Effects of Bleaching Agents on Human Enamel Light Reflectance

Abstract

Objectives: Tooth whitening has been associated with splitting-up chromogenic molecules by hydrogen peroxides. Though micromorphological alterations are well documented, little is known about optical changes as a function of shifting in wavelengths. Therefore, the aim of the current study was to measure reflectance changes after bleaching in vitro by using a spectrometer.Methods: Forty-eight enamel slabs (diameter = 5 mm) were prepared from the sound enamel of extracted human teeth that were: 1) fully impacted, 2) from juveniles ages 10 to 16 years, 3) from adults 35 to 45 years of age and 4) from seniors older than age 65. In all specimens, the baseline total reflectance measurement was performed with a computer-assisted spectrometer Clinical RelevanceIn dental bleaching, the micromorphological alterations of hard tissues have been well investigated, but little is known about the optical changes involved. The results of the current study showed that enamel, irrespective of maturation, is subjected to a shift in reflectance towards blue within the color space and enhanced reflection. This effect was demonstrated in different bleaching agent concentrations and protocols. Results: Total reflectance significantly increased after bleaching at all enamel maturation stages, irrespective of the bleaching agent concentration, for wl 450 nm (blue) and 500 nm (green) with p<0.0001. At 750 nm (red), significant changes only occurred in enamel from adults and seniors (p<0.04). However, the efficacy of bleaching was significantly increased in the blue and green light spectra as compared to the red spectra (p<0.0001). Conclusions:The results of the current study showed that the exclusive assumption of the "chromophore effect" in dental bleaching could not be sustained, because whitening of the dental enamel works at different maturation stages, even in impacted teeth. This effect is irrespective of the bleaching protocol used and the bleaching agent concentration.

Analysis of the Color and Fluorescence Alterations of Enamel and Dentin Treated With Hydrogen Peroxide

“…3 and 4) show an increased reflection in the range of wavelengths near the blue, especially in the enamel specimens. These data confirm the higher values of the b* coordinate, as previously observed (9,25). The coloring pigments within an object will absorb different wavelengths of light, allowing other wavelengths to scatter out the object.…”

The influence of desensitizing dentifrices on pain induced by in-office bleaching

“…Free radicals, such as perhydroxyl (HO 2 − ), are able to oxidize chromophores and break them down into less complex molecules that reflect more light. 5,[7][8][9] Declaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript.…”

Review of the Mechanism of Tooth Whitening

“…It is well known that a rough or coarse surface results in more diffuse reflection, turning the object brighter, whereas a smooth surface leads to more specular reflection, and that increased backscattering of short wavelengths that are reflected as bluish‐white due to opalescent effects at small structures plays a considerable role in the light scattering of teeth . Although an increase in surface roughness post‐whitening is not necessarily anticipated, where present, it may result in increased reflectance spectra and thus in improved digital color reading . The enhanced reflection on the surface post‐whitening would, in turn, render the enamel more opaque, as can also be observed in early carious lesions …”

“…84 Although an increase in surface roughness post-whitening is not necessarily anticipated, where present, it may result in increased reflectance spectra and thus in improved digital color reading. 109,113,116,117 The enhanced reflection on the surface post-whitening would, in turn, render the enamel more opaque, as can also be observed in early carious lesions. 92,93,111 Within the same context, it has been suggested that demineralization during tooth whitening might contribute to the whitening effect.…”