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At least 577 records · Page 32Linked to original sources
PubMed2001

Treatment behavior and complete-mouth rehabilitation using AGC crowns: a case report.

This case report covers the combined functional and perioprosthetic complete-mouth rehabilitation of a 67-year-old patient with severe temporomandibular joint pain caused by a prognathic forced incorrect centric relation and severe overclosure. Once bite guard treatment had been concluded and the pain had subsided completely, AGC electroformed crown and bridgework was fabricated. Electroformed crown-and-bridge copings exhibit extremely high precision of fit and, from the clinical point of view, perfect esthetics. As the coping material is pure gold and there are no bonding oxides in the gold-porcelain bonding layer, AGC restorations are readily integrated into the biologic structures around the crown margins. Perfectly healthy, noninflamed soft tissues, a lack of bluish-livid colored gingival margins, and visible gingival reattachment around the crown margins are considerable benefits from the perioprosthetic point of view. This leads to foreseeable clinical success and promises further use of electroformed porcelain restorations.

Aged↗
PubMed1995

Scientific and technological results from the Consort rocket program.

The Consort suborbital rocket program was initiated to allow industrial researchers working through the various NASA Centers for Commercial Development of Space to have ready access to 6 to 7 min of microgravity environment for the purpose of trying out new ideas and for testing apparatus being developed for longer duration Shuttle flights. The 6 Consort flights have provided a wealth of experimental data, some of which has not been published in the open literature. The purpose of this paper is to document the experiments that have been flown and what has been learned. A fairly extensive bibliography of the published results has been included, and the investigator team responsible for the various experiments has been included so that interested parties may contact the various investigators directly for more details.

Acceleration↗
PubMed1999

Bonding procedures for intraoral repair of exposed metal with resin composite.

PURPOSE: To determine if tin plating can be recommended for intraoral repair of ceramic veneered cast restorations where metal of unknown composition is exposed by loss of ceramic. This study investigated the effectiveness of surface treatments incorporating tin plating and unfilled resin to enhance the tensile bond strength of a resin composite restorative to three different metal ceramic casting alloys. MATERIALS AND METHODS: Gold-platinum, palladium-tin and nickel-chromium alloys were used to fabricate 120 rods of each alloy, 4 x 15 mm. The end of each rod was ground perpendicular on 600-grit SiC paper and grit blasted with 50-micron alumina. Rods from each alloy were divided into four groups of 30 to receive one of the following treatments before bonding pairs end to end with a visible light-polymerized resin composite (Herculite XRV): 1) direct bonding with the resin composite; 2) tin plating (Micro-Tin) and bonding; 3) application of unfilled resin (Chameleon) and bonding; 4) tin plated, application of unfilled resin and bonding. The bonded samples were stored in distilled water, incubated at 37 degrees C for 24 hours and tested for tensile bond strength at a crosshead speed of 1 mm/min in a Lloyd 1000R machine. The mode of failure was examined using a stereo zoom microscope. RESULTS: A statistically significant increase in tensile bond strength was demonstrated between the control (group 1) and both the gold and palladium alloy treated with tin plating and unfilled resin (group 4). Tin plating, or tin plating with the application of unfilled resin had no statistically significant effect on the tensile bond strength of resin composite to the nickel-chromium alloy. CONCLUSION: The results demonstrate that tin plating, in conjunction with the application of a low-viscosity unfilled resin, optimizes the tensile bond of a resin composite to the three alloys used in the study. This procedure can be recommended for intraoral repair of exposed metal when the type of alloy belongs to one of the investigated alloy groups.

Analysis of Variance↗
PubMed2001

The influence of surface configuration on the retention of posts designed for use with a cast-on technique.

OBJECTIVES: The combination of an individually cast core and a prefabricated metal post is one of the many techniques to restore endodontically treated teeth. The surface characteristics of commercially available posts vary considerably and likely influence retention. In this study, the surface configuration of 11 castable prefabricated post systems and their retention at the post-cement interface were investigated. METHOD AND MATERIALS: Scanning electron microscopic photos were made to assess surfaces of the posts. Etchant residues or applied surface layers were also analyzed with an electron beam microprobe. For the retention measurements, 6 posts from each system were cemented in artificial root canals with a zinc phosphate cement. Retention was measured on a universal testing machine. RESULTS: Analysis of variance and the Ryan-Einot-Gabriel-Welsch F test revealed significant differences in retention between posts; these differences were related to the microstructure of the surfaces of the posts. In general, the coarser the surfaces, the better the retention. Gold plating of the etched surface for one manufacturer resulted in less retention compared to posts of the same type and size that were not plated. CONCLUSION: The surface configuration of a post could be an important factor when selecting a prefabricated post system.

Acid Etching, Dental↗
PubMed2000

Bond strengths and patterns of failure of a zinc polycarboxylate cement on surface-treated gold alloys.

The study investigated the shear strengths and fracture characteristics of a zinc polycarboxylate cement on three sets of type III gold alloy bars whose surfaces were modified by alumina blasting, heat treatment and tin plating respectively. Each set comprised 20 bars with similarly treated surfaces, cemented in pairs with the polycarboxylate cement and stored in water at 37 degrees C for 48 hours. The cement bond was then stressed to failure by application of forces in shear mode and the bond strength was determined. The mean bond strength for each type of treated gold alloy surface was calculated and then compared with the others by way of statistical analysis. The failed surfaces were observed and photographed with a stereophotomicroscope for subjective evaluation of the character of the failed surfaces. The strongest bonds were formed on the alumina-blasted surfaces where 70% of the bonds failed in an adhesive-cohesive fashion. The weakest bonds were formed on the tin-plated surfaces where cement failure was entirely adhesive. Bond strengths on the heat-treated surfaces were intermediate and a cohesive failure pattern was observed on 80% of the specimens. The differences in bond strengths on the three surfaces were statistically significant.

Adhesiveness↗
PubMedDate not supplied

[Possibilities of metallic-ceramic link optimization by electrodeposition].

To reach a good link between the metallic framework and the ceramic element of a bridge represents one of the most important aim of the clinical and technical steps of the dental treatment for partial edentulous patients. The purpose of this study was represented by the analysis of the electrodeposition method in enhancing of the metalo-ceramic link. We used an electrogalvanic bath inside which we introduced a metallic framework which has been improved by electrodeposition of a thin layer of gold. The results showed a stronger and more stable link between the metallic framework and the ceramic element.

Crowns↗
PubMed1992

[Study on casting precision of plat castable ceramic crowns].

The plat castable ceramic crown was made with investment material prepared in our college with our own casting technique by a Chinese-made casting machine. The accuracy and fitness of the crown were studied and appraised. Results show that the margin of fitness is 46 microns and that the cement film thickness of the dies in the spacer material group is 65.13 microns. Hence the results are satisfactory. The Plat castable ceramic crown might be used in clinical dentistry.

Crowns↗
PubMed2003

Microleakeage and resin cement film thickness of luted all-ceramic and gold electroformed porcelain-fused-to-metal crowns.

PURPOSE: The purpose of this study was to evaluate the sealing ability of single-unit all-ceramic and gold-electroformed crowns luted with a resin cement under laboratory conditions. MATERIALS AND METHODS: Thirty extracted maxillary premolars were selected. Standardized abutments were prepared for full-crown restorations with cervical margins located 1 mm below the cementoenamel junction. Samples were divided into two groups (n = 15) based on type of restorative system: Group 1: a heat-pressed all-ceramic system (IPS Empress 2, Ivoclar-Vivadent); Group 2: a gold-electroformed porcelain-fused-to-metal system (Gramm Technik). Crowns were luted with Excite DSC bonding system (Ivoclar-Vivadent) and Variolink II resin cement (Ivoclar-Vivadent) following manufacturer's instructions. After luting procedures and 700 thermal cycles (5 degrees C and 55 degrees C, 1 min dwell time), 20 specimens (n = 10 per group) were randomly selected and processed for microleakage evaluation at cervical sites. The remaining specimens (n = 5 per group) were prepared for SEM investigation on film thickness. Microleakage and film thickness data were statistically evaluated using the Mann-Whitney U-test (p < 0.05). RESULTS: Fifty percent of group 1 and 60% of group 2 samples showed leakage. For group 1, dye penetration was mostly observed between metal and resin material, while group 2 specimens showed leakage mainly between ceramic margins and resin cement. Samples from group 1 showed a cement thickness of 82 microm, while 71 microm was found for group 2. Statistically significant differences were not found between samples from the two groups. CONCLUSION: Regarding microleakage and film thickness, both restorative systems evaluated in this study performed similarly.

Bicuspid↗
PubMedDate not supplied

Hydroxyapatite coating on a titanium metal substrate by a discharging method in modified artificial body fluid.

PURPOSE: The aim of this study was to evaluate the formation of a hydroxyapatite coating on titanium plate by discharging in typical and modified artificial body fluids. MATERIALS AND METHODS: Japanese Industrial Standard Grade 2 titanium plates were used as specimens. Discharging was performed on the specimens in each solution, and the surface topography of each coating was observed with a scanning electron microscope. The Ca/P atomic ratio and surface characterization of each coating were evaluated by x-ray photoelectron spectroscopy, and crystal phases of each coating were analyzed by Fourier transform infrared spectroscopy and x-ray diffraction. RESULTS: Tricalcium phosphate formed on the titanium surface in a 1.5 Ca/P solution with high ion concentrations of calcium (2.5 mmol/L) and phosphorous (1.67 mmol/L). Crystalline HA was formed on the titanium surface in a 1.5 Ca/P solution (Hanks' balanced salt solution without organic molecules) with low ion concentrations of calcium (1.26 mmol/L) and phosphorus (0.83 mmol/L). DISCUSSION: A solution containing organic pH buffer was insufficient to form stable coatings on the titanium surface. Coating properties strongly depended on the Ca/P chemical ratio of the applied solution. A Ca/P ratio of 1.5 was appropriate for preparing a calcium phosphate coating on a titanium surface, whereas a Ca/P ratio of 2.5 was excessively high. CONCLUSION: These findings suggest that Hanks' balanced salt solution without organic molecules is the most suitable solution for forming crystalline hydroxyapatite coatings on titanium surfaces by the discharging method.

Body Fluids↗
PubMed1992

Effect of bonded gold inlays on fracture resistance of teeth.

The purpose of this study was to determine if bonding gold inlays to tooth structure with an adhesive resin cement would increase the fracture resistance of restored teeth. Extracted paired maxillary premolars were prepared for mesio-occlusodistal inlays, and the inlays were cast in type II gold. In one tooth of each pair, the inlay was sandblasted with aluminium oxide, tin plated, and cemented with an adhesive resin into the etched preparation. For the other (control) tooth in each pair, the inlay was sandblasted and then cemented into the preparation with zinc phosphate cement. The teeth were thermocycled and loaded until fracture. The teeth in the bonded group had a statistically significantly higher fracture resistance than did the teeth in the control group. Scanning electron microscopic examination revealed that failure in the bonded group occurred predominantly within the resin.

Bicuspid↗
PubMedDate not supplied

Surface treatments to improve bond strength in removable partial dentures.

The metal and resin interface of removable partial dentures is weakened by the poor bond strength between the two materials. This study was designed to test the hypothesis that surface treatments--consisting of air abrasion, with aluminum oxide, tin plating and oxidation, and silanation, either alone or in combination--will improve the bond strength of acrylic resin to metal. Statistical analysis revealed that air abrasion, tin plating/oxidation, and silanation all showed significantly higher bond strength than either abrasion and tin plating, abrasion and silanation, or abrasion alone. Air abrasion demonstrated the greatest effect on improving bond strength. The mean bond strength of samples subjected to a combination of air abrasion, tin plating and oxidation, and silanation was significantly greater than any other combination treatment.

Acrylic Resins↗
PubMed2003

A clinical evaluation of the agar alginate combined impression: dimensional accuracy of dies by new master crown technique.

PURPOSE: To evaluate the dimensional accuracy of several impression methods including agar alginate combined impression in vivo; the marginal accuracy of stone dies was determined using a new electroformed master crown technique. MATERIALS AND METHODS: Cast cores with knife-edge and chamfer margins and electroformed master crowns were fabricated for 3 patients. Five impressions were taken of each preparation, using agar alginate combined impression and silicone impression materials. Dies were made after impression. The marginal fit of the master crown on each die was analyzed by four-way analysis of variance (ANOVA) and Tukey HSD test (p<0.05). RESULTS: The marginal fit of the master crown on the dies with chamfer margin was better than those with knife-edge margin for agar alginate combined impression. The shape of the margin did not affect the accuracy when silicone impression material was used. CONCLUSIONS: The results suggest that the agar alginate impression method is clinically acceptable for the chamfer margin, but shape of the margin may affect the dimensional accuracy of dies. The shape of the margin does not affect the accuracy of dies when silicone impression was used. Furthermore, the master crown made by electroforming technique could be useful for clinical evaluation of impression methods.

Agar↗
PubMedDate not supplied

The bond strength of porcelain to Ni-Cr alloy--the influence of tin or chromium plating.

Nickel-chromium alloys were plated with tin and chromium to evaluate the effect on porcelain shear bond strength. Six plating methods were used. Additionally, the microstructure of the bond between the plated alloy and porcelain were studied using SEM and EPMA. Tin plating increased the bond strength of porcelain to a nickel-chromium alloy while chromium plating did not.

Chromium Alloys↗
PubMedDate not supplied

[Galvanic technology in the workplace: prevention of occupational tumors].

We studied 10 firms having production processes that involve galvanic technologies, with the goal to verify the "Titolo VII of D.Lgs 626/94". Research results showed out that there are many critical issues that underline the need of an improved awareness about the worker's exposure to carcinigenons materials. We also think that would be useful a greater cooperation among managers, occupational physicians and even workers. Firms cooperated in the research allowing us to fix some items and allowing us to reach results that represent one step ahead in the path through the whole management of cancer hazards: primary healthcare.

Electroplating↗