Effects of hydrogen peroxide on the light reflectance and morphology of bovine enamel

Abstract

The purpose of this study was to examine the effects of a bleaching agent (30% hydrogen peroxide) on the surface of bovine enamel using a scanning electron microscope and a UV-VIS-NIR spectrophotometer. Five non-carious bovine incisors were bleached for 0, 1, 2 and 3 days using 30% hydrogen peroxide. The light reflectance spectrum was measured using a spectrophotometer with diffuse reflectance mode. Colour values and colour differences in the teeth were evaluated from the reflectance measurements with the CIE L*a*b* colour coordinate system. Surface alterations in the bleached and unbleached teeth were studied using a scanning electron microscope. The change of reflectance in the teeth was related to the change of colour. Most reflectance change occurred within a 1-day bleaching, and this result was confirmed by a CIE L*a*b* colour coordinate system. The colour differences in the bleached teeth were significant enough to be perceived by the observer's eye. The comparison of bleached to unbleached bovine enamel revealed that the bleached surface showed non-uniform slight morphological alterations, and it developed varying degrees of surface porosity. This study indicates that the bleached bovine teeth showed apparent colour differences as well as slight morphological alterations after bleaching.

Effect of Two In-office Whitening Agents on the Enamel Surface In Vivo: A Morphological and Non-contact Profilometric Study

“…Both HP and CP in-office bleaching products did not affect enamel surface roughness. However, previous studies suggest that subsurface alterations may occur in human teeth submitted to bleaching 9,21,34 due to the penetration of peroxide compounds into the enamel. Therefore, these observations and their clinical significance must be further investigated in in-office bleaching agents and at-home bleaching products, which, even if used at lower concentration, are kept in contact with enamel for a longer period of time.…”

“…28 On the other hand, since urea is alkaline, it raises the pH of the bleaching products, thus reducing the demineralization potential. 15 In previous studies (Table 1), most in vitro studies using high concentrations of hydrogen peroxide solution have been reported to produce morphological alteration of the enamel surface, 15,21,[30][31][32]34,38 modifications to enamel crystal distribution, 41 increased porosities of the superficial enamel structure 34 and higher adhesion of S mutans to the enamel surface. 18 Furthermore, surface chemical analysis has reported both modification in the calcium/phosphate ratio 42 and calcium loss, 37 thus supporting the hypothesis that bleaching agents are chemically active components able to induce important structural alterations of human enamel.…”

“…The major differences between these studies are the type of study setup (in vitro vs in vivo), sample size, type of tissue (human or bovine enamel), preparation of the tissue (polished or sound enamel), type of analysis carried out (mechanical test or morphological analysis), bleaching agent used (hydrogen peroxide or carbamide peroxide), bleaching agent concentration and formulation (gel or solution), length of bleaching agent exposure and other evaluation criteria. Also, methods of analysis are different among the studies, with protocols based on scanning electron microscope (SEM) analysis, [20][21]27,[30][31]34,36,38 microhardness tests, 9,11,14,36,38,40 profilometric techniques, 4,15,18,34,36,[38][39] plasma-atomic emission spectrometric analysis associated with chromatography, 37 infrared absorption spectroscopy correlated with x-ray analysis, 41 atomic force microscopy 10,28 and nanoindentation techniques. 5 Conversely, only a few studies have attempted to assess whitening effects in vivo, 22,26,29 usually based on the analysis of an enamel replica using SEM.…”

Indirect cytotoxicity of a 35% hydrogen peroxide bleaching gel on cultured odontoblast-like cells

“…2 and 3). It may be speculated that the similar cytotoxic effects observed in G1 and G2 are due to the fact that the 5 consecutive applications of the bleaching gel promoted deep structural alterations in the dental hard tissues (13), permitting an intense diffusion of the products of gel degradation through enamel and dentin.…”

“…It has been demonstrated that the application de H 2 O 2 on enamel produces porosities due to the protein matrix dissolution caused by the intense oxidative effect of the free radicals resulting from bleaching gel degradation (13). Studies have reported that due to its low molecular weight, the H 2 O 2 present in the bleaching gels can diffuse easily through dentin to reach the pulp chamber (4-6).…”