Effects of staining and bleaching on color change of dental composite resins
Patricia Villalta, DDS, MS,a Huan Lu, DDS, PhD,b Zeynep Okte, DDS, PhD,c
Franklin Garcia-Godoy, DDS, MS,d and John M. Powers, PhDe
College of Dental Medicine, Nova Southeastern University, Fort Lauderdale, Fla; Department of
Restorative Dentistry and Biomaterials, University of Texas Dental Branch at Houston, Tex;
University of Ankara, Faculty of Dentistry, Ankara, Turkey
Statement of problem. Discoloration of resin-based composites by colored solutions is a common problem.
The use of bleaching agents for discolored natural teeth is becoming increasingly popular. It is not clear if
bleaching agents can remove the stain from composite resins.
Purpose. The purpose of this study was to investigate the effects of 2 staining solutions and 3 bleaching systems
on the color changes of 2 dental composite resins.
Material and methods. Forty-five disk-shaped specimens (9 3 2.5 mm) of each of 2 composite resins, Filtek
Supreme (FS) and Esthet X (EX), were prepared. The specimens were then divided into 3 groups of 15 specimens each and immersed in 2 staining solutions (coffee or red wine) or distilled water (control) for 3 hours
daily over a 40-day test period. The 3 groups were then divided into 3 subgroups (n=5), and 3 bleaching agents
(Crest Night Effects, Colgate Simply White Night, or Opalescence Quick) were applied to the surface of the
specimens over a 14-day period. Color of the specimens was measured with a spectrophotometer using CIELAB
color space relative to CIE standard illuminant D55 at baseline, after staining, and after bleaching. The color
differences (DEab*) between the 3 measurements were calculated. The value DEab*=3.3 was used as an acceptable value in subjective visual evaluations. Analysis of variance and nonparametric analysis (Kruskal-Wallis test
and Mann-Whitney test) were used to analyze the data.
Results. After staining, FS had more color change than EX and was more affected by the wine solution. After
bleaching, the color of both EX and FS specimens returned to the baseline. The color differences between
bleaching and baseline were less than value DEab*=3.3 for all groups.
Conclusion. The nanocomposite (FS) changed color more than the microhybrid composite (EX) as a result of
staining in coffee or red wine solutions. After bleaching, discoloration was removed completely from the
composite resins tested. (J Prosthet Dent 2006;95:137-42.)
CLINICAL IMPLICATIONS
Red wine and coffee caused discoloration of the composite resins tested. Different concentrations
of carbamide peroxide appear to have clinically similar effects in removing stain on the surface of
shade A2 composite resins.
C
omposite resins have been widely used since
their introduction because of their excellent esthetic
properties. However, a major disadvantage is their discoloration after prolonged exposure to the oral environment. Unacceptable color match is a primary reason for
replacement of composite resin restorations.1,2
a
Assistant Professor, Bioscience Research Center, College of Dental
Medicine, Nova Southeastern University.
b
Assistant Professor, Oral Biomaterials, Department of Restorative
Dentistry and Biomaterials, University of Texas Dental Branch
at Houston.
c
Associate Professor, Department of Pedodontics, University of
Ankara, Faculty of Dentistry.
d
Associate Dean of Research; Director, Bioscience Research Center;
Director, Clinical Research Center, Bioscience Research Center,
College of Dental Medicine, Nova Southeastern University.
e
Professor and Director, Houston Biomaterials Research Center,
University of Texas Dental Branch at Houston.
FEBRUARY 2006
Composite resin restorative materials undergo a series of physical changes as a result of the polymerization
reaction and the subsequent interaction with the wet
oral environment.3 Following polymerization, the inward movement of water molecules causes mobilization
of ions within the matrix and outward movement of
unreacted monomers and ions leached from fillers and
activators.4-6 Elution of leachable components contributes to further shrinkage and loss of weight, whereas
hygroscopic absorption of water results in a swelling of
material and an increase in weight.7 This process may
cause softening of the resin matrix and reduction of stain
resistance.8,9
Discoloration of tooth-colored resin-based materials
may be caused by intrinsic and extrinsic factors. Intrinsic
factors involve the discoloration of the resin material
itself, such as the alteration of the resin matrix and the
interface of matrix and fillers.2 The intrinsic color of
THE JOURNAL OF PROSTHETIC DENTISTRY 137
THE JOURNAL OF PROSTHETIC DENTISTRY
VILLALTA ET AL
Table I. Resin composites and bleaching systems used
Product
Composite resins
Filtek Supreme
Esthet-X
Bleaching agents
Crest Night Effects
Colgate Simply White Night
Opalescence Quick
Code
Composition/type
Lot No.
FS
EX
Nanocomposite
Microhybrid composite
3M ESPE, St. Paul, Minn
Dentsply Caulk, Milford, Del
20040330
0410055
CNE
CSWN
OPAL
16% Carbamide peroxide
18% Carbamide peroxide
35% Carbamide peroxide
Procter & Gamble, Cincinnati, Ohio
Colgate-Palmolive, New York, NY
Ultradent, South Jordan, Utah
30435614J0
P9809176
5J69
esthetic materials may change when materials are aged
under various physical-chemical conditions such as
thermal changes and humidity.10 Extrinsic factors such
as adsorption or absorption of stains may also cause
discoloration.11,12
The staining of resin-based materials by colored solutions such as coffee, tea, and other beverages,10-18 and
color stability after aging in different solutions2,19-21
have been reported. Scotti et al21 simulated the oral
condition by immersing specimens in synthetic saliva
combined with coffee, tea, or chlorhexidine in a dark
environment at 37°C, and concluded that synthetic
saliva and coffee produced the greatest darkening and
that the type of material also had a significant role on
the stain resistance. Stober et al22 reported that red
wine and coffee caused severe discoloration, with total
color differences of DE.10 in all the tested composites.
Um and Ruyter23 stated that discoloration by coffee was
due to absorption of colorants by the tested materials.
Iazzetti et al10 studied the color stability of 6 fluoridereleasing materials by immersing the specimens in coffee
mixed with soluble tea and cranberry juice. The authors
reported that the hydrophobic materials showed greater
color stability and stain resistance than the hydrophilic
materials. Lim et al20 evaluated the degree of color stability of glass ionomers and polyacid modified resin–
based composites in various environmental solutions
and found that glass ionomers and polyacid modified
resin–based composites showed significant color changes
in 0.1 mole acetic acid and 10% hydrogen peroxide
solution.
Since their introduction, the use of bleaching agents
has become increasingly popular for whitening stained
teeth.24-26 As these products contact tooth structures
for extended periods of time, they may come into contact with dental materials.27 As discoloration of resinbased composites is a common problem, studies also
investigated the effect of bleaching agents on toothcolored materials.28-37 Cooley and Burger28 evaluated
composite resins for changes in surface hardness, roughness, and lightness after exposure to 10% carbamide peroxide gels and found that these 3 parameters increased
significantly after exposure. Fay et al30 concluded that
the 10% carbamide peroxide bleaching agent used in
138
Manufacturer
the study removed stains from the composite resin and
hybrid ionomer but was not effective in removing
them from the compomer. Other studies compared
the effect of carbamide versus hydrogen peroxide on
composite resins. Cullen et al31 reported that 10% carbamide peroxide and 30% hydrogen peroxide had no
significant effect on tensile strength of highly filled
composite resins. However, microfilled composite resins
were significantly affected by 30% hydrogen peroxide,
resulting in a reduction in tensile strength. Canay and
Cehreli34 showed that 10% hydrogen peroxide caused
more color changes of composite resins compared
with 10% carbamide peroxide, and the color change of
all composite resins bleached with hydrogen peroxide
solution was clinically detectable to the naked eye.
New bleaching products continue to appear on the
market that can be used effectively in bleaching human
teeth.38-44 No study was identified that tested the effects
of these products on stained composite resins. The aim
of this study was to analyze the effects of 2 staining solutions and 3 bleaching agents on the color stability of
2 composite resins.
MATERIAL AND METHODS
The 2 composite resins and 3 bleaching agents used
in this study are shown in Table I. An A2 color shade
was selected for the 2 composite resins. Forty-five
disk-shaped specimens from each material (90 specimens in total), 9 mm in diameter and 2.5 mm in depth,
were prepared in polytetrafluoroethylene molds. The
materials were handled according to the manufacturers’
instructions. A nylon thread was incorporated into the
specimen so that the specimen could be suspended in
the staining solutions. The mold with the composite
resin was held between 2 glass slides, each covered
with a transparent polyester strip (Mylar; Henry Schein,
Melville, NY), and the microscope slides were gently
pressed together to remove excess material. Specimens were polymerized by a conventional halogen lightpolymerizing unit (ESPE Elipar Trilight; 3M ESPE,
St. Paul, Minn) with light intensity of 450 mW/cm2,
using 40 seconds of exposure to top and bottom surfaces, respectively. The distance between the light
VOLUME 95 NUMBER 2
VILLALTA ET AL
THE JOURNAL OF PROSTHETIC DENTISTRY
Table II. Mean values (SDs) of color change (DEab*)
Coffee
CSWN
Esthet X
Filtek Supreme
STBL
BBL
BST
STBL
BBL
BST
3.6
0.7
4.0
6.3
1.4
5.1
(0.3)*
(0.5)
(0.7)*
(2.2)*
(0.9)
(1.5)*
CNE
3.9
1.1
3.2
6.2
2.4
3.8
(0.4)*
(0.5)
(0.4)
(0.5)*
(0.4)
(0.4)*
Wine
OPAL
4.1
1.4
5.2
6.5
1.0
5.7
(0.5)*
(0.3)
(0.8)*
(0.9)*
(0.5)
(0.6)*
CSWN
3.5
2.0
5.3
9.2
0.7
8.9
(0.5)*
(0.7)
(0.9)*
(1.2)*
(0.2)
(1.2)*
CNE
3.9
0.9
3.3
15.5
3.1
12.4
(0.8)*
(0.6)
(0.4)*
(5.0)*
(1.0)
(5.0)*
Water
OPAL
4.3
2.3
6.4
11.5
2.1
10.1
(0.6)*
(0.9)
(1.4)*
(5.2)*
(1.8)
(5.3)*
CSWN
0.7
0.8
0.4
1.0
0.9
0.4
(0.3)
(0.1)
(0.2)
(0.3)
(0.3)
(0.2)
CNE
0.6
1.1
0.8
0.6
0.9
0.9
(0.2)
(0.2)
(0.5)
(0.3)
(0.6)
(0.6)
OPAL
1.0
1.3
0.6
1.1
0.6
0.8
(0.8)
(1.0)
(0.3)
(0.3)
(0.2)
(0.2)
STBL, Interval between staining and baseline; BBL, interval between bleaching and baseline; BST, interval between bleaching and staining; CSWN, Colgate Simply
White Night; CNE, Crest Night Effects; OPAL, Opalescence Quick.
*
Indicates clincially unacceptable value (DEab*$3.3).
source and specimen was standardized by the use of a
1-mm glass slide. The end of the light guide was in contact with the cover glass during the light-polymerization
process. Afterward, all specimens were stored in distilled
water for 24 hours at 37°C to ensure complete polymerization. The top surfaces of all specimens were then polished with fine and superfine polishing disks (Sof-lex;
3M ESPE) with a slow-speed handpiece.
Color testing
Color of the specimens was measured with a spectrophotometer (Color Eye 7000; GretagMacbeth LLC,
New Windsor, NY) against a white background using
CIELAB color space relative to CIE standard illuminant
D55 at baseline, after staining, and after bleaching. The
color differences (DEab*) between the 3 measurements
were calculated as follows45:
DEab ¼ ½ðDL Þ2 1 ðDa Þ2 1 ðDb Þ2 1=2
where L* is lightness, a* is green-red (2a*=green; 1a*=
red), and b* is blue-yellow (2b*=blue; 1b*=yellow).
A perceptible discoloration that is DEab*.1.0 will be
referred to as acceptable up to the value DEab*=3.3 in
subjective visual evaluations made in vitro under optimal
lighting conditions.15,30
Staining process
Forty-five specimens of each composite resin were
separated into 3 groups (n=15). All specimens in each
group were immersed in 1 of the 2 staining solutions
(coffee or red wine) or distilled water (control) for 3
hours per day at room temperature over a 40-day test
period. Solutions were changed daily. Coffee group
specimens were immersed in vials containing 50 mL
of freshly brewed regular coffee per vial (Auroma
Paramount Coffee, Lansing, Mich); wine group specimens were immersed in vials containing 50 mL of red
wine (Concha y Toro Frontera Cabernet Sauvignon
2002; Merlon, Chile); and control group specimens
were immersed in distilled water. The vials were
sealed with parafilm (Pechiney Plastic Packaging Inc,
FEBRUARY 2006
Menasha, Wis) to prevent evaporation of the staining
solution. After each staining period, the specimens
were gently rinsed with distilled water, air dried, and
stored in distilled water at 37°C.
Bleaching process
Three bleaching agents were used in this study
(Table I). The 15 specimens in each staining group
were further divided into 3 subgroups. Specimens in
each subgroup (n=5) were bleached by one of the
bleaching agents. The bleaching agents were painted
on the top surface of the specimen according to the
manufacturers’ instructions. All bleaching agents were
applied at room temperature for 8 hours per day for
14 days to simulate the bleaching process. To be consistent with the other 2 paint-on products, Opalescence
Quick was applied for a time period that far exceeded
the manufacturer’s recommended time of no more
than 2 hours per session. After bleaching, the specimens
were rinsed with tap water for 1 minute to remove the
bleaching agents, blotted dry, and stored in distilled
water at 37°C.
A limit of DEab*#3.3 was interpreted as a clinically
acceptable difference in this study.46 One-way and 2way analysis of variance (ANOVA) tests were used to
analyze the data if the normality and equal variance
assumptions were met. Statistical software (SPSS 11.5
for Windows; SPSS Inc, Chicago, Ill) was used to perform the analysis. Fisher’s protected least significant
difference (PLSD) intervals were calculated (a=.05) to
compare the group mean values. If the data did not
meet the assumptions for ANOVA, a nonparametric
analysis (Kruskal-Wallis test and Mann-Whitney test)
was used to analyze the data.
RESULTS
Mean values and SDs of DEab*s for intervals of staining and baseline, bleaching and baseline, and bleaching
and staining are listed in Table II. After staining, FS
and EX both had clinically significant discoloration
(DEab*.3.3) for the coffee and wine groups, and FS
139
THE JOURNAL OF PROSTHETIC DENTISTRY
VILLALTA ET AL
Table III. One-way ANOVA of color change from baseline after staining for EX (control group included)
Source
Corrected model
Intercept
Stain
Error
Total
Corrected total
Type III Sum of squares
df
Mean square
F
P
98.083(a)
362.895
98.083
12.501
473.480
110.585
2
1
2
42
45
44
49.042
362.895
49.042
.298
64.761
1219.186
164.761
,.001
,.001
,.001
P,.05 denotes statistically significant difference.
Table IV. Two-way ANOVA of color change from baseline after bleaching for EX
Source
Corrected model
Intercept
Stain
Bleach
Stain 3 Bleach
Error
Total
Corrected total
Type III Sum of squares
df
Mean square
F
P
11.713(a)
74.061
4.379
3.262
4.072
12.987
98.761
24.700
8
1
2
2
4
36
45
44
1.464
74.061
2.189
1.631
1.018
.361
4.058
205.292
6.069
4.520
2.822
.002
,.001
.005
.018
.039
P,.05 denotes statistically significant difference.
was more affected by the wine solution. Overall, the
control group (distilled water) had the least color
change in the 3 intervals for both materials. After bleaching, the color of both EX and FS specimens returned to
the baseline. The color differences between bleaching
and baseline were less than 3.3 for all the groups. The
data for EX met the equal variance assumption, and a
1-way ANOVA was performed for the color change after
staining (Table III), while a 2-way ANOVA was used to
analyze the color change after bleaching (Table IV).
Fisher’s PLSD intervals (P=.05) for comparisons of
mean values among the 3 stain solutions (including control group) was 0.20. The results of the statistical analysis showed that the staining solution had significant
influence (P,.001) on the color change for EX specimens. There was no difference between coffee and
wine groups, whereas these groups were significantly
different (P,.05) from the control group. For the color
change between bleaching and baseline, the staining
solutions, bleaching agents, and interaction between
the 2 variables all had significant influence (P,.05).
Data for FS did not meet the equal variance requirement of ANOVA. For the color change after staining,
the Kruskal-Wallis test showed that the stain solution
had significant influence on the color change (P,.05)
of the specimens; the Mann-Whitney test indicated
that all 3 stain solutions (coffee, wine, and water) were
significantly different from each other (P,.01) with respect to the color change of FS specimens. Wine had
the most significant discoloration effect on FS, whereas
the specimens in water showed the least color change. As
there is no nonparametric equivalent of the 2-way
140
ANOVA, the data relating to color change after bleaching was not analyzed by a statistical method. The data
showed that all 3 bleaching products had a clinically significant effect on the removal of stain from discolored
FS specimens. The color differences between bleaching and baseline for all the groups were less than 3.3
(the clincially acceptable color change), even for the significantly discolored specimens in coffee or wine groups
(Table II).
DISCUSSION
After staining, both composite resins tested had perceptible color changes (DEab* between 3.5 and 15.5).
Low pH and alcohol may affect the surface integrity of
composite resins and cause staining. These results are
similar to those reported by Stober et al.22 The effect
of staining solutions on color changes of composite
resins was material dependent. This result is consistent
with another study.11 The staining susceptibility of a
material may be attributed to its resin or filler type. As
purported by the manufacturer, Filtek Supreme (FS) is
a nanocomposite with a primary 20-nm silica filler and
loosely bonded cluster zirconia/silica particle size ranging from 0.6 to 1.4 mm. Its resin matrix is composed of
Bis-GMA, UDMA, Bis-EMA, and TEGDMA. As purported by the manufacturer, Esthet X (EX) is a microhybrid composite containing BisGMA, BisEMA, and
TEGDMA, and 0.6- to 0.8-mm-sized fillers. FS demonstrated more discoloration than EX for the 2 staining
solutions, especially for the wine group. As FS and EX
had different compositions, FS might absorb a staining
VOLUME 95 NUMBER 2
VILLALTA ET AL
substance such as coffee or red wine more easily than EX,
as seen in other studies.17,18
It is interesting to note that the color of stained
specimens returned to baseline after bleaching for all
the groups tested even after a large discoloration due
to staining, especially for the wine group of FS. The results of this study showed how effective the bleaching
agents were in removing the exterior stainings for dental resin composites. Although the post hoc test showed
that there were significant differences among the
bleaching agents, the color differences between bleaching and baseline were acceptable clinically (DE,3.3).
However, a limitation of this study is that no negative
control was used during the bleaching stage, as the
purpose of this study was to compare the effect of 3
commercial bleaching products. Thus, the study fails
to prove that the stained specimens would not return
to their original color with an innert paste. Therefore,
the tentative conclusion of the study was that carbamide
peroxide was responsible for removing stain from the
surface of the specimens, and that the different concentrations of carbamide peroxide (16%, 18%, and 35%
for Crest Night Effects, Colgate Simply White Night,
and Opalescence Quick, respectively) had clinically similar effects on the color change of composite resins
tested.
When composite resins were immersed in water, the
color differences were imperceptible and clinically acceptable. This observation confirms that water sorption
by itself did not alter the color of composites to a considerable extent.16 The results after bleaching showed that
bleaching did not affect the composite resins, even after
8 hours of application of Opalescence Quick over a
period of 14 days. These results are consistent with previous studies for the low concentration of carbamide
peroxide bleaching products,34-36 but not for the high
concentrated bleaching agent.34,37 Monaghan et al37
and Canay and Cehreli34 reported perceptible color
change for the composite resins bleached by 35% hydrogen peroxide and 10% hydrogen peroxide, respectively.
This observation could be the reason for the disparities
between that study and the present study, as other components in commercial products may contribute to the
bleaching process as well.30
The bleaching mechanism for teeth is that the active
agents (peroxide solutions) can flow freely through the
enamel and dentin and oxidize the pigments in the
teeth.24 The results of the present study indicated that
the color change of composite resins after bleaching
was probably due to superficial cleansing of the specimens, not intrinsic color change.
Opalescence Quick is an in-office bleaching system
with a recommended treatment time of no more than
2 hours. It was applied on the surface of specimens
for 8 hours per day in this study to be consistent with
the other 2 paint-on products tested. It appears that
FEBRUARY 2006
THE JOURNAL OF PROSTHETIC DENTISTRY
prolonged contact with composite resins did not
increase the bleaching effect.
Although bleaching agents can successfully remove
the exterior staining from composite resins, they will
not bleach them, whereas they can effectively bleach
teeth.25,26 Therefore, after bleaching, the composite
resin restoration may not match the surrounding
bleached tooth structure. Also, bleaching can increase
the surface roughness of composite resins; therefore,
the restoration may stain more easily after bleaching.32,33 Bleaching agents should be used cautiously to
remove the exterior stain on the surface of composite
resin restorations. This study evaluated only A2 shades
of both materials; thus, the results may not be applicable
to other shades.
CONCLUSIONS
Different composite resins reacted differently in the 2
staining solutions. FS and EX specimens had clinically
significant discoloration (DEab*.3.3) in both the coffee
and wine solutions, and FS was more affected by the
wine. After bleaching with 3 types of bleaching agents,
discoloration was removed from the composite resins.
The authors thank Dr Jay Kim, professor, Loma Linda University,
School of Dentistry for his help with the statistical analysis.
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Reprint requests to:
DR PATRICIA VILLALTA
BIOSCIENCE RESEARCH CENTER, COLLEGE
NOVA SOUTHEASTERN UNIVERSITY
3200 SOUTH UNIVERSITY DRIVE
FT LAUDERDALE, FL 33329
FAX: 945-262-1782
E-MAIL: pvillalt@nova.edu
OF
DENTAL MEDICINE
0022-3913/$32.00
Copyright Ó 2006 by The Editorial Council of The Journal of Prosthetic
Dentistry.
doi:10.1016/j.prosdent.2005.11.019
VOLUME 95 NUMBER 2
Patricia Villalta