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At least 595 records · Page 33Linked to original sources
PubMed2001

[Transverse deflection study of casted titanium zirconium alloy for dental clinic use].

OBJECTIVE: The aim of this study was to obtain the reasonable thickness of Ti-Zr alloy used for denture base material. METHODS: According to the "Revised ADA Specification No. 12 for denture base polymers", the transverse deflection tests of Ti-Zr alloy after casting were performed. Pure titanium, Ti-6Al-4V alloy and Co-Cr alloy were examined as the control. Three groups of wax patterns with different thickness were designed. Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy were casted into molds at 300 degrees C, which were made of zircon (ZrO2.SiO2) investment, using a casting machine (China), with a program of vacuum, pressure and centrifuge casting. Co-Cr alloy was casted by normal method in clinic. The transverse deflections of these four alloys castings with three different thicknesses were measured using a transverse testing machine. RESULTS: When the thickness is 0.65 mm for Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy, and 0.57 mm for Co-Cr alloy, the transverse deflections could satisfy the requirement. CONCLUSION: The transverse deflection is one of the key indexes for evaluating the ability of dental material to bear biting forces. The reasonable thickness of Ti-Zr alloy used as denture base material is 0.65 mm.

Dental Alloys↗
PubMed1992

An improved method for preparing microvascular corrosion casts of rat embryos.

This paper presents an improved method for preparing microvascular corrosion casts of rat embryos (day 16.5-21.5). Special attention was paid on the viscosity of the casting material, the method of mechanical restraint, and the subsequent drying of the casts. The embryos were perfused with Mercox resin diluted with 25% methyl methacrylate monomer followed by undiluted Mercox resin to avoid outflow of resin from the vasculature after perfusion. The specimens were mounted on a stainless steel plate with self-curing resin to prevent flotation, mechanical damage, and collapse of the cast specimens following preparation. After digestion and washing, the cast specimens were freeze dried to prevent deformation of the casts. This specimen preparation resulted in much better scanning electron microscopic images of the embryonic microvasculature of various oral tissues, free from leakage and insufficient filling.

Animals↗
PubMed2004

[The effect of casting techniques on the accuracy of titanium crown and bridge].

OBJECTIVE: To investigate the method of enhancing the accuracy of titanium crowns by improving the casting method. METHODS: A self-assembled die was used to fabricate 48 standardized wax crowns. The dies were averagely divided into two groups. 21 crowns were successfully fabricated from one group according to the improved techniques. 18 crowns were fabricated by traditional method. A reference mark was scribed 90 degrees apart at four sites on the margin of each wax pattern and respective die. The distance between the margins of the wax pattern and the die was measured under a stereomicroscope. Similar method was also applied to measure the margin of castings. The castings were longitudinally split through midline. The distance between the 4 points(B',C',D',E') selected in the inner part of the crown and the die was respectively examined. RESULTS: Castings acquired by the improved method were more complete and had smoother surface. Marginal discrepancy value had significant difference between the two groups. Value in experimental group was smaller. Distance from B',E' to die between the two groups had no significant difference, but the distance from C',D' to the die was significantly different. The experimental group was smaller. CONCLUSION: Standardized crowns fabricated by the improved titanium casting technique were more accurate, but special investment for titanium crowns and bridges should be developed to compensate the casting shrinkage of metal.

Crowns↗
PubMed2006

Functional cast bracing in the management of open forearm fractures: a preliminary report.

BACKGROUND: Management of any injury is expensive to the individual and the community. For this reason modification of methods of managing trauma very often is necessary in resource poor countries. OBJECTIVE: To verify the effectiveness of metal hinge joints in prevention of contractures and ankylosis of the elbow joint in cast immobilisation of reduced open forearm fractures. PATIENTS: 20 patients who had sideswipe injuries were managed from the year 01/01/2000 to date (20/5/2004) by the orthopaedic unit of Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria. They were referred from General Hospitals and Rural/Primary Health centers in northwestern Nigeria. They were all males, between the third and fourth decades of life (mean age was 35.54+1.52years). METHODS: Management of these patients involved early anti tetanus prophylaxis, good wound hygiene, internal fixation of the reduced fractures with kirschner wires, cast immobilisation and incorporation of metal hinge joints at the elbow joint. Three days after surgery the casts were windowed and patients were discharged to continue wound dressing at the nearest Health Centres. The metal hinge joints permitted elbow joint movement throughout the period of immobilization. After 12.45+0.42 weeks (mean length of time of wound healing in these cases) casts and implants were removed. RESULTS: Active movement of the elbows was rated as very good (8 cases), good (6 cases) and fair (6 cases). Plain radiography of the forearms showed fifteen cases of union and five cases of nonunion of fractures. CONCLUSIONS: The outcome of treatment of these injuries discerns the effectiveness of functional cast bracing in the prevention of contractures and ankylosis of the elbow joint in cast immobilization of reduced open forearm fractures. The healed wounds made the skin safer for further management of the cases of nonunion.

Adult↗
PubMed1992

Peroneal nerve palsy after early cast application for femoral fractures in children.

The incidence and contributing factors associated with post-casting peroneal nerve palsy were examined in a series of 110 consecutive pediatric femoral shaft fractures treated with early hip spica cast application. Four patients with peroneal nerve palsy were identified. All four had 90 degrees/90 degrees casts placed and underwent cast wedging for alignment. All palsies resolved with immediate cast removal. Other treatment options for certain femur fractures with significant initial shortening should be considered. We advise pre- and post-cast neurologic examination and avoidance of forceful distraction. Fracture manipulation, through wedging, should be delayed.

Casts, Surgical↗
PubMed1991

Recurrence of neuropathic ulceration following healing in a total contact cast.

Total contact casting has been clearly shown to be an effective technique in the healing of diabetic neuropathic foot ulcerations. The purpose of this study was twofold: (1) to determine the rate of ulcer recurrence in a large population of patients whose ulcerations had healed in a total contact cast, and (2) to determine the reason for which ulcerations had recurred. A random sample of 102 patients was taken from a much larger population, all of whom had healed in a total contact cast. There were 54 men and 48 women, all of whom were diabetics, averaging 50.5 years of age. These patients had an average wound size of 2.6cm by 1.9cm prior to casting and an average healing time of 33.9 days. At the time the sample was drawn, it had been an average of 25 months since casting for this group. Twenty (19.6%) of the 102 patients had ulcer recurrences since initially healing in a cast. Causes of ulcer recurrence were failure to comply with follow-up foot-wear/foot-care protocol (n = 8), biomechanical faults (n = 5), osteophyte or bone fragment (n = 4), osteomyelitis (n = 5), and Charcot joint (n = 4). Some patients had multiple etiologies.

Adult↗
PubMedDate not supplied

Effectiveness of cast-joined Ni-Cr-Be structures.

This study tested the load transfer effectiveness of cast-joined structures under flexural loading conditions. Bars of Rexillium III alloy (Ni-Cr-Be) were tested under four-point bending conditions in an Instron testing machine. Six specimens were prepared for each of five interlocking designs. After wax elimination of the investment mold, new metal was cast into the central interlock area. Strain gauges were bonded across the interfaces between the as-cast and secondary cast structures on the bottom surface, and the specimens were loaded to failure in a four-point-bending fixture. Failure was assumed at a strain level of 0.1%, which corresponds to the tensile failure strain of feldspathic porcelain. Three as-cast bars were tested as controls. The average failure load of an interlock design used by Weiss and Munyon was significantly higher (P less than 0.05) than that of the remaining four designs but was significantly lower (P less than 0.05) than that of the solid bar. At the critical strain level of 0.1%, the load-transfer effectiveness of the Weiss and Munyon design was less than 22%. The results suggest that the cast-joining technique may increase the risk of failure in clinical situations where high flexural stresses exist.

Dental Alloys↗
PubMed1990

[Effect of casting techniques on castability of copper-aluminum alloys].

It was evaluated the castability of four copper-aluminium alloy according the melting casting method used. The specimens were made using polyester mesh screen, with 11 x 11 filaments of 0.26 mm thick, fixed along of two adjacent edges in wax bar, with the sprue attached at their junction. The alloys were in an electrical casting machine and a centrifugal casting machine with an air/gas torch. The castability values were obtained by the percentage of completed segments of the resulting cast alloy screen. It was verified that the use of the electrical casting machine produced higher castability values to the copper-aluminium alloys than those produced by a centrifugal casting machine with an air/gas torch.

Aluminum↗
PubMed1990

[Fatigue of retentive clasps of removable partial dentures. Effect of alloys, thickness and casting techniques. 2].

The authors tested the T clasp of Roach in three differents proportions among width and thickness: E1-1.7; E2-2.0 and E3-2.3, with a constant length of 15 mm. These clasps were casted with three cobalt-chromium alloys (L1-Biosil; L2-Steldent and L3-Duracrom), through two casting techniques (F1-oxygen-gas and F2-oxygen-acetylene). The fatigue of the clasps were verified by using and assay machine, that through movements, simulate the insertion and removal of the clasps for a pattern which were obtained from a premolar, prepared in a surveyor. This machine detect the fatigue of the clasps and count the number of cycles of insertion and removal realized. The obtained results of the interaction between the analysed factors, were submitted to the statistic analysis and the authors concluded that: a) the interaction of factors, Alloy x Thickness, Alloy x Casting Technique and Thickness x Casting Technique did not change the order of effects that the factors showed separately but gave rise to effects of different magnitude for any observed sense; b) the simultaneous interaction of the factors Alloy x Thickness x Casting Technique confirmed the superiority of the L3 alloy, the thickness E3 and the F2 casting technique.

Bicuspid↗
PubMed1979

[Oxygen contents and casting porosities in Ag alloys (author's transl)].

Although pure Ag has a large casting porosity near the sprue attachment, Ag-Zn and Ag-Cu alloys have small or no porosities. The casting porosities of Ag-Au alloys are similar to that of pure Ag. These experimental results were discussed using the calculated oxygen contents in molten state and the measured oxygen contents of castings, and related to the capacity for deoxidization of additive elements. In the present study the casting porosities in pure Ag and Ag-Au alloys are considered to be not shrinkage porosities, but porosities due to discharged oxygen gas. In spite of high oxygen contents of molten state and castings, the casting porosity was not observed in pure Cu. This may be due to the fact that the occluded oxygen atoms exist as copper oxide (Cu2O) in solid Cu.

Dental Alloys↗
PubMed1987

Improved treatment of femoral shaft fractures in children. The "pontoon" 90-90 spica cast.

In the past 15 to 20 years, little improvement has been made in the standard treatment of femur fractures in children. Children younger than two years of age or weighing less than 30 pounds are normally treated with skin traction or immobilized in a plaster cast or both. Older or heavier children are often treated with skeletal traction, followed by early or late application of spica cast in the neutral position. A method of spica cast treatment that immobilizes the limb in the 90-90 position using a reinforced cast incorporating a distal femoral traction pin--the pontoon spica--allows for early cast application and discharge from the hospital and encourages early motion of the knee joint. A series of 23 femur fractures in 21 patients were treated with this method. This series is compared with a series of 38 fractures treated with conventional methods. The follow-up period ranged from three to 24 months. The pontoon method provided better results in control of alignment than the conventional method, with no greater discrepancy in leg lengths than generally observed after skin traction and hip spica casts. The average hospital cost reduction was 73%, or approximately $13,334. There were no major complications with the pontoon method, which is now a standard treatment for femoral fractures in children.

Casts, Surgical↗
PubMed1982

Setting temperatures of plaster casts. The influence of technical variables.

It is known that plaster-of-Paris casts can cause burns. Experiments were done to determine what factors are involved in causing an elevation of the temperature in a freshly applied cast. A glass tube filled with water between the temperatures of 36 and 39 degrees Celsius was used to simulate a leg for this study. Standard plaster casts were applied to the tube and the following variables were studied: different temperatures of the dip water; different thicknesses of the cast; the presence of plaster residue in the dip water; and the effect of the plaster of a pillow placed under the tube. It was found that if the temperature of the dip water was higher than 24 degrees Celsius or the thickness of the cast was greater than eight ply, or both, and if the pillow was used to limit the dissipation of heat from the cast, temperatures high enough to cause skin burns could occasionally be reached. Variable results indicated that these were the factors operating in practice and that a combination of them posed the greatest hazard.

Burns↗
PubMedDate not supplied

The plaster slipper cast.

Since cast correction of congenital metatarsus adductus requires purchase of the cast on the foot only, a plastic slipper cast can accomplish this task. The correction of deformity and retainability equals or exceeds that of the short-leg cast. Ease of application and removal make this cast quite attractive in the small child. The use of this cast can be extrapolated to many conditions.

Casts, Surgical↗
PubMed1976

[Slip casting of stainless steel powder (author's transl)].

Slip casting of stainless steel powder (AISI type 316 L) was investigated as means of forming medical and dental porous restorations. This research was undertaken to evaluate the effects of the particle size and aging of casting slip and firing conditions. Bulk density was used as a measure of the degree of sintering. Water contents of casting bodies decreased with the particle size and its casting rates, bulk densities and bending strengths increased. Aging of slip decreased casting rates, water contents and bending strengths of the casts. The bulk densities of the sintered stainless steel increased with sintering time and temperature. The porosities of the materials decreased with the particle size and the elevating temperature. The bending strengths of the materials increased sharply with the decreasing particle size. The optical micrographs did not always show the uniform elimination of pores in the sintered. Aging of slip increased a little the bulk densities of the materials and decreased the porosity and the bending strength.

Dental Casting Technique↗
PubMed1994

A technique for developing a master cast with previously made dies.

This article describes a technique for preparing final working casts to be used in the laboratory phase of restorative treatment. The goal is to produce accurate working casts that have stable dies which are easily removed from the base and reliably replaced. Most casts with removable dies are made from a single master impression. However, individual dies are sometimes made previously from individual tooth (preparation) impressions. In such cases, transfer copings are required to relate the dies and produce the final working cast. Hollow plastic casting sprues are used as temporary dowels in this technique until a transfer coping pickup impression has been made. After the dies are seated and secured in the transfer coping pickup impression, the plastic casting sprues are replaced with conventional brass dowel pins. This technique ensures well-placed dowel pins that will facilitate easy and accurate withdrawal and replacement of the dies.

Dental Casting Technique↗
PubMedDate not supplied

New high-palladium casting alloys: Part 2. Effects of heat treatment and burnout temperature.

Castings simulating a maxillary central incisor coping were fabricated from five representative high-palladium alloys, using burnout temperatures of 1,400 degrees F and 1,500 degrees F, with a carbon-free phosphate-bonded investment. Three castings of each alloy were individually prepared at each burnout temperature. Each casting was sectioned into two specimens, and one specimen was subjected to simulated porcelain firing heat treatment. Polished and etched specimens in as-cast and heat-treated conditions were examined with optical and scanning electron microscopes. Mean values of Vickers hardness (1-kg load) were determined for each alloy and condition. It was observed that the simulated porcelain firing cycles caused major changes in as-cast bulk microstructures for the three first-generation alloys, while only subtle alterations were observed for the two second-generation alloys. In addition, complex regions associated with oxidation processes were found near the surfaces of all the heat-treated alloys. While the as-cast microstructure and the hardness of each alloy did not vary appreciably for the two burnout temperatures, the incidence of hot tearing in one first-generation alloy was substantially reduced at the lower burnout temperature. Statistically significant decreases in hardness generally occurred in the high-palladium alloys after the simulated porcelain firing cycles, but the relatively small changes (usually 10% or less) should not have any clinical significance. Other clinically relevant applications are also discussed.

Dental Alloys↗
PubMed1995

Plantar pressures with total contact casting.

Total contact casting has been used to aid in the healing of plantar neurotrophic ulcerations. The efficacy of total contact casts in promoting ulcer healing is presumably due to a reduction in the load over high pressure areas with pressure redistribution over the entire surface of the foot. The purpose of this study was to quantify the effectiveness of total contact casting in reducing plantar pressures. A portable microprocessor-based data-acquisition system was used for recording plantar pressures. Plantar pressures were collected from six nondisabled individuals with and without total contact casting at cast-walking cadence. In our study, there was a decrease in plantar loading under the metatarsal heads (first, fourth, fifth), the great toe, and the heel. The average decrease was 32% under the fifth metatarsal, 63% under the fourth metatarsal, 69% under the first metatarsal, 65% under the great toe, and 45% under the heel. Our study quantitatively showed that total contact casting does reduce vertical plantar pressures in high load areas.

Adolescent↗
PubMed1996

Casting methods of scanning electron microscopy applied to hemal lymph nodes in rats.

Hemal lymph nodes of the para-aortic group in rats were examined by scanning electron microscopy (SEM) using the corrosion cast technique. The vasoarchitecture of hemal lymph nodes was described in cast specimens filled from the abdominal aorta. A dense system of capillaries arranged in the mode of a meshwork could be represented in the nodal cortex. The postcapillary venule (PCV) with wide vascular lumina provided the prevailing vessel type of the deep cortex. Sphincter-like narrowings of the capillary lumen appeared at the sites where capillaries merged with the PCV. These vascular segments were interpreted as structures controlling the hemodynamics of the joining PCV thereby providing appropriate conditions for homing lymphocytes. No evidence was obtained from the casts for an open circulation in hemal lymph nodes. The intranodal lymphatic pathways were studied in specimens interstitially injected with resin. The fine lymphoid tissue spaces were characterized by special cast patterns reflecting the structural differentiation of certain nodal compartments. Afferent lymphatics could be clearly identified in casts with a retrograde filling from the subcapsular sinus. Very spacious intermediary sinuses and wide meshed medullary sinuses could be represented in those casts as well, thus allowing ample space for the encounter of large macrophages with red blood cells.

Animals↗