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[Short-term observation of gold-plating unprecious metal ceramic crown in restoring anterior tooth].

PURPOSE: To evaluate the short-term effect of gold-plating technique used in Ni-Cr metal ceramic crown in restoring anterior teeth. METHODS: 64 teeth from 38 cases were divided into two groups. Each group consisted of 32 teeth. All the teeth were restored with Ni-Cr metal ceramic crown. The restorations in group 1 had no treatment while those in group 2 were treated with gold-plating technique in the base metal alloy.Gingiva discoloration, bleeding on probing (BOP), plaque index (PLI) and sulcular bleeding index (SBI) were examined 1 and 12 months after restoration. Chi-square test and Wilcoxon rank sum test were used for statistical analysis. RESULTS: Gingiva discoloration was found in both groups after bonding. According to the percentage of gingival discoloration, there was no significant difference between group 1 and group 2 (12.5% vs 28.1%) (P>0.05). However, 12 months later, significant difference was found between the two groups (15.6% vs 37.5%)(P<0.05). According to PLI, BOP and SBI, there was no statistical difference between two groups (P>0.05). CONCLUSION: Gold-plating was a good method in solving the problem of gingival discoloration in unprecious metal ceramic crown.

Chromium Alloys↗

Leaching of metals on stabilization of metal sludge using cement based materials.

Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371.5 mg/L, 1.95 mg/L and 1.99 mg/L respectively. Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.

Aluminum Silicates↗

Removal of nickel ions from industrial plating effluents using activated alumina as adsorbent.

Removal of nickel ions from industrial effluents has been studied using activated alumina prepared by the galvanic oxidation of aluminum metal at ambient temperature as the adsorbent. The effect of various factors, such as initial concentration of nickel, contact time, dose of adsorbent and pH of the solution has been investigated. Batch and column type of adsorption studies have been made. The results indicate that the adsorption process is favored at pH 9. The adsorption data were fitted with suitable adsorption isotherm. The optimum conditions for the best adsorption have been evaluated for the following factors: dosage, contact time, pH, initial concentration of nickel ions and temperature. The process of regeneration of the adsorbent has also been studied.

Adsorption↗

Properties of hydroxyapatite-coated Ti-6Al-4V alloy produced by the ion-plating method.

To improvement the brittleness of hydroxyapatite (HAp) coated on titanium alloy (Ti-6Al-4V), a thin ceramic layer was formed by means of the RF ion-plating method. The alloy substrates were coated with HAp at 1, 3 or 5 microns thickness and heat-treated at 500 degrees C for 4 hours. Properties of HAp-coated alloy were evaluated by characterization of the ceramic films both before and after heat-treatment, as well as by bending, electrochemical and dissolution tests. HAp-coated film had a slightly higher Ca/P ratio than the original material and was stoichiometrically Ca10(PO4)6(OH)2 by EPMA analysis. HAp was mainly recognized crystallographically by XRD analysis of the films after heat treatment, though it was hardly recognized on before heat-treatment film. These coated materials had a residual strain ranging from 0.3 to 0.7% without causing cracks in the HAp films with the three-point bend testing. Electrochemically, it was confirmed that the corrosion resistance of the Ti alloy was improved by any coating process. The amounts of Ca released from HAp coated film in 0.9% NaCl solution tended to increase with films that were 3 and 5 microns in thickness, but there were no significant differences in Ca released from film before and after heat treatment.

Aluminum Oxide↗

Dielectrophoresis of DNA: time- and frequency-dependent collections on microelectrodes.

This paper reports measurements that characterize the collection of DNA onto interdigitated microelectrodes by high-frequency dielectrophoresis. Measurements of time-dependent collection of 12 kilobase pair plasmid DNA onto microelectrodes by dielectrophoresis show significant reduction in the response as the frequency increases from 100 kHz to 20 MHz. Collection time profiles are quantitatively measured using fluorescence microscopy over the range 100 kHz to 5 MHz and are represented in terms of two parameters: the initial dielectrophoretic collection rate, and the initial to steady-state collection transition. Measured values for both parameters are consistent with trends in the frequency-dependent real part of the effective polarizability measured for the same plasmid DNA using dielectric spectroscopy. The experimentally measured parameters are qualitatively compared with trends predicted by theory that takes into account dielectrophoretic particle movement and diffusion. The differences between experiment and theory are discussed with suggested improvements to theoretical models, for example, including the effects of electrohydrodynamically driven fluid motion.

Coated Materials, Biocompatible↗

[Effects of voltage during anodization on titanium surface on cell attachment and spreading of osteoblasts].

PURPOSE: The effects of the voltage during anodic oxidation on cell attachment and spreading of human osteoblasts in early stage were investigated. METHODS: The samples were anodized in the electrolyte of 0.03 M calcium glycerophosphate (Ca-GP) mixed with 0.15 M calcium acetate (CA) under current density of 70 A/m2 and different voltages, 140V, 200V or 260V. The surface roughness of the specimens and the attachment and spreading of human osteoblasts in early stage were investigated. SPSS13.0 for windows was used for one-way ANOVA. RESULTS: The surface average roughness of cp Ti was significantly improved from 0.17 micro m to 0.23 micro m, 0.26 micro m, 0.33 micro m, respectively, by anodic oxidation with increased voltage (P<0.05). After 2 hours of cell culture, cell skeleton was reorganized and cell morphology became more irregular with the increase of anodizing voltages. Cell attachment on the specimens anodized under 260V was significantly higher than on the surface of cp Ti (P<0.05). CONCLUSION: The surface properties of cp Ti can be affected by anodic oxidation. The early cell attachment and spreading were enhanced with anodizing voltage.

Acetates↗

Galvanoforming for large-span fixed restorations in the treatment of periodontally compromised patients.

Large-span fixed restorations in the treatment of periodontally compromised patients are technically difficult to realize. Despite existing techniques of regenerative periodontal surgery and implant therapy aimed at preventing large spans by increasing the number of abutments, prosthetic complications do occur. The present article describes a method that introduces galvanic caps to conventional prosthetic technology, which facilitates clinical procedures and reduces complications by improving precision of fit.

Crowns↗

Adhesion monomers utilized for fixed partial denture (porcelain/metal) repair.

A technique is presented for repair of fatigue-fractured fixed partial dentures with an overlaid, bonded porcelain/metal repair. The repair techniques utilize recent advances in resin-to-metal and resin-to-porcelain adhesion. Clinical procedures are given for adhesion of repair castings to intraoral porcelain or metal surfaces. Metal surface preparation techniques depend on the chemistry of the metal and include intraoral tin plating of noble metals. Direct adhesion of composite resin luting agents is used for base metals.

Adhesives↗

Removal of "black-line" margins and improving esthetics of porcelain-fused-to-metal crowns: update in technique.

A repair technique is presented for elimination of "black line" crown margins and extension of margins onto cervical surfaces. A resin bonding agent that adheres simultaneously to metal, porcelain, and dentin is utilized to expedite completion of the repair. The bonding resin is opaqued with a light-curing, filled resin and then covered with a suitable composite resin. This technique updates a previously published technique by eliminating glass-ionomer cement liners and liner etching and improves both efficiency and esthetics of the repair.

Composite Resins↗

[Experimental study on bond strength of gold plated etched-metal surfaces of resin bonded restorations].

The purpose of this study was to compare the tensile bond strength of the resin-metal interface between etched only and etched & goldplated metal specimens. Etched only and etched & goldplated metal specimens were treated or were not treated with bonding agent and bonded to metal specimens with Comspan and MBAS. Also, electrochemically only etched metal surface and etched & goldplated metal surface was observed by SEM. The following results were obtained: 1. The tensile bond strength of the electrochemically etched only and gold-plated specimens were not significantly different in Comspan group, but the gold-plated specimens in MBAS group demonstrated slightly lower values than the etched only specimens. 2. The tensile bond strengths were not significantly different between the treated group with bonding agent and not-treated group with bonding agent. 3. The tensile bond strengths were not significantly different between the Comspan and MBAS groups. 4. The basic microretentive structures, maintained obviously in the etched and goldplated metal surfaces by SEM.

Acid Etching, Dental↗