牙科氧化锆陶瓷压痕尺寸效应及其真实硬度确定方法

目的:在分析五种氧化锆陶瓷(Y-TZP)压痕尺寸效应实验数据基础上,确定计算和测试Y-TZP真实硬度的方法.方法:收集ASTM C1327-2015标准测试的五种Y-TZP压痕尺寸效应实验数据,然后对实验数据进行分析和评价.结果:数字光处理(DLP)、机械加工(MILL)、添加A3染料(A3)和无染料(NA3)四种Y-...     

Y-TZP口腔修复材料的低温老化及抗低温老化的相关研究

综合国内外相关研究,了解氧化钇稳定的四方氧化锆多晶陶瓷(Y-TZP)口腔修复材料的低温老化现象,探讨抗Y-TZP修复陶瓷低温老化的方法,展望抗低温老化Y-TZP陶瓷在口腔临床中的应用.抗Y-TZP低温老化的方法包括:稳定剂类型和含量的选择、加工工艺的改善、适宜的表面处理、合成复合陶瓷等,其中Y-TZP/Al2O3复合陶瓷对Y-TZP的低温老化有较大程度的缓解作用,且能明显改善Y-TZP的机械性能,是一种在口腔临床应用中具有发展前景的氧化锆基陶瓷材料.     

不同频率铒激光对氧化锆陶瓷粘接性能的影响

目的: 评价不同频率铒钇铝石榴石（erbium-doped yttrium aluminum garnet,Er:YAG）激光对氧化锆陶瓷粘接性能的影响。方法: 制作3 mm×3 mm×2 mm的钇稳定四方多晶氧化锆（yttrium-stabilized tetragonal zirconia polycrystals,Y-TZP）试件,随机分为6组,即空白对照组（C组）、喷砂组（SB组）和Er:YAG激光蚀刻组（A1-A4组）,频率分别为5、10、15和20 Hz,IPS e.max Press压铸陶瓷为B组,记录各组扫描电镜图像。将陶瓷试件粘接到牙试件上,37 ℃恒温水浴,保存24 h后进行剪切实验,随后在体视显微镜下观察各个试件的断裂模式。采用SPSS 26.0软件包对实验数据进行统计学分析。结果: 扫描电镜显示,不同频率的Er:YAG激光照射Y-TZP陶瓷后,与C组相比,Y-TZP陶瓷表面变得粗糙。剪切实验结果显示,B组剪切强度值最高,为（13.15±2.97） MPa;其次为SB组[（7.78±0.97） MPa]和A2组[（7.13±0.75） MPa],SB组与A2组相比无统计学差异（P>0.05）。断裂模式结果显示,C组断裂模式以Y-TZP陶瓷与树脂粘接剂界面断裂为主,A1-A4组和SB组断裂模式大多为Y-TZP陶瓷与树脂粘接剂界面断裂,少部分为混合断裂和树脂粘接剂内聚断裂,B组断裂模式全部为混合断裂。结论: 10 Hz Er:YAG激光照射Y-TZP陶瓷可替代110 μm直径的Al₂O₃颗粒喷砂,用于Y-TZP陶瓷的表面改性,增加了Y-TZP陶瓷与树脂粘接剂的粘接强度。     

新型牙科陶瓷的抗折强度与硬度

修复体制作过程中和受载时受到表面冲击力而形成的表面缺陷的进一步发展可使牙科陶瓷修复体失败。材料的抗折力称为抗折强度。抗折强度测量技术有 双端悬臂梁法、双向扭转法、凹槽弯曲法、压痕技术。其中压痕技术较接近临床情况,样本尺寸小,结果却与凹槽弯曲法一致。因此本文采用压痕技术测新型陶瓷的抗折能力。     

醋酸及柠檬酸对牙科氧化锆陶瓷性能的影响

目的评价两种典型食用酸(醋酸、柠檬酸)在常温下对牙科氧化钇稳定四方相氧化锆陶瓷(Y-TZP)机械性能和微观结构的影响,探讨食用酸对临床上Y-TZP修复体使用安全性的影响。方法制作30枚条状氧化锆陶瓷试样,随机分为6组,并进行以下处理:阴性对照组(A组)试样不处理;阳性对照组(B组)试样放入高压灭菌器,在134℃、0.2 MPa条件下加速老化20 h;酸溶液浸泡组试样分别于10%醋酸或20%柠檬酸溶液中浸泡7 d(C组、E组)或14 d(D组、F组)。测试表面维氏硬度,计算断裂韧性。各组典型试样以扫描电镜观察表面微观结构。结果醋酸和柠檬酸浸泡并未改变Y-TZP试样的表面维氏硬度。D组断裂韧性显著降低。电镜下未发现6组试样表面微观结构的改变。结论常温下柠檬酸不会影响Y-TZP修复体的机械性能和微观结构;长期接触醋酸会造成Y-TZP断裂韧性的显著降低,影响Y-TZP修复体的临床使用寿命。     

纳米氢氧化锆涂层对10-甲基丙烯酰氧癸二氢磷酸酯提高氧化锆陶瓷粘接强度的影响

目的 研究纳米氢氧化锆在氧化锆陶瓷表面形成碱性涂层后对10-甲基丙烯酰氧癸二氢磷酸酯（MDP）与氧化锆陶瓷粘接强度的影响。方法 制作氧化钇稳定四方相氧化锆（Y-TZP）瓷片140枚,氧化铝喷砂后对其表面进行不同的处理,制作粘接试件并测试剪切粘接强度。以X线光电子能谱（XPS）检测Y-TZP陶瓷表面依次经过纳米氢氧化锆涂层和含有MDP的底涂剂处理后的化学键变化。结果 老化前,与对照组相比,两种碱性涂层均能提高短期粘接强度值,纳米氢氧化锆涂层增强效果更显著。老化后,各组粘接强度值差异无统计学意义,但较老化前均显著降低（P<0.05）。XPS在制备纳米氢氧化锆涂层的Y-TZP瓷片表面检测到-OH键,在制备纳米氢氧化锆涂层的Y-TZP陶瓷应用含有MDP的底涂剂处理后检测出-P-O-Zr键。结论 在氧化锆陶瓷表面制备碱性涂层能够使MDP提高氧化锆陶瓷粘接强度。     

稀土氧化物着色牙色四方多晶氧化锆陶瓷的机械性能研究

目的探讨添加微量稀土氧化物对牙色四方多晶氧化锆（Y-TZP）陶瓷的机械性能的影响。方法以稀土氧化物（Pr6O11、CeO2、Er2O3）和过渡元素氧化物（MnO2）为着色剂,采用粉体掺杂方法在Y-TZP粉体中添加不同质量分数的着色剂,制备出6组牙色Y-TZP,测试其机械性能（包括弯曲强度、维氏硬度、断裂韧性）,并通过扫描电子显微镜观察各组陶瓷烧结体断裂面的显微结构,分析其断裂模式。结果6组牙色Y-TZP的弯曲强度为（792±20）～（960±17）MPa,断裂韧性为（4.72±0.31）～（5.64±0.38）MPam1/2,维氏硬度为（1 332±19）～（1 380±17）MPa;显微结构显示6组陶瓷均呈致密的多晶结构,断裂模式为混合型断裂。结论以稀土氧化物作为着色剂制备的Y-TZP具有较好的断裂韧性和维氏硬度,可满足口腔临床的应用要求。     

着色剂对口腔修复用钇稳定氧化锆 陶瓷粉体制备的影响

目的 探讨着色剂氧化铁（Fe2O3）、氧化铈（CeO2）对口腔修复用钇稳定氧化锆陶瓷（Y-TZP）制备粉体的影响。方法 按照一定比例将口腔修复用Y-TZP粉体和着色剂（Fe2O3 0.15%或CeO2 4%）分别混合,配置成具有一定固含量的Y-TZP喷雾干燥浆料。通过喷雾造粒的方法进行着色和未着色Y-TZP粉体造粒。粉体分成3组,分别为未着色Y-TZP组、0.15%Fe2O3着色Y-TZP组、4%CeO2着色Y-TZP组,分别利用激光粒度分析仪和光学显微镜进行3组粉体粒径和形貌的测量和分析。结果 3组口腔修复用Y-TZP造粒粉体的颗粒D50总体均数差异有统计学意义（P<0.05）。均数两两比较时,0.15%Fe2O3着色Y-TZP粉体D50与未着色Y-TZP粉体、4%CeO2着色Y-TZP粉体D50均数差异有统计学意义（P<0.05）;未着色Y-TZP粉体与4%CeO2着色Y-TZP粉体D50均数差异无统计学意义（P>0.05）。Fe2O3、CeO2作为Y-TZP的内着色剂,粉体大多成球形。结论 CeO2作为口腔修复用Y-TZP的着色剂,对造粒粉料的粒径分布以及成球性能影响不大;Fe2O3作为着色剂进行内着色对颗粒的粒径产生一定的影响。     

磷酸酯单体PENTA与牙科氧化锆陶瓷结合的化学证据

目的 提供磷酸酯单体双季戊四醇五丙烯酸酯磷酸酯（Dipentaerythritol penta-acrylate phosphate,PENTA）与牙科氧化锆陶瓷结合的化学证据,分析PENTA提高牙科氧化锆陶瓷粘接的机理。 方法 配置包含PENTA的质量分数为5%、10%、15%、20%的实验性底涂剂,用其处理Y-TZP（Yttria-stabilized tetragonal zirconia polycrystals）瓷粉,随后以丙酮反复清洗去除游离成分后分别进行红外光谱分析（fourier transform infrared spectroscopy,FTIR）和热重分析（thermogravimetric analysis,TG）。FTIR分析以10%PENTA丙酮溶液作为对照,分别采用二阶导数分峰和残差分峰两种方法对FTIR图谱磷酸基团特征峰进行分峰分析;TG以空白Y-TZP粉作为对照。 结果 两种FTIR分峰分析结果一致,均表明各种浓度的包含PENTA的底涂剂与Y-TZP陶瓷接触后,磷酸基团的P-O键振动所产生的波峰向波数减小的方向移动。热重结果证明PENTA能够化学吸附于Y-TZP表面,高浓度组的PENTA与氧化锆的反应程度更高。 结论 PENTA能够与Y-TZP发生化学结合,该化学反应的存在依赖于PENTA分子中的磷酸基团发挥作用。     

两种着色氧化物对氧化锆陶瓷的颜色影响

目的:选取适合的2种着色金属氧化物对氧化锆粉体(3Y-TZP)进行着色,系统的研究2种着色金属氧化物对氧化锆最终的颜色性能影响。方法:在氧化锆粉体中,加入不同质量分数Fe2O3、CeO2粉体,将粉体装入模具,200MPa冷等静压成型,常压烧结后制得终烧体。从终烧体上切取瓷片,每组5个,使用VITAEasyshade比色仪进行颜色测定,得到瓷片的颜色色度值。结果:添加CeO2后材料的明度为85左右,a*值稍有降低,颜色色调向黄绿色相偏移。添加Fe2O3能显著降低氧化锆陶瓷(3Y-TZP)明度,使材料色调向黄红色相偏移。结论:着色金属氧化物能够赋予氧化锆陶瓷所需的色度值,对氧化锆陶瓷的其他性能影响,尚待进一步研究。     

Indentation size effect of Y-TZP dental ceramics

ObjectiveThe purpose of this study was to investigate and analyze the indentation size effect (ISE) in Vickers hardness of monolithic yttria partially stabilized zirconia (Y-TZP) dental ceramics without and with the addition of dental dye A3. The ISE is analyzed using the Mayer law, a proportional specimen resistance (PSR) model and a modified proportional specimen resistance (MPSR) model.MethodsTwo samples of Y-TZP dental ceramics, trade names BruxZir (provided by Glidewell Laboratories, CA, USA), were investigated. The first sample was polished Y-TZP and the second sample was polished Y-TZP with the addition of dental dye A3, by VITA Classical Shade Guide. The Vickers hardness was measured under the following loads: 0.49 N, 0.98 N, 1.96 N, 4.90, 9.81 N and 29.42 N. Thirty indentations were made on each sample, under each load. Relationships between the applied load, F, and the resulting indentation size, d, have been analyzed by the Mayer law, the PSR model and the MPSR model.ResultsThe Meyer index (n) for both Y-TZP dental ceramics is less than 2, which indicates that hardness is dependent on test loads. The PSR model and the MPSR model were used to calculate “true” Vickers hardness or load-independent hardness.SignificanceAll applied mathematical models are suitable for the data analysis, which is confirmed with high correlation coefficients, but the best correlation between measured values and mathematical models was achieved with the MPSR model with a correlation coefficient of 0.9999.     

Effect of loading conditions on the fracture toughness of zirconia

PurposeA Vickers hardness indenter was pressed into yttria-stabilized zirconia (Y-TZP) by the indentation fracture method (IF method).MethodsThe effect on the calculated Vickers hardness, fracture toughness values, and indentation fracture load (9.8, 49, 98, 196, and 294 N) was examined to deduce the optimum conditions of the IF method. Calculated Vickers hardness and fracture toughness values were analyzed with one-way analysis of variance and then multiple comparisons (Scheffe). The appearance of on indentation and cracks was also evaluated using a scanning electron microscopy (SEM).ResultsIndentation of Y-TZP was generated by 9.8 and 49 N of indentation fracture load, however cracks could not be confirmed with the microscope attached to the Vickers hardness tester. Both indentation and cracks were observed at 98, 196 and 294 N of indentation fracture load obtained values of 7.1 and 6.8 MPam^1/2. Cracks noted at the 98 N were not clear, whereas the 196 and 294 N showed especially clear cracks. Due to the hardness of zirconia and the light loads, fracture toughness values for 9.8, 49, and 98 N could not be calculated. There was no significant difference between 196 and 294 N, when calculated fracture toughness values were analyzed with multiple comparisons. SEM revealed clear indentation and cracks, that extended linearly, but no chips or fractures were observed. Surface changes were observed at 196 and 294 N that are presumed to be accompanied by phase transition around the cracks.ConclusionsOptimum experimental conditions of the indentation fracture load in the IF method were determined as 196 and 294 N.     

The influence of simulated masticatory loading regimes on the bi-axial flexure strength and reliability of a Y-TZP dental ceramic

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.     

Mechanical behavior and microstructural characterization of different zirconia polycrystals in different thicknesses

PURPOSETo characterize the microstructure of three yttria partially stabilized zirconia ceramics and to compare their hardness, indentation fracture resistance (IFR), biaxial flexural strength (BFS), and fatigue flexural strength.MATERIALS AND METHODSDisc-shaped specimens were obtained from 3Y-TZP (Vita YZ HT), 4Y-PSZ (Vita YZ ST) and 5Y-PSZ (Vita YZ XT), following the ISO 6872/2015 guidelines for BFS testing (final dimensions of 12 mm in diameter, 0.7 and 1.2 ± 0.1 mm in thicknesses). Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed, and mechanical properties were assessed by Vickers hardness, IFR, quasi-static BFS and fatigue tests.RESULTSAll ceramics showed similar chemical compositions, but mainly differed in the amount of yttria, which was higher as the amount of cubic phase in the diffractogram (5Y-PSZ > 4Y-PSZ > 3Y-TZP). The 4Y- and 5Y-PSZ specimens showed surface defects under SEM, while 3Y-TZP exhibited greater grain uniformity on the surface. 5Y-PSZ and 3Y-TZP presented the highest hardness values, while 3Y-TZP was higher than 4Y- and 5Y-PSZ with regard to the IFR. The 5Y-PSZ specimen (0.7 and 1.2 mm) showed the worst mechanical performance (fatigue BFS and cycles until failure), while 3Y-TZP and 4Y-PSZ presented statistically similar values, higher than 5Y-PSZ for both thicknesses (0.7 and 1.2 mm). Moreover, 3Y-TZP showed the highest (1.2 mm group) and the lowest (0.7 mm group) degradation percentage, and 5Y-PSZ had higher strength degradation than 4Y-PSZ group.CONCLUSIONDespite the microstructural differences, 4Y-PSZ and 3Y-TZP had similar fatigue behavior regardless of thickness. 5Y-PSZ had the lowest mechanical performance.     

The hardness and modulus of elasticity of primary molar teeth: an ultra-micro-indentation study

Objective: Baseline information on the mechanical properties of and the effect of load upon dental hard tissue is important in the development of successful dental materials. Existing methods of measuring such properties of tissue are subject to significant experimental error. This study reports on the use of an Ultra-Micro-Indentation System (UMIS) to measure the hardness and elastic modulus of primary enamel and dentine.

Methods: Primary molar teeth were sectioned, set in resin and polished. Thirty indentations were made in enamel and dentine using a Berkovitch indentor, 15 of which were subject to a load of 50 mN and 15 to a load of 150 mN. An automated computerised system converted the force/penetration graph for each indentation in to a hardness vs depth graph from which values for the mean hardness and elastic modulus were calculated.

Results: Primary enamel had a mean hardness of 4.88±0.35 GPa whilst the hardness of dentine was 0.92±0.11 GPa The elastic modulus for enamel was 80.35±7.71 GPa and that of dentine 19.89±1.92 GPa. Using linear regression analysis a significant relationship could be shown between the hardness and the elastic modulus for both enamel and dentine when loaded to 150 mN but only for dentine at 50 mN (P<0.05). In general the elasticity of tooth structure increased as the hardness increased.

Conclusion: The UMIS offers a simple and reproducible method of measuring basic mechanical properties of small samples of enamel and dentine.     

Correlation between strength and hardness of dental casting gold alloys

abstract – The yield strength, tensile strength, and hardness of Type IV dental casting gold alloys were measured. Regression lines and prediction intervals for the estimation of yield strength and tensile strength from hardness measurements were then determined. The 95% prediction intervals for the yield strength and tensile strength were found to be ± 45 MN/m² and ± 105 MN/m², respectively.     

氧化铝喷砂对牙科用氧化锆基底与饰面瓷结合强度的影响

目的 研究氧化铝（Al₂O₃）喷砂对牙科用氧化锆基底与饰面瓷结合强度的影响。方法 按照ISO 9693的要求,制作（25±1） mm×（3±0.1） mm×（0.5±0.05） mm的片状氧化锆试样21个,随机分为3组：A组进行110目Al₂O₃喷砂;B组进行80目Al₂O₃喷砂;对照组不做喷砂处理。测定所有基底瓷的表面粗糙度以及基底瓷与饰面瓷的结合强度,扫描电镜（SEM）观察结合界面微观形貌,能谱分析（EDS）检测界面元素分布。结果 A组、B组和对照组基底瓷表面粗糙度分别为（1.272±0.149）、（0.622±0.113）、（0.221±0.065） μm;瓷瓷结合强度分别为（28.21±1.52）、（27.71±1.27）、（24.87±3.84） MPa。统计结果显示：各组间表面粗糙度的差异具有统计学意义（P<0.05）;A组和对照组之间结合强度的差异具有统计学意义（P<0.05）,而B组与A组和对照组之间的差异均无统计学意义（P>0.05）。破坏模式以结合界面附着破坏为主。SEM观察结果显示瓷瓷结合界面结合紧密,EDS结果表明界面无明显元素渗透现象。结论 Al₂O₃喷砂能提高基底瓷与饰面瓷的结合强度,但其作用不明显。     

Effect of exposure intensity and post-cure temperature storage on hardness of contemporary photo-activated composites

Objectives: The effect of variation in post-exposure storage temperature (18 vs. 37°C) and light intensity (200 vs. 500 mW/cm²) on micro-hardness of seven light-activated resin composite materials, cured with a Prismetics Mk II (Dentsply) light activation unit, were studied.

Methods: Hardness values at the upper and lower surfaces of 2 mm thick disc shaped specimens of seven light-cured resin composite materials (Herculite XRV and Prodigy/Kerr, Z100 and Silux Plus/3M, TPH/Dentsply, Pertac-Hybrid/Espe, and Charisma/Kulzer), which had been stored dry, were determined 24 h after irradiation with a Prismetics Mk II (Dentsply) light activation unit.

Results: Hardness values varied with product, surface, storage temperature, and curing light intensity. In no case did the hardness at the lower surface equal that of the upper surface, and the combination of 500 mW/cm² intensity and 37°C storage produced the best hardness results at the lower surface.

Conclusions: Material composition had a significant influence on surface hardness. Only one of the seven products (TPH) produced a mean hardness values at the lower surface >80% of the maximum mean upper surface hardness obtained for the corresponding product at 500 mW/cm² intensity/37°C storage temperature when subjected to all four test regimes. Despite optimum post-cure storage conditions, 200 mW/cm² intensity curing for 40 s will not produce acceptable hardness at the lower surface of 2 mm increments of the majority of products tested.     

Electron microscopy of enamel surface after reactions of apatite accretion

Abstract. Images were obtained from intact and acid etched enamel surfaces (both before and alter growth of surface apatite) with electron diffraction, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Labial surfaces (intact) of bovine incisor teeth were slightly abraded and pumiced. They were then etched by a 14-hour immersion in 2mM sodium acetate-acetic acid buffer at pH 5.0; an average of 31 μ.Mol/cm² calcium and 24 μMol/cm² phosphate was dissolved from the surfaces. The SEM. and TEM showed loss of minerals to a depth of 10 μm. Dissolution was largely in central areas of enamel prisms, and prismatic structure in the etched surfaces was retained. Electron diffraction, SEM, and TEM showed the growth of crystalline apatites at the etched surfaces after 24 to 96 hours immersion in neutral pH solution (metastable) which contained 1.5 mM Ca⁺², 0.9 mM H₂PO₄/HPO₄⁻², 0.05 mM F⁻, and 150 mM NaCl. Indirect analysis, at the loss of calcium and phosphate concentrations in the metastable solution after immersion periods, indicated deposition of approximately 24μMol/Cm² calcium and 14μMol/cm² phosphate on the etched surfaces. Results show induction of apatite crystal growth and recrystallization at enamel surfaces in otherwise stable solutions containing 0.05 mM F⁻.