Property changes in resin composite exposed to mouth rinses during 10% carbamide peroxide bleaching

Abstract

Aim  This in vitro study evaluated the effects of different mouth rinses in combination with 10% carbamide peroxide bleaching gel on the properties of resin composite.

Methods  Cylindrical specimens of a nanofilled resin composite (n = 12) were allocated to four groups: distilled water (control, C), mouth rinse with essential oils (EO), mouth rinse with essential oils and alcohol (EO+A), and mouth rinse with essential oils, alcohol, and hydrogen peroxide (EO+A+HP). Samples were bleached daily for 14 days with 10% carbamide peroxide gel for 4 hours and immersed in 5 mL of the assigned mouth rinse before and after bleaching. Surface microhardness (SMH), surface roughness (Ra), and color changes (ΔL^*, Δa^*, Δb^*, ΔE_ab, and ΔE₀₀) were assessed at baseline (T1) and post-treatment (T2). Data were analyzed using generalized linear mixed models and Kruskal–Wallis/Dunn tests.

Results  All groups exhibited decreased SMH and increased Ra at T2. No significant differences in SMH were observed among groups, whereas Ra was highest in the EO+A+HP group. The EO+A and EO+A+HP groups showed greater Δa^* and ΔE₀₀ values compared with the control.

Conclusion  Mouth rinses used during 10% carbamide peroxide bleaching increase roughness, reduce microhardness, and alter resin composite color, depending on their active ingredients.

Keywords
Composite resins; Mouthwashes; Tooth bleaching; Color; Surface properties; Hardness

Introduction

One effective, affordable, and practical approach to dental bleaching is the at-home technique, performed by the patient under a dentist’s supervision¹,². This technique employs low-concentration bleaching agents, such as carbamide peroxide, which are applied repeatedly to achieve optimal results³.Upon contact with water, carbamide peroxide decomposes into hydrogen peroxide and urea. Hydrogen peroxide, the main active compound in bleaching gels, oxidizes various organic and inorganic molecules, leading to tooth color changes⁴.

Hydrogen peroxide in bleaching gels interacts not only with pigment molecules but also with any surface it contacts. During at-home bleaching, it can affect both the dental hard tissues and restorative materials, leading to potential chemical and physical interactions. As a result, the impact of hydrogen peroxide on resin composites has been widely investigated⁵-⁷. Research indicates that exposure to bleaching gels can increase surface roughness, reduce microhardness, weaken the adhesive interface, and alter the color and translucency of resin-based materials⁶,⁸,⁹.

During at-home bleaching, other substances—such as mouth rinses used for oral hygiene—can also come into contact with direct restorations, potentially interacting with the resin composite. Mechanical plaque removal is an effective strategy for preventing biofilm-related oral diseases, including caries, gingivitis, and periodontal disease¹⁰-¹². However, mouth rinses are commonly used by patients, often without professional supervision¹³. While dentists may recommend specific formulations, many individuals select mouth rinses based on personal preference or marketing claims. These products are among the most widely available over-the-counter oral care items, easily found in supermarkets, pharmacies, and online stores worldwide¹⁴,¹⁵.

Many commercially available mouth rinses contain ingredients such as water, antimicrobial agents, salts, preservatives, essential oils, alcohol, and, in the case of whitening formulations, hydrogen peroxide¹⁶. The effects of these components on the polymeric matrix of resin composites have been widely discussed in the literature¹⁷. Specifically, alcohol can soften resin composite surfaces¹⁸,¹⁹, reducing hardness and increasing wear over time²⁰,²¹. Additionally, alcohol in mouth rinses enhances the sorption and solubility of resin composites compared to alcohol-free formulations²², and has been associated with color alterations in the material²³. Essential oils have also been shown to compromise the structural integrity of resin composites, contributing to reduced microhardness and increased surface roughness²³. Whitening mouth rinses can further intensify these effects, promoting additional surface degradation and roughness in resin composites²³.

To date, no study has assessed the impact of various mouth rinse components on resin composites during at-home bleaching with 10% carbamide peroxide, despite the fact that patients often use these products concurrently. Moreover, while the structural changes induced by bleaching on resin composites are well documented, it remains unclear whether the simultaneous use of mouth rinses could exacerbate these effects. Understanding these interactions is clinically relevant, as it can help dental practitioners provide evidence-based recommendations to patients who use mouth rinses during at-home bleaching, thereby ensuring both the effectiveness of bleaching and the longevity of restorative materials.

Therefore, the aim of this in vitro study was to evaluate the effects of mouth rinses with different active agents on resin composites during at-home bleaching with 10% carbamide peroxide, focusing on color stability, surface microhardness, and surface roughness. The null hypotheses tested were that: (1) mouth rinses would not affect the surface microhardness of the resin composite during at-home bleaching; (2) mouth rinses would not induce changes in surface roughness during at-home bleaching; and (3) mouth rinses would not alter the color of the resin composite during at-home bleaching.

Material and Method

Experimental design

All groups underwent the same bleaching protocol, with the only difference being the type of mouth rinse used. The mouth rinses, which differed in their active ingredients, represented one experimental factor with four levels: distilled water (control group), mouth rinse containing essential oils – EO (Listerine Cool Mint Zero Alcohol, Johnson & Johnson, São Paulo, SP, Brazil); mouth rinse containing essential oils and alcohol – EO+A (Listerine Cool Mint, Johnson & Johnson, São Paulo, SP, Brazil); and mouth rinse containing essential oils, alcohol, and hydrogen peroxide – EO+A+HP (Listerine Whitening Extreme, Johnson & Johnson, São Paulo, SP, Brazil). The detailed composition of each product is presented in Table 1.

Table 1
Composition of the materials that were used in this study according to the manufacturer’s information.

Materials	Manufacturer	Composition	Color	Application time	pH
Distilled water	--	Distilled water	--	30 seconds	7.05
Listerine Cool Mint Zero Alcohol	Johnson & Johnson (São Paulo, Brazil)	Water, sorbitol, propylene glycol, sodium lauryl sulfate, poloxamer 407, eucalyptol, benzoic acid, Aroma (d-limonene), thymol, methyl salicylate, sodium benzoate, menthol, CI 42053	FD&Ca Blue No. 1 (Cl 42090 – brilliant blue FCF)	30 seconds	3.99
Listerine Cool Mint	Johnson & Johnson (São Paulo, Brazil)	Water, sorbitol, alcohol, poloxamer 407, benzoic acid, sodium saccharin, eucalyptol, aroma (d-limonene), thymol, methyl salicylate, sodium benzoate, menthol, CI 42053.	FD&Ca Blue No. 1 (Cl 42090 – brilliant blue FCF)	30 seconds	3.92
Listerine Whitening Extreme	Johnson & Johnson (São Paulo, Brazil)	Water, alcohol, hydrogen peroxide 2.5%, aroma, poloxamer 407, sodium saccharin, menthol, phosphoric acid, disodium phosphate, sodium fluoride (100 ppm Fluoride), sucralose.	FD&Ca Blue No. 1 (Cl 42090 – brilliant blue FCF)	60 seconds	3,45
Whiteness Perfect 10%	FGM (Joinville, Brazil)	Carbamide peroxide 10%, potassium nitrate, sodium fluoride, carbopol, propylene glycol, deionized wate	--	4 hours	--
Filtek Z350 XT enamel	3M Oral Care (St. Paul, MN, USA)	Bis-GMA, UDMA, TEGDMA, PEGDMA, Bis-EMA, Zirconia and silica nanoparticles	B1	--	--

• ^a US Federal Food, Drug, and Cosmetic Act

Additionally, time was included as a experimental factor for the surface roughness and microhardness analyses (evaluated at baseline and after treatment). The analyses performed included surface microhardness (SMH), surface roughness (Ra), and color parameters (ΔL^*, Δa^*, Δb^*, ΔE_ab, and ΔE₀₀).

Sample preparation

A total of 48 cylindrical specimens of a nanofilled resin composite (Filtek Z350 XT Enamel, 3M Oral Care, St. Paul, MN, USA), shade B1, were prepared for color and surface roughness testing, measuring 7.0 mm in diameter and 2.0 mm in thickness. An additional 48 specimens measuring 3.0 mm in diameter and 2.0 mm in thickness were prepared for surface microhardness evaluation.

Shade B1 was selected due to its high luminosity, which makes potential color changes more perceptible. The enamel-type composite was chosen to closely simulate the outer layer of a clinical dental restoration. Separate specimens were prepared for microhardness analysis to avoid surface damage or interference with other measurements, since this test produces permanent indentations.

The resin was inserted into a silicone mold in a single increment, covered with a polyester strip and a glass slide, and subjected to a 500 g weight for 30 seconds to ensure a uniform surface. Polymerization was performed using a LED curing unit (Valo, Ultradent Products Inc., South Jordan, USA). After curing, the specimens were stored for 24 hours at 37°C and 100% relative humidity.

The top surface of each specimen was sequentially polished for 1 minute with #600, #1200, and #4000 silicon carbide sanding discs (Buehler Ltd, Lake Bluff, IL, USA), followed by polishing with felt discs and diamond pastes (3 µm, ½ µm, and ¼ µm). Finally, the resin surfaces were coated with a colorless, acid-resistant varnish to restrict treatment exposure to only one surface, simulating intraoral clinical conditions.

Application of mouth rinses and bleaching

All specimens were stored at 37°C ± 2°C and 100% relative humidity throughout the experiment. Bleaching was performed over 14 consecutive days using a 10% carbamide peroxide gel (Whiteness Perfect 10%, FGM, Joinville, Brazil). The gel was applied to completely cover the top surface of each specimen. After each application, the specimens were stored at 37°C ± 2°C for 4 hours to simulate intraoral conditions. Subsequently, the specimens were rinsed with distilled water for 1 minute to remove any residual gel and then dried with absorbent paper.

Each specimen was exposed to 5 mL of mouth rinse or distilled water twice daily—once before and once after bleaching gel application—throughout the 14-day period, with agitation at 100 rpm at room temperature²⁴. This exposure regimen followed the manufacturer’s recommendations. The 14-day protocol was chosen to represent the typical duration of mouth rinse use per bottle. After each exposure, specimens were rinsed with distilled water for 10 seconds to remove residues.

Surface microhardness

Surface microhardness was measured at baseline (T1) and after treatment (T2). A Knoop indenter with a 25 g load applied for 5 seconds was used (HMV-2000, Shimadzu, Tokyo, Japan). Five indentations were made per specimen, spaced 100 µm apart, and the mean value was calculated to obtain the Knoop Hardness Number (KHN).

Surface roughness

Surface roughness (Ra) was also evaluated at T1 and T2 using a contact profilometer (Surf-Corder 1700, Kosaka, Tokyo, Japan). Measurements were taken in three equidistant directions on each specimen, using a cutoff value of 0.25 mm, a reading length of 1.25 mm, and a scanning speed of 0.1 mm/s. The mean of the three readings was recorded as the Ra value for each specimen.

Color analyses

Color measurements were performed at T1 and T2. Specimens were positioned in a Teflon holder inside a standardized light chamber (GTI Mini Matcher MM1e, GTI Graphic Technology, Newburgh, NY, USA) to ensure consistent illumination. Color readings were obtained using a spectrophotometer (Konica Minolta CM-700d, Konica Minolta Investment, Shanghai, China). Data were recorded according to the CIELAB color system, and color differences (ΔL^*, Δa^* and Δb^*) were calculated. The total color difference (ΔE^*_ab) was determined using the equation: $\Delta E_{\mathrm{ab}}^{\ast }=\left(\right[L1-L0{]}^2+[a1-a0{]}^2+{[b1-b0{]}^2)}^{1/2}$¹. The ΔE₀₀ values were calculated using the formula:

$\Delta E_{00}={[{\left(\frac{\Delta L^{\prime }}{K_L{S}_L}\right)}^2+{\left(\frac{\Delta C^{\prime }}{K_C{S}_C}\right)}^2+{\left(\frac{\Delta H^{\prime }}{K_H{S}_H}\right)}^2+R_T\left(\frac{\Delta C^{\prime }}{K_C{S}_C}\right)\left(\frac{\Delta H^{\prime }}{K_H{S}_H}\right)]}^{1/2}$

Statistical analyses

Descriptive and exploratory analyses were performed for all variables. Microhardness and surface roughness data were analyzed using generalized linear mixed models (GLMM) for repeated measures over time. Color variation data were evaluated using the Kruskal–Wallis test, followed by Dunn’s post hoc test. All analyses were conducted using the R statistical software (R Foundation for Statistical Computing, Vienna, Austria), with the significance level set at α = 0.05.

Result

Surface microhardness

The results of the surface microhardness analysis are presented in Table 2.

Table 2
Mean (standar deviation) of surface microhardness (SMH) as a function of group and time.

Group	Time
	Initial (T1)	Final (T2)
Distilled water	89.73 (3.29) Aa	71.17 (3.13) Ba
Mouth rinse with essential oils	88.03 (3.70) Aa	70.90 (4.56) Ba
Mouth rinse with essential oils and alcohol	87.67 (3.36) Aa	72.32 (3.99) Ba
Mouth rinse with essential oils, alcohol, and hydrogen peroxide	88.56 (3.94) Aa	71.80 (3.72) Ba

• Different letters (capital letters horizontally and lowercase letters vertically) indicate statistically significant differences (p≤0.05). p(group)<0.0001; p(time)<0.0001; p(interaction)<0.0001.

When comparing the two time points within each group, all groups exhibited a statistically significant reduction in microhardness from the initial to the final measurement (p < 0.05).

However, no significant differences were observed among the groups at either time point (p > 0.05).

Surface roughness

The results of the surface roughness analysis are shown in Table 3.

Table 3
Mean (standar deviation) of surface roughness (Ra) as a function of the group and time.

Group	Time
	Initial (T1)	Final (T2)
Distilled water	0.07 (0.01) Ba	0,09 (0.01) Ad
Mouth rinse with essential oils	0.07 (0.01) Ba	0,26 (0.01) Ac
Mouth rinse with essential oils and alcohol	0.07 (0.01) Ba	0,29 (0.01) Ab
Mouth rinse with essential oils, alcohol, and hydrogen peroxide	0.07 (0.01) Ba	0,31 (0.01) Aa

• Different letters (capital letters horizontally and lowercase letters vertically) indicate statistically significant differences (p≤0.05). p(group)<0.0001; p(time)<0.0001; p(interaction)<0.0001.

Within-group comparisons revealed that all groups showed a statistically significant increase in surface roughness between the initial and final measurements (p < 0.05).

At the final time point, the highest roughness values were observed in the group exposed to the mouth rinse containing alcohol, essential oils, and hydrogen peroxide, whereas the lowest values were recorded in the distilled water (control) group (p < 0.05).

Color analyses

The results of the color analysis are presented in Tables 4 and 5.

Table 4
Median (minimum and maximum value) of color analysis between the initial and post-rinse times according to the group.

Group	∆ L	∆ a	∆ b
Distilled water	-0.54 (-2.18; 0.42) ab	0.87 (0.65; 1.29) b	-0.66 (-1.09; 0.38) a
Mouth rinse with essential oils	-0.20 (-1.03; 0.11) a	1.15 (1.00; 1.62) ab	-0.37 (-0.73; 0.04) a
Mouth rinse with essential oils and alcohol	-0.57 (-2.25; -0.05) ab	1.28 (-3.36; 2.32) a	-0.35 (-1.21; 0.80) a
Mouth rinse with essential oils, alcohol, and hydrogen peroxide	-0.87 (-1.37; 0.16) b	1.28 (1.03; 1.60) a	-0.17 (-1.17; 2.63) a
p-value	0.0097	0.0047	0.5516

• Distinct vertical letters indicate statistically significant differences (p≤0.05).

Table 5
Median (minimum and maximum value) of color variation (∆Eab and ∆E00) according to the group.

Group	∆ Eab	∆ E00
Distilled water	1.30 (0.94; 2.41) ab	1.29 (1.08; 1.93) b
Mouth rinse with essential oils	1.23 (1.05; 2.05) b	1.51 (1.3; 2.27) ab
Mouth rinse with essential oils and alcohol	1.89 (1.22; 3.53) a	1.96 (1.25; 4.07) a
Mouth rinse with essential oils, alcohol, and hydrogen peroxide	1.63 (1.25; 3.08) a	1.83 (1.54; 2.26) a
p-value	0.0027	0.0014

• Distinct vertical letters indicate statistically significant differences (p≤0.05).

No statistically significant differences were found among the mouth rinse groups and the distilled water group for ΔL^* and Δb^* values (p > 0.05). However, for ΔE^*_ab, the alcohol-free mouth rinse group exhibited lower color change values, differing significantly from all other groups (p < 0.05).

Regarding Δa^* and ΔE₀₀, both the mouth rinse containing alcohol and essential oils and the mouth rinse containing alcohol, essential oils, and hydrogen peroxide showed higher values, which were significantly different from the distilled water group (p < 0.05).

Discussion

Hardness is a material’s ability to resist permanent surface indentation or penetration, and it is closely linked to several properties such as strength, ductility, elastic stiffness, plasticity, strain, toughness, viscoelasticity, and viscosity. These factors are critical for the clinical durability of dental restorations, as composite resins in the oral cavity frequently interact with opposing dental structures or materials²⁵,²⁶. In this study, the microhardness results demonstrated that dental bleaching leads to a decrease in the microhardness of the resin composite, with all groups showing a statistically significant difference between the initial and final times. This reduction in hardness may be attributed to the action of the bleaching gel.

A 10% carbamide peroxide solution contains between 3.0 and 3.5% hydrogen peroxide²⁷. Hydrogen peroxide generates free radicals that can cause oxidative cleavage of polymer chains, leading to the chemical softening of dental materials¹,²⁸. This finding aligns with existing literature, which indicates that composite resins subjected to dental bleaching may experience a reduction in surface microhardness²⁹,³⁰. Additionally, the higher concentration of TEGDMA in the composite resin used in this study may make the resin matrix more susceptible to bleaching agents, further contributing to its softening. The high molecular weight of the resin matrix and its lower filler content also contribute to a greater reduction in the microhardness of the material³¹.

The microhardness results indicated that the use of mouth rinses did not exacerbate the reduction in microhardness caused by dental bleaching, as no statistically significant differences were observed between the mouth rinse groups and the control group. This finding supports the first null hypothesis tested in the present study. The absence of additional effects may be attributed to the relatively low concentrations of active ingredients in the mouth rinses, which may not have been sufficient to cause significant structural alterations in the resin composite³². These results are in agreement with previous studies that evaluated different types of composite resins and reported no significant changes in microhardness following exposure to mouth rinses³³.

Surface roughness was also analyzed, as it represents an important indicator of material surface degradation and is directly associated with color stability, stain susceptibility, and optical properties such as light scattering and reflection³⁴. In the present study, all mouth rinse groups exhibited a significant increase in surface roughness between the initial and final measurements, thereby refuting the second null hypothesis. This increase can be largely attributed to the known effect of the 10% carbamide peroxide bleaching gel, since even the distilled water group showed increased roughness over time. However, significant differences among the experimental groups at the final time point suggest that the specific chemical composition of each mouth rinse influenced the extent of surface alteration observed.

The effects of essential oils in mouth rinses on resin composites have been previously reported. Studies have shown that compounds such as eucalyptol, menthol, methyl salicylate, and thymol can interact with the resin composites and influence surface characteristics¹⁶,²³,³⁵. In the present study, all mouth rinses contained essential oils, which may explain the general increase in surface roughness and the statistical differences observed in comparison with the control group. However, the mouth rinse containing only essential oils produced the lowest roughness values among the experimental rinses, whereas formulations containing both essential oils and alcohol resulted in higher roughness. This finding is consistent with previous research demonstrating that the presence of alcohol in combination with essential oils enhances the softening and degradation of resin composite surfaces³⁵.

Alcohol is known to interact with and damage the polymeric chains of resin-based composites¹⁸,³⁶. In this study, the group exposed to a mouth rinse containing essential oils and alcohol showed statistically significant increases in surface roughness compared to the distilled water group, corroborating previous reports that alcohol can enhance the surface degradation of composite resins³⁵. Alcohol is capable of inducing hygroscopic expansion, allowing it to penetrate polymeric chains, disrupt cross-links, and distort the polymer network¹⁸,³⁷. Such disruption can lead to leaching of unreacted monomers and the formation of micro-porosities within the material¹⁸. Furthermore, the resin composite composition may have contributed to these effects, as the triethylene glycol dimethacrylate (TEGDMA) monomer is particularly susceptible to alcohol-induced sorption due to its hydroxyl groups and ether bonds²²,³⁸, potentially compromising the composite’s physical properties.

The mouth rinse containing essential oils, alcohol, and hydrogen peroxide exhibited the greatest increase in surface roughness among the tested formulations. Although all rinses evaluated in this study were acidic, this particular mouth rinse had the lowest pH, which may have further contributed to the observed effects. Acidic conditions are known to alter the physical, chemical, and mechanical properties of restorative materials, including increasing surface roughness²¹,³⁹. Notably, this was the only mouth rinse applied for 60 seconds—twice the duration of the other rinses—following the manufacturer’s instructions. While this difference in exposure time represents a study limitation, it also ensures that the experimental protocol closely simulates clinically relevant conditions.

The third and final hypothesis of this study was rejected, as the use of mouth rinses significantly influenced the color of resin composites bleached with 10% carbamide peroxide.

Mouth rinses are well-recognized extrinsic factors that can compromise the color stability and esthetics of dental restorations⁴⁰. Since staining resistance and color stability are critical for the long-term clinical success of restorations⁴¹,⁴², alterations in these properties are affected by multiple material- and environment-related factors⁴²,⁴³.

The primary determinants of color stability are the composition and relative proportion of the organic matrix and inorganic filler content, which govern the hydrophilicity and susceptibility of the resin to staining⁴⁴,⁴⁵. Studies indicate that resins with lower inorganic filler content exhibit increased water sorption⁴⁶-⁴⁸. The presence of TEGDMA, a hydrophilic monomer in the tested composite, contributes to higher water uptake, an effect that is further enhanced when combined with Bis-GMA⁴⁴. Filler particles also play a critical role in staining susceptibility. Although the tested composite contains 78.5% filler by weight, the presence of aggregated zirconia/silica clusters can create inter-particulate gaps, which may facilitate color changes over time⁴⁷,⁴⁹.

Color changes are also influenced by surface texture and alterations in light reflection patterns³⁴,⁵⁰. In the present study, all groups exhibited increased surface roughness following bleaching, irrespective of the mouth rinse used. A rougher surface is more prone to staining, as it facilitates the adhesion and absorption of pigments from mouth rinses or other extrinsic sources⁵¹,⁵². Moreover, the specific composition of each mouth rinse may have contributed to pigmentation, as the groups containing essential oils with alcohol, and essential oils with alcohol and hydrogen peroxide displayed the highest surface roughness and were the only groups that differed significantly from the control in Δa^* values. The presence of alcohol combined with the low pH of these solutions can compromise the integrity of the composite resin surface, promoting degradation of the organic matrix and reducing resistance to staining⁵³.

Previous studies have demonstrated that mouth rinses can induce discoloration of resin composites¹⁷,⁴¹,⁵⁴. Although some experimental groups did not show statistically significant differences from the control, all groups exhibited perceptible color changes for ΔE_ab and ΔE₀₀ (ΔE_ab > 1.2, ΔE₀₀ > 0.8)⁵⁵. Notably, the groups containing essential oils with alcohol and essential oils with alcohol plus hydrogen peroxide showed significant differences from the control in Δa^* and ΔE₀₀, exceeding the clinical acceptability threshold (ΔE₀₀ > 1.8).

Although differences in color parameters were observed, the overall changes were modest, and no significant differences were detected for ΔL^*, Δb^*, or ΔE_ab. This may be related to the limited exposure time, as mouth rinses were applied only twice daily for short durations (30–60 seconds) over the 14-day period. Additionally, any pigments adhering to the resin surface could have been partially removed during subsequent bleaching gel applications, since the protocol involved using the mouth rinse on the same day as bleaching.

This study provides important insights into the effects of specific oral care products on resin composites, particularly in the context of esthetic treatments. However, limitations should be acknowledged. One key limitation is the variation in application times among the mouth rinses; one group was exposed for 60 seconds, while the others were applied for 30 seconds, potentially affecting surface roughness and color outcomes. Furthermore, although the 14-day experimental period is clinically relevant, it may not fully represent the long-term effects of repeated exposure. Another consideration is the in vitro design, which cannot entirely replicate the complexities of the oral environment, including factors such as saliva, masticatory forces, and remineralization processes, all of which may influence the degradation of resin composites. Therefore, long-term clinical studies are warranted to confirm these findings under more realistic oral conditions.

In conclusion, this study demonstrated that at-home dental bleaching with 10% carbamide peroxide significantly reduced the surface microhardness and increased the surface roughness of resin composites, potentially compromising their clinical durability. Mouth rinses containing essential oils, alcohol, and hydrogen peroxide further intensified surface roughness and affected color stability, although no additional reduction in microhardness was observed. These findings suggest that certain mouth rinses may accelerate the surface degradation of resin composites during bleaching, emphasizing the importance of careful product selection and professional guidance during at-home bleaching protocols. However, long-term in vivo and clinical studies are needed to confirm these results and to clarify the clinical relevance and longevity of resin-based restorations exposed to combined bleaching and mouth rinse use.

Acknowledgement

The authors extend their sincere appreciation to the Foundation for Research Support of the State of São Paulo (FAPESP), under the process number 2021/08194-5, for the financial support.

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• Data Availability:
  Datasets related to this article will be available upon request to the corresponding author.

Edited by

• Editor:
  Dr. Altair A. Del Bel Cury

Data availability

Datasets related to this article will be available upon request to the corresponding author.

Publication Dates

• Publication in this collection
  09 Mar 2026
• Date of issue
  2026

History

• Received
  7 July 2025
• Accepted
  25 Nov 2025