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At least 1,207 records · Page 67Linked to original sources
PubMed1994

Luminal volume reconstruction from angioscopic video images of casts from human coronary arteries.

Intravascular angioscopy has been hampered by its limitation in quantifying obtained images. To circumvent this problem, a lightwire was used, which projects a ring of light onto the endoluminal wall in front of the angioscope. This investigation was designed to quantify luminal dimensions of casts from stenotic human coronary arteries and to investigate the feasibility of performing volume reconstruction. Angioscopic video recordings were made during simultaneous motorized pullback (2 mm/s) of an angioscopic catheter and light-emitting fiber through 4 epoxy casts from human coronary arteries. Quantification of the images was performed using a computerized cross-sectional area measurement system. The coronary casts were divided into cross-sectional segments of 4 to 10 mm in thickness, with the true volume of each segment determined by means of a microdispenser. Because of vessel curvature and luminal narrowing, complete visualization of the ring of light at all 1-mm-distant locations was only possible in 19 of 40 segments. For these 19 segments, linear regression analysis showed a good correlation between measured and true segmental volume (r = 0.97, y = 0.88x + 6.58 mm3, standard error of estimate = 3.48 mm3). The relative error in the measured segmental volumes was 3.9 +/- 7.1% (mean +/- SD). These initial results of endoluminal volume reconstruction demonstrate the feasibility of this technique in vitro with high accuracy and low variability, but further technical improvements are necessary to increase the success rate, especially in the quantitative assessment of vessels with complex morphology.

Angioscopes↗
PubMed1980

Cast bracing in practice: a two-year study in Aberdeen.

This paper reviews the use of cast bracing of fractures of the femoral shaft over a two-year period in an orthopaedic unit which provides a service to half a million people in the Grampian Region. More than three-quarters of the patients with fractures of the femoral shaft admitted to hospital were treated by cast bracing and these patients are reviewed. In 1976 the cast braces were applied at an average of 6.3 weeks after fracture and in 1977 after an average of 5 weeks, with consequent savings in hospital bed time. The average time to union remained remarkably constant at around 14.5 weeks. The less than good results are looked at critically with a view to avoiding these in the future.

Adolescent↗
PubMed1984

Preliminary results of treatment of fractures of the femur by cast-bracing using the Zaria metal hinge.

This is a prospective study of 27 patients with fractures of the femur at different levels and treated by cast-bracing using the Zaria hinge. The shortest follow-up period is 6 months. The brace was applied after an average of 4.5 weeks in traction. No alignment jigs or other accessory appliances were used. The patients got up 1-3 days after application of the brace and left hospital 5.8 weeks after fracture. Healing of the fracture was judged clinically and radiologically. The patients were pleased with the method. The average time in the brace was 9 weeks and to clinical union was 13.5 weeks. Three patients had shortening of more than 2.5 cm and six fractures were bent by more than 10 degrees but most of these deformities were present before the brace was applied. When the brace was removed the average range of flexion at the knee was 0-80 degrees and 6 months after fracture it was virtually full. The only notable difficulty with the hinge was loosening of the proximal end-plate. It is concluded that the Zaria metal hinge is an effective device for the cast-bracing of fractures of the femur, that alignment jigs and other accessory appliances are not essential for its application and that the cast-brace method is particularly suitable for use in the developing countries because of its effectiveness, simplicity and cheapness.

Adolescent↗
PubMed1990

Backslabs and plaster casts: which will best accommodate increasing intracompartmental pressures?

Plaster-of-Paris backslabs are presently used after closed or operative reduction of fractures as they are thought to accommodate any swelling which may occur. This study was designed to examine the ability of different types of cast to expand with increasing internal pressure. The results of the study show clearly that a split and spread cast is the only safe cast to use after fracture as it allows for swelling. Backslabs are no better than a complete plaster at accommodating increased internal pressure. It is therefore recommended that backslabs are no longer used to maintain reductions when swelling is anticipated.

Casts, Surgical↗
PubMed1983

A mathematical treatise on the fit of crown castings.

A mathematical analysis was given to calculate the marginal cement thickness, Dm, of a cemented crown casting as a function of the minimum cement film thickness, F; the width, W, of the base of the tapered region; the width, W', at the bevel (if present) of the tooth preparation; the taper angle, theta; the marginal angle, beta; and the compensatory expansion, X, of the metal investment system: Dm = [F/sin theta - 0.5(X - 1) (W cot theta - W' cot beta)] sin beta. The elevation of the cemented casting, delta H, above the tooth preparation may also be obtained from this equation by substituting beta = 90 degrees, in which case Dm = delta H. The effect of the preparation of a chamfer margin or bevel on the marginal film thickness may be calculated from this equation. An additional analysis showed that the minimum marginal cement thickness, Dm = F, can be obtained for a shoulder preparation and X values of common metal-investment systems by applying a spacer of appropriate thickness on the entire occlusal and axial walls of the die. This renders the preparation of bevels superfluous. The thickness of the spacer should allow for the cement film thickness, roughness of the tooth and casting surfaces, dimensional inaccuracies of the die, and distortions of the wax pattern. If the spacer is thicker than required, a minimum value of Dm is still obtained for preparations without bevels. If the horizontal part of the die shoulder is covered as well with the spacer, a greater spacer thickness is required to obtain a minimum value of Dm than if the spacer extends to the end of the axial walls. In this case the spacer thickness should be greater on the occlusal die wall than on other regions of the die for values of X smaller than 1. The spacer should also be thicker in the occlusal region if restriction of the investment setting expansion by the wax pattern occurs mainly in this region.

Cementation↗
PubMed1985

Combined die-investment stone and die-stone cast for making resin-retained prostheses.

A technique has been presented for developing a combined die-investment stone/die stone-full arch working cast for use in making a resin-retained prosthesis. The advantage of the technique is that it affords the opportunity to articulate the working cast with a cast of the opposing arch and make the framework directly on a refractory material, while minimizing the subsequent need to trim the refractory material.

Calcium Sulfate↗
PubMed1986

A review of methods and techniques to improve the fit of cast restorations.

Many factors that can affect the overall adaptation of cast restoration margins have been studied. Many methods and techniques have been advocated to improve casting accuracy. Some are time-consuming procedures and others are simple and economical. An acceptable cast restoration depends primarily on the dentist's ability to interpret and evaluate the restoration clinically and radiographically.

Acid Etching, Dental↗
PubMed1987

Effect on the fit of removable partial denture frameworks when master casts are treated with cyanoacrylate resin.

Master casts of improved dental stone were made from irreversible hydrocolloid impressions of a metal model. Half of the master casts were treated with cyanoacrylate resin and half were untreated controls. They were sent to a dental laboratory for framework fabrication. The returned frameworks were examined for acceptability and their completeness of seating was determined. The frameworks fabricated on the treated master casts fit significantly better than the controls. The improved seating may be attributed to an increased surface hardness, increased abrasion resistance, and improved surface morphology, but further study is necessary.

Cyanoacrylates↗
PubMed1991

Spot-welded wire hooks as seating guides for resin-bonded castings.

A technique is described to assist in accurate positioning of cast metal, resin-bonded prostheses. The method is particularly useful for the recementation of castings but can also be used with new restorations. A piece of rectangular chrome alloy arch wire is annealed and spot-welded to the retainer. The wire is then adapted to lie over the incisal edge of the abutment tooth and forms a locating device during trying in and cementing of the restoration. The wire hook assists in the handling of the casting at chairside and is easily snapped off after cementation, leaving little finishing to be completed. The technique permits access to all of the marginal surfaces at cementation and offers certain advantages over existing alternative techniques.

Cementation↗
PubMed1992

Marginal accuracy and geometry of cast titanium copings.

The biocompatibility of titanium with human tissue is well established; its potential as an alternate metal for crown restorations has yet to be fully investigated. This study measured the geometry and accuracy of coping margins cast in Ti, 99.5% chemically pure. Twenty castings with 45-degree facial and 90-degree palatal margins were made by indirect technique with a commercial system using recommended procedures. They were then cemented with ZnPO4 cement. The coping and die assemblies were embedded in resin, sectioned longitudinally, and measured with a microscope at x50 power. Casting shrinkage was characteristic, particularly along the horizontal axis in the plane of the shoulder. Although horizontal linear shrinkage of 45-degree margins was greater than that for the 90-degree form, the surface of marginal discrepancy was greatest with the 90-degree configuration.

Analysis of Variance↗
PubMed1992

Flexible casts used in making indirect interim restorations.

This article describes a procedure for making indirect interim restorations from a cast and dies made of polyvinyl siloxane impression material. The use of these flexible casts and dies facilitates the removal of the polymerized resin from the cast and the rapid set of the polyvinyl materials reduces the time involved in making the indirect interim restorations.

Dental Casting Investment↗
PubMed1993

Passive adaptation of the prosthesis-implant interface by soldering gold cylinders to the framework casting.

Difficulties associated with accuracy of conventional long-span one-piece castings for fixed partial dentures are also observed in the fabrication of implant-supported prostheses. A technique is proposed whereby direct intraoral verification of cylinder-abutment relationship, master cast accuracy, possible corrected cast procedures, and soldering of gold cylinders to the framework ensure an accurate, passive adaptation of the prosthesis to all supporting implants.

Dental Abutments↗
PubMed1993

Radiographic and metallographic evaluation of porosity defects and grain structure of cast chromium cobalt removable partial dentures.

A study was undertaken to determine the defects in the internal microstructure of clasps of cast chromium cobalt removable partial denture frameworks. Ninety cast frameworks were radiographically evaluated for porosity with an industrial radiographic machine. The grain structure of the clasps was analyzed with an optical photomicroscope before and after various heat treatments. The radiographic study showed a large number of internal defects in various parts of removable partial denture frameworks. The grain structure study revealed microporosities randomly distributed within the matrix. Various heat treatments were performed and resulted in no change in the grain structure of the original castings.

Chromium Alloys↗
PubMed1994

A boxing procedure for corrected cast impressions.

This new method for boxing a corrected cast impression for a distal extension removable partial denture improves the procedure. The framework with its impression is seated on the remainder of the cast after anatomic ridges have been removed and luted with sticky wax, and the assembly is inserted into a previously formed thermoplastic box and poured to make a new corrected cast.

Acrylic Resins↗
PubMed1995

X-ray diffraction studies of as-cast high-palladium alloys.

OBJECTIVES: The purpose of this study was to use x-ray diffraction (XRD) to investigate four representative high-palladium alloys in the as-cast condition and obtain new information about the metallurgical phases. METHODS: Two Pd-Cu-Ga alloys and two Pd-Ga alloys were cast into plate-shaped specimens (20 mm x 1.5 mm) which were bench-cooled. Polished and etched specimens were analyzed using two different x-ray diffractometers and CuKa radiation. RESULTS: All four alloys exhibited strong XRD peaks for the face-centered cubic (fcc) palladium solid solution matrix, and variations in the lattice parameter were consistent with alloy compositions. Comparison of the relative peak intensities for the alloys and the pure palladium powder standard indicated that the as-cast microstructures had preferred crystallographic orientation. Because the two Pd-Cu-Ga alloys contained appreciable amounts of near-surface lamellar interdendritic or eutectic constituents, it was possible to determine previously unreported XRD peaks for the Pd2Ga phase in these alloys. Low-intensity peaks in the Pd-Ga alloys were attributed to small amounts of secondary phases observed in the microstructures. SIGNIFICANCE: Knowledge of the metallurgical structures of these high-palladium alloys can be important for interpretation of microstructural observations, mechanical properties, corrosion behavior and clinical performance.

Dental Alloys↗
PubMed1989

Influence of casting procedure on silver-palladium endodontic posts.

Silver-palladium alloys have been endorsed on clinical grounds as substitutes for gold alloys in posts and cores. However, carbon absorption during heating and casting can adversely affect the mechanical properties of silver-palladium alloys. In this study the tensile characteristics of endodontic posts cast in silver-palladium alloy using either a graphite or a ceramic crucible were determined. Graphite crucibles were associated with a significantly lower (2P less than 0.00001) percentage elongation than were ceramic crucibles. The need for a carbon-free casting environment for silver-palladium alloys was confirmed. The configuration of the cylindrical, serrated, vented post used in these tests resulted in mechanical properties lower than those achieved with standard metallurgical test procedures.

Ceramics↗
PubMed2005

Passive stretching does not enhance outcomes in patients with plantarflexion contracture after cast immobilization for ankle fracture: a randomized controlled trial.

OBJECTIVE: To compare the efficacy of short- and long-duration passive stretches with a control treatment for the management of plantarflexion contracture after cast immobilization for ankle fracture. DESIGN: Assessor-blinded, randomized controlled trial. SETTING: Hospital physical therapy outpatient departments. PARTICIPANTS: Adults with plantarflexion contracture (N=150) after cast immobilization for ankle fracture. All subjects were weight bearing or partial weight bearing. INTERVENTIONS: Exercise only, exercise plus short-duration passive stretch, and exercise plus long-duration passive stretch. All subjects had a 4-week course of exercises. In addition, subjects in the short-duration stretch plus exercise group completed 6 minutes of stretching per day, and subjects in the long-duration stretch plus exercise group completed 30 minutes of stretching per day. MAIN OUTCOME MEASURES: Lower Extremity Functional Scale and passive dorsiflexion range of motion with the knee bent and straight at baseline, and at 4 weeks and 3 months postintervention. RESULTS: One hundred thirty-nine (93%) subjects completed the 4-week assessment and 134 (89%) subjects completed the 3-month assessment. There were no statistically significant or clinically important between-group differences for the primary outcomes. CONCLUSIONS: The addition of passive stretching confers no benefit over exercise alone for the treatment of plantarflexion contracture after cast immobilization for ankle fracture.

Adult↗