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Biomedical subjects

S M Newman

Publications and source records attributed to S M Newman.

50 records · Page 3Linked to original sources
PubMed1982

Incidence of nickel-induced sister-chromatid exchange.

Nickel is a recognized carcinogen to which the general population is being increasingly exposed. A nickel-induced alteration in the incidence of sister-chromatid exchanges in cultured lymphocytes has been investigated. Human lymphocytes from a single donor were cultured in media containing various concentrations of nickelous chloride from 10(-6) to 10(-3) M and a control culture containing no added nickel. A significantly increased incidence of exchanges over background was induced at 1.19 x 10(-4) M as indicated by a Student's t-test. A concentration/response curve was generated up to 5 x 10(-4) M where the nickel concentration was lethal to the cells. The nickel response was analyzed by a chi-square test for any variation in location of activity across the karyotype and no differences were detected. The background incidence did vary from a uniform distribution across the karyotype with increasing incidences in chromosomes 1 and 2 and those of the B group, and decreased incidences in the E, F, and G groups.

Cells, Cultured↗
PubMed1981

Ultraviolet light and ultraviolet light-activated composite resins.

In a comparison of the UV light--activated composite resins, Estilux was polymerized to a significantly greater depth than the other composite resins. In general, Lee-fill polymerized the least. When comparing the UV light sources, the Lee light and the Duralux light did not significantly differ from each other, but both polymerized the materials tested to a significantly greater depth than the other light sources. Of the two time exposures, 60-second exposure provided a significantly greater depth of polymerization than 20 seconds for each light with each material.

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↗
PubMed1980

Castability of low gold content alloys.

A test pattern composed of 14 gauge sprue wax and various gauges of nylon lines was constructed, and used to differentiate the castability of several alloys. The castability of seven commercial low gold content alloys for porcelain fused to metal restorations was compared. Five commercial low gold content yellow alloys for full cast restorations were compared to each other and to a Type III certified control.

Chemical Phenomena↗
PubMed1977

Pharmacological prophylaxis against the development of kindled amygdaloid seizures.

The kindling of amygldaloid and cortical seizures in cats was used to study the prophylactic effects of phenobarbital, phenytoin, ethosuximide, acetazolamide, and dexamethason. Phenobarbital prevented the evolution of such seizures beyond stage 4 in all amygdaloid-kindling animals during 160 days of study. The prophylactic effect persisted on periodic challenge after the drug had been discontinued. Phenytoin, ethosuximide, acetazolamide, and dexamethasone appeared to have no prophylactic effect against the development of kindled amygdaloid seizures. With cortical kindling, both phenobarbital and phenytoin retarded the evolution of seizures without achieving true prophylaxis. The drugs appeared to act as suppressants. Prophylaxis was not an "all-or-none" phenomenon but rather a limitation of the stage of seizure evolution.

Acetazolamide↗
PubMedDate not supplied

Effectiveness of reciprocal-action instrumentation for polishing composite resin: an in vitro study.

This in vitro study investigates the use of reciprocal-action instrumentation for polishing composite resin restorative materials. Electron photomicrographs were made of surfaces of a microfilled and a hybrid composite resin restorative material polished by various reciprocal-action polishing procedures, including several types of polishing pastes used with nonabrasive plastic tips. The best polish on the microfilled composite resin restorative material tested was produced by ending with 3-mu diamond polishing paste. The best polish on the hybrid composite resin restorative material tested was produced by ending with 0.5-mu diamond polishing paste. The surfaces produced were comparable to those produced by polishing discs.

Carbon↗
PubMedDate not supplied

Effect of repeated sterilization and ultrasonic cleaning on curet blades.

PURPOSE: Instrument cleaning and sterilization are important steps in infection control. This study investigated the effect of repeated ultrasonic cleaning, cycles of autoclave or chemiclave, on the surface and cutting edge of stainless steel and carbon steel curets. METHODS: Eight carbon steel and six stainless steel Columbia #13/14 curets were cleaned or sterilized in a series of treatments by one of the following methods: ultrasonic cleaning, chemiclave sterilization, and autoclave sterilization. In addition, two carbon steel instruments were placed in an anticorrosive dip followed by autoclave. The blades of the curets were examined and photographed with the scanning electron microscope (SEM) at 200 X and 1000 X for baseline and after 2, 4, 8, 16, and 32 treatment cycles. Photographs were evaluated for visible change in surface appearance by four examiners independently. Photographs for each treatment time were compared to the baseline (pretreatment) photographs for the same instrument. They were scored as (1) no visible change; (2) slight change; or (3) moderate to major change. Changes observed were: surface pitting, corrosion products as additions to the surface, edge deterioration, or loss of structure. RESULTS: Stainless steel curets showed slight or no change after the three treatments. Carbon steel curets were affected by all treatments. The chemiclave produced slight change. The autoclave produced slight change after the fourth treatment cycle and moderate to major change after the eighth cycle. Those carbon steel instruments treated by anticorrosive dip followed by the autoclave showed pronounced change after 16 or 32 cycles. The most varied results were from the ultrasonic cleaner; one blade showed moderate to major change after only four cycles, the other showed slight change at that point and major change only after 32 cycles. CONCLUSION: With stainless steel curets, ultrasonic cleanings or sterilization with autoclave or chemiclave can be used without visibly affecting the cutting edge. With carbon steel instruments, chemiclave is the least damaging sterilization method followed by anticorrosive treatment before autoclaving. Use of the autoclave without the anticorrosive pretreatment or use of an ultrasonic cleaner negatively affects the integrity of the surface and cutting edge of these instruments.

Corrosion↗