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Biomedical subjects

L Gettleman

Publications and source records attributed to L Gettleman.

At least 37 records · Page 2Linked to original sources
PubMed1982

A model culture system with human gingival fibroblasts for evaluating the cytotoxicity of dental materials.

A model experimental culture system and protocol are described to screen polymerized dental materials for diffusible toxic products. The system employs cultures of human gingival fibroblasts grown in plates containing immobilized samples of polymerized resins. Comparative cytoxicity is evaluated by counting viable cells with the aid of phase optics at several time periods up to 48 h. To achieve adequate statistical sampling, multiple counts are made in four different zones at 90 degrees angles from each sample and at three distances from the centers of samples. The most significant data were generated during a 24 to 48 h test period in climate. This cytotoxicity test measured cell death as a function of time of exposure and distance from the sample (24 h, 0 to 3 mm; 48 h, 3 to 6 mm) and permitted a calculation of the relative cytoxicity for each material, which is termed the viability index (VI). This can be expressed as a percentage related to the control, which is called the time-distance cytotoxicity index (TDCI). This method is simple to carry out because it used basic laboratory equipment, is rapid, and has a sound scientific basis. It focuses on times and distances when or where, or both, the greatest cellular changes are taking place. Some data illustrated are based on the screening of eight different restorative resins. The literature of cell culture testing of dental materials is reviewed. It is concluded that biotoxicity studies ideally should employ diploid human target cells from the oral cavity because the cells retain specialized features. Secondary cultures or strains of human diploid gingival fibroblasts, which are relatively easy to obtain and maintain, are recommended as cells of choice for screening dental restorative materials in vitro.

Adult↗
PubMed1981

Effect of internal relief, vibration, and venting on the vertical seating of cemented crowns.

The presence of a vent hole in the occlusal surface, vibration during seating, and internal relief inside cast crowns were investigated individually and in all combinations for their effect on vertical seating on metal dies, using zinc phosphate cement. It was found that: 1. Vibration, applied horizontally, had no effect by itself or any interaction with venting or internal crown relief. 2. Venting and internal relief alone effectively achieved good seating. 3. Venting and internal relief together were the most effective combinations. 4. When crowns were seated well, they tended to tilt less.

Cementation↗
PubMed1981

Identification of a foreign body using energy dispersive x-ray analysis.

A foreign object, presumably swallowed during a dental appointment, was recovered by using an esophagoscope and thought to be a piece of dental impression material, probably alginate. It was identified as being of nondental origin by means of visible light and scanning electron microscopy (SEM), the latter coupled to an energy dispersive X-ray analyzer. Histologic examination revealed some amorphous crystalline material surrounded by parakeratin and exfoliated squamous cells. The material was essentially radiolucent. A known dental alginate impression material contained diatomaceous earth filler (siliceous shells of diatoms), but no microscopic symmetrical figures were seen in the foreign body. After dehydration, both materials were carbon-coated and observed in an SEM at 20 kV at magnifications up to 2000 X. The spectrum of secondary X-rays produced by the scanning electron beam revealed only magnesium in the foreign body and mostly silicon in the dental alginate. There are no known dental products that contain magnesium as the only inorganic ingredient and so the foreign body is believed to be not of dental origin. The patient may have had an antacid or laxative having magnesium as a major ingredient in the stomach, and this may have been refluxed from the stomach after stimulation of the normal gag reflex during the dental procedure.

Dental Materials↗
PubMed1980

Strength and biocompatibility of polymethacrylate-silica composite dental implant materials.

A study was made of the strength properties of several composite dental implant materials composed of silica microspheres (6%, 24%, and 48% by weight) and PMMA. Prepared specimens of the materials were tested for compressive strength and tensile strength as a function of the curing methods. Compressive strength was reduced only slightly when the 6% mixture was used, as compared to 100% PMMA, but the compressive strengths of the 12% and 24% mixtures were reduced by approximately 30% when compared to 100% PMMA. The compressive strengths of these materials were reduced even further after curing in a microwave oven, and the tensile strengths decreased to a greater degree. The 6% mixture was reduced by 38% in the heat-cured specimens and was reduced by 27% in the microwave-cured specimens. Tooth replica implants were placed in baboons and the peri-implant tissues were studied histologically after 6 months. Inflammation was minimal. Peri-implant alveolar bone was viable and active, and both connective tissue and epithelial attachment to the implant surface was evident.

Alveolar Process↗
PubMed1980

Measurement of in vivo corrosion rates in baboons, and correlation with in vitro tests.

The Lineal Polarization Technique was used to determine the polarization resistances and corrosion currents of various dental restorative and implant alloys and amalgams placed in the teeth of animals, and as laboratory samples in artificial saliva. Gold- and chromium-containing alloys corroded the least, and amalgams generated the highest corrosion currents. There was good agreement between measurements made in vivo and in vitro. This is the first time that corrosion current have been measured in the mouth repeatedly over a long time span. These methods may be developed into useful predictive tests of in vivo corrosion.

Animals↗
PubMed1980

Corrosion behavior of Au and Ag modified Cu-Ni-Mn alloys.

The linear electrochemical polarization method was used to provide quantitative in vitro measurements of corrosion rates as a function of exposure time for Cu-Ni-Mn, Cu-Ni-Mn-Au, Cu-Ni-Mn-Ag, and Cu-Ni-Mn-Au-Ag alloys in artificial saliva. Both Au and Ag additives to dental-cast Cu-Ni-Mn alloys lowered the corrosion rate significantly.

Copper↗
PubMed1980

Status report on low-gold-content alloys for fixed prostheses. Council on Dental Materials, Instruments, and Equipment.

Because of their savings in cost and comparable mechanical and handling properties, low-gold-content dental casting alloys will remain an attractive alternative to high-gold-content alloys. Certain compositions perform well in the corrosive oral environment; others do not. Accurate information on such performance is currently unavailable. Accurate prediction of tarnish and ocrrosion behavior awaits development and acceptance of reliable and valid performance tests. There is adequate evidence that not only the Ag, Cu, and Pd ratios are important for resistance to corrosion but also the addition of minor amounts of other elements may be important for adequate clinical performance.

American Dental Association↗
PubMed1979

The problem of corrosion and tarnish of dental restorative and implant metals.

The linear polarization technique has been used to measure polarization resistances and corrosion currents directly in the mouths of baboons and in vitro for a wide range of dental and implant alloys. Good correlations were found to exist between these two conditions, indicating that this test is accurate and valid as well as being simple to perform. Intraoral corrosion proceeded faster, probably due to abrasion by foodstuffs. Tarnish has also been measured using an intraoral tristimulus colorimeter and results were compared with the corrosion determinations. The tarnish of pure metals (Au, Ag, and Cu) was inversely proportional to corrosion. Gold alloys tarnished little but varied in corrosion current. Dental amalgams corroded the most but the tarnish experience depended more on their chemistry than their precious metal composition.

Animals↗
PubMed1978

Histologic response to porous PMMA implant materials.

Poly(methyl methacrylate) as used in polymer replica tooth implants was fabricated into 6 X 6 mm cylindrical specimens and cured in either an air oven, pressure pot, autoclave, or microwave oven. Polymer porosity was achieved by means of either 1) intrinsic foaming agents, or 2) compacting different sizes of large beads with a minimum of monomer, with dense PMMA used as a control. Specimens were then implanted in the long bones of baboons. Histology of thin-sectioned and ground specimens from the sacrificed animals revealed complete tissue ingrowth into implanted material made of medium and large PMMA beads, very superficial ingrowth into material containing foaming agents and anorganic bone chips, and no ingrowth into dense PMMA implants. None of the implants were rejected or caused chronic inflammation. The effect on histologic response of the different curing methods could not be distinguished.

Animals↗
PubMed1978

Surface texture and strength of vitreous carbon-poly(methyl methacrylate) dental implant materials.

A study has been carried out on the surface texture and the strength of several dental implant materials composed of vitreous carbon microballoons (6, 24, and 48 wt %)and poly(methyl methacrylate). Two sizes of microballoons were used--particle size less than 100 micrometer and particle size greater than 100 micrometer. Square wafers of the materials (10 X 10 X 1 mm) were studied with the surface sandblasted in half of the specimens. SEM studies revealed a rough porous surface with scattered moderately sized deep cavities in the 6% and 24% specimens with an increase in the number of cavities in the 24% specimens. The 48% specimens revealed a rough, porous surface composed of large shallow craters. Prepared specimens of the materials, processed by a gas-fired air oven and by a microwave oven, were tested for compressive strength and tensile strength using an Instron Universal Testing Machine. Compressive strengths of the various mixtures were similar, but mixtures using VC particle size over 100 micrometer demonstrated somewhat reduced compressive strength. Tensile strengths of the mixutres decreased significantly as the amount of VC increased, with a 20% reduction at 24 wt % and a 45% reduction at 48 wt %.

Carbon↗
PubMed1978

Preliminary evaluation of the histotoxicity and radiopacity of lead-containing elastic impression materials.

Severe reactions can be caused when elastic impression materials are trapped beneath soft tissues. To develop a rank order of severity of responses, a series of these materials was injected beneath the oral mucosa of a baboon. Alginate and polysulfide rubbers containing lead peroxide produced severe reactions; hydrocolloid, polysulfide without lead, silicone, and polyether produced more mild reactions. The more toxic materials proved to be more radiopaque than the others. Tests for foreign body toxicity should be made a part of future specifications for these materials, and the use of toxic ingredients should be reduced as much as possible. These materials should be made opaque to X rays and of a different color than those of soft or hard tissues.

Abscess↗