Article_5_3_3
DENTAL MATERIALS
EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL PROPERTIES OF AGED
Original Article
RESIN COMPOSITES
Ingrid Fernandes Mathias-Santamaria1a , Ayla Macyelle de Oliveira Correia1b, Débora Cristina Barbosa Dantas1c,
Márcia Carneiro Valera1d, Renata Marques de Melo2e, Eduardo Bresciani1f*
1
Department of Restorative Dentistry, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil
2
Department of Dental Materials and Prosthodontics, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil
DDS, MSc, PhD Student
a,b,c
d
DDS, MSc, PhD, Full Professor of Endodontics
e
DDS, MSc, PhD, Researcher Professor
f
DDS, MSc, PhD, Associate Professor of Operative Dentistry
ABSTRACT DOI: 10.25241/stomaeduj.2018.5(3).art.3
OPEN ACCESS This is an Open Access
Objectives: To evaluate the effect of bleaching on colour, gloss, translucency, and article under the CC BY-NC 4.0 license.
microhardness of two types of resin composites (Charisma Classic and Filtek Z350 Peer-Reviewed Article
XT), previously aged. Citation: Mathias-Santamaria IF, de Oliveira Correia
Materials and methods: Forty specimens of each material were artificially aged for AM, Barbosa Dantas DC, Carneiro Valera M, de Melo
RM, Bresciani E. Effect of whitening on the optical and
300 hours (UV-accelerated aging). Specimens were then treated with 35% hydrogen mechanical properties of aged resin composites. Stoma
peroxide (Whiteness HP) in four 15-minutes sessions, totaling one hour of bleaching. Edu J. 2018;5(3):161-167
Colour coordinates CIE L*a*b* and parameters of translucency (PT) were measured Academic Editor: Nicoleta Ilie, Dipl-Eng, PhD,
using a spectrophotometer (CM2600d – Konica Minolta), surface gloss readings were Professor, Ludwig-Maximilians-Universität München,
München, Germany
performed with a glossmeter (Novo-Curve – Rhopoint TM), and microhardness was
assessed using a hardness device (FM-700, Future-Tech). Measurements have been Received: August 21, 2018
Revised: September 05, 2018
performed after artificial aging as well as after the first and last bleaching protocol. Acccepted: September 11, 2018
Data were analyzed by two-way ANOVA and two-way repeated measures ANOVA, Published: September 17, 2018
followed by Tukey’s test (5%). *Corresponding author: Assoc. Professor Eduardo
Bresciani, DDS, MSc, PhD, Department of Restorative
Results: The bleaching procedures of aged resin composites decreased the gloss Dentistry, Institute of Science and Technology,
and increased the translucency, but did not alter colour and microhardness. São Paulo State University, Av. Eng. Francisco José
Longo, 777, São José dos Campos, SP, Brazil, ZIPCODE:
Conclusion: Bleaching procedures should be used carefully when resin composite 12245000, Tel:/Fax: +55 12 39479048, e-mail:
restorations are present. eduardob@ict.unesp.br
Keywords: colour, hardness, gloss, bleaching agents, composite resins. Copyright: © 2018 the Editorial Council for the
Stomatology Edu Journal.
1. Introduction studies [7-9] concluded that bleaching agents are able
Dental bleaching is a conservative alternative with high to reduce significantly the gloss of resin composites,
success rates for treating discoloured teeth [1]. Tooth thus changing the aesthetic property of restorations.
bleaching is a chemical process, which is performed Bleaching procedure alters the colour of resin composite
with peroxide, chlorine, or chloride based-products. materials [6], but not the translucency. The literature is
Among the products, hydrogen peroxide is the most still controversial regarding the microhardness of resin
commonly used agent. The bleaching process relies on composites after bleaching procedures. It has been
the decomposition of peroxide into free radicals, while reported that bleaching treatment with 10% carbamide
unstable molecules, such as tooth pigments, uptake peroxide decreased the surface microhardness of resin
electrons for stabilization [2]. Basically, the formed free composites by 15% of its baseline value [10]. However,
radicals break up the double-bonds of the pigment’s there are available studies on reduced [9,11,12] or even
complex chains, resulting in a lighter pigment. This increased [13] microhardness, when testing nanofilled
process represents the oxidative reaction of pigments resin composites.
within tooth structures. The influence of bleaching on resin composites is
Studies have reported that bleaching agents might explained by a surface degradation and the presence
affect the properties of resin composites; this of microcracks on the surface, which is aggravated over
influence is dependent on the bleaching agent and time [14]. Despite those studies, considering colour,
its concentration, as well as on the type of restorative gloss, translucency and surface hardness, the literature
material tested [3-6]. Microhybrid resin composites is not conclusive about the influence of bleaching
seem to undergo greater colour changes than treatment on the surface of different resin composites
nanohybrid ones; and the concentration of the [3,5].
bleaching agent seems to be less important than the To simulate clinical condition several in-vitro studies
time exposed to such products, although there are uses artificial aging of resin composites. For those,
reports stating the higher the concentration the greater artificial aging by UV light and moisture or water
the bleaching efficacy on a determined period of time immersion protocols [15] have been proposed [16,17].
[5]. Regarding surface gloss assessment, previous By employing artificial aging, the mechanical properties
Stomatology Edu Journal 161
EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL
PROPERTIES OF AGED RESIN COMPOSITES
of resin composites are negatively influenced over time
Original Article due to filler degradation [18], or matrix plasticization [19].
Table 1. Characteristics of resin composites tested in the present study.
Manu-
The influence of isolated artificial aging or bleaching Composite Shade Type Composition
facturer
LOT
procedures over resin composites is well documented.
Bis-GMA,
The association of both parameters is usually tested TEGDMA, barium
using a bleaching procedure followed by artificially aluminium fluoride
glass (0.02–2 Heraeus
accelerated aging. Studies with that purpose have
shown that colour and roughness of resin composites Charisma Micro- microns) and Kulzer,
A2 highly dispersive 010027A
were significantly changed depending on resin type Classic hybrid Siliciumdioxyde Hanau,
(0.02–0.07
[16,17]. microns), with 78%
Germany
To the best of our knowledge, there are limited studies filler content by
identifying potential problems that bleaching may result weight
on the properties of previously aged resin composites, Bis-GMA, Bis-
especially regarding the optical properties. Bleaching EMA, UDMA,
and TEGDMA;
employed over aged resin composite restorations is a 3M ESPE,
Filtek Nano- 20-nm nanosilica,
usual scenario faced in clinical practice. Therefore, the A2 and 5- to 20-nm St Paul, 96374
aim of this study is to evaluate the optical (colour, gloss Z350 XT hybrid zirconia nano
agglomerates, with
MN, USA
and translucency) and mechanical (microhardness) 78.5% filler content
properties of two types of resin composite, previously by weight
aged and whitened. The Null hypothesis is that none of Bis-GMA: bisphenol A-glycidyl ether dimethacrylate; UDMA: urethane
the variables (colour, gloss, translucency microhardness) dimethacrylate; TEGDMA: triethylene glycol dimethacrylate; Bis-EMA:
is affected by the bleaching procedure considering the ethoxylated bisphenol A-dimethacrylate.
independent variables tested (type of resin composite
and time of bleaching).
2. Materials and methods
2.1. Sample preparation
The characteristics of the tested resin composites are
shown in Table 1.
A total of 20 samples of each material were prepared
for assessing colour, translucency, and gloss. Resin
composite was placed in a single increment into
a standardized circular matrix, 6 mm in diameter
and 1 mm thick for specimen preparation. For the
microhardness assessment, a total of 20 samples of
each material were prepared, 3 mm in diameter and Figure 1. Sequence of the polishing step. A. Thickness standardization;
B. Specimen in position inside the metal holder; C. Polishing; D. Final
1 mm thick. The molds and materials were covered aspect.
with Mylar strips on the top and bottom and placed
between two cover glasses. Finger pressure was Table 2. Composition of the artificial saliva according to Göhring et al.,
2004.
then applied to extrude the excess of material and
to promote an even and smooth surface. Specimens Component mmol/l
were light-cured (Radii Cal curing light, SDI, Victoria,
Australia; 440-480 nm, 1200 mW/cm2) according to Hydrogen carbonate 22.1
the manufacturer’s instructions (20 seconds for both
Potassium 16.1
materials). The irradiance of the light-curing unit was
assessed with a radiometer (Ecel, Ribeirão Preto, Brazil) Sodium 14.5
prior to the fabrication of specimens. The samples were
stored in ultrapure water for 24 hours at 37°C, to allow Hydrogen phosphate 2.6
post-curing.
The specimens were positioned inside a metal Boric acid 0.8
holder, and the surface that would be treated with
Calcium 0.7
the bleaching therapy was polished with sequential
(P1200, P2400, and P4000 grit) aluminum oxide Thiocyanate 0.4
abrasive papers (FEPA-P, Struers, Ballerup, Denmark)
in a polishing device (DP-10, Panambra Industrial e Magnesium 0.2
Técnica SA, São Paulo, SP, Brazil) for 30 seconds on each
paper (Fig. 1). pH 7.4-7.8
2.2. Accelerated artificial aging irradiation at 765 W/m2, followed by one hour at 37
After polishing, the samples were artificially aged in a ± 5°C and no light irradiation, totaling 3 hours each
weathering machine (SUNTEST CPS+ - Atlas Material cycle. That protocol simulates exposure of 160 klux,
Testing Technology, Mount Prospect, Illinois, USA), corresponding to intense natural light, equivalent to
following ISO 7491 standard. One hundred aging one year of clinical use [20]. During the artificial aging,
cycles were performed (300 hours in total). Each samples were immersed in artificial saliva at 37 ± 1°C
cycle was composed of two hours at 55 ± 5°C and (Table 2) [21].
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EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL
PROPERTIES OF AGED RESIN COMPOSITES
2.3. Colour assessment
Original Article
The colour coordinates of each specimen were
assessed, under standardized ambient conditions,
according to the CIE L*a*b* system, using a reflectance
spectrophotometer (CM2600d, Konica Minolta, Osaka,
Japan). The device was adjusted to D65 standard
illuminant with 100% UV and specular component
included (SCI). The observer angle was set at 2° and
the device was adjusted to a small area view (SAV).
The colour of each sample was measured three times,
obtaining an average of L* a* b* chromatic coordinates,
as established by the Commission Internationale de
l’Eclariage (CIE), which locates the colour of an object in
a three-dimensional colour space. The L* axis represents
the degree of lightness within a sample and ranges
from 0 (black) to 100 (white). The a* axis represents the
degree of the green/red colour within the sample, while
the b* axis represents the degree of the blue/yellow
colour within the sample. The colour was measured
over white (L*: 84.95; a*: -0.38; b*: 2.93) and black (L*:
2.58; a*: -0.15; b*: -0.24) standard backgrounds (Ceram,
Staffordshire, UK) [22]. Optical contact between the
specimen and the backgrounds was improved by Figure 2. Schematic chart.
using an interfacing layer of a polyethylene glycol Tokyo, Japan), with a 25 g load for 10 seconds. Three
400 solution (LabSynth, Diadema, São Paulo, Brazil) random measurements were carried out on each
[22]. From the colour measurements after the artificial specimen and the average represented each data point.
aging and after the first or last week of bleaching, the
values of the changes of L* (ΔL), a* (Δa), and b* (Δb) 2.7. Bleaching
were calculated. Next, the total change in colour or the Bleaching procedures were performed in three sessions
variation in perception of colour of each specimen was one week apart from each other. In each session,
calculated, designated by the abbreviation ΔEab. Data specimens received a layer of 35% hydrogen peroxide
obtained using white background were used for colour gel (Whiteness HP, FGM Ltda., Joinville, Santa Catarina,
assessments. Colour variation was calculated using the Brazil) during four sessions of 15 minutes, totaling 1
following equation: hour. In between sessions, the specimens were stored
in ultrapure water under constant temperature in a
∆E*ab=[(∆L*)2+(∆a*)2+(∆b*)2]1/2 bacteriological oven (37°C + 1°C).
Colour, translucency, gloss and microhardness were
2.4. Translucency assessment analyzed considering the baseline (Reading 1), the first
Translucency was expressed using the translucency (Reading 2) and last (Reading 3) bleaching sessions,
parameter (TP), which was determined by calculating being the last two readings performed right after the
the colour difference between the L*, a* and bleaching protocol. Figure 2 shows a schematic chart
b* coordinates obtained over black and white illustrating the experimental design of this study.
backgrounds for each specimen, using the formula:
TP= [(LB* - LW*)2 + (aB* - aW*)2 + (bB* - bW*)2 ]1/2. 2.8. Statistical Analysis
Assumptions of the normal distribution (Kolmogorov-
The subscript B refers to the colour coordinates of Smirnov test) were checked for all the variables tested.
the specimens over the black background and the Data were statistically analyzed using STATISTICA
subscript W refers to those measurements over the software (StatSoft, version 8.0, 2010). Two-Way ANOVA
white background. was performed for colour analysis, followed by Tukey’s
test with 5% significance. All other parameters were
2.5. Gloss analysis analyzed by Two-way repeated measures ANOVA,
Surface gloss was measured using a glossmeter (Novo- followed by Tukey’s test with 5% significance.
Curve, Rhopoint TM, East Sussex, England), with a 2
mm × 2 mm area and a 60° geometry (light incidence),
with values expressed in Gloss Units (GU). The 3. Results
measuring principle of this device is based on a light 3.1. Colour change
beam incident to a surface at 60°, and the glossmeter The mean and standard deviation values of the colour
measures the intensity of the reflected light and change (∆E) for tested resin composites during bleaching
compares it to a reference value. Three readings were related to the artificial aging are presented in Table 3. In
carried out of each specimen and they were averaged relation to colour changes (∆E) after bleaching (Reading
to obtain a single value for each specimen during each 1-Reading 2 and Reading 1-Reading 3), both materials
assessment period. tested did not present significant differences (p > 0.05).
2.6. Microhardness analysis 3.2. Translucency
The surface microhardness (KHN) was assessed using The two-way repeated measures ANOVA showed
a Knoop Microhardness Tested (FM-700, Future-Tech, significant differences in TP for resin composites (p <
Stomatology Edu Journal 163
EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL
PROPERTIES OF AGED RESIN COMPOSITES
0.01) and readings (p < 0.01), with no interaction of
Original Article factors (p = 0.901). Charisma Classic overall presented
Table 3. Mean values (±SD) of colour change (∆E) and results of Tukey´s
test.
lower TP in comparison to Filtek Z350 XT. For both resin Charisma Classic Filtek Z350 XT
composites, increased translucency was observed over
Reading1-Reading 2 2.21(±0.95) Aa 1.92 (±0.44) Aa
time; this increase was detected after the first week
after bleaching for Charisma Classic, while Filtek Z350 Reading1-Reading 3 2.08(±1.14) Aa 2.44 (±0.66) Aa
XT presented increased TP only in the third week of In each row, distinct capital letters indicate significant difference between
bleaching (Table 4). resin composite while distinct lowercase letters in each column, indicate
significant difference among weeks (α = 0.05).
3.3. Gloss
Table 4. Mean values (±SD) of translucency parameter (TP) and results
Gloss values as a function of time (baseline (before of Tukey´s test.
bleaching and after aging), 1 and 3 weeks after
bleaching) are shown in Table 5. Reduction of gloss Charisma Classic Filtek Z350 XT
values was noticed after 1 week for Charisma Classic Reading 1 23.02 (±5.62) Aa 26.4 (±5.11) Ba
with no further reduction over time (p < 0.01). For Filtek Reading 2 33.16 (±1.95) Ab 37.31 (±3.88) Bb
Z350 XT, surface gloss reduction was detected only
Reading 3 30.9 (±2.39) Ab 35.42 (±4.18) Bb
after the third week of treatment (p < 0.01). In terms of
absolute gloss values, resin composite Charisma Classic In each row, distinct capital letters indicate significant difference between
presented lower gloss values. resin composite while distinct lowercase letters in each column, indicate
significant difference among weeks (α = 0.05).
3.4. Microhardness analysis Table 5. Mean values (±SD) of gloss and results of Tukey´s test.
The values obtained for KHN are shown in Table 6. Two- Charisma Classic Filtek Z350 XT
way repeated measures ANOVA showed significant
differences between the resin composite (p < 0.01) Reading 1 79.53 (±8.54) Aa 84.77 (±4.03) Aa
while the time (baseline, 1 and 3 week) was not (p = Reading 2 66.57 (±12.15) Ab 84.37 (±4.52) Ba
0.63), nor was the interaction between factors (p = Reading 3 63.42 (±9.1) Ab 67.5 (±5.24) Ab
0.87). Charisma Classic presented KHN mean values
In each row, distinct capital letters indicate significant difference between
lower than Filtek Z350 XT. resin composite while distinct lowercase letters in each column, indicate
significant difference among weeks (α = 0.05).
4. Discussion different fillers, both resin composites present Bis-GMA
The influence of bleaching and artificial aging in its composition, and it might have influenced the
procedures on the optical and mechanical properties presently assessed colour stability for both nanohybrid
of resin composite has been investigated [6,9,16]. It and microhybrid aged resin composites. Previous
was expected that the bleaching procedure had no studies on the effect of bleaching on the properties
effects on the properties studied. However, this was of aged composites reported conflicting results. The
not observed and, consequently, the null hypothesis discrepancies between those studies may be caused
was rejected. The results revealed that 35% hydrogen by the type of aging protocol, bleaching agents used
peroxide bleaching procedure was able to increase and total application time of agents or the type of resin
the translucency and reduce the gloss of aged resin composite tested. Some studies have shown a significant
composites. No differences were detected regarding colour change for resin composite Charisma [16] or Filtek
colour and microhardness variations. Supreme [9], while others did not [16]. Comparing the
The optical and mechanical properties of resin present data on aged resin composites to other studies
composites can be influenced by several factors, in which aging was not performed [5,7], the bleaching
including the aging process, bleaching procedures, as process resulted in similar patterns of colour alterations,
well by characteristics related to restorative material suggesting bleaching may behave similarly to aged and
[5,7,23-25]. The UV-accelerated aging has a photo- non-aged resin composite.
oxidative potential, by means of the action of both UV As reported by other studies [3,6], the potential effect of
radiation and water, inducing the cleavage of simple and bleaching treatment depends on the type, concentration
double carbon bounds found in the resin matrix, such of bleaching agent, and the resin composite brand. For
as Bis-GMA, UDMA and TEGDMA, being responsible for instance, it has been reported that Filtek resin composite
the material deterioration and changes in properties presented different behavior to colour change after
[9,23,26,27]. Regarding bleaching procedures, oxidative bleaching when compared to another nanohybrid resin
cleavage of polymer-chains by means of free prehydroxyl composite [3]. Moreover, 16% carbamide peroxide is
(HO2-) radicals, resulting from the degradation of the H2O2, reported to be more effective for bleaching therapy
have been suggested to explain the colour changes of than 35% hydrogen peroxide, and stained resin
restorative materials [28]. Water and molecular oxygen composites for enamel are more prone to bleaching.
are also released during the reaction [29]. Such release Besides that, the exposure time of resin composites to
may accelerate the hydrolytic degradation, and lead to bleaching agent plays an even more important role to
colour changes of resin composites. In addition, factors the material properties, since an extended exposure is
related to composites can influence colour, including more deleterious than higher concentration [6]. This can
wear, matrix structure, volume and type of filler, and be attributed to the colour results of the present study.
weakening of matrix-filler bonding [22,25,30]. Thus, a Translucency is related to light transmission, absorption,
composite with higher resin matrix content is expected scattering and reflection [22]. This property is influenced
to be more prone to degradation and colour changes by the difference between the refractive index of the
after bleaching treatment [31]. Although they presented resin matrix and filler particles, filler size, distribution,
164 Stoma Edu J. 2018;5(3): 161-167 http://www.stomaeduj.com
EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL
PROPERTIES OF AGED RESIN COMPOSITES
concentration, pigments and defects like voids [30,32]. materials [14]. In this study, different results would
Original Article
The increase of particles weight percent in resin possibly be detected with increased bleaching time.
composite (ranging from 10 to 70 %) reduced the It is important to emphasize that the microhardness
translucency of the material. Additionally, the increase of the two tested resin composites was different. The
in particle size is also reported to result in increased higher microhardness values of the Filtek Z350 XT are
translucency when comparing 0.77 µm with 0.50 m expected due to the presence of nanoclusters combined
fillers [32]. In the present study, an increased TP for with nanoparticles, which reduce the interstitial space,
Filtek Z350 XT was observed. It was reported that aging improving the physical properties [42]. From these
can change the translucency of the composites due to results, it was found that microhardness results were
changes in scattering and absorption properties [33]. only material dependent.
Previous studies reported that water from the bleaching Notwithstanding the low amount of studies and
agent is released during the bleaching procedures methodological variability, it has to be highlighted
[29,34] and it is able to penetrate within the polymer that aging and bleaching procedures produce relevant
chains and stay between the layers [27,35]. This process changes in the properties of the resin composite, which
can induce hydrolytic degradation of the material are material dependent. Although these changes might
[29,34,36], leading to filler–matrix interface debonding not be clinically observed, bleaching agents can lead to
and changes in optical properties due to an altered microcracks in the resin composite’s surface. This might
pattern of light diffusion [32,33,36]. One might question influence the clinical acceptability of resin composite
this statement regarding the presence of water in restorations concerning the longevity, and further
the oral environment during the whole restoration necessity of repair or replacement. Therefore, this study
service. The authors believe that the bleaching therapy provides interesting information and support further
exacerbates the potential of water influence on resin investigations to complement the present obtained
composites. In addition, the hydrophilic characteristics results.
of the monomers present in resin composites may
have contributed to translucency changes [36]. The
presence of Bis-GMA and TEGDMA monomers, which 5. Conclusion
present great susceptibility to hydrolysis, may lead to a Considering the limitations, the results of this in vitro
water uptake and monomer elution and consequently study provide useful additional information on the
an alteration in the light refraction index of the polymer optical and mechanical properties of aged resins after
matrix [37]. Those considerations might contribute to bleaching procedures. It is concluded that colour
explain the translucency behavior detected. However, and microhardness were constant, before and after
this condition needs to be further investigated. bleaching procedures. The bleaching agents were able
One of the reasons for studying the surface gloss to increase translucency and reduce the gloss of aged
of materials relies on the fact they might influence resin composites. Microhybrid composite showed lower
colour matching/selection in clinical conditions [38]. values for all the parameters assessed when compared
It has been reported that the gloss is altered after to the nanohybrid composite.
bleaching procedures [7,9]. Once the material already
presents a state of degradation, bleaching may worsen
this condition. In theory, the deterioration or wear Author Contributions
of materials can produce changes in surface gloss, IFM: Study design, laboratory testing, discussion of
resulting in esthetic changes [23,39]. Light reflection results, manuscript writing, and final manuscript
is related to filler size [40]. Small filler sizes are reported approval; AMC: Study design, laboratory testing,
to present greater surface gloss than large fillers under discussion of results and manuscript writing, and final
the same polishing procedures, leading to greater manuscript approval; DCD: Study design, laboratory
specular reflection [41]. In the present study, the testing, discussion of results, and final manuscript
bleaching decreased gloss for all tested materials, and approval; MCV: Study design, and discussion of results,
no differences were detected between nanohybrid and and final manuscript approval; RMM: Study design, and
microhybrid aged composites. Possibly, the superficial discussion of results, and final manuscript approval; EB:
layer was degraded due to the erosion of the resin matrix Study design, statistical analysis, interpretations of data,
[7], a fact that might be the reason for the present results. and manuscript writing, and final manuscript approval.
Thus, the fillers were exposed, altering the surface
topography, and therefore less gloss was detected.
Comparing the present data on aged resin composites Disclosure
to non-aged resin composite studies [7,8], the bleaching The authors do not have any financial interest in the
process resulted in similar patterns of surface gloss companies whose materials are included in this article.
decrease, suggesting bleaching may behave similarly
to aged and non-aged resin composite regarding such
property. Acknowledgements
It was observed that the application of the bleaching This study has been partially financed by the
agent was not able to change the microhardness of the Coordenação de Aperfeiçoamento de Pessoal de Nível
tested composites, confirming our expectations. The Superior - Brasil (CAPES) - Finance code 001.
effect of the bleaching agent on microhardness seems
to be related to the oxidation process, as previously
described [14]. The oxidative cleavage of polymer chains References
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166 Stoma Edu J. 2018;5(3):161-167 http://www.stomaeduj.com
EFFECT OF WHITENING ON THE OPTICAL AND MECHANICAL
PROPERTIES OF AGED RESIN COMPOSITES
Original Article
Ingrid Fernandes MATHIAS-SANTAMARIA
DDS, MS, PhD Student
Department of Restorative Dentistry
Institute of Science and Technology, São Paulo State University
São José dos Campos, Brazil
CV
Ingrid Fernandes Mathias-Santamaria, DDS, MS, PhD Student, got her degrees at the Institute of Science and Technology of São
José dos Campos, São Paulo State University - UNESP, Brazil. She has experience with laboratory and clinical research applying
dental materials, studying the behavior of direct resin composites.
Questions
1. Which method was used to assess colour and gloss?
qa. Spectrophotometer and Glossmeter, respectively;
qb. Glossmeter and Spectrophotometer, respectively;
qc. Spectrophotometer only;
qd. None of above.
2. Which was the result of the study?
qa. All the parameters were influenced by the bleaching therapy;
qb. None of the parameters were influenced by the bleaching therapy;
qc. Gloss decreased, and colour and microhardness were not influenced by the bleaching therapy;
qd. None of the optical parameters changed after bleaching therapy.
3. Which was the bleaching therapy used?
qa. 35% hydrogen peroxide for 20 minutes per application, three sessions;
qb. 35% carbamide peroxide for 15 minutes per application, three sessions;
qc. 35% carbamide peroxide for 15 minutes per session, three sessions;
qd. 35% hydrogen peroxide for 60 minutes per session, three sessions.
4. Regarding the artificial accelerated aging used, choose the correct alternative:
qa. Resin composites were not aged in this study;
qb. Aging was performed for 300 h using a UV-light chamber, simulating one year of clinical service;
qc. Aging was performed for 300 h using a UV-light chamber, simulating one year and a half of clinical
service;
qd. Aging was performed for 300 aging cycles using a UV-light chamber, simulating one year of clinical service.
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Stomatology Edu Journal 167