Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique

PURPOSE: The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS: Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS: Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION: Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

Metal stain on monolithic zirconia restoration: A case report

In restorative treatment using fixed dental prostheses, dentists should select appropriate restoration material among various types of dental materials. The strength, marginal fit, esthetics, wear resistance, biocompatibility, and cost are important factors in the choice of restoration materials. The present case showed a surface stain on a monolithic zirconia restoration that was due to wear between the monolithic zirconia restoration and the base metal alloy restoration. This phenomenon was confirmed by surface roughness measurement and electron probe micro-analysis.

Evaluation of effect of galvanic corrosion between nickel-chromium metal and titanium on ion release and cell toxicity

PURPOSE: The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS: It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens (10 x 10 x 1.5 mm) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS: The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION: The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

Evaluation of effect of galvanic corrosion between nickel-chromium metal and titanium on ion release and cell toxicity

PURPOSE: The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS: It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens (10 x 10 x 1.5 mm) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS: The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION: The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

Corrosion of orthodontic brackets in different spices:In vitro study.

Context: Moist environment in the mouth varies and causes variable amounts of corrosion of dental materials. This is of concern particularly when metallic implants, metallic fillings, orthodontic appliances are placed in the hostile electrolytic environment in the human mouth. Components of diet rich in salt and spices are important factors influencing the corrosion of metallic appliances placed in the oral cavity. Aims: To study in vitro corrosion of orthodontic metallic brackets immersed in solutions of salt and spices in artificial saliva. Materials and Methods: Orthodontic brackets were used for corrosion studies in artificial saliva, salt, and spices using electrochemical technique and surface analysis. Electrochemical studies using different parameters were done in solutions of artificial saliva containing salt and spices. Photomicrographs from the optical microscope were also obtained. Results: Results of corrosion studies have clearly demonstrated that certain spices such as turmeric and coriander are effective in reducing corrosion, whereas salt and red chili have been found to enhance it. Surface analysis of small pits present on the surface of the as-received bracket will initiate corrosion which leads to more pitting.

Properties of experimental copper-aluminium-nickel alloys for dental post-and-core applications

PURPOSE: This study aimed to develop a copper-aluminium-nickel alloy which has properties comparable to that of dental alloys used for dental post and core applications with the reasonable cost. MATERIALS AND METHODS: Sixteen groups of experimental copper alloys with variants of 3, 6, 9, 12 wt% Al and 0, 2, 4, 6 wt% Ni were prepared and casted. Their properties were tested and evaluated. The data of thermal, physical, and mechanical properties were analyzed using the two-way ANOVA and Tukey's test (alpha=0.05). The alloy toxicity was evaluated according to the ISO standard. RESULTS: The solidus and liquidus points of experimental alloys ranged from 1023degrees C to 1113degrees C and increased as the nickel content increased. The highest ultimate tensile strength (595.9 +/- 14.2 MPa) was shown in the Cu-12Al-4Ni alloy. The tensile strength was increased as the both elements increased. Alloys with 3-6 wt% Al exhibited a small amount of 0.2% proof strength. Accordingly, the Cu-9Al-2Ni and Cu-9Al-4Ni alloys not only demonstrated an appropriate modulus of elasticity (113.9 +/- 8.0 and 122.8 +/- 11.3 GPa, respectively), but also had a value of 0.2% proof strength (190.8 +/- 4.8 and 198.2 +/- 3.4 MPa, respectively), which complied with the ISO standard requirement (>180 MPa). Alloys with the highest contents of nickel (6 wt% Ni) revealed a widespread decolourisation zone (5.0-5.9 mm), which correspondingly produced the largest cell response, equating positive control. CONCLUSION: The copper alloys fused with 9 wt% Al and 2-4 wt% Ni can be considered for a potential use as dental post and core applications.

Avaliação da microestrutura, microdureza e resistência à corrosão de juntas soldadas de uma liga de Ni-Cr obtidas através de diferentes processos de soldagem / Evaluation of the microstructure, hardness and corrosion resistance of welded joints of a Ni-Cr alloy obtained by different welding processes

Este trabalho avaliou o comportamento eletroquímico do metal de base (MB) de uma liga a base de níquel-cromo em relação a juntas soldadas desta liga obtidas pelos processos de brasagem (BRA) e Tungsten Inert Gas (TIG), imersos em saliva artificial com pH 2,5 e 5,5. Foram também realizados ensaios de microdureza e caracterização microestrutural, por meio de microscopia óptica e eletrônica de varredura e análise química semi-quantitativa por EDS, nos grupos MB, TIG, BRA e no cordão de solda a laser (LAS). O MB apresentou uma matriz rica em níquel e cromo, distribuída em um arranjo dendrítico típico, apresentando inclusões metálicas de silício e titânio, além de porosidades. As soldas TIG e LAS revelaram uma microestrutura mais refinada que o MB, mostrando, entretanto, uma mesma composição química e distribuição de seus elementos. A solda BRA apresentou diferenças marcantes em sua microestrutura, composição química e distribuição de seus elementos em relação ao MB. Os dados de microdureza Vickers (HV), potencial de corrosão (Ecorr) e densidade de corrente de corrosão (jcorr) foram analisados com ANOVA e teste de Tukey (p<0,05). Para determinação da influência do pH quanto a resistência à corrosão dos grupos MB, TIG e BRA, empregou-se o teste t de Student (p<0,05). O MB apresentou menor média de microdureza (256,13 ± 9,39 HV), seguido pelos grupos TIG (271,53 ± 8,07 HV), LAS (303,73 ± 13,93 HV) e BRA (551,99 ± 37,73 HV). Em pH 2,5 as médias do Ecorr (mV) para o MB, TIG e BRA foram, respectivamente, -67,9 ± 8,43, -52,78 ± 16,74, e -284,33 ± 19,04; e em pH 5,5, médias de -54,03 ± 21,15, -62,08 ± 20,16 e -278,8 ± 28,96. Os valores médios de jcorr (µA.cm-2) para o MB, TIG e BRA em pH 2,5 foram, respectivamente, 2,49 ± 0,95, 5,584 ± 1,64 e 27,45 ± 4,9; e em pH 5,5, médias de 1,929 ± 0,83, 4,267 ± 1,51 e 54,2 ± 11,96. Os grupos MB e TIG apresentaram boa resistência à corrosão, com maior módulo de impedância em relação ao grupo BRA. As diferenças no pH da ...

This study evaluated and compared the electrochemical behavior of the base metal (BM) of a nickel-chromium dental alloy with welded joints obtained by brazing processes (BRA) and Tungsten Inert Gas (TIG), when immersed in artificial saliva at pH 2.5 and 5.5. Microhardness, microstructural characterization by means of optical microscopy, scanning electron microscopy (SEM) and semi-quantitative chemical analysis by Energy Dispersive Spectroscopy (EDS), were performed in the groups BM, TIG, BRA and in joints weld by laser (LAS). The BM showed a matrix rich in nickel and chromium, distributed in a typical dendritic arrangement, with inclusions of silicon and titanium, and porosities. LAS and TIG welds reveled a microstructure more refined than the BM, however, the same chemical composition and distribution of its elements. BRA showed marked differences in their microstructure, chemical composition and distribution of the elements in relation to BM. Vickers microhardness (HV), corrosion potential (Ecorr) and corrosion current density (jcorr) were statistically analyzed with ANOVA and Tukey test (p <0.05). In order to determine the influence of pH and corrosion resistance in groups BM, TIG and BRA, Student t test, with significance level of 95% was used. BM had the lowest average microhardness (HV 256.13 ± 9.39), followed by groups TIG (271.53 ± 8.07 HV), LAS (303.73 ± 13.93 HV) and BRA (551, HV 99 ± 37.73). At pH 2.5 the average Ecorr (mV) for the MB and TIG were respectively -67.9 ± 8.43 and -52.78 ± 16.74, and at pH 5.5, averaging -54, 03 ± 21.15 and -62.08 ± 20.16. LAS group showed averages of Ecorr (mV) at pH 2.5 and 5.5, respectively, -284.33 ± 19.04 and 28.96 ± -278.8. The average values of jcorr (ìA.cm-2) to BM and TIG at pH 2.5 were respectively 2.49 ± 0.95 and 5.584 ± 1.64, and at pH 5.5, 1.929 ± 0.83 and 4.267 ± 1.51. Average jcorr for LAS group (ìA.cm-2) at pH 2.5 and 5.5 were respectively 27.45 ± 4.9 and 11.96 ± 54.2. BM and TIG ...

Corrosion behavior of titanium wires: An in vitro study.

Context: Teeth and restorations are subjected continuously to degradation in hostile physical and chemical environments, resulting in corrosion. Component of liquid or solid is an important factor influencing the corrosion of metallic appliances placed in the oral cavity. Aims: To study in vitro corrosion of titanium wires immersed in solutions of toothpaste and chocolate in artificial saliva. Materials and Methods: Immersion test and electrochemical studies using different parameters, including corrosion potential (E corr ), cathodic Tafel constant (βc), anodic Tafel constant (βa), corrosion current (I corr ), polarization resistance (R p ), and corrosion rate of titanium wires, were done in solutions of artificial saliva containing Colgate™ toothpaste and Amul™ chocolate. Photomicrographs were also taken. Results: The results showed degradation of titanium wires by electrochemical attack when they were placed in the hostile electrolytic environments provided in the experiments. Surface analysis of titanium wires showed pitting and localized attacks on the surface. Pitting corrosion was found in the titanium wires.

Shear bond strength of porcelain veneer with fresh and recasting Ni-Cr alloy: a comparative in vitro study / Resistência de união ao cisalhamento entre porcelana de recobrimento e liga de Ni-Cr nova e refundida: estudo in vitro comparativo

Introduction: Dental alloys are routinely subjected to multiple casting procedures. Repeated casting of the same alloys may cause loss of trace elements (such as Sn, Si, Mn, etc.) that are essential for the metal ceramic bond. A common practice is to include a proportion of new metal with the previously cast metal that is thought to replenish the lost elements. Objective: The study was done to evaluate the effect of variation in percentage of recasted Ni-Cr alloy used and to compare the effects with the shear bond strength of porcelain to the fresh ingot Ni-Cr alloy. Materials and methods: Uniform patterns were fabricated, invested and casting was done in five different combinations of fresh and recast alloy. A hundred percent fresh alloy; 25% recast with 75% fresh alloy; 50% recast and 50% fresh alloy; 75% recast and 25% fresh alloy; 100% recast alloys. After uniform porcelain application and firing, the specimens were subjected to shear bond test using a universal testing machine. Data were statistically analyzed using Duncans’s multiple comparison test. Results: The results showed that the mean shear bond strength of the 100% fresh alloy was maximum and 100% recast alloy was least among the groups tested. The mean shear bond strength of castings obtained from 100% fresh, 25% recast, and 50% recast alloy were similar to each other and showed statistically significant difference when compared to the 100% recast group. Seventy five percent recast group did not show statistically significant difference with 100% recast alloy. Arch Oral Res. 2011 May/Aug.;7(2)177-82 Rajalbandi SK, Kumar V, Sajjan S. 178 Introduction The Development of “Taggarts” technique of casting by lost wax process into the Dentistry gave an impetus to use alloyed metals as a restoration (1). Most of the dental laboratories commonly use the sprue and button from a previous casting as a part of the melt for the new casting (2, 3). This practice is especially detrimental with ceramometal...

Introdução: Ligas dentárias são rotineiramente submetidas a procedimentos de fundição múltipla. Fundiçõesrepetidas da mesma liga podem causar perda de elementos-traço, tais como Sn, Si e Mn, os quais são essenciaispara a união entre metal e cerâmica. Uma prática comum é a de incluir uma proporção de liga nova com ometal anteriormente fundido visando repor esses elementos perdidos. Objetivo: O presente estudo avaliou oefeito da variação da porcentagem de liga de Ni-Cr refundida na resistência de união ao cisalhamento comporcelana, comparado a liga de Ni-Cr nova. Materials e métodos: Padrões uniformes foram confeccionados,incluídos e fundidos sob cinco diferentes combinações de liga nova e refundida: 100% liga nova; 25% ligarefundida + 75% liga nova; 50% liga refundida + 50% liga nova; 75% liga refundida + 25% liga nova; 100%liga refundida. Após a aplicação uniforme da porcelana e sua posterior cocção, as amostras foram submetidasao teste de cisalhamento utilizando uma máquina universal de ensaios. Os dados foram analisados estatisticamenteatravés do teste de comparações múltiplas de Duncan. Resultados: Os resultados mostraram que amaior resistência de união ao cisalhamento para a liga 100% nova, e a menor resistência para a liga 100%refundida. A resistência de união ao cisalhamento das fundições com 100% de liga nova, 25% e 50% de ligarefundida foi similar e estatisticamente diferente do grupo com 100% de liga refundida. O grupo com 75%de liga refundida não mostrou diferença estatisticamente significante com o grupo de liga 100% refundida.Conclusão: Pode-se concluir que o mínimo de 50% de liga nova para a fundição é uma margem de segurançapara a refundição de ligas de Ni-Cr.

Microstructural characterization of Ni-Cr-Mo-Ti and Ti-6Al-4V alloys used in prosthetic abutments / Caracterização microestrutural das ligas Ni-Cr-Mo-Ti e Ti-6Al-4V utilizadas para pilares de próteses

Purpose: Titanium alloys are commonly used for prosthetic abutments fabrication, but these alloys present high cost and difficult handling. Alternative Ni-Cr alloys with Mo and Ti combination have been proposed. This study compared the alloys Ti-6Al-4V and Ni-Cr-Ti-Mo by analyzing their surface properties such as hardness, morphology and microstructural characterization. Methods: Five discs (5 x 2 mm) of commercially Ti-6Al-4V and Ni-Cr-Ti-Mo alloys were used to evaluate Vickers hardness by hardness micro indentation test. The same specimens were analyzed by scanning electron microscopy (SEM) regarding surface morphology and subjected to a metallographic analysis of the microstructure by optical microscopy. Data on surface hardness were analyzed using one-way ANOVA followed by Tukey test (α = 0.05). Results: The Ni-Cr-Mo-Ti alloy showed significantly higher Vickers hardness (kg/mm2) values (452.2 ± 3.9) than the Ti-6Al-4V alloy (375.7 ± 15.2). The surface morphology evaluated by SEM revealed differences between the alloys. Metallographic analyses, for both alloys, showed a two-phase equilibrium microstructure, with the presence of e α + ß phase for Ti-6Al-4V; and gamma (γ) primary phase and gamma-prime (γ´) as a second phase for Ni-Cr-Mo-Ti. Conclusion: It can be concluded that both alloys present the requirements to be used in prosthetic abutments.

Objetivo: As ligas de titânio são comumente usadas para a fabricação de componentes protéticos, entretanto apresentam alto custo e dificuldade de manuseio laboratorial. Ligas alternativas a base de Ni-Cr combinadas com Mo e Ti também tem sido propostas com o mesmo objeto. Este estudo comparou as ligas Ti-6Al-4V e Ni-Cr-Ti-Mo pela análise de suas propriedades de superfície como dureza, morfologia e caracterização da microestrutura.Metodologia: Cinco discos (5 × 2 mm) das ligas Ti-6Al-4V e Ni-Cr-Ti-Mo foram utilizados para a avaliação da dureza Vickers, análise de morfologia de superfície por meio da microscopia eletrônica de varredura (MEV) e análise da microestrutura pela análise metalográfica. Os dados da dureza de superfície foram analisados pela Análise de Variância a um nível seguida do teste de Tukey (α = 0,05). Resultados: A liga Ni-Cr-Mo-Ti apresentou os maiores valores de dureza Vickers (kg/mm2) (452,2 ± 3,9) comparada a liga Ti-6Al-4V (375,7 ± 15,2) A morfologia de superfície avaliada por MEV revelou características distintas entre as ligas. A análise metalográfica para ambas as ligas mostrou uma microestrutura com equilíbrio de duas fases, com a presença de fase α + ß para Ti-6Al-4V; e fase gamma primária (γ) e fase gamma-prime (γ') como secundária para Ni-Cr-Mo-Ti. Conclusão: Ambas as ligas podem ser utilizadas para fabricação de pilares protéticos.

Evaluation of mechanical properties of two low noble alloys / 实用口腔医学杂志

?Objective: To evaluate the mechanical properties of low noble alloy Au Pd and Ag Pd developed by Stomatological College,Fourth Millitaly Medical University and Xi'an University of Architecture & Techuology. Methods:The two low noble alloys were cast by means of a centrifugal induction furnace into the tensile bars whose dimensions accorded with the standards of China for Dental Casting Precious Metal Alloys. Tensile properties (?b)were determined by means of a conventional testing machine. The 0.2% offset yield strength(?0.2), elongation(?) and microhardness (HV)were determined in a conventional manner. All data were the average of four specimens of each alloy. Results:?b(MPa),?0.2(MPa),?(%) and HV of Au Pd were 485?12.9,365 ?14.8,7.8?1.1 and 220?14.3;those of Ag Pd 550?9.5,435?8.2,13.5?5.4 and 245?15.1,respectivey.Conclusion:The mechanical properties of the two low noble alloys meet the demands of standards and have lower microhardness than natural tooth enamel.