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