Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CASTS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1978

[Relationship between mechanical properties and amounts of casting porosities in tensile-test fracture surface of Au-Pd-Ag-Cu alloy (author's transl)].

One hundred and thirty-nine tensile-test specimens of Au-Pd-Ag-Cu alloy were cast in various casting conditions. The specimens were subjected age-hardening heat-treatment. The casting porosities and the nonmetallic inclusions in the surface of a tensile-test fracture of cast specimens were observed and analyzed by use of Electron Probe X-ray Microanalyzer (EPMA). The polosity ratio that is the area ratio of the porosities to the fracture surface was determined. Studies were quantitatively made on the effect of the porosity ratio on the tensile strength and the elongation. Furthermore, the effect of the casting conditions on the tensile strength was investigated. The main results were summarized as follows; The tensile strength decreased only slightly within about 15% of the porosity ratio and remarkably with an increase in its ratio in the range from about 15% to 50%. The elongation, however, decreased considerably in the presence of the porosities of only a few per cent. Aspects of the decrease curves on the tensile strength and the elongation were represented in the shape of an inverse S-type and hyperbolic curve with an increase in the porosity ratio, respectively. With an increase in the porosity ratio, the shapes of the tensile-test specimens at the fracture part and load-elongation curves in the tensile-tests were shown as a brittle fracture. However, the result observed by a scanning electron microscope revealed that the fracture surfaces without the porosities showed mostly "dimple pattern" suggesting a characteristic figure of a ductile fracture. The nonmetallic inclusions in the fracture surfaces were identified as SiO2 (quartz) which was derived from an ingredient of an investment by comparing the inclusion with the reference standards on the characteristic X-ray O Kalpha spectra by EPMA. The microstructures observed by a light microscope showed a coarse structure with the high temperature casting conditions. However, the results of a scanning electronmicroscopy revealed that the microstructres observed in high magnifications of about 1000 to 3000 composed of two structures; micro-lamella and Widmanstätten structure, and no difference was shown in the various casting conditions. Therefore, it is concluded in the present alloy that a coarseness of the microstructures observed by a light microscope become no reason for a decrease of the tensile strength.

Copper↗
PubMed1985

Casting accuracy of a nickel and beryllium-free cobalt-chromium alloy for crown and bridge prostheses and resin-bonded bridges.

In the 1970's economic factors dictated the development of alternatives to gold alloys in dentistry in the USA and in Europe. A similar development has not occurred in Sweden because of different laws. Alloys that contain nickel and beryllium present a health hazard and are therefore of little interest to the Swedish market. A review of the literature shows that castings of base-metal alloys are less accurate than castings of conventional gold alloys and of low gold alloys. However, in long-span-bridges and in thin resin-bonded cast restorations, their physical and mechanical properties are superior to those of the gold alloys. In this study the casting accuracy of a nickel- and beryllium-free cobalt-chromium alloy, Neobond II Special, is investigated. Neobond II Special was found to be less accurate than Sjödings C-guld. The marginal discrepancies of the castings were small, however, when the castings were oversized. It also proved to be technique sensitive to conventional dental laboratory procedures. Thus, it seems difficult to get castings with an acceptable retention as well as small marginal discrepancies when using the base-metal alloy.

Chemical Phenomena↗
PubMed1981

Quantification of intracompartmental pressure and volume under plaster casts.

UNLABELLED: Infusion lines (to elevate intracompartmental pressure experimentally) and wick catheters (to monitor the pressure produced) were inserted into hind-limb muscle compartments in twenty-six dogs. A padded plaster cast was then applied. The effect of the cast on intracompartmental pressure and volume and the effect of first splitting the cast and then cutting the padding were determined. Three different padding were used: dry Webril, Webril soaked in blood and Betadine (povidone-iodine), and Webril soaked in blood and Betadine and then dried. The cast was found to restrict expansion of the compartment volume by approximately 40 per cent. The most significant reductions in pressure in all groups occurred after the cast was cut and spread (mean reduction, 65 per cent). An additional pressure reduction of 10 to 20 per cent occurred after cutting the Webril. After removal of the cast, all limbs maintained some residual elevation of the intracompartmental pressure. CLINICAL RELEVANCE: This study demonstrates the need in clinical practice for continued evaluation and monitoring of a limb even after the cast has been completely removed because of signs and symptoms of a compartmental syndrome.

Animals↗
PubMed1994

[Comparative studies of synthetic and nonsynthetic cast dressings].

Six different cast materials were evaluated and compared for radiolucency and mechanical properties. Synthetic casts, that do not contain fiberglass are more radiolucent than fiberglass cast materials or plaster of Paris. The fiberglass cast is particularly stable, and the advantage of the cotton cast is a low dead weight. The costs of synthetic casts made according to the producer manufacturers' recommendations do not differ significantly, but they are all much more expensive than plaster of Paris. Splitting a synthetic cast along its length and bending it open is not enough to prevent compartment syndrome, and wedging is recommended to keep it open.

Absorptiometry, Photon↗
PubMed2005

Novel method for titanium crown casting using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded investment.

OBJECTIVES: For titanium casting, most commercial investments for titanium recommend casting at a low mold temperature to reduce oxidation. However, the thermal expansion values of the molds at low casting temperatures may be insufficient. The purpose of the current study was to investigate the possibility of obtaining accurate titanium crown casts using wax pattern fabricated by a CAD/CAM system with a non-expanded mold. METHODS: Three types of experimental magnesia-based investments (A, B and C) were made and their properties were evaluated for dental use. Two kinds of wax patterns for full-coverage coping crowns (S-0: cement space of 0 microm; S-20: cement space of 20 microm) were fabricated using a commercial CAD/CAM system. A traditional method (TM) using inlay wax was performed for comparison. The investment for titanium casting was decided from the fundamental data of experimental investments. Titanium crowns were replaced on the stone die and the thickness of the cement layer was evaluated. RESULTS: There were no significant differences for the setting time and setting expansion among the experimental investments, but the aluminous cement content played a role in hardening and contracting the mold. The fit of the titanium crowns differed significantly between the TM and the CAD/CAM system. The ranges of thickness obtained from the TM, S-0 and S-20 were 20.78-357.88 microm, 25.12-107.46 microm and 17.84-58.92 microm, respectively. SIGNIFICANCE: High quality titanium crown casting was obtained using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded MgO-based investment.

Analysis of Variance↗
PubMed2000

A human skull cast model for training of intracranial microneurosurgical skills.

Skillful microsurgical techniques such as microvascular anastomosis and repair of nerves require dedicated and extensive laboratory training. Human microneurosurgery poses several additional technical difficulties, as the intracranial procedures are often performed through a narrow operative space at a considerable length, using knee-bend instruments. This article presents a laboratory model to simulate microneurosurgical procedures in humans. A human skull cast model made from plaster is cut such that, when placed on a operating table, it represents a standard position of a pterional approach and that the point of operation is at the same depth as the hypothetical circle of Willis. A standard pterional opening is made in de skull cast and the model is placed over the rat. Subsequently, all surgical procedures starting from tissue preparation to performing an arterial, venous, and/or nerve repair are performed with the cast over the rat using microneurosurgical knee-bent instruments and a surgical microscope. Microsurgical procedures such as end-to-end vessel anastomosis and nerve repair are technically much more challenging and difficult to execute when performed through the pterional opening of the human skull cast than without the cast model. Moreover, the cast model useful in training microsurgical techniques performed with long knee-bend instruments. It is concluded that the skull cast model represents a useful method to train intracranial microneurosurgical blood vessel anastomosis and nerve repair.

Humans↗
PubMed1984

Development of the vascular bed in the rabbit ear: scanning electron microscopy of vascular corrosion casts.

The development of the vascular bed in the rabbit ear was investigated using vascular corrosion casts from animals of various ages. Examination of the casts revealed that the arrangement of the major auricular arteries and veins was determined before birth and was maintained during postnatal growth of the ear. Furthermore, the number of arteries branching off the central ear artery and the lateral arteries did not increase with increasing ear length. Scanning electron microscopic examination of lateral segments of adult ear casts revealed many anastomoses between marginal arteries and veins. These arteriovenous anastomoses (AVAs) occurred singly, in pairs, or in clusters of three to six. Their size and shape were variable, even in the same cast. The central segment of many AVA casts showed surface impressions of endothelial cell nuclei which were different from the impressions on adjacent arteries and veins. Arteriovenous anastomoses were also detected in ear casts from animals as young as 8 days. The density of AVAs in lateral ear segments ranged from 95-165 cm-2 in 8- to 11-day-old rabbits to 80-115 cm-2 in adults. However, estimates of the total number of AVAs in the lateral ear margin indicated that AVAs continued to be formed at a steady rate during growth of the ear. During the early neonatal period the cutaneous capillary plexuses developed prominent tufts projecting toward the skin surface, which were apparently associated with developing hair follicles. These capillary tufts were not seen in casts from fetal or adult rabbits.

Animals↗
PubMed1988

Nuclear magnetic resonance study of an ethyl cellulose sustained-release delivery system. I: Effect of casting solvent on hydration properties.

This study was conducted in order to explore the proton relaxation time and the structural features of films that are cast from different solvents and to be used as sustained-release delivery systems. Protons magnetic resonance measurements were performed on ethyl cellulose (EC) films cast from ethanol or chloroform solutions in the presence of polyethyleneglycol (PEG). Spin-lattice relaxation time (T1) was measured with a Bruker PC-20 Multispec, at 20 MHz and at 37 degrees C, on the dry films and thereafter during gradual, controlled hydration. The prolongation of the rate of relaxation time for the films cast from ethanol and chloroform solutions was found to be drastically different. Water compartmentalization was then calculated according to the Free Induction Decay model. After the addition of similar amounts of water, markedly different hydration fraction (HF) values were derived for the films cast from the different solutions as a function of the amount of embedded PEG. Scanning electron micrographs confirmed that the two types of systems have different film structures that are dictated by the casting solvent and the amount of embedded PEG. From these results it can be concluded that in the presence of PEG, EC films cast from ethanol have more water binding sites and a thicker water multilayer around them than films cast from chloroform. These properties might influence the release rate of an active agent from the sustained-release device.

Cellulose↗
PubMed1994

Spontaneous passage of a colon cast in the absence of abdominal aneurysm.

The spontaneous passage of colon cast from a 76-year-old Japanese female patient is reported. Macroscopically, the colon case was shaped like the airbladder of a fish. Histopathologically, the cast consisted of degenerated colonal mucosa, including glands. No inflammatory reaction was apparent. The patient lacked any evidence of abdominal aneurysm. Since there have been only five reported cases of colon cast in the literature, and since in all of those association with abdominal aneurysms was always described, the present study represents the first report demonstrating the formation of a colon cast in the absence of associated abdominal aneurysm. However, the patient was found to exhibit several risk factors for ischemic colitis, such as arteriosclerosis on the wall of the abdominal aorta, chronic constipation, and colonic stenosis. Her colonal mucosal surface, indeed, suggested ischemic colitis. This case report, therefore, indicates that ischemic colitis, due to various causes, may be responsible for the formation of colon casts, and that the presence of an abdominal aneurysm is not necessarily a prerequisite for colon cast formation. This report may contribute to a better understanding of the pathogenesis of colon casts.

Aged↗
PubMed2001

Two- or three-dimensional cast analysis in patients with cleft lip and palate?

AIM: The aim of the present study was to evaluate different two- and three-dimensional cast analyses for the assessment of maxillary dimensions in patients with complete unilateral cleft lip and palate, using a set of representative cast series. PATIENTS AND METHOD: Consecutive casts were taken from ten patients at 1 week, and at 3, 6, and 12 months, respectively. First, cast surfaces were digitized two-dimensionally using a scanner. Subsequently, landmarks were identified on screen and the previously defined maxillary dimensions were determined automatically by computer. Additionally, three-dimensional measurements were carried out using a specialized coordinate measurement table. The differences between the respective measurements were analyzed for statistical significance. RESULTS: The present study shows that the precision of the cast analysis is influenced above all by the quality of the casts and less by the precision of the measuring system employed. Moreover, misinterpretation of the results can be attributed to using an inappropriate reference system or to considering mean values only. When assessing linear and angular measurements located in approximately the same plane, no significant amount of additional information could be obtained by including the third dimension. CONCLUSION: Thus, two-dimensional measurement procedures are appropriate in principle for quick, reliable cast analysis in patients with cleft lip and palate.

Cephalometry↗
PubMed2006

Y-chromosomal insights into the genetic impact of the caste system in India.

The caste system has persisted in Indian Hindu society for around 3,500 years. Like the Y chromosome, caste is defined at birth, and males cannot change their caste. In order to investigate the genetic consequences of this system, we have analysed male-lineage variation in a sample of 227 Indian men of known caste, 141 from the Jaunpur district of Uttar Pradesh and 86 from the rest of India. We typed 131 Y-chromosomal binary markers and 16 microsatellites. We find striking evidence for male substructure: in particular, Brahmins and Kshatriyas (but not other castes) from Jaunpur each show low diversity and the predominance of a single distinct cluster of haplotypes. These findings confirm the genetic isolation and drift within the Jaunpur upper castes, which are likely to result from founder effects and social factors. In the other castes, there may be either larger effective population sizes, or less strict isolation, or both.

Chromosomes, Human, Y↗
PubMed1990

Occlusal accuracy of casts made and articulated differently.

This study evaluated the occlusal accuracy of gypsum casts constructed from irreversible hydrocolloid and selected nonaqueous elastomeric materials. Master metal casts were attached to a vertically moving apparatus that allowed their occlusal surfaces to produce repeatable contacts. Impressions were made with irreversible hydrocolloid, polysulfide, and vinylsiloxane. Resulting maxillary casts were mounted with a constant positioning device and mandibular casts were mounted with zinc oxide-eugenol paste records or by maximum intercuspation. Four specific master occlusal contacts were compared with contacts generated from the mounted gypsum casts; a perfect score was 40 (four contacts x 10 casts). A chi-square linear model for category data was used to compare groups. Results indicated that casts made from irreversible hydrocolloid should not be articulated with the use of a zinc oxide-eugenol paste but are best articulated by using maximum intercuspation (32/40 contacts).

Chi-Square Distribution↗
PubMed1988

Capillary configuration and fiber shortening in muscles of the rat hindlimb: correlation between corrosion casts and stereological measurements.

It has been a matter of discussion whether the dramatic increase in capillary tortuosity visualized in shortened muscles by vascular cast represents in vivo situations. In this study, we combined vascular cast and stereological methods in the same samples, in order to obtain (1) measurements of sarcomere length in the same muscles from which corrosion casts were prepared, and (2) scanning electron micrographs of the three-dimensional arrangement of capillaries in the same muscles where capillary anisotrophy was estimated by morphometry. Various rat skeletal muscles (soleus, gastrocnemius, and gracilis) were examined at lengths ranging from full shortening to full extension. We found a very good correlation between capillary geometry in material prepared for vascular casts and in muscles perfusion-fixed in situ. All muscles, cast and noncast, showed the same progressive curvilinear decrease in capillary anisotropy with decreasing sarcomere length. Capillary tortuosity visualized by corrosion casts in shortened muscles is a consequence of fiber shortening, within physiological sarcomere lengths; it does not represent an artifact related to the casting procedure.

Animals↗
PubMed1992

Enrollment in clinical trials: institutional factors affecting enrollment in the cardiac arrhythmia suppression trial (CAST).

Recruitment and Enrollment Assessment in Clinical Trials (REACT), an NHLBI-sponsored substudy of the Cardiac Arrhythmia Suppression Trial (CAST), was conducted to assess factors associated with enrollment in clinical trials. We report on the relationships of institutional factors at CAST sites to patient enrollment. The proportion of CAST-eligible patients enrolling at each CAST site during the REACT study period was defined as the number of subjects enrolled divided by the sum of (1) the number enrolled plus (2) the number of eligibles who refused plus (3) the number of eligibles whose physicians refused to permit CAST personnel to attempt to enroll them. A questionnaire that included 78 questions regarding factors hypothesized to be associated with enrollment was completed between August 1988 and February 1990 by the nurse coordinators at all 112 CAST sites in the United States and Canada. Sixteen items were unanalyzable, and 37 of the remaining 62 were grouped into seven scales. The remaining items were analyzed individually. Enrollment proportions varied widely across the 112 CAST sites (mean 32.7% SD 22.6). Five variables or scales were included in the final multiple regression model (multiple R2 = .39). The most important of these was the proportion of eligible patients at a site cared for by medical staff other than private attending physicians (multiple R2 for this variable alone, .26). This proportion tended to be high in teaching hospitals. Other variables in this model that were associated with higher enrollment proportions included the number of days per week a nurse coordinator was present at the site, the number of nurse coordinator full-time equivalents at the site, fewer other clinical trials for which the nurse coordinator was responsible, and fewer perceived obstacles to enrollment. These findings indicate that enrollment was more successful at hospitals with higher proportions of eligible subjects cared for by fellows, housestaff, and service attending physicians and at institutions with the committed presence of a nurse-coordinator.

Arrhythmias, Cardiac↗
PubMed2004

Geographic variation of caste structure among ant populations.

Morphologically distinct worker castes of eusocial insects specialize in different tasks. The relative proportions of these castes and their body sizes represent the demography of a colony that is predicted to vary adaptively with environments. Despite strong theoretical foundations, there has been little empirical evidence for the evolution of colony demography in nature. We show that geographically distinct populations of the ant Pheidole morrisi differ in worker caste ratios and worker body sizes in a manner consistent with microevolutionary divergence. We further show that the developmental mechanism for caste determination accounts for the unique pattern of covariation observed in these two traits. Behavioral data reveal that the frequency of different tasks performed by workers changes in a caste-specific manner when caste ratios are altered and demonstrate the importance of the major caste in colony defense. The population-level variation documented here for P. morrisi colonies supports the predictions of adaptive demography theory and illustrates that developmental mechanisms can play a significant role in shaping the evolution of phenotype at the colony level.

Adaptation, Biological↗
PubMed2004

A variation on split-cast mounting for complete denture construction.

This article describes a variation of the split-cast mounting technique wherein the border of the definitive cast is wrapped with masking tape to form a container for the dental plaster normally used to affix the cast to the articulator. The entire inferior surface of the cast is coated with a thin film of petroleum jelly, and the cast is mounted in the articulator. After the dental plaster has set, the cast is retained by means of the masking tape. The cast is separated from the dental plaster simply by removing the masking tape.

Adhesives↗
PubMed2000

In vitro comparison of master cast accuracy for single-tooth implant replacement.

STATEMENT OF PROBLEM: The inaccuracy in transferring the position of the hexagonal head of a single implant to the working cast can result in a final single tooth crown, which clinically may present occlusal and/or interproximal contacts that are different from those contacts on the master cast obtained by the technician. PURPOSE: This in vitro study evaluated the accuracy of the master casts obtained using square pick-up impression copings for single-tooth replacement. Copings used were (1) copings as sold by the manufacturer, and (2) copings modified by sandblasting and coating with impression adhesive their roughened surfaces before final impression procedures. MATERIAL AND METHODS: A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using nonmodified impression copings; a second group of 20 impressions were fabricated with modified copings. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. RESULTS: The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained with the modified impression copings than in the master casts achieved with the nonprepared copings. CONCLUSION: Improved precision of the impression was achieved when the adhesive-coated copings were used.

Adhesives↗
PubMed1998

A method for the measurement of three-dimensional geometry of casts used for the manufacture of ankle foot orthoses.

OBJECTIVE: To develop a method to measure the geometry of casts for the manufacture of ankle foot orthosis. DESIGN: A measurement study in which the feasibility of the technique, and its reliability were studied, using statistics based upon the analysis of variance. BACKGROUND: Studies have shown that the effectiveness of ankle foot orthoses is influenced by small changes in geometry and, particularly, by the amount of dorsiflexion. This study is concerned with a technique to identify the variations between nominally identical casts. METHODS: A measuring technique was used to determine the coordinates of grids drawn on the surface of the casts. Repeatability studies involved the measurement of six casts of the same leg produced by one orthotist. The influence of rectification, in which the technician makes modification prior to moulding, was also studied. RESULTS: The measurement technique was reliable, and there were no significant differences in grid dimensions among the casts. There were significant differences in dorsiflexion (up to 11 degrees) which were not influenced by rectification. CONCLUSIONS: This technique has been shown to be suitable to study the geometry of casts for the manufacture of ankle foot orthoses, and has demonstrated that relatively large variations may occur between nominally identical casts. There is a need to apply this procedure to study the influence of orthotic technique on geometry and function. RELEVANCE: AFO's are prescribed for patients with neurological disabilities. Since it is known that a correctly manufactured orthosis can achieve significant improvements in gait, it is necessary to quantify manufacturing accuracy.

Journal Article↗