In-office bleaching with a two- and seven-day intervals between clinical sessions.

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Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/jden 1 2 3

In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity

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Eloisa Andrade de Paula a, Jéssica Andressa Nava a, Cheilla Rosso a, Cristina Monteiro Benazzi a, Karen Tamura Fernandes a, Stella Kossatz b, Alessandro Dourado Loguercio b, Alessandra Reis b,* a b

School of Dentistry, Paranaense University, Umuarama, Paraná, Brazil School of Dentistry, State University of Ponta Grossa, Ponta Grossa, Paraná, Brazil

article info

abstract

Article history:

Objectives: In-office bleaching is usually performed in 2–3 sessions with one-week interval.

Received 24 May 2014

The impact of shorter interval times on tooth sensitivity has not been evaluated. This study

Received in revised form

aimed to compare the absolute risk of tooth sensitivity (TS) and colour change after in-office

27 August 2014

bleaching with a two- and seven-day intervals between sessions.

Accepted 12 September 2014

Methods: We selected for this randomized, single-blind study, 40 patients with colour C2 or

Available online xxx

darker. We performed two bleaching sessions with a 35% hydrogen peroxide gel with either a 1-week or 2-day interval. We recorded the TS up to 48 h with a VAS scale and the colour at

Keywords:

baseline and 30 days after bleaching with a value-oriented shade guide and a spectropho-

Dentine sensitivity

tometer. The risk and intensity of TS were compared with the Fisher’s exact test and two-

Randomized controlled trial

way repeated measures ANOVA. Colour change (DSGU and DE) were evaluated by Student’s

Tooth bleaching

t-test (alpha = 5%).

Results: Approximately 60% of the participants reported TS (65% and 55% for the 7 and 2-day groups). A significant whitening of approximately 6 shade guide units was detected for both groups. No difference was detected between groups.

Conclusions: The reduction of the interval between bleaching sessions from seven to two days reduced the treatment time without increasing the bleaching-induced TS (clinicaltrials.gov identifier: NCT1959789).

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Clinical significance: In-office bleaching with a 2-day interval did not increase the risk and intensity of bleaching-induced tooth sensitivity. # 2014 Published by Elsevier Ltd.

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1.

Introduction

Bleaching is the most conservative treatment for discoloured teeth. Since the introduction of carbamide peroxide for

at-home bleaching,1 new bleaching techniques have been developed. Although at-home bleaching achieves a high success rate and it is the most widely used technique by clinicians for bleaching vital teeth,2,3 some patients do not want to use a bleaching tray or do not want to wait two to three

* Corresponding author at: Universidade Estadual de Ponta Grossa, Faculdade de Odontologia, Rua Carlos Cavalcanti, 4748, CEP 84030-900, Q2 Brazil. Tel.: +55 42 30277898.

E-mail addresses: reis_ale@hotmail.com, alereis@uepg.br (A. Reis). http://dx.doi.org/10.1016/j.jdent.2014.09.009 0300-5712/# 2014 Published by Elsevier Ltd.

Please cite this article in press as: de Paula EA, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. Journal of Dentistry (2014), http://dx.doi.org/10.1016/j.jdent.2014.09.009

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weeks to see the results of the treatment. These patients typically prefer a method that produces more immediate results. In such cases, in-office bleaching is an alternative bleaching option since the dental professional can perform the in-office bleaching at the same day the patient visits the dental office. This method of tooth whitening has been around for many years and remains popular because some degree of whitening can be seen after one clinical appointment.

However, a single in-office bleaching session4–7 seems not to be enough to whiten teeth effectively and reach patient’s satisfaction.8,9 Usually two or three visits should be performed to achieve effective whitening with colour stability.9–12 This has the disadvantage of prolonging the time needed to reach satisfactory results, since these visits are usually arranged with at least one week interval.13–19 Although this one-week interval is not an evidence-based decision, it may be due to the clinician’s concern of producing severe pulp damage and increase the TS levels. Bleachinginduced tooth sensitivity (TS) affects more than 70% of the patients.14,19–21 This TS usually starts during bleaching and ceases 24–48 h after the procedure.16,20–22 From the professional and patient standpoint, in-office bleaching with shorter intervals between sessions could allow faster results.

To the best of the author’s knowledge, there is no clinical study that investigated the effect of the interval time between in-office bleaching sessions on the risk and intensity of bleaching-induced TS. Therefore, this study attempted to investigate the risk and intensity of bleaching-induced TS after in-office bleaching with a two or seven-day intervals between sessions. The null hypotheses of the present study were (1) the 7-day and 2-day groups will yield the same bleaching effectiveness and (2) both groups will have the similar risks of bleaching-induced TS.

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This clinical investigation was approved (protocol number 22564/2011) by the Ethics Committee for the protection of human subjects of the University of Umuarama, Paraná, Brazil. The experimental study was described according to the Consolidated Standards of Reporting Trials statement.23 Two weeks before the bleaching procedures, selected volunteers from the city of Umuarama, (Paraná, Brazil) received a dental screening and a dental prophylaxis with pumice and water in a rubber cup and signed an informed consent form.

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This was a randomized, single-blind (evaluators), parallel and equivalence trial with an equal allocation rate between groups. The study was conducted at the School of Dentistry, Paranaense University in Umuarama, Paraná from August 2011 to August 2012.

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2.1.1.

Materials and methods

in the university and in stores at Umuarama city. A total of 116 participants were examined in a dental chair to check if they met the inclusion and exclusion criteria (Fig. 1). The participants should have at least six maxillary and mandibular anterior teeth caries-free and without restorations on the labial surfaces. The central incisors should be C2 or darker according to a value-oriented shade guide (Vita Lumin, Vita Zahnfabrik, Bad Säckingen, Germany). Participants with preexisting anterior restorations, pregnant/lactating, with severe internal tooth discoloration (tetracycline stains, fluorosis, pulpless teeth), taking any drug with anti-inflammatory and antioxidant action, bruxism habits or any other pathology that could cause TS (such as recession, dentine exposure) were excluded from this study to minimize confounding experimental variables.

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2.2.

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Sample size calculation

We selected the absolute risk of TS as the primary study outcome. Considering the absolute risk of TS to be approximately 90%,19 40 participants were required to be 90% (study power) sure that the limits of a two-sided 90% confidence interval will exclude a difference between the standard and experimental group of more than 30% (equivalence limit).

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2.3.

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Study intervention

We randomly divided the participants in the 2-day and 7-day groups. A third operator, not involved in the research protocol, conducted the randomization process, which recorded the details of the allocated groups on cards placed in sequentially numbered, opaque and sealed envelopes. Once the participant was eligible for the procedure and completed all baseline assessments, the operator could open the envelope. Neither the participant nor the operator knew the group allocation before this stage.

We isolated the gingival tissue of the teeth using a lightcured resin dam (Top Dam, FGM, Joinville, SC, Brazil). The 35% hydrogen peroxide gel (Whiteness HP Blue, FGM, Joinville, Brazil, Table 1) was applied in a single 40-min application according to the manufacturer’s directions in all upper incisors, canines and premolars. After 2 days (2-day group) and 7 days (7-day group), this procedure was repeated using the same protocol. We instructed all participants to brush their teeth at least three times daily using fluoridated toothpaste (Sorriso Fresh, Colgate-Palmolive, São Paulo, SP, Brazil). The lower arch was also bleached in another clinical session, but data was not collected from this arch.

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2.4.

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Study design

Inclusion and exclusion criteria

Participants included in this clinical trial were at least 18 years old and had good general and oral health. Participants were recruited by means of visual communication through posters

Shade evaluation

We recorded the shade evaluation before and 30 days after the end of the bleaching treatment using a subjective (valueoriented shade guide Vita Lumin, Vita Zahnfabrik, Bad Säckingen, Germany) and an objective method (Easyshade spectrophotometer, Vident, Brea, CA, USA). Colour evaluation was done in a room under artificial lightning conditions without interference from outside light.

For the subjective examination, we arranged the shade guide’s 16 tabs from highest (B1) to lowest (C4) value, making

Please cite this article in press as: de Paula EA, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. Journal of Dentistry (2014), http://dx.doi.org/10.1016/j.jdent.2014.09.009

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Fig. 1 – Flow diagram of the clinical trial including detailed information on the participants.

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the minimum qualifying shade C1 as number 6 (6th tab on the value-ordered arrangement). We treated the changes in the scale as representing a continuous and approximately linear ranking. We measured the colour in the middle third of the facial surface of one of the anterior central incisors (randomly selected) at baseline and 30 days after bleaching to calculate the variations in colour towards the lighter end of the scale (DSGU).

For the objective evaluation, we made a preliminary impression of the maxillary arch using high-putty silicone Adsil (Vigodent S/A Ind. Com., Rio de Janeiro, RJ, Brazil) to serve as a standard guide for the spectrophotometer tip. We created a window on the labial surface of the moulded silicone guide in the middle third of the central incisor, using a metallic device with well-formed borders, 3 mm in radius .15 One calibrated operator measured the colour in all participants using the Vita Easyshade spectrophotomer (Easyshade, Vident, Brea, CA, USA) before and 30 days after the bleaching

Table 1 – Baseline characteristics of the participants included in this clinical trial.

Characteristics Age (mean SD, yrs) Male (%) Baseline colour (mean SD, SGU) yrs – years; SGU – shade guide units.

7 days

2 days

25.6 5.4 50 10.9 1.9

23.9 6.6 35 10.1 2.1

therapy. The L*, a* and b* parameters were recorded; 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. We calculated the variation in colour between the two assessment periods (D E) using the formula: D E = [(DL*)2 + (Da*)2 + (Db*)2]1/2.15,17 The operator was only considered calibrated when he could get a weighted Kappa of 85% in two consecutive readings of the same teeth in 10 different people.

The patients recorded their perception of TS during the first and second bleaching sessions using the visual analogue scale VAS.24,25 This scale employs a 10-cm horizontal line with words ‘‘no pain’’ at one end and ‘‘worst pain’’ at the opposite end. We asked subjects to record whether they experienced TS during the treatment up to 1 h after the bleaching, from 1 h to 24 h and from 24 h to 48 h after bleaching. In the 30-day recall, patients were also asked if they experienced pain during this 30-day period. As two bleaching sessions were performed, the VAS score obtained in both bleaching sessions was considered for statistical purposes. These values were computed for the maxillary arch.

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Statistical analysis

The analysis followed the intention-to-treat protocol and involved all participants who were randomly assigned.23 The statistician was blinded to the study groups. The absolute risks

Please cite this article in press as: de Paula EA, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. Journal of Dentistry (2014), http://dx.doi.org/10.1016/j.jdent.2014.09.009

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of TS (overall percentage of patients that reported TS at least once during treatment at any assessment point) were compared with the Fisher’s exact test. TS intensity was evaluated by two-way repeated measures ANOVA (Group vs.

Assessment point) and Tukey’s test. Colour change (DSGU and DE) from baseline to 30 days after bleaching were evaluated by Student’s t-test. In all statistical tests, the significance level was set at alpha of 5%.

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Results

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The characteristics of the participants included in this clinical trial are described in Table 1. Fig. 1 depicts the participant flow diagram in the different phases of the study.

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The risks of TS in the 7-day and 2-day groups were 65 and 55% and no significant difference was observed between groups (Table 2; p = 0.74). The TS intensity of both bleaching sessions was statistically similar (p = 0.75; data not shown) and thus, we reported in Table 3 the overall TS intensity at different assessment points. No significant difference was observed between 2-day and 7-day groups in any of the study periods (p = 0.75). Most of the TS complaints occurred within the first 24 h (p < 0.01) and only one participant of each group experienced pain after 24 h. None of the patients reported to feel TS for the next 30 days after the procedure.

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A whitening of approximately 6 shade guide units in the shade guide units and a variation of approximately 9 in the DE were

Colour change

Treatment (days)

7 2

Tooth sensitivity (number of participants) Yes

No

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7 9

Absolute risk (95% CI)

65 (43–82) A 55 (34–74) A

Fisher exact-test. Identical letters indicate similar proportions.

Table 3 – Tooth sensitivity intensity (means W standard deviations) at the different assessment points for both study groups and the statistical comparison.a VAS

Up to 1 h 1–24 h 24–48 h a

DSGU DE a

7 days

2 days

p-Valuea

6.3 2.3 A 9.1 6.1 a

6.2 2.4 A 8.8 4.6 a

0.80 0.85

Student t-test. Means indicated by the same uppercase (DSGU) and lowercase (DE) letters indicate statistically similar means.

detected for the 7-day and 2-day groups, respectively (Table 4).

No statistically significant difference was observed between the study groups (p 0.8 for both methods). The variation in the L* (6.1 5.9 [7-day] and 5.3 4.8 [2-day]), a* ( 2.0 2.3 and 3.1 2.0) and b* ( 4.6 3.6 and 4.5 3.0) parameters were similar for the study groups (p > 0.05).

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Tooth sensitivity

Table 2 – Comparison of the number of patients who experienced tooth sensitivity at least once during the bleaching regimen in both groups along with absolute risks (*) and the statistical comparisona.

a

Table 4 – Colour change in shade guide units (SGU) and DE (means W standard deviations) between baseline vs.

30 days after bleaching for the two treatment groups.

7 days

2 days

2.5 2.3 A 1.6 2.6 A 0.2 1.0 B

2.2 2.9 A 1.3 1.9 A 0.1 0.5 B

Two-way ANOVA and Tukey’s test. Means identified with the same letters are statistically similar.

Discussion

In both study groups, a whitening of approximately 6 shade guide units were observed, which suggests effective whitening of the in-office bleaching protocol, as already demonstrated by other authors.3,15,17,19,26 Although some authors reported low effectiveness of in-office bleaching with significant colour rebound soon after bleaching,4–7 these studies considered the final colour outcome the one produced immediately after bleaching.

Teeth tend to appear whiter immediately after bleaching, due to the demineralization caused by the low pH of some bleaching products and the dehydration caused by teeth isolation.12 The contact of the teeth with saliva can reverse the demineralization27 and dehydration effects in a few days and only the whitening produced by the oxidization of the organic dental matrix will be sustained. This is the reason of why we recorded the final colour 30 days after bleaching. Therefore, the colour change reported in the present study indeed reflects the changes produced by the oxidation process caused by the 35% hydrogen peroxide gel. Apart from that, the application of a single in-office bleaching session4–7 is not enough to whiten teeth effectively and reach patient satisfaction.8,9 At least, two in-office bleaching sessions is required to produce effective and stable whitening in periods from 9 to 24 months.10,11 Although the aetiology of the bleaching-induced TS is yet not completely understood it seems to result from the direct activation of intradental nerve via chemosensitive channels to a variety of oxidizer compounds, including the hydrogen peroxide.28 However, the presence of an acute inflammatory reaction in dental pulps of human bleached teeth29 suggests that some released mediators of the inflammatory reaction such as bradykinin or substance P30 may be involved in the aetiology of the bleaching-induced TS. The interpretation that the consecutive application of hydrogen peroxide could be cytotoxic to the pulp came from in vitro studies on cultured pulp cells31 and on the two or three-day histological findings of human lower incisors29,32 and canines of dogs.33 Extensive inflammatory reaction and deposition of reactionary dentine were seen in the bleached teeth from the aforementioned studies after in-office bleaching. The histological condition of human pulps longer periods

Please cite this article in press as: de Paula EA, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. Journal of Dentistry (2014), http://dx.doi.org/10.1016/j.jdent.2014.09.009

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after bleaching was only assessed in premolars,34 where no changes were observed even in the immediate period.32 These differences may be related to the thickness of the dental structure of the bleached teeth.

The long-term histological study in dogs reported that the inflammatory reaction seen three-days after bleaching were still present in teeth extracted 15 days after bleaching. Only after 60 days, the haemorrhage, resorption and inflammatory infiltration were not detected, which demonstrates that the bleaching-induced inflammatory reaction is a slow but reversible process.33 In face of the above discussion we hypothesize that even if an inflammatory reaction occurs in human teeth after one bleaching session, the condition of the pulp will not be different two or seven days after the procedure. This may explain why the application of a second bleaching session two days after bleaching did not increase the risk and intensity of TS, which was similar to the tradicional 7-day interval. Besides that, none of the patients reported pain 30 days after the end of the protocol, which strengthens the hypothesis that the different time intervals was not capable to exacerbate the inflammatory reaction in the pulp. Future studies evaluating the histological pulp condition after bleaching with different time intervals should be conducted to strengthen the safety of this shorter interval protocol.

One important difference between the bleaching gel employed in this study and other in-office bleaching gels available on the market is that it contains 2% calcium gluconate and it is delivered in an alkaline pH. Most in-office bleaching gels present pHs values that varies from 2.4 to 6.5.35 Recent studies that evaluated this calcium-containing gel reported lower risk of TS (20–40%) than the ones usually reported in the literature for other in-office bleaching products.17,36 In face of that, the extrapolation of the results of this study to other commercial available gels should be done with caution.

Finally one could not omit that the sample size used in this study is a clear limitation of the present study. The study was designed to find a high effect size between participants from the both study groups. The conduction of the same experimental design using higher sample sizes should be encouraged to rule out a possible small difference between groups.

Besides that, the sample selected is mainly composed of young participants, which also limits the generalizability to older adults. Further clinical trials with other commercial products should also be encouraged.

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The in-office bleaching with a 2-day interval yielded similar whitening to the 7-day interval and reduced the treatment time without increasing the bleaching-induced TS.

Conclusion

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Acknowledgments Q4 This study was partially supported by the National Council for

Scientific and Technological Development (CNPq) under grants 301937/2009-5 and 301891/2010-9 as well as Araucária

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Foundation. The authors are also grateful for FGM Dental Products for the donation of the bleaching agents employed in this study.

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Please cite this article in press as: de Paula EA, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. Journal of Dentistry (2014), http://dx.doi.org/10.1016/j.jdent.2014.09.009