P.L. Fan

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.

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 Stability of New Composite Restorative Materials Under Accelerated Aging

The color stability of seven microfilled and conventional composites under conditions of accelerated aging was evaluated by reflection spectrophotometry. During early aging the composites generally became darker, more chromatic, and more opaque. The in vitro color stability of the microfilled composites was better and less influenced by erosion than the conventional composites.

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.

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.

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 to 7.3 x 10-3 mm3/mm2 after 900 h of aging. Surface morphology changed more dramatically for the conventional composites than for the other materials. Changes in surface chemistry as measured by FTIR-ATR were observed.

In vitro Wear of Aged Composite Restorative Materials

Wear characteristics of aged and unaged composite restorative materials were compared using single-pass sliding. There were differences in wear track widths, tangential forces, and surface failure classifications between aged and unaged composites. Changes in surface wear characteristics upon aging were attributed to surface degradation in the composite materials.

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. The veneering materials were similar in color to, but more opaque than, composite restorative materials. Changes in color during aging were minimal. Weight loss occurred during aging.

Adsorption of Streptococcus mutans on Chemically Treated Hydroxyapatite

Adsorption of Streptococcus mutans on hydroxyapatite and chemically treated hydroxyapatite was studied. Zeta potentials of the surfaces were measured. Chemically treated hydroxyapatite gave higher ζ potentials and lower S mutans adsorption.

Wear of aged dental composites

Abstract Surface morphology and wear characteristics of five dental composites subjected to accelerated aging were investigated. Aging conditions caused degradation of the surface as evidenced by the formation of microcracks and the exposure and loss of filler particles. Wear parameters such as track width, transition load and mode of surface failure caused by single-pass sliding were influenced by aging and by the composition of the composite.