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 Table of Contents  
Year : 2019  |  Volume : 6  |  Issue : 1  |  Page : 13-17

In vitro assessment of human enamel surface composition bleached with two different bleaching agents

Department of Science of Dental Materials, Ziauddin College of Dentistry, Ziauddin University, Karachi, Pakistan

Date of Web Publication12-Mar-2019

Correspondence Address:
Nazish Fatima Ahmed
Ziauddin College of Dentistry, Ziauddin University, Karachi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sjos.SJOralSci_19_18

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Background: Varieties of methods are available for more obstinate tooth discoloration such as crowns, veneer, and micro and macro abrasion of enamel, but tooth bleaching gained high patient acceptance. The aim of the present research was to estimate changes in surface enamel composition after bleaching 16% carbamide peroxide (CP) (home-use bleaching) with 38% hydrogen peroxide (HP) (in office bleaching).
Materials and Methods: A total of 90 enamel slabs from 45 sound human third molars were randomly divided into three groups. Of three groups, per group had thirty samples (n = 30), of which samples of Group 1 were placed in artificial saliva at 37°C in incubator (Memart, Germany) during complete experiment. Sample of Groups 2 and 3 was treated with power whitening gel (White Smile 2011, Germany) and tooth whitening pen (white Smile 2011, Germany), respectively. Later on, after bleaching treatment, discs were thoroughly washed and stored in artificial saliva at 37°C in incubator. Chemical analysis was done with energy dispersive spectroscopy (Edx) detector to detect changes in surface composition.
Results: Energy dispersive X-ray spectroscopy (Edx) analysis showed no significant difference between all the three groups for Ca% mass (P > 0.99) and Ca% atomic (P > 0.99), C% mass (P = 0.78) and C% atomic (P = 0.76), and O% mass (P > 0.99) and O% atomic (P = 0.28). Similar results were shown for Na, Mg, P, and F.
Conclusion: Statistically insignificant effect was observed on enamel composition with both bleaching agents (38% HP and 16% CP).

Keywords: Bleaching, carbamide peroxide, enamel composition, hydrogen peroxide

How to cite this article:
Ahmed NF. In vitro assessment of human enamel surface composition bleached with two different bleaching agents. Saudi J Oral Sci 2019;6:13-7

How to cite this URL:
Ahmed NF. In vitro assessment of human enamel surface composition bleached with two different bleaching agents. Saudi J Oral Sci [serial online] 2019 [cited 2022 Aug 15];6:13-7. Available from: https://www.saudijos.org/text.asp?2019/6/1/13/254027

  Introduction Top

Perfect smile is the main key for face esthetic harmony and satisfaction of patient with their dental appearance. In this regard, there is a high demand in clinics for esthetic treatments and tooth color plays an important role in the perceptions of esthetic.[1]

Due to simplicity, cost-effectiveness, and conservation property, tooth bleaching has become a popular procedure. Even varieties of methods are available for more obstinate stains such as crowns, veneer, and micro and macro abrasion of enamel but tooth bleaching gained high patient acceptance.[2]

Organic compound which contains conjugated double bond results in color producing stain. Thus, the principal theory on the bleaching procedure is that molecules of stains are oxidized into colorless compounds, throughout the procedure of bleaching agent working as an active oxidizing agent.[3] It changes a long organic chain which is yellow into small colorless chain.[2]

The procedure that involves in whitening of tooth is divided into three separate stages: first stage, bleaching agent move into the structure of tooth; second, bleaching agent interacted with the stain molecules; and in third, as a result of which altered tooth structure surface reflects such that it reflects light differently.[4]

Ideally, the bleaching agent minimizes damage to the tooth structure, but unfortunately, this oxidizing reaction is not specific because of its small molecular size and weight, and it diffuses through the organic matrix of enamel and may not limit to chromogens also cause damage to organic matrix of enamel.[5]

One of the possible side effects related to bleaching procedure is hypersensitivity.[6] The hypersensitivity problem during the bleaching procedure has been associated to the loss of minerals which leads to increased porosity on the enamel surface and subsurface.[7],[8] This change is surface composition, and morphology is responsible for affecting mechanical properties as it depends on the ratio between these components.[9] Usually, decrease in enamel microhardness has been used as an indicator of the mineral loss following bleaching procedures.[10]

The hydrogen peroxide (HP) ionization procedure takes place due to the presence of decomposition catalysts, enzymes in saliva, and the free radicals diffuse through the interprismatic substance of enamel, convert the highly pigmented carbon rings into simple chains.[11] Low pH of the bleaching agents causes alteration in the mineral content of the enamel and dentine, resulting in weakening of mechanical property.[10] Bleaching procedure adversely modifies the enamel composition by reducing its inorganic content (calcium, phosphate, and fluoride); due to these changes, mechanical properties are also adversely affected.[11],[12]

Literature reported that enamel exposed to 10% carbamide peroxide (CP) showed alteration in microhardness, micromorphology, and composition.[13] Although several other studies have demonstrated no major changes in the surface of enamel,[14] there is a concern that sustained and extensive treatment will result in dissolution of the enamel matrix.[13] Little evidence is found about the effect of bleaching product with different peroxide concentrations, formulation, and application time on enamel.

The controversial findings and limitations in existing literature review have helped to set the objectives of this research work. The aim of the current research was to find out the effect in between home-use bleaching agent (16% CP) and in office bleaching agent (38% HP) on composition of enamel.

The hypothesis tested is that various bleaching agents their concentration and methods of their application affect the composition of enamel.

  Materials and Methods Top

It was an in vitro experimental study. Forty-five human permanent third molars obtained from the Department of Oral and Maxillofacial Surgery (Dow University).

The crowns were separated from roots and 90 enamel blocks with standardized area of 9 mm2 (3mm × 3 mm) were prepared. The specimens (enamel blocks) sectioned in a digital low-speed cutting saw (MTI Corp; USA) under water spray and smoothened with sandpaper.

The specimens were identified and remained stored in artificial saliva at 37°C during the experiment. The composition of artificial saliva given in [Table 1].[15]
Table 1: Chemical composition of the artificial saliva used as storage medium

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Ninety blocks were selected after scanned with stereo microscope (Motic DMW-143-FBGC Hong Kong) at ×20 to exclude those with cracks and stains.

Blocks were randomly divided into three groups (n = 30) in according to the bleaching treatment. After the division, Group 1 that is control group was placed in artificial saliva at 37°C, whereas Groups 2 and 3 were treated with power whitening gel (White Smile 2011, Germany) and tooth whitening pen (White Smile 2011, Germany), respectively, according to manufacturer's instruction. The basic composition of bleaching agents is shown in [Table 2].
Table 2: Manufacturer, concentration, and bleaching regimen of the whitening products used in this study

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Surface composition analysis done with energy dispersive spectroscopy (Edx) detector to check changes in chemical composition. The specimens were dried, fixed on aluminum stubs, and sputter-coated with gold in a vacuum evaporator (JEOL-JFC 1500, Japan), and the most central region will be used for Edx.

Data were entered and analyzed in Statistical Package of the Social Sciences (SPSS) V. 16.0 (SPSS Inc., Chicago, US). Kruskal–Wallis ANOVA was run to test the difference in chemical composition among different groups.

  Results Top

Energy-dispersive X-ray spectroscopy (Edx) investigation measured the relative amount of calcium (Ca), carbon (C), oxygen (O), sodium (Na), magnesium (Mg), phosphorus (P), and fluoride (F) of the total elemental content (100%) in mass percentage (% mass) and atomic percentage (% at). ANOVA analysis revealed no significant difference between all the three groups for Ca% mass (P > 0.99) and Ca% at (P > 0.99), C% mass (P = 0.78) and C% at (P = 0.76), and O% mass (P > 0.99) and O% at (P = 0.28). Similar results were shown for Na, Mg, P, and F as shown in [Table 3]. Mean ± standard deviation of Edx analysis regarding the elemental composition is shown in [Table 4].
Table 3 : Mean±standard deviation regarding the elemental composition of different groups

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Table 4: Mean±standard deviation of energy dispersive X-ray spectroscopy analysis regarding the elemental composition

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  Discussion Top

In the current study, because of the impossibility to perform scanning electron microscopy-Edx tests in patient's oral cavity, therefore, the experiment was done on extracted human teeth. Moreover, comparing the outcome ofin vitro toin vivo experiment could be a problem. Furthermore, although studies have shown that there is almost negligible variation among the shades of the teeth pre- and postextraction procedure, it is also reported that human teeth before and after extraction procedure do not show any significant difference in their mechanical, physical, and chemical properties.[16]

A study has reported that saliva and demineralized water are found to be ideal storing solutions forin vitro studies.[17] In the current study, artificial saliva with neutral pH was used as it keeps tooth surface remain unaltered. It has been reported that the presence of the mineral content along with neutral pH of saliva can prevent enamel surface from negative effects of storage inin vitro state. However, remineralization ability of the saliva is due to the presence of its saturated calcium and phosphorous elements in its composition.[18] Similar findings were seen in the current study as negligible amount enamel surface reduction was reported when 38% HP and 16% CP; bleaching agents were applied.

Filiz et al. in 2012 had used three different concentration bleaching agents with different activation modes; however, consumption of all three bleaching agents did not show any significant difference in mineral content of enamel. The outcomes of the present research were in concordance with Filiz et al., the reason may be associated with lesser contact time period of bleaching agents with enamel.[19]

In the present study, no significant difference was reported among all the three groups for Ca, C, O, Na, Mg, P, and F, these findings were compatible with the outcomes of Oltu and Gurgans. They also presented with no significant difference in concentration of enamel with CP and 16% CP (8 h/day for 6 weeks).[20]

In the current study, there was an insignificant difference found among chemical composition of control and bleach groups. These findings were in similarity with the studies reported by Goo et al. in 2004 and Park et al. The reason might be related to proper methodology used in the study.[21],[22]

Studies reported by McCrackens and Haywood showed minimal loss of calcium from surface of teeth on bleaching with 10% CP solution for 6 h.[23] The outcomes of the present research were in disparity with McCrackens. These variations in result might be due to difference in methodology.

The conclusions of the current study were in contrary with the findings reported by Lee et al., the reason might be due to use of different set of teeth and contact time. As Lee used bovine teeth for bleaching with 120 h of contact time, however, in the current study, human teeth were bleached for 15 min.[24]

This has been reported by most of the researchers that HP and CP containing products have statistically insignificant harmful effects on microhardness of the enamel, its morphology, and chemistry, even with the used of maximum concentrations of HP or CP. However, few researches have reported significant effect but have some limitations in their in vitro methodologies thus failed to simulate thein vivo situation accurately.

  Conclusion Top

Within the limitation of the current research, following conclusion is drawn: There were no significant changes in chemical composition of bleached and unbleached specimen of enamel.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Henn-Donassollo S, Fabris C, Gagiolla M, Kerber í, Caetano V, Carboni V, et al. In situ andin vitro effects of two bleaching treatments on human enamel hardness. Braz Dent J 2016;27:56-9.  Back to cited text no. 1
Burrows S. A review of the efficacy of tooth bleaching. Dent Update 2009;36:537-8, 541-4, 547-8.  Back to cited text no. 2
Markovic L, Jordan RA, Lakota N, Gaengler P. Micromorphology of enamel surface after vital tooth bleaching. J Endod 2007;33:607-10.  Back to cited text no. 3
Kwon SR, Wertz PW. Review of the mechanism of tooth whitening. J Esthet Restor Dent 2015;27:240-57.  Back to cited text no. 4
Yazici AR, Khanbodaghi A, Kugel G. Effects of an in-office bleaching system (ZOOM) on pulp chamber temperature in vitro. J Contemp Dent Pract 2007;8:19-26.  Back to cited text no. 5
Swift EJ Jr., Heymann HO, Wilder AD Jr., Barker ML, Gerlach RW. Effects of duration of whitening strip treatment on tooth color: A randomized, placebo-controlled clinical trial. J Dent 2009;37 Suppl 1:e51-6.  Back to cited text no. 6
Armênio RV, Fitarelli F, Armênio MF, Demarco FF, Reis A, Loguercio AD, et al. The effect of fluoride gel use on bleaching sensitivity: A double-blind randomized controlled clinical trial. J Am Dent Assoc 2008;139:592-7.  Back to cited text no. 7
Berger SB, Pavan S, Dos Santos PH, Giannini M, Bedran-Russo AK. Effect of bleaching on sound enamel and with early artificial caries lesions using confocal laser microscopy. Braz Dent J 2012;23:110-5.  Back to cited text no. 8
Zimmerman B, Datko L, Cupelli M, Alapati S, Dean D, Kennedy M, et al. Alteration of dentin-enamel mechanical properties due to dental whitening treatments. J Mech Behav Biomed Mater 2010;3:339-46.  Back to cited text no. 9
Justino LM, Tames DR, Demarco FF. In situ andin vitro effects of bleaching with carbamide peroxide on human enamel. Oper Dent 2004;29:219-25.  Back to cited text no. 10
Joiner A. The bleaching of teeth: A review of the literature. J Dent 2006;34:412-9.  Back to cited text no. 11
Cubukçu HE, Ersoy O, Aydar E, Cakir U. WDS versus silicon drift detector EDS: A case report for the comparison of quantitative chemical analyses of natural silicate minerals. Micron 2008;39:88-94.  Back to cited text no. 12
Akal N, Over H, Olmez A, Bodur H. Effects of carbamide peroxide containing bleaching agents on the morphology and subsurface hardness of enamel. J Clin Pediatr Dent 2001;25:293-6.  Back to cited text no. 13
Price RB, Sedarous M, Hiltz GS. The pH of tooth-whitening products. J Can Dent Assoc 2000;66:421-6.  Back to cited text no. 14
Klimek J, Hellwig E, Ahrens G. Effect of plaque on fluoride stability in the enamel after amine fluoride application in the artificial mouth. Dtsch Zahnarztl Z 1982;37:836-40.  Back to cited text no. 15
Goodkind RJ, Schwabacher WB. Use of a fiber-optic colorimeter forin vivo color measurements of 2830 anterior teeth. J Prosthet Dent 1987;58:535-42.  Back to cited text no. 16
Abouassi T, Wolkewitz M, Hahn P. Analysis of erosion effects of storing solutions on enamel surface. J Dent Res 2008;87:791.  Back to cited text no. 17
Shannon H, Spencer P, Gross K, Tira D. Characterization of enamel exposed to 10% carbamide peroxide bleaching agents. Quintessence Int 1993;24:39-44.  Back to cited text no. 18
Filiz YC, Sema SO, Esra F, Sevil G. Effect of office bleaching systems on chemical compositions of enamel and dentin: Anin vitro study. Clin Dent Res 2012;36:35-41.  Back to cited text no. 19
Kihn PW, Barnes DM, Romberg E, Peterson K. A clinical evaluation of 10 percent vs. 15 percent carbamide peroxide tooth-whitening agents. J Am Dent Assoc 2000;131:1478-84.  Back to cited text no. 20
Goo DH, Kwon TY, Nam SH, Kim HJ, Kim YJ. The efficacy of 10% carbamide peroxide gel on dental enamel. Dent Mat J 2004;23:522-7.  Back to cited text no. 21
Park HJ, Kwon TY, Nam SH, Kim HJ, Kim KH, Kim YJ, et al. Changes in bovine enamel after treatment with a 30% hydrogen peroxide bleaching agent. Dent Mater J 2004;23:517-21.  Back to cited text no. 22
McCracken MS, Haywood VB. Demineralization effects of 10 percent carbamide peroxide. J Dent 1996;24:395-8.  Back to cited text no. 23
Lee KH, Kim HI, Kim KH, Kwon YH. Mineral loss from bovine enamel by a 30% hydrogen peroxide solution. J Oral Rehabil 2006;33:229-33.  Back to cited text no. 24


  [Table 1], [Table 2], [Table 3], [Table 4]


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