|Year : 2016 | Volume
| Issue : 1 | Page : 11-16
Effects of hydrogen peroxide-based mouthwashes on color changes of stained direct composite resins
Muhammet Karadas1, Murat Alkurt2, Zeynep Yesil Duymus2
1 Department of Restorative Dentistry, Recep Tayyip Erdogan University, Rize, Turkey
2 Department of Prosthodontics, Recep Tayyip Erdogan University, Rize, Turkey
|Date of Web Publication||9-Feb-2016|
Dr. Muhammet Karadas
Department of Restorative Dentistry, Faculty of Dentistry, Recep Tayyip Erdogan University, Rize - 53100
Source of Support: None, Conflict of Interest: None
Objective: The aim of this study was to evaluate the effect of three mouthwashes on color changes of three composite resins stained with tea. Materials and Methods: Fifty specimens were prepared for each of the three composite resins [Clearfil Majesty Esthetic (CME), Filtek Z250 (Z25), and Charisma (CH)], and the specimens were then stained in a tea solution. Each composite group was randomly divided into five subgroups (n = 10) according to the product applied: Distilled water (DW) (negative control); Crest 3D White mouthwash (CR); Listerine whitening mouthwash (LS); Scope White SC mouthwash (SC), and Opalescence PF gel (OP) (10% carbamide peroxide, positive control). The color of the specimens was measured with a spectrophotometer at baseline, after staining, and on the 7th, 28 th , and 56 th days of the treatment period. The color differences (ΔE) were analyzed with a three-way analysis of variance (ANOVA), followed by Tukey's test (P < 0.05). Results: Compared with the clinically acceptable threshold unit, the level of staining on all the composite resins was considerably high (ΔE > 3.3). The composite resin, mouthwash, immersion time, and their interaction had a significant effect on the color change procedure (P < 0.05), but the immersion time × mouthwash × composite did not. Conclusion: The discoloration of the specimens after immersion in the mouthwashes decreased significantly over time. Only the staining of the CME specimens treated with CR, LS, and OP decreased to a clinically acceptable level at the end-treatment period.
Keywords: Carbamide peroxide, color change, composite resins, mouthwashes, spectrophotometry
|How to cite this article:|
Karadas M, Alkurt M, Duymus ZY. Effects of hydrogen peroxide-based mouthwashes on color changes of stained direct composite resins. J Res Dent 2016;4:11-6
|How to cite this URL:|
Karadas M, Alkurt M, Duymus ZY. Effects of hydrogen peroxide-based mouthwashes on color changes of stained direct composite resins. J Res Dent [serial online] 2016 [cited 2020 Sep 28];4:11-6. Available from: http://www.jresdent.org/text.asp?2016/4/1/11/176018
| Introduction|| |
Composite resins are commonly used in restorative dentistry because they have excellent esthetic properties and can be bonded to dentin and enamel. Their increasing popularity can be ascribed to esthetic demands from patients for tooth-colored restorative materials.  Esthetic restorative materials should mimic the appearance of natural teeth and match their color. Although the initial esthetic outcome may be excellent, one major disadvantage of composite resins is discoloration after prolonged exposure to conditions in the mouth. ,, The change in color and the loss of shade match with the surrounding tooth structure cause esthetic problems and may lead to the replacement of restorations. This is a very expensive and time-consuming process. ,
Both intrinsic and extrinsic factors may cause discoloration of tooth-colored restorations. Intrinsic factors include the composition of the organic polymer matrix; the amount, size, and nature of the inorganic filler; the quantity of the photo initiator or inhibitor; the bond between the polymer matrix and fillers; and the rate of polymerization. Extrinsic discoloration is due to exposure to food pigments, ultraviolet (UV) radiation, temperature changes, and water absorption. ,
The color stability of composite materials has been examined by artificial aging and by immersion in colored solutions, such as tea, coffee, and red wine. , A number of factors, such as incomplete polymerization, water sorption, chemical reactivity, diet, oral hygiene, and surface roughness of the restoration, can influence the degree of discoloration. The structure of the composite resin and the characteristics of the particles have a direct impact on the surface roughness and susceptibility to extrinsic discoloration.  A previous study reported that hydrophobic materials showed better color stability and stain resistance than hydrophilic materials. 
Mouthwashes are very popular oral hygiene agents. They can chemically control cariogenic biofilms and aid remineralization. Due to the rise in patients' concerns about the esthetic appearance of their teeth in recent years, the number of mouthwash products containing hydrogen peroxide has significantly increased.  Mouthwashes that include a low concentration of hydrogen peroxide and sodium hexametaphosphate can help prevent stains and fight plaque buildup.  Previous studies examined the effects of bleaching agents on composite resin materials. , However, there is little information available on the impact of mouthwashes on stained direct composites.
The aim of this in vitro study was to evaluate color changes in three stained universal composite resins immersed for different times in three hydrogen peroxide-based mouthwashes compared with those immersed in a 10% carbamide peroxide bleaching gel. The null hypotheses were that:
- The mouthwashes would not affect the color stability of the composite resins,
- The immersion time in the mouthwashes would not affect the results,
- There would be no significant color differences among the mouthwashes used, and
- There would be no significant color differences among the composite resins tested.
| Materials and Methods|| |
The details of the materials used in this study are presented in [Table 1] and [Table 2]. Fifty specimens from each universal composite resin [Clearfil Majesty Esthetic (CME), Filtek Z250 (Z25), and Charisma (CH)], A2 shade, were prepared using a polytetrafluoroethylene cylindrical mold (10 mm in diameter and 2 mm in depth). Each composite resin was loaded into the mold, fixed on a glass slide, and covered with a transparent Mylar strip (100 universal strips, Alfred Becht, Offenburg, Germany). Excess materials were then removed by applying pressure on another glass slide placed on the Mylar strip to obtain a flat surface. The composite resins were polymerized with a light-emitting diode (Elipar TM Freelight2, 3M ESPE, St. Paul, MN, USA) according to the manufacturer's recommended cure time. The power output of the light unit was checked using a power meter (Hilux, Benlioğlu Dental, Ankara, Turkey) to maintain the light intensity at 800 mW/cm2 . The specimens were removed from the molds, and the top and bottom surfaces of the composites were polished with finer grit (Sof-Lex, 3M ESPE, St. Paul, MN, USA) for 10 s. The polishing process was conducted using a low-speed handpiece under dry conditions. To complete the polymerization, the specimens were stored in distilled water and dark containers at 37°C for 24 h.
|Table 2: Composition of mouthwashes and bleaching gel used in this study |
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The prepared composite specimens were immersed for 7 days in a tea mixture, which was prepared by brewing 3.5 g of black tea (Çaykur, Altinbaş Tea, Rize, Turkey) in 100 mL of boiled distilled water for 10-12 min. The specimens were then washed with running distilled water for 1 min. Fifty stained specimens per composite resin were then randomly divided into five different groups (n = 10) according to the immersion solution: Distilled water (DW group, negative control), Crest 3D White whitening mouthwash for 4 min daily for 56 days at 37°C (CR group), Listerine whitening mouthwash for 4 min daily for 56 days at 37°C (LS group), Scope White SC whitening mouthwash for 4 min daily for 56 days at 37°C (SC group), and a positive control group, with the specimens placed in glass containers filled with bleaching gel Opalescence PF (10% carbamide peroxide) for 4 h daily at 37°C, for 14 days (OP group). All the specimens were immersed in distilled water in dark containers at 37°C for the rest of the day. After the completion of bleaching with carbamide peroxide, the specimens were immersed in distilled water until the end of the experiment.
One trained operator used a digital spectrophotometer (VITA Easyshade Advance, Zahnfabrik, Bad Säckingen, Germany) to measure the color of each specimen in standardized daylight against a standard white background. The spectrophotometer was calibrated according to the manufacturer's recommendations. The spectrophotometric data were recorded according to the color system recommended by the Commission international de l'éclariage (CIELAB-CIE1976 L*a*b*). The L* scale indicates the amount of lightness in a specimen and varies from black (0) to white (100). The a* scale indicates the amount of red (+a*) and green (−a*) in the specimens, and the b* scale denotes the amount of yellow (+b*) and blue (−b*). 
The color measurements were performed at different times: Baseline (before staining the prepared composite specimens); after immersion in the tea solution; and after 7 days, 28 days, and 56 days of whitening. The color difference between two measurements was calculated using the following formula: 
where the subscripts 0 and 1 denote the initial and final measurements, respectively.
When ΔE values are below 3.3 units, the difference is clinically acceptable.  Color differences in this study were calculated using baseline color parameters at each measurement time: After staining (T0), and on the 7 th (T1), 28 th (T2), and 56 th (T3) days of the treatment period. In the OP group, the color differences were calculated on days 7, 14 (recorded as 28 days in this study), and 56 of the treatment period.
PASW Statistics software 18 (SPSS Inc., Chicago, IL, USA) was used to analyze the data. Parametric tests were used, as the data were normally distributed. After staining, the data obtained were assessed by a one-way analysis of variance (ANOVA). After the whitening period, analysis of the mean ΔE values was performed with a three-way repeated-measure ANOVA and Tukey's multigroup comparison test at P < 0.05.
| Results|| |
The color changes (ΔE) of all the composite resins after immersion in the tea solution are represented in [Figure 1]. The level of the discoloration was clinically unacceptable for all the composite resin types (ΔE > 3.3). The level of staining differed significantly among the composite resin groups (P < 0.001). The results of the repeated-measure ANOVA revealed that the immersion time in the mouthwashes, composite, mouthwash used, and the interactions among them significantly affected the ΔE values. However, there was no statistically significant interaction between the immersion time × mouthwash × composite (P = 0.076, [Table 3]).
|Figure 1: Mean color changes of composites after immersion in tea solution|
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Immersion time in the mouthwashes was a significant factor in the color change of each composite resin. After the completion of the whitening treatments, the color of the CME specimens in the OP, CR, and LS groups returned to the baseline (ΔE < 3.3). However, the color changes between the whitening and baseline in the Z25 and CH specimens were higher than the clinically acceptable ΔE value (3.3). All the mouthwashes were significantly more effective than the negative control group in terms of the color recovery of the stained composites. After completion of the treatments, the color changes of the tested composite resins in the mouthwashes were significantly different. The ΔE values of the CH specimens treated with the whitening products were not significantly different, whereas those of the Z25 and CME specimens were significantly different. After 56 days of immersion, there was no significant difference between the LS mouthwash and OP bleaching gel in the color change of any of the tested composite resins [Table 4] (P > 0.05).
|Table 4: The means ± standard deviations of color change (ΔE) for each composite resin after immersion in each mouthwash |
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| Discussion|| |
The three-way repeated-measure ANOVA revealed that three main factors were significant: The immersion time, mouthwash and composite, and their interaction. However, there was no significant interaction between the immersion time × immersion solution × composite. The null hypothesis that the mouthwash, composite, and immersion time would have no effect on the color change of the composite resin was rejected.
The color stability of composite resin restorations throughout their functional lifetime is one of the most important features of esthetic restorative materials in terms of the durability of the treatment. The color stability of different composite resin materials has been reported to be inconsistent.  The staining susceptibility of a composite resin may be attributed to its resin matrix or filler type. A previous study found that the effect of the resin matrix on staining susceptibility was associated with the hydrophobicity and water absorption properties of the resin matrix.  As reported elsewhere, inorganic fillers can debond from the resin matrix and leave a void, hence increasing the surface roughness.  The size and composition of filler particles were previously shown to affect the roughness of composite resin materials,  with smaller voids left on the surface of nanohybrid composite resins compared to other composite materials because of the smaller particles of the former. , Karaarslan et al.  compared the effects of different polishing methods on the color stability of different composite resin materials after accelerated aging. They reported the lowest ΔE* values for a microhybrid resin but found no significant differences in these values among microhybrid and nanohybrid resins except for BisCover glaze material (Bisco, Schaumburg, IL, USA). The results of our study showed that the staining susceptibility of a nanohybrid composite, CME, was significantly lower than that of the other composites. As the composite resins examined in this study contained different amounts of filler and different compositions, the staining susceptibility of these materials after immersion in the tea solution was significantly different.
Tea contains a yellow colorant and causes severe discoloration in composite resins by absorption and adsorption. In previous studies, tea produced more severe staining in tooth-colored restorative materials than did cola-based beverages. , In the present study, DW was selected as the negative control group because water is a common component of both solid and liquid diets. A previous study demonstrated that although water helped to dissolve stains and ameliorated color changes in composite resins, it did not fully dissolve hydrophobic molecules.  In the present study, the level of staining of the CH and Z25 composites significantly decreased with increased time when immersed in DW but that of the CME composites did not change, which may be attributed to various factors, such as the filler content, filler type, and water solubility.
The findings of the current study demonstrated that the color of the tea-stained CME specimens in the CR and LS groups returned to baseline after 56 days of immersion (ΔE < 3.3). Only the mean ΔE values of the CME composite specimens bleached with the at-home bleaching gel decreased to an acceptable level after 14 days of the treatment. Villalta et al.  examined the effects of bleaching systems on color changes of nanocomposite and microhybrid resins stained with different solutions and reported that the colors of both types of composite specimens returned to the baseline. On the other hand, in a study of the effectiveness of mouthwashes in the color recovery of a stained microhybrid composite, Harorli et al.  found that the immersion time in the mouthwash and the brand of mouthwash had a significant effect on the color recovery of the stained composite.
The mouthwashes tested in this study included whitening products containing a low concentration of hydrogen peroxide (1-2%), sodium hexametaphosphate, and pyrophosphates. These products work either by bleaching or by removal and control of stains. , The actual teeth-whitening mechanism of hydrogen peroxide is not fully known, but it is thought to be the result of an oxidation reaction in which the pigment molecules are broken down. , Sodium hexametaphosphate has the ability to bind easily and reduce stains, thereby helping to whiten and protect the surface of the teeth from new stains. 
A previous study suggested that the color change of composite resins after the use of whitening agents was due to extrinsic cleansing of specimens, not an intrinsic color change.  In the present study, the mouthwashes were effective in removing stains from the composite resins over time. At the end of the 56-day treatment period, there were no statistically significant differences in the color change of any of the composites tested, irrespective of the type of mouthwash used. Only the Listerine mouthwash was as effective as the at-home bleaching gel in removing stains from all the composite resins tested.
Carbamide peroxide (10%) was chosen as the positive control group because home bleaching methods are commonly used in dental practice to whiten teeth. , Home bleaching gel (10% carbamide peroxide) contains 3.5% hydrogen peroxide, and this percentage is greater than that found in the mouthwashes examined in this study. A previous study of two different mouthwashes containing hydrogen peroxide reported that they had a bleaching effect.  Home bleaching gels in trays have limited contact with the teeth and gums. In contrast, mouthwash is in direct contact with all the oral mucosa. 
In the present study, the immersion time in the mouthwash had a significant influence on stain removal from the composite. However, the continuous use of a mouthwash can cause side effects, such as mucosa desquamation, ulceration, inflammation, allergic reactions, and burning mouth sensation.  These side effects can be increased if the amount of mouthwash that a person uses exceeds that recommended by the manufacturer.
Mouthwashes have become extremely popular teeth-whitening agents because of their ease of application, low cost, and wide availability.  Given their recent widespread popularity, it is important to consider their effect on the esthetic appearance of composite resins in teeth. In the present study, the ability of the same mouthwash or bleaching agent to remove stains differed depending on the composite type. This finding can be explained by the different compositions of the composites tested in this study. Organic polymer matrices of composite resin materials are prone to chemical degradation induced by the acidic component of whitening products. This may compromise the color-matching of composite restorations to an adjacent tooth.  As reported in other studies, whitening agents can remove stains from resin composites and effectively whiten teeth, but they cannot whiten resin composites. , Consequently, after using whitening products, the color of the composite resin restoration may not match that of the surrounding whitened teeth. Thus, patients should be informed that replacement of composite restorations in teeth may be required after use of whitening mouthwash, depending upon the extent of the color change.
This in vitro study evaluated the color stability of three different composite resin materials after immersion in only tea solution. The consumption of different staining substances, immersion time in staining solution, and absence of cleaning or brushing of the specimens during the study are significant factors affecting the color stability of composite materials.  Therefore, additional studies should be conducted to evaluate the effect of mouthwashes in the composite materials under the oral environment and different storage conditions.
| Conclusion|| |
In conclusion, immersion in a tea solution caused severe discoloration of the three composite types studied. The nanohybrid composite (CME) showed the least discoloration, followed by the microhybrid (Z25) and hybrid (CH) composites. The discoloration of the specimens after immersion in the mouthwashes decreased significantly over time. The color alteration (ΔE) in all the composite groups differed significantly at the time intervals evaluated compared to the DW group. Only the composites treated with the LS mouthwash showed a similar color change to that of the OP group. The staining of the CME composite treated with CR and LS decreased to the clinically acceptable level after the 56-day period.
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[Table 1], [Table 2], [Table 3], [Table 4]