GI－Ⅰ型粉浆涂塑铝瓷核冠底层抗弯强度的测定

采用三点弯曲试验测试了６件ＧＩ－Ⅰ型粉浆涂塑铝瓷核冠底层的抗弯强度，结果表明，ＧＩ－Ⅰ型粉浆涂塑铝瓷核冠底层的抗弯强度为２０６．７６ＭＰａ，高于常见的几种全瓷修复系统。     

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。     

GI—Ⅰ型粉浆涂塑铝瓷核冠底层抗弯强度的测定

采用三点弯曲试验测试了６件ＧＩ－Ⅰ型粉浆涂塑铝瓷核冠底层的抗弯强度，结果表明，ＧＩ－Ⅰ型粉浆涂塑铝瓷核冠底层的抗弯强度为２０６．７６ＭＰａ，高于常见的几种全瓷修复系统。     

可切削渗透陶瓷的渗透方法及性能

探讨可切削渗透陶瓷的渗透方法,了解氧化铝基体的堆积密度对ＭＩＣ性能的影响。方法：应用Ｉｎ－Ｃｅｒａｍ渗透技术,交云母微晶玻璃渗透入多孔氧化铝基体中,形成连续渗复合体,并进行微晶化处理,测定３种不同基体堆积密度ＭＩＣ的物理性能。结果：本实验的云母玻璃经１１６０℃保持６ｈ渗透后,可获得具有优良性能的ＭＩＣ复合体,基体相对堆积密度约７５％时,性能最佳。结论：ＭＩＣ是一种性能优良的新型渗透陶瓷材料,可满足     

晶化热处理制度对新型牙科云母基陶瓷弯曲强度的影响

目的：分析不同晶化温度和晶化时间对新型牙科云母玻璃陶瓷弯曲强度的影响,探讨该材料适用于牙科的最佳热处理制度。方法：将材料分为7组,采用一段晶化法,分别按照不同晶化温度/不同晶化时间进行热处理。测量其三点弯曲强度,并进行X射线衍射（XRD）及扫描电镜（SEM）观察。结果：随晶化温度升高,晶化时间延长,弯曲强度呈先上升后下降趋势,680℃晶化2h弯曲强度可达到173.68MPa。结论：该材料有优异的加工性能,是一种很有前途的牙科全瓷材料。     

GI-Ⅱ型渗透陶瓷氧化铝粉体的研究

目的:研究GI-Ⅱ型渗透陶瓷氧化铝粉体和坯体的特征,分析其形成氧化铝多孔结构的机制。方法:X衍射分析氧化铝粉体的晶型,粒度分析仪测试其粒度组成,扫描电镜观察坯体的微观结构。结果:氧化铝晶体是结构最紧密、最稳定的纯A型氧化铝晶型。氧化铝粉体中小于015Lm的细颗粒占9 wt%,粗颗粒集中在115~315Lm,占 75 wt%。扫描电镜观察坯体断面发现许多细小的颗粒均匀地附着在大颗粒表面,大小颗粒分散均匀,堆积较为密实。结论:氧化铝的晶型、粒度分布、颗粒分散,有利于形成多孔可渗透氧化铝骨架,是GI-Ⅱ型渗透陶瓷预制体的材料基础,也是复合体强度提高的关键。     

干湿环境下循环载荷对氧化锆-饰面瓷叠层瓷结构抗弯强度的影响

目的:比较干燥和唾液浸泡环境下动态循环加载对氧化锆/饰面瓷叠层瓷结构抗弯强度的影响。方法:制作氧化锆/饰面瓷叠层瓷结构圆片试件30个,随机分为干燥和唾液浸泡两组,循环加载10000次后进行双轴弯曲测试,光学显微镜观察其表面损伤及断裂面形貌。结果:在干燥环境下,经过10000次循环疲劳实验后,表面裂纹主要为赫兹锥状裂纹,破碎模式主要为完全断裂。而在唾液环境下,经过疲劳实验后,表面裂纹除了赫兹锥状裂纹外还有环状裂纹,破碎模式主要为饰瓷脱瓷,而且在干燥环境下的样品抗弯强度比在湿润环境下平均要高70%。结论:口腔内氧化锆全瓷修复材料长期使用后出现性能下降的疲劳现象,与牙科陶瓷修复体处于充满唾液的水环境有关。     

牙科渗透陶瓷用着色玻璃粉的制备与性能研究

目的:研究渗透陶瓷用着色玻璃粉的制备方法与相关性能。方法:将玻璃原料混匀烘干后放入氧化铝坩埚,在1400℃下熔融2h制成玻璃,测试玻璃的各种物理及力学性能。结果:差热分析显示玻璃的转换温度在690℃,在20℃-600℃之间,玻璃的热膨胀系数为6.2×10-6℃-1 ,密度2.23g/cm3,抗弯强度118Mpa,断裂韧性1.22Mpam1/2,维氏硬度7.4GPa。结论: 本研究所添加着色氧化物不影响渗透玻璃的物理及力学性能,制备的着色玻璃粉与多孔氧化铝预烧体有良好的物理与化学匹配性。     

GI-Ⅱ型渗透陶瓷断裂韧性测试

目的:测试并比较GI-Ⅱ型渗透陶瓷和In-ceram的断裂韧性和硬度。方法:制备GI-Ⅱ型渗透陶瓷和In-ceram圆盘形试件,研磨抛光。在维氏硬度仪上测试断裂韧性和硬度。断裂韧性数据采用Weibull分析。结果:GI-Ⅱ型渗透陶瓷和In-ceram的断裂韧性和硬度分别是3.05±0.06MN·m~(-1.5),12.66±0.33GPa和3.86±0.25MN·m~(-1.5),14.63±0.43GPa。Weibull 模数分别是46.93和15.00。结论:GI-Ⅱ型渗透陶瓷的断裂韧性和硬度比In-ceram低,但明显高于其它传统牙科陶瓷,而且其较高的Weibull模数表明其较好的材料均质性。     

牙科着色氧化锆陶瓷饰瓷前后的力学性能及断裂模式分析

目的:本研究对牙科氧化锆陶瓷着色及构筑饰面瓷前后的力学性能及断裂模式进行分析.方法:球磨混合一定组分的着色剂(氧化铁及氧化铈)和3Y-TZP(钇稳定氧化锆)粉体制备着色氧化锆陶瓷.根据ISO6872牙科陶瓷标准,制备着色和未着色氧化锆陶瓷的三点弯曲强度样品和构筑饰面瓷后的双层瓷样品,核心瓷与饰面瓷的厚度比为1:1.对所获得样品进行三点弯曲强度、断裂韧性和维氏硬度测试.采用X射线衍射(XRD)分析物相结构,扫描电镜(SEM)观察样品的断裂模式.结果:白色氧化锆陶瓷与着色氧化锆陶瓷的三点弯曲强度分别为1301 MPa和1203:MPa,统计学结果显示二者间没有明显差异,构筑饰面瓷后的三点弯曲强度分别为817 MPa和803 MPa,统计学结果显示二者间没有明显差异,但构筑饰面瓷后比单一材料样品强度降低,二者间有显著差异.在所有的双层瓷样品中,断裂模式的应力位移曲线显示为单峰断裂模式,断裂起始于核心瓷的张应力面中心区域同时发生饰面瓷的破碎和瓷层剥脱.结论:对氧化锆粉体的适当着色并没有明显影响材料的机械性能,着色和未着色氧化锆材料与饰面瓷具有良好的物理匹配性.     

Biaxial flexure strength determination of endodontically accessed ceramic restorations

Objectives

To report analytic solutions capable of identifying failure stresses from the biaxial flexure testing of geometries representative of endodontic access cavities prepared through dental restorative materials.

Methods

The ring-on-ring biaxial flexure strength of annular discs with a central circular hole supported peripherally by a knife-edge support and loaded evenly at the upper edge of the central hole were solved using general expressions of deformations, moments and shears for flat plates of a constant thickness. To validate the solutions, finite element analyses were performed. A three-dimensional one-quarter model of the test was generated using a linear P-code FEA software and the boundary conditions represented the experimental test configuration whereby symmetry planes defined the full model. To enable comparison of the maximum principal stresses with experimental derived data, three groups of nominally identical feldspathic ceramic disks (n = 30) were fabricated. Specimens from Group A received a 4 mm diameter representative endodontic access cavity and were tested in ring-on-ring. Group B and C specimens remained intact and were tested in ring-on-ring and ball-on-ring, respectively, to give insight into strength scaling effects. Fractography was used to confirm failure origins, and statistical analysis of fracture strength data was performed using one-way ANOVAs (P < 0.05) and a Weibull approach.

Results

The developed analytical solutions were demonstrated to deviate <1% from the finite element prediction in the configuration studied. Fractography confirmed the failure origin of tested samples to coincide with the predicted stress maxima and the area where fracture is observed to originate clinically. Specimens from the three experimental groups A–C exhibited different strengths which correlated with the volume scaling effects on measured strength.

Significance

The solutions provided will enable geometric and materials variables to be systematically studied and remove the need for load-to-failure ‘crunch the crown’ testing.     

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.     

The strength of sintered and adhesively bonded zirconia/veneer-ceramic bilayers

Objectives

Recently all-ceramic restorative systems have been introduced that use CAD/CAM technology to fabricate both the Y-TZP core and veneer-ceramic layers. The aim was to identify whether the CAD/CAM approach resulted in more favourable stressing patterns in the veneer-ceramic when compared with a conventionally sintered Y-TZP core/veneer-ceramic.

Methods

Nominally identical Vita VM9 veneer-ceramic disc-shaped specimens (0.7 mm thickness, 12 mm diameter) were fabricated. 20 specimens received a surface coating of resin-cement (Panavia 21); 20 specimens were bonded with the resin-cement to fully sintered Y-TZP (YZ Vita Inceram Vita) discs (0.27 mm thickness, 12 mm diameter). A final series of 20 Y-TZP core/veneer-ceramic specimens were manufactured using a conventional sintering route. Biaxial flexure strength was determined in a ball-on-ring configuration and stress at the fracture origin calculated using multilayer closed-form analytical solutions. Fractography was undertaken using scanning electron microscopy. The experimental test was simulated using Finite Element Analysis. Group mean BFS were compared using a one-way ANOVA and post hoc Tukey tests at a 95% significance level.

Results

Resin cement application resulted in significant strengthening of the veneer-ceramic and further significant strengthening of the veneer-ceramic (p < 0.01) occurred following bonding to the Y-TZP core. The BFS calculated at the failure origin for conventionally sintered specimens was significantly reduced when compared with the adhesively bonded Y-TZP/veneer-ceramic.

Conclusions

Under the test conditions employed adhesive cementation between CAD/CAM produced Y-TZP/veneer-ceramic layers appears to offer the potential to induce more favourable stress states within the veneer-ceramic when compared with conventional sintered manufacturing routes.

Clinical significance

The current investigation suggests that the stressing patterns that arise in all-ceramic restorations fabricated using CAD/CAM for both the core and veneer-ceramic layers differ from those that occur in conventionally sintered bilayer restorations. Further work is required to ascertain whether such differences will translate into improved clinical outcomes.     

Application of analytical stress solutions to bi-axially loaded dental ceramic–dental cement bilayers

OBJECTIVE: Increased consideration of dental ceramics and dental cements as a singular structural unit for in-vitro mechanical testing has resulted in the reporting of a wide range of analytical methods to calculate the failure stresses. Therefore a comparison of observations between studies is complicated by the use of dissimilar stress solutions despite the employment of a similar testing methodology and specimen geometry. MATERIALS AND METHODS: Three analytical solutions to calculate failure stresses in bi-axially loaded dental ceramic-dental cement bilayers were appraised for a commonly utilized testing geometry (ball-on-ring). Clinically relevant datasets were generated from the bi-axial flexure testing of uncoated and dental cement coated aluminous core ceramic exposed to differing ceramic surface preparations. A Weibull statistical approach was utilized in order to provide insight into the impact of the analytical method on both the scale (sigma(0)) and distribution (m) of the failure stress data. RESULTS: Calculation of the bi-axial flexure stress utilizing Timoshenko's analysis resulted in an increase in sigma(0) for the uncoated (6%) and dental cement coated (11-12%) aluminous core ceramic, when compared with the bilayered solutions reported by Rosenstiel and Hsueh. However, the shape of the failure distributions illustrated by the consistency of m and associated 95% confidence intervals was not influenced by the analytical stress solution employed. SIGNIFICANCE: The choice of the analytical method chosen to calculate failure stresses in bi-axially loaded dental ceramic-dental cement bilayers will impact on the magnitude of the reported strength. Comparison between the failure stresses of uncoated and cement coated dental ceramics is more accurately represented by bilayer solutions, which account for the mismatch between the elastic constants of dissimilar materials. However, within the context of dental cement coated dental ceramics of clinically relevant dimensions, the choice of solution is unlikely to impact on the interpretation of the observations previously reported in the dental literature.     

氧化铝渗透陶瓷底瓷全瓷冠2年临床观察

目的 探讨氧化铝渗透陶瓷作为全瓷修复体底瓷的修复效果,为临床推广应用提供参考。方法 61例门诊患者,修复体159件,其中上颌98件,下颌61件。前牙全冠132个,后牙全冠27个。通过12～24个月的观察,采用美国加利福尼亚牙科学会的质量评价体系对氧化铝渗透陶瓷作为底瓷所做的前、后牙全冠修复进行临床效果评价。结果 对61例患者159颗全冠的临床观察结果 表明,氧化铝渗透陶瓷作为底瓷所制作的全瓷修复体具有良好的的边缘密合性,色泽稳定,强度高,其失败率为1.25%,效果满意。结论 氧化铝渗透陶瓷作为底瓷的全瓷冠修复是一种效果良好的全瓷修复方式。     

渗透陶瓷与松风AL饰面瓷的热匹配性研究

目的 考察氧化铝玻璃渗透陶瓷与松风Vintage AL饰面瓷的热匹配性,以指导临床合理应用.方法 制作氧化铝玻璃渗透陶瓷与松风Vintage AL饰面瓷25mm× 5.0mmx5.0 mm试件,测定550℃至25℃区间的热膨胀曲线及热膨胀系数,评价二者热匹配性.结果 氧化铝玻璃渗透陶瓷,AL牙本质瓷,AL不透明牙本质瓷的热膨胀系数分别为7.6×10-6/℃,6.7x10-6/℃,7.1×10-6/℃,三者之间均能满足热匹配.结论 氧化铝玻璃渗透陶瓷与松风Vintage AL热匹配性良好,完全满足临床需要.     

The influence of clinically induced variability on the bi-axial fracture strength of aluminous core porcelain discs

Objective: The proportions of the constituents required to produce a porcelain slurry used in crown construction are assessed by experience so that variability is inevitable. The present study investigated the strength dependence of porcelain specimens on slurry consistency.

Methods: Vitadur-N core porcelain was formed into discs and the mean fracture strength, standard deviation and associated Weibull Moduli (m) determined as a function of slurry consistency using bi-axial flexure (ball-on-ring) by fracturing sets of 30 specimens prepared to different powder contents for a constant 0.4 ml of liquid.

Results: The strength data for the porcelain discs showed variation in magnitude and consistency ranging from 145±16.5 MPa (m=9.7±1.8) at 1.2 g to 155±13.8 MPa (m=12.3±2.2) at 1.4 g and 142±13.7 MPa (m=11.7±2.1) at 1.6 g of powder. Increasing or decreasing the powder content of the slurry (related to specimens condensed using 1.4 g of powder) resulted in an increase in the apparent porosity and a decrease in the apparent solid density.

Conclusions: There was no significant decrease in the mean bi-axial flexure strengths for the slurry consistencies investigated. However, the reliability of the fracture strength data did vary significantly. The results suggested that an optimum consistency exists (wherein consistent reproducibility of test results was achieved) and appears to have implications for laboratory testing of materials since a comparison between materials can only be achieved if specimen preparation occurs consistently between test centres for all the materials under investigation.     

The reliability in flexural strength testing of a novel dental composite

Objectives. To investigate the reliability of bi-axial flexure and three-point flexure testing of an experimental, low-shrink oxirane-based dental composite, EXL596 compared with two conventional methacrylate based restoratives, Z250 and Z100.

Methods. Specimens (n=20) of a novel oxirane-based composite and two commercially available methacrylate based composites were fabricated for flexural testing to evaluate mean bi-axial flexure strengths, three-point flexure strengths and the associated Weibull moduli (m) following 24 h immersion in a lightproof waterbath maintained at 37±1 °C.

Results. Mean bi-axial flexure strengths and the associated m of EXL596, Z250 and Z100 were 168±11 MPa (m=16.2±4), 140±12 MPa (m=11.9±3) and 126±13 MPa (m=10.2±2), respectively. Three-point flexure strengths and the associated m of EXL596, Z250 and Z100 were 113±15 MPa (m=9.2±2), 92±10 MPa (m=8.5±2) and 79±16 MPa (m=6.3±1), respectively.

Conclusions. The present investigation suggests that bi-axial flexure strength testing of dental resin-based composites provides a more reliable testing method than three-point flexure. The increased reliability was considered in terms of the associated Weibull moduli following bi-axial flexure testing as a result of the elimination of the additional induced variability introduced during the curing regime of three-point flexure specimens.     

玻璃渗透氧化铝陶瓷树脂粘接耐久性的研究

目的分析含有不同类型酸性树脂单体的硅烷偶联剂及不同类型树脂粘接剂的相互组合对玻璃渗透氧化铝陶瓷树脂粘接耐久性的影响。方法使用3种硅烷偶联剂处理玻璃渗透氧化铝陶瓷的表面,使用2种双重固化树脂粘接剂与之粘接。测量试件在0和30 000次冷热循环后的粘接强度。结果冷热循环前,粘接剂A与未硅烷化处理陶瓷间的粘接强度显著低于其他硅烷化处理组,粘接剂A、B与偶联剂B处理的陶瓷间的粘接强度显著低于其与偶联剂A和C的粘接强度。冷热循环30 000次后,粘接剂A与未硅烷化处理陶瓷组的试件全部脱落;而其他硅烷化处理陶瓷组中,只有偶联剂A处理的陶瓷表面与粘接剂A和B间的粘接强度达到了5 MPa以上。结论使用10-甲基丙烯酰氧癸基磷酸酯作为硅烷水解剂的硅烷偶联剂处理的玻璃渗透氧化铝陶瓷能够与不同类型的树脂粘接剂获得较好的粘接耐久性。     

The deformation and strength of a dental ceramic following resin-cement coating

Objectives

The hypothesis tested was that processing, pre-cementation and cementation techniques can modify the profilometrically measured deformation of a ceramic.

Methods

Three-point flexural moduli of a resin-cement were characterised following light irradiation at 430 and 180 mW cm⁻². Thirty IPS e.max Ceram discs were prepared and a reference surface produced by polishing. Discs were annealed, alumina particle air abraded and resin-coated. Profilometric evaluation was performed following each pre-cementation or cementation operative technique using a contact diamond stylus profilometer. Bi-axial flexure strength of the resin-coated discs, light irradiated at 430 and 180 mW cm⁻² (Groups A and B), and the un-coated discs (Group C) was determined. Data were analysed by a one-way analysis of variance with post hoc Tukey tests (P < 0.05), or repeat measure analyses when appropriate.

Results

Annealing (at 510 °C for 40 min) resulted in a significant reduction (P < 0.001) in the characterised mean deflection, as did alumina particle air-abrasion (P < 0.001). Resin-cement coating significantly increased the mean deflection for Groups A and B (P < 0.001) specimens against the uncoated state. Furthermore no significant impact of increasing time or irradiation intensity on the mean deflection was identified. The mean bi-axial flexure strength was significantly increased (P < 0.001) after resin-coating (Groups A and B) when compared with Group C specimens although no difference between Groups A and B specimens (P = 0.291) was identified.

Conclusion

The results of the profilometric technique in combination with the strength supported a strengthening mechanism sensitive to shrinkage stress generation associated with the polymerisation of resin-cements.