Download Spectrophotometric evaluation of color changes of

RPG Rev Pós Grad
2011;18(1):20-7
Spectrophotometric evaluation of color changes of
esthetic brackets stored in potentially staining solutions
MARCOS ROGÉRIO DE MENDONÇA*, AUBREY FERNANDO FABRE**, MARCELO COELHO GOIATTO***, OSMAR APARECIDO
CUOGHI*, LÍDIA PIMENTA MARTINS**, ANA CAROLINE GONÇALES VERRI**
Adjunct Professor, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) –
Araçatuba/SP, Brazil.
**
Postgraduate student, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) –
Araçatuba/SP, Brazil.
***
Adjunct Professor, Department of Dental Materials and Prosthetic Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) –
Araçatuba/SP, Brazil.
*
Abstract
The purpose of this study was to evaluate, in vitro,
the chromatic behavior of esthetic brackets stored in
potentially staining solutions. The sample were divided
into four groups according to the commercial brand
and stored in four different solutions (distilled water,
cola soda, coffee and mouthrinse) at 37°C for 14 days.
Possible color changes measured according to the CIE
L*a*b* color system with a spectrophotometer at five
intervals of time after storage. The statistical analysis
was carried out using ANOVA to 1%, Tukey’s tests and
decomposition of interactions with a significance level
of 5%.The color changes were dependent on the solution, storage time and the brand of brackets. The largest color changes were observed in the G3, followed by
G2, G1/G4. The esthetic brackets do not present satisfactory and stable chromatic behavior.
Descriptors
Color. Orthodontic brackets. Spectrophotometry.
Introduction
The increasing demand by the adult population42
for orthodontic treatment has led to the use of esthetic
Corresponding address:
Marcos Rogério de Mendonça
Disciplina de Ortodontia – Faculdade de Odontologia de Araçatuba
– Universidade Estadual Paulista Júlio de Mesquita Filho
(UNESP)
Rua José Bonifácio, 1.193
CEP 16015-050 – Araçatuba/SP, Brazil
Phone: 55 (18) 3636-3236
Email: [email protected]
20
brackets14.The plastic brackets, developed in 196930,
still present several problems, such as limited torque
control3,36, excessive wear and structural fragility1,3, water absorption16, low bond strength18, high friction with
orthodontic wires7, outstandingly high color instability13, and structural deformation53. Thereafter, the original composition was modified with the incorporation of
glass fibers or ceramic particles into the polycarbonate
polymer matrix, resulting in the so called “composite”36
brackets, as well as the development of new types of
polymers. Nevertheless, these problems have not yet
been completely resolved3,12,13,36.
In an attempt to eliminate the problems with polymeric accessories, ceramic brackets were developed in
19868,44, used in two forms: monocrystalline or polycrystalline17. The polycrystalline is more widely used, more
opaque and presents less optical clarity9,44. However,
there are still some limitations, such as staining9,24, frictional resistance8,9,15,17,44, friability2,39, abrasion of antagonist teeth47, and problems with removal27.
The color changes in esthetic brackets are of a multifactorial origin44. Discoloration of dental materials may
be the result of intrinsic factors such as water absorption, incomplete polymerization of adhesives or resins,
matrix composition of the material, content and size of
reinforcement particles5,22,44, brand28, tone45, or extrinsic
factors such as ingestion of food dyes containing caffeine
(coffee, tea, colas), mouthrinse use, saliva29, nicotine33,
lipsticks11,44, heat13, time and polymerization intensity21.
Objective
Therefore, the objective of this study was to evaluate the color changes of esthetic brackets after storage
in potentially staining solutions. The null hypothesis to
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
be tested was that the esthetic brackets did not change
color after contact with dye solutions.
Material and Methods
Brackets
For this study, 160 esthetic brackets for central incisors on the right side were used, of the Roth type, slot
0.022” x 0.028”, of different brands (Table 1).
Solutions
Four different solutions were used: (1) distilled
water; (2) cola soda (Coca-Cola®, produced by Spaipa,
Marília, SP, Brazil); (3) soluble coffee (Nescafé®, produced by Nestlé of Brazil Ltda, Araras, SP, Brazil), prepared according to the manufacturer’s recommendations;
(4) mouthrinse containing alcohol (Listerine® Tartar
Control, produced by Altana Pharma Ltda, Jaguariúna,
SP, Brazil, Custom Johnson & Johnson Industrial Ltda).
Spectrophotometric analysis
The color change readings were made using a reflectance spectrophotometer (Un-Visible Spectrophotometer
UV-2450®, manufactured by Shimadzu, Kyoto, Japan)
with wavelength range 380-780 nm and standard illumination D654. To allow the standard positioning of the
brackets during the reading, four individual polyvinyl
chloride (PVC) matrices, black color were fabricated,
one for each brand of bracket, with a standard fitting
and precise positioning of the bracket-matrix set for later
reading the bracket color (Figure 1). Before the readings,
each bracket was washed by ultrasound for one minute,
and properly dried on paper towels. The color changes to
be calculated by the CIE L*a*b*system10, and the total
color difference (ΔE*) was calculated by the following
equation: ΔE* = [(ΔL*)² + (Δa*)² + (Δb*)²]½. The L* parameter corresponds to the value or degree of lightness or
brightness and a*b* values of chroma, where +a* is red
and -a* is green, +b* is yellow and -b* is blue.
Data collection
Study groups
Four groups were formed with 40 brackets for
group and ten brackets for solution (Table 1).
Storage
Each bracket was stored in a polypropylene microtube with cover, enumerated, and stored at 37°C. All solutions and microtubes were regularly renewed after every
24 hours of storage. The total storage period was 14 days.
The color change reading was taken by means of
the software attached to a computer with a previously
established configuration, and the value of ΔE* was automatically obtained for each bracket in each experimental period, generating a mean ΔE* for each experimental
time, bracket brand and solution. The experimental times
were: T0 (before the initial immersion), T1 (1 day after
the initial immersion), T3 (3 days), T7 (7 days), T10 (10
days) and T14 (14 days after immersion).
Table 1
Brackets and its constitution
Group
Bracket
Manufacturer
Type
Material
Lot number
Solutions
G1
Composite®
Morelli
Orthodontics,
Sorocaba, SP,
Brazil
Plastic
Polycarbonate
reinforced with
glass fiber
(30%)
1066487
G2
Silkon Plus™
American
Orthodontics,
Sheboygan, WI,
USA
Plastic
Polycarbonate
with ceramic
particles (30%)
0201
G3
Invu™
TP Orthodontics,
La Porte, IN, USA
Ceramic
Polycrystalline
alumina, with
polycarbonate
base
1258C05
G4
Transcend™
6000
3M/Unitek,
Monrovia, CA, USA
Ceramic
Polycrystalline
alumina
0904005766
Distilled water
Cola soda
Coffee
Mouthrinse
Distilled water
Cola soda
Coffee
Mouthrinse
Distilled water
Cola soda
Coffee
Mouthrinse
Distilled water
Cola soda
Coffee
Mouthrinse
Brackets for
solution
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
21
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
Figure 1 - Bracket-matrix set. (a) posterior view; (b) demarcations to position; (c) brackets attached.
Measurement of pH change
The pH of the solutions was measured before and after 24 hours of initial immersion and storage in polypropylene microtubes (Table 2), using ion analyzer (Orion
Research 720A, Orion, USA) coupled to a magnetic stirrer (NT 101, Nova Técnica, Piracicaba, SP, Brazil).
Statistical analysis
Statistical analysis was performed using the SAS
System™ and Microsoft Excel® programs. According
to the Kolmogorov-Smirnov test, data distribution was
normal with p=0.0539. Next, an arcsine transformation
was performed and the three-factor analysis of variance
(brand, solution and time) was applied (Table 3). Since
there were no significant differences between any of the
sources of variation, the Tukey’s test was applied and the
decomposition of the interactions brand*solution*time
was performed. The level of significance was 1% for
analysis of variance and 5% for the decompositions.
Results
The mean color change values and their standard
deviations (sd) during the experiment are shown in
Table 3. Tests were also performed for comparisons between brands, solutions and time (Tables 4 to 6).
Group 1
In the distilled water solution, when chronologically
compared, ΔE* values were statistically significant. In the
soda, the values from ΔE* showing a gradual increase over
time, with statistically significant differences. Similarly, the
brackets stored in coffee showed a gradual increase in the
22
Table 2
pH variation during 24 hours of immersion
pH variation
Solution
Before
24 hours after
immersion
immersion
Distilled water
6,34
6,42
Cola soda
2,61
4,80
Coffee
4,93
4,81
Mouthrinse
4,33
4,20
value of ΔE*, statistically significant. When stored in the
mouthrinse, only the value of ΔE*3 was found to be statistically significant when compared with the other values.
(Figure 2)
Group 2
In distilled water the values not showing statistically significant difference. In the soda, showed a
gradual increase over time, with statistically significant
difference. The brackets stored in coffee also showed a
gradual increase in the value of ΔE* with over time, and
were statistically significant. In the mouthrinse only the
value of ΔE*7 was found to be statistically significant
when compared with the other values. (Figure 3)
Group 3
For distilled water, statistically significant difference
was found only between the values of ΔE*1. In the soda,
showed a gradual increase over time, with no statistically
significant difference, except between the values of ΔE*1
and ΔE*3. For coffee, no statistically significant difference
were found between the values of ΔE*3, ΔE*7 and ΔE*10,
despite showing a tendency towards a gradual increase in
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
Group
G1
G2
G3
G4
Table 3
Mean values of ΔE* and standard deviation of each group, according to the solution over time
ΔE* mean and standard derivation for each solution
ΔE*
Distilled water
Cola soda
Coffee
Mouthrinse
ΔE*1
0,445a
0,802b
1,595c
0,671ab
(0,194437)
(0,210069)
(0,307038)
(0,253616)
ΔE*3
0,725b
1,464c
2,868de
1,254ci
(0,33768)
(0,39164)
(0,57024)
(0,307398)
ΔE*7
0,408a
2,732d
3,822g
0,648ab
(0,287626)
(0,733315)
(0,710239)
(0,352067)
ΔE*10
0,553ab
3,413e
5,198fh
0,554ab
(0,300335)
(0,902762)
(0,515554)
(0,31248)
ΔE*14
0,750b
4,449fg
5,679h
0,450ab
(0,450876)
(0,600804)
(0,514856)
(0,194594)
ΔE*1
0,810a
1,468b
2,293cd
0,817al
(0,44572)
(0,261398)
(0,269033)
(0,347245)
ΔE*3
0,696a
1,96c
3,338h
0,860al
(0,302515)
(0,446468)
(0,375908)
(0,487761)
ΔE*7
0,772a
2,744d
4,312i
1,061l
(0,371118)
(0,435717)
(0,36772)
(0,29614)
ΔE*10
0,606a
3,721e
5,188j
0,992al
(0,405112)
(0,561831
(0,518626)
(0,342241)
ΔE*14
0,750a
4,716f
6,416k
0,820al
(0,450876)
(0,72062)
(0,521349)
(0,302288)
ΔE*1
0,597a
1,211bc
8,143g
32,825j
(0,407923)
(0,210103)
(0,609955)
(0,548579)
ΔE*3
1,295b
1,364bc
10,015h
4,513fk
(0,387076)
(0,325856)
(0,623151)
(0,622505)
ΔE*7
1,389b
1,984bd
11,143h
4,348fk
(0,34812)
(0,691828)
(0,413173)
(0,43764)
ΔE*10
1,422b
3,574e
11,389h
5,251fl
(0,286543)
(0,772402)
(0,430154)
(0,944357)
ΔE*14
1,516b
4,554f
12,058i
5,661l
(0,263363)
(0,909593)
(0,550814)
(0,638617)
ΔE*1
0,552ª
3,596b
0,898c
0,727ac
(0,314812)
(0,440585)
(0,254899)
(0,345545)
ΔE*3
0,632a
3,296b
2,097d
0,472f
(0,349374)
(1,247061)
(0,588313)
(0,302354)
ΔE*7
0,779a
3,350b
3,063b
0,470f
(0,571731)
(0,496767)
(0,849484)
(0,299518)
ΔE*10
0,537a
3,344b
3,725b
0,451f
(0,346187)
(0,712245)
(0,624664)
(0,23421)
ΔE*14
0,740a
3,511b
4,694e
0,412f
(0,338625)
(0,728842)
(0,449647)
(0,1641)
Different letters represent statistically significant difference intragroups.
Table 5
Comparison of the potential of the staining solutions
Solution
Number of measures Average Tukey*
Distilled water
200
0.085010
A
Cola soda
200
0.165116
B
Coffee
200
0.223280
C
Mouthrinse
200
0.135907
D
Table 4
Comparison of performance between groups
Group
Number of measures
Average Tukey*
G1
200
0.125110
A
G2
200
0.137257
B
G3
200
0.223390
C
G4
200
0.123557
A
*
Different letters represent statistically significant difference.
*
Different letters represent statistically significant difference.
23
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
the value of ΔE*. In the mouthrinse, the values indicating
that there was no statistically significant difference, except
between the values of ΔE*3 and ΔE*7 (Figures 4 and 5).
Table 6
Influence of time on the average value of ΔE* during the
storage period
Group Number of measures
Average
Tukey*
T1
160
0.145502
A
T3
160
0.137960
B
T7
160
0.148316
A
T10
160
0.159168
C
T14
160
0.170695
D
Group 4
For the distilled water solution the values of ΔE*
were not statistically significant. In the soda, the values no
showed statistically significant difference. In coffee, despite
the trend towards gradual increase over time, there was no
statistically significant difference between the values of
ΔE*7 and ΔE*10. In the mouthrinse, only the value of ΔE*1
was found to be statistically significant, despite the gradual
reduction in the values of ΔE* over time. (Figure 6)
Considering the solutions used and the period of time
of the trial as an overall treatment for the studied brands,
the mean values of ΔE*, in ascending order, were found
for the G3 and G1, followed by G2 and G4 (Table 4). When
comparing the means of the solutions, it was possible to
prove that coffee caused the greatest color change, followed by soda, mouthrinse and distilled water (Table 5).
When comparing the values of ΔE* versus time, it was
observed that higher color change values were recorded
in T14, indicating that the longer the storage period, the
greater the trend towards change color (Table 6).
*Different letters represent statistically significant difference.
¨E*
24
distilled water
soda
coffee
mouthrinse
3
2
1
0
1
!
3
7
10
14
time (days)
Figure 2 - Behavior of G1.
¨E*
7
6
5
39
It has been shown that the brand, the solution and
storage time influence the degree of color change of
the materials49, which can also be observed in this experiment (Tables 4 to 6), since all bracket brands tested
underwent color change in all solutions over time. The
storage period was taken with the purpose of exposing
the brackets to extreme conditions to assess the degree
of staining, since after this period, there is a trend towards saturation6. Moreover, a period of 24 hours of
artificial treatment is considered very short to investigate the color change of the composites43. The choice
of solutions was based on the literature11-13,20,31,38,43,51 and
the products routinely used by orthodontic patients.
5
4
Discussion
As esthetics is their main advantage over metal brackets , the stability and color match of esthetic brackets is
a cause for concern. Some authors have attempted to correlate the numerical values of color changes with visual
perception, by means of spectrophotometry23 of esthetic
brackets12,13,25,26,51 and composite resin or prosthetic resto
rations11,35,38,40,41,43,48. However, these thresholds of reference for the ΔE* cannot be compared with those in this
study because the results are dependent on the methodology, moreover, the brackets tested were different.
6
4
distilled water
soda
coffee
mouthrinse
3
2
1
0
1
3
7
10
14
time (days)
Figure 3 - Behavior of G2.
!
¨E*
35
30
25
20
distilled water
soda
coffee
mouthrinse
15
10
5
0
1
!
3
Figure 4 - Behavior of G3.
7
10
14
time (days)
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
shows the greatest potential of this staining solution
(Table 5), in agreement with previous studies38,49. This
color change was due to the large amount of yellow pigments in the solution, by adsorption and absorption11,46,
which could be corroborated the increase in the values
of the coordinate b*.
Figure 5 - Behavior of G3 over time (T0 to T14) in distilled water (a),
soda (b), coffee (c) and mouthrinse (d).
¨E*
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
distilled water
soda
coffee
mouthrinse
1
!
3
7
10
14
time (days)
Figure 6 - Behavior of G4
Among the evaluated groups, color changes were
observed in the G1 and G3 in distilled water, resulting
from the loss of brightness (L*) caused by water absorption, since the value of L* was decreased in relation to baseline (T0). Water absorption by dental materials can be explained by differences in composition,
size, quantity and distribution of particles within the
matrix38,48. Water absorption into the G2 and G4 brackets
was lower, with no statistically significant difference
between them.
In the soda, only G4 underwent no statistically significant change in color, although the mean ΔE* value
over time was relatively high. In the pH measurement
of the solutions, it was found that the soda had the lowest initial pH (Table 2), which possibly affected the surface integrity of the specimens5,6, favoring color change
probably due to the absorption of pigments from the
solution by the brackets.
For all groups stored in coffee there was statistically significant difference, with higher ΔE* values, which
In mouthrinse, all groups suffered color change, and
the highest ΔE* values were observed for G3. According
to a previous study20, 12 hours of immersion is equivalent to a period of one year under clinical conditions, that
corresponding at only one daily rinse with duration of
two minutes, with great compatibility with the values
found from T1 to T3. Some authors34,37 reported that alcohol tends to alter the surface properties of composites,
increasing the area of adsorption of pigments. Since the
color of the mouthrinse was blue, the coordinate values
L* and b* decreased gradually, which contributed to the
higher ΔE* values for the G3, particularly in T1, possibly
due to some type of specific reaction with some constituent of the ceramic matrix, since no other group showed
similar behavior. According to literature20,32 whether or
not mouthrinses contain alcohol in their composition,
they affect the microhardness of restorative materials.
Other authors19,52 reported no effect, saying that the behavior of this solution is no different from that of distilled
water that also was observed in this study.
Although the literature49 reports that the low pH
and high concentration of alcohol tend to increase the
potential for staining of certain products, this study
showed that the factor most responsible for color
changes in the brackets was the amount and type of
pigment in the solution, which is in agreement with
previous studies38,48. It was also reported that changes in optical properties (opacity/translucency) of the
polymeric matrix5 may be responsible for clinically
observed color change.
Due to these complications, a number of variables
(intrinsic and/or extrinsic) should be considered in the inference clinic50. The complex interaction of factors in the
oral environment such as temperature, humidity, biofilm,
salivary pellicle, food, and beverage consumption can affect dental materials. Furthermore, the combination and
the simultaneous effects of different foods or beverages,
mouthwash, saliva, and brushing were not evaluated.
Although ceramic brackets present better performance
chromatic than the polycarbonate type8, this laboratory
study showed that this superiority is not always true and the
association between laboratory results and clinical experience should guide the choice of the best accessories.
25
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
This study also showed that solutions used in
everyday life are able to cause color changes in esthetic brackets, which may help to clear the frequent
concern regarding the necessary minimum time required for the solutions to cause color change. In this
study, the experimental times used were overestimated when compared to the times prevalent in the
patients’ life. Nevertheless, the influence of cosmetic
color enhancements in patients who make excessive
use of these solutions can have a strong correlation
with the results shown.
Conclusion
The results presented led to the rejection of the
null hypotheses, and all groups tested underwent color changes when immersed in the studied solutions.
Therefore, the esthetic brackets do not present satisfactory and stable chromatic behavior.
Acknowledgments
The authors thank Morelli Orthodontics for the donation of the Composite® brackets.
Resumo
Avaliação espectrofotométrica das alterações cromáticas de braquetes estéticos
armazenados em soluções potencialmente corantes
O objetivo deste estudo foi avaliar, in vitro, o comportamento cromático de braquetes estéticos armazenados
em soluções potencialmente corantes. As amostras foram divididas em quatro grupos de acordo com a marca comercial e imersas em quatro soluções diferentes (água destilada, refrigerante à base de cola, café e enxaguatório
bucal) a 37ºC, por 14 dias. As possíveis alterações de cor foram medidas de acordo com o sistema CIE L*a*b*
por meio de um espectrofotômetro em cinco intervalos de tempo após armazenamento. A análise estatística foi
conduzida usando ANOVA a 1%, testes de Tukey e decomposição das interações com nível de significância de 5%.
As alterações de cores ocorreram conforme solução, tempo de armazenamento e marca dos braquetes. As maiores
variações cromáticas foram observadas no G3, seguido por G2, G1/G4. Os braquetes estéticos não apresentam comportamento cromático estável e satisfatório.
Descritores
Cor. Braquetes ortodônticos. Espectrofotometria.
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Received in: 24/2/11
Accepted in: 31/3/11
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