Peroxide bleaching agent effects on enamel surface microhardness, roughness and morphology

Abstract

ABSTRACT:The aim of this study was to evaluate the surface roughness, microhardness and morphology of human enamel exposed to six bleaching agents (at baseline and post-treatment). Human dental enamel samples were obtained from human third molars and randomly divided into seven groups (n = 11): control, Whiteness Perfect -10% carbamide peroxide (10% CP), Colgate Platinum -10% CP, Day White 2Z -7.5% hydrogen peroxide (7.5% HP), Whiteness Super -37% CP, Opalescence Quick -35% CP and Whiteness HP -35% HP. Bleaching agents were applied according to manufacturers' instructions. The control group remained not treated and stored in artificial saliva. Microhardness testing was performed with a Knoop indentor and surface roughness was analyzed with a profilometer. Morphologic observations were carried out with scanning electron microscopy (SEM). Results were statistically analyzed by two-way analysis of variance and Tukey's test (5%), and revealed a significant decrease in microhardness values and a significant increase in surface roughness post-bleaching. Changes in enamel morphology after bleaching were observed under SEM. It was concluded that bleaching agents can alter the microhardness, roughness and morphology of dental enamel surface.

Effects of different concentrations of carbamide peroxide and bleaching periods on the roughness of dental ceramics

“…6,8,9,13 Although an increase in roughness has been observed in composite resins or glass ionomers after bleaching treatment, [18][19][20][21][22][23][24]27 no alteration in ceramic surfaces was observed after bleaching in the current study, 23 so the impact of bleaching agents on surface roughness may be considered material-dependent, as also demonstrated by previous studies. 16,[20][21][22][23] In these studies, the chemical stability of ceramics against bleaching agents was observed after treatment with 15% carbamide peroxide for 56 h, 23 16% carbamide peroxide for 126 h, 17 10% or 15% carbamide peroxide 27 and 38% hydrogen peroxide for 30 minutes 23 or 45 minutes, respectively.…”

“…The respective treatment agent was applied for six hours a day over 21 days, corresponding to 126 hours of treatment. Specimens to be bleached were covered with 0.03 ml of the respective bleaching agent, were placed in vacuum-formed custom trays with a drop of artificial saliva, 8,13 and were stored in a plastic container at 37 °C. [6][7][8] Specimens from control groups were stored only with artificial saliva drops in the vacuum-formed custom tray to mimic oral conditions.…”

“…1,[3][4][5] Several microscopic changes on the enamel surface morphology are also observed, due to enamel mineral loss and surface roughening. [6][7][8][9][10][11][12][13][14][15] Extremely unstable and reactive H + free radicals, released by bleaching agents, and low pH are described as the main cause of the side effects of prolonged use of these products. [6][7][8][9][10][11][12][13][14][16][17] Similarly, bleaching agents may cause structural changes on restorative materials that may compromise their physical properties and lead to premature failure.…”

“…[6][7][8][9][10][11][12][13][14][15] Extremely unstable and reactive H + free radicals, released by bleaching agents, and low pH are described as the main cause of the side effects of prolonged use of these products. [6][7][8][9][10][11][12][13][14][16][17] Similarly, bleaching agents may cause structural changes on restorative materials that may compromise their physical properties and lead to premature failure. [18][19][20][21][22][23][24] Although conventional dental ceramics are considered the most inert among all dental restorative materials, their surfaces can exhibit surface deterioration in contact with acidulated fluoride gels or other solutions.…”

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

“…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.…”