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Dental Alloys (dental + alloy)
Selected AbstractsPrediction of the Elastic Properties of Polycrystalline Microcomponents by Numerical HomogenizationADVANCED ENGINEERING MATERIALS, Issue 3 2009Katja Jöchen Polycrystalline microcomponents made of Stabilor®G, a dental alloy mainly consisting of gold, are examined in terms of their elastic properties. Finite element calculations of uniaxial tensile tests are carried out with ABAQUS so as to identify the characteristic parameters of the distribution of Young's modulus. It is shown that the statistics of mechanical properties observed experimentally can be estimated by using the finite element method. The findings are generalized to microcomponents consisting of crystals with a cubic symmetry. [source] Immunohistochemical study of oral lichen planus associated with hepatitis C virus infection, oral lichenoid contact sensitivity reaction and idiopathic oral lichen planusORAL DISEASES, Issue 5 2001H Mega OBJECTIVES:,Oral lichen planus (OLP) is a common mucocutaneous disorder and might be associated to a possible pathogenic relationship with hepatitis C virus (HCV) infection or hypersensitivity to dental alloy. We examined the clinical and immunohistochemical features of OLP associated with HCV infection (OLP-HCV), oral lichenoid contact sensitivity reaction (OLCSR), and idiopathic oral lichen planus (iOLP). The immunohistochemical expressions of CD4, CD8, B cells, Class II major histocompatibility complex antigen (HLA-DR), S-100, HSP60, Proliferating cell nuclear antigen (PCNA) and Ki-67 were compared to study the pathogenic differences of the three OLP groups. MATERIALS AND METHODS:,Three groups of OLP patients, (1) OLP-HCV patients (n=17), (2) OLCSR patients (n=10) and (3) iOLP patients (n=14) were retrieved from clinical records and tissues examined immunohistochemically by the avidin,biotin-complex technique. RESULTS:,The patients with OLP-HCV showed widespread lesions. The proportion of CD8+ cells was found to be significantly higher in the lamina propria of the OLP-HCV patients and a significantly lower proportion of CD8+ cells of the OLCSR patients was noticed in the epithelium or the connective tissue papillae than in the iOLP patients. There were no significant differences in either the number of CD4+ cells or B cells between the three OLP groups. No significant differences in the number of HLA-DR+ cells were found between the three OLP groups and some OLP-HCV patients showed a significant increase of S-100+ cells in the epithelium compared with iOLP patients. There were no significant differences in either the number of PCNA+ or Ki-67+ cells between the groups. The patients showed similar weak expressions of HSP60 in the three OLP groups. CONCLUSION:,The different distributions of the CD8+ cells that could have functionally different roles might be related to the distinct pathogenic mechanisms in the three OLP groups. [source] In vitro evaluation of the effect of a current bleaching agent on the electrochemical corrosion of dental alloysJOURNAL OF ORAL REHABILITATION, Issue 10 2002enay Canay summary, The nightguard bleaching of discoloured teeth is currently performed by using % 10 carbamide peroxide. While the material is effective on the bleaching of natural teeth, it may deteriorate crowns, bridges and amalgam restorations placed in the mouth. The purpose of the present study was to investigate the effect of 10% carbamide peroxide on the electrochemical corrosion of various dental casting alloys used for fixed partial dentures and dental amalgam. Tafel extrapolation curves were obtained by the corrosion cell that facilitated simulation of the oral enviroment and comparison of the corrosion rates of alloys and amalgam was accomplished. The results revealed that unpolished amalgam and nickel-chromium alloy samples had the most and noble alloys had the least corrosion rate. [source] Galvanic corrosion of selected dental alloysJOURNAL OF ORAL REHABILITATION, Issue 3 2001J. Karov Samples prepared from three different amalgam brands were coupled to two gold alloys and orthodontic brackets. In the resulting galvanic cells, the amalgam coupled to gold were anodic, exhibiting galvanic current densities about one order of magnitude higher than the uncoupled corrosion current densities of 0·2,0·5 ,A. Coupling amalgams to orthodontic brackets resulted in galvanic current densities of the same magnitude as the uncoupled samples. Corrosion current densities at the anode were found to be up to six times higher than the measured galvanic current densities. Brushing caused transient increases in galvanic current densities that decayed within 100 s to the previous steady state levels. Brushing of amalgam/bracket couples, caused an anodic peak followed by brief polarization reversal during which the brackets were anodic. [source] The effect of pH on the corrosion of dental metal alloysJOURNAL OF ORAL REHABILITATION, Issue 7 2000G. Bayramo The aim of this study was to determine the effects of the oral environment's pH on the corrosion of dental metals and alloys that have different compositions, using electrochemical methods. The corrosion rates and the cathodic Tafel slopes were obtained from the current,potential curves. The effect of pH on the corrosion of dental metals and alloys was dependent on their composition. Dissolution of the ions occurred in all of the tested pH states. The dissolution was moderately low for samples containing titanium because its surface was covered with a protective layer, whereas the dissolution was maximal for the samples containing tin and copper. Addition of cobalt and molybdenum to the alloys improved their corrosion resistance; these cobalt and molybdenum alloys were not effected by changes in the pH. Dissolution of the precious metal alloys increased as the percentage of noble metals increased. The corrosion characteristics of dental metals and alloys are important because the corrosion tendencies of dental alloys in the mouth may cause health hazards, weakening and the aesthetic loss of dental restorations. [source] | ||||||||||