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PubMed1991

[Prolongation of the CAST study.Is it justified to consider another trial?].

A possible prolongation of the CAST would be another trial of the same type, (CAST II), designed for high risk patients (1 year mortality over 20%). The aim of this study would be to confirm the hypothesis that the ratio efficacy/undesirable side effects of antiarrhythmic drugs is beneficial in this type of patient. The most important selection criteria would be an ejection fraction of less than 40%, the presence of repetitive arrhythmias, especially ventricular tachycardia on Holter monitoring and the recording of late ventricular potentials on surface averaging ECG. The patients would be included at about the 20th day after myocardial infarction in order to exclude as much as possible unstable coronary artery disease and ventricular arrhythmias on successive Holter recordings because this would make interpretation of the efficacy of antiarrhythmic drugs impossible. The ideal number of patients would be about 5,000 but this is unrealistic because the trial would only include high risk cases and there would be difficulties in recruiting this number even in a multicenter trial. During follow-up of 2 to 3 years, the surveillance of the therapeutic efficacy of the antiarrhythmics would have to be better than in the CAST. The most delicate methodological problem would be the randomization of patients as the formation of a placebo group is unethical in high risk coronary patients with severe or malignant ventricular arrhythmias. The use of the only proved cardioprotector drugs, the betablockers, in all these high risk patients would be one solution, even if it might introduce a bias in the results.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed2006

[Influence of different convergence angles on the retention of cast metal post and core].

Fifty-four simulated tooth roots made of polymethacrylate (PMMA) were divided into six groups according to the root canal convergence angles of 0 degrees, 3.93 degrees, 5.71 degrees, 7.48 degrees, 11.31 degrees, 14.71 degrees. Cast post and cores were manufactured and cemented with Zinc phosphate cement (ZP). The retention capacities of the posts were tested. The bonding strength of ZP at different convergence angles were tested with some casted wafers, and linear regression was made. So the effect of interlocking and the proportion could be calculated. With these results, we made some curvilinear regressions. The results showed that the retention of cast post declined and the bonding strength of ZP fell with the increase of convergence angles. There were significant differences in the bonding strength and retention among groups, P<0.05. The experiment indicates that the dentists should reduce the convergence angles of posts as much as possible to obtain greater retention.

Cementation↗
PubMed2006

Effects of advanced oxidation on green sand properties via iron casting into green sand molds.

The effects of advanced oxidation (AO) processing on the properties of green sand were studied via pouring cast iron into green sand molds. Upon cooling, the green sand molds were autopsied at various distances from the metal-sand interface. Autopsy green sand samples collected from a mold that incorporated AO water were characterized and compared to controlled samples collected from a similar autopsied mold made with conventional tap water (TAP). It was found that the AO processing removed a coating of coal pyrolysis products from the clay surface that typically accumulated on the clay surface. As a result, the AO-conditioned green sand retained 10-15% more active clay as measured bythe standard ultrasonic methylene blue titration than did the TAP-conditioned green sand. The AO processing also nearly doubled the generation of activated carbon from the normalized amount of coal composition of the green sand during the casting process. The AO-enhanced activated carbon generation and the AO-incurred clay surface cleaning provided the AO-conditioned green sand with higher normalized pore volume, and thus higher normalized m-xylene adsorption capacity, i.e., relative to before-metal-pouring conditions. Furthermore, mathematical analysis indicated that the AO-conditioned green sand better retained its important properties after pouring than did the TAP-conditioned green sand. Effectively, this meant after metal pouring, the AO-conditioned sample offered about the same net properties as the TAP-conditioned sample, even though the AO-conditioned sample contained less clay and coal before metal pouring. These results conformed to the full-scale foundry empirical finding that when AO is used, foundries need less makeup clay and coal addition through each casting cycle, and they release less air emissions.

Air Pollutants↗
PubMed2006

[An improved fast algorithm for ray casting volume rendering of medical images].

Ray casting algorithm can obtain better quality images in volume rendering, however, it presents some problems such as powerful computing capacity and slow rendering velocity. Therefore, a new fast algorithm of ray casting volume rendering is proposed in this paper. This algorithm reduces matrix computation by the matrix transformation characteristics of re-sampling points in two coordinate system, so re-sampled computational process is accelerated. By extending the Bresenham algorithm to three dimension and utilizing boundary box technique, this algorithm avoids the sampling in empty voxel and greatly improves the efficiency of ray casting. The experiment results show that the improved acceleration algorithm can produce the required quality images, at the same time reduces the total operations remarkably, and speeds up the volume rendering.

Algorithms↗
PubMedDate not supplied

Gene differentiation at the ABO locus among six castes of Shudras, Andhra Pradesh, India.

Gene differentiation in the ABO system of six caste groups of the Shudra community was studied in the Visakhapatnam District, Andhra Pradesh, India. The results suggest that only a small fraction of gene diversity (0.50%) is attributable to between caste groups; in other words 99.50% of the gene diversity exists within the castes of Shudras.

ABO Blood-Group System↗
PubMed1991

A clinical technique for bonding gold castings to teeth.

A clinical technique is presented that allows practitioners to use adhesive bonding techniques to improve the retention and seal of gold castings. At the time of delivery of a gold casting, the preparation is treated with a self-curing enamel and dentinal bonding agent. The internal surface of the casting is sandblasted and electroplated with tin to produce a surface suitable for bonding with a resin cement, which is virtually insoluble and is adhesive to both the metal surface and the treated tooth.

Acrylic Resins↗
PubMed1991

[The effect of the working conditions on the development of diseases in cast-iron welders].

It was established that during cast-iron welding unfavourable factors of this production are welding aerosols, thermal and physical loads, radiation of the optical range. Results of detailed medical screening evidence that 80% of cast-iron welders showed pathology of the internal organs. Diseases of the bronchopulmonary apparatus occupy the leading place and are registered in every second cast-iron welder. The incidence rises with increased length of work and age.

Humans↗
PubMed1990

The accuracy of implant master casts constructed from transfer impressions.

The accuracy of master casts fabricated from three impression techniques commonly used with the Brånemark System was measured. Points placed in a metal surrogate model and onto master abutments were compared after abutments were transferred to stone casts using splinted and unsplinted impression coping techniques. The mean values and standard deviations of each of the reference points on 12 total casts were compared with the values for each point from the surrogate model. Values from techniques using splinted and unsplinted squared polymer copings as well as unsplinted tapered hydrocolloid copings were not significantly different from values recorded from the master surrogate model. Tapered hydrocolloid copings yielded a higher correlation to coordinate values on the master than unsplinted squared polymer copings or splinted squared copings.

Acrylic Resins↗
PubMed1990

[Analysis of stresses in modified resin-bonded cast fixed partial dentures].

In 1973, ROCHETTE introduced a periodontal splinting method that involved bonding of cast perforated retainers to the acid etched lingual surfaces of anterior teeth, using a resin. Nowadays, there have been a number of reports on the clinical performance of the adhesive bridges. The objective of this investigation was to photoelastically evaluate the forces exerted on the supporting structures of abutment teeth by modified resin-bonded cast fixed partial dentures. Four modified designs were tested and a traditional fixed bridge used as a control design. This study indicated that the resin bonded cast fixed partial denture with the lingual chamfer margin and mesial rest was the design to be chosen.

Dental Abutments↗
PubMed1990

[Adhesive cast restorations].

The aim of this article is to present the clinical use of the adhesive cast restoration in the treatment of the advanced perio case in an effort to overcome the serious restorative problems related to those cases. The use of the adhesive cast restoration in the advanced periodontal conditions has proved that it can be considered a permanent restoration. The main advantages in the use of the adhesive cast restoration are: i) Minimal tooth preparation, which eliminates the possibility of pulpal contamination. In fact, pulpal integrity is of crucial importance in the advanced perio case because of the close interrelationship between the pulp tissue and periodontal structures. ii) Supragingival lingual margins, which do not compromise the patient's esthetics and permit for good plaque control. iii) Reversibility of the restoration. iv) Reduced cost, which helps the clinician to use teeth with guarded prognosis from a periodontal point of view.

Costs and Cost Analysis↗
PubMedDate not supplied

Esthetic modification of cast dental-ceramic restorations.

The advantages and disadvantages of conventional opaque substructures (eg, metal ceramic restorations) used for creating esthetic complete crown restorations are reviewed, and the esthetic advantages of veneering a translucent crown (Dicor) are considered. An appropriate aluminous veneering porcelain was identified (Vitadur Veneer). This veneer porcelain was chosen to match the thermal coefficient of expansion of the cast glass-ceramic substructure. A flexural strength study was then completed and it showed no difference in the strength of the veneered and nonveneered translucent cast glass-ceramic specimens. Scanning electron microscopy revealed that the interface between the porcelain veneer and cast glass-ceramic substructure had no visible porosity and resulted in a continuous-appearing structure. Potential coping designs, as well as the clinical applications and ramifications of this modified crown, are discussed.

Aluminum Oxide↗
PubMed1989

[Peripilar keratin casts].

The hair casts are infrequent condition. There are two distinct groups: idiopathic and secondary. Idiopathic hair casts are described in three girls aged 3, 5 and 13 years. They are cousins, indicating a possible hereditary influence. It's a illness without systemic affection, with pathophysiology yet unknown. It is important to know, overall for differential diagnosis, specially nits. The only treatment is removal of casts by careful and repeated combing.

Adolescent↗
PubMed1989

Calibrated double split cast simulations for orthognathic surgery.

A cephalometric prediction tracing serves as a guideline for orthognathic surgery. Transfer of information from prediction tracings to cast simulation (model surgery) is part of treatment planning for surgical correction of dentofacial deformities. Articulated mounting with calibrated double split casts adds precision to the process and makes the final cast operation more effective. Systematic errors in the transfer of information are appraised critically.

Audiovisual Aids↗
PubMed1989

Optical measurement of dental cast profile and application to analysis of three-dimensional tooth movement in orthodontics.

Dental casts are frequently used for measuring the size, shape and position of a tooth. We have developed an optical apparatus for measuring a three-dimensional profile of a dental cast. The measurement is based on the triangular method which detects a laser spot on a cast by an image sensor. The apparatus is computer-controlled and designed to achieve a total measuring depth of 40 mm, a data acquisition time of 25 ms per point and a minimum scanning pitch of 0.1 mm. The depth and lateral resolutions are 0.05 and 0.1 mm, respectively, within a depth range of 25 mm. As a particular application of the apparatus, three-dimensional movement of teeth, including rotational movement, during orthodontic treatment, has been quantified by means of the superimposition of tooth profiles using a computer.

Child↗
PubMed1977

[The shaping of the margin in cast objects in oral rehabilitation].

Various preparations of margins in cast replacements as well as their insertion and finishing are studied and measured by means of radioactive isotopes. It was found, in particular, that the conventional preparation of cavity margins and the finishing of cast margins of tightly cemented cast replacements should be discontinued.

Cementation↗
PubMed1989

Interpretation of structural patterns appearing on corrosion casts of small blood and initial lymphatic vessels.

Structures imprinted on the corrosion casts of blood and lymphatic microvessels are examined by correlative scanning electron microscopy of corroded casts and fixed tissue. Replicas of the endothelial nuclear portions and cell boundaries and the plastic bands surrounding the casts of terminal blood vessels are demonstrated. In small lymphatics the replication of valve structures, interendothelial open junctions and direct prelymphatic connections is shown. The different imprint patterns are examined in regard to their morphological significance and under methodical aspects.

Animals↗
PubMed1988

[Assessment of the amount of palladium-silver alloy used for cast posts and veneer crowns].

Average amounts of palladium-silver alloy were assessed in a sample of 966 veneer crowns and 667 casted posts. The mean weight values of the samples under study were compared in relation to particular types of anterior teeth. The specimens cast in Auropal SE were weight by the precise balance, Tehtnica, type 6215. Results were analyzed by weight according to the type of the sample under study, and classified according to age, and to the anterior teeth of the upper and lower jaws. On an average, the heaviest posts and veneer crowns were measured on upper canines, whereas the lighest were those on lower incisors. A cast post was found to be by about 40% heavier than a veneer crown on the same tooth.

Crowns↗
PubMed1987

Scanning electron microscopy of vascular corrosion casts in comparative studies on renal vascular structure.

In comparative microcorrosion casting studies on renal vascular systems the following demands should be met: The preparation procedure (anaesthesia, operation, flushing of the blood vascular system, ...) should be in accord with the specific physiological properties of the animal under investigation and the casting procedure (injection, curing, maceration, ...) should be kept constant as far as possible. If these points are considered, comparative data, even of quantitative nature, can be obtained from corrosion casts. Examples of results at the organ, single vessel and intercellular level as well as correlation of the results with physiological data are given.

Animals↗