Effect of repeated firings and staining on the mechanical behavior and composition of lithium disilicate

ObjectiveTo evaluate the composition, flexural strength and fatigue behaviour of lithium disilicate ceramic (LD) after repeated firings and different staining techniques.MethodsLD discs were fabricated and divided according to number of firing cycles and staining technique: CO - control, discs were crystallized (850 °C/10 min); SC – single-step characterization – crystallization and staining (applied with a thin brush) were performed in a single step with one firing cycle (850 °C/10 min); and DC – double-step characterization – crystallization firing cycle was performed first (850 °C/10 min), followed by staining firing cycle (770 °C/90 s). Specimens were fired two, four or six times (one crystallization firing cycle and one, three or five staining firing cycles), resulting into 9 groups (n = 30): COII, COIV, COVI, SCII, SCIV, SCVI, DCII, DCIV and DCVI. The composition of the specimens was investigated (EDS, XRD, Raman spectroscopy), and the biaxial flexural strength (n = 10) and staircase tests (n = 20, 5 × 10⁴ cycles, 5 Hz) were performed. Data were subjected to one-way ANOVA and Tukey’s test (α = 0.05).ResultsEDS and XRD revealed amorphous content for stained groups. Biaxial flexural strength was not affected by repeated firings in any group, but stained groups presented lower flexural strength than control groups (p = 0.001). The fatigue limit results decreased in all groups compared to flexural strength. SC groups showed similar (SCII and SCIV) or even higher fatigue limits (SCVI) than the control groups, and DC showed the lowest fatigue limit values. SEM and Raman suggested that the interfaces between staining and the LD showed only an overlap for the DC groups, whereas for the SC it was suggested an interaction between the stain and the LD.SignificanceRepeated firings did not result in decreased lithium disilicate flexural strength.Staining affected flexural strength and also resulted in increased amorphous content in the characterized specimens. Single-step staining resulted in the highest fatigue limit.     

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...     

Impact of thermocycling on surface roughness,microhardness and optical properties of three different lithium disilicate ceramics

ObjectivesThis investigation was carried out to examine the influence of thermocycling aging on the surface roughness (R_a, µm), color parameters (L*, a*, b*), lightness change (ΔL*), chroma change (ΔC*_ab), color change (ΔE), and microhardness (VH) of three lithium disilicate ceramics.Materials and methodsForty-five specimens were prepared from three lithium disilicate materials (n = 15)—e.max CAD (EC), e.max Press (EP), and GC Initial LiSi Press (LP) ceramics—with dimensions of 6.0 × 1.2 × 16.0 ± 0.2 mm following the manufacturers’ instructions. All specimens were exposed to 5000 thermal cycles with bath temperatures ranging between 5 °C and 55 °C. Data of surface roughness, color parameters, and microhardness were obtained using an optical profiler, a spectrophotometer, and a Vickers hardness tester, respectively. One-way ANOVA, a post-hoc Tukey’s test, and a paired sample t-test were implemented for statistical analysis (p ≤ 0.05).ResultsFor surface roughness, insignificant differences were reported between the materials either before or after thermocycling (p > 0.05) while each material displayed a significant increase after being subjected to thermocycling (p < 0.05). For color parameters, LP showed significantly lower L* and b* after thermocycling while EC presented a significant reduction in a* in comparison with other materials (p < 0.05). EP showed a significant decrease in ΔL*, ΔC*_ab and ΔE compared with other materials (p < 0.05). Regarding microhardness, LP showed significantly increase value in comparison with other materials (p < 0.05).ConclusionsThermocycling had a major impact on the surface roughness, microhardness and optical characteristics of the tested materials. E.max Press displayed less changes in (ΔL*), (ΔC*_ab) and (ΔE), while GC LiSi Press had better behavior in terms of microhardness.     

氢氟酸处理对二硅酸锂玻璃陶瓷表面形貌及粗糙度的影响

目的 探讨氢氟酸处理时间对二硅酸锂玻璃陶瓷表面形貌及粗糙度的影响,拟为与之相关的玻璃陶瓷机械强度和树脂粘接强度做出初步解释.方法 采用失蜡铸造法制作直径10 mm、厚1 mm的玻璃陶瓷片状试件15个,打磨抛光之后随机分为5组,每组3个.陶瓷表面分别接受9.5％的氢氟酸凝胶酸蚀处理0、20、40、60和120 s.使用原子力显微镜(AFM)测量表面粗糙度参数和酸蚀深度,观测其表面三维形貌,并结合使用场发射扫描电子显微镜(FE-SEM)对陶瓷表面微观结构进行观察分析.结果 FE-SEM观察显示,陶瓷表面的玻璃基质首先被氢氟酸侵蚀溶解,随着酸蚀时间的延长,玻璃基质进一步被侵蚀,部分晶体结构也从陶瓷表面脱落、消失.AFM测量酸蚀表面得出,对照组、20、40、60和120 s氢氟酸处理组陶瓷片表面粗糙度Ra[分别为(17.2±1.6)、(241.8±23.6)、(290.6±38.2)、(322.6±19.6)和(371.3 ± 43.0) nm]随氢氟酸酸蚀时间的延长而显著增加(P＜0.05),且与酸蚀时间成正相关.结论 氢氟酸处理可显著增加二硅酸锂陶瓷表面粗糙度.结合使用FE-SEM和AFM能够更好地对玻璃陶瓷的酸蚀表面微观形貌结构进行分析评价.     

8—MOP,ATRA以及二者联合应用对Mc3细胞克隆形成的影响

研究8-MOP与ATRA单独及联合应用对Mc3细胞克隆的影响。方法。软琼脂克隆法。结果：照组细胞克隆形成率为53．1％,经IC308-MOP与ATRA单独及联合作用5－d以后,克隆形成率降低为8-MOP组0．9％,ATRA组35.1％,联合用药组3.2％。结论：8－MOP与ATRA单独及联合应用Mc3细胞克隆形成率降低,有可能使Mc3细胞的转移能力下降。     

不同表面处理方式对丙烯酸树脂表面性状和粘接强度的影响

目的探讨不同表面处理方式对丙烯酸树脂表面性状和粘接强度的影响。方法制备硅橡胶与丙烯酸树脂构成的重叠联合模型。根据树脂条的不同表面处理方式,将模型随机分为4组:对照组、MMA浸润组、喷砂组、MMA浸润+喷砂组。用扫描电镜观察各组树脂处理后的表面形态变化,用粗糙度仪检测其粗糙度,万能材料试验机测定树脂条和硅橡胶之间的粘接强度。结果 1.电镜观察显示,未经处理的树脂条表面打磨痕迹明显,经过MMA浸润后,表面出现溶解的痕迹,经过喷砂后,表面粗糙凸凹不平;2.粗糙度:喷砂组(3.12±0.02)μm和MMA浸润+喷砂组(3.11±0.01)μm>对照组(0.73±0.01)μm和MMA浸润组(0.71±0.01)μm,且差异有统计学意义(P<0.05);3.粘接强度:MMA浸润+喷砂组(2.34±0.03)MPa>喷砂组(2.02±0.01)MPa>MMA浸润组(1.81±0.02)MPa>对照组(1.50±0.01)MPa,且差异有统计学意义(P<0.05)。结论 MMA单体浸润与喷砂的处理方式可以使丙烯酸树脂表面的形貌发生变化,更有利于硅橡胶与丙烯酸树脂的结合,获到良好的粘接效果,可在临床推广使用。     

Survival probability of zirconia-reinforced lithium silicate ceramic: Effect of surface condition and fatigue test load profile

ObjectivesThe present investigation evaluated the step stress accelerated test (SSALT) load profiles on the survival probability of a glass ceramic under two surface conditions (polished or roughened).MethodsSuprinity–ZLS blocks (Vita Zhanfabrik) were shaped into cylinders, cut in a sawing machine, and crystalized according to the manufacturer's instructions. 60 discs were obtained (Ø = 12 mm, thickness = 1.2 mm) and randomly assigned into two surface conditions: “p” polished surface (400–1200-grit SiC papers), and “r” roughened surface (200-grit SiC papers). Profilometry was performed in all discs to evaluate average surface roughness prior to flexural fatigue strength testing. 3 discs of each group were submitted to biaxial flexural strength in an universal testing machine (0.5 mm/min) and the mean load to failure (N) was calculated to determine SSALT profiles. 27 specimens per surface condition were assigned into three profiles – Mild (n = 9), Moderate (n = 9), and Aggressive (n = 9), and submitted to the fatigue test (60–320 N, 140,000 cycles at 1.4 Hz). The results were analyzed using the Kaplan-Meier and Wilcoxon tests (5%), 2-way ANOVA and Tukey test (α = 5%).ResultsKaplan-Meier and generalized Wilcoxon showed (P = 0.002) that polished groups showed higher survival probability than roughened condition (P < 0.05). A rough internal surface impacted deleteriously on the fatigue strength and reliability of ZLS ceramic. Both surface conditions were more sensitive to the aggressive profile than the other profiles, even worst for the roughened group. Regardless the load profile, 0% survival probability was observed at 384 MPa for polished condition. While for roughened, aggressive tested specimens did not survived 147 MPa followed by moderate at 312 MPa and mild at 384 MPa. The failure modes showed fracture marks originating from superficial grooves for both surface conditions.SignificancePolished specimens are sensitive to the load profile variation, confirming the effect of surface morphology on the fatigue results.     

Effect of titania addition and sintering temperature on the microstructure,optical, mechanical and biological properties of the Y-TZP/TiO2 composite

ObjectiveThe aims of this study were: 1) to evaluate the effect of sintering temperature on microstructure, density and flexural strength of a 3Y-TZP/TiO₂ composite containing 12.5 wt% of TiO₂ compared to 3Y-TZP specimens (control); 2) to compare 3Y-TZP with the experimental 3Y-TZP/TiO₂ composite, both sintered at 1400 °C, with respect to the following parameters: optical properties, characteristic strength, Weibull modulus, fatigue behavior, induction of osteoblasts proliferation and differentiation (mineralization nodules formation).MethodsThe 3Y-TZP and 3Y-TZP/TiO₂ powders were uniaxially pressed and sintered at 1200 °C, 1300 °C, 1400 °C or 1500 °C for one hour in a furnace. The microstructural analysis consisted of X-ray diffraction and scanning electron microscopy. The density was measured by the Archimedes' principle and the flexural strength was obtained by the biaxial flexure test. The optical properties were measured using a spectrophotometer operating in the visible light wavelength range. The step-stress accelerated life testing was performed by the pneumatic mechanical cycler and the biological behavior achieved by using osteoblast-like cells (Osteo-1 cell line).ResultsTetragonal zirconia was identified in all groups and cubic zirconia was identified only at 3Y-TZP group. The addition of TiO₂ decreased the values of density and flexural strength of the composite 3Y-TZP/TiO₂ in relation to 3Y-TZP regardless of the sintering temperature. The color difference between the two materials was not significant regarding L*a*b* parameters. The composite showed higher probability of failure, and induced higher proliferation and differentiation than control.SignificanceThe composite developed have good aesthetic and biologics properties. However, its microstructure and mechanical properties need to be improved for future dental implant applications.     

Translucent multi-layered zirconia: Sandblasting effect on optical and mechanical properties

ObjectiveThe aim of this study was to evaluate the influence of the sandblasting treatment on the microstructure, optical and mechanical properties of multi-layered translucent zirconia.MethodsSamples of yttria-stabilized zirconia were prepared by stratifying four layers (L1, L2, L3 and L4) of ML-type KATANA multi-layered monolithic discs, whose surfaces were then sandblasted with alumina particles (110 µm and 0.2 MPa) in order to evaluate its effect on the presence of different crystalline phases as well as on the optical and mechanical properties of each of the four layers. The optical characterization was carried out by measuring the reflectance spectrum and colorimetric parameters by UV-Vis spectrophotometric analysis and the transmittance curves were indirectly obtained using the Kubelka-Munk model (KM). Microstructural, structural, mechanical and roughness characterizations were also performed using SEM, XRD, biaxial flexural strength B3B, and light interferometry, respectivelyResultsAccording to the KM model there are different degrees of translucency between the upper and lower layers of the monolithic discs, but there was no influence of the Al₂O₃-sandblasting treatment on this optical property. The disk pigmentation causes greater absorption of light below 600 nm, decreasing the transmittance rate to values below 25% in this region of the spectrum. The yellowing index presented higher values for inner disk layers L3 and L4, in agreement with the highest values of the light absorption coefficient K observed for these layers. The roughness of the samples did not change significantly with the surface treatment performed and the sandblasting did not result in new crystalline phases. SEM analysis showed the presence of different grain sizes in all layers analyzed, being related to the co-occurring presence of cubic (c-ZrO₂) and tetragonal (t-ZrO₂) phases in similar contents (∼ 50 wt%). The Weibull statistical analysis, in turn, showed an increase in the Weibull characteristic stress value (σ₀) for most layers subjected to sandblasting, except for the second layer (central region of the disk). It was also verified an increase in the value of the structural reliability of the material (m), referring to the samples of the central region of the disc (L2 and L3 layers) after sandblasting.Significance:The pigmentation in the disk causes a decrease of the transmittance rate to values well below 25% in the region of the spectrum 400–600 nm and the inner layers (L3 and L4) have even lower transmittance than the outer layers in this spectrum range. Although the CR index indicates variation related to the Al₂O₃-sandblasting treatment, the transmittance spectra of KM model show that the sandblasting did not cause a significant change in the transmittance rate of the four analyzed layers. Also, there is no significant difference in the light scattering of the different layers of the disc, either before or after Al₂O₃-sandblasting treatment.     

Effects of multiple firing processes on the mechanical properties of lithium disilicate glass-ceramics produced by two different production techniques

Statement of problemRepeated firings cause materials to be exposed to additional heat treatments. The effect of these additional heat treatments on the mechanical properties of lithium disilicate glass-ceramics is not fully known.PurposeThe purpose of this in vitro study was to determine the effects of repeated firing on the mechanical properties of lithium disilicate glass-ceramics produced by 2 different techniques, press and computer-aided design and computer-aided manufacturing (CAD-CAM).Material and methodsEighty rectangular (25×4×2 mm) lithium disilicate glass-ceramic specimens were used in this study, 40 produced by heat pressing and 40 by milling, and divided into 4 groups (n=10) with a different number of veneer porcelain firings (1 to 4). After firing, the Vickers hardness, flexural strength (3-point bend test), and fracture toughness were determined, and the specimens were analyzed with an environmental scanning electron micrograph. Data were analyzed with analysis of variance (ANOVA) (α=.05).ResultsThe repeat firing processes did not affect the flexural strength of the specimens in either group (P>.05), while the surface hardness and fracture toughness were significantly changed (P<.05).ConclusionsIncreasing the number of firings adversely affected the mechanical properties of lithium disilicate glass-ceramics.     

Effect of beverage solutions and toothbrushing on the surface roughness,microhardness, and color stainability of a vitreous CAD-CAM lithium disilicate ceramic

Statement of problem

Computer-aided design and computer-aided manufacturing (CAD-CAM) has enhanced the physicomechanical stability of ceramics. However, various factors in the oral cavity may impair the longevity of restorations by negatively affecting their properties. Appropriate surface treatments such as glaze application or mechanical polishing are necessary to diminish these effects.

Effect of staining and whitening systems on color stability of computer aided design/computer aided manufacturing lithium disilicate glass ceramic

PurposeTo investigate the effect of coffee stain and whitening systems on the color stability of CAD/CAM glazed lithium disilicate glass-ceramics (LDGCs).Methods 68 glazed LDGC discs (12 × 10 × 2 mm) were fabricated using blocks of CAD/CAM systems (IPS e.max CAD ceramic). Baseline color was measured (CIE/L*a*b*), and specimens were randomized into four groups (n = 17). All specimens were stained (coffee solution; 24 h/d × 12) and then subjected to two whitening protocols. G1- (kept moist × 7 days); G2-positive control (brushed with distilled water, 200gm/load, 2 min twice daily × 7 days); G3- whitening toothpaste (Colgate optic white; relative dentin abrasivity = 100, 200gm/load, 2 min twice daily × 7 days) and G4-simulated at-home bleaching protocol (Opalescence,15% carbamide peroxide (CP), 6 h/day × 7 days). The study outcome was color change (ΔE) measured at baseline, after staining, and after whitening treatments. Data were analyzed using paired T-test and one-way ANOVA (α = 0.05).ResultsAll groups stained equally (p > 0.05) but were not clinically significant (ΔE ≤ 1.05). Stains were significantly (p ≤ 0.01) improved in G2 and G3 (ΔE = 0.69 and 0.63), yet were not eliminated compared to bleaching, which had the highest color improvement and completely removed the stains (ΔE = 0.72).ConclusionsGlazed LDGC was color stable after simulating one year of coffee staining. Bleaching, using 15% CP for a week, completely removed the stains and returned the LDGCs to their original shade. However, simulating eight months of brushing, regardless of the toothpaste content, improved the color outcome but didn’t remove it completely.     

Effect of surface treatments on optical,topographical and mechanical properties of CAD/CAM reinforced lithium silicate glass ceramics

ObjectivesTo investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC’s) and their combined effect on the output of a light curing unit (LCU).MethodsFour CAD/CAM LSC’s were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (θ°) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (σ) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (α = 0.05).ResultsAcid neutralization decreased T% and increased Abs% in all LSC’s and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced θ° (p < 0.001). σ was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC’s.SignificanceOptical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.     

氢氟酸质量分数对二硅酸锂玻璃陶瓷表面形貌及树脂粘接的影响

目的 探讨不同质量分数的氢氟酸对二硅酸锂玻璃陶瓷表面形貌及树脂粘接耐久性的影响。方法 制备大小为11 mm×13 mm×2 mm的二硅酸锂玻璃陶瓷片试件72个,经烧结、研磨、清洗后,随机分为3组,每组24个,分别接受质量分数为32%的磷酸、4%的氢氟酸、9.5%的氢氟酸处理20 s,形成酸蚀后试件。每组随机选出4个陶瓷片,1个使用扫描电子显微镜观察陶瓷表面形态,另外3个用表面粗糙度仪测量陶瓷片表面粗糙度参数（Ra、Rz和Rmax）。陶瓷片表面接受硅烷偶联剂/树脂粘接剂/树脂水门汀处理,并与直径3 mm的复合树脂柱粘接形成粘接试件。将每组20个粘接试件分为两组,10个试件直接进行剪切实验,10个试件经20 000次冷热循环后进行剪切实验。结果 氢氟酸处理组试件表面粗糙度参数值均显著高于磷酸处理组;9.5%氢氟酸组除Ra以外的参数值均高于4%氢氟酸组（P<0.05）。冷热循环明显降低了所有实验组的粘接强度（P<0.05）。冷热循环前后,氢氟酸处理组的粘接强度均高于磷酸处理组;尽管4%氢氟酸组的粘接强度高于9.5%氢氟酸组,但9.5%氢氟酸组在冷热循环过程中的粘接强度降低幅度要明显低于4%氢氟酸组（P<0.05）。结论 氢氟酸的质量分数对陶瓷表面形态及与树脂的粘接耐久性有明显影响,9.5%氢氟酸能更有效地保持二硅酸锂玻璃陶瓷的树脂粘接强度。     

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。     

使用FUS-invest锆系牙科纯钛包埋料提高铸件的物理机械性能及精度

目的:评价自制FUS-invest锆系牙科纯钛包埋料铸造的纯钛铸件的物理机械性能及标准化单冠的精度.方法:制备7个厚度为0.8 mm的纯钛比例铸件.经伺服液压动态实验系统、断口扫描电镜观察及能谱分析,评价其物理机械性能.制备38个标准化单冠,实验组(FUS-invest锆系包埋料)、对照组(磷酸盐系包埋料)各19个,测量显微镜测标准化单冠边缘差异值d和铸件内壁与工作模的距离,进行铸件精度评价.采用SPSS17.0软件包对数据进行统计学分析.结果:①纯钛铸件的弹性模量为(123.5±14.2)GPa,屈服强度为(569.3±16.5) MPa,抗拉强度为(668.4±16.1) MPa,延伸率为(4.5±0.2)％;断口EDS分析除钛元素外,不同深度处可发现少量不同含量的Si元素和Fe元素,但未检测出Zr元素.②精度实验中,单因素方差分析及两独立样本t检验显示,组内标准化单冠边缘4个标记点处的测量值无显著差异(P＞0.05);实验组和对照组相比亦无显著差异(P＞0.05).2组内部测量值无显著差异(P＞0.05),而组内内部不同标记点间差异显著(P＜0.01).结论:虽然FUS-invest锆系包埋料铸造获得铸件的延伸率略低,但各项物理机械性能均达到临床要求.无论边缘适合性还是内部适合性,2组均无显著差异且均在临床可接受范围,2组边缘差异均值约为46 μm,内部近咬合面的差异均值约为56 μm,内部轴壁处的差异均值约为0.     

表面有机改性纳米SiO_x对A-2186硅橡胶机械性能的影响

目的:研究添加不同浓度的表面改性纳米SiOx对A-2186硅橡胶机械性能的影响。方法:将表面有机改性纳米SiOx分别按照2、4、6wt%的比例加入A-2186硅橡胶,固化后得到3组实验样品,未添加表面有机改性纳米SiOx的A-2186硅橡胶作为对照组。按照ASTM标准制作试件,测试材料的拉伸强度、拉断伸长率、撕裂强度、邵氏A硬度。采用SPSS10.0软件包对数据进行统计学分析。结果:添加表面有机改性纳米SiOx后,A-2186硅橡胶的拉伸强度自(6.16±0.27)MPa显著下降(P<0.001)。表面有机改性纳米SiOx添加量为2wt%时,其拉断伸长率(292.20±6.26)%较对照组(314.40±8.05)%下降,无统计学差异(P=0.068)。其余各实验组与对照组相比,差异有统计学意义。表面有机改性纳米SiOx加入量为2、4wt%时,A-2186硅橡胶的撕裂强度(12.50±0.96)kN/m分别提高至(21.96±1.02)kN/m、(18.22±1.07)kN/m,均较对照组有统计学差异(P<0.001);其中,2wt%组高于4wt%组,两者差异显著(P<0.001)。加入表面有机改性纳米SiO...     

反复熔铸对纯钛烤瓷合金力学性能的影响

目的： 探讨反复熔铸对纯钛烤瓷合金力学性能的影响。方法：纯钛经过1~3次单纯反复熔铸后,采用拉伸实验、弯曲实验、硬度实验对各代试件的力学性能进行测试。采用SPSS13.0软件包对数据进行统计学分析。结果：经不同次数熔铸的纯钛烤瓷合金试件,其弯曲强度无显著差异。经过2次、3次熔铸的纯钛烤瓷合金试件,其弯曲模量较1次熔铸的纯钛烤瓷合金显著升高(P<0.05)。拉伸强度、0.2%屈服强度随着熔铸次数的增加而升高(P<0.05)。经过3次熔铸的纯钛烤瓷合金试件,其延伸率较经过1次、2次熔铸的纯钛烤瓷合金显著降低(P<0.05)。经过3次熔铸的纯钛烤瓷合金试件,其显微硬度较经过1次、2次熔铸的纯钛烤瓷合金显著升高(P<0.05)。结论：纯钛烤瓷合金经1~3次单纯反复熔铸后,弯曲性能、显微硬度未下降,但拉伸性能下降。