人工老化对全瓷贴面树脂粘结剂颜色稳定性的影响

目的研究人工老化对全瓷贴面树脂粘结剂颜色的影响。方法用VITABLOCS MARK-Ⅱ制作厚度为1 mm的试件40个,随机分为4组(n=10)。分别采用Superbond C&B化学固化粘结剂、VariolinkⅡ双重固化粘结剂、RelyX Veneer光固化粘结剂和Filtek Z350 Flow流动复合树脂进行粘结,4种粘结剂颜色均为A3。在黑暗环境下保持24 h后用色度计测量色度值。再将各组试件置于紫外光老化实验箱中进行老化后再次测量其色度值,比较4种树脂粘结剂的颜色稳定性。选定ΔE<3为临床可接受范围。结果 Superbond C&B、VariolinkⅡ、RelyX Veneer和Filtek Z350 Flow粘结剂的ΔE分别为2.32±0.21,2.50±0.29,0.68±0.24和0.79±0.20。其中Superbond C&B和VariolinkⅡ的ΔE高于其他组(P<0.05)。Superbond C&B和VariolinkⅡ之间,RelyX Veneer和Filtek Z350 Flow之间无显著性差异(P>0.05)。结论 4种树脂粘结剂在人工老化后均出现不同程度的颜色变化,但这种颜色改变程度在临床美学要求范围内。RelyX Veneer和Filtek Z350 Flow树脂具有较好的颜色稳定性。     

不同厚度饰瓷与基底瓷双层结构全瓷桥残余应力的有限元分析

目的:建立不同厚度饰瓷与基底瓷双层结构的后牙三单位全瓷桥有限元模型,分析饰瓷与基底瓷厚度对全瓷桥残余应力的分布及其影响。方法:使用WIELAND ZENOTEC Scan对上颌后牙三单位固定桥基牙标准模型进行三维光学扫描,在上述模型基础上通过WIELAND ZENOTEC Cad;Geomagic;CATIA构建三组不同厚度饰瓷与基底瓷双层结构后牙三单位全瓷桥实体模型,将模型导入ABAQUS6.10有限元软件,分析修复体从575℃降至室温25℃过程中残余应力的形成及分布。结果:全瓷修复体残余应力主要分布在饰瓷与基底瓷结合界面处,其中冠边缘、连接体处修饰瓷分布较薄的部位界面处残余应力较为集中,而在修饰瓷较厚的部位残余应力分布较为均匀。随着温度的降低,饰瓷与基底瓷结合界面的残余应力逐渐增大。随着饰瓷与基底瓷热膨胀系数之差逐渐增大和饰瓷厚度的增加,结合界面的残余应力也逐渐增大。结论:双层结构全瓷桥三维有限元模型的建立使得修复体残余应力分析得以实现。修饰瓷较薄和热膨胀系数差较大时残余应力分布较大,在进行全瓷桥修复时除饰瓷与基底瓷热膨胀系数匹配外,要保证饰瓷一定的厚度。     

全瓷贴面在前牙美容修复中的疗效观察

目的：探讨全瓷贴面在前牙美容修复中的疗效。方法：选择97颗前牙,全瓷贴面修复,并进行2年的随访,采用美国公共健康协会的修正标准进行评价分析。结果：97颗全瓷贴面在修复完成后6个月,六项评价指标均达到A级;修复完成后1年,修复体周围龋：2颗达到B级;修复完成后2年,2例患者(3颗牙)失访,修复体周围龋：2颗B级、1颗C级,修复体折断：1颗B级,基牙松动：2颗B级。结论：全瓷贴面在前牙美学修复中的临床效果是非常理想的。     

全瓷贴面的临床应用

目的：观察全瓷贴面用于变色前牙修复的临床效果。方法：选择38例患，共制作全瓷贴面152颗，随诊30个月，通过临床检查和患主观评价，观察临床效果，结果：临床检查修复效果显，患主观感觉光滑舒适，无牙龈炎症，无牙髓反应，结论：全瓷贴面修复效果好，是较为理想的变色前牙美容修复体。     

Effect of adhesives on bond strength of porcelain veneer to base metal alloy.

OBJECTIVE: The purpose of this in vitro study was to evaluate the bond strength of porcelain veneer to base metal alloy using different adhesive systems. METHOD AND MATERIALS: Eighty cylindrical models were cast in a nickel-chromium-beryllium base metal alloy. After they were mounted in self-cured acrylic resin, the surfaces of the specimens were air abraded. Specimens were divided into four groups of 20. Control porcelain disks were baked on the base metal. For the experimental groups, 60 porcelain disks were made. After 50-microm aluminum oxide sandblasting, a silane coupling agent was applied to the surface of the porcelain. The experimental groups were based on the type of adhesive used to bond porcelain to metal: Scotchbond Multipurpose and Duo Cement; One Coat Bond and Duo Cement; or Panavia 21 Ex. After 500 thermal cycles, the bonded porcelain specimens were placed under a continuous shear load of 2 mm/min until fracture occurred. RESULTS: Mean values for bond strength were 25.39 (control), 19.10 (Panavia 21 Ex), 15.81 (Scotchbond Multipurpose), and 13.69 MPa (One Coat Bond). Statistically significant differences in bond strength were noted between the control group and all the experimental groups. A statistically significant difference was observed between Panavia 21 Ex specimens and One Coat Bond specimens. CONCLUSION: Panavia 21 Ex provided an effective bond strength between a porcelain veneer and a base metal alloy, the closest of all the experimental groups to that of the control group.     

三维有限元法分析不同粘接剂层对瓷贴面应力分布的影响

目的：利用计算机生成下颌中切牙的三维实体模型和三维有限元模型,生物力学角度分析瓷贴面复合体粘接层的受力情况,以期为临床应用提供理论依据.方法：将Micro-CT获得的牙体原始数据导入Mimics10.01软件,利用topo算法和Ansa软件生成下颌中切牙三维实体模型和三维有限元模型;用有限元法分析瓷贴面复合体不同厚度的粘接层,在不同载荷条件下的应力分布规律,使用ABAQUS/Standard求解器对该计算模型求解,并进行应力分析.结果：获得较为精准的下颌中切牙三维实体模型和三维有限元模型;应力云图可见：垂直载荷下,Von Mises应力主要集中于舌面远中1/3处和粘接层切端中1/3处;斜向载荷下,Von Mises应力主要集中在唇面切端远中1/3处和舌面颈部远中1/3处;Von Mises应力值斜向加载均大于垂直向加载;不同载荷条件下粘结层厚度均为100um时Von Mises应力值最小.结论：下颌中切牙瓷贴面修复应重点注意粘接层切端边缘的处理,并引导下颌牙齿延牙体长轴受力;树脂粘接层在厚度为100um附近时更有利于瓷贴面的粘接效果.     

即刻牙本质封闭对瓷贴面预备后基牙敏感程度的影响

目的 评价牙本质即刻封闭技术对瓷贴面修复后基牙敏感的防治效果.方法 选择76名患者的138颗活髓前牙进行瓷贴面基牙预备后随机分为试验组和对照组.其中,试验组69颗牙齿,基牙预备后,用牙本质粘接剂Gingle bondⅡ)涂布于基牙表面再取印模;对照组69颗牙齿,基牙预备后直接取模.然后2组均常规制作临时冠粘接.在取模后...     

Oxidation of noble metal alloys for porcelain veneer crowns.

It has been found that oxide-forming elements in the alloy are important for the blood strength between the metal and the procelain. The purpose of the present investigation was to study the formation of oxides during pretreatment and firing of porcelain. Four commerically available Ceramo-Metal alloys were studied. The specimens were heated at 980 degrees C for five hours in air, and the weight was continuously recorded. In addition porcelain was fired on to the alloys. Metallographic examinations were conducted on both oxidized and fired speciments. The weight gain data also indicated an increased oxygen uptake with a larger amount of oxidizable elements in the alloy. Most of the oxygen gain and time indicated that the oxygen uptake was diffusion controlled. The weight gain data also indicated an increased oxygen uptake with larger amount of oxidizable elements in the alloy. Most of the oxygen in the oxidize alloys was located as oxide along grain boundaries in the metal.     

Clinical gap changes after porcelain firing cycles of zirconia fixed dentures

PURPOSE

The aim of this study was to measure the changes on the marginal and internal adaptation of zirconia based anterior fixed partial dentures after the porcelain firing process.

MATERIALS AND METHODS

A total of 34 anterior fixed partial dentures using LAVA CAD/CAM system (3M ESPE, Germany) were applied. Two silicone replicas were obtained: one is obtained before porcelain firing process (initial) and the other is obtained after porcelain firing process (final), followed by the examination under a binocular stereomicroscope. Kruskal Wallis and Wilcoxon Signed Ranks tests were used for the statistical analysis (P<.05).

RESULTS

No statistically significant difference was found between initial and final marginal gap values (P>.05). At the internal gap measurements, final marginal area values (59.54 µm) were significantly lower than the initial marginal area values (68.68 µm)(P<.05). The highest and the lowest internal gap values were observed at the incisal/occlusal area and at the marginal area, respectively. In addition, lower internal gap values were obtained for canines than for central incisors, lateral incisors and premolars at the incisal area (P<.05).

CONCLUSION

The firing cycles did not affect the marginal gap of Lava CAD/CAM system, but it is controversial for the internal gap.     

超薄瓷贴面的临床应用进展

超薄瓷贴面的临床应用具体是指在没有或者极少量的牙齿预备基础上仅通过0.3~0.5 mm厚的瓷贴面来改善牙齿的美学效果,已成为前牙美学修复的主流,因其对牙齿的损伤极小而备受患者青睐,临床医生也越来越关注超薄瓷贴面的修复过程及远期疗效。该文将从发展过程、适应证、牙体预备以及瓷材料与粘接剂的选择方面对超薄瓷贴面的临床应用现状进行详细论述。     

Indirect porcelain veneer technique for restoring intrinsically stained teeth.

Indirect porcelain veneers are often the ideal restoration for intrinsically stained teeth. This article details a step-by-step procedure for esthetically restoring discolored teeth. Porcelain laminate veneers are often indicated when teeth bleaching or direct composite bonding procedures cannot provide the desired esthetic result. Veneers are more appealing to many patients than full coverage crowns because of the more conservative tooth preparation required. If technique details are followed meticulously and cases are appropriately selected, porcelain veneers are not only durable but also promote marvelous gingival health and may be the most esthetic anterior dental restoration.     

Influence of tempering method on residual stress in dental porcelain.

The porcelain component of a porcelain-fused-to-metal restoration is strengthened by residual (tempering) stresses which are induced by cooling procedures followed in dental laboratories. The thermophysical properties of materials and cooling rate are the main factors which determine the residual stress. In this paper, the temperatures in the midplane of body-porcelain disks were measured from a heat-soak temperature (1000 degrees C) to room temperature during two different cooling procedures: slow cooling in air and forced-air cooling. Experimental results approximated exponential cooling wherein the cooling rates could be represented by a linear equation of temperature. Residual stresses, as affected by the tempering method and thickness of a porcelain disk, were calculated by computer simulation for regions away from the edges. The following temperature-dependent factors were incorporated into the simulation: elastic modulus, viscosity, and coefficient of thermal expansion. The cooling rate dependencies of the glass transition temperature and the temperature distribution during cooling were also included. The cooling rates used in this simulation were derived from the tempering data. The agreement between development of transient and residual stresses--calculated by computer simulation for various cooling methods, and the tendency toward failures of porcelain disks subjected to the tempering processes--was examined. Simulated residual stresses were also in good agreement with those measured by the indentation fracture method of Marshall and Lawn (1977) and Anusavice et al. (1989).     

Thermal stress failure of porcelain bonded to a palladium-silver alloy

Cracking or rupturing, due to thermal stress, of porcelain bonded to a palladium-silver alloy indicated that porcelain-metal thermal compatibility was dependent on: the difference in thermal expansion coefficients of the porcelain and metal; the geometry and dimensions of the samples; and the porcelain-metal thickness ratio. A spherical configuration was more sensitive to thermal expansion coefficient differences than was a disc configuration. A higher incidence of cracking resulted from an increase in both specimen size and porcelain-metal thickness ratio.