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PubMed2006

Piezoelectric ultrathin lead titanate films prepared by deposition of aquo-diol solutions.

We report on the preparation of continuous ultrathin ferroelectric films of pure lead titanate by chemical solution deposition (CSD) methods. Aquo-diol solutions highly diluted have been used to obtain films with thickness down to approximately 13 nm, the lowest reported for CSD films. The formation of islands instead of continuous coatings, which has been reported when CSD is used to prepare ultrathin films, is avoided here. The piezoelectric activity of the films has been characterized by piezoresponse. force microscopy, showing that the thinnest film obtained retains a significant piezoelectric activity at the nanoscale, which is promising for their use as transducer elements in nanoelectromechanical systems (NEMS).

Crystallization↗
PubMed1992

Detection of selenium in generalized and localized argyria: report of four cases with X-ray microanalysis.

Electron microscopic and X-ray microanalytic studies were performed on four cases of argyria; one generalized and three localized. Deposition of electron dense granules was predominantly found on elastic fibers and around basal laminas of secretory portions of eccrine glands, although the amount of deposition was much less in the case of generalized argyria. In all four cases, X-ray microanalysis revealed that the depositions consisted mainly of silver, selenium, and sulfur. The importance of selenium in the detoxification of heavy metals was discussed.

Acupuncture Therapy↗
PubMed1996

Marginal fit of electroformed ceramometal crowns.

PURPOSE: A method of fabricating ceramometal crowns using gold copings produced by an electroforming process has been described, which purportedly results in restorations exhibiting an excellent marginal fit. This study compares the fit of electroformed ceramometal crowns with ceramometal crowns fabricated using conventional lost wax casting techniques. MATERIALS AND METHODS: Electroformed and conventional ceramometal crowns were fabricated for prepared extracted teeth. Specimens were cemented, embedded in acrylic resin, sectioned, polished, photographed, and measured to compare marginal fit. RESULTS: Marginal fit of electroformed ceramometal crowns was superior to the fit of ceramometal crowns fabricated using conventional casting techniques. The difference was statistically significant at a P = .05 level. CONCLUSIONS: Crowns utilizing copings fabricated by electroforming methods appear to have a fit superior to conventional ceramometal crowns fabricated using copings made by lost wax casting. The ease in laboratory electroforming techniques and the esthetic advantages of a gold-colored coping can be capitalized on without concerns of a poorer fit.

Crowns↗
PubMed1996

The bond strength of an adhesive resin luting cement to a variety of surface treatments of a high-palladium copper alloy.

PURPOSE: This study evaluated the tensile bond strength of a bisphenol glycidyl methacrylate (Bis-GMA) resin luting cement with four different surface treatments of a high Pd-Cu alloy. MATERIALS AND METHODS: For each surface treatment type (tin-plated, porcelain furnace oxide, air-abraded, and finished-only), 15 opposing half-dumbbell-shaped samples were cast and prepared in new Pd-Cu alloy. Samples were luted with a Bis-GMA resin luting cement at a film thickness of 80 microns using a custom alignment apparatus. Samples were stored in distilled water at 37 degrees C for 24 hours, thermocycled for 1,000 cycles, and then stored for 30 days in distilled water at 37 degrees C. Samples were then subjected to fracture in tension at a loading rate of 0.5 cm/min with the bond strengths calculated in megapascals (MPa). The fractured surfaces were examined using stereomicroscopy and scanning electron microscopy at various magnifications ranging from 5.5x to 500x to determine the type of bond failure (adhesive, cohesive, or mixed). RESULTS: Tensile bond strengths (mean +/- SD MPa) were: tin-plated, 30 +/- 15.7; porcelain furnace oxide, 23 +/-n 8.6; air-abraded, 8 +/- 8.1; and finished-only, 4 +/- 4.5. Statistical analysis of the tensile bond values using an ANCOVA and Tukey's multiple comparison test at a significance level of 0.05 indicated that there was no difference between the tin-plated and the furnace oxide groups, as well as between the air-abraded and the furnace oxide groups. However, there was significant difference between the tin-plated, the air-abraded, and the finished-only groups. The observed bond failures were predominantly mixed and cohesive in nature with only one adhesive failure. CONCLUSIONS: There was no significant difference in the tensile bond strengths between the tin-plated group or the porcelain furnace oxide surface group. This suggests that the less-technique-sensitive porcelain furnace oxide surface treatment offers an alternative for achieving high metal-resin bonds to a high Pd-Cu alloy.

Aluminum Oxide↗
PubMed2000

Tensile bond strength of resin-modified glass-ionomer cement to microabraded and silica-coated or tin-plated high noble ceramic alloy.

PURPOSE: The purpose of this study was to evaluate the influence of alloy surface microabrasion, silica coating, or microabrasion plus tin plating on the tensile bond strengths between a resin-modified glass-ionomer luting cement and a high-noble alloy. Bond strength between the microabraded alloy specimens and conventional glass-ionomer cement or resin cement were included for comparison. MATERIALS AND METHODS: One hundred twenty uniform size, disk-shaped specimens were cast in a noble metal alloy and divided into 6 groups (n = 10 pairs/group). The metal surfaces of the specimens in each group were treated and cemented as follows. Group 1: No surface treatment (as cast, control), cemented with a resin-modified glass-ionomer cement. Group 2: Microabrasion with 50-microm aluminum oxide particles, resin-modified glass-ionomer cement. Group 3: A laboratory microabrasion and silica coating system, resin-modified glass-ionomer cement. Group 4: Microabrasion and tin-plating, resin-modified glass-ionomer cement. Group 5: Microabrasion only, conventional glass-ionomer cement. Group 6: Microabrasion and tin-plating, conventional resin cement. The uniaxial tensile bond strength for each specimen pair was determined using an Instron Universal Testing Machine (Instron Corp, Canton, MA). Results were analyzed using a one-way analysis of variance (alpha = 0.05) and a Tukey post-hoc analysis. RESULTS: Mean bond strength: Group 1: 3.6 (+/- 1.5) MPa. Group 2: 4.2 (+/-0.5) MPa. Group 3: 6.7 (+/- 0.9) MPa. Group 4: 10.6 (+/- 1.8) MPa. Group 5: 1.1 (+/- 0.4) MPa. Group 6: 14.6 (+/- 2.3) MPa. Group 6 was significantly stronger than Group 4. The bond strength of specimens cemented with the resin-modified glass-ionomer cement using microabrasion and tin-plating (Group 4) was significantly stronger than all other groups except the resin cement with microabrasion and tin-plating (Group 6). CONCLUSION: Microabraded and tin-plated alloy specimens luted with the resin-modified glass-ionomer cement resulted in the greatest mean tensile strengths for the resin-modified glass-ionomer cement groups. This strength was 73% of the mean tensile strength of microabraded specimens luted with resin cement.

Aluminum Oxide↗
PubMed2001

A comparison of 3 alloy surface treatments for resin-bonded prostheses.

PURPOSE: The most frequent cause of clinical failure of resin-bonded fixed partial dentures is a debonding at the metal-cement interface. The purpose of this in vitro study was to compare the tensile bond strengths of 3 different alloy-surface treatments when cemented to human enamel with a resin cement. MATERIALS AND METHODS: Cylinders of a nickel-chromium-beryllium (Ni-Cr-Be) and a gold-palladium (Au-Pd) alloy were fabricated and assigned to different surface treatment groups as follows: Group 1: Ni-Cr-Be, chemically etched; Group 2: Au-Pd, airborne particle-abraded and tin-plated; and Group 3: Au-Pd, airborne particle-abraded and treated with the Alloy Primer (Kuraray Co, LTD, Osaka, Japan). The cylinders were bonded to the enamel surfaces of extracted, human third molars and stored in normal saline at 37 degrees C for 48 hours. The tensile bond strength of 21 specimens from each group was measured on a Universal Testing Machine (Instron, Canton, MA). Three failed specimens of each group were evaluated using scanning electron microscopy and energy dispersive spectroscopy. RESULTS: Statistically significant differences (p <.05) were found between all 3 treatment groups. The mean tensile bond strengths (+/- the standard error of mean) recorded as follows: Group 1: 10.6 MPa (+/-1.3), Group 2: 0.9 MPa (+/-0.2), and Group 3: 13.4 MPa (+/-1.0). Specimens from groups 1 and 3 revealed a trend towards mixture of cohesive, within the resin cement, and adhesive failures at the metal-cement interface. Group 2 specimens exhibited primarily adhesive failures at the metal-cement interface. CONCLUSIONS: The tensile bond strength of Au-Pd alloy specimens was significantly increased with the Alloy Primer.

Acid Etching, Dental↗
PubMed2007

Cementable implant crowns composed of cast superstructure frameworks luted to electroformed primary copings: an in vitro retention study.

OBJECTIVE: The aim of this in vitro study was to investigate, on ITI solid abutments, the retention values of single crowns fabricated using an alternative prosthetic solution: secondary cast superstructure luted to an electroformed primary coping. MATERIALS AND METHODS: Fifty standard 4.1 mm ITI implants and 5.5 mm high ITI machined abutments were assembled and mounted in acrylic resin. Implant/abutment assemblies were randomly divided into two groups. In the test group, primary galvanic caps were directly fabricated on implant abutments (A.G.C. Micro machine), and a secondary cast noble alloy superstructure was luted on each primary galvanic cap with a resin cement (Nimetic Cem). In the control group, prefabricated burn-out caps were used for casting the metal frameworks. Test and control crowns were cemented using a resin cement (Panavia 21). After storage at 37 degrees for 24 h, the specimens were subjected to a pull-out test using an Instron universal testing machine. The load required to dislodge each sample and the respective mode of failure were recorded. Means and standard deviations of loads at failure were analyzed using ANOVA. Statistical significance was set at P< or =0.05. RESULTS: The retention values (+/-SD) of loads at failure were 67.26 (+/-16.61) for the test group and 44.03 (+/-9.45) for the control group. In the test group no separation occurred between the electroformed (galvanic) primary cap and the secondary superstructure. CONCLUSIONS: The results showed that this prosthetic solution is superior on retentive performance than the conventional cast framework. An added clinical advantage of this novel method is its potential to provide a totally passive fit. Further in vitro and in vivo studies involving multiple-unit restorations are needed in order to more generally validate this prosthetic concept.

Cementation↗
PubMed1985

Nickel allergy: analysis of metal clothing objects and patch testing to metal samples.

In 22 nickel-sensitive subjects, 57 metal clothing objects were said to be not tolerated (37) or tolerated (20). They were analysed by X-ray energy dispersion in electron microscopy, and by the dimethylglyoxime spot test. The correlation between the analytical results and the statements of patients is discussed. Patch tests to nickel-plated metal samples with various thicknesses of chromium (0.25 mu to 1 mu) or gold/copper/cadmium (0.5 mu) were performed in human subjects or in guinea pigs sensitive to nickel. Surface-plating and anticorrosive techniques, as well as the results in nickel-sensitive subjects, are described and discussed. Good tolerance will not be obtained under experimental conditions if nickel in any form is a component of the object. It is to be hoped that appropriate regulations will prohibit the use of nickel in the manufacture of clothing objects.

Adolescent↗
PubMed1988

Nickel allergy: tolerance to metallic surface-plated samples in nickel-sensitive humans and guinea pigs.

The purpose of this work is to evaluate in nickel-sensitive patients and guinea pigs the tolerance to nickel samples, surface-plated with one or several metals of varying structures and thicknesses. All the metal samples elicited allergic reactions in the guinea pig. In humans, absolute tolerance was not observed for any sample. In humans, the interposing of a layer of bright copper between nickel and surface chrome greatly increased the tolerance.

Adolescent↗
PubMed1997

Exposure of nickel in used and unused gold-plated earrings: a study using scanning electron microscopy and X-ray microanalysis.

Nickel is the most common contact sensitizer in the female population. The aim of the present study was to examine closely the surface of both used and unused gold-plated earrings by scanning electron microscopy, and to ascertain the distribution of nickel on the surface of these earrings qualitatively and quantitatively by X-ray microanalysis. The claps of 4 sets of used earrings causing nickel dermatitis and of the 3 sets of unused earrings were examined. In backscattered electron images obtained by scanning electron microscopy, a large number of scratches and pits were found on the surface of the used earrings. Cross-sections of the surfaces confirmed that the gold plating was defective in some areas, exposing the nickel. Nickel was readily detected and quantitatively determined in the scratches and pits by X-ray microanalysis. We also found that, even in unused earrings, numerous scratch marks and pits were present, again exposing the nickel. Clearly, even in unused earrings, nickel exposed at the surface sensitizes the skin and causes contact dermatitis.

Dermatitis, Contact↗
PubMed2002

Enhanced periodontal response and esthetics of implant-supported bridge by the use of galvanoforming technique: case report.

BACKGROUND: Galvanoforming restorations have been placed over the past 15 years successfully. They offer several advantages over alloy restorations, including enhanced response to the periodontal tissues, biocompatibility, and superior esthetics. PURPOSE: The purpose of this report is to show the use of the galvanoforming process in dental implant restorations to transfer the benefits of this technique. MATERIALS AND METHODS: Two standard Brånemark fixtures were placed submerged in the lower mandible for the restoration of a three-unit bridge. The impression was taken at fixture level, and two cast individual telescope abutments were inserted. The galvanoforming restoration was seated conventionally without any screw retention. RESULTS: An implant-supported galvanoforming bridge is functioning successfully. The use of biocompatible materials does not compromise the stability of the restoration; instead, the effect on the periodontal tissues is excellent, resulting in less plaque accumulation and bleeding on probing. Microgaps were avoided by conventional seating on the individual telescope gold abutments, revealing superior occlusal esthetics. CONCLUSIONS: This case report demonstrates the practicability of the biocompatible galvanoforming procedure for implant-supported restorations enhancing periodontal response and esthetics.

Biocompatible Materials↗
PubMedDate not supplied

Repair of porcelain/metal restoration with resin bonded overcasting.

Porcelain occasionally fractures from ceramometal fixed partial dentures following final cementation. Repair of these porcelain fractures can be a challenging task. When the problem occurs on anterior teeth, it is especially difficult because the repair must not only be durable, but esthetically pleasing as well. Although composite resins can be used for some repairs, it is often difficult to match the color and texture to the surrounding intact porcelain. In addition, the bonding between the resin and porcelain is susceptible to margin leakage, which may ultimately cause an esthetic failure. Techniques involving a cemented porcelain-fused-to-metal overcasting have often been successful in restoring the fixed partial denture to form and function. Although the esthetic result of a porcelain/metal overcasting can be quite successful, retention of the overcasting is sometimes poor. The compromised retention and resistance form is due to lack of interproximal walls on the underlying fractured unit. To improve the retention of the overcasting, the following technique of tin plating the overcasting and fractured unit prior to cementing with a composite resin cement is presented.

Dental Bonding↗
PubMed1987

A mortality study of nickel/chromium platers.

The mortality experienced by a cohort of 2689 nickel/chromium platers between 1946 and 1983 has been investigated. All members of the study cohort had some period of chrome exposed employment. Overall, compared with the general population of England and Wales, statistically significant differences relating to cancer were found for cancer of the stomach (E = 16.2, O = 25), primary cancer of the liver (E = 0.8, O = 4), cancer of the nose and nasal cavities (E = 0.3, O = 3), cancers of the lung and bronchus (E = 48.1, O = 72), and all cancers (E = 164.2, O = 213). Chrome bath workers are the more heavily exposed workers, and a striking difference in SMRs was found for lung cancer among men first employed as chrome bath workers (SMR = 199) and men first employed as other chrome workers (SMR = 101). The method of regression models in life tables (RMLT) was used to compare the durations of chrome exposed employment of those dying from causes of interest with those of all matching survivors in the same year of follow up, while controlling for sex, and for year and age of starting employment. Significant positive associations were found only for cancers of the lung and bronchus and duration of chrome bath work. In this study exposure to nickel was shown not to be an important confounding exposure.

Chromium↗
PubMed1997

Memory artifact related to selenium-based digital radiography systems.

Digital images acquired on radiography systems with amorphous selenium detectors are susceptible to "memory artifacts" from prior x-ray exposures. In routine clinical use and in a laboratory experiment, artifacts appeared in chest radiographs until the selenium recovered from initial exposure. Memory artifacts were eliminated when 3 minutes or more elapsed between acquisition of a lateral chest radiograph and acquisition of the next radiograph.

Aluminum↗
PubMed2004

Synthesis and characterization of extremely uniform Fe-Co-Ni ternary alloy nanowire arrays.

We have fabricated extremely uniform arrays of polycrystalline Fe-Co-Ni ternary alloy nanowires having composition Fe 12.3 wt.%, Co 43.9 wt.% and Ni 43.8 wt.%. The wires are made by electrodeposition into nanoporous alumina templates, using an electrodeposition voltage of 15 V at 1000 Hz. Nanowires have been fabricated having diameters ranging from 43 nm to 120 nm, and lengths of 3 microm to 7 microm, as dependent upon template topology. The magnetization easy axis lies along the nanowire length, with an easy axis coercivity of 72 kA/m.

Alloys↗