Masking Power of Dental Opaque Porcelains

A technique was developed to qualify the masking power of undiluted opaque dental porcelain by dilution of opaque powder with a clear glaze powder and by extrapolation of quantitative data gathered by reflectance spectrophotometry. Quantification of reflectance data was made on dilute opaque porcelains using the scattering and absorption coefficients in the Kubelka-Munk equation. Qualitative comparisons of undiluted opaque porcelains were made from quantitative data gathered from diluted opaque porcelains.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67998/2/10.1177_00220345840630062601.pd

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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67987/2/10.1177_00220345800590051101.pd

Optical Properties of Direct Restorative Materials

The contrast ratio, light reflectivity, scattering coefficient, and absorption coefficient of four composites and an unfilled resin were calculated algebraically from reflection spectrophotometric data using Kubelka's equations. The correlation coefficient between calculated and experimental values of contrast ratio was 0.9996. Values of infinite optical thickness ranged from 4.19 to 6.70 mm.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68196/2/10.1177_00220345810600050601.pd

The Colors of Mixtures of Dental Opaque Porcelains

The colors of mixtures of dental opaque porcelains and modifiers were measured with use of the CIE L*a * b* uniform color space. Mixtures of dental porcelains were tested to duplicate the range of human tooth colors. Vertical movements in the yellow and blue directions were obtained. Horizontal movements in the red and green directions were achieved. Reflectance measurements were made with use of a spectrophotometer with an integrating sphere. Spectrophotometer measurements were converted to absolute reflectance and then used to calculate CIE a* b* values for a 2° standard observer and for illuminant C. Movements in the yellow, red, blue, and green directions for adequate simulation of the tooth color range can be demonstrated with use of dental opaque and modifier porcelains.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67312/2/10.1177_00220345890680090601.pd

Light Scattering and Gloss of an Experimental Quartz-filled Composite

For samples of polymethylmethacrylate with and without quartz filler, the inverse of the contrast-gloss ratio is shown to be related to surface roughness and to the optical scattering coefficient. This finding adds to the importance of optical scattering, which has been widely studied because of its relation to color and translucency of materials. Furthermore, optical scattering by composite fillers is shown to be linearly related to the concentration of the filler material within the range of concentrations studied. Quartz fillers were incorporated at concentrations from 5 to 20 weight percent and were short fibers or granular powder, with the granular particles ranging in median equivalent spherical diameter from 15 to 3.3 μm. The efficiency of optical scattering for the granular quartz filler increased as the size of the filler decreased.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68026/2/10.1177_00220345860650060501.pd

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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67845/2/10.1177_00220345780570091601.pd

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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68115/2/10.1177_00220345810600100401.pd

The Detection of Incipient Caries with Tracer Dyes

The purpose of this study was to determine the increase in color contrast produced by the use of a tracer dye in detection of incipient caries lesions with transillumination. Twenty four caries-free first premolars were immersed in an acid gelatin for production of artificial incipient caries lesions. After the lesions had developed, these teeth were photographed by transillumination. Two photographs were taken of each tooth. The first photograph showed the lesion without dye. A blue tracer dye was then added and absorbed by the lesion, and a second photograph was taken. The data on the color difference were obtained by use of a reflectance colorimeter and showed a four-fold increase between the lesion and surrounding area with the dye. A two-way analysis of variance was used for the statistical interpretation. The color difference between the lesion without the dye and then with the dye was significant. The use of the blue tracer dye, therefore, significantly increased the contrast in the images of the artificial incipient lesions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68289/2/10.1177_00220345890680021101.pd

Virtual distillation for quantum error mitigation

Theoretical Physic