Bond strength of porcelain to dental alloys – an evaluation of two test methods

Abstract – Two methods for measuring shear strengh of the porcelain-metal interface, a rod/disk-push test and a cube/cube-push test, were compared using the same metals and porcelain material. Both types of specimen showed evidence of complex stress distribution at the interface during loading and fracture line located mainly in the opaque porcelain layer. Both methods were thusmainly a test of the "strength" of the porcelain at the interface. The "Bond strength values" obtained with the rod/disk specimen seemed to depend on the geometry of specimen and the values obtained with the cube/cube specimen scemed to depend on the quality of the porcelain work. It seem questionable whether "bone strenghth values" as obtained with these two methods can be the basis for requirenments in a standard for porcelain-metal systems.     

Effect of electrodeposition of gold on porcelain-to-metal bond strength

The effect of electrodeposition of two different thicknesses of gold on porcelain-metal bond strength with three different base metal alloys was determined and compared to a control high gold alloy. The following conclusions can be drawn. Mean porcelain-metal bond strengths of all four alloys were in the same range when conventional porcelain application techniques were used. However, the base metal porcelain-metal bond is clinically suspect because of adhesive failure through the porcelain-metal interface. A thin 180A gold coat increased the porcelain-metal bond strength and generally resulted in cohesive failure through the porcelain. A thicker gold coat (720A) decreased the bond strength and generally resulted in adhesive failure. The mechanism of action of the gold coat on bond strength is likely its effect on the oxide layer on the surface of the base metal alloy.     

The effect of surface treatments on the bond strength of a nonprecious alloy-ceramic interface

PURPOSE: The purpose of this study was to compare the effect of seven different alloy surface treatments on the bond strength of the porcelain-metal interface. MATERIALS AND METHODS: Three layers of opaque porcelain and a measured thickness of dentin porcelain were applied to nickel-chromium alloy. A tensile bond strength test was used. RESULTS: The alloy surface treatment that exhibited the highest bond strength was sandblast + surface grinding + sandblast + de-gas, whereas the alloy surface treatment that exhibited the lowest bond strength was sandblast + surface grinding + sandblast + steam cleaning + de-gas. There was a significant difference between the two methods (P < 0.05). CONCLUSION: It was concluded that de-gassing the alloy prior to porcelain application increased the bond strength and excess surface grinding of the alloy reduced bond strength; steam cleaning the alloy surface prior to de-gassing and porcelain application also significantly reduced the bond strength.     

The relationship between oxide adherence and porcelain-metal bonding

The lack of a reliable bond test has hindered the elucidation of the mechanism for porcelain-metal bonding in dental systems, because a test capable of detecting differences among porcelain-metal bonds of various qualities is required before the reasons for these differences may be ascertained. A method was developed in the present study whereby specimens of alloys with differing physical properties may be deformed to a constant strain to yield a fracture surface suitable for measurement of the area fraction of retained porcelain by an x-ray spectrometric technique described previously. The method proved sufficiently discriminating that significant differences could be found in 48 of the possible 66 comparisons among alloys and treatments. Linear regression analysis revealed a strong correlation (r2 = 0.947) between the area fractions of retained porcelain measured in the present study and the oxide adherence strength values measured previously. This strong correlation, when considered in light of the literature evidence for the presence of an oxide layer at the porcelain-metal interface, provides compelling support for the oxide layer theory of porcelain-metal bonding in dental alloy systems.     

The Effect of Surface Treatments on the Bond Strength of a Nonprecious Alloy–Ceramic Interface: An Invitro Study

The purpose of this study was to compare the effect of seven different alloy surface treatments on the bond strength of the porcelain-metal interface. Three layers of opaque porcelain and a measured thickness of dentin porcelain were applied to nickel–chromium alloy, A tensile bond strength test was used. The alloy surface treatment that exhibited the highest bond strength was sandblast + surface grinding + sandblast + de-gas, whereas the alloy surface treatment that exhibited the lowest bond strength was sandblast + surface grinding + sandblast + steam cleaning + de-gas. There was a significant difference between the two methods (P < 0.05). It was concluded that de-gassing the alloy prior to porcelain application increased the bond strength and excess surface grinding of the alloy reduced bond strength; steam cleaning the alloy surface prior to de-gassing and porcelain application also significantly reduced the bond strength.     

A qualitative study for the bond and color of ceramometals. Part I

A shear testing method was devised to study and evaluate the effect of various and repeated firing cycles, types of alloy, and brand of porcelain relative to the color and bond strength of ceramometal complexes specifically at the opaque porcelain-metal interface and the opaque-body porcelain juncture. Two alloys and two porcelain brands were chosen on the basis of their widespread clinical use and the marked contrast between them. An increase of the firing temperature significantly raised the bond strength for all alloy-porcelain combinations.     

Measurement of oxide adherence to PFM alloys

A method has been reported for evaluating adherence of an oxide to its substrate metal to a maximum value of about 40 MPa. Oxidized alloy plates were cemented between two aluminum cylinders with a high-strength cyanoacrylate cement and loaded in tension until failure occurred either at the oxide/metal interface, within the oxide layer, or in the cement itself. Significant differences were found among the oxide adherence values obtained from different PFM alloys. The oxides formed on five of the alloys exhibited adherence strengths in excess of the published value for cohesive strength of dental opaque porcelain, indicating that they possess sufficient adherence to act as the transition zone between the porcelain and the alloy. In addition, a correspondence was found between the quality of porcelain bond for a given alloy and its oxide adherence strength. These results remove the principal objection to the oxide-layer theory of porcelain bonding in dental alloy systems and emphasize the importance of oxide adherence in the establishment of a bond. It is therefore suggested that future work devoted to porcelain-metal bonding should seek to elucidate the mechanism of oxide adherence to PFM alloys and explore the development of new alloys which form adherent oxides.     

The effect of cooling rate on the apparent bond strength of porcelain-metal couples

The effects of cooling conditions on the apparent bond strength of a dental porcelain fused to a case substructure were studied. Under the conditions of this investigation slow cooling of the porcelain-metal composite in an oven or rapid cooling in an ice chest from the maturation temperature of the porcelain resulted in the highest values of apparent bond strength. However, additional factors must be considered in the selection of a particular cooling method. From the present data it appears that the most practical procedure for cooling a ceramometal restoration is under a protective cover since it provides the least risk to the integrity of the porcelain-alloy bond and the surface of the porcelain.     

Effect of four pretreatment techniques on porcelain-to-metal bond strength

Porcelain bond strengths of three base metal alloys with different metal pretreatment techniques were studied. Statistically significant differences were found in bond strengths achieved between the different metals but not with the different pretreatments. Each metal displayed considerable variation in bond strength with each of the pretreatment techniques. Collectively, the base metal alloys evaluated displayed a disturbing tendency for adhesive failure through the porcelain-metal interface, although this was not universal. Manufacturers and ceramists should develop a specific regime for porcelain bonding for each alloy used. Standardized testing should demonstrate adequate bond strengths with cohesive failure through the body of the porcelains.     

Effect of multiple firing on the bond strength of selected matched porcelain-fused-to-metal combinations

In this study two different opaque porcelain-metal combinations were evaluated for planar shear bond strength. Samples were tested after one, three, five, seven, and nine different firing cycles to evaluate the effect of repeated firing on shear bond strength. For the combination of Will Ceram/W1 and Vita/Olympia materials, no statistical difference was observed either between materials or after repeated firing. For apparently well-matched porcelain-metal combinations, no significant reduction in bond strength occurs during normal firing of the opaque porcelain to the metal.     

Evaluation of low-fusing ceramic systems combined with titanium grades II and V by bending test and scanning electron microscopy

The bond strength by three point bending strength of two metal substrates (commercially pure titanium or grade II, and Ti-6Al-4V alloy or grade V) combined to three distinct low-fusing ceramic systems (LFC) and the nature of porcelain-metal fracture by scanning electron microscopy (SEM) were evaluated. The results were compared to a combination of palladium-silver (Pd-Ag) alloy and conventional porcelain (Duceram VMK68). Sixty metal strips measuring 25x3x0.5mm were made - 30 of titanium grade II and 30 of titanium grade V, with application of the following types of porcelain: Vita Titankeramik, Triceram or Duceratin (10 specimens for each porcelain). The porcelains were bonded to the strips with dimensions limited to 8x3x1mm. The control group consisted of ten specimens Pd-Ag alloy/Duceram VMK68 porcelain. Statistical analyses were made by one-way analysis of variance (ANOVA) and Tukey test at 5% significance level. Results showed that the bond strength in control group (48.0MPa ± 4.0) was significantly higher than the Ti grade II (26.7MPa ± 4.1) and Ti grade V (25.2MPa ± 2.2) combinations. When Duceratin porcelain was applied in both substrates, Ti grade II and Ti grade V, the results were significantly lower than in Ti grade II/Vitatitankeramik. SEM analysis indicated a predominance of adhesive fractures for the groups Ti grade II and Ti grade V, and cohesive fracture for control group Pd-Ag/Duceram. Control group showed the best bond strength compared to the groups that employed LFC. Among LFC, the worst results were obtained when Duceratin porcelain was used in both substrates. SEM confirmed the results of three point bending strength.     

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.     

A simple 3-point flexural method for measuring fracture toughness of the dental porcelain to zirconia bond and other brittle bimaterial interfaces

PurposePorcelain fused to zirconia prostheses are widely used, but porcelain chipping, fracture, spalling and delamination are common clinical problems. Conventional bond strength testing is inherently unsuited for studying interfacial failure by cracking in brittle materials. Instead, fracture toughness is a more meaningful parameter because it can assess the robustness of the interface when subjected to loading, but fracture mechanics approaches have only rarely been used. Our purpose was to develop a novel, simple, 3-point flexural methodology and mathematical analysis to measure the fracture toughness of the porcelain to zirconia interface.MethodsEquations were derived to estimate the fracture toughness of the bond by computing the interfacial energy release rate for a novel simple 3-point flexural test model. The test was validated using two different configurations of layered zirconia/porcelain beams (n = 10), approximating the dimensions of a fixed dental prosthesis, fabricated from a tetragonal polycrystalline zirconium dioxide partially stabilized with yttria and a feldspathic dental porcelain.ResultsCracking along the bimaterial interface was produced and measured as a discrete event. Fracture toughness means (standard deviations) computed from the measured energy release rate, for the porcelain to zirconia interface in two different specimen configurations were 7.9 (1.3) and 5.3 (1.6) J/m².ConclusionsEquations were derived to measure interfacial fracture toughness of brittle materials using a novel simple 3-point flexural test method. The test was then validated; estimates for the fracture toughness for the porcelain to zirconia bond, overlapped with previously published data derived from more complex 4-point notched tests.     

Shear strength of the composite bond to etched porcelain

The shear bond strength of composite resin to porcelain was investigated to optimize variables for bonding porcelain laminate veneers. Scanning electron microscopy was initially used to examine the surface configuration of porcelain prepared under various conditions. A factorial experiment was undertaken to determine the effects of three different bonding methods on both etched and non-etched porcelain. Composite resin was bonded to the porcelain groups using (a) unfilled resin, (b) silane, and (c) silane with dentin adhesive. The results indicated a significant difference in shear bond strength for the three bonding groups, depending on the porcelain surface condition. For the unetched samples, significant differences in bond strength were obtained for all three bonding conditions. However, for the etched group, there were no differences between the silane and silane-with-dentin-adhesive groups. Porcelain etching significantly increased bond strength across all three bonding methods and was the main contributor to the obtained values.     

Bond strengths of a porcelain material to different abutment substrates

The study evaluated the bond strength values of a single-unit all-porcelain material luted with an adhesive-resin cement to different abutment substrates: amalgam, compomer, traditional glass ionomer cement, microhybrid resin composite, two resin composites for abutment build-up, gold, sandblasted gold, dentin and enamel. Syntac enamel-dentin bonding system, in combination with IPS-Empress porcelain material, was used. After thermal cycling, the samples were inserted into a Bencor jig device and sheared in a Controls testing machine. The statistical analysis of the differences between the bond strength values obtained was performed by ANOVA and the Student-Newman-Keuls multiple-comparison test. The type of failure at the interface was evaluated using scanning electron microscopy. The type of failure, such as adhesive, cohesive and adhesive-cohesive, was correlated with bond strength values. Enamel, dentin and the two resin composites for crown build-up showed the highest bond strength values, while amalgam and gold samples showed the lowest.     

不同厚度内冠对钴铬合金烤瓷髓腔固位冠金瓷结合强度的影响

目的：研究内冠厚度对钴铬合金烤瓷髓腔固位冠金瓷结合强度的影响。 方法：选取32 颗离体磨牙,随机分为4 组,分别铸造0.3mm、0.5mm、0.8mm、 1.0mm 厚度内冠的钴铬合金烤瓷髓腔固位冠,采用万能检测机测试烤瓷冠的金瓷 结合强度,扫描电镜和能谱仪分析金瓷结合界面。结果：0.3mm、0.5mm、0.8mm、 1.0mm 厚度内冠的剪切力强度值分别为11.34±1.70MPa、11.55±1.62MPa、13.42 ±1.41MPa 和15.21±2.85MPa,不同厚度内冠之间的剪切力强度有统计学差异 (P<0.05)。结论：钴铬合金烤瓷髓腔固位冠不同厚度内冠的金瓷结合强度均能满 足临床要求,临床上可根据具体情况灵活选用。但如果从修复间隙的角度考虑, 在咬合间距过紧、严重磨耗等牙体修复时,可考虑使用较薄的内冠厚度。     

不同表面处理方法对氧化锆基底材料与饰面瓷结合强度的影响

目的 比较不同表面处理方法对氧化锆基底与饰面瓷之间的结合强度及结合界面微观结构的影响。方法 将WIELAND氧化锆瓷块胚体烧结制成10 mm×5 mm×5 mm大小试件33个。将试件随机分为3组,每组11个。喷砂组在烧结前进行喷砂处理;处理剂组先喷砂处理,再烧结结合衬底瓷;对照组不做处理。3组基底瓷材料采用粉浆涂塑法烧结5 mm×5 mm×5 mm大小的饰面瓷。每组随机抽取1个基底瓷及双层瓷试件,采用扫描电镜、能谱分析方法,研究氧化锆底瓷与饰面瓷之间的结合情况。其余试件则通过电子拉伸机测试结合界面的剪切强度,并用SPSS 17.0软件对实验数据进行统计学分析。结果 喷砂组、处理剂组、对照组试件的剪切强度分别为（18.06±0.59）、（21.04±1.23）、（13.80±1.54） MPa,各组间差异均有统计学意义（P<0.01）。结论 氧化锆胚体烧结前喷砂处理能提高氧化锆基底冠与饰面瓷的结合强度,结合衬底瓷的应用能提高氧化锆基底冠与饰面瓷的结合强度。     

Investigations of Pd-Ag alloy for porcelain fusing. (Part 1) Bond strength (author's transl)]

For the purpose of developing the Pd-Ag alloys for porcelain fusing, indium and/or tin were added to Pd-Ag alloys (70, 60 and 50 wt% Pd) and nine kinds of testing alloys for porcelain fusing were prepared. The bond strength with Ceramco porcelain was measured. The test-pieces for bond strength measured were prepared by press or condensing method. The bond strength was measured by "pull-out method" developed by Iwama. The maximum bond strength (230 kgf/cm2) was obtained 54 wt% Pd-36 wt% Ag-5 wt% In-5 wt% Sn alloy.     

A comparative study of the strength of aluminous porcelain jacket crowns constructed with the conventional and twin foil technique

The purpose of this study was to evaluate and compare the strength of aluminous porcelain jacket crowns made in the following manners: (1) the conventional technique, (2) the conventional technique with a pure alumina insert, (3) the twin foil technique, and (4) the twin foil technique with a pure alumina insert. The conclusions of this investigation can be summarized as follows: 1. Porosity was observed in all the restorations made by each of the techniques. 2. The porosity was greater at the porcelain-platinum foil interface than anywhere else throughout the restoration with both the conventional and twin foil techniques. 3. The porosity seemed to be evenly distributed along the interface, with no concentration in any area. 4. Regardless of the technique, crowns that were more porous fractured at lower values. 5. Crowns built by the twin foil technique were significantly more porous at the interface of the tin-plated platinum and the porcelain core than those built by the conventional technique. 6. Crowns constructed with the conventional technique were significantly stronger than those constructed with the twin foil technique. 7. There was no bond between the core porcelain and the platinum foil matrix in crowns constructed by the conventional technique. 8. There seemed to be a strong bond between the core porcelain and the tin-plated platinum matrix in crowns built by the twin foil technique. 9. The presence or absence of the alumina insert on crowns constructed with the conventional and twin foil technique did not affect the strength of the crowns when tested at the incisal edge.     

Shear bond strength between metal alloy and a ceramic system, submitted to different thermocycling immersion times

The aim of this study was to evaluate the shear bond strength of Co-Cr and Ni-Cr metal alloys and a specific ceramic, submitted to different thermocycling immersion times. Sixty metal-ceramic specimens were confectioned and standardized in cylindricalformat. Three thermocycling conditions were evaluated: without thermocycling, 3,000 cycles (5 degrees C/55 degrees C+/-1) with 30s of immersion time and 3,000 cycles (5 degrees C/55 degrees C+/-1) with 60s. The shear bond strength was performed in a universal testing machine, using a special device to concentrate the tension at the metal/ceramic interface during the test. The load was applied until fracture of the specimens. The data was statistically analyzed by ANOVA (two-way) and Tukey (p<0.05) test. The results didn't show significant statistic differences between the metal-porcelain combinations. Nevertheless, both metal-ceramic systems submitted to 60s of immersion time showed lower values compared to specimens without thermocycling. It was concluded that the thermocycling immersion time of 1 minute affect the shear bond strength values for the Ni-Cr/porcelain and Cr-Co/porcelain systems.