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ORIGINAL ARTICLE
Year : 2014  |  Volume : 2  |  Issue : 2  |  Page : 78-82

Susceptibility of teeth to re-pigmentation after bleaching: An in vitro study


Department of Conservative Dentistry and Endodontics, Maitri College of Dentistry and Research Center, Anjora, Durg, Chhattisgarh, India

Date of Web Publication11-Jul-2014

Correspondence Address:
Abhilasha Avoy Dash
Department of Conservative Dentistry and Endodontics, Maitri College of Dentistry and Research center, Anjora, Durg - 491 001, Chhattisgarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-4619.136641

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  Abstract 

Introduction: Whiter or brighter smile, which is a cornerstone of a beautiful esthetic smile, can be achieved by bleaching. The public concern about appearance has been partly responsible for increased awareness in esthetic dentistry and consequently bleaching techniques. Bleaching solutions have been reported to cause alterations and loss of mineral content in surface enamel after bleaching. These irregularities in enamel surface could result in more susceptibility to re-pigmentation, thereby adversely affecting the whitening treatment. Aim: To evaluate the susceptibility of teeth to re-pigmentation using two different bleaching materials, i.e. 35% hydrogen peroxide (H 2 O 2 ) and 16% carbamide peroxide. Subjects and Methods : In this study, 30 extracted teeth were divided in three groups. Group I was bleached with 35% H 2 O 2 , Group II with 16% carbamide peroxide, and Group III was used as control. They were then stained with silver nitrate stain to evaluate their susceptibility to pigmentation after bleaching. The shade of each tooth was recorded before bleaching, after bleaching, and after pigmentation using a Vita shade guide. Results: Results showed that after staining with silver nitrate, the teeth in all groups became darker but the amount of change in the shade value of the samples was different for the two groups. The change of shade was greater for Group I as compared to Group II after pigmentation. This change in shade between Groups I and II was found to be statistically significant using one-way ANNOVA test (P < 0.05). Conclusions : Thus, we concluded that susceptibility to pigmentation increases after bleaching. Furthermore, pigmentation is greater when H 2 O 2 is used for bleaching.

Keywords: Bleaching, re-pigmentation, carbamide peroxide, H 2 O 2 , silver nitrate


How to cite this article:
Dash AA, Dash AK, Goyal B. Susceptibility of teeth to re-pigmentation after bleaching: An in vitro study . J Res Dent 2014;2:78-82

How to cite this URL:
Dash AA, Dash AK, Goyal B. Susceptibility of teeth to re-pigmentation after bleaching: An in vitro study . J Res Dent [serial online] 2014 [cited 2020 May 28];2:78-82. Available from: http://www.jresdent.org/text.asp?2014/2/2/78/136641


  Introduction Top


As it is famously said by Phyllis Diller, "Smile is a curve that sets everything straight". Whiter or brighter teeth, which are a cornerstone of a beautiful esthetic smile, can be achieved by bleaching. The public concern about appearance has been partly responsible for increased awareness in esthetic dentistry and consequently in various bleaching techniques and materials. Conditions which may need tooth whitening include, mild generalized staining, age yellowing, mild tetracycline stains, very mild fluorosis, acquired superficial staining, stain from smoking tobacco, tea/coffee stains, and young patients with an inherited gray or yellow hue. [1] The two most commonly used techniques for external vital bleaching are, home bleaching-where the patients apply the bleaching agent on their teeth using custom made trays (10-22% carbamide peroxide is most commonly used) and office bleaching-where the dentist performs tooth whitening treatment

(35-50% Hydrogen Peroxide, H 2 O 2 , is most commonly used). [2] These bleaching solutions have been reported to cause a wide variety of changes in enamel and dentin. Following application of some commercial forms, a loss in mineral content of dentin has been reported. [3] Also, it has been reported that if the bleaching material is applied with a tooth brush, the enamel roughness will be increased. [4] It has also been found in various in vitro studies that application of bleaching agents increases surface roughness and decrease enamel microhardness of teeth. [5],[6],[7],[8],[9],[10] Also, the risk of caries was found to increase due to adhesion of cariogenic bacteria to the enamel surface as the enamel characteristics are altered by repeated bleaching. [11],[12]

Many studies have also been carried out to determine the effect of bleaching agents on enamel and dentine microhardness, surface roughness, and fracture resistance but few have concentrated on the susceptibility of teeth to re-pigmentation after bleaching. Hence, the aim of this study was to determine the susceptibility of teeth to re-pigmentation after bleaching with two bleaching agents, i.e. 35% H 2 O 2 and 16% carbamide peroxide.


  Subjects and methods Top


Thirty freshly extracted premolars of patients undergoing orthodontic treatment were collected for the study. The teeth were cleaned with ultrasonic scaler, polished with pumice paste, and then stored in saline. The apical foramina were sealed with glass ionomer cement. (GC Fuji) The root surface of all samples was coated with a water resistant transparent nail varnish. Thirty samples were randomly assigned to three groups. Each sample was scanned for a matching shade from the Vita shade guide. (Vitapan) [Figure 1]a and b The vita shade guide was used for value disposition, assigning an incremental number to each shade [Table 1]. The shade comparisons were performed by two observers. In case of disagreement among the two observers, the mean of the two values was recorded. In Group I, teeth were bleached using 35% H 2 O 2 (Pola-office, SDI) [Figure 2] as per the manufacturer's instructions, i.e. 15 minutes three times a day, every alternate day for four days. In Group II, teeth were bleached using 16% carbamide peroxide (Pola-night, SDI) [Figure 3] as per the manufacturers' instruction, i.e. 90 minutes a day for 15 days. Group III was used as control; no bleaching agent was used. In Group III, teeth were only immersed in distilled water for 15 days.
Figure 1: After staining with silver nitrate, the teeth in all groups became darker. But the amount of change in the shade value of the samples was different for the two groups. The change of shade was greater for Group I as compared to Group II after pigmentation. (a) Shades registered before bleaching using Vita shade guide, (b) Shades registered before bleaching using Vita shade guide

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Figure 2: 35% Hydrogen peroxide (Pola office SDI) used for bleaching of teeth in Group 1

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Figure 3: 16% Carbamide peroxide (pola night SDI) used for bleaching the teeth in Group 2

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Table 1: Shade and their values

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All samples in Groups I and II were stored in distilled water in between the bleaching procedures. After 15 days, the samples from Groups I and II were compared with the Vita shade guide and their new shades were noted [Figure 4]a and b. All samples were immersed in silver nitrate solution (50% by weight) for 4 hours. They were then fixed for 24 hours using a radiographic fixing solution (dithioxamide solution) (Photon F32). Each specimen was washed under running water for 15 seconds to remove the loosely precipitated silver nitrate.
Figure 4: (a) Shades registered after bleaching using Vita shade guide, (b) Shades registered after bleaching using Vita shade guide

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All samples were once again matched with the Vita shade guide in value disposition and their shades were registered [Figure 5]a and b The corresponding value for each matching shade was recorded and used for statistical analysis. One way analysis of variance (ANNOVA) was used to determine the significance of statistical differences among the three groups.
Figure 5: (a) Shades registered after pigmentation using Vita shade guide, (b) Shades registered after pigmentation using Vita shade guide

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  Results Top


A summary of the results can be observed in [Table 2] and [Figure 6]. After bleaching, all samples of the two groups became lighter. Although the change in shade values was more in Group I (35% H 2 O 2 ) than in Group II (carbamide peroxide), the difference between them was not found to be statistically significant. After staining with silver nitrate, the teeth in all groups became darker but the amount of change in the shade value of the samples was different for the two groups. The change of shade was greater for Group I as compared to that for Group II after pigmentation. This change in shade between Groups I and II was found to be statistically significant using one way ANNOVA test (P < 0.05).
Figure 6: Graphical representation of the results obtained showing that tendency of pigmentation increases after bleaching. Also, the susceptibility of teeth to re-pigmentation is higher when bleached with hydrogen peroxide, H2O2, (35%) as compared to carbamide peroxide (16%)

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Table 2: Mean shade values before and after pigmentation

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  Discussion Top


This study assessed the susceptibility to pigmentation of teeth after the use of two different bleaching agents. Silver nitrate was used for staining because of its high contrast, stability after precipitation, small particle size, which allows minimal penetration, clinically undetectable imperfections making them readily visible. In this study, we found that 16% carbamide peroxide used in home bleaching was as effective as 35% H 2 O 2 used in office. Although the change in shade values was more in Group I (35% H 2 O 2 ) than in Group II (carbamide peroxide), the difference between them was not found to be statistically significant. Therefore, the treatment selection will entirely depend upon the patient's preference whether they find visiting the dentist or wearing the tray more convenient. After bleaching, when the silver nitrate dye was introduced, re-pigmentation occurred and all the teeth became darker. Although a change in the shades of untreated enamel surface (control group) was observed, the difference in their values was not statistically significant. The dye can penetrate any existing gap between the enamel rods. However, it seems that these gaps are smaller or less frequent in untreated enamel. This can be the reason why the difference in shade value of the samples in control group was less. Re-pigmentation also occurred in the group treated with bleaching agents. The change in the shades was greater in Group I (H 2 O 2 ) as compared to Group II (carbamide peroxide). Several studies have demonstrated that no change in hardness occurs on the surface of enamel after the use of carbamide peroxide. [13],[14],[15] Titely et al. reported an increase in surface roughness after bleaching with carbamide peroxide. [8],[16],[17] On the other hand, it was found in a number of studies that H 2 O 2 can result in a decrease of the superficial microhardness of the enamel to the extent that a low concentrate fluoride is required to restore the original level of hardness. [2],[18],[19],[20] Spalding et al. reported that 35% H 2 O 2 had a tendency to promote an increase in density of pits on enamel surface. [9] H 2 O 2 significantly reduces the calcium concentration of enamel surfaces and fracture toughness as compared to carbamide peroxide. [21],[22] Scanning Electron Microscopy (SEM) studies have revealed some changes in enamel morphology and a slight increase in surface porosity after bleaching with H 2 O 2 as well as carbamide peroxide. [22],[23] Atomic Force Microscopy study of the bleached enamel surface revealed that the samples treated with 35% H 2 O 2 showed slightly more number of grooves on their surface than did the samples bleached with 16% carbamide peroxide. [24] These irregularities in surface enamel after bleaching with 35% H 2 O 2 may have increased the susceptibility to re-pigmentation in Group I, thereby adversely affecting the teeth whitening treatment. Though in the oral environment, saliva plays a major role in re-mineralization of enamel by reaction of calcium, phosphate, and fluoride ions with the cations present in the tooth. However, saliva alone was found to be incapable of reversing the changes caused by the bleaching agents on enamel and dentin. [25] Turkun et al. [26] found in his in vitro study that the changes in enamel caused by the bleaching agent took approximately 3 months to disappear. Moreover, this recovery time is certainly long enough and may increase the susceptibility of the bleached dental surface to biofilm formation and discoloration by various stains. [11],[12]


  Conclusion Top


It was concluded from the study that:

  • Carbamide peroxide (16%) used in home bleaching is as effective as H 2 O 2 (35%) used in office
  • Susceptibility to pigmentation increases after bleaching
  • In vitro pigmentation is greater when H 2 O 2 (35%) is used for bleaching in comparison to carbamide peroxide (16%)
  • Further studies should be carried out to see the


In vitro changes after bleaching, as the presence of saliva in the oral cavity may cause re-mineralization or re-hardening of the surface enamel and thereby lesser re-pigmentation.

 
  References Top

1.Greenwall L. Bleaching Techniques in Restorative Dentistry: An Illustrated Guide.Thieme Medical Pub; 1 St Edition edition; 2001. p.1-23.  Back to cited text no. 1
    
2.Lewinstein I, Hirschfeld Z, Stabholtz A, Rotstein I. Effect of hydrogen peroxide and sodium perborate on the micro hardness of human enamel and dentine. J Endod 1994;20:61-3.  Back to cited text no. 2
    
3.de Freitas PM, Turssi CP, Hara AT, Serra MC. Monitoring of demineralized dentin microhardness throughout and after bleaching. Am J Dent 2004;17:342-6.  Back to cited text no. 3
    
4.Worschech CC, Rodrigues JA, Martins LR, Ambrosano GM. In vitro evaluation of human dental enamel surface roughness bleached with 35% carbamide peroxide and submitted to abrasive dentifrice brushing. Pesqui Odontol Bras 2003;17:342-8.  Back to cited text no. 4
    
5.Basting RT, Rodrigues AL Jr, Serra MC. The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time. J Am Dent Assoc 2003;134:1335-42.  Back to cited text no. 5
    
6.Lopes GC, Bonissoni L, Baratieri LN, Vieira LC, Monteiro S Jr. Effect of bleaching agents on the hardness and morphology of enamel. J Esthet Restor Dent 2002;14:24-30.  Back to cited text no. 6
    
7.Faraoni-Romano JJ, Turssi CP, Serra MC. Concentration-dependent effect of bleaching agents on microhardness and roughness of enamel and dentin. Am J Dent 2007;20:31-4.  Back to cited text no. 7
    
8.Tezel H, Atalayin C, Erturk O, Karasulu E. Susceptibility of enamel treated with bleaching agents to mineral loss after cariogenic challenge. Int J Dent 2011;2011:953835.  Back to cited text no. 8
    
9.Spalding M, Taveira LA, de Assis GF. Scanning electron microscopy study of dental enamel surface exposed to 35% hydrogen peroxide: Alone, with saliva, and with 10% carbamide peroxide. J Esthet Restor Dent 2003;15:154-64.  Back to cited text no. 9
    
10.Lewinstein I, Fuhrer N, Chraru N, Cardash H. Effect of different peroxide bleaching regimens and subsequent fluoridation on the hardness of human enamel and dentin. J Prosthet Dent 2004;92:337-42.  Back to cited text no. 10
    
11.Gurgan S, Bolay S, Alacam R. In vitro adherence of bacteria to bleached or unbleached enamel surface. J Oral Rehabil 1997;24:624-7.  Back to cited text no. 11
    
12.Hosoya N, Honda K, Lino F, Arai T, Changes in enamel surfaceroughness and adhesion of Streptococcus mutans to enamel after vital bleaching. J Dent 2003;31:543-8.  Back to cited text no. 12
    
13.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. 13
    
14.Murchinson DF, Charlton DG, Moore BK. Carbamide Peroxide bleaching: Effect on enamel surface hardness and bonding. Oper Dent 1992;17:181-5.  Back to cited text no. 14
    
15.McCracken MS, Haywood VB. Effects of 10% carbamide peroxide on the subsurface hardness of enamel. Quintessence Int 1995;25:21-4.  Back to cited text no. 15
    
16.Titley K, Torneck CD, Smith D. Effect of concentrated hydrogen peroxide solutions on the surface morphology of human tooth enamel. J Endod 1988;14:69-74  Back to cited text no. 16
    
17.McGuckin RS, Babin JF. Meyer BJ Alteration in human enamel surface morphology following vital bleaching. J Prosthet Dent 1992;68:754-60.  Back to cited text no. 17
    
18.Teixeira EC, Ritter AV, Thompson JY, Leonard RH Jr, Swift EJ Jr. Effect of tray-based and trayless tooth whitening system on microhardness of enamel surface and subsurface. Am J Dent 2004;17:433-6.  Back to cited text no. 18
    
19.Ulukapi H. Effect of different bleaching techniques on enamel surface microhardness. Quintessence Int 2007;38:e201-5.  Back to cited text no. 19
    
20.Zantner C, Beheim-Schwarzbach N, Neumann K, Kielbassa AM. Surface microhardness of enamel after different bleaching procedures. Dent Mater 2007;23:243-50.  Back to cited text no. 20
    
21.Tezel H, Ertas OS, Ozata F, Dalgar H, Korkut ZO. Effect of bleaching agents on calcium loss from the enamel surface. Quintessence Int 2007;38:339-47.  Back to cited text no. 21
    
22.Yeh ST, Su Y, Lu YC, Lee SY. Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment. Oper Dent 2005;30:507-15.  Back to cited text no. 22
    
23.Pinto CF, Oliveira Rd, Cavalli V, Giannini M. Peroxide bleaching agent effects on enamel surface microhardness, roughness and morphology. Braz Oral Res2004;18:306-11.  Back to cited text no. 23
    
24.Hegedüs C, Bistey T, Flóra-Nagy E, Keszthelyi G, Jenei A. An atomic force microscopy study on the effect of bleaching agents on enamel surface. J Dent 1999;27:509-15.  Back to cited text no. 24
    
25.Martin JM, de Almeida JB, Rosa EA, Soares P, Torno V, Rached RN, et al. Effect of fluoride therapies on surface roughness of human enamel exposed to bleaching agents. Quintessence Int 2010;41:71-8.  Back to cited text no. 25
    
26.Turkun M, Sevgican F, Pehlivan Y, Aketenu BO. Effects of 10% carbamide peroxide on the enamel surface morphology: A scanning electron microscopy study. J Esthet Restor Dent 2002;14:238-44.  Back to cited text no. 26
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2]



 

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