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 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.
Dentist and patient preferences are often used to select replacement teeth in prosthodontics. Face shape compared with inverted tooth form classifications based on Leon William's work are currently used. Shapes of teeth and faces have been referred to as square, ovoid or tapered, or some combination of these. Six patients, three male and three female, were selected as being classically square, tapered or ovoid in facial form. Three sets of dentures had been made for each patient with tapering, ovoid and square denture teeth. Using a standardized photographic technique, full face views with profiles and close-ups of the teeth were taken. Then from standardized enlarged tracings, key anatomic and derived points were marked, digitized and computer analysed. The face shapes and inverted tooth forms were digitized in the same manner. A comparison of tooth moulds versus the actual denture teeth shows a highly significant difference (P less than 0.001) between set and unset denture teeth. There is also a significant difference (P less than 0.001) between facial form and denture teeth using temporal zygomatic and gonial widths for faces, compared with incisal, contact, and cervical widths for the teeth.
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