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Year : 2018  |  Volume : 21  |  Issue : 5  |  Page : 500-504
Effect of different concentrations of carbamide peroxide on the staining susceptibility of resin composites

1 Dental Materials Research Center, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran
2 Dental Student, Student Research Committee, Babol University of Medical Sciences, Babol, Iran
3 Department of Operative, School of Dentistry, Kashan University of Medical Sciences, Kashan, Iran
4 Social Determinants of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran

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Date of Submission23-Feb-2018
Date of Decision11-Mar-2018
Date of Acceptance20-Jun-2018
Date of Web Publication17-Sep-2018


Context: Bleaching can affect the surface properties of resin composites.
Aims: The aim of this study was to evaluate the effect of three regimens of carbamide peroxide (CP) on staining susceptibility of silorane and methacrylate-based resin composites.
Methods: In this study, 80 composite disks were prepared from A2 shade of P90 and Z250 composite resins (40 each). Samples were divided into three test groups based on the CP concentration (10%, 16%, and 22%) and bleached for 14 days. Controls were kept in distilled water. Then, specimens were immersed in a tea solution for 14 consecutive days. A spectrophotometer was used to measure the specimen colors in CIE L*a*b system, initially and after staining. Data were analyzed using SPSS 16 software using two-way ANOVA, t-test, and Tukey honestly significant difference tests at α = 0.05.
Results: The color susceptibility of Z250 samples were significantly affected in groups bleached with 22% CP compared to the controls (P = 0.001). The different concentrations of CP did not affect the staining susceptibility of the P90 samples (P > 0.05).
Conclusions: Bleaching of the tested resin composites did not increase their susceptibility to extrinsic staining in vitro except for the Z250 samples bleached with 22% CP.

Keywords: Carbamide peroxide; resin composite; silorane composite resin; tooth bleaching

How to cite this article:
Esmaeili B, Zenouz GA, Khazaei F, Daryakenari G, Bizhani A. Effect of different concentrations of carbamide peroxide on the staining susceptibility of resin composites. J Conserv Dent 2018;21:500-4

How to cite this URL:
Esmaeili B, Zenouz GA, Khazaei F, Daryakenari G, Bizhani A. Effect of different concentrations of carbamide peroxide on the staining susceptibility of resin composites. J Conserv Dent [serial online] 2018 [cited 2022 Jun 29];21:500-4. Available from:

   Introduction Top

Color stability is an important factor affecting the success of an esthetic restoration.[1],[2] Discoloration of restorative materials may occur by intrinsic and/or extrinsic factors.[1] Intrinsic factors include physicochemical reactions in the matrix of the composite resin. Extrinsic factors include plaque accumulation and adsorption or absorption of superficial pigments.[3],[4] Beverages, such as cola-based soft drinks, black tea, coffee, red wine, and fruit juices have a great influence on color change of both teeth and restorative materials.[3]

Dental bleaching with peroxide-containing materials (carbamide and hydrogen peroxide [HP]) is a conservative esthetic treatment for discolored teeth. The effect is reported to be directly related to the exposure time and the percentage of the active component of the bleaching material. Higher concentrations of HP (35%–40%) are used for in-office bleaching. About 10%–22% carbamide peroxide (CP) is prescribed for home bleaching, with more predictable results.[5]

It is very common to detect teeth restored with different tooth-colored restorations in patients seeking bleaching treatments. Tooth whitening materials can however affect these restorations by destructing their surface components and making them more susceptible to staining. Thus, the resin matrix and/or the fillers of composite resins may be influenced. Previous studies have shown that the resin matrix is readily altered by the acidity of bleaching materials, which endangers the color matching of the restoration with the surrounding dental tissues.[6],[7]

Cooley and Burger have reported that surface roughness of resin composites is increased after bleaching treatment.[8] Turker and Biskin also revealed that bleaching could have a role in increasing the surface roughness of resin composites, which may cause easier staining.[9] In contrast, Celik et al. showed that bleaching of the tested resin composites had no effect on their susceptibility to extrinsic staining in vitro.[10]

Silorane-based composites (SC) were introduced to overcome the disadvantages of previous methacrylate-based composites (MC) due to their lower polymerization shrinkage. The resin matrix is conjoined of oxirane and siloxane molecules enabling lower polymerization shrinkage.[11] According to the authors' knowledge, there is limited research about the effect of the CP on the staining susceptibility of SC restorations.

To accurately determine a shade there are different techniques such as visual colorimetry, spectrophotometry, and digital photograph analyzing. Spectrophotometry is the most reliable method in dental material researches.[12]

The aim of this study was therefore to evaluate the staining susceptibility a microhybrid silorane-based and a microhybrid MC in a tea solution when exposed to three different regimens of CP. The null hypothesis of this study was that bleaching with different concentrations of CP has no effect on the staining susceptibility of the MC or SC.

   Methods Top

In the present in vitro study, two types of resin composite and three concentration of CP were used. The product names, their chemical compositions, and manufacturers are listed in [Table 1].
Table 1: The materials used in the current study

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Specimen preparation

Eighty composite disks were prepared using A2 shade of each material in plastic molds. To prepare the specimens, plastic molds, with an inner diameter of 10 mm and a height of 2 mm, were used. After placing the composite in the mold a transparent strip and a 1-mm glass slab was placed over it and light-cured through the glass slide using a light-curing unit (Astralis 7, Ivoclar vivadent, Liechtenstein) with a light intensity of 750 mW/cm 2 for 20 s, followed by an extra 20 s from each side after removing the disk from the mold to ensure proper polymerization. The upper surfaces of the specimens were polished using polishing disks (sof-lex, 3M, ESPE, USA) from the course to the soft grit, respectively. The specimens were then kept in 37°C distilled water for 24 h, to ensure complete polymerization. Each composite resin group were randomly divided into four subgroups (n = 10), three bleaching groups and one control (n = 10).

Bleaching procedure

Whiteness perfect home bleaching agent (FGM, Brazil) with three CP concentrations (10%, 16%, and 22%) were used in the present study. The bleaching gel was injected with a preloaded syringe on the upper surfaces of the specimens, forming a layer that was 1.5 thick. According to the manufacturers' instructions for each concentration of the bleaching agent, the protocol was as follows:

  1. Specimens were treated with 10% whiteness perfect 4 h/day for 14 days
  2. Specimens were treated with 16% whiteness perfect 3 h/day for 14 days
  3. Specimens were treated with 22% whiteness perfect 1 h/day for 14 days
  4. Samples in the control group were kept at 37°C distilled water for 14 days with no bleaching application.

After each bleaching session, the specimens were rinsed under running water for 1 min to remove the bleaching agent, dried and stored in distilled water at 37°C until the next application. Distilled water was refreshed daily.

Staining procedure

After the bleaching process, all specimens were placed in a 50°C tea solution for 20 min/day for 14 consecutive days. This accounts for three cups of tea in one day, each contacting teeth for 1 min, in a 3 months.[10] The tea solution (Yellow Lable, Lipton, UK) was prepared by immersing two prefabricated tea bags (2 × 2 g) into 500 ml of boiling water for 2 min. Fresh tea solutions were prepared each day.

After each session, the specimens were rinsed with running water for 1 min and stored in 37°C distilled water for the rest of the day.

Color measurements

Vita Easyshade compact spectrophotometer (Vident, USA) was used to measure the specimen colors in CIE L*a*b system. This instrument is a hand-held spectrophotometer that consists of a cordless handpiece. It contains several 1-mm diameter fiberoptic bundles. During the measurement process, the tooth is illuminated by directing the light from white LEDs into the tooth surface.[13] Easyshade measures the spectral reflectance of a color and converts it into L*a*b, where L* describes the luminance reflectance, while a* and b* describe the red–green and yellow–blue color coordinates, respectively. The spectrophotometer's CIE L*a*b* output is based on D65 illuminant. For color assessment, the composites were placed on a white background, and the device was calibrated before each measurement following the manufacturer's instructions. The color was measured in two intervals by a single operator; before bleaching (L1, a1, b1) and after immersion in tea (L2, a2, b2). Three consecutive measurements were done for each sample and average values of 'L', 'a', and 'b' were recorded at each interval. The color change was calculated using the following formula:

ΔE2-1= (L2−L1]2 + [a2−a1]2+ [b2−b1]2

Statistical analysis

Data were analyzed using SPSS16 software (SPSS Inc., Chicago, IL, USA) by two-way ANOVA, Paired t-test and Tukey honestly significant difference tests. The level of statistical significance was set at P < 0.05.

   Results Top

In this study, the effect of composite (F = 8.971, DF = 1, P = 0.004), the effect of bleaching (F = 4.734, DF = 3, P = 0.005), and the interaction of composite-bleaching (F = 3.699, DF = 3, P = 0.016) was statistically significant. ΔE values <3.3 were considered clinically acceptable.[6] [Table 2] shows mean ΔE values of different groups after staining procedure. The highest ΔE value was observed in the Filtek Z250 specimens after bleaching with 22% CP and the lowest ΔE value was in the Filtek Z250 specimens after bleaching with 16%CP.
Table 2: Mean ΔE±standard deviation values of the composite resins after staining procedure

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The 22% CP significantly increased the staining capacity (ΔE) of the Z250 composite disks, in the tea solution, in comparison to the control group (P = 0.02). While 10% and 16% CP only moderately affected the Z250 disks and the color change was not significant compared to the control group [Table 2].

According to [Table 2], the different concentrations of CP did not affect the staining susceptibility of SC (P = 0.792). The color modification of different groups is presented in box plot1 [Graph 1].

In most groups, a reduction was observed in L* value and a* value was increased, inducing a less bright and more red view in the composite resins.

   Discussion Top

In the present study, there were no significant differences in the staining susceptibility of SC samples bleached with different concentrations of CP. However, in the MC group exposed to 22% whitening agent significant staining was revealed compared to the control group; therefore, the null hypothesis was partially rejected.

During standard bleaching treatments, whitening agents contact teeth and restorative materials simultaneously. However, the changes of the restorative materials induced by bleaching are however still not clear. The fact that bleaching agents can affect restorative materials deleteriously remains under debate.[3] Some studies indicate that free radicals produced during bleaching procedure degrade the resinous matrix and disrupt the filler/matrix interface thus increasing the water sorption and filler debonding and changing the surface topography.[14] It was reported that bisphenol A-glycidyl methacrylate (Bis-GMA) resin monomers is more degraded compared to the urethane dimethacrylate resin monomers. Moreover, the filler particles containing quartz or silica are less prone to hydrolytic attack than barium particles. These filler particles on the surface would be dissolved by the HP significantly.[15] An increase in the surface roughness of resin composites after bleaching has been indicated in previous studies [16],[17] Pitacas et al. also observed surface changes of resin composites after bleaching by SEM. They reported superficial cracks and multiple pores, accentuating a separation between resin matrix and fillers.[18] The expected outcome is more staining capacity due to having a rougher surface, after bleaching.[10]

In the present study, whitening agents (10%, 16% or 22%) bleaching treatment had no significant effect on the staining susceptibility of the SC, while the 22% bleaching gel increased the staining susceptibility of the MC. The findings of the current study indirectly are in agreement with the previous studies,[9],[17],[19],[20] which evaluated surface roughness of composites after bleaching.

This staining could be caused by the alterations in the surface of the bleached restorations.[3]

In research by Bahannan 10% CP did not affect the surface roughness considerably while the 20% concentration induced a significantly rougher surface.[21] Moraes et al. also demonstrated a rougher surface for a microhybride composite after exposure to 35% CP gel, while the 10% gel had no diverse effect on the composite.[19]

Similarly, Turker and Biskin found that 10% and 16% CP did not influence the surface roughness of resin composites.[9] Rattacaso et al. and Zuryati et al. had similar results using 16% and 10% CP consecutively.[17],[22] On the other hand, Kim et al. reported increase in surface roughness of resin composites after bleaching with whitening strips; however, the Ra value was <0.30 micron after bleaching, and significant color change did not seen.[23] It seems that concentration of the bleaching material influences the surface roughness of composite resin.

There is also evidence that the lower concentrations of CP release a low amount of free radicals. These can lead to higher surface polymerization and hardness.[24]

Kurtulmus-Yilmaz et al. revealed 10% CP and HP caused in an unacceptable color change of resin composites, but they did not have any staining procedure.[13] Yu et al. found that bleached composite resins show more staining than unbleached ones when in contact with herbal tea. However, it is important to note that their bleaching material was 15% CP used 8 h daily.[3] Celik et al. showed bleaching of the resin composites did not increase their susceptibility to extrinsic staining in vitro,[10] but de Andrade et al. reported significant staining of nanofilled composites after bleaching. Their staining solution was red wine and coffee. Apart from the pigments found in these media, the alcoholic content of the red wine and the coffee temperature used in their study may have softened the organic matrix of the composite and induced staining.[4] Differences in the bleaching protocols and the composition and concentration of the investigated bleaching agents may explain such contradictory findings.

In this study, upper a* and L* levels were seen in MC group bleached after immersion in tea solution.

A shift of the L* to negative and a* to positive indicate a perceptible darkening of the composite. The change in the L* and a* values was however consistent with Yu et al.'s study.[3]

It can be concluded that not only the concentration of a bleaching material is important when it comes to the staining susceptibility of a resin composite but also the composite itself and its composition, could yield it more vulnerable after home bleaching. Since in vitro environment cannot truly depict the oral cavity and restorative materials are subjected to saliva in the mouth and not distilled water more studies are recommended in this regard.

   Conclusion Top

None of the concentrations of carbamide peroxide had any effect on the staining susceptibility of the silorane based composite, but the bleaching of the methacrylate based composite with the 22% carbamide peroxide increased its susceptibility to extrinsic staining.


The authors would like to thank Babol University of Medical Sciences for their financial support.

Financial support and sponsorship

This study was financially supported by Babol University of Medical Sciences.

Conflicts of interest

There are no conflicts of interest.

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Correspondence Address:
Dr. Ghazaleh Daryakenari
Department of Operative, School of Dentistry, Kashan University of Medical Sciences, Kashan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCD.JCD_59_18

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