ceramics-02-00019

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ceramics
Article
Influence of a Bleaching Agent on the Color Stability
of Indirect Composite Resins Immersed in Dyes
Daniele M. dos Santos *, Emily V. F. da Silva , Juliani B. Mendonça, Denis Cetrangolo,
Fernanda P. de Caxias and Marcelo C. Goiato
Department of Dental Materials and Prosthodontics, Aracatuba Dental School,
Sao Paulo State University (UNESP), Aracatuba, Sao Paulo 16015-050, Brazil;
emilyvfs@yahoo.com.br (E.V.F.d.S.); juliani_mendonca@hotmail.com (J.B.M.);
dcetrangolo.3006@gmail.com (D.C.); fpc.bra@gmail.com (F.P.d.C.); m.goiato@unesp.br (M.C.G.)
* Correspondence: danielamicheline@foa.unesp.br; Tel.: +(55)-18-3636-3287; Fax: +(55)-18-3636-3245
Received: 31 January 2019; Accepted: 26 March 2019; Published: 1 April 2019
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Abstract: This study aimed to evaluate the effect of a bleaching agent on the color of extrinsically
pigmented indirect composite resins. Samples of five resins (Adoro, Resilab, Cristobal, Sinfony,
Epricord) were manufactured and divided into five groups: red wine, coffee, orange juice, Coca-Cola,
and artificial saliva (control). The stained samples were immersed in a 38% hydrogen peroxide
solution for 30 min per week, over three weeks. Color readings were performed at the initial state
(L0), after 21 days of dye immersion (∆E1, L1), and after 7 (∆E2, L2), 14 (∆E3, L3), and 21 days
(∆E4, L4) of bleach immersion. Data were subjected to ANOVA and Tukey’s honestly significant
difference (HSD) test (α = 0.05). The color alteration was greater in ∆E1, regardless of color solution,
indicating extrinsic pigmentation. The Resilab group exhibited greater ∆E1 values than the other
resins. The bleaching agent promoted bleaching action on the surfaces of the materials studied,
removing the previously impregnated pigments.
Keywords: composite resins; bleaching agents; color; staining
1. Introduction
Beauty standards directly influence dental esthetics. Therefore, dental procedures that involve
esthetics, such as restorations with composite resins and bleaching treatments, are under constant
development [1].
The chromatic alteration of composite resins can be caused by intrinsic or extrinsic factors.
The intrinsic factors are related to chemical and physical reactions in the deepest portions of the
restoration, in addition to changes in temperature and humidity. The extrinsic factors are related to
the adsorption or absorption of colored substances. In addition, the presence of hydrophilic particles
within the resinous matrix, with the capacity to absorb water, and the size and distribution of the
particles could provoke chromatic alterations of the restoration [2,3].
A material must have a natural appearance, biocompatibility, and longevity to be used in dental
applications [4]. Indirect resin composites incorporate some advantages of porcelain into the composite
resins without presenting inherent limitations [5]. In addition to having lower costs than porcelains,
they possess better properties than direct resins: reduced polymerization shrinkage, increased flexural
strength, resistance to abrasion and fracture, and increased color stability, presenting excellent clinical
results [2,3,6].
Despite mechanical polishing being able to remove superficial stains from restorations made from
composite resins [7], the use of bleaching agents could give better results in the removal of stains from
these materials [8,9]. Different substances can be used as bleaching agents, such as carbamide peroxide
Ceramics 2019, 2, 235–245; doi:10.3390/ceramics2020019 www.mdpi.com/journal/ceramics
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Ceramics 2019, 2 236
and hydrogen peroxide [9]. For in-office application, Opalescence Xtra Boost is a hydrogen peroxide
gel with a chemical activation that has a neutral pH, can be used efficiently and safely, and provides
appropriate results in a short period of time [10].
Therefore, the objective of this study was to evaluate the efficacy of the use of bleaching agents on
the color stability of extrinsically pigmented indirect composite resins. The null hypothesis was that
the bleaching agent was not effective for removing impregnated pigments, originating from staining
solutions from the surfaces of the tested indirect composite resins.
2. Materials and Methods
Five different brands of B2 (dentine)-colored indirect composite resins were evaluated (Table 1):
Adoro (Ivoclar Vivadent Ltda., São Paulo, São Paulo, Brazil), Resilab Master (Wilcos do Brasil, Indústria
e Comércio Ltda., Petrópolis, Rio de Janeiro, Brazil), Cristobal (Dentisply Ceramco, Burlington, NJ,
USA), Sinfony (3M, Campinas, São Paulo, Brazil), and Epricord (Kuraray Noritake Dental, Tokyo,
Japan) (Figure 1) [11]. Twenty-five samples from each brand were manufactured and divided into five
groups, according to the type of staining solution (red wine, coffee, orange juice, and Coca-Cola) or
artificial saliva (control group) (Table 2).
Table 1. Indirect composite resins used for specimen confection.
Brand Chemical Composition Polymerization
Adoro
17–19% of dimethacrylate, 82–83%
copolymers of silicon oxide, and 1%
stabilizers, catalysts, and pigments.
Pre-polymerization in a Targis Quick unit (halogen
lamp, intensity of 600 mW/cm2). Resin
impregnated with glycerin gel. Polymerization in a
Lunamat 100 unit, with eight lamps emitting
fluorescent light in a mirrored environment for
25 min (10 min with light, 10 min with heat at
1040 ◦C and 5 min with cooling unit) at a total
power of 750 W.
Resilab
Master
Small particles with a mean size of 0.05 mm,
53% of ceramic filler particles, BisGMA
(bisphenol A-glycidyl methacrylate),
BisEMA (ethoxylated bisphenol A-
dimethacrylate), UDMA (urethane
dimethacrylate), TEGMA (tri-ethylene
glycol dimethacrylate), aluminum
borosilicate, highly dispersible silica,
photoinitiators, inhibitors, and pigments.
Pre-polymerization for 4 min in an EDG-Lux unit
(400–500 mW/cm2) with temperature not
exceeding 50 ◦C. Final polymerization for 8 min in
an EDG-Lux unit (400–500 mW/cm2).
Cristobal 74% pyrogenic silica particles, barium glass,
and borosilicate.
Pre-polymerization in an MPa 2000 unit for 90 s
(200 mW/cm2) in the first cycle and then for 75 s
(800–1000 mW/cm2) in the second cycle. Final
polymerization in a Post Cure unit for 8 min at 80
◦C.
Sinfony
48% organic matrix (UDMA), 40%
strontium glass (macroparticle of 0.6 µm),
5% pyrogenic silica (microparticle of 0.06
µm), 5% glass ionomer cement particles, 1%
silane and 1% initiator.
Pre-polymerization for 15 s in Visio Alfa Light and
Visio Beta Vario Light units used with a Visio Beta
Vacuum pump (470 mW/cm2). Final
polymerization in two stages: 1 minute of light
emission in air followed by 14 min of light
emission in vacuum in Visio Beta.
Epricord
53% ceramic filler content, 25%
multifunctional polymers and 22%
conventional resin photoinitiators. The
mean particle size is 0.6 µm.
Pre-polymerization for 30 s in a Kota unit. Final
polymerization for 180 s with a halogen lamp (600
mW/cm2) in a Kota unit.
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Figure 1. Indirect composite resin sample. 
2.1. Manufacturing of Samples 
The samples were manufactured in a cast stainless steel matrix (10 mm length × 5 mm width × 
1.5 mm thickness) according to the recommendations of the manufacturers (Table 1) [10]. After the 
final polymerization, the samples were polished in a semi-automatic polishing machine (Ecomet 
300PRO, Buehler, Lake Bluff, IL, USA), running at 300 rpm, with metallographic sandpaper of 240, 
400, 800, and 1200 grit (Buehler, Lake Bluff, IL, USA), under constant irrigation with water. The 
polishing of the samples was finalized using a felt disc with diamond solution(Buehler, Lake Bluff, 
IL, USA). Each sample had its thickness checked, with the assistance of a digital caliper (500-171-20B, 
Mitutoyo, Tokyo, Japan), in order to ensure the correct dimensions. All samples were stored in a 
digital bacteriologic incubator (CIENLAB Equipamento Científicos Ltda., Campinas, São Paulo, 
Brazil), in distilled water at 37 ± 1 °C for 24 hours, before the initial color reading [3]. 
Table 2. Immersion solutions used in the study. 
Solution Brand Chemical Composition 
Red wine 
Periquita dry red wine, José 
Maria Da Fonseca Vinhos S.A., 
Azeitão, Portugal 
Red grape varieties, conservative INS 220 (sulfur 
dioxide, SO2), sulphurous acid, and 12.7% alcohol. 
Coffee 
Coffee Pilão, Sara Lee, Jundiaí, 
São Paulo, Brazil Roasted and ground coffee. 
Orange 
juice 
Coca-Cola, Ribeirão Preto, Brazil Orange juice, water, sugar, orange pulp, natural 
flavors, ascorbic acid, and citric acid. 
Coca-Cola Coca-Cola, Ribeirão Preto, Brazil Carbonated water, sugar, cola nut extract, yellow 
dye IV, acidulant INS 338, and natural flavors. 
Artificial 
saliva 
Farmácia de Manipulação 
Apothicário, Araçatuba, Brazil 
[KCl (0.4 g·L−1), NaCl (0.4 g·L−1), CaCl2·2H2O (0.906 
g·L−1), NaH2PO4·2H2O (0.690 g·L−1), Na2S·9H2O 
(0.005 g·L−1), and urea (1 g·L−1)]. 
2.2. Process of Immersion 
Each sample was placed in a flask containing 1 mL of a specific solution (Table 2), and sealed to 
prevent its evaporation. Immersed in the solutions, which were substituted daily, the samples were 
stored in an incubator at 37 ± 1 °C for 4 hours per day for 21 days. When not immersed in the solution, 
they were stored in artificial saliva [12]. 
After the immersion, all samples were subjected to the 38% hydrogen peroxide bleaching agent 
(Opalescence Xtra Boost, Ultradent, South Jordan, Utah, USA) for 30 minutes per week, for 3 weeks, 
according to the recommendation from the manufacturer [13]. During this period, the samples 
continued to be stored in the incubator at 37 ± 1 °C for 21 days. When not immersed in the bleaching 
solution, they were stored in artificial saliva [13]. 
 
Figure 1. Indirect composite resin sample.
2.1. Manufacturing of Samples
The samples were manufactured in a cast stainless steel matrix (10 mm length × 5 mm width ×
1.5 mm thickness) according to the recommendations of the manufacturers (Table 1) [10]. After the
final polymerization, the samples were polished in a semi-automatic polishing machine (Ecomet
300PRO, Buehler, Lake Bluff, IL, USA), running at 300 rpm, with metallographic sandpaper of
240, 400, 800, and 1200 grit (Buehler, Lake Bluff, IL, USA), under constant irrigation with water.
The polishing of the samples was finalized using a felt disc with diamond solution (Buehler, Lake Bluff,
IL, USA). Each sample had its thickness checked, with the assistance of a digital caliper (500-171-20B,
Mitutoyo, Tokyo, Japan), in order to ensure the correct dimensions. All samples were stored in a digital
bacteriologic incubator (CIENLAB Equipamento Científicos Ltda., Campinas, São Paulo, Brazil), in
distilled water at 37 ± 1 ◦C for 24 h, before the initial color reading [3].
Table 2. Immersion solutions used in the study.
Solution Brand Chemical Composition
Red wine
Periquita dry red wine, José Maria
Da Fonseca Vinhos S.A., Azeitão,
Portugal
Red grape varieties, conservative INS 220 (sulfur
dioxide, SO2), sulphurous acid, and 12.7% alcohol.
Coffee Coffee Pilão, Sara Lee, Jundiaí, São
Paulo, Brazil Roasted and ground coffee.
Orange juice Coca-Cola, Ribeirão Preto, Brazil Orange juice, water, sugar, orange pulp, natural
flavors, ascorbic acid, and citric acid.
Coca-Cola Coca-Cola, Ribeirão Preto, Brazil Carbonated water, sugar, cola nut extract, yellow dye
IV, acidulant INS 338, and natural flavors.
Artificial saliva Farmácia de Manipulação
Apothicário, Araçatuba, Brazil
[KCl (0.4 g·L−1), NaCl (0.4 g·L−1), CaCl2·2H2O
(0.906 g·L−1), NaH2PO4·2H2O (0.690 g·L−1),
Na2S·9H2O (0.005 g·L−1), and urea (1 g·L−1)].
2.2. Process of Immersion
Each sample was placed in a flask containing 1 mL of a specific solution (Table 2), and sealed to
prevent its evaporation. Immersed in the solutions, which were substituted daily, the samples were
stored in an incubator at 37 ± 1 ◦C for 4 h per day for 21 days. When not immersed in the solution,
they were stored in artificial saliva [12].
After the immersion, all samples were subjected to the 38% hydrogen peroxide bleaching agent
(Opalescence Xtra Boost, Ultradent, South Jordan, Utah, USA) for 30 min per week, for 3 weeks,
according to the recommendation from the manufacturer [13]. During this period, the samples
continued to be stored in the incubator at 37 ± 1 ◦C for 21 days. When not immersed in the bleaching
solution, they were stored in artificial saliva [13].
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2.3. Reading of the Color Alteration
The readings of the color alteration were performed in the following periods: initial (L0), after 21
days of immersion in the color solutions (∆E1 and L1), after 7 days of immersion in the bleaching
agent (∆E2 and L2), after 14 days of immersion in the bleaching agent (∆E3 and L3), and after 21 days
of immersion in the bleaching agent (∆E4 and L4). The readings of the color alteration (∆E) and
luminosity (L*) of the samples were performed with the assistance of a reflection spectrophotometer
(UV-2450, Shimadzu Corp., Kyoto, Japan) [14,15]. Color alterations (∆E) were calculated by means of
the L*a*b* system, as established by the CIE—Commission Internacionale de l’Eclairage [16].
2.4. Statistical Analysis
The data describing the color alteration (∆E) and the L* (CIELab) coordinates obtained were
subjected to the three-way analysis of variance (ANOVA) with repeated-measure factors, and the
Tukey honestly significant difference (HSD) test (α = 0.05), in order to detect statistically significant
differences between the analyzed factors.
3. Results
From the results, it was observed that interactions between the type of resin, the staining solution
used, and the period of analysis significantly affected the color alteration (∆E) (P < 0.001) (Table 3) and
the L* coordinate (P < 0.001) (Table 4).
The color alteration was greatest at ∆E1, regardless of the staining solution and the composite
resin analyzed, indicating pigmentation of the materials after immersion. The Resilab group exhibited
the greatest values of ∆E1, when compared to the other resins. From the analyses of ∆E2, ∆E3, and ∆E4,
it was concluded that the bleaching agent produced a bleaching action on the surfaces of the materials
studied, removing the previously impregnated pigments (Tables 5–9).
By considering the L* coordinate (Figures 2–6), it was verified that the bleaching agent permitted
an increase in the lightness of the materials studied, after the immersion in the coloring solutions.
This indicates a bleaching action on the surface.
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2.3. Reading of the Color Alteration 
The readings of the color alteration were performed in the following periods: initial (L0), after 
21 days of immersion in the color solutions (ΔE1 and L1), after 7 days of immersion in the bleaching 
agent (ΔE2 and L2), after 14 days of immersion in the bleaching agent (ΔE3 and L3), and after 21 days 
of immersion in the bleaching agent (ΔE4 and L4). The readings of the color alteration (ΔE) and 
luminosity (L*) of the samples were performed with the assistance of a reflection spectrophotometer 
(UV-2450, Shimadzu Corp., Kyoto, Japan) [14,15]. Color alterations (ΔE) were calculated by means of 
the L*a*b* system, as established by the CIE—Commission Internacionale de l’Eclairage [16]. 
2.4. Statistical Analysis 
The data describing the color alteration (ΔE) and the L* (CIELab) coordinates obtained were 
subjected to the three-way analysis of variance (ANOVA) with repeated-measure factors, and the 
Tukey honestly significant difference(HSD) test (α = 0.05), in order to detect statistically significant 
differences between the analyzed factors. 
3. Results
From the results, it was observed that interactions between the type of resin, the staining solution 
used, and the period of analysis significantly affected the color alteration (ΔE) (P < 0.001) (Table 3) 
and the L* coordinate (P < 0.001) (Table 4). 
The color alteration was greatest at ΔE1, regardless of the staining solution and the composite 
resin analyzed, indicating pigmentation of the materials after immersion. The Resilab group 
exhibited the greatest values of ΔE1, when compared to the other resins. From the analyses of ΔE2, 
ΔE3, and ΔE4, it was concluded that the bleaching agent produced a bleaching action on the surfaces 
of the materials studied, removing the previously impregnated pigments (Tables 5–9). 
By considering the L* coordinate (Figures 2–6), it was verified that the bleaching agent permitted 
an increase in the lightness of the materials studied, after the immersion in the coloring solutions. 
This indicates a bleaching action on the surface. 
Figure 2. Mean values of L* coordinates of Adoro resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
Figure 2. Mean values of L* coordinates of Adoro resin for each color solution used, in each period
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between different
color solutions in the same period. Different capital letters indicate statistically significant differences
(P < 0.05) between different periods for the same color solution.
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Figure 3. Mean values of L* coordinate of Resilab resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
Table 3. Three-way analysis of variance (ANOVA) with repeated-measure factors for color alterations 
(ΔE) of indirect composite resins. 
 SS df MS F P 
Resin 6566.386 4 1641.597 2142.478 <0.001 
Solution 131.647 4 32.912 42.954 <0.001 
Resin × Solution 458.558 16 28.660 37.404 <0.001 
Between subjects 172.398 225 0.766 
Period 19,564.573 2.845 6877.370 5664.649 <0.001 
Period × Resin 12,870.394 11.379 1131.055 931.611 <0.001 
Period × Solution 930.291 11.379 81.754 67.338 <0.001 
Period × Resin × Solution 3266.354 45.516 71.762 59.108 <0.001 
Within subjects 777.105 675 1.151 
P < 0.05 denotes statistically significant difference. 
Table 4. Three-way analysis of variance (ANOVA) with repeated-measure factors for L* coordinate 
of indirect composite resins. 
 SS df MS F P 
Resin 23,185.790 4 5796.447 1693.562 <0.001 
Solution 200.716 4 50.179 14.661 <0.001 
Resin × Solution 829.049 16 51.816 15.139 <0.001 
Between subjects 770.093 225 3.423 
Period 8636.929 3.071 2812.801 1324.969 <0.001 
Period × Resin 25,959.112 12.282 2113.535 995.580 <0.001 
Period × Solution 2326.537 12.282 189.422 89.227 <0.001 
Period × Resin × Solution 4517.111 49.129 91.943 43.310 <0.001 
Within subjects 1466.683 900 1.630 
P < 0.05 denotes statistically significant difference. 
4. Discussion 
The null hypothesis tested, that the bleaching agent was not effective for the removal of pigments 
originating from staining solutions from the surface of indirect resins, was rejected. This is because 
Figure 3. Mean values of L* coordinate of Resilab resin for each color solution used, in each period
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between different
color solutions in the same period. Different capital letters indicate statistically significant differences
(P < 0.05) between different periods for the same color solution.
Table 3. Three-way analysis of variance (ANOVA) with repeated-measure factors for color alterations
(∆E) of indirect composite resins.
SS df MS F P
Resin 6566.386 4 1641.597 2142.478 <0.001
Solution 131.647 4 32.912 42.954 <0.001
Resin × Solution 458.558 16 28.660 37.404 <0.001
Between subjects 172.398 225 0.766
Period 19,564.573 2.845 6877.370 5664.649 <0.001
Period × Resin 12,870.394 11.379 1131.055 931.611 <0.001
Period × Solution 930.291 11.379 81.754 67.338 <0.001
Period × Resin × Solution 3266.354 45.516 71.762 59.108 <0.001
Within subjects 777.105 675 1.151
P < 0.05 denotes statistically significant difference.
Table 4. Three-way analysis of variance (ANOVA) with repeated-measure factors for L* coordinate of
indirect composite resins.
SS df MS F P
Resin 23,185.790 4 5796.447 1693.562 <0.001
Solution 200.716 4 50.179 14.661 <0.001
Resin × Solution 829.049 16 51.816 15.139 <0.001
Between subjects 770.093 225 3.423
Period 8636.929 3.071 2812.801 1324.969 <0.001
Period × Resin 25,959.112 12.282 2113.535 995.580 <0.001
Period × Solution 2326.537 12.282 189.422 89.227 <0.001
Period × Resin × Solution 4517.111 49.129 91.943 43.310 <0.001
Within subjects 1466.683 900 1.630
P < 0.05 denotes statistically significant difference.
4. Discussion
The null hypothesis tested, that the bleaching agent was not effective for the removal of pigments
originating from staining solutions from the surface of indirect resins, was rejected. This is because the
Ceramics 2019, 2 240
bleaching agent produced a bleaching action on the surfaces of the materials studied, removing the
previously impregnated pigments (Tables 5–9, Figures 2–6).
It can be verified, through the results (Tables 5–9), that the delta of the color for all samples was
greater than 3.3 in all color solutions. This indicates, by spectrophotometric analysis, an alteration
of color which is visually perceptible and clinically unacceptable from the point of view of esthetics
(∆E < 3.3) [17,18].
It is known that the alterations of the color of composite resins are multifactorial, involving
intrinsic and extrinsic factors [19–21]. The intrinsic factors are related to the chemical stability of the
material, which depends on the fractional conversion of the monomers present in the resinous matrix.
The presence of residual monomers in the resinous material induces susceptibility to pigmentation by
absorption of external substances [22].
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the bleaching agent produced a bleaching action on the surfaces of the materials studied, removing 
the previously impregnated pigments (Tables 5–9, Figures 2–6). 
 
Figure 4. Mean values of L* coordinate of Epricord resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
 
Figure 5. Mean values of L* coordinate of Cristobal resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
Figure 4. Mean values of L* coordinate of Epricord resin for each color solution used, in each period
evaluated. Different small letters indicate statistically significant differences(P < 0.05) between different
color solutions in the same period. Different capital letters indicate statistically significant differences
(P < 0.05) between different periods for the same color solution.
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the bleaching agent produced a bleaching action on the surfaces of the materials studied, removing 
the previously impregnated pigments (Tables 5–9, Figures 2–6). 
 
Figure 4. Mean values of L* coordinate of Epricord resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
 
Figure 5. Mean values of L* coordinate of Cristobal resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
Figure 5. Mean values of L* coordinate of Cristobal resin for each color solution used, in each period
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between different
color solutions in the same period. Different capital letters indicate statistically significant differences
(P < 0.05) between different periods for the same color solution.
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Figure 6. Mean values of L* coordinates of Sinfony resin for each color solution used, in each period 
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between 
different color solutions in the same period. Different capital letters indicate statistically significant 
differences (P < 0.05) between different periods for the same color solution. 
Table 5. Mean values of color alterations (∆E) of Adoro resin for each staining solution, before and 
after bleaching treatment. 
Resin 
Staining Solution 
Red Wine Coffee Orange Juice Coca-Cola Saliva 
Adoro ∆E1 6.59 Aa 5.99 Aab 5.42 Ab 6.14 Aab 0.57 Bc 
 ∆E2 2.79 Bb 5.05 Ba 1.89 Bc 2.20 Bbc 0.45 Bd 
 ∆E3 3.40 Ba 2.47 Cb 1.89 Bb 2.47 Bb 1.96 Ab 
 ∆E4 0.76 Ca 0.66 Da 1.20 Ba 1.22 Ca 0.85 Ba 
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey). 
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey). 
Table 6. Mean values of color alterations (∆E) of Resilab resin for each staining solution, before and 
after bleaching treatment. 
Resin 
Staining Solution 
Red Wine Coffee Orange Juice Coca-Cola Saliva 
Resilab ∆E1 13.49 Ad 29.44 Ac 35.64 Aa 34.53 Ab 33.68 Ab 
 ∆E2 8.15 Ba 4.61 Bb 1.18 Dc 1.87 Cc 1.34 Cc 
 ∆E3 5.13 Ca 3.19 Cb 2.26 Ccd 1.77 Cd 2.93 Bbc 
 ∆E4 4.56 Dab 3.87 BCab 3.53 Bb 4.77 Ba 1.98 BCc 
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey). 
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey). 
Table 7. Mean values of color alterations (∆E) of Epricord resin for each staining solution, before and 
after bleaching treatment. 
Resin 
Staining Solution 
Red Wine Coffee Orange Juice Coca-Cola Saliva 
Epricord ∆E1 12.78 Ab 13.84 Aa 11.54 Ac 11.54 Ac 11.53 Ac 
 ∆E2 5.52 Bab 6.16 Ba 4.05 Cc 4.20 Cc 5.09 Cb 
 ∆E3 6.32 Ba 5.93 Ba 6.35 Ba 5.94 Ba 6.28 Ba 
 ∆E4 2.50 Ca 0.95 Cb 1.08 Db 0.84 Db 0.88 Db 
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey). 
Figure 6. Mean values of L* coordinates of Sinfony resin for each color solution used, in each period
evaluated. Different small letters indicate statistically significant differences (P < 0.05) between different
color solutions in the same period. Different capital letters indicate statistically significant differences
(P < 0.05) between different periods for the same color solution.
Table 5. Mean values of color alterations (∆E) of Adoro resin for each staining solution, before and
after bleaching treatment.
Resin
Staining Solution
Red Wine Coffee Orange Juice Coca-Cola Saliva
Adoro ∆E1 6.59 Aa 5.99 Aab 5.42 Ab 6.14 Aab 0.57 Bc
∆E2 2.79 Bb 5.05 Ba 1.89 Bc 2.20 Bbc 0.45 Bd
∆E3 3.40 Ba 2.47 Cb 1.89 Bb 2.47 Bb 1.96 Ab
∆E4 0.76 Ca 0.66 Da 1.20 Ba 1.22 Ca 0.85 Ba
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey).
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey).
Table 6. Mean values of color alterations (∆E) of Resilab resin for each staining solution, before and
after bleaching treatment.
Resin
Staining Solution
Red Wine Coffee Orange Juice Coca-Cola Saliva
Resilab ∆E1 13.49 Ad 29.44 Ac 35.64 Aa 34.53 Ab 33.68 Ab
∆E2 8.15 Ba 4.61 Bb 1.18 Dc 1.87 Cc 1.34 Cc
∆E3 5.13 Ca 3.19 Cb 2.26 Ccd 1.77 Cd 2.93 Bbc
∆E4 4.56 Dab 3.87
BCab 3.53 Bb 4.77 Ba 1.98 BCc
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey).
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey).
Ceramics 2019, 2 242
Table 7. Mean values of color alterations (∆E) of Epricord resin for each staining solution, before and
after bleaching treatment.
Resin
Staining Solution
Red Wine Coffee Orange Juice Coca-Cola Saliva
Epricord ∆E1 12.78 Ab 13.84 Aa 11.54 Ac 11.54 Ac 11.53 Ac
∆E2 5.52 Bab 6.16 Ba 4.05 Cc 4.20 Cc 5.09 Cb
∆E3 6.32 Ba 5.93 Ba 6.35 Ba 5.94 Ba 6.28 Ba
∆E4 2.50 Ca 0.95 Cb 1.08 Db 0.84 Db 0.88 Db
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey).
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey).
Table 8. Mean values of color alterations (∆E) of Cristobal resin for each staining solution, before and
after bleaching treatment.
Resin
Staining Solution
Red Wine Coffee Orange Juice Coca-Cola Saliva
Cristobal ∆E1 8.57 Aab 9.27 Aa 8.54 Aab 8.58 Aab 8.39 Ab
∆E2 6.51 Ba 4.10 Bb 2.91 Bc 3.32 Bc 0.82 Cc
∆E3 1.31 Cbc 1.85 Cab 0.74 Cc 0.77 Cc 2.40 Ba
∆E4 0.69 Cbc 2.02 Ca 0.58 Cc 1.69 Cab 2.06 Ba
Means followed by the same capital letter in column and do not differ (P < 0.05; Tukey).
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey).
Table 9. Mean values of color alterations (∆E) of Sinfony resin for each staining solution, before and
after bleaching treatment.
Resin
Staining Solution
Red Wine Coffee Orange Juice Coca-Cola Saliva
Sinfony ∆E1 11.22 Aa 9.95 Ab 8.83 Ac 8.06 Ac 8.25 Ac
∆E2 5.87 Ba 2.76 Bb 0.84 Cc 1.39 Cc 1.01 Cc
∆E3 2.24 Cab 2.40 Ba 1.39 Cb 2.34 Ba 2.48 Ba
∆E4 1.55 Cb 2.02 Bab 2.83 Ba 1.89
BCab
1.83
BCab
Means followed by the same capital letter in column do not differ (P < 0.05; Tukey).
Means followed by the same lowercase letter in the line do not differ (P < 0.05; Tukey).
Despite the versatility and good esthetic results of resinous materials, the absorption of staining
agents is still the most prominent reason for chromatic alterations of these materials, and staining of
restorations [23]. Among the liquid solutions tested in the present study, red wine (greater ∆E1 for
Adoro and Sinfony), coffee (greater ∆E1 for Epricord and Cristobal), and orange juice (greater ∆E1
for Resilab) affected the color stability the most, with a statistically significant difference from the
other solutions (Tables 5–9). According to some studies, coffee possesses a great capacity for staining,
caused by absorption and adsorption of yellow pigments of low polarity, which possess a chemical
affinity to the polymeric phase of the resinous material [19,24,25]. Similar to coffee, some studies
demonstrate the great effect that red wine shows in pigmentation of resinousmaterials, due to the
alcohol it contains [24,26]. Orange juice contains citric acid, which could influence the pigmentation of
materials [27].
Several studies have also demonstrated a staining potential of tea, showing greater pigmentation
than coffee [28] and grape juice [29], for example. The color alteration is a result of theaflavins present
in tea leaves, which produce a yellowish-brown stain [16]. Therefore, this staining solution should be
evaluated in further studies for a better understanding of its behavior.
Ceramics 2019, 2 243
Many times, dental surgeons perform superficial polishing of the material, trying to minimize
staining and to remove extrinsic pigments from the surface of the restoration, thus increasing the
longevity of the restoration. However, some studies affirm that bleaching agents could also be capable
of removing intrinsic and extrinsic stains from restorations [8,9,30,31]. This was observed in the
present study, in which the values of ∆E2, ∆E3, and ∆E4 indicated that the bleaching agent effectively
decolored the surfaces of the materials (Tables 5–9). Nonetheless, to evaluate only the ∆E values could
induce an error, since the color of these materials is affected by a combination of intrinsic and extrinsic
factors, and the correlations in the results obtained by existing laboratory methods, such as the CIE
L*a*b*, are poor [32], many times making it necessary to evaluate each coordinate.
Values of the L* coordinate (Figures 2–6) extend from 0 (black) to 100 (perfect white), describing
the luminosity of the sample. It was observed that after the immersion in the staining solutions used,
the bleaching agent produced an increase in the lightness of the resins analyzed, resembling the initial
values. This indicates that removal of the pigments impregnated on the surfaces of the materials
studied could have occurred.
However, this may not occur clinically, since the effects of the solutions tested could be modified by
the action of bacterial biofilms and saliva. The laboratory tests, in which immersions of these restorative
materials are performed in different solutions, are biased by disregarding these factors [9]. In addition,
the bleaching agents could also provoke the detachment of charged particles from the surface of
the resinous materials, since hydrogen peroxide can cause oxidation and reduction reactions [33,34].
This action could lead to an increase in the superficial roughness, facilitating even more staining of the
material when it is again exposed to staining solutions [8,9,30]. Therefore, more in vitro studies that
simulate the effects of these factors, and laboratory methods that possess a strong correlation between
the laboratory tests and the results found in clinics, are necessary.
In the present study, a challenge was performed, which consisted of periods of exposure to
solutions intercalated with periods of exposure to saliva, simulating oral conditions with high
accuracy. The clinical implication of this study is that the greatest color alteration was observed
in ∆E1, independent of color solution, indicating extrinsic pigmentation. The Resilab group exhibited
greater values of ∆E1 when compared to the other resins. The 38% hydrogen peroxide-based bleaching
agent effectively bleached the surfaces of the materials studied. Therefore, these findings are important
to patients and can help scientists and professionals in their clinical practice.
5. Conclusions
Based on the results obtained, and considering the limitations of this study, it can be concluded
that the 38% hydrogen peroxide-based bleaching agent produced a bleaching action of the surfaces of
the materials studied, removing the previously impregnated pigments.
Author Contributions: In regards to the contributions of each author, all authors contributed equally to the
work. M.C.G. and D.M.d.S. participated in the concepts and coordination of the study, performed the study
design, and drafted the manuscript. E.V.F.d.S., J.B.M. and D.C. conceived the study, fabricated the samples,
and participated in assays, as well helped draft the manuscript. F.P.d.C. performed the statistical analysis and
participated in interpretation of data. All authors read and approved the final manuscript.
Funding: This research was funded the Sao Paulo Research Foundation, grant number 2012/13244-2.
Acknowledgments: This work was supported by the Sao Paulo Research Foundation [Process 2012/13244-2].
Conflicts of Interest: The authors declare no conflict of interest.
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	Introduction 
	Materials and Methods 
	Manufacturing of Samples 
	Process of Immersion 
	Reading of the Color Alteration 
	Statistical Analysis 
	Results 
	Discussion 
	Conclusions 
	References