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Biomedical subjects

P L Fan

Publications and source records attributed to P L Fan.

At least 55 records · Page 3Linked to original sources
PubMed1981

Frictional behavior and surface failure of acrylic denture teeth.

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.

Acrylic Resins↗
PubMed1981

In vitro accelerated aging of composites and a sealant.

The in vitro accelerated aging of conventional and microfilled composite restorative materials and a sealant was studied. Volume loss/surface area ranged from 2.0 x 10(-3) mm3/mm2 for I to 7.3 x 10(-3) mm3/mm2 for SF after 900 h of aging. Surface morphology of the conventional composites was characterized by crazing and exposure of filler particles. The surfaces of the microfilled composites also showed crazing. The surface morphology of the sealant appeared unchanged. Comparisons of infrared ATR spectra between zero and 900 h of aging showed that slight chemical changes occurred at the surface of AR but not SF.

Composite Resins↗
PubMed1981

Color stability and aging of plastic veneering materials.

The color stability and aging characteristics of commercial plastic veneering materials were studied in vitro by an accelerated aging method. Values of luminous reflectance, dominant wavelength, and excitation purity at baseline were similar to values reported for composite restorative materials. The veneering materials were more opaque than composites. After aging for 900 h, small changes in color were observed instrumentally, but were difficult to detect visually. Weight loss of some the veneering materials after aging was greater than that anticipated from solubility in water alone.

Color↗
PubMed1981

Translucency of human dental enamel.

Translucency of human dental enamel was determined by total transmittance of wavelengths from 400 to 700 nm. The transmission coefficient at 525 nm was 0.481 mm-1. Total transmission of light through human dental enamel increased with increasing wavelength. Human tooth enamel is more translucent at higher wavelengths. The translucency of wet human enamel and enamel after dehydration was also measured by total transmittance. The transmission coefficient at 525 nm decreased from 0.482 to 0.313 mm-1 after dehydration and was reversed on rehydration. The decrease in translucency occurred as a result of the replacement of water around the enamel prisms by air during dehydration.

Color↗
PubMed1981

Surface roughness of microfilled composites.

Average surface roughness values, profile tracings, and surface microstructures of three microfilled composites and a conventional composite were studied with respect to final finishing procedures. Surfaces cured against Mylar matrix strips were the smoothest and were similar for all composites. White stones produced the roughest surfaces for Isopast, Silar, and Superfil. Silicon carbide disks and aluminum oxide disks produced smoother surfaces. The finished surfaces of the microfilled composites were smoother than the corresponding surfaces of Concise for each finishing instrumentation evaluated.

Acrylic Resins↗
PubMed1981

Surface mechanical properties of stone, resin, and metal dies.

Two improved stone die materials (Duroc and Silky Rock) used with water and with a hardener, one resin die material with dispersed metal powder (Die-Met), and copper and silver electroplated metal die materials were evaluated for surface mechanical properties. The improved stone dies had the highest surface roughness, intermediate surface hardness and the highest loss of material in two-body abrasion. The use of a hardener decreased the surface roughness, but did not improve abrasion resistance. The improved stone dies, with or without hardener, showed brittle failure in single-pass sliding at low normal loads. The resin dies had the lowest hardness. The unfilled resin die had low surface roughness and was similar to metal dies. The resin-metal die had a surface roughness similar to the improved stone dies. The presence of dispersed metal powder in the resin did not increase the hardness. Both resin die materials had intermediate values of material loss in two-body abrasion and showing tensile cracking and loss had intermediate values of material loss in two-body abrasion and showed tensile cracking and loss of material on single-pass sliding at medium normal loads. The metal dies had the highest hardness and the least surface roughness. They also had the lowest material loss in two-body abrasion. The metal dies showed ductile behavior in single-pass sliding.

Calcium Sulfate↗
PubMed1980

Translucency of dental porcelains.

The translucency of comparable shades of five dental porcelains was determined. Both direct transmittance and total transmittance were measured at wavelengths of 400-700 nm. For 1 mm of porcelain, the values for direct transmittance were low and averaged 0.13 percent, whereas the values for total transmittance averaged 26.8 percent. Transmittance increased with increasing incident wavelength. These results indicated a high degree of light scattering.

Color↗
PubMed1980

Erosion of composite resins.

The surface degradation of composite resins caused by accelerated aging was studied. Accelerated aging for 900 hours caused erosion of the resin matrices and exposure of filler particles. Differences in surface profiles after aging suggest that the materials eroded at different rates. Accelerated aging may model erosive wear of composites.

Color↗
PubMed1980

Color stability of new composite restorative materials under accelerated aging.

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.

Color↗
PubMed1979

In vitro wear of microfilled and visible light-cured composites.

Wear of microfilled composites, a visible light-cured composite, and a conventional composite were characterized by two-body abrasion and single-pass sliding. There were differences in abrasion rates among the materials. Tangential forces, wear track widths, and surface failure modes were different among materials. Wear characteristics are combinations of these properties.

Composite Resins↗