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Biomedical subjects

A Koran

Publications and source records attributed to A Koran.

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

Stain removal from a pigmented silicone maxillofacial elastomer.

The removal of environmental stains from a pigmented maxillofacial elastomer was carried out by solvent extraction under network swelling. Silastic 44210 was pigmented with 11 maxillofacial pigments prior to staining. Samples were stained with lipstick, methylene blue, and disclosing solution. These stains were then removed by solvent extraction with 1,1,1-trichloroethane. Color parameter measurements both before and after staining and after solvent extraction demonstrated the effectiveness of removing these stains by solvent extraction while causing little or no change in the color of the pigmented samples.

Color↗
PubMed1981

Reflection spectrophotometry of facial skin.

The color of human skin of 241 whites, blacks, and orientals was measured by reflection spectrophotometry. Among these groups, major differences in luminous reflectance and excitation purity, but not in dominant wavelength, were observed. The twin absorption bands of oxyhemoglobin at 540 and 580 nm were more prominent in whites (particularly females) than in orientals or blacks. Parameters determined for Source A were higher than those for Source C.

Asian People↗
PubMed1981

Stain removal from a silicone maxillofacial elastomer.

In this study, environmental stains were removed from maxillofacial elastomers by solvent extraction. Silastic 44210, an RTV silicone with proven color and physical property stability, was stained with lipstick, disclosing solution, and methylene blue. These stains were then removed by solvent extraction with each of four chemically dissimilar solvents, namely: toluene, benzene, 1,1,1-trichloroethane, and n-hexane. An additional series of samples was prepared with 11 maxillofacial pigments, not for staining, but for evaluation of pigment stability. Results obtained from spectrophotometric measurements before and after solvent extraction demonstrated the effectiveness of solvent extraction in removing stains, while there was little or no change in the color of the pigments or the base elastomer.

Chemical Phenomena↗
PubMed1980

Physical properties of maxillofacial elastomers under conditions of accelerated aging.

The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.

Chemical Phenomena↗
PubMed1980

Physical properties of a pigmented silicone maxillofacial material as a function of accelerated aging.

The effects of accelerated aging on a pigmented elastomer were evaluated by using a weathering chamber. Silastic 44210, a maxillofacial material with proven color and physical property stability, was chosen for pigmentation with 11 maxillofacial pigments. The values of ultimate tensile strength, maximum percent elongation, shear strength, Shore A hardness, and permanent deformation were determined for the pigmented elastomer before and after accelerated aging for 900 h. Results obtained indicate that the incorporation of 0.2% by weight of pigments can alter the physical and mechanical properties of the base elastomer. Accelerated aging had no effect on the physical properties of the pigment/elastomer combinations.

Chemical Phenomena↗
PubMed1980

Impression materials for recording the denture bearing mucosa.

To accurately record the denture bearing mucosa at rest or with the least possible tissue movement, the following suggestions should be considered: The denture bearing mucosa should be healthy and firm. Impression materials used should be of low viscosity. Materials which rapidly increase in viscosity after mixing should be placed in the mouth as soon as possible without compromising acceptable clinical procedures. The zinc oxide-eugenol materials have an advantage of a much longer working time. Materials with low contact angles with water may have flow characteristics that are more favorable for making impressions of the denture bearing mucosa. The pressure used to seat and hold an impression of the denture bearing mucosa should be kept at the minimum necessary to achieve adequate flow for that impression material. From this discussion, it is evident that no single impression material is ideally suited for making edentulous impressions. Perhaps in the future the dental manufacturers will consider developing and marketing products with the specific performance characteristics that have been outlined. Until that time, clinicians should be aware of the characteristics of the material they are using and modify their techniques accordingly.

Agar↗
PubMed1979

Color stability of a pigmented elastomer for maxillofacial appliances.

The color stability of a series of eleven maxillofacial pigments was determined after accelerated aging using reflection spectrophotometry. The results indicate that seven of the pigments demonstrated good to excellent color stability, while four of the pigments were less promising for clinical use.

Color↗
PubMed1979

Stain resistance of maxillofacial materials.

The resistance of three silicone and one polyvinyl chloride maxillofacial materials to staining by tea, lipstick, and disclosing solution was measured by reflectance spectrophotometry. Changes in color caused by staining were larger than changes caused by color instability of the base elastomers or pigments under conditions of accelerated aging.

Color↗
PubMed1978

The rheological properties of fluid denture-base resins.

The rheological properties of six commercial fluid denture resins were determined by rotational viscometry. Initial viscosity ranged from 67 to 575 centipoise at a rotational speed of 10 revolutions per minute. All resins showed initial non-Newtonian flow behavior and increased viscosity with time.

Acrylic Resins↗
PubMed1978

Color of dental restorative resins.

The color of 7 composite resins, an unfilled restorative resin, and 3 glaze coatings was determined by reflection spectrophotometry and visually with Munsell color tabs. Statistically significant correlations existed between comparable parameters of the spectrophotometric and Munsell data. There was observable color variations among the 11 resins studied, but only 3 materials were within the range for natural tooth color.

Acrylic Resins↗
PubMed1977

Color of gingival tissues of blacks and whites.

Value, chroma, and hue of gingiva of 100 black and 100 white patients were measured clinically with Munsell color tabs under fluorescent light and under simulated daylight. The color of uniformly pigmented attached gingiva of both blacks and whites was described most often by a value between 5/ and 7/, a chroma of /4, and a range of hues from 2.5R to 7.5R when determined under fluorescent light. The color of gingiva pigmented by melanin in 61 black patients was lower in value (3/ to 4/) and chroma (/1 to /2) but had a similar range of hues compared with uniformly pigmented gingiva. The use of a simulated daylight source instead of a fluorescent light present in the clinic resulted in a modest change in color described by an I of no more than 3.6.

Black People↗
PubMed1977

Color of denture resins.

The color of 24 commercially available denture resins was determined visually with Munsell color tabs and by reflection spectrophotometry. Correlation between Munsell and spectrophotometric data was found. The resins characterized for Black patients had a higher degree of specular reflectance and were more opaque than resins for Caucasians.

Color↗
PubMed1977

Apparent viscosity of materials used for making edentulous impressions.

The viscosity of commercially available impression materials used for making edentulous impressions was determined as a function of time and rotational speed. The impression materials studied showed large differences in viscosity and could be ranked into three groups. The values for one group--Plastogum, Ackerman cement (1:1 powder-to-liquid ratio), and light-bodied Permlastic--ranged from 23,800 cp to 57,200 cp. The viscosity values for a second group--Unilastic, syringe Elasticon, Luralite, and Coe-Flo--ranged from 92,200 cp to 107,000 cp. For a third group--Omniflex, Jeltrate, and Ackerman cement (2:1 powder-to-liquid ratio)--the viscosity values ranged from 239,000 cp to 257,000 cp. Light-bodied Permlastic, Ackerman cement (1:1 powder-to-liquid ratio), Jeltrate, and syringe Elasticon functioned as Newtonian liquids immediately after mixing. All other materials were non-Newtonian in behavior. The viscosity of most impression materials increased dramatically with time; the only exceptions were the zinc oxide-eugenol impression materials.

Alginates↗