饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响

目的：研究饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响。方法：常规 CAD-CAM制作氧化锆筒状基底冠25个,厚度均为0．5 mm,随机分为 A、B、C、D、E 5组,饰面瓷厚度依次为0．5、1．0、1．5、2．0、2．5 mm。万能材料试验机测试各组试件抗压缩破坏力值。采用 SPSS13．0统计软件对测试结果进行统计分析。用扫描电镜（SEM）观察试件断裂面微观结构。结果：A ～E 组试件抗压缩破坏力值依次为：（1279．96±42．85）N、（2235．44±50．14）N、（2216．38±48．97）N、（2169．22±60．40）N、（2028．70±47．37）N。A 组、E 组氧化锆全瓷修复体的抗压缩破坏力值均低于其他3组（P ＜0．01）;其余组间抗压缩破坏力值无统计学差异（P ＞0．05）。扫描电子显微镜观察发现,A 组、E 组氧化锆全瓷修复体基底瓷－饰面瓷结合界面处不平坦,较为疏松;饰瓷层出现气孔及微裂纹增多、增大。结论：饰面瓷厚度低于1．0 mm 及高于2．0 mm 时,修复体的微观结构可能会受到影响,从而氧化锆全瓷冠整体抗压缩破坏力的性能受影响,建议临床应用时严格控制饰面瓷厚度。     

云纹干涉法应用于金瓷界面抗断裂能力研究的初步探讨

目的探讨云纹干涉法在金瓷界面抗断裂能力研究中的应用。方法在5组金瓷厚度不同的试件表面制作光栅,加载后采集u场及。场云纹干涉条纹,推算各组金瓷界面断裂韧性Jc值并观测裂纹扩展方向。结果加载条件下,裂纹周围显示应力集中区,条纹随载荷增加逐渐变密。由云纹干涉图位移场算得各组试件金瓷界面断裂韧性各不相同,其裂纹扩展方向也有差异。结论云纹干涉法适用于金瓷界面断裂韧性的研究,也可用于观测并预测裂纹的扩展方向及趋势。     

瓷层厚度对金瓷修复体颜色的影响

目的 探讨瓷层厚度对金瓷修复体颜色的影响。方法 选用VMK 95 METALL KERAMIK,A2色瓷粉,Ni-Cr非贵金属体系烤瓷合金(德国),常规制作金瓷试件(金属基底厚为0.3mm,瓷厚度分别为0.5mm,1.0mm,1.5mm,2.0mm,2.5mm各10个试件,分成5组)。用Shade eye EX(松风,日本)电脑比色仪检测试件的颜色。结果 ①不同瓷层厚度,其金瓷修复体的颜色、色相、彩度和明度均不同,并有显著差异(P<0.01)。②随着瓷厚度的增加,试件颜色有从A2→A1的变化趋势;试件的色相有从R1→R2的变化趋势;试件的彩度值和明度值均变小。结论 瓷层厚度太大或太小都会影响金瓷修复体颜色,最佳瓷厚度为(1～2.5mm)。由于Vita Lumin比色板与中国人牙色相比,颜色分布不均匀,如要减少颜色的明度或彩度,可适当增加瓷厚度以弥补Vita Lumin比色板的局限。     

遮色瓷厚度对金瓷修复体颜色的影响

目的 探讨遮色瓷层厚度对金瓷修复体颜色的影响，以指导其制作工艺，提高修复体美观方面的满意度。方法 选用Ni-Cr非贵金属体系烤瓷合金(德国)，常规制作金瓷试件(金属基底厚为0．3mm)，在其上涂布不同遮色瓷厚度(0.15～0．30mm)，选用VMK95METALL KERAMIK A2色瓷粉进行烧结(瓷厚度为1．0mm)，用Shade eye EX(松风，日本)电脑比色仪检测试件的颜色。结果 金瓷修复体遮色瓷层厚度的变化对修复体的颜色、彩度、明度和色相均有影响，并有显著差异。随着遮色瓷层厚度的增加，试件的颜色有从A1→A2的变化趋势；试件的彩度值和明度值均增大，但当遮色瓷层超过一定厚度(0.20～0.25mm)时，彩度值和明度值反而变小；试件的色相有从R1→R2的变化趋势。结论 遮色瓷的最佳厚度为0.20—0．25mm；由于Vita Lumin比色板与中国人牙色相比，颜色分布不均匀，缺乏明度值和彩度值较高的偏红黄色调，适当增加遮色瓷厚度可以增加红色成分，增加明度值和彩度值，以弥补Vita Lumin比色板的局限。     

RG实验低熔瓷与钛的结合性能分析

目的　测试作者自行研制的RG实验低熔瓷与钛的结合性能。方法　铸造 1 0mm×5mm× 1 4mm钛片 5个 ,于钛片表面依次熔附RG实验遮色瓷和牙本质瓷总厚度 1mm。采用扫描电镜观察钛瓷界面形貌并做能谱分析。采用铸造法制备 2 8mm× 3mm× 0 5mm的NiCr合金试件6个 ,纯钛试件 1 8个。于NiCr合金试件中份 8mm× 3mm处熔附 1mmVita常用瓷 ;钛试件分为 3组 ,每组 6个 ,于试件中份 8mm× 3mm处分别熔附 1mmRG实验低熔瓷、VITATITANKERAMLK瓷和NoritakesuperporcelainTi 2 2瓷。在实验机上采用 3点弯曲法测试金瓷分离时的载荷。采用金瓷修复体制作方法制作RG实验钛瓷冠。结果　扫描电镜观察发现遮色瓷与钛之间无明显缝隙存在 ,遮色瓷与钛之间存在一个约 1 μm过渡层 ,能谱分析发现该过渡层的主要化学元素为Ti、Si、O。NiCr合金 VITA瓷试件的分离加载为 (1 2 733± 3 2 97)N ,钛 VITATITAN、钛 Noritake瓷试件和钛 RG实验瓷的分离加载分别为 (7 2 33± 2 539)N、(5 533± 1 1 99)N和 (6 31 6± 1 433)N。经统计检验 ,3种钛瓷试件之间差异无显著性 (P >0 0 5) ;而 3种钛瓷样本的分离加载均明显低于NiCr合金与瓷的分离载荷 ,差异有极显著性 (P <0 0 1 )。钛瓷冠瓷面完整无裂纹。结论　RG瓷与钛具有良好的结合     

氧化锆基底和饰瓷结合强度的分析

目的分析和比较几种全瓷系统基底和饰瓷的结合强度。方法制作直径为8 mm、厚度为3 mm的Lava、 Cercon、IPS e.max ZirCAD、Procera试件各20个,分别为Lava组、Cercon组、IPS e.max ZirCAD组、Procera组。每组各选10个试件表面烤制厚度为1 mm的相应饰瓷,10个试件表面烤制厚度为2 mm的相应饰瓷。对试件进行剪切强度的测定和断裂模式的观察。结果饰瓷厚度为1 mm时,Lava、Cercon、IPS e.max ZirCAD、Procera组的剪切强度分别为：（13.82±3.71）、（13.24±2.09）、（6.37±4.15）、（5.19±5.31）MPa;饰瓷厚度为2 mm时,各组的剪切强度分别为：（38.77±1.69）、（21.67±3.34）、（12.70±4.24）、（9.94±6.67）MPa。Lava组和Cercon组的剪切强度高于IPS e.max ZirCAD组和Procera组（P<0.05）,饰瓷厚度为2 mm的试件的剪切强度高于饰瓷厚度为1 mm的试件（P<0.05）。各组试件破坏模式均以界面破坏为主。结论氧化锆基底和饰瓷的结合强度因基底材料的不同而不同,饰瓷的厚度对结合强度有明显的影响。     

种植金瓷固定桥的瓷层厚度对瓷裂影响的试验研究

作者研究了烤瓷厚度对松风一镍铬合金系列的种植金瓷固定义齿瓷裂的影响、结果表明：当瓷粉厚度达到3.5mm时，开始出现瓷裂；达到4mm时，全部样本产生瓷裂；连接体是产生裂纹的主要部位；用体视镜观察裂纹优于肉眼观察。提示应保证涂塑的体瓷粉厚度小于3．5mm，为了更好地满足此要求，可在种植体基桩与支架固位体之间做内冠。同时要求支架连接体外形和连接体处的瓷表面外形为平缓曲面，以避免连接体外的形状突然变化而引起的瓷裂     

钛的氧化行为对钛瓷结合力的影响

目的:观察钛的氧化行为对钛瓷结合力的影响。方法:铸造28mm×3mm×0.5mm的纯钛试件24个,喷砂、清洗后分为4组,每组6个,第1组不进行预氧化处理,第2、3、4组分别在750、800、900℃温度下,在烤瓷炉内进行预氧化处理5min。于每个金属试件中份8mm×3mm处,依次熔附Noritake TI-22瓷系统的黏结剂、遮色瓷、牙本质瓷,瓷层总厚度1mm。在拉伸试验机上采用三点弯曲法测试金瓷分离时的加载值。使用薄层X线衍射仪观察4组试件未附瓷的钛表面氧化膜中氧化物的种类。结果:不预氧化、750、800、900℃预氧化试件的金瓷分别加载(N)测试结果为10.33、9.98、5.53、3.37。不预氧化试件表面氧化膜中的氧化物全部是Ti6O;750、800、900℃试件的氧化膜中的氧化物为Ti6O和TiO2,900℃试件氧化膜中的TiO2的量明显增加。结论:随着氧化温度的升高,氧化膜中TiO2含量明显增加,钛瓷结合力显著下降,说明钛的高温氧化行为对钛瓷结合力有不利的影响。     

瓷层厚度对牙龈瓷颜色的影响

目的　了解牙龈瓷的颜色再现受瓷层厚度影响的变化规律。方法　采用分光光度计(PR-650)测量不同厚 度Shofu vintage pink龈色瓷,不同厚度牙本质瓷及不同颜色的遮色瓷和牙本质瓷对金瓷试件颜色改变的影响。结果 　当Shofu vintage pink龈色瓷厚度从0·3 mm增加到0·9 mm,金瓷试件的L*值不断降低,a*值不断升高;牙本质瓷 厚度的增加使试件颜色向亮度低,偏红方向变化;不同颜色遮色瓷、牙本质瓷层厚度会导致龈色瓷表面的颜色改 变。结论　瓷层厚度可以影响牙龈瓷的颜色再现。     

除气和预氧化对含钛镍铬合金金瓷结合强度的影响

目的研究上瓷前含钛镍铬合金除气和预氧化对其金瓷结合强度的影响。方法三点弯曲法测定A组（除气）、B组（预氧化）和C组（无热处理）试件的金瓷结合强度,扫描电镜和X线衍射分析金瓷界面。结果 A组金瓷结合强度为（39.812±2.466）MPa,B组为（37.406±5.238）MPa,C组为（32.704±3.140）MPa。A组与B组间差异无统计学意义（P〉0.05）,但2组均明显大于C组,且差异有统计学意义（P〈0.05）。扫描电镜下,3组均可见金属与瓷之间有一清晰的过渡层,A组和B组界面过渡层厚度约10～15μm,金瓷结合良好,无明显的中间层、气泡等缺陷。C组过渡层厚度约5～10μm,见明显孔洞和裂纹。X线衍射分析,3组金瓷界面过渡层局部出现Sn、Ti、Si的聚集,Ti元素呈不规则扩散曲线。结论除气而无需再预氧化也能获得较高的金瓷结合强度,预氧化能提高金瓷结合强度,无热处理试件金瓷结合强度较低。     

The influence of interfacial surface roughness on bilayered ceramic specimen performance.

OBJECTIVES: The aim of the current study was to assess the influence of interfacial surface roughness on the performance of bilayered ceramic composite disc-shaped specimens. METHODS: Specific surface flaw distributions were introduced to a series of standard aluminous core porcelain disc specimens (12 mm diameter, 1.7 mm thickness) prior to bilayering with dentin porcelain. Mean flexure strengths, standard deviations and associated Weibull moduli (m) were determined using bi-axial flexure (ball-on-ring) for each series of 30 bilayered specimens. RESULTS: The mean bi-axial fracture strengths of bilayered specimens resulted in significant differences between specimen groups with the smoothest interfacial roughness recording the highest strength and fracture strength reliability. Specimen delamination was identified in five of the bilayered group with the smoothest interfacial roughness compared with no specimen delaminations in the rougher interface groups. However, fracture occurred in the weaker dentin layer rather than along the interface between the dentin and core porcelain for specimens in these rougher interface groups. CONCLUSIONS: A smoother interfacial surface roughness resulted in increased performance, namely increased strength and reliability amongst the bilayered dental ceramic composite specimens examined in the current investigation. The incidence of complete or partial delamination of the reinforcing core and aesthetic dentin was increased for these specimens since the reduced tortuosity of the interface between porcelain layers fails to restrict propagation of a crack front along the interface.     

The effect of porcelain thickness and surface liner application on the fracture behavior of a ceramic system

Objectives

To determine the effect of porcelain thickness and the application of a surface liner (SL) on the flexural strength (σ) of a ceramic system.

Methods

One hundred twenty bar-shaped specimens of yttria-stabilized zirconia-based ceramic were fabricated and randomly divided into two groups according to the application of SL: A - applied; B - not applied. The specimens were further divided according to the porcelain veneer thickness (n = 20): 0-0.5 mm; 1-1.0 mm; 2-2.0 mm. All specimens were tested in 3-point bending with the porcelain under tension. The maximum load was recorded at first sign of fracture, the σ was calculated and the mode of failure was determined. Data was statistically analyzed using one-way ANOVA, Tukey (α = 0.05) and Weibull distribution.

Results

The SL application had no effect (p = 0.723) while the porcelain thickness had a significant effect (p = 0.000) on the mean σ values. No significant differences in mean σ values were found with same porcelain thickness. A 0.5-mm thick porcelain layer (groups A0 and B0) showed greater mean σ values than other groups. The Weibull modulus (m) ranged from 6 (groups A1 and B2) to 9 (groups A0, A2 and B0). The predominant mode of failure for all groups was fracture initiation at the porcelain surface propagating to the ceramic interface.

Significance

The porcelain thickness influenced the mean σ values, but the SL had no significant effect on the flexural strength and the mode of failure of the ceramic system examined.     

Tensile stress in glass-ceramic crowns: effect of flaws and cement voids.

The objective of this study was to analyze the relative effect of loading site, occlusal thickness, ceramic flaws, elastic modulus of the cement, and voids in the cement layer on tensile stress that develops in molar glass-ceramic crowns under applied loads. Finite-element stress analyses were performed. Resin cement with a thickness of 0.05 mm was used. A central conical flaw (0.05 mm [diameter] x 0.05 mm) and a circular grooved flaw located under the cusp tips were included in all flaw cases. A void space confined within the occlusal region of the cement layer was also included in selected cases. For a ceramic thickness of 0.5 mm and a vertical distributed load applied at a distance of 1.3 mm from the vertical axis, the maximum tensile stresses were 100 MPa for a crown with flaws and a void, 87 MPa for a crown with no flaws and a void, and 75 MPa for a crown with flaws and no void. For a 1.5-mm-thick crown with flaws and a void, the tensile stress decreased to 22 MPa. When the load of 600 N was concentrated at the central point of the occlusal region, the peak tensile stress in a crown with flaws and no void was increased to 325 MPa. For the conditions analyzed in this study a large void in a flawed occlusal region of a thin molar crown (0.5 mm) is proposed as a mechanism of crown failure.     

Influence of the thickness of metal and porcelain upon metal-ceramics (author's transl)]

This paper deals with the strength of metal-ceramics and the influence of the thickness of metal and porcelain layer. The metal-ceramic specimens, 30 mm long and 10 mm wide of various each thickness, supported at each ends, were tested by bending to obtain the transverse strength. The thickness of metal layer was changed from 0.2 mm to 1.0 mm, while that of porcelain layer was changed from 0.5 mm to 1.3 mm respectively. Interaction of the thickness of metal or porcelain layer to the fixed total thickness was also investigated comparing with the results of the experiment in which the thickness of one side was constant. From the load-deflection diagram, the maximum work before breaking was surveyed and compared. Main results were as follows. 1) In case of the same total thickness of metal-ceramics, the thicker the metal layer, the greater the transverse strength, maximum work before breaking and maximum deflection. 2) When the metal thickness exceeded one half of the porcelain layer, the transverse strength increased in comparing with value of porcelain itself. 3) The maximum deflection of metal-ceramics by bending before breaking was approximately three or four times as great as that of simple porcelain. 4) The work of the metal-ceramics by bending before breaking was approximately two or three times as that of the simple porcelain. 5) It was imagined that the total strength of the metal-ceramics would be affected by the hardness of the constituent metal and boundary bonding strength.     

钴铬合金表面喷砂及烤瓷厚度对金-瓷结合强度影响

目的探讨不同的喷砂处理及瓷层厚度对钴铬合金烤瓷冠金-瓷结合的影响。方法处理因素有两点：①喷砂直径,60目及90目的氧化铝,压力为0.4MPa,②瓷层厚度,1.5mm及2.0mm。实验分为四组：A组,60目砂、1.5mm厚度瓷层;B组,60目砂2.0mm厚度瓷层;C组,90目砂1.5mm厚度瓷层;D组,90目砂2.0mm厚度瓷层。按照要求制作剪切强度试件,用万能试验机进行剪切强度测试。应用SPSS10.0软件进行统计学分析。结果各实验组抗剪切强度分别为：A组33.5987±5.3926MPa,B组29.0446±2.4165MPa,C组27.9936±2.7097MPa,D组21.9586±0.2209MPa;统计分析结果表明,A组与D组之间的差异有统计学意义（P〈0.05）,而其余各组之间的差异均无统计学意义。结论喷砂用的氧化铝粒径较大者,钴铬合金表面的金瓷结合力较强;1.5mm瓷层组的金瓷结合力大于2.0mm瓷层组。     

An in vitro study to investigate the load at fracture of Procera AllCeram crowns with various thickness of occlusal veneer porcelain

PURPOSE: The aim of this study was to investigate the effect of occlusal veneer porcelain thickness on the load at fracture of Procera AllCeram crowns. MATERIALS AND METHODS: Fifty resin dies were manufactured to incorporate the features of an all-ceramic crown preparation on a premolar tooth. Fifty corresponding crowns were constructed and divided into five groups. Groups 1, 2, 3, and 4 were crowns with 0.6-mm-thick Procera cores and 0.4-mm-thick axial veneer porcelain and occlusal veneer porcelain thicknesses of 0.0 mm, 0.4 mm, 0.9 mm, and 1.4 mm, respectively. Group 5 specimens consisted of 0.6-mm-thick In-Ceram cores with 0.4 mm of axial porcelain and 0.4 mm of occlusal porcelain. The crowns were cemented onto their respective dies with a resin luting agent. Specimens were stored in distilled water at 37 degrees C for 24 hours prior to placing them in a universal testing machine and applying a controlled compressive load at a cross-head speed of 0.1 mm/min until fracture occurred. RESULTS: The mean loads at fracture were 419 N (group 1), 702 N (group 2), 1,142 N (group 3), 1,297 N (group 4), and 732 N (group 5). Statistical analysis revealed significant differences (P < .05) in the load at fracture between the groups, except for between groups 2 and 5. CONCLUSION: Increasing the thickness of the occlusal veneer porcelain increased the load at fracture for Procera AllCeram crowns. There was no significant difference in load at fracture between the Procera and In-Ceram crowns.     

Influence of initial flaw size on crack growth in air-tempered porcelain

Tempering of dental porcelain by forced convective cooling in air has been shown previously to inhibit the sizes of cracks induced in porcelain surfaces. However, the depth of compressive stress that is produced by tempering of feldspathic porcelain has not been determined. It can be assumed that the potential of tempered specimens to inhibit crack formation is reduced as the flaw size exceeds some critical value, since the compressive stress decreases with distance from the surface. The objective of this study was to test the hypothesis that the effectiveness of tempering stress in porcelain decreases with the increasing size of initial surface flaws. Body porcelain discs, 16 mm in diameter and 2 mm in thickness, were tempered (T) by forced convective cooling in air from an initial temperature of 982 degrees C at a pressure of 0.34 MPa for 90 s. Nontempered control discs (NT) were slowly cooled by termination of power to the furnace. The half crack-lengths (c) of surface cracks induced by a Vickers microhardness indenter at loads ranging from 2.0 to 39.2 N were determined initially and over a period of 24 h. The initial half crack-lengths, co, for the tempered specimens were significantly smaller (p less than 0.05) than the corresponding values for the slow-cooled specimens. The mean value of the stress corrosion susceptibility coefficient (n), which is inversely related to the slope of log crack size vs. log time, was only slightly smaller for the NT specimen groups (15.3), compared with the mean value for the T groups (17.1).(ABSTRACT TRUNCATED AT 250 WORDS)