Biomedical subjects
Publications and source records attributed to C N Raptis.
In this study, a maxillofacial silicone elastomer was stained with cigarette smoke. The stain was then removed by solvent extraction using 1,1,1-trichloroethane. The cigarette smoke produced large color changes in the elastomer as measured from spectrophotometric reflectance curves. The solvent was totally effective in removing the cigarette stain without changing the color of the silicone base.
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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.
Six variables that could affect the surface roughness of a casting were investigated. The variables were (1) type of alloy, (2) mold temperature, (3) metal casting temperature, (4) casting machine, (5) sandblasting, and (6) location of each section. It was determined that the training portion of a complete cast crown had rougher surfaces than the leading portion. Higher mold and casting temperatures produced rougher castings, and this effect was more pronounced in the case of the base metal alloy. Sandblasting reduced the roughness, but produced scratched surfaces. Sandblasting had a more pronounced affect on the surface roughness of the base metal alloy cast either at a higher mold temperature or metal casting temperature. The morphology and the roughness profile of the original cast surface differed considerably with the type of alloy used.
The water characteristics of acrylic denture teeth were investigated under single- and double-pass sliding. The response of acrylic teeth to sliding was that of a relatively ductile material. The wear characteristics were affected similarly by environments of water and saliva. The "enamel" surfaces showed more resistance to penetration and were less susceptible to surface damage than the "dentin" surfaces. The effect of the second pass was to increase track width and cause a more severe mode of surface failure.
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.
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.
1. The effect of mold conditions on the UTS, n, and TS at 200% and 300% elongations, and Shore A hardness was measured for Silastic 44210. 2. There was no difference in n, Shore A hardness, and TS at 200% and 300% elongation between Silastic 44210 samples whether produced in metal or coated stone molds. 3. The highest UTS for Silastic 44210 was demonstrated for samples processed in aluminum molds. The UTS was slightly reduced when coated stone molds were used, and it was considerably reduced with untreated stone molds. It is felt that the slight decrease in UTS with coated stone molds would not compromise the use of stone molds clinically, particularly when ease of processing is considered. 4. Petroleum jelly, silicone spray, and tinfoil substitute were all equally effective in improving the physical properties of the elastomer when processed in a stone mold. These results demonstrate the necessity of using a mold sealant when processing Silastic 44210 in a stone mold.
The color stability of seven commercial composite restorative materials under conditions of accelerated aging was evaluated by reflection spectrophotometry at baseline and 300, 600, and 900 h. During early aging the composites generally became darker, more chromatic, and more opaque. Changes in color of the conventional composites during aging were influenced by erosion of the resin matrices and exposure of filler particles. Color stability of the microfilled composites under the in vitro conditions tested was better than that of the conventional composites and did not appear to be influenced as much by erosion.
Physical and mechanical properties of four commercial micro-filled composite resins, a visible light-cured composite resin, and a conventional composite resin were investigated. Isocap, Isopast, and Superfil were similar in most properties. Compared with Concise, they had lower values of inorganic filler content and modulus of elasticity and higher values of water sorption, depth of indentation, and linear coefficient of thermal expansion. The properties of Silar were between those of Concise and the other microfilled composite resins. Fotofil had lower values of modulus of elasticity, water sorption, and linear coefficient of thermal expansion than Concise.