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At least 847 records · Page 47Linked to original sources
PubMed1992

Rapid isoelectric focusing of proteins in hydrolytically stable capillaries.

Three new types of capillary coatings for capillary isoelectric focusing that avoid siloxane chemistry, resulting in hydrolytically stable coatings, are described and tested: phenyl-silica, acrylamide-reacted vinyl-silica, and pure PTFE. Capillaries of these three types were compared using standard proteins and a biological mixture of proteins similar to what might be encountered in actual use. Of these, the acrylamide-coated capillary produced the highest-quality results. In contrast to capillaries prepared using siloxane reactions, the capillaries described herein exhibited greatly enhanced stability at high pH.

Acrylamides↗
PubMed1992

High-performance liquid chromatographic separation of detritylated oligonucleotides on highly cross-linked poly-(styrene-divinylbenzene) particles.

Detritylated oligonucleotides were separated by reversed-phase high-performance liquid chromatography on highly cross-linked polystyrene-based particles having a mean particle diameter of 2.3 microns. The addition of poly(vinyl alcohol) during polymerization, which resulted in the presence of hydroxyl groups on the surface of the poly(styrene-divinylbenzene) beads, was necessary to obtain baseline resolution of phosphorylated oligodeoxyadenylic acids with a chain length of up to 30 bases. The impact of temperature was investigated and optimum resolution was achieved at 40 degrees C. At pH 7.0, the retention times of oligonucleotides were found to depend on the ratio of bases and to increase in the order of C less than G less than A less than T. Under the same conditions, it was possible to separate phosphorylated from dephosphorylated oligonucleotides, the former being eluted earlier. Recoveries ranged from 92 to 100%.

Base Sequence↗
PubMed1975

Mouth protector for an edentulous patient.

Upper and lower bases and occlusion rims are made of a soft vinyl plastic to form a mouth protector for an edentulous patient. In practical use, the patient can breathe more comfortably with the protectors in place (Fig. 4) than with dentures in the mouth. In addition, the prosthesis is an aid in the prevention of injury to the jaws and head.

Humans↗
PubMed1980

An assessment of recent advances in external maxillofacial materials.

A variety of new materials representing several polymer classes and diverse fabrication procedures are now becoming available for use as external maxillofacial prostheses. Because of the availability of these materials, the severely disfigured patient can now be provided an opportunity to elad a near-normal life in today's society. Remarkable advancements have been made in providing the patient with prostheses which feel and look more like skin. Progress has also been made in simplifying fabrication procedures, thus reducing cost. Much remains to be done in materials research. Processing time is still too long for most of the materials. Some of the materials give variable results in the quality and stability of the prostheses because of sensitivity to contaminants and to lab conditions and operator technique. Extrinsic coloration is extremely tedious and diffult with many of the products. The fitting and attachment of the prosthesis to the patient continues to need much improvement. Margins are difficult to mask even with the best materials. Large prostheses of most of the materials are much too heavy and are poorly retained. Staining of the prostheses by foods, cosmetics, and tobacco is a serious problem. The need for an improved material has been recognized by various government agencies and a few of the industrial suppliers of synthetic polymers. Additional advances are sure to result from these efforts.

Chemical Phenomena↗
PubMed1980

Frozen-slab technique for mixing zinc phosphate cement for cast restorations.

The technique for handling zinc phosphate cement can be altered to achieve enhanced properties of the cement. The compressive strength of the material can be decreased. The film thickness can be maintained within acceptable limits, and the possibility of pulpal damage can be kept low by maintaining temperature changes in the cement similar to those obtained from a room temperature-slab technique. The technique advocated by this report is as follows: 1. Store the aluminum slab with vinyl covering in a freezer at -15 degrees C to -20 degrees C in a plastic bag to prevent ice formation on the surface. 2. Remove the slab when ready to mix. 3. Quickly wipe the slab clean. 4. Dispense twice as much powder and liquid as recommended on the slab. 5. Start timer. 6. Slowly incorporate the powder into the liquid over a large area of the slab for 2 minutes. 7. Allow the mix to remain on the slab. 8. The instrument for placing the cement can be placed under the slab. The casting can be placed on a corner of the slab. 9. At 10 minutes, place the cement into the casting(s) and seat. 10. Remove excess cement. 11. Clean the slab by rinsing in water and gently wiping. 12. Dry the slab, place it in the plastic bag, and return it to the freezer.

Aluminum↗
PubMed1981

Flexure fatigue of 10 commonly used denture base resins.

The flexure fatigue properties of 10 denture base resins (four different types) were tested. Each specimen underwent two-way testing in a water bath maintained at 37 degrees +/- 1 degree C. A load of 3,650 gm was applied a 342 flexures per minute until the specimen broke. The resin types listed in order of increasing resistance to flexure fatigue are polymethylmethacrylate (PMM) pour resins, PMM thermosetting resins, vinyl resins, and a PMM grafted resin. Although small samples size and scatter of results limit broad application of this data, it is of some significance that the grafted resin Lucitone 199 tended to withstand repeated flexure when compared to the other resins.

Dental Stress Analysis↗
PubMed1986

Using soft vinyl stents to facilitate augmentation of maxillary anterior atrophic ridges with hydroxyapatite.

A technique has been described for fabrication of a surgical template made of soft vinyl mouthguard material. Use of this stent at the time of surgery can be of great value to the oral surgeon and the prosthodontist. The risk of excessive augmentation and migration of the particulate hydroxyapatite to an undesired area will be minimized if the stent is used as a matrix. Uniform results in size and form of the ridge can be obtained from the surgical procedure when the stent is used. The denture-bearing area of the maxillary anterior ridge will improve significantly, enabling the dentist to make a maxillary complete denture.

Alveolar Ridge Augmentation↗
PubMed1989

Effects of dental medicaments on examination glove permeability.

Dental care providers wear gloves for all clinical procedures. This study was designed to assess the intactness of examination gloves after exposure to commonly used agents. Finger portions from latex and vinyl examination gloves were sealed to syringe barrels and exposed to alcohol, eugenol, a surface disinfectant, cavity varnish, or commercial mouth wash. Tritiated water was introduced into the finger-tip portion, which was suspended in a vacuum flask containing distilled water. Aliquots of water were withdrawn from the flask at intervals of 5 minutes to 8 hours and analyzed for transfer of radioactivity through the glove tip. Treatment with agents such as eugenol and cavity varnish resulted in significant leakage after 5 to 15 minutes. Although some agents apparently quickly damaged the gloves, leaks developed in untreated gloves with time. Results suggest that visibly intact gloves may have developed microleaks and that changing gloves during long clinical procedures may be indicated.

Dental Cavity Lining↗
PubMed1992

Comparison of bond strength of six soft denture liners to denture base resin.

The bond strength of six commercial soft denture liners was evaluated using a modified tensile test. The soft denture liners investigated were Prolastic, VinaSoft, Flexor, Molloplast-B, Novus, and Super-Soft. The samples were processed according to the manufacturers' instructions to cured denture base resin (polymethyl methacrylate; PMMA). The soft denture liners were 10 x 10 x 3 mm and were processed between two PMMA blocks. The samples were placed in tension until failure. The mode of failure, cohesive or adhesive, was also recorded. The results of this study showed that the bond strength is related to the components of the materials. Prolastic, VinaSoft, and Flexor had the lowest bond strength to cured PMMA and ranged from 9.6 to 11.3 kg/cm2. Super-Soft, Novus, and Molloplast-B demonstrated better bond strengths and ranged from 16.7 to 17.6 kg/cm2. The bond strength of Novus could be improved by using the recommended bonding agent and bonded Novus at 26.1 kg/cm2 had the highest bond strength of all materials tested.

Adhesiveness↗
PubMed1976

Carcinogenic, mutagenic and teratogenic risks associated with vinyl chloride.

The data presented demonstrate clearly that vinyl chloride (VC) is related to a significant excess of mortality from cancer of the liver, lung and brain among workers occupationally exposed to VC. The risk of dying from cancer of the lymphatic and hematopoietic system also appears to increase with an increase in latency. These cancer sites could have been predicted by the animal bioassay conducted by Maltoni. With regard to the liver, even the histophthologic type of cancer (angiosarcoma) was observed first in experimental animals. A study of cancer mortality among populations residing proximate to VC polymerization facilities also demonstrated an increased risk of dying from CNS and lymphatic cancer. These latter findings raise cause for concern about out-plant emmissions of VC, but without further study these cancers obviously cannot be interpreted as being related to out-plant exposure to VC. Various test systems now have elicited a positive mutagenic response to VC. Thus, our observations of a significant excess of fetal mortality among the wives of males, who were occupationally exposed to VC, raise public health concern that VC may be mutagenic in humans. With regard to the teratogenicity of VC, observations of a significant excess of children born with birth defects were reported among populations residing proximate to VC polymerization facilities. Additional epidemiologic study is needed to determine whether a repeated pattern of excessive numbers of children born with birth defects can be observed in other communities with VC polymerization facilities.

Abnormalities, Multiple↗
PubMed1977

Vinyl chloride mutagenesis in Drosophila melanogaster.

In inhalation experiments, Drosophila males were exposed to vinyl chloride at concentrations of 200, 850, 10,000 30,000 or 50,000 ppm for 2 days, and to 30 or 850 ppm for 17 days. VCM was mutagenic in the recessive-lethal test both after short-term and long-term exposures. The lowest effective concentration (LEC) was 850 ppm after 2 day exposure, and this value could be lowered to 30 ppm by prolonging the exposure time to 17 days. With the concentration levels tested, the mutation frequency increased with concentrations and reached a plateau at 10,000 ppm. This indicates a substrate saturation effect. In contrast with the recessive lethal assay, negative results were obtained when tests on dominant lethals, translocations, entire and partial sex-chromosome loss were carried out with VCM at 30,000 ppm for 2 days. This finding of a false negative seems a logical consequence of the observed saturation effect, and strengthens the concept that there exist two effective concentrations for point mutations vs the induction of chromosome breakage events. Vinyl chloride monomer provides another example to support our view that chromosome breakage is not a reliable measure of mutagenic activity.

Animals↗
PubMed1977

Lack of mutagenicity of vinyl chloride in two strains of Neurospora crassa.

No detectable induction of mutations could be found in two strains of Neurospora crassa after their conidia were treated with vinyl chloride, in ethanol solution and in its gaseous form. The results suggest that although N. crassa seems to lativating systems does not increase mutagenic activity of vinyl chloride in the two strains tested. At the same time these strains were mutated easily by UV and methyl methanesulfonate.

Aerosols↗
PubMed1978

Chromosomal analyses in vinyl chloride-exposed workers.

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973--1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, gamma-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.

Chromosomes↗