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Biomedical subjects

W A Brantley

Publications and source records attributed to W A Brantley.

At least 55 records · Page 3Linked to original sources
PubMed1993

Porcelain adherence to high-palladium alloys.

The adherence of porcelain to four representative high-palladium alloys of the first generation (Pd-Cu-Ga) and second generation (Pd-Ga) was measured by use of a gold-palladium alloy as a control. The area fraction of adherent porcelain after metal-ceramic specimens were debonded in biaxial flexure at constant strain was calculated from the characteristic Si x-ray intensity with a standardized scanning electron microscope/energy-dispersive spectroscopy technique (SEM/EDS). The gold-palladium alloy exhibited the highest percentage of cohesive fracture through the porcelain, the two first-generation alloys were intermediate, and the two second-generation alloys exhibited the lowest area fractions. This study demonstrated that conventional visual (naked eye) or microscopic examination of the fractured metal-ceramic specimens at moderate magnification and the use of standard quantitative metallographic techniques were inadequate to provide accurate measurements of the area fraction covered with porcelain.

Analysis of Variance↗
PubMed1993

Titanium alloy cylinders in implant framework fabrication: a study of the cylinder-alloy interface.

Titanium alloy has been proposed as a suitable alternative to noble metal alloys in premanufactured metal cylinders for fabricating implant prosthesis frameworks. The interfaces produced by standard lost wax procedures that use titanium and conventional noble metal implant cylinders with both high-fusing (high-palladium) and low-fusing (high-gold) noble metal casting alloys were compared. Elemental analysis by scanning electron microscopy and energy-dispersive spectroscopy (SEM/EDS) of the two titanium cylinders revealed that one commercial product had a composition similar to that for commercially pure titanium and the other had a composition consistent with that for Ti-6Al-4V alloy. The SEM observations and complementary elemental line scans indicated that the interfaces between the titanium cylinders and the two noble metal casting alloys did not meet proposed criteria for acceptable metal-to-metal unions. The interfaces between the noble metal cylinders and noble metal casting alloys did exhibit acceptable unions. The SEM observations and elemental analyses were supported by push-shear test results that showed that the resistance to failure was appreciably greater for interface specimens produced with alloy cast to noble metal cylinders compared with titanium cylinders.

Alloys↗
PubMed1993

Composite microfiller content and its effect on fracture toughness and diametral tensile strength.

Previous studies have examined the relationship between total filler content in hybrid restorative composites and some of their mechanical properties. This investigation evaluated the effect of varying the amount of microfiller in an experimental hybrid composite on fracture toughness (single edge-notch technique) and diametral tensile strength. The microfiller content in the experimental hybrid composite was varied from 0-44 wt% for seven specimen groups, while the total filler content ranged from 77-84 wt%. It was found that 9 wt% microfiller loading produced the highest mean fracture toughness (1.33 MPa.m(1/2)) and 44 wt% loading produced the lowest mean value (0.80 MPa.m(1/2)). Only the 9 wt% microfiller content group differed significantly in fracture toughness from the other specimen groups. The diametral tensile strength displayed only small differences for the range of microfiller content studied with mean values ranging from 42.1-49.6 MPa. Additional research on the viscoelastic properties of these heavily filled hybrid composites may provide some insight into the differences for the fracture toughness and diametral tensile strength results.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1993

Bending and metallurgical properties of rotary endodontic instruments. IV. Gates Glidden and Peeso drills.

A laboratory study was performed on Gates Glidden and Peeso drills to determine the bending characteristics and related metallurgical properties. Sizes #1 to #6 stainless steel Gates Glidden drills, sizes #1 to #6 stainless steel and carbon steel type P Peeso drills, and sizes #009 to #023 carbon steel-type B-1 Peeso drills were evaluated in cantilever bending with a Tinius Olsen stiffness tester. The bending moments were measured for a 12.5-mm test span at deflection angles of 2 to 90 degrees. The mean maximum bending moments in g cm and the corresponding deflection angles in degrees were plotted graphically to ascertain the bending characteristics of the instruments. The stainless steel Gates Glidden and Peeso drills exhibited considerable permanent bending deformation during testing. Some stainless steel drill samples were able to withstand the full bending deflection of 90 degrees without fracturing. In contrast, the carbon steel Peeso drills were able only to undergo bending deflections of less than 20 degrees and exhibited brittle fracture. If the drill fractured during the in vitro testing, the failure site was always located near the handpiece end.

Dental Cavity Preparation↗
PubMed1993

Thermal diffusivity of glass ionomer cement systems.

The thermal diffusivity has been measured for 10 glass ionomer and resin-based materials: three conventional (water-hardened) glass ionomer cements, two silver-reinforced glass ionomers, an experimental stainless steel-reinforced glass ionomer, three visible light-cured (VLC) glass ionomer-resin hybrid materials, and a VLC resin-based product developed for the same clinical uses as the hybrid materials. Cube-shaped specimens, c. 10 x 10 x 10 mm, initially at room temperature were immersed in mercury surrounded by an ice-water bath. From the experimental cooling curve a semi-log plot of relative temperature decrease vs. time yielded a straight line whose slope is proportional to the thermal diffusivity. The values ranged from 1.74-5.16 x 10(-3) cm2 s-1, and all of the materials tested would have adequate insulating properties provided normal clinical thickness levels for lining materials are maintained. It was found that the thermal diffusivities for the three metal-reinforced glass ionomers, where composition information is available, do not follow a rule of mixtures applied to the individual components.

Cermet Cements↗
PubMed1993

Cobalt-chromium and nickel-chromium alloys for removable prosthodontics, Part 1: Mechanical properties.

PURPOSE: This investigation compared the mechanical properties of three base metal casting alloys (Vitallium2, Neoloy N [Regular], and Regalloy T) for removable partial denture (RPD) frameworks with those for two base metal RPD alloys (Vitallium, Jelenko LG) whose mechanical properties had been previously reported. MATERIALS AND METHODS: Plastic patterns with dimensions meeting ADA specification no. 14 requirements were used with appropriate casting investments to cast tensile test bars of the five alloys. Nine specimens of each alloy were loaded to failure, and the mechanical properties of modulus of elasticity, 0.1% yield strength, 0.2% yield strength, and tensile strength were obtained from five well-behaved load-elongation plots. Values of percentage elongation were also determined, along with Vickers hardness of the work-hardened alloys from polished cross-sections of fractured tensile specimens. The fracture surfaces for representative specimens of each alloy were examined with a scanning electron microscope. RESULTS: Although the measured values of mechanical properties generally agreed with those reported by the manufacturers, differences found for Vitallium and Jelenko LG with previous investigations suggest that there may have been some changes in alloy compositions and processing by the manufacturers. The investment burnout procedure adopted for the plastic patterns and the present casting conditions may also have affected the mechanical properties of some alloys. Two alloys, Jelenko LG and Regalloy T, had mean values of percentage elongation exceeding 10%, but caution is recommended for clinicians and dental laboratories when performing clasp adjustments with all five alloys because of the substantial work hardening that can occur. CONCLUSIONS: In general, all of the alloys met the requirements in ADA specification no. 14 for base metal RPD alloys. Further research will be necessary to determine the relationships between the mechanical properties, particularly yield strength, rate of work hardening and percentage elongation, and the clinical requirements for these alloys.

Analysis of Variance↗
PubMed1993

A photoelastic and strain gauge analysis of angled abutments for an implant system.

This study was conducted to determine the effect of abutment angulation on the stress field near a specific dental implant. Photoelastic resin was cast directly to five 3.8 x 10-mm Steri-Oss implants in 50 x 70 x 13-mm molds. One additional model was fabricated with a strain gauge rosette embedded in the resin to allow precise determination of normal stresses. Zero-degree, 15-degree, and 20-degree abutments were assembled on each of the six implants, subjected to 178 N load, and viewed with a circular polariscope. Observed fringe patterns were photographed for all six models, and strain indicator readings were recorded for the strain gauge model. Numerical data from the strain gauges produced results that agreed with the visual interpretation of the isochromatic fringes. Strain gauge data were also used to calculate the principal stresses and strains. Although a statistically significant increase in stress and strain was found for each increase in abutment angulation, all three abutments produced principal strains that appear to be within the physiologic zone for bone. All values for stress and strain were determined at the location of the rosette, approximately 4 mm from the implant. Higher stresses and strains exist in regions closer to the fixture.

Analysis of Variance↗
PubMed1992

Physical dimensions, torsional performance, and metallurgical properties of rotary endodontic instruments. 3. Peeso drills.

A laboratory study was performed on Peeso drills to determine their physical dimensions, torsional performance, and metallurgical properties. Samples were measured from each of sizes #1 to #6 of Peeso drills (type P) and sizes #009 to #023 of Peeso drills (type B-1) from the two manufacturers that distribute these instruments in the United States. They were also tested in clockwise and counterclockwise torsion using a digital torque meter instrument. It was not possible to evaluate completely some type P drills of size #4 and larger or type B-1 drills of size #016 and larger because the torsional moments exceeded the capacity of the test instrument. Scanning electron microscopic examination confirmed visual observations that the stainless steel Peeso drills exhibited ductile torsional fracture, in contrast to the carbon steel Peeso drills which fractured in a relatively brittle manner. The carbon steel Peeso drills exhibited a much greater tendency for torsional fractures in the bur head, along with considerably smaller values of angular deflection at separation compared to the stainless steel Peeso drills. This study is part of a continuing investigation to establish standards for all rotary endodontic instruments.

Dental Cavity Preparation↗
PubMed1991

Bending properties of superelastic and nonsuperelastic nickel-titanium orthodontic wires.

Cantilever bending properties were evaluated for several clinically popular sizes of three superelastic and three nonsuperelastic brands of nickel-titanium orthodontic wires in the as-received condition, and for 0.016-inch diameter wires after heat treatment at 500 degrees and at 600 degrees C, for 10 minutes and for 2 hours. A torque meter apparatus was used for the bending experiments, and the specimen test-span length was 1/4 inch (6 mm). In general, the bending properties were similar for the three brands of superelastic wires and for the three brands of nonsuperelastic wires. For the three brands of superelastic wires, heat treatment at 500 degrees C for 10 minutes had minimal effect on the bending plots, whereas heat treatment at 500 degrees C for 2 hours caused decreases in the average superelastic bending moment during deactivation; heat treatment at 600 degrees C resulted in loss of superelasticity. The bending properties for the three brands of nonsuperelastic wires were only slightly affected by these heat treatments. The differences in the bending properties and heat treatment responses are attributed to the relative proportions of the austenitic and martensitic forms of nickel-titanium alloy (NiTi) in the microstructures of the wire alloys.

Dental Alloys↗
PubMed1991

Torsional and metallurgical properties of rotary endodontic instruments. 2. Stainless steel Gates Glidden drills.

A laboratory study was performed on stainless steel Gates Glidden drills to determine their torsional and metallurgical properties. Samples of #1 to #6 drills from the two manufacturers that distribute these instruments in the United States were tested in incremental and continuous clockwise torsional loading by using a digital torque meter. The values of mean torque at fracture obtained with these tests generally showed no statistically significant differences for the same drill size and a given manufacturer. However, it was not possible to completely evaluate drill sizes #5 and #6 because the torsional moments developed during testing exceeded the capacity of the test instrument. Scanning electron microscope examination confirmed the occurrence of ductile torsional fracture processes, which were evident from visual observation of the instruments after fracture. This study is part of a continuing investigation to establish standards for all rotary endodontic instruments.

Dental Instruments↗
PubMed1990

Physical dimensions and torsional properties of rotary endodontic instruments. 1. Gates Glidden drills.

A laboratory study was performed on Gates Glidden drills to determine their physical dimensions and torsional properties. Five samples of sizes #1 to #6 drills from two brands distributed in the United States were measured for physical dimensions. Five samples of the most commonly used sizes #1, #2, and #3 drills from these two brands were tested at failure in both the clockwise and counterclockwise directions using an analog torque meter. The values for the bur head dimensions of both brands correspond closely to those established by the ISO. The mean values for torque at failure for both the clockwise and counterclockwise directions showed no statistically significant difference for each brand-size combination. However, some instrument groups had separation or fracture sites near the bur head, while other groups underwent failure near the hand-piece end. This study is the first part of a continuing investigation to establish standards for rotary endodontic instruments.

Dental Instruments↗
PubMed1988

Effects of appliance size, arch wire diameter, and alloy composition on the in vitro force delivery of the quad-helix appliance.

The quad-helix appliance is a fixed lingual arch wire appliance that produces slow maxillary expansion for the treatment of maxillary constriction or crossbite in the primary and mixed dentitions. Despite considerable success in the clinical treatment of patients, there is little quantitative information about the force delivery of this appliance. The purpose of this investigation was to characterize the in vitro force delivery of the quad-helix appliance. Appliances of four sizes were fabricated from Elgiloy blue and stainless steel wires with diameters of 0.032, 0.036, and 0.038 inch. The force delivery in grams for 8-mm activation was determined from the force-extension characteristics using an Instron mechanical testing machine. The results show that the force delivery of the quad-helix appliance is affected significantly by changes in the appliance size and arch wire diameter, but is independent of alloy type (stainless steel or Elgiloy blue). The quantitative results from this investigation should provide worthwhile information for clinical appliance selection and treatment of patients with varying arch dimensions.

Dental Alloys↗
PubMed1988

Structure and mechanical properties of as-received and heat-treated stainless steel orthodontic wires.

A combination of x-ray diffraction analysis with mechanical testing in tension and bending has been used to investigate the metallurgical structures and mechanical properties for as-received and heat-treated stainless steel orthodontic wires. Two different proprietary wire types were selected, having a wide range in cross-sectional dimensions: 0.016-, 0.030-, and 0.050- or 0.051-inch diameters, and 0.017 X 0.025-inch rectangular specimens. Heat treatments were performed for 10 minutes in air at temperatures of 700 degrees, 900 degrees, and 1100 degrees F. The x-ray diffraction patterns showed that the as-received 0.016-inch diameter and 0.017 X 0.025-inch wires of both proprietary types consisted of a two-phase structure containing a martensitic phase along with the austenitic phase. This duplex structure was converted entirely to austenite with heat treatment for one wire type, but persisted after heat treatment for the other wire type. The largest diameter, 0.050- or 0.051-inch, wires of both types were single-phase austenitic structure for both the as-received and heat-treated conditions. Evidence of substantial preferred crystallographic orientation or texturing in these orthodontic wires was also found by x-ray diffraction. As in our previous studies, the modulus of elasticity in bending was significantly less than the value obtained in tension for only the smaller cross-sectional wires. The 0.05 radian flexural yield strength correlated more closely with the 0.2% offset yield strength in tension than with the yield strength for 0.05% and 0.1% permanent offsets.

Chemical Phenomena↗
PubMed1987

Evaluation of biangular reflection photometry for quantitative study of etched alloy surface roughness.

Biangular reflection photometry was correlated with quantitative stereology and direct pit-depth measurements for an electrolytically etched nickel-chromium-beryllium alloy. Effects of viewing angle, viewing aperture, and plane polarization of incident and viewing light were also studied. The results showed that architectural changes in the etched metal surface could be quantitatively described with the use of reflection photometry. An off-specular peak, located at an angle of reflection considerably different from the angle of incidence, was observed to have an intensity comparable with that of the specular reflection peak. Viewing aperture was found to affect one's ability to distinguish among degrees of surface roughness.

Acid Etching, Dental↗
PubMed1986

Comparison of bending and tension tests for orthodontic wires.

Stainless steel, cobalt-chromium-nickel (Elgiloy), nitinol, and beta titanium wires with diameters from 0.010 to 0.040 inch and in rectangular sizes from 0.017 X 0.025 to 0.019 X 0.025 inch were evaluated with the American Dental Association specification no. 32 bending test and the conventional tension test. The modulus of elasticity (E) and yield strength (YS) obtained with the two mechanical testing procedures are reported for as-received wires and after heat treatment at 900 degrees F for the stainless steel and selected Elgiloy wires. Measured values of E and YS in bending were almost invariably higher than the corresponding values obtained in tension. The only general agreement between the modulus of elasticity in bending and tension was for the 0.040-inch diameter stainless steel wires. Anomalously high values of E in bending were also found for most of the heat-treated stainless steel and Elgiloy groups. Difficulties with the bending test are attributed to loading effects at both ends of the test span and deviation of the bent specimen from a circular arc. Improved procedures are described for performing the tension test on the relatively small cross-section orthodontic wires.

Alloys↗