In vitro evaluation of human dental enamel surface roughness bleached with 35% carbamide peroxide and submitted to abrasive dentifrice brushing

Abstract

The aim of this in vitro study was to evaluate the surface roughness of human enamel bleached with 35% carbamide peroxide at different times and submitted to different superficial cleaning treatments: G1 - not brushed; G2 - brushed with fluoride abrasive dentifrice; G3 - brushed with a non-fluoride abrasive dentifrice; G4 - brushed without dentifrice. Sixty fragments of human molar teeth with 4 x 4 mm were obtained using a diamond disc. The specimens were polished with sandpaper and abrasive pastes. A perfilometer was used to measure roughness average (Ra) values of the initial surface roughness and at each 7-day-interval after the beginning of treatment. The bleaching was performed on the surface of the fragments for 1 hour a week, and the surface cleaning treatment for 3 minutes daily. The samples were stored in individual receptacles with artificial saliva. Analysis of variance and the Tukey test revealed significant differences in surface roughness values for G2 and G3, which showed an increase in roughness over time; G1 and G4 showed no significant roughness differences. The bleaching with 35% carbamide peroxide did not alter the enamel surface roughness, but when the bleaching treatment was performed combined with brushing with abrasive dentifrices, there was a significant increase in roughness values.

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

“…26 Therefore, any possible change in roughness due to in vitro treatment would be detected by contact profilometry. 11,12,16,26 No significant differences in ceramic roughness were observed after 126 hours of exposure to 10% or 16% carbamide peroxide in comparison to the baseline values, demonstrating that all products were inert in vitro to dental bleaching, so the hypothesis of this study was rejected. Our results corroborate those of Zavanelli et al, 27 who found no alterations on ceramic surfaces treated with 10% or 15% carbamide peroxide for 126 h. Therefore, accidental exposure of dental ceramics to bleaching agents does not change their surface roughness to values capable of increasing the risk for both secondary caries and periodontal inflammation.…”

“…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

“…These results are in accordance with previous in vitro studies. 10,27,36,39 Since both products tested in this experiment are designed for chairside procedures, they were used under rubber dam isolation. Impressions were recorded immediately after bleaching and before removing the rubber dam, thus, no contact with saliva was allowed.…”

“…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.…”