were cut from the glass rods, nucleated in the temperature range 600-650 degrees C for 1 h and crystallized at 900 degrees C for 0.5 h. The density of the glass-ceramics was measured by Archimedes' method. The elastic constants were determined by standard ultrasonic velocity technique. The fracture toughness was evaluated by the indentation technique. The indentation crack patterns and microstructure were investigated by scanning electron microscopy. The crystalline phases were identified by X-ray diffraction. A commercially available lithium disilicate glass-ceramic served as control. RESULTS: The fluorrichterite glass-ceramics containing 3.8 and 5.6 wt% sodium had the lowest mean fracture toughness. The glass ceramic containing 1.9 wt% sodium and the control material had the highest mean fracture toughness. The values obtained for these two materials (2.26 +/- 0.15 MPa m0.5 and 2.29 +/- 0.31 MPa m0.5, respectively), were not significantly different (p = 0.997). There was no linear relationship between the amount of sodium present in the glass-ceramic composition and the mean fracture toughness. The fluorrichterite glass ceramics exhibited a dual microstructure consisting of both fluorrichterite and mica crystals. SIGNIFICANCE: Higher fracture toughness appeared to be associated with a higher density of fluorrichterite crystals.     

Strength and microstructure of IPS Empress 2 glass-ceramic after different treatments

PURPOSE: This investigation was designed to determine whether heat pressing and/or simulated heat treatments affect the flexure strength and microstructure of the lithium disilicate glass-ceramic of the IPS Empress 2 system. MATERIALS AND METHODS: Four groups of the lithium disilicate glass-ceramic were prepared as follows: group 1 = as-received material; group 2 = heat-pressed material; group 3 = heat-pressed and stimulated initial heat-treated material; and group 4 = heat-pressed and simulated heat-treated material with full firings for a final restoration. Three-point bending tests and scanning electron microscopy (SEM) analysis were conducted. RESULTS: The flexure strength of group 2 was significantly higher than that of group 1. However, there were no significant differences in strength among groups 2, 3, and 4, or between groups 1 and 4. The SEM micrographs of the lithium disilicate glass-ceramic showed a closely packed, multidirectionally interlocking microstructure of numerous lithium disilicate crystals protruding from the glass matrix. The crystals in the glass matrix of the heat-pressed materials (groups 2, 3, and 4) were a little more homogeneous and about 2 times bigger than those of the as-received material (group 1). These changes of the microstructure were greatest between groups 1 and 2. However, there were no marked differences among groups 2, 3, and 4. CONCLUSION: Although there were significant increases in the strength and some changes of the microstructure after the heat-pressing operation, the combination of heat pressing and simulated subsequent heat treatments did not produce an increase of strength of IPS Empress 2 glass-ceramic.     

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??Objective    To investigate the fracture resistance of different lithium disilicate crowns by mechanical test.  Methods    Totally 30 epoxy dies crowns were divided into 3 groups. They were cemented to domestic lithium disilicate glass-ceramic crowns in Group DID?? to IPS e.max CAD crowns in Group IPC and to IPS e.max Press crowns in Group IPP respectively. Use the universal testing machine to survey the flexural  strength.Stainless steel ball with a diameter of 6 mm was vertically placed on the occlusal surface of the crowns at a speed of 0.5mm/min.Fracture was defined as occurrence of chipping. The loads at fracture were registered??scanning electron microscopy ??SEM?? was used to  observe cross-section morphology. SPSS21.0 was used to analyze the fracture resistance of the three groups??the standard being α = 0.05. Results    The mean fracture resistance of the domestic lithium disilicate glass-ceramic crowns was ??949.7 ± 119.4?? N?? IPC group ??1746.9 ± 244.8?? N?? IPP group ??2161.8 ± 239.0?? N. The difference among the three groups was statistically significant ??F = 86.685??P < 0.05??. The difference had statistical significance ??P < 0.05?? when the groups were compared in pairs. The fracture mode of the three groups of all-ceramic crowns had no significant difference?? and the fracture mode was mostly type ??. Under SEM?? all sizes of crystals with fine cracks on surface could be seen unevenly distributing in samples of group DID?? the big and long crystals could be seen relatively evenly distributing in samples of group IPC??and in group IPP?? the rodlike lithium disilicate crystals were evenly distributed in glass phase?? interdigitated?? and formed an interlocking microstructure. Conclusion    In the study?? different lithium disilicate glass-ceramic crowns have influence on fracture resistance and fracture mode?? and domestic lithium disilicate porcelain can meet the clinical requirement?? which has certain guiding significance for its clinical application.     

三种二硅酸锂玻璃陶瓷冠抗折强度研究

目的    通过抗折破坏实验分析3种牙科二硅酸锂玻璃陶瓷抗折强度的差异,为国产二硅酸锂玻璃陶瓷临床应用提供依据。方法    将30个下颌第一磨牙标准预备体代型随机分为3组,每组10个,分别制作国产二硅酸锂玻璃陶瓷冠试件（DID组）、IPS e.max CAD冠试件（IPC组）和IPS e.max Press冠试件（IPP组）。3组全瓷冠试件粘接后,分别放置于电子万能试验机上,用直径6 mm圆形加载头,以0.5 mm/min速度垂直加载于全瓷冠面中央至瓷层碎裂,记录最大载荷,即二硅酸锂玻璃陶瓷冠抗折强度。用扫描电镜（SEM）观察表面形态。采用SPSS21.0 统计软件对3组全瓷冠试件抗折强度值进行单因素方差分析和组间两两比较的q检验,检验水准取双侧α = 0.05。结果    3组全瓷冠试件抗折强度结果：DID组为（949.7 ± 119. 4）N,IPC组为（1746.9 ± 244.8）N,IPP组为（2161.8 ± 239.0）N 。3组间总的比较,差异有统计学意义（F = 86.685,P < 0.05）;各组间两两比较,差异亦均有统计学意义（均P < 0.05）。3组全瓷冠试件的断裂模式无显著差异,大部分试件断裂类型均为Ⅰ型。SEM观察,DID组可见晶体在样本中分布不均匀,大小不一,表面有细小裂隙;IPC组可见析出晶体在样本中分布较均匀,晶体较为长大;IPP组可见析出的棒状二硅酸锂晶体均匀分布于玻璃相中,互相嵌合,并形成一种互锁微结构。结论    研究条件下,不同二硅酸锂玻璃陶瓷对抗折强度及断裂类型均有影响,国产二硅酸锂玻璃陶瓷可以满足临床要求,对于其在临床应用有一定指导意义。     

Real time neutron diffraction and NMR of the Empress II glass-ceramic system

Objective. This study reports real time neutron diffraction on the Empress II glass-ceramic system.Methods. The commercial glass-ceramics was characterized by real time neutron diffraction, ³¹P and ²⁹Si solid-state MAS-NMR, DSC and XRD.Results. On heating, the as-received glass ceramic contained lithium disilicate (Li₂Si₂O₅), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this phase had disappeared by 958 °C in agreement with thermal analysis. On cooling lithium metasilicate (Li₂SiO₃) started to form at around 916 °C and a minor phase of cristobalite at around 852 °C. The unit cell volume of both Li-silicate phases increased linearly with temperature at a rate of +17 × 10⁻³ ų.°C⁻¹. Room temperature powder X-ray diffraction (XRD) of the material after cooling confirms presence of the lithium metasilicate and cristobalite as the main phases and shows, in addition, small amount of lithium disilicate and orthophosphate. ³¹P MAS-NMR reveals presence of the lithiorthophosphate (Li₃PO₄) before and after heat treatment. The melting of lithium disilicate on heating and crystallisation of lithium metasilicate on cooling agree with endothermic and exotermic features respectively observed by DSC. ²⁹Si MAS-NMR shows presence of lithium disilicate phase in the as-received glass-ceramic, though not in the major proportion, and lithium metasilicate in the material after heat treatment. Both phases have significantly long T₁ relaxation time, especially the lithium metasilicate, therefore, a quantitative analysis of the ²⁹Si MAS-NMR spectra was not attempted.Significance. The findings of the present work demonstrate importance of the commercially designed processing parameters in order to preserve desired characteristics of the material. Processing the Empress II at a rate slower than recommended 60 °C min⁻¹ or long isothermal hold at the maximal processing temperature 920 °C can cause crystallization of lithium metasilicate and cristobalite instead of lithium disilicate as major phase.