Relation between the Fluorescence and Shade of Extracted Human Teeth
Date Issued
2011
Date
2011
Author(s)
Lin, Hsing-Yi
Abstract
The natural teeth emit blue fluorescence under the exposure to ultraviolet. It is essential that dental prostheses present such fluorescent character to be as vivid as natural teeth even thought under special light source. Therefore, some chemical activators were added to commercial dental restorative material or porcelains to mimic the fluorescence of natural teeth. Several researchers concluded that organic luminophore may be the possible candidates of dental fluorescence. Furthermore, a few studies demonstrated fluoresce intensity was age-dependent and the sex and the type of tooth have no significant influence on tooth fluorescence. The mechanism of fluorescence of natural teeth, however, was not yet clear. Very few attempts have been made in exploring the relationship between fluorescence and tooth color. Since understanding the fluorescence may improve the esthetics of dental prostheses, we measured the fluorescent spectra of extracted human teeth and recorded the CIE coordinates of tooth color. The purposes of this study were to explore the mechanics of fluorescence of natural teeth, to correlate the fluorescent spectra of a natural tooth with the donor’s sex and age and the type of tooth, and to analyze if there is any correlation between fluorescence
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and tooth shade.
Sixty-five extracted human teeth from 43 patients were collected and the sex, age of the patient and type of tooth were also recorded. Five of the samples were sectioned and then separately processed with 400℃ heat to denature the organic compound of teeth or soaked in EDTA solution to demineralize the teeth. The fluorescent spectra of the original and treated samples were measured. Otherwise, a specimen with a size of 4×4×2 mm was cut from each of the other 60 natural teeth by means of high speed dental hand piece. The excitation and emission spectra were obtained from the enamel side and the dentin side using corrected PL spectrophotometer. The CIE coordinates (X, Y) of each sample were also computed. In addition, the CIE L*a*b* color scales were measured with a colorimeter and compared with fluorescence intensity.
Experimental results and conclusion：(1) The fluorescene of a tooth was diminished with heat and increased with demineralization, which suggested that organic luminophore could be the candidates of fluorescence. (2) The fluorescence of dentin is much stronger than enamel in a tooth. (3) The wavelength of the excitation spectra of extracted human teeth was around 300 nm to 450 nm with peak at 390 nm, as well as the wavelength of the emission spectra of extracted human teeth was
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around 410 nm to 600 nm with peak at 470 nm. There was inter-individual difference in fluorescence spectra and intensity. (4) The X and Y values of tristimulus calculated from the spectra located in blue to greenish-blue region in the CIE color space. (5) Different teeth from the same individual showed spectra with similar peak wavelength and CIE coordinates but different fluorescent intensity. (6) Regarding to the correlation between fluorescence and L*a*b* color scale, the peak intensity of fluorescence was statistically negatively correlated to the b value. It meant that a higher fluorescence intensity was accompanied with a higher blue tone in a tooth. (7) The wavelength of the excitation spectra of tryptophan, a suggested candidate of fluorescence, was around short wavele UV light to 370 nm with peak at 300 nm, and the wavelength of the emission spectra was around 370 nm to 550 nm with peak at 380 nm. The fluorescence of tryptophan located in purple-blue area. As a result, the tryptophan may not a possible candidate of the fluorescence.
Subjects
fluorescence
shade
extracted human teeth
Type
thesis
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