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dental bleaching
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Tooth sensitivity and efficacy of in-office bleaching inrestored teeth
Elize Bonafe, Camila Lais Bacovis, Simone Iensen, Alessandro D. Loguercio, Alessandra Reis,Stella Kossatz *
School of Dentistry, State University of Ponta Grossa, Ponta Grossa, Parana, Brazil
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 9
a r t i c l e i n f o
Article history:
Received 21 August 2012
Received in revised form
10 January 2013
Accepted 18 January 2013
Keywords:
Tooth bleaching
Hydrogen peroxide
Tooth sensitivity
Dental aesthetic
a b s t r a c t
Objectives: The aim of this clinical trial was to evaluate efficacy (BE) and tooth sensitivity (TS)
of in-office bleaching with a 35% hydrogen peroxide (HP) in patients with aesthetic restora-
tions.
Methods: Hydrogen peroxide 35% was applied in two sessions, of three 15 min applications,
in 15 patients with upper anterior sound teeth (S) and 15 with aesthetic restorations (R). The
colour was recorded at baseline, one week and 6 months after treatment completion.
Patients recorded TS on a 04 scale. The BE was evaluated by two-way ANOVA and Tukeys
tests (a = 0.05). The percentage of patients with TS was evaluated by Fishers exact test and
TS intensity of treatments was compared with MannWhitney U-test (a = 0.05).
Results: All participants experienced TS at least once during treatment. Higher TS intensity
was observed in R (1.5 [1/1.75]) compared to S (0.5 [0/1.25]) during the bleaching ( p < 0.05). S
and R demonstrated similar tooth colour enhancement compared to baseline ( p < 0.05) and
both presented colour stability after 6 months of evaluation ( p > 0.05).
Conclusions: The in-office bleaching with 35% HP was effective in patients with aesthetic
restorations, however, a higher intensity of TS was observed during the bleaching protocol.
Clinical relevance: In-office dental bleaching can be performed in patients with adhesive
restorations promoting satisfactory results; however, it can promote higher intensity of
sensitivity compared to patients with sound teeth.
# 2013 Elsevier Ltd. All rights reserved.
Available online at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/jden1. Introduction
Nowadays, vital tooth bleaching is one of the most requested
cosmetic dental procedures asked by patients who want an
aesthetically more pleasing smile.1 This procedure is per-
formed by the application of carbamide or hydrogen peroxide
gels on tooth surfaces and can be done at home, with or
without the supervision of the dentist, or in-office by the
clinician.2,3
At-home bleaching is the most widely taught bleaching
technique in the USA4 and the most accepted technique* Corresponding author at: Programa de Pos-Graduacao Stricto Sensu daM, Av. General Carlos Cavalcanti, 4748 Uvaranas, CEP 84030-900, Pon
E-mail address: stellakp@gmail.com (S. Kossatz).
0300-5712/$ see front matter # 2013 Elsevier Ltd. All rights reservedhttp://dx.doi.org/10.1016/j.jdent.2013.01.007among patients.5 This is probably due to the high number of
successful records of satisfactory results reported with this
technique.610 However, there are still some people that do not
want to use bleaching trays or who want faster results. In
addition, some patients may not adapt well to the daily use of a
bleaching tray, which increases the treatment time and costs.
In these circumstances, in-office bleaching seems to be the
most suitable treatment.
Although clinical studies have shown that in-office
bleaching can achieve as satisfactory degree of whitening as
at-home bleaching, as long as the materials are used for the UEPG, Departamento de Odontologia, Campus de Uvaranas, Blocota Grossa, PR, Brazil.
.
http://dx.doi.org/10.1016/j.jdent.2013.01.007mailto:stellakp@gmail.comhttp://www.sciencedirect.com/science/journal/03005712http://dx.doi.org/10.1016/j.jdent.2013.01.007
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 9364appropriate period of time5,1116 most of the data we have
about tooth bleaching has been gathered from participants
with sound teeth, because the clinical protocol of these studies
did not usually include participants with restored teeth.12,1722
Few studies have included participants with adhesive restora-
tions on anterior maxillary teeth in clinical trials.14,23,24
However, in a clinical practice, vital tooth bleaching is often
performed on teeth with adhesive restorations on a daily
basis, and therefore, more knowledge about the bleaching
efficacy (BE) and tooth sensitivity (TS) of in-office bleaching in
relation to this common condition is required.
Laboratory studies have shown that higher amounts of
hydrogen or carbamide peroxide can penetrate the pulp
chamber of teeth with adhesive restorations, compared to
sound teeth.2527 Considering that TS has been reported as a
common side effect, affecting more than 60% of the patients
that undergo this cosmetic treatment,17,2123 this situation
may be even worse in patients with restored teeth. To the
extent of the authors knowledge, no previous study has
compared the BE, and most importantly, the TS experiences of
patients with and without adhesive restorations. Therefore,
the aim of this clinical trial was to compare the degree of
whitening and the TS intensity of patients with and without
adhesive restorations.
2. Materials and methods
This clinical investigation was approved under protocol
number 12/2011 by the scientific review committee and by
the committee for the protection of human beings of the local
university (UEPG). Based on pre-established criteria, 30
volunteers were selected for this study. Two weeks before
the bleaching procedures, all the volunteers received dental
screening and prophylaxis with pumice and water in a rubber
cup. They also signed an informed consent form.
2.1. Inclusion and exclusion criteria
Participants included in this clinical trial were between 18 and
35 years old. A total of 64 participants were examined in a
dental chair to check if they meet the inclusion and exclusion
criteria (Fig. 1). The participants were required to have central
incisors of shade A2 or darker, as judged by comparison with a
value-oriented shade guide (Vita Lumin, Vita Zahnfabrik, Bad
Sackingen, Germany). The following were excluded from the
study, since they would not be suitable for a cosmetic study
such as bleaching: people who had undergone tooth-whiten-
ing procedures, smokers, pregnant/lactating women, people
with severe internal tooth discoloration or endodontic
treatment in anterior teeth, people taking any kind of
medicine, with bruxism habits, recession, dentine exposure,
or active carious lesions. Participants who reported to have
spontaneous TS or sensitivity to hold and cold drinks were
also excluded from the study.
2.2. Sample size calculation
With a 90% confidence interval, the number of subjects
required to detect an absolute risk of TS was around 80% forboth groups12,21 with a total width of the confidence interval of
0.35, being 14 participants per group.28 A total of 15
participants were selected for each group in order to
compensate for likely dropouts.
2.3. Study groups
Participants who met the inclusion criteria were examined in a
dental chair to see whether they had anterior teeth with
adhesive restorations. Those participants who did not have any
restoration in the facial surface of the eight upper maxillary
teeth were assigned to the control group, while participants with
at least one restoration in the central incisor and a maximum of
four in other anterior teeth were assigned to the restored group.
These restorations were not to involve more than 25% of the
facial surface of the anterior teeth14 and were to be judged as
satisfactory (Alfa and Bravo for marginal adaptation and
discoloration, and lack of caries lesions adjacent to the
restorations) with no need of repair according to FDI criteria.29
2.4. Study intervention
The gingival tissue of the teeth to be bleached was isolated
using a light-cured resin dam (Top Dam, FGM, Joinville, SC,
Brazil). Hydrogen peroxide (HP) gel, 35% (Whiteness HP Maxx,
FGM) was used in three 15-min applications for both groups
according to the manufacturers directions. The in-office
bleaching agent was refreshed every 15 min during the 45-
min application period. Two sessions with a one week interval
were performed.
2.5. Tooth sensitivity evaluation
The participants recorded their perception of TS during the
bleaching on a daily basis up to 7 days following each
bleaching session. The patients were asked to report any
tingling or shooting pain without provoking stimuli. A five-
point verbal rating scale [0 = none, 1 = mild, 2 = moderate,
3 = considerable and 4 = severe]6,22 was employed in this
study. The median score value obtained in both bleaching
sessions for each time assessment was considered for
statistical purposes. The values were arranged into two
categories: percentage of patients that reported TS at least
once during treatment (absolute risk of TS), and overall TS
intensity during and up to 24 h after each bleaching session.
The participants were also instructed to identify the painful
teeth every time they experienced TS.
2.6. Shade evaluation
Shade evaluation was recorded using two methods: a
subjective evaluation using a shade guide (Vita Lumin, Vita
Zahnfabrik, Bad Sackingen, Germany) and an objective
evaluation using the spectrophotometer (Easyshade, Vident,
Brea, CA, USA). Colour was evaluated with teeth in a complete
hydrated condition at baseline, 1 week and 6 months after the
bleaching protocol. Colour was not evaluated soon after each
bleaching session in order to avoid the influence of tooth
dehydration and demineralization that occurs simultaneously
with the whitening effect on the final colour outcome.
Exclud ed (n= 34)Central i ncisors l igh ter tha n A2
(n=17)
Tooth sensiti vity to cold dr inks(n=10)
Maxillar a nter ior tee th w ith endodontic treat ment (n =5)
Other reasons (n= 2)
Assess ed for eli gibility (n= 64)
Enrollment
Randomized (n=30)
Allocat ed t o gr oup S (n=15)Received a llocate d i nte rventi on (n= 15)
Allocat ed to grou p R (n =15)Received a llocate d i nte rventi on ( n=1 5)
Lost to follow up ( n=0)Discont inued i nterven tion (n= 0)
Lost t o fo llow up ( n=0)Discont inued i nterven tion (n= 0)
Analysed (n= 15) Analysed (n= 15)
Allocation
Follow up
Analysis
.
.
.
.
Fig. 1 Flow diagram of the clinical trial.
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 9 365For the subjective examination, the shade guides 16 tabs
were arranged from the highest (B1) to the lowest (C4) value,
making the colour A2 number 5, for example, in order to allow
calculation of the variation of the shade guide units (DSGU).
Although this scale is not linear in the truest sense, we treated
the changes as representing a continuous and approximately
linear ranking for the purpose of analysis. The measurement
area of interest for shade matching was the middle third of the
facial surface of the anterior central incisor. For calibration
purposes, five patients whom we did not include in the sample
because they were used in the pilot study participated in the
training phase of this study. The two examiners, scheduled
the patients for bleaching after evaluating their teeth against
the shade guide. The two examiners were required to have an
agreement of at least 85 (weighted Kappa statistic) before
beginning the study evaluation. If disagreements arose during
evaluation they were encouraged to reach a consensus.
For the objective evaluation we followed the method
employed by Marson et al.17 A preliminary impression of
the maxillary arch was made using dense silicone Adsil
(Vigodent S/A Indu stria e Comercio, Rio de Janeiro, RJ, Brazil),
that served as a standard colour measurement guide for the
spectrophotometer. A window was created on the labial
surface of the silicone guide for the central incisor to be
evaluated. It window was made using a metallic device with
well-formed borders, 3 mm in radius. The measurement wascarried out on all 30 patients using Vita Easyshade (Easyshade,
Vident, Brea, CA, USA) at the same time assessment used in
the subjective evaluation. In the restored teeth, care was taken
to perform the measurements only on the tooth surface. The
shade was determined using the parameters of the Easyshade
device where it indicated the following values: L*, a* and b*, in
which L* represents the value from 0 (black) to 100 (white) and
a* and b* represent the shade, where a* is the measurement
along the red-green axis and b* is the measurement along the
yellow-blue axis. The colour comparison before and after
treatment is given by the differences between the two colours
(DE), which is calculated using the formula30:
DE DL2 Da2 Db21=2
:
2.7. Statistical analysis
The analysis followed the intention-to-treat protocol and
involved all participants who were randomly assigned.31 The
statistician was blinded to the study groups.
The primary outcome, absolute risk of TS, was compared by
using the Fishers exact test. Statistical analyses of TS
intensity, comparing the two groups in each assessment
points, were performed using the MannWhitney U-test. As
two bleaching sessions were performed, the median score at
each assessment point was considered for statistical analysis.
Table 1 Median and interquartiles ranges of toothsensitivity reported by patients at different assessmenttimes for the two treatment groups.a
Sound Restored
During bleaching 0.5 (0/1.25) aA 1.5 (1/1.75) aB
Up to 24 h
post-bleaching
2 (0.75/2.25) bA 2 (0/2) aA
a At each treatment, the two periods were compared with
Wilcoxon Signed Rank (a = 0.05) and differences are represented
by different lowercase letters. For each period, the treatments were
compared with MannWhitney U-test and the differences are
represented by different uppercase letters.
Table 2 Means and standard deviations of shade guideunits (Vita Classical shade guide) at different assessmentpoints for the two treatment groups.a
Sound Restored
Baseline 5.7 1.5 aA 5.9 1.1 aA1 week after bleaching 1.3 0.5 aB 1.8 0.7 aB6 months after bleaching 1.5 0.5 aB 1.9 0.6 aBa The same lowercase letters indicate statistically similar means
within rows. The same uppercase letters indicate statistically
similar means within columns (Tukeys test, a = 0.05).
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 9366Comparisons between times within each group were per-
formed using the Wilcoxon Signed Rank test. The proportion
of patients from both groups that reported TS at least once in
the central incisors, lateral incisors, canines and premolars
were calculated and compared by chi-square test. The
proportion of painful restored teeth was compared with the
proportion of sound restored teeth in the restored group by
chi-square test.
For the subjective evaluation of colour, the mean and
standard deviations of shade guide units at baseline, one week
after and 6 months after bleaching were compared with two-
way repeated measures ANOVA (Groups vs. Assessment time)
and Tukeys test. The data from DSGU and DE of both groups
were submitted to two-way repeated measures ANOVA. A post
hoc analysis (Tukeys test) was used to make pairwise
comparisons. In all statistical tests, the significance level
was set at a = 0.05.
3. Results
A total of 64 participants with age ranging from 18 to 35 years
old were evaluated to select 30 participants that met the
inclusion criteria. Reasons for exclusion of participants were
the following: shade lighter than A2 (n = 17), presence of
spontaneous TS (n = 10), anterior incisors with endodontic
treatment (n = 5) and other reasons (n = 2). The mean age
(years) of the participants in this study was similar between
the groups (control: 24.4 3.7 and restored: 25.3 5.4). Sixtypercent of the participants were females, 10 in the control
group and 8 in the restored group.
All participants in this study reported TS at least once
during treatment and thus the absolute risk of TS was 100%
(95% CI: 80100%) for both groups (Fishers exact test, p = 1.0).Table 3 Means and standard deviations (SD) of DSGU and DEgroups.a
DSGU
Sound R
Baseline vs. 1 week 4.3 1.3 a 4Baseline vs. 6 months 4.2 1.4 a 4aMeans indicated by the same lowercase letters indicate statistically sim
letters indicate statistically similar means for DE (Tukeys test, a = 0.05).In regard to the intensity of TS (Table 1), participants from the
restored group reported a higher intensity during bleaching
than those from the sound group (MannWhitney U-test,
p = 0.0362). Most participants of both groups reported tooth
pain up to 6 h post-bleaching (83.3%, 95% CI: 66.492.7%), with
some experiencing pain up to 24 h (16.7%, 95% CI: 7.333.6%)
and no statistical difference was observed between groups at
this assessment time (Wilcoxon Signed Rank test, p = 0.3507).
The two-way ANOVA for the shade guide units (SGU) data
showed that only the main factor assessment time was
statistically significant ( p < 0.001). A higher degree of bleach-
ing was obtained after two weeks of treatment and this result
was stable after 6 months for both groups (Table 2). The DSGU
and DE values showed a similar trend. Neither the main factors
nor the cross-product interaction were statistically significant
(ANOVA test, p > 0.05). This means that a degree of bleaching
of approximately 4 SGUs was detected for both groups and this
was stable after 6 months (Table 3).
For all patients included in this clinical trial, the teeth with
most complaints of TS were the lateral incisors (76.7%) which
were statistically different from the canines and premolars
(chi-square test, p < 0.05) but similar to the central incisors
(Table 4). In relation to the participants of the restored group,
50% (95% CI: 32.068.0%) of their restored teeth and 31.3% (95%
CI: 21.243.4%) of their sound anterior teeth were reported to
be painful, respectively. These percentages were not statisti-
cally different (chi-square test, p = 0.16) to the participants in
the control group, 34.4% (95% CI: 25.444.7%).
4. Discussion
Dental bleaching often promotes TS as an adverse effect. It
probably occurs in response to the permeation of HP through
enamel and dentin32 promoting the release of inflammatory
mediators in the pulp33 and damage to the pulp cells.38 In at different assessment points for the two treatment
DE
estored Sound Restored
.1 0.9 a 4.2 0.9 a 4.7 1.1 a
.0 0.9 a 4.0 0.7 a 4.1 0.7a
ilar means for DSGU and means indicated by the same uppercase
Table 4 Number of patients who reported tooth sensitivity at least once in the different tooth types.
Tooth type Number of patients of each groupa Overall proportion (95% CI)**
Sound (a) Restored (b) Overall
Central incisors 9 8 17 53.3 (36.169.8) A
Lateral incisors 11 12 23 76.7 (59.088.2) A
Canines 5 4 9 30.0 (16.747.9) B
Premolars 0 0 0 0 (00.11) C
a Proportions indicated by the different lower case letters are statistically different (sound or restored; chi-square test, a = 0.05).** Proportions indicated by the different upper case letters are statistically different (tooth types; chi-square test, a = 0.05)
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 9 367accordance with previous studies,17,2123 a high absolute risk
of TS was observed in this study, regardless of the treatment
group.
However, although the prevalence of TS among patients in
the control and restored groups was similar, a higher TS
intensity was observed in patients with adhesive restorations,
especially during the application of the in-office bleaching gel.
This means that all patients, regardless the presence or absence
of restorations, can experience TS, but its intensity is likely to be
higher in patients with restored teeth during the gel application.
TS results from the expression of inflammatory mediators
such as substance-P33 and prostaglandins, which have a
recognized role in triggering nociceptive impulses for the
perception of pain.34 The amount of HP that reaches the pulp
was shown to be 25 times higher in restored rather than in
sound teeth.25,26 This is likely to be due to the fact that adhesive
interfaces in the restored teeth may work as fast pathways of HP
to pulp and that pulp cells may not be capable of producing
enough peroxidades, catalases35 and oxygenases36 to protect
the pulp from the immediate damage caused by HP. This might
explain why during the application of the in-office bleaching
gel, participants from the restored group showed TS with a high
intensity than those from the control group.
However, as pointed out by Gokay et al.26 it is worth
mentioning that several factors may affect the ability of HP to
permeate the dental structures of restored teeth. The depth
and size of the restorations, as well as the type of adhesive and
restorative material, may also play a significant role. In the
present study, only participants with composite resin restora-
tions were evaluated. We were not aware of the brand of
composite and adhesive system used. The impact of these
factors on the amount of HP that reaches the pulp and the TS
experienced by patients is not known and should be the focus
of future studies.
In present study, the tooth that was reported to give most
complaints of TS was the upper lateral incisor. In a review of
the literature, Haywood37 reported that bleaching-induced TS
usually affects the smaller teeth, such as the maxillary laterals
and the mandibular incisors. These reports are in agreement
with a recent histological study of pulp after in-office
bleaching.38 In the latter study the authors observed notable
damage to the pulp tissue of lower incisors but not in
premolars. The thinner enamel and dentine layers of incisors
compared to premolars may allow the fast passage of HP to the
pulp, allowing less time for the production and release of
protective enzymes against damage by HP.38
At the present time, there are several recommendations
for reducing post-bleaching sensitivity, such as theadministration of analgesics39 a decrease in concentration
and in application time of the bleaching gel22,37 and the
application of desensitizing agents before each bleaching
session.12 The most commonly used desensitizing agents
include potassium nitrate, which prevents the transmission of
nerve impulses.40 This could represent an alternative which
might minimize TS in patients with restorations; however,
this possibility must be clinically evaluated.
In regard to bleaching efficacy, the results of this present
study indicated that both groups demonstrated similar and
significant tooth colour enhancement as compared with
baseline. Studies that employed 35% HP and reported their
results in SGU have usually observed an overall colour change
of 58 SGUs after two bleaching sessions.5,12,21,22,24 In our
study, we found on average a variation of 4 SGUs which is in
agreement with a previous study.16 These differences may be
due to variations in the baseline colour shade of teeth included
in the trial. Studies that usually report a higher variation in
SGU include teeth with shade darker than C2. In the present
study and in other recent research16 the investigation of teeth
colour used a baseline of A2.
Visual colour determination by comparing teeth to a shade
guide has been the most often used method in dentistry. Some
authors41 concluded that the human eye is efficient in detecting
even small differences, while other authors have commented
that the human evaluation of tooth shade is not as accurate as
digital evaluation.42,43 The digital method has been evaluated as
being five times more likely to match the original shade colour
compared to the visual method.44 Taking that into consider-
ation, we opted to evaluate colour changes using a visual shade
guide and a spectrophotometer. In the present study, both
methods yielded similar results and were similar to the results
shown in the study by Meireles et al.8 The standardization of
lighting, the array used to support the spectrophotometer, and
most importantly, the moment at which the objective evalua-
tions were done (with teeth completely hydrated, avoiding bias
in colour measurement), are probably responsible for such
agreement between methods.
In regard to colour stability, 6 months after bleaching no
significant differences among the groups were detected and
there was also no significant colour rebound. These results are
similar to those reported by other authors,16,17,45 but differ
from the clinical study of Zekonis et al.13 and Matis et al.24 The
findings of the latter two studies are controversial, probably
due to differences in the total bleaching time, which was
lower. In-office bleaching seems to achieve satisfactory results
when more than one session is performed11 with no statistical
rebound of colour, at least in periods ranging from 6 months to
j o u r n a l o f d e n t i s t r y 4 1 ( 2 0 1 3 ) 3 6 3 3 6 93682 year.45,46 Future studies should be conducted in order to
evaluate the longevity of bleaching procedures after several
years.
5. Conclusions
Similar degrees of whitening could be observed in participants
with restored teeth. However, a higher intensity of tooth
sensitivity was reported by participants with restored teeth
during the bleaching protocol.
Acknowledgment
The authors would like to thank FGM Dental Products for the
donation of the products used in this investigation.
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Tooth sensitivity and efficacy of in-office bleaching in restored teeth1 Introduction2 Materials and methods2.1 Inclusion and exclusion criteria2.2 Sample size calculation2.3 Study groups2.4 Study intervention2.5 Tooth sensitivity evaluation2.6 Shade evaluation2.7 Statistical analysis
3 Results4 Discussion5 ConclusionsAcknowledgmentReferences
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