SciELO - Scientific Electronic Library Online

 
vol.31 suppl.1Efficiency of polymerization of bulk-fill composite resins: a systematic reviewLight curing in dentistry and clinical implications: a literature review author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Brazilian Oral Research

On-line version ISSN 1807-3107

Braz. oral res. vol.31  supl.1 São Paulo Aug. 2017  Epub Aug 28, 2017

http://dx.doi.org/10.1590/1807-3107bor-2017.vol31.0060 

Critical Review

Randomized clinical trials of dental bleaching – Compliance with the CONSORT Statement: a systematic review

Alessandro Dourado LOGUERCIO(a) 

Bianca Medeiros MARAN(a) 

Taíse Alessandra HANZEN(a) 

Alexandra Mara de PAULA(a) 

Jorge PERDIGÃO(b) 

Alessandra REIS(a) 

(a)Universidade Estadual de Ponta Grossa – UEPG, School of Dentistry, Department of Restorative Dentistry, Ponta Grossa, Paraná, Brazil.

(b)University of Minnesota, Department of Restorative Sciences, Minneapolis, MN, United States of America.

Abstract

We reviewed the literature to evaluate: a) The compliance of randomized clinical trials (RCTs) on bleaching with the CONSORT; and b) the risk of bias of these studies using the Cochrane Collaboration risk of bias tool (CCRT). We searched the Cochrane Library, PubMed and other electronic databases, to find RCTs focused on bleaching (or whitening). The articles were evaluated in compliance with CONSORT in a scale: 0 = no description, 1 = poor description and 2 = adequate description. Descriptive analyses of the number of studies by journal, follow-up period, country and quality assessments were performed with CCRT for assessing risk of bias in RCTs. 185 RCTs were included for assessment. More than 30% of the studies received score 0 or 1. Protocol, flow chart, allocation concealment and sample size were more critical items, as 80% of the studies scored 0. The overall CONSORT score for the included studies was 16.7 ± 5.4 points, which represents 52.2% of the maximum CONSORT score. A significant difference among journal, country and period of time was observed (p < 0.02). Only 7.6% of the studies were judged at “low” risk; 62.1% were classified as “unclear”; and 30.3% as “high” risk of bias. The adherence of RCTs evaluating bleaching materials and techniques to the CONSORT is still low with unclear/high risk of bias.

Key words: Tooth Bleaching; Dental Sensitivity

Introduction

Dental bleaching (or whitening) has become the most sought after treatment by patients in search for esthetics. According to study of Al-Zaera,1 which investigated the research subjects’ satisfaction with dental appearance, nearly 66% of the individuals were dissatisfied with the color of their teeth. Another survey conducted in Ankara, Turkey,2 focused on the treatment of patients who were unhappy with their smile, questioning which treatment these patients would like to receive. About half of the patients suggested dental bleaching (49.9%), followed by esthetic restorations (25.4%), orthodontic treatment (24.5%), and prosthetic restorations (16.9%).

Linked to growing demand, the effectiveness of various protocols and materials used by dental professionals has been extensively studied in the last decades, including longevity of the bleaching outcome.3,4,5,6 Researchers have used clinical or in vitro studies to obtain data that can predict clinical performance, as some subjective factors related to the bleaching protocol, such as postoperative sensitivity and other adverse reactions, cannot be evaluated directly.7,8,9

While laboratory testing is a very useful method to study the diffusion of the components of bleaching gels, such H2O2, into dental pulp,10,11 clinical trials can provide reliable and direct evidence to guide clinicians in their choice of materials for in-office and at-home bleaching.12,13,14,15

Hence, randomized controlled trials (RCTs) are considered the standard research design for the evaluation of health interventions. In fact, RCTs and systematic reviews are at the top level of the evidence hierarchy.16 RCTs, however, may incur risk of spurious results if their design is flawed or if the respective methodology lacks accuracy.17 Several problems with the design and execution of RCTs raise questions regarding the validity and reliability of the respective findings. This situation may lead to an underestimation or overestimation of the true intervention effect.18

Therefore readers should appraise any RCT before a clinical decision is made. This evaluation depends on a good report/writing of the methods and results of RCTs. A group of experts joined efforts in 1996 and proposed several items that should be described in a RCT (CONsolidate Standard Of Randomized Trials [CONSORT] Statement), with the objective of standardizing the reporting of RCTs. The CONSORT Statement was reviewed in 200119 and the most recent version was published in 2010.20,21

Given the importance of RCTs in dental bleaching to make decisions regarding protocols, application time, and commercial brand, the aim of this study was to systematically review the literature in peer-reviewed journals to evaluate a) the compliance of RCTs with the CONSORT Statement and b) the risk of bias in these RCT studies through the Cochrane Collaboration risk of bias tool (CCRT).

Methodology

This study was not registered, as there are no currently known systematic review registries of methodologies.

Search methods

We following databases: MEDLINE via PubMed, Cochrane Library, Brazilian Library in Dentistry (BBO) and Latin American and Caribbean Literature in Health Sciences database (LILACS) and citation bases: Scopus and Web of Science were consulted (Table 1). The reference lists of all primary studies, as well as the related articles link from the PubMed database from each primary study, were manually searched. Articles in Korean, Japanese, Chinese, Arabic and related languages were not included due to difficult translation.

Table 1 Search strategy (07/02/17). 

Pubmed
#1 (((((((((((((((((((tooth discoloration[MeSH Terms]) OR dentition, permanent[MeSH Terms]) OR color[MeSH Terms]) OR color[Title/Abstract]) OR colour[Title/Abstract]) OR “tooth discoloration”[Title/Abstract]) OR “tooth discolouration”[Title/Abstract]) OR “teeth discoloration”[Title/Abstract]) OR “teeth discolouration”[Title/Abstract]) OR “discolored tooth”[Title/Abstract]) OR “discoloured tooth”[Title/Abstract]) OR “discolored teeth”[Title/Abstract]) OR “discoloured teeth”[Title/Abstract]) OR “dental discoloration”[Title/Abstract]) OR “dental discolouration”[Title/Abstract]) OR “tooth staining”[Title/Abstract]) OR “teeth staining”[Title/Abstract]) OR “stained tooth”[Title/Abstract]) OR “stained teeth”[Title/Abstract]) OR “dental staining”[Title/Abstract] #2 ((((((((((((((((((tooth bleaching[MeSH Terms]) OR tooth bleaching agents[MeSH Terms]) OR peroxides[MeSH Terms]) OR hydrogen peroxide[MeSH Terms]) OR carbamide peroxide[Supplementary Concept]) OR peroxides[Title/Abstract]) OR “hydrogen peroxide”[Title/Abstract]) OR “carbamide peroxide”[Title/Abstract]) OR bleaching[Title/Abstract]) OR whitening[Title/Abstract]) OR “in office”[Title/Abstract]) OR “at home”[Title/Abstract]) OR “light activation”[Title/Abstract]) OR “light activated”[Title/Abstract]) OR “laser assisted”[Title/Abstract]) OR “dentist-supervised”[Title/Abstract]) OR nightguard[Title/Abstract]) OR “tray-delivered”[Title/Abstract]) OR “jump-start”[Title/Abstract] #3 (randomized controlled trial[pt] OR controlled clinical trial[pt] OR randomized controlled trials[mh] OR random allocation[mh] OR double-blind method[mh] OR single-blind method[mh] OR clinical trial[pt] OR clinical trials[mh] OR (“clinical trial”[tw]) OR ((singl*[tw] OR doubl*[tw] OR trebl*[tw] OR tripl*[tw]) AND (mask*[tw] OR blind*[tw])) OR (placebos[mh] OR placebo*[tw] OR random*[tw] OR research design[mh:noexp] OR comparative study[pt] OR evaluation studies as topic[mh] OR follow-up studies[mh] OR prospective studies[mh] OR control*[tw] OR prospective*[tw] OR volunteer*[tw]) NOT (animals[mh] NOT humans[mh]))
#1 AND #2 AND #3
Cochrane Library
#1 MeSH descriptor: [Tooth Discoloration] explode all trees #8 MeSH descriptor: [Tooth Bleaching Agents] explode all trees
#2 MeSH descriptor: [Dentition, Permanent] explode all trees #9 MeSH descriptor: [Peroxides] explode all trees
#3 MeSH descriptor: [Color] explode all trees #10 MeSH descriptor: [Hydrogen Peroxide] explode all trees
#4 color:ti,ab,kw or t*th next discoloration:ti,ab,kw or discolored next t*th:ti,ab,kw or dental next discoloration:ti,ab,kw or t*th next staining:ti,ab,kw (Word variations have been searched) #11”carbamide peroxide”:ti,ab,kw or peroxides:ti,ab,kw or “hydrogen peroxide”:ti,ab,kw or bleaching:ti,ab,kw or whitening:ti,ab,kw (Word variations have been searched)
#5 stained next t*th:ti,ab,kw or dental next staining:ti,ab,kw (Word variations have been searched) #12 “in office”:ti,ab,kw or “at home”:ti,ab,kw or light next activat*:ti,ab,kw or laser next assisted:ti,ab,kw or dentist supervised:ti,ab,kw (Word variations have been searched)
#6 #1 or #2 or #3 or #4 or #5 #13 nightguard:ti,ab,kw or tray delivered:ti,ab,kw or jump start:ti,ab,kw (Word variations have been searched)
#7 MeSH descriptor: [Tooth Bleaching] explode all trees #14 #7 or #8 or #9 or #10 or #11 or #12 or #13
#15 #6 AND #14
Lilacs and BBO
#1 (MH: “tooth discoloration” OR MH: “permanent dentition” OR MH:color OR color OR cor OR colour OR “tooth discoloration” OR “descoloração do dente” OR “decoloración del diente” OR “descoloración del diente” OR “tooth discolouration” OR “teeth discoloration” OR “descoloração dos dentes” OR “decoloración de los dientes” OR “descoloración de los dientes” OR “teeth discolouration” OR “discolored tooth” OR “dente descolorido” OR “discoloured tooth” OR “discolored teeth” OR “dentes descoloridos” OR “diente pigmentado” OR “dientes pigmentados” OR “dentes pigmentados” OR “dente pigmentado” OR “discoloured teeth” OR “dental discoloration” OR “descoloração dental” OR “decoloración dental” OR “decoloración dentaria” OR “descoloración dental” OR “descoloración dentaria” OR “dental discolouration” OR “tooth staining” OR “manchamento dental” OR “tinción dental” OR “tinción dentaria” OR “pigmentación dental” OR “pigmentación dentaria” OR “teeth staining” OR “dentes manchados” OR “stained tooth” OR “dente manchado” OR “stained teeth” OR “mancha nos dentes” OR “mancha en los dientes” OR “dental staining” OR “mancha en lo diente” OR “mancha no dente”) #2 (MH:”tooth bleaching” OR MH:”tooth bleaching agents” OR MH:peroxides OR MH:”hydrogen peroxide” OR peroxides OR peróxidos OR “hydrogen peroxide” OR “peróxido de hidrogênio” OR “carbamide peroxide” OR “peróxido de carbamida” OR bleaching OR branqueamento OR blanqueo OR whitening OR clareamento OR blanqueamiento OR clareamiento OR “in-office” OR “em consultório” OR “en ambulatorio” OR “at home” OR caseiro OR “casero” OR “light activation” OR fotoativação OR “activación por luz” OR “light activated” OR “ativado por luz” OR “activado por luz” OR “laser assisted” OR “a laser” OR “con láser” OR “dentist-supervised” OR “superviosionado por dentista” OR “supervisado por el dentista” OR nightguard OR “tray-delivered” OR moldeira OR cubeta OR “jump-start” OR associado OR combinado)
#1 AND #2
Web of science
#1Tópico: (“t*th discolo*ration”) OR Tópico: (“permanent dentition”) OR Tópico: (colo$r) OR Tópico: (“discolo*red t*th”) OR Tópico: (“dental discolo*ration”) OR Tópico: (“t*th staining”) OR Tópico: (“stained t*th”) OR Tópico:(“dental staining”) #2 Tópico:(“t*th bleaching”) OR Tópico:(peroxides) OR Tópico: (“hydrogen peroxide”) OR Tópico: (“carbamide peroxide”) OR Tópico: (bleaching) ORTópico: (whitening) OR Tópico: (“in-office”) OR Tópico: (“at home”) ORTópico: (“light activat*”) OR Tópico:(“laser assisted”) OR Tópico:(“dentist-supervised”) OR Tópico:(nightguard) OR Tópico: (“tray-delivered”) OR Tópico: (“jump-start”)
#1 AND #2
Scopus
#1 (TITLE-ABS-KEY (“t*th discoloration”) OR TITLE-ABS-KEY (“permanent dentition”) OR TITLE-ABS-KEY (colo*r) OR TITLE-ABS-KEY (“t*th discolouration”) OR TITLE-ABS-KEY (“discolored t*th”) OR TITLE-ABS-KEY (“discoloured t*th”) OR TITLE-ABS-KEY (“dental discolo*ration”) OR TITLE-ABS-KEY (“t*th staining”) OR TITLE-ABS-KEY (“stained t*th”) OR TITLE-ABS-KEY (“dental staining”)) #2 (TITLE-ABS-KEY (“t*th bleaching”) OR TITLE-ABS-KEY (peroxides) OR TITLE-ABS-KEY (“hydrogen peroxide”) OR TITLE-ABS-KEY (“carbamide peroxide”) OR TITLE-ABS-KEY (bleaching) OR TITLE-ABS-KEY (whitening) OR TITLE-ABS-KEY (“in office”) OR TITLE-ABS-KEY (“at home”) OR TITLE-ABS-KEY (“light activat*”) OR TITLE-ABS-KEY (“laser assisted”) OR TITLE-ABS-KEY (“dentist-supervised”) OR TITLE-ABS-KEY (nightguard) OR TITLE-ABS-KEY (“tray-delivered”) OR TITLE-ABS-KEY (“jump-start”))
#1 AND #2

According to the MEDLINE database, a search strategy was defined according to a terminology for indexing biomedical information (MeSH, Medical Subject Headings, U.S. National Library of Medicine, Bethesda, MD, USA) along with free keywords. For each database, the search strategy was adapted for consultation. In order to standardize the articles evaluated, only studies published since the CONSORT Statement declaration in 1996 were included.

Eligibility criteria

We included parallel and split-mouth RCTs that evaluated the effectiveness of different types of bleaching systems and techniques on color change, toxicity, postoperative sensitivity and application technique. We did not restrict studies with patients of different age groups or populations (Table 2).

Table 2 Inclusion and exclusion criteria. 

Inclusion criteria Exclusion criteria
Parallel and Split-mouth RCTs published in 1996 or later Laboratory studies
Conference abstracts
Different types of bleaching systems (in-office, at home and jump-start) (bleaching strips, gels, dentifrices, use of light) regarding. Thesis
Studies that evaluate color change, toxicity, postoperative sensitivity and application technique Reports published in any media other than peer-reviewed journals
The studies included patients of any age group Reported cases

Laboratory studies were excluded, as well as those presented as conference abstracts, theses and reports published in any media other than peer-reviewed journals. Additionally, all studies that were published before 1996 were excluded (Table 2).

Three reviewers (A.P., B.M.M. and T.H.) catalogued articles that met the inclusion criteria. Article selection was carried out by first reading the titles and abstracts; then the full text of the paper was read in case of doubts.

Adherence to CONSORT statement

An evaluation tool based on the items related to the methods and results from the 2010 CONSORT Statement20 was developed to evaluate the reporting completeness of RCTs (Table 3).22 The items related to the title and abstract, introduction and discussion were not evaluated since the evaluation would have been very subjective and the adherence to these items would not weaken the quality of the study report or the risk of bias of the studies.

Table 3 Instrument tool developed from the 2010 CONSORT Statement to evaluate the compliance of the studies to the CONSORT Statement. 

CONSORT item Sub-item Score Adherence to the methods and results items of the consort statement

Description
Trial design Positive [2] The trial design is clearly written in the text (split mouth, cross-over, factorial, cluster).
Negative [0] This information is not reported.
Poor [1] 1. Information can be obtained during reading the manuscript, although this is not explicity reported by the authors. 2. There is lack of consistence between sections of the article (examples - abstract does not match the material and methods section; the presentation of the results does not match the description of the trial design; flow diagram presents different information, etc.).
Participants Eligibility criteria Positive [2] The inclusion and exclusion criteria is clear, so that readers can know exactly which population the data can be extrapolated to.
Negative [0] The information is not reported.
Poor [1] 1. Incomplete information of eligibility criteria compared to most of the studies on the field. 2. Presence of inconsistencies in the inclusion/exclusion criteria that prevents the readers from knowing the population at which the intervention/control groups were performed.
Settings and location Positive [2] Clear description of the setting (academic, practice-based research, university, private clinics, etc.) as well as the date at which the intervention was implemented.
Negative [0] The setting and/or the location is not reported in the text.
Poor [1] 1. Authors describe either the setting or the date but never both. 2. This information can be obtained indirectly in the text
Interventions Positive [2] The interventions for each group are described with sufficient details to allow replication, including how they were actually administered.
Negative [0] There is no description.
Poor [1] There are missing information that prevents the replication of the interventions/comparators.
Outcomes Positive [2] At least the primary outcomes were defined in details, including how and when they were assessed. Consider it as clear when the details are clear, but the authors did not use the term “primary outcome” or related synonyms.
Negative [0] There is no definition of the primary outcome and/or secondary outcomes.
Poor [1] 1. The authors only report they have used a specific criteria without detailing the most important outcomes of such criteria. 2. The description of the primary outcome and/or secondary outcomes is very superficial and does not allow replication of the method.
Sample size Positive [2] Method of sample size calculation is described in a way to allow replication. It should be identified the primary outcome for each the sample size was calculated for. Elements of the sample size calculation are (1) the estimated outcomes in each group (which implies the clinically important target difference between the intervention groups); (2) the α (type I) error level; (3) the statistical power (or the β (type II) error level); and (4), for continuous outcomes, the standard deviation of the measurements should be reported. For equivalence trials, the equivalence limit, instead of the effect size should be reported.
Negative [0] There is no description in the article.
Poor [1] The sample size is described but some parameters are missing so that it prevents replication.
Randomization Sequence generation Positive [2] 1. Clear description of the random sequence generation. 2. or clear description of a non-random sequence method.
Negative [0] There is no information in the text.
Poor [1] The authors only provide a very superficial description (such as the “groups were randomly allocated”) or do not provide sufficient information to allow replication of the randomization process.
Allocation concealment Positive [2] Clear description of the allocation concealment. See next columns for evaluation of the Risk of Bias.
Negative [0] There is no information in the text.
Poor [1] not applicable
Blinding Positive [2] 1) The authors describe who is blinded in the study. 2. In single-blind studies (when this is clearly reported by the authors), just the description of participant or evaluator (the one blinded) is enough; however when the study is double blind or triple blind all blinded people should be described. 2) The study describes just the participant or examiner blinded but one of these people cannot be blinded by intrinsic features of the study design.
Negative [0] There is no description of the blinding.
Poor [1] Insufficient/partial information. For instance, (1) the authors describe examiners’ blinding or participants’ blinding, but never both. (2) The authors describe the study was blind or double-blind but does not specify who was blinded.
Statistical methods Hypothesis testing Positive [2] Statistical methods are described with enough detail to enable a knowledgeable reader with access to the original data to verify the reported results. Additionally, statistical tests employed by the authors seem to be adequate for the type of trial design and nature of the data collected.
Negative [0] Statistical methods are not described.
Poor [1] 1) There is not enough information to evaluate the statistical method used by the authors and/or the type of statistical tests employed by the authors are inadequate for the trial design and/or nature of the data (for instance, tests that do not take into account the paired nature of the data when this is the case). 2) The authors describe several statistical tests but does not specify for each outcome they were applied.
Estimated effect size Positive [2] Authors report at least for the primary outcome the effect size and its precision (such as 95% confidence interval). Odds ratio, risk ratio, risk difference, mean difference, etc.
Negative [0] There is no description of the effect size and 95% confidence interval
Poor [1] There is incomplete information.
Participant flow Flow diagram Positive [2] For each group, the numbers of participants who were randomly assigned, received intended treatment and were analyzed for the primary outcome is described in the flow chart CONSORT diagram.
Negative [0] The flow-chart is not presented in the article.
Poor [1] 1. There are inconsistencies between the numbers described in the flow-chart and other parts of the manuscript. 2. Incomplete diagram with missing information
Losses/Exclusions Positive [2] 1. For each group, losses and exclusions after randomization are described with reasons. 2. During reading, reviewer observes that there is no loss to follow-up.
Negative [0] 1. There is no description of losses and exclusions.
Poor [1] Incomplete information. For instance, 1. the authors describe the overall percentage of losses but this information is not specified per group. 2. The authors describe the losses and exclusions but does not specify the reasons
Baseline data Positive [2] A table/text description containing baseline demographic and clinical characteristics of each group are presented in the article.
Negative [0] There is no table/text description with baseline data or description in the body of the text.
Poor [1] 1. A table/ text description with baseline data is presented but the data is not distributed between the study groups and/or given in percentages instead of raw numbers. 2. Insufficient information about participants is provided; 3. Inconsistencies in the data presented can be observed.
Numbers analysed Positive [2] For each group and for each outcome, the number or participants (denominator) included in the analysis are clear.
Negative [0] Authors do not report the numbers analyzed.
Poor [1] There is no clear description of the number of participants (denominator) included in the analysis of at least one of the outcomes. 2. Instead of reporting the raw number of participants, the authors report their data in percentages. 3. The authors fail to report the baseline number of patients included in each analysis. 4. Data can be obtained indirectly in the study.
Registration and protocol Positive [2] The study was registered in a trial registry and the protocol number is provided.
Negative [0] This information is not available in the manuscript. Registration in an Ethics Committee is valid as trial registry
Poor [1] The authors describe that the study was registered but does not provide the registration number and/or the number provided does not link to the study.

A total of 12 items of the CONSORT Statement were included in this CONSORT evaluation tool. As some of these items were subdivided, a total of 16 items were evaluated. The given score per item ranged from 0 to 2. In general words, 0 = no description, 1 = poor description and 2 = adequate description. More details regarding the scoring process for each score of each item are displayed in Table 3. Each item was given an equal weighting.

Prior to evaluation, the instrument was discussed between two experienced authors in clinical trials (A.D.L. and A.R.), pilot-tested in 15 articles and checked for accuracy and reproducibility by three evaluators. This process yielded modification of the instrument tool, as new possibilities for each score were observed and discussed during pilot testing.

Three reviewers (A.P., B.M.M. and T.H.) performed the round of scoring using the CONSORT evaluation tool as guide (Table 3). In case of disagreement a discussion followed and the consensus was used to determine the final score. Evaluators were not blinded to the study authors. This was not feasible, as reviewers were familiar with the studies and could easily guess the researchers’ affiliation by reading the paper.

Scoring system and statistical analysis

The number of studies by journal, follow-up period and country were analyzed descriptively. Compliance with individual items of the CONSORT Statement was analyzed to identify areas in which authors could improve the description. A chart with the percentage of studies per score in each item was provided.

To achieve an overall compliance score, the scores for the 16 items were added in each article. A trial with adequate descriptions (score 2) for all CONSORT items would have received a maximum score of 32. A mean average score was calculated by period of time, journal and country. Comparison within each factor was performed with the Kruskall-Wallis and Mann-Whitney test at a level of confidence of 95%. Linear correlation analysis between 2015 ISI journal impact factor and the average CONSORT score was also performed.

These additional analyses aimed at offering information about whether improvements in the average CONSORT score occurred over the time and if these improvements were related to the journal and respective impact factor, as well as the living country of the first author.

Risk of bias in individual studies

Quality assessments were performed by two independent reviewers, using the Cochrane Collaboration’s tool for assessing risk of bias in randomized trials (CCRT).23 The assessment criteria contain six domains: sequence generation, allocation concealment, blinding of the outcome assessors, incomplete outcome data, selective outcome reporting, and other possible sources of bias. Each domain of the Cochrane risk of bias tool was evaluated at low, high or unclear risk of bias. After assessment of the domains, each study was then evaluated into low risk of bias if all domains were at low risk. The study was judged as at high risk of bias if at least one of the key domains was evaluated as high risk of bias. And finally, the study would be considered at unclear risk, if at least one domain were judged at unclear risk of bias.

Results

Characteristics of the included studies

From the 1925 articles that were originally screened, after removal of duplicates, 1756 were excluded for not complying with the inclusion criteria. The full-text of 234 papers were assessed and 49 papers were excluded for the following reasons: 1) 15 studies were not randomized clinical trials; 2) 7 studies were case reports; 3) 3 studies were duplicates; 4) 2 studies were abstracts; 5) 1 study was published in Korean language; 6) 4 studies were in vitro; 7) 2 studies were case series; 8) 1 study was a literature review; 9) 1 study was an ex-vivo study; 10) 1 study is currently in the recruitment phase and evaluation of tooth color (results not yet available); 11) 1 study evaluated the color change of the composite resin after bleaching; 12) 11 studies were not accessible. After these exclusions, 185 RCTs remained for assessment (Figure 1).

Figure 1 PRISMA Flow chart diagram. 

The included RCTs investigated several topics, such as the comparison of 1) at-home dental bleaching techniques; 2) in-office dental bleaching techniques; 3) patient related factors; 4) in-office vs. at home and 5) combined bleaching techniques.

Table 4 displays the 185 RCTs tabulated by their collected characteristics. The journals contributing with the most RCTs were Oper Dent (17.8%), followed by Comp Cont Educ Dent (11.4%), Am J Dent (7.6%) and Quintessence Int (7.0%). Approximately 29.2% of the publications were published in 37 different journals. The countries with most publications were USA (40.5%) and Brazil (28.1%), representing together about 70% of all publications in the field. The most frequent follow-up period (days) reported in the articles occurred between 14 (22.7%) and 28 (10.3%) days.

Table 4 Characteristics of the included studies by categories. 

Characteristics Categories Number of studies Percentage (%)
Journal Clin Oral Investig 5 2.7
J Clin Dent 10 5.4
J Esthet Restor Dent 11 5.9
J Dent 12 6.5
JADA 12 6.5
Quintessence Int 13 7.0
Am J Dent 14 7.6
Comp Cont Educ Dent 21 11.4
Oper Dent 33 17.8
Others* 54 29.2
Country UK 6 3.2
Italy 7 3.8
Germany 14 7.6
Brazil 52 28.1
USA 75 40.5
Others** 31 16.8
Period of time 1996 to 2000 17 9.2
2001 to 2005 48 25.9
2006 to 2010 52 28.1
2011 to 2016 68 36.8
Follow-up period (days) 0 5 2.7
7 12 6.5
14 42 22.7
21 10 5.4
28 19 10.3
30 6 3.2
42 5 2.7
168 12 6.5
Others*** 74 40.0

*Representing 37 different journals; **Representing 18 different countries; ***Representing 33 different follow-up period (days).

Study compliance with each of the CONSORT instrument tool items

Figure 2 displays the percentage of studies per score for each item of the CONSORT Statement in percentage of studies. In regard to the items’ intervention and outcomes, more than 80% of the studies were scored as 2, with an adequate reporting. For the items eligibility, hypothesis testing, losses/exclusion and numbers analyzed, more than 50% of the studies were scored as 2.

Figure 2 Percentage of studies per CONSORT score for each CONSORT item analyzed. 

More than 50% of the studies received score 1 (poor reporting) or score 0 (no reporting) for all other items. This was more critical with the items protocol, flow chart, allocation concealment and sample size where more than 80% of the studies were scored as 0 (no reporting).

In order to help future randomized clinical trials of bleaching, some examples of adequate description of each item of the results, material and methods of CONSORT were added in Tables 5 to 9.

Table 5 Examples of adequate description of the evaluate parameters of the Instrument tool developed from the 2010 CONSORT Statement for bleaching studies. 

Item Examples
Trial design
Example 1: “This study was a randomized, single-blind, controlled trial with a parallel group and an allocation rate of 1:1.”56
Example 2: “This was a randomized, parallel, placebo-controlled, triple-masked clinical trial, in which the patient, operator, and evaluator were masked to the group assignment. A third researcher, not involved in the evaluation process, was responsible for the randomization process, and delivery and guidance on the administration of the drugs.”57
Participants
Eligibility criteria The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Settings and locations Example 1: “The study took place in the clinics of the dentistry schools at the State University of Ponta Grossa, Paraná, and the University of São Paulo, São Paulo, from June 2010 to June 2012.”58
Example 2: “This study was performed from February 2011 to March 2012 in the city of Guarapuava (Paraná, Brazil).”12
Interventions The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Outcomes The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Sample size
For Tooth sensitivity For superiority trial: “The primary outcome of this study was the absolute risk of TS. The absolute risk of TS (that is, the number of patients [percent] who reported pain at some point during dental bleaching) was reported to be approximately 87% (4,8) for the bleaching product Whiteness HP Maxx (FGM Dental Products). Thus, a minimum sample size of 56 participants was required to have a 90% chance of detecting, as significant at the 2-sided 5% level, a decrease in the primary outcome measure from 86% in the control group to 50% in the experimental group.”57
For equivalent trial: 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).”59
For Color evaluation For superiority trial: “The primary outcome of this study was color change of the participants’ teeth. A previous study (34) reported that two bleaching sessions with the product Whiteness HP Maxx 35% (FGM Dental Products, Joinville, SC, Brazil) without light activation produced a whitening effect of about 7 ± 2 SGUs. To detect a difference of 2 SGUs between the means of any pair of the study groups, with a power of 80% and an alpha of 5%, a minimum sample size of 17 patients per group was required. This threshold of perceptibility was based on the fact that ‘‘untrained’’ people, such as the patients, do not detect easily changes of one shade guide unit at the lighter end of the vita classical guide.”58
For equivalent trial: We based the sample size calculation on the color change measured with the spectrophotometer (DE), the primary outcome of the study. One hundred eighteen participants were required to exclude a difference of means of 2.0 units of DE at 1 week and 1 month (equivalence limit) with a power of 90 % and a of 5 %. With these calculations, we took into consideration a standard deviation of 3.3 in the DE. The equivalence limit we chose was lower than the DE threshold of 3.0, above which color differences become clinically perceptible (24-26).”60
Randomisation
Sequence generation, allocation concealment and implementation Example 1: “The randomization process was performed by coin toss immediately before the bleaching procedure to provide adequate allocation concealment.”61
Example 2: “Participants were randomly divided into four groups according to the combination of the main factors: HP (20% or 35%) and light activation (with or without). A third person who was not involved in the research protocol performed the randomization procedure by using computer-generated tables. We used blocked randomization (block sizes of 2 and 4) with an equal allocation ratio (www.sealedenvelope.com). Opaque and sealed envelopes containing the identification of the groups were prepared by a third party not involved in the study intervention.”58
Blinding Example 1: “The participant and the operator could not be blinded to the procedure, as the application of bleaching gel for different times could not be masked. However, the examiners who evaluated the color changes were not aware of which group the participant was assigned to.”62
Example 2: “Neither the participant nor the operator knew the group allocation, both being blinded to the protocol.” “The two examiners, blinded to the allocation assignment, scheduled these patients for bleaching and evaluated their teeth against the shade guide at baseline and 30 days after the procedure.”63
Statistical methods
Hypothesis testing The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Estimated effect size Two examples of how to report an effect size can be seen in Tables 6 and 7.
Participants
Flow diagram Please see the following link to have access templates of the CONSORT flow diagram available in MS Word (http://www.consort-statement.org/consort-statement/flow-diagram)
Losses and exclusions The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Baseline data Two examples of how to report an effect size can be seen in Tables 8 and 9.
Numbers analysed The authors judged that it was not necessary to add some examples, because this item showed an adequate reporting as seen in Figure 2.
Registration and protocol Example 1: “The ClinicalTrials.gov identification number was NCT02017873.”4
Example 2: “The clinical investigation was approved (protocol number 172.988) by the scientific review committee and by the committee for the protection of human participants of the local university. It was registered in the Brazilian clinical trials registry under the identification number RBR-6pt2n3.”57

Table 6 Baseline characteristics of the participants. 

Characteristics Smokers Non-smokers
Age (years; mean ± SD)
Brazil 26.3 ± 6.5 24.1 ± 6.8
Chile 29.3 ± 9.4 25.5 ± 6.6
Male (%)
Brazil 46.7 53.3
Chile 63.3 36.7
Baseline color (L*; mean ± SD)
Brazil 82.4 ± 4.9 82.3 ± 4.3
Chile 83.2 ± 4.0 84.9 ± 3.8
Baseline color (b*; mean ± SD)
Brazil 22.6 ± 3.6 23.2 ± 3.6
Chile 22.2 ± 3.1 21.7 ± 2.5
Baseline color (a*; mean ± SD)
Brazil -1.0 ± 1.0 -0.5 ± 1.0
Chile -0.0 ± 0.7 -0.2 ± 0.6
Baseline color (SGU; mean ± SD)
Brazil 6.8 ± 2.3 7.4 ± 2.5
Chile 7.2 ± 1.7 8.4 ± 2.9
Smoking time (years; mean ± SD)
Brazil 8 ± 5.9 -
Chile 11.8 ± 9.1 -
Number cigarettes/day (mean ± SD)
Brazil 13.2 ± 4.0 -
Chile 12.8 ± 3.8 -

Adapted from DeGeus et al. 64

SD: Standard-deviation; L*: luminosity; b*: color along the yellow-blue axis; a*: Color along the red-gree axis;.

Table 7 Demographic features of the participants of each study group. 

Feature 20% 20% + light 35% 35% + light
Age (mean ± SD) 22.9 ± 4.0 22.0 ± 4.4 23.0 ± 3.4 22.0 ± 3.6
Female (n, %) 13 (68) 12 (63) 13 (68) 12 (60)
Baseline SGU (median, 25 and 75 percentil) 12 (11 – 14) 12 (11 – 12) 12 (10,5 – 15) 11 (9 – 12)

Adapted from Mena-Serrano et al. 58

SD: Standard-deviation.

Table 8 Means (standard deviations) of the change in shade guide units obtained with the VITA Classical and VITA Bleachedguide* and the color change measured by spectrophotometer at baseline versus 1-month postbleaching. 

Color evaluation tools Groups p-value Mean difference (95%CI)

Placebo Dexamethasone
Vita Classical 3.1 ± 2.6 3.4 ± 2.3 0.642 - 0.3 (-9.9–10.5)
Dexamethasone 2.8 ± 2.2 2.7 ± 1.6 0.775 - 0.6 (-9.4–10.6)
p-value 6.0 ± 4.7 6.6 ± 4.0 0.582 - 0.6 (-11.4–12.6)

Adapted from Rezende et al. 57

CI: confidence interval.

Table 9 Absolute risk of tooth sensitivity, along with the risk ratio, for both groups at the different assessment points. 

Periods Group Number of patients with TS Absolute risk (95%CI) Risk ratio (95%CI) p-value*

Yes No
During in-office session HP35% 17 3 85.0 (64.0–95.0) 1.8 (1.1– 3.2) 0.02
HP20% 7 8 47.0 (25.0–69.0)
Up to 48 h after in-office session HP35% 13 7 65.0 (43.2–81.9) 2.0 (0.9–4.3) 0.09
HP20% 5 10 33.3 (15.2–58.3)
During at-home bleaching HP35% 5 15 25.0 (11.2–46.9) 1.3 (0.5–3.8) 0.71
HP20% 5 10 33.3 (15.2–58.3)

Adapted from Rezende et al. 61

Fisher’s exact test; TS: tooth sensitivity; CI: confidence interval.

Average CONSORT score per study characteristics

The overall CONSORT score for the included studies in this review was 16.7 ± 5.4 points, which represents 52.2% of the maximum CONSORT score of 32 points. We observed a significant influence of journal, country, and period of time on the average CONSORT score (Table 10). Significant differences among journals were observed (p < 0.0001; Table 10), with the average CONSORT scores of J Dent (higher score), Oper Dent, Clin Oral Investig and JADA being higher than the remaining journals. ‘Other journals’ are composed of 37 different journals, which published 54 different papers (29.1% of total). A significant but weak correlation between average CONSORT score and impact journal factor was observed (r = 0.16; p < 0.0001, Figure 3).

Table 10 Average CONSORT score per journal, country and period of time. 

Characteristics Categories Mean ± SD Median (interquartile range) p-value*
Journal Clin Oral Investig 19.60 ± 6.58 A 18 (18–22) < 0.0001
J Clin Dent 16.30 ± 1.42 A,B 16 (15–17)
J Esthet Restor Dent 15.27 ± 3.04 A,B 14 (13–17.5)
J Dent 21.75 ± 6.50 A 20 (17.5–28.25)
JADA 19.33 ± 5.28 A 19.5 (13–22.5)
Quintessence Int 15.54 ± 4.33 A,B 14 (13–16)
Am J Dent 18.36 ± 4.22 A,B 18.5 (16.25–19.75)
Comp Cont Educ Dent 15.24 ± 3.06 A,B 15 (13–18)
Oper Dent 19.94 ± 6.32 A 18 (15–25)
Others 13.80 ± 4.99 B 13 (11–16)
Country UK 14.83 ± 2.99 B 15 (12.5–17.5) 0.02
Italy 14.29 ± 6.80 B 13 (9.5–19)
Germany 16.71 ± 4.05 A,B 17 (14.25–18)
Brazil 19.48 ± 6.93 A 20.5 (13.75–25)
USA 15.25 ± 3.13 B 15 (13.5–18)
Others 16.10 ± 4.99 A,B 14.5 (12.25–18)
Period of time 1996 to 2000 13.47 ± 4.03 B 14 (11–16) 0.004
2001 to 2005 15.54 ± 2.81 A,B 16 (14–18)
2006 to 2010 15.75 ± 4.01 A,B 15 (13–19)
2011 to 2016 19.03 ± 6.87 A 18 (13.75–25)

*Kruskall Wallis and Mann-Whitney tests.

Figure 3 Linear regression between Impact Factor and Consort Score. 

Regarding country, a significant difference was also observed (p = 0.02; Table 10). Brazil showed the highest average CONSORT score, being statistically higher than those of UK, Italy and USA. On the same line, the period of time in years had a significant influence on the average CONSORT score (p = 0.004; Table 10). We observed an increase in the average CONSORT score in the 2011-2016 interval (19.0 ± 6.8) in comparison with the 1996-2000 period (13.4 ± 4.0). The individual CONSORT score for each one of the included studies can be seen in Table 11.

Table 11 List of the scored papers along with their average CONSORT score and evaluation of the risk of bias in each domain. 

Study identification Year Journal Average CONSORT score Risk of bias tool

random sequence allocation concealment participant blinding examiner blinding incomplete outcome data selective reporting
Acosta Gómez et al.34 1999 Univ Odontol 11 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Al Shethri et al.65 2003 Oper Dent 18 LOW UNCLEAR UNCLEAR UNCLEAR LOW LOW
Almeida et al.66 2012 Int J Periodontics Restorative Dent 16 UNCLEAR UNCLEAR HIGH HIGH LOW HIGH
Alomari, El Daraa67 2010 J Contemp Dent Pract 13 UNCLEAR UNCLEAR LOW LOW LOW LOW
Alonso de la Peña, Balboa Cabrita68 2006 Quintessence Int 14 UNCLEAR HIGH HIGH HIGH HIGH LOW
Alonso de la Peña, Lopez Ranton69 2014 Oper Dent 18 LOW UNCLEAR HIGH HIGH LOW LOW
Auschill et al.70 2005 Oper Dent 18 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Auschill et al.71 2012 Quintessence Int 26 LOW LOW UNCLEAR LOW LOW LOW
Barlow et al.72 2009 Int J Dent 21 LOW UNCLEAR UNCLEAR LOW LOW LOW
Barnes et al.73 1998 Comp Cont Educ Dent 15 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Basting et al.74 2012 Oper Dent 21 LOW LOW UNCLEAR LOW LOW LOW
Berga-Caballero et al.75 2006 Med Oral Patol Oral Cir Bucal 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Bernardon et al.76 2010 Oper Dent 16 LOW UNCLEAR UNCLEAR LOW LOW LOW
Bernardon et al.77 2015 J Prosthet Dent 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH
Bernardon et al.78 2016 J Prosthet Dent 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Bizhang et al.79 2007 Am J Dent 20 UNCLEAR HIGH UNCLEAR UNCLEAR LOW HIGH
Bizhang et al.80 2009 Oper Dent 18 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Bonafé et al.81 2014 Clin Oral Investig 22 LOW UNCLEAR LOW LOW LOW LOW
Bortolatto et al.82 2016 Lasers Med Sci 26 LOW LOW LOW LOW LOW LOW
Braun et al.83 2007 Dent Mater 15 HIGH UNCLEAR LOW LOW LOW LOW
Browning et al.84 2012 J Esthet Restor Dent 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Browning et al.85 2004 Oper Dent 13 UNCLEAR UNCLEAR LOW LOW UNCLEAR LOW
Bruhn et al.86 2012 Int J Dent Hyg 16 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Callan et al.87 2008 Am J Dent 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Cardoso et al.88 2011 JADA 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Carvalho et al.89 2005 Rev Assoc Paul Cir Dent 6 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Cerqueira et al.90 2013 Rev Assoc Paul Cir Dent 19 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Cibirka et al.91 1999 J Esthet Dent 15 LOW UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Collins et al.92 2004 J Dent 19 HIGH UNCLEAR UNCLEAR LOW UNCLEAR LOW
Corbella et al.93 2009 Dent Cadmos 8 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH
Cronin et al.94 2005 Comp Cont Educ Dent 16 UNCLEAR UNCLEAR UNCLEAR LOW UNCLEAR HIGH
da Costa et al.95 2010 Oper Dent 19 LOW UNCLEAR UNCLEAR UNCLEAR LOW LOW
da Costa et al.96 2011 J Esthet Restor Dent 22 LOW LOW UNCLEAR LOW LOW LOW
Dawson et al.97 2011 Oper Dent 19 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
de Almeida et al.98 2014 Photomed Laser Surg 20 UNCLEAR UNCLER LOW LOW LOW LOW
de Freitas et al.99 2016 Quintessence Int 17 LOW UNCLEAR UNCLEAR LOW UNCLEAR LOW
de Geus et al.100 2015 JADA 29 LOW LOW UNCLEAR LOW LOW LOW
de Geus et al.4 2015 J Dent 28 LOW LOW UNCLEAR UNCLEAR LOW LOW
de Geus et al.64 2015 Oper Dent 25 LOW LOW LOW LOW LOW LOW
de Paula et al.63 2013 Clin Oral Invest 29 LOW LOW LOW LOW LOW LOW
de Paula et al.59 2015 J Dent 29 LOW LOW UNCLEAR LOW LOW LOW
de Paula et al.12 2014 Oper Dent 30 LOW LOW LOW LOW LOW LOW
Delgado et al.101 2007 P R Health Sci J 16 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR
Deliperi et al.102 2004 JADA 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Donly et al.103 2002 Comp Cont Educ Dent 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Donly et al.104 2005 Pediatr Dent 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Donly et al.105 2006 Gen Dent 15 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Donly et al.106 2007 Gen Dent 21 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Donly et al.107 2010 Am J Dent 19 HIGH UNCLEAR UNCLEAR LOW LOW LOW
Farrel et al.108 2006 J Clin Dent 18 HIGH UNCLEAR LOW LOW LOW LOW
Fernandez et al.109 2016 Oper Dent 30 LOW LOW LOW LOW LOW LOW
Ferrari et al.110 2004 Am J Dent 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Gallagher et al.111 2002 J Clin Dent 15 UNCLEAR UNCLEAR HIGH LOW LOW LOW
Gallo et al.112 2009 Quintessence Int 14 UNCLEAR UNCLEAR LOW LOW UNCLEAR LOW
Garcia-Godoy et al.113 2004 Comp Cont Educ Dent 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Gerlach et al.114 2000 Comp Cont Educ Dent 20 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Gerlach et al.115 2001 Am J Dent 18 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Gerlach et al.116 2002 Comp Cont Educ Dent 16 HIGH UNCLEAR LOW LOW LOW HIGH
Gerlach et al.117 2004 J Clin Dent 15 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Gerlach et al.118 2005 Comp Cont Educ Dent 15 HIGH UNCLEAR LOW LOW LOW LOW
Gerlach, Barker119 2003 Am J Dent 20 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Gerlach, Sagel120 2004 JADA 15 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Gerlach et al.121 2002 Am J Dent 20 HIGH UNCLEAR UNCLEAR LOW LOW LOW
Gerlach, Zhou121 2004 Comp Cont Educ Dent 20 HIGH UNCLEAR UNCLEAR LOW LOW LOW
Giachetti et al.122 2010 JADA 23 LOW LOW UNCLEAR UNCLEAR LOW LOW
Giniger et al.123 2005 J Clin Dent 15 HIGH UNCLEAR UNCLEAR LOW LOW LOW
Giniger et al.124 2005 JADA 21 HIGH UNCLEAR LOW LOW LOW LOW
Gomes et al.13 2008 R Dent Press Estet 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW HIGH
Goodson et al.125 2005 J Clin Dent 11 LOW UNCLEAR LOW LOW UNCLEAR HIGH
Grobler et al.126 2011 Int J Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Guênes et al.127 2015 RFO UPF UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Guerrero et al.128 2007 Am J Dent 20 UNCLEAR UNCLEAR LOW LOW LOW LOW
Gurgan et al.129 2010 Lasers Med Sci 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Hanning et al.130 2007 Clin Oral Investig 18 UNCLEAR UNCLEAR LOW LOW LOW HIGH
Henry et al.131 2013 Int J Dent Hyg 18 UNCLEAR UNCLEAR LOW HIGH LOW LOW
Hyland et al.132 2015 Clin Oral Investig 11 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH
Ishikawa-Nagai et al.133 2004 J Esthet Restor Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Jadad et al.134 2011 Am J Orthod Dentofacial Orthop 9 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Javaheri, Janis135 2000 Oper Dent 6 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH
Karpina et al.136 2002 Am J Dent 14 UNCLEAR UNCLEAR LOW LOW LOW LOW
Karpina et al.137 2003 J Prosthodont 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW HIGH
Kihn et al.138 2000 JADA 17 HIGH UNCLEAR LOW LOW LOW LOW
Kihn et al.139 2002 Comp Cont Educ Dent 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Knosel et al.140 2007 Angle Orthod 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Knosel et al.141 2008 Quintessence Int 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Kose et al.142 2011 Am J Dent 20 LOW UNCLEAR LOW LOW LOW LOW
Kose et al.62 2016 Oper Dent 28 LOW LOW LOW LOW LOW LOW
Kossatz et al.143 2011 Oper Dent 17 LOW UNCLEAR LOW LOW LOW LOW
Kossatz et al.144 2012 JADA 25 LOW UNCLEAR LOW LOW LOW LOW
Kozlovsky et al.145 1996 Oral Health 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH LOW
Krause et al.146 2008 Quintessence Int 13 HIGH UNCLEAR LOW LOW UNCLEAR LOW
Kugel et al.147 2002 Comp Cont Educ Dent 11 HIGH UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Kugel et al.148 2006 Comp Cont Educ Dent 12 UNCLEAR UNCLEAR LOW LOW LOW LOW
Kugel et al.149 2004 Comp Cont Educ Dent 19 UNCLEAR UNCLEAR LOW LOW LOW LOW
Kugel et al.150 2009 J Esthet Restor Dent 19 HIGH UNCLEAR LOW LOW LOW LOW
Kugel, Kastali151 2000 Comp Cont Educ Dent 18 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Leonard et al.152 1999 J Esthet Restor Dent 13 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Leonard et al.153 2001 J Esthet Restor Dent 18 HIGH UNCLEAR LOW UNCLEAR LOW LOW
Leonard et al.154 2004 J Esthet Restor Dent 12 UNCLEAR UNCLEAR HIGH LOW UNCLEAR LOW
Lewgoy et al.155 2011 Rev ABO Nac 6 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Li et al.156 2003 Comp Cont Educ Dent 18 HIGH UNCLEAR LOW LOW LOW LOW
Lo et al.157 2007 Am J Dent 21 UNCLEAR UNCLEAR LOW LOW LOW HIGH
Lo Giudice et al.158 2016 Open Dent J 6 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Loguercio et al.159 2015 Braz Oral Res 30 LOW LOW LOW LOW LOW LOW
Loyola-Rodriguez et al.160 2003 J Clin Pediatr Dent 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Luo et al.161 2007 J Dent 16 HIGH UNCLEAR UNCLEAR LOW LOW LOW
Machado et al.162 2013 Quintessence Int 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Machado et al.163 2016 Int J Periodontics Restorative Dent 16 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Maghaireh et al.164 2014 Oper Dent 16 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Marson et al.165 2008 Oper Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Martín et al.166 2015 J Dent 30 LOW UNCLEAR LOW LOW LOW LOW
Martins et al.167 2011 Rev Assoc Paul Cir Dent 12 LOW UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Matis et al.168 1998 Quintessence Int 15 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Matis et al.169 2000 Quintessence Int 17 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Matis et al.170 2002 Oper Dent 17 LOW UNCLEAR UNCLEAR UNCLEAR LOW LOW
Matis et al.171 2002 Quintessence Int 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Matis et al.172 2005 Oper Dent 15 UNCLEAR UNCLEAR LOW LOW UNCLEAR UNCLEAR
Matis et al.173 2006 Oper Dent 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Matis et al.174 2007 Oper Dent 11 UNCLEAR UNCLEAR LOW LOW UNCLEAR LOW
Matis et al.175 2009 Oper Dent 15 LOW UNCLEAR LOW LOW LOW LOW
Medeiros, de Lima176 2008 J Can Dent Assoc 17 LOW UNCLEAR UNCLEAR UNCLEAR LOW LOW
Mehta et al.177 2013 Eur J Oral Sci 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Meireles et al.178 2008 J Dent 22 LOW UNCLEAR LOW LOW LOW LOW
Meireles et al.179 2008 Oper Dent 21 LOW UNCLEAR LOW LOW LOW LOW
Meireles et al.180 2009 JADA 21 LOW UNCLEAR LOW LOW LOW LOW
Meireles et al.181 2010 J Dent 21 LOW UNCLEAR LOW LOW LOW LOW
Meireles et al.182 2014 J Dent 22 LOW UNCLEAR LOW LOW LOW LOW
Mena Serrano et al.58 2016 Oper Dent 30 LOW LOW LOW LOW LOW LOW
Miller et al.183 2000 Pract Proced Aesthet Dent 4 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR
Moghadam et al.184 2013 Eur J Dent 20 LOW UNCLEAR LOW LOW LOW LOW
Mohan et al.185 2008 J Dent 19 HIGH UNCLEAR LOW LOW LOW LOW
Mokhlis et al.186 2000 JADA 16 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Mondelli et al.187 2012 J Appl Oral Sci 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Montenegro-Arana et al.188 2016 Oper Dent 25 LOW LOW LOW UN LOW LOW
Morgan et al.189 2015 Br Dent J 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Myers et al.190 2003 J Esthet Restor Dent 14 LOW UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Nathoo et al.191 2001 Comp Cont Educ Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Nathoo et al.192 2003 J Clin Dent 17 HIGH UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH
Navarra et al.193 2014 Int J Dent Hyg 11 LOW LOW UNCLEAR UNCLEAR UNCLEAR HIGH
Nutter et al.194 2013 J Dent 14 LOW UNCLEAR UNCLEAR UNCLEAR LOW LOW
Ontiveros, Paravina195 2009 J Dent 13 LOW UNCLEAR LOW LOW LOW LOW
Palé et al.196 2014 Odontology 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Paphatanasiou et al.197 2001 Comp Cont Educ Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Paphatanasiou et al.198 2002 Comp Cont Educ Dent 17 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Perry et al.199 2013 Comp Cont Educ Dent 9 UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH LOW
Polydorou et al.200 2013 Oper Dent 15 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Posso Moreno et al.201 2010 Univ Odontol 15 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW HIGH
Reis et al.202 2011 Oper Dent 24 LOW LOW LOW LOW LOW LOW
Reis et al.203 2011 Oper Dent 24 LOW LOW LOW LOW LOW LOW
Reis et al.204 2013 Oper Dent 31 LOW LOW LOW LOW LOW LOW
Rezende et al.205 2014 Rev Assoc Paul Cir Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Rezende et al.206 2013 Oper Dent 23 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Rezende et al.207 2016 Oper Dent 25 UNCLEAR UNCLEAR UNCLEAR LOW LOW LOW
Rezende et al.61 2016 Oper Dent 30 LOW LOW LOW LOW LOW LOW
Rosenstiel et al.208 1996 Quintessence Int 11 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW HIGH
Santana et al.209 2014 Braz Dent Journal 24 UNCLEAR UNCLEAR LOW LOW LOW LOW
Shahidi et al.210 2005 J Clin Dent 17 HIGH UNCLEAR LOW LOW LOW LOW
Shanbhag et al.211 2013 J Contemp Dent Pract 14 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Sielski et al.212 2003 Comp Cont Educ Dent 18 HIGH UNCLEAR LOW LOW LOW HIGH
Silva et al.213 2012 Rev Odontol Bras Central 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH HIGH
Simon et al.214 2014 J Clin Dent 16 HIGH UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW
Soares et al.215 2006 Rev Odont UNESP 8 UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH LOW
Strobl et al.216 2010 Lasers Med Sci 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Sundfeld et al.217 2015 Indian J Dent Res 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Swift et al.218 1997 J Esthet Restor Dent 15 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Swift et al.219 1999 J Esthet Restor Dent 14 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Swift et al.220 2004 Comp Cont Educ Dent 18 UNCLEAR UNCLEAR LOW UNCLEAR LOW LOW
Swift et al.221 2009 J Dent 19 UNCLEAR UNCLEAR LOW LOW LOW LOW
Tavares et al.222 2003 JADA 19 LOW UNCLEAR LOW LOW LOW LOW
Tay et al.6 2009 JADA 24 LOW LOW LOW LOW LOW LOW
Tay et al.223 2012 Am J Dent 29 LOW LOW LOW LOW LOW LOW
Tsubura224 2010 Odontology 10 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Tsubura ,Yamaguchi225 2005 Odontology 12 UNCLEAR UNCLEAR UNCLEAR LOW HIGH LOW
Türkün et al.226 2010 J Esthet Restor Dent 12 UNCLEAR UNCLEAR UNCLEAR UNCLEAR HIGH LOW
Vano et al.227 2015 Int J Dent Hyg 24 UNCLEAR LOW UNCLEAR LOW LOW LOW
Ward, Felix228 2012 Comp Cont Educ Dent 13 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Wetter et al.229 2009 Lasers Med Sci 14 UNCLEAR UNCLEAR UNCLEAR UNCLEAR LOW LOW
Xu et al.230 2007 Am J Dent 17 UNCLEAR UNCLEAR LOW LOW LOW LOW
Yudhira et al.231 2007 Am J Dent 22 HIGH LOW LOW LOW LOW LOW
Zantner et al.232 2006 Quintessence Int 23 LOW UNCLEAR LOW LOW LOW LOW
Zekonis et al.233 2003 Oper Dent 18 LOW UNCLEAR UNCLEAR LOW LOW LOW
Zhao et al.234 2013 Quintessence Int 15 LOW LOW UNCLEAR UNCLEAR LOW LOW
Ziebolz et al.235 2007 Clin Oral Investig 18 HIGH UNCLEAR UNCLEAR UNCLEAR LOW LOW
Ziemba et al.236 2005 J Clin Dent 19 LOW LOW UNCLEAR UNCLEAR LOW LOW

Risk of bias of the included studies

Except for the selective outcome reporting and incomplete outcome data, most of the studies were judged to be at “unclear” or “high” risk of bias in the Cochrane Collaboration tool domains (Figure 4). Table 10 reports the individual risk of bias in each domain for all included studies. This table facilitates the analysis of the risk of bias within each study. Only 14 included studies (7.6%) were judged to be at “low” risk of bias in all domains; 115 studies were classified as at “unclear” risk of bias in at least one domain, resulting in 62.2% of the studies being classified at “unclear” risk of bias at the study level. The remaining 56 studies were classified as at “high” risk of bias in at least one domain, representing 30.3% of studies judged as at “high” risk of bias.

Figure 4 Methodological risk of bias chart. 

Discussion

Study compliance with the CONSORT

Although the CONSORT Statement has been misleadingly used as an instrument to evaluate the quality of the RCTs available in the literature,24 the aim of the CONSORT Statement is to guide authors to describe details on their studies to enable the evaluation of the risk of bias of RCTs.25 This is why adherence to CONSORT Statement is of ultimate importance so that readers can appraise the available literature and translate this literature into clinical knowledge pertinent to evidence-based practice. In the present study, we assessed the adherence of RCTs of bleaching materials and techniques to the CONSORT Statement. 26,27

In order to provide a better analysis of the compliance of the studies with each item of the CONSORT score, a 0–2 scale was developed in a way that zero means no reporting, 1 poor reporting, and 2 adequate reporting.22 This is different from what had been done in other papers, which have reported the adherence of RCTs in other dental areas, such as orthodontics, prosthodontics, oral implants, periodontics and pediatric dentistry.28,29,30,31,32,33 These earlier studies were more focused on the journal’s compliance rather than the article’s compliance with a specific subject. Subsequently, few of these earlier studies performed a comprehensive search review of the articles published in a specific research area, as we have tried to do in the present study. To the extent of the authors’ knowledge this is the first study that has attempted to evaluate the adherence of RCTs of bleaching materials and techniques to the CONSORT Statement, which was one of the aims of the present study.

To evaluate the risk of bias of the RCTs it is imperative that we concentrate on the design and the results of any study report. CONSORT adherence to introduction or discussion section increases the quality of the article reporting but does not affect the risk of bias of the studies. This is the reason behind our decision to only evaluate each study’s compliance with the items related to methodology and results. Earlier studies with the same aim, conducted on different specialties of dentistry, evaluated additional items, including the subjective items of introduction and discussion sections. 28,29,30,31,32,33

In the present study we observed that the overall CONSORT score for the included studies was 16.6 ± 5.3 points, which represents only 52.2% of the maximum CONSORT score a study could have reached. This reduced compliance with CONSORT Statement was also observed in an earlier study from our research group evaluating the compliance of RCTs in non-carious cervical lesions with the CONSORT.22 Similarly, other dental specialties such as periodontics and pediatric dentistry yielded similar results. For instance, a CONSORT compliance of approximately 60% was observed for RCTs in prosthodontics and implant dentistry. In orthodontics, this compliance ranged from 40 to 70%.28,29,30,34,35 Although these variations are small, they may reflect the inclusion criteria of the RCTs, the method of compliance evaluation, the number of CONSORT items evaluated, and also the period of publication. Our previous study of RCTs in non-carious cervical lesions demonstrated that the adherence of the study increases when the study is more recent.22

The results of the present study confirmed that the journal endorsement of the CONSORT Statement might positively influence the completeness of reporting of RCTs, mainly because three out of four journals with high average CONSORT score (J Dent, Clin Oral Investig, and JADA) have adopted this policy within the last decade. The same tendency has been observed for medical journals36 and for orthodontics journals,28,37 but not for RCTs conducted in non-carious cervical lesions.22 Braz Oral Res is another journal that clearly endorses the CONSORT Statement. Although there is an increasing number of journals endorsing the CONSORT Statement in medical journals as well as dental journals, the CONSORT compliance is still considered suboptimal even in these journals.38

Theoretically, one should expect that journals with high impact factor would publish studies with better reporting standards. Indeed, a significant correlation between journal impact factor and journal average CONSORT score was observed in the present and in earlier investigations,39,40 but this correlation is usually weak. In the present study the correlation coefficient (R2 = 0.1602) was also very weak, which means that the great variation observed in the average CONSORT score is not explained by the journal impact factor.

We hypothesize that not all members of the editorial board of these journals check the submitted articles for compliance with the CONSORT Statement, which prevents the journals from reaching an improved reporting score of RCTs. More attention to these items during the peer-review process may be required. Apart from that, the ambiguous language of what was meant by CONSORT endorsement25,41,42 in journals may prevent a better CONSORT adherence. In fact, instructions on how CONSORT should be used by authors are inconsistent across journals and publishers. For instance, J Dent recommends the use of CONSORT and submission of the checklist and flow diagram in the instructions for authors, while Clin Oral Investig does not recommend the use of reporting guidelines in the instructions.38 Publishers and journals should encourage authors to use CONSORT and set clear instructions for authors regarding full compliance with CONSORT. Braz Oral Res, for example, clearly indicates that authors must fully comply with the CONSORT Statement.

In regard to the period of time, better compliance was observed in more recent studies (2011–2016; mean CONSORT score of 19.0 ± 6.8) than in earlier periods (1996-2000; mean CONSORT score of 13.4 ± 4.0). This finding had been reported by other authors28,35 and in an earlier RCT study of adhesive materials applied onto non-carious cervical lesions.22 However, this increase is still small and substandard, as it reached slightly more than 50% of the maximum CONSORT score (32 points). Had all trials described the evaluated items correctly, the score might have been closer to 32.

Regarding the country, there is not a clear explanation why papers published by Brazilian researchers reached higher average CONSORT score than authors from more developed countries, such as USA, UK and Italy. We believe that the policies and efforts of Brazil government agencies in supporting training of specialized researchers in Science and Technology, implemented by Periódicos Capes Theses databases (www.capes.gov.br [Coordination of Personal Formation for Higher Education]) in the last 40 years, has led to an increasing number and quality of Brazilian articles in all science fields. Based on data from the SCImago database (www.scimagojr.com), the number of published papers in Dentistry is higher than those in other areas.43

As reported in the results section, the item sample size was reported poorly. This is also problematic in the medical field. For instance, Chan and Altman44 reported that 73% of the 519 medical trials indexed in PubMed in December 2000 did not report sample size calculation. Although sample size does not affect the validity of the study and its risk of bias, if not done properly and based on a clinically important effect, it may result in underpowered studies, which is usually misunderstood as groups being statistically similar. However, the lack of evidence to reject the null hypothesis does not mean that the groups are similar to one another. It may also mean that the study did not have a sample size big enough to detect a smaller difference if it really existed.

Based on the same premise, by using an infinite sample size we can prove any small and non-clinical relevant difference as being statistically different which may induce readers to change equivocally the standard protocol or technique for others that may be more costly or with higher side effects.45 This is why authors from RCTs should describe in their study the effect size rather than only the results of the hypothesis testing. Effect sizes and confidence intervals make the interpretation of the results easier. If a protocol has a fictitious relative risk for tooth sensitivity of 0.75 (95% CI 0.5 to 0.8), this means that the experimental group has a chance of 25% lower (from 50% to 20% lower) to develop tooth sensitivity. This response carries much more information than only stating that two groups were statistically different based on a probability value of 0.1%, for instance. Unfortunately, in the present study 88.1% of the studies did not report well, or did not report at all, the effect sizes, which is also a problem in medical journals.46

Based on these ideas, researchers are advised to move away from significance tests and to display, instead, an estimate of effect size delimited by confidence intervals. This method incorporates all the information normally included in a hypothesis, but in a way that emphasizes what is really important (clinical significance rather than statistical significance).46,47,48

Another concern in the included bleaching studies is related to randomization. Ideally, such description should include details about both the methods used to generate the random sequence, as well as the method used to conceal this the random sequence. Inadequately and unclearly concealed trials have been shown to result in exaggerated effect sizes in favor of the experimental group.49 This problem also occurs in other areas: poor reporting of allocation concealment was observed in 78% of the RCTs among dental journals50 and 93% in the specialty of periodontology.31 In the present study problems in random sequence generation and allocation concealment (scores 0 and 1) were seen in 53.5% and 84.8% of the trials, respectively.

These two items (random sequence and allocation concealment) allow readers to evaluate if the study is free of selection bias. A well-done random sequence generation is worthless if not well concealed. The objective of the randomization process is to balance the participants in terms of known and unknown factors so that no other variable apart from the one under investigation can account for the differences observed among participants from distinct groups.

Usually, authors refer to terms such as “random allocation” or “the groups were randomized”, without further elaboration. Authors should specify the method of sequence generation (such as a random-number table or a computerized random number generator, coin toss, dice throwing, etc.) as well as restrictions to the process such as stratification, block randomization, etc.45

Blinding is also a key element in RCT reporting and should not be confused with allocation concealment, as blinding prevents performance and detection bias45 instead of selection bias. In some research questions of bleaching studies, operator and patient blinding may be not possible, when for instance light activated systems are being tested. However, evaluator blinding may be always possible and it could be implemented in the study design, mainly if the primary outcome color change is being checked against a shade guide unit. In such case, lack of evaluator blindness would put the study at a higher risk of bias. However, for objective outcomes, such as color measurements with a spectrophotometer, the lack of examiner blindness is not that important. When the primary outcome is tooth sensitivity, which is a patient-centered subjective outcome, it is the lack of participants’ blinding and not evaluators’ that downgrade the level of confidence in the research findings.

Failures to describe who is blinded in the study are the most common problems observed in the eligible studies. Reports like “this study was single-blind”, “this was a double-blind study”, are useless, as they do not inform readers of who was in fact blinded. In agreement with these ideas, Pandis et al.50 reported that inadequate description of blinding in RCTs published in leading dental journals ranged from 74 to 100%. In implant dentistry, the lack of adequate blinding reporting was informed to be 58%.51

The design and conduct of some RCTs may be not straightforward, particularly when there are losses to follow-up, or exclusions. This precludes the description of the numbers of participants through each phase of the study in a few sentences.52 This can be simply described by introducing a flow chart with the number of participants in each phase of the trial. Although the CONSORT Statement recommends the inclusion of a flow chart, we observed that only 48.1% of the clinical trials followed this recommendation.

Another type of bias commonly found in RCTs is selective outcome reporting. In general, there is most enthusiasm about the publication of RCTs that show either a large effect of a new treatment (positive trials) or equivalence of two approaches. Consequently, articles with negative findings are less submitted or accepted for publication by journals. This may even be more relevant in sponsored RCTs if the results of the trial place financial interests at risk.53

To manage such problems, the International Committee of Medical Journal Editors (ICMJE) has proposed comprehensive trials registration. Trials must register at or before the onset of patient enrollment.53 For the ICMJE, this policy applies to any clinical trial that started enrollment after July 1, 2005. However, only 12 out of 120 included studies of this review published in 2005 or later performed trial registration (Table 5). Such earlier registration prevents selective reporting and reduces publication bias, two important issues that may downgrade the level of evidence of a randomized clinical trial.54 Some dental journals as J Dent, Oper Dent, and Braz Oral Res have added this indication as mandatory in their instructions for authors.

In regard to numbers analyzed, the number of participants per group in all analyzes should be clear. Reporting summary statistics without their spread over the mean or only percentages, relative risks, odds ratios is not enough as does not allow assessment of whether or not some of the randomly assigned participants were excluded from the analysis. The same should be applied to losses and exclusions. Along with the description of these figures per group, reasons for the losses and exclusions should be given as they may be related to the intervention. For instance, when a patient quits the treatment because another disease is requiring his/her attention, this is unlikely to be related to the intervention; but if a patient does not attend the recalls because he/she wants to be withdrawn from the trial, the reason may be related to side effects or lack of efficacy of the treatments under evaluation.

Baseline information was adequately reported in only 34% of the papers and it is important to check comparability at baseline. Any differences in baseline characteristics are, however, the result of chance rather than bias; the reason of why there is no need to perform hypothesis testing for these characteristics.55

For any item, when reporting data, authors should be careful. They should not display percentages instead of raw figures, as it is risky. Rounded percentages may be compatible with more than one numerator and if the authors fail to provide the total number of participants, the number of participants in the event under evaluation will be unclear. For instance, 90% may represent 1 out of 10 but also 100 out of 1000 – this makes a profound influence on the precision of the data. Merging data of groups can done as long as their individual data are also reported. Finally, summary statistics for continuous variables should be presented with their measure of spread; for dichotomous variables authors should describe the number of counts vs. total number of observations.22

The trial design involves the description of type of the trial (parallel, cross-over, factorial, split-mouth and or multiple restorations); the conceptual framework (superiority, non-inferiority or equivalence trial) and also the allocation ratio (example 1:1 or 1:2).20 The settings (where and when the study was performed) are also essential to place the study in historical context and to evaluate its external validity (generalization of the findings to other populations).

Risk of bias

Although incomplete outcome data and selective reporting were poorly described, this occurred in small percentage of the studies. In all other domains of the Cochrane Collaboration risk of bias tool, most the RCTs were judged to be at “unclear” or at “high” risk of bias. The implications of inadequate sequence generation, allocation concealment and examiner blinding were already discussed in details.

At the study level, only 7.57% of the studies were considered to be at low risk of bias, which means being low risk of bias in all domains. The remaining studies were at unclear or high risk of bias. This is worrying since our treatment decisions are being based on studies that do not have a rigorous methodology and therefore they may lead to biased results.

Final remarks

Although CONSORT guidelines have been included in the instructions for authors of some journals, active compliance is far from being achieved. Perhaps, the inclusion of additional subheadings, as suggested by Kloukos et al.29 might result in better compliance with the CONSORT Statement. The results of the present study indicate that adherence of RCTs of bleaching systems to the CONSORT Statement requires improvements. Adherence to the CONSORT Statement will also make readers to rethink their methodology and ultimately reduce the high risk of bias of studies in the field.

There are some limitations in the present study. Although a very comprehensive search in terms of different databases with specific vocabulary and keywords were performed, we may have missed some articles in the search.

Nevertheless, looking at Table 4, the higher numbers of the papers were produced in USA and Brazil and the majority of them were published in English language journals. Only a few papers were published in Portuguese or Spanish (10 in total). Also, as mentioned in the results section, only one paper was excluded due to language. These details make us confident in the results herein presented. Although other studies on the field may not be cited here they are unlikely to change the results herein presented.

Acknowledgments

The authors would like to thanks to Mr. Amelia Falcone, Brand Manager from Compendium for kindly provide us some papers from the Compendium Continuing Education in Dentistry including in this review. This study was partially supported by CAPES and National Council for Scientific and Technological Development (CNPq) under grants 304104/2013-9 and 305588/2014-1.

References

1. Al-Zarea BK. Satisfaction with appearance and the desired treatment to improve aesthetics. Int J Dent. 2013;2013:ID912368. http://dx.doi.org/10.1155/2013/912368Links ]

2. Akarslan ZZ, Sadik B, Erten H, Karabulut E. Dental esthetic satisfaction, received and desired dental treatments for improvement of esthetics. Indian J Dent Res. 2009;20(2):195-200. https://doi.org/10.4103/0970-9290.52902Links ]

3. Fernández E, Bersezio C, Bottner J, Avalos F, Godoy I, Inda D et al. Longevity, esthetic perception, and psychosocial impact of teeth bleaching by low (6%) hydrogen peroxide concentration for in-office treatment: a randomized clinical trial. Oper Dent. 2017;42(1):41-52. https://doi.org/10.2341/15-335-CLinks ]

4. Geus JL, de Lara MB, Hanzen TA, Fernández E, Loguercio AD, Kossatz S et al. One-year follow-up of at-home bleaching in smokers before and after dental prophylaxis. J Dent. 2015;43(11):1346-51. https://doi.org/10.1016/j.jdent.2015.08.009Links ]

5. Moncada G, Sepúlveda D, Elphick K, Contente M, Estay J, Bahamondes V, et al. Effects of light activation, agent concentration, and tooth thickness on dental sensitivity after bleaching. Oper Dent. 2013;38(5):467-76. https://doi.org/10.2341/12-335-CLinks ]

6. Tay LY, Kose C, Loguercio AD, Reis A. Assessing the effect of a desensitizing agent used before in-office tooth bleaching. J Am Dent Assoc. 2009;140(10):1245-51. https://doi.org/10.14219/jada.archive.2009.0047Links ]

7. Kina JF, Huck C, Riehl H, Martinez TC, Sacono NT, Ribeiro AP, et al. Response of human pulps after professionally applied vital tooth bleaching. Int Endod J. 2010;43(7):572-80. https://doi.org/10.1111/j.1365-2591.2010.01713.xLinks ]

8. Soares DG, Basso FG, Hebling J, de Souza Costa CA. Concentrations of and application protocols for hydrogen peroxide bleaching gels: effects on pulp cell viability and whitening efficacy. J Dent. 2014;42(2):185-98. https://doi.org/10.1016/j.jdent.2013.10.021Links ]

9. Soares DG, Basso FG, Pontes EC, Garcia LF, Hebling J, Costa CAS. Effective tooth-bleaching protocols capable of reducing H2O2 diffusion through enamel and dentine. J Dent. 2014;42(3):351-8. https://doi.org/10.1016/j.jdent.2013.09.001Links ]

10. Hanks CT, Fat JC, Wataha JC, Corcoran JF. Cytotoxicity and dentin permeability of carbamide peroxide and hydrogen peroxide vital bleaching materials, in vitro. J Dent Res. 1993;72(5):931-8. https://doi.org/10.1177/00220345930720051501Links ]

11. Roderjan DA, Stanislawczuk R, Hebling J, Costa CA, Reis A, Loguercio AD. Response of human pulps to different in-office bleaching techniques: preliminary findings. Braz Dent J. 2015;26(3):242-8. https://doi.org/10.1590/0103-6440201302282Links ]

12. Paula EA, Kossatz S, Fernandes D, Loguercio AD, Reis A. Administration of ascorbic acid to prevent bleaching-induced tooth sensitivity: a randomized triple-blind clinical trial. Oper Dent. 2014;39(2):128-35. https://doi.org/10.2341/12-483-CLinks ]

13. Gomes RS, Souza FBd, Lacerda CM, Brambilla CFF, Pascotto RC. Avaliação clínica da eficiência do uso do sistema LED-laser, LED e luz halógena na ativação do agente clareador em dentes vitalizados. Rev Dental Press Estét. 2008;5(2):62-77. [ Links ]

14. Mena-Serrano AP, Parreiras SO, Nascimento EM, Borges CP, Berger SB, Loguercio AD et al. Effects of the concentration and composition of in-office bleaching gels on hydrogen peroxide penetration into the pulp chamber. Oper Dent. 2015;40(2):E76-82. https://doi.org/10.2341/13-352-LLinks ]

15. Rezende M, Loguercio AD, Kossatz S, Reis A. Predictive factors on the efficacy and risk/intensity of tooth sensitivity of dental bleaching: a multi regression and logistic analysis. J Dent. 2016;45:1-6. https://doi.org/10.1016/j.jdent.2015.11.003Links ]

16. Burns PB, Rohrich RJ, Chung KC. The levels of evidence and their role in evidence-based medicine. Plast Reconstr Surg. 2011;128(1):305-10. https://doi.org/10.1097/PRS.0b013e318219c171Links ]

17. Jüni P, Altman DG, Egger M. Systematic reviews in health care: assessing the quality of controlled clinical trials. BMJ. 2001;323(7303):42-6. https://doi.org/10.1136/bmj.323.7303.42Links ]

18. Schulz KF, Grimes DA. Allocation concealment in randomised trials: defending against deciphering. Lancet. 2002;359(9306):614-8. https://doi.org/10.1016/S0140-6736(02)07750-4Links ]

19. Rennie D. CONSORT revised: improving the reporting of randomized trials. JAMA. 2001;285(15):2006-7. https://doi.org/10.1001/jama.285.15.2006Links ]

20. Schulz KF, Altman DG, Moher D, Group C. CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials. BMC Med. 2010;8(1):18. https://doi.org/10.1186/1741-7015-8-18Links ]

21. Moher D, Hopewell S, Schulz KF, Montori V, Gøtzsche PC, Devereaux PJ et al. CONSORT 2010 Explanation and elaboration: updated guidelines for reporting parallel group randomised trials. BMJ. 2010:340. https://doi.org/10.1136/bmj.c869Links ]

22. Reis A, Wambier L, Schroeder M. Compliance of randomized clinical trials in non-carious cervical lesions with the CONSORT Statement: a methodology systematic review. Oper Dent. 2017. [ Links ]

23. Higgins JP, Altman DG, Gøtzsche PC, Jüni P, Moher D, Oxman AD et al. The Cochrane collaboration’s tool for assessing risk of bias in randomised trials. BMJ. 2011;343:d5928. https://doi.org/10.1136/bmj.d5928Links ]

24. Cioffi I, Farella M. Quality of randomised controlled trials in dentistry. Int Dent J. 2011;61(1):37-42. https://doi.org/10.1111/j.1875-595X.2011.00007.xLinks ]

25. Shamseer L, Sampson M, Bukutu C, Schmid CH, Nikles J, Tate R et al. CONSORT extension for reporting N-of-1 trials (CENT) 2015: explanation and elaboration. J Clin Epidemiol. 2016;76:18-46. https://doi.org/10.1016/j.jclinepi.2015.05.018Links ]

26. Moher D, Hopewell S, Schulz KF, Montori V, Gøtzsche PC, Devereaux PJ et al. CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. J Clin Epidemiol. 2010;63(8):e1-37. https://doi.org/10.1016/j.jclinepi.2010.03.004Links ]

27. Schulz KF, Altman DG, Moher D, Group C. CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials. Trials. 2010;11(1):32. https://doi.org/10.1186/1745-6215-11-32Links ]

28. Flint HE, Harrison JE. How well do reports of clinical trials in the orthodontic literature comply with the CONSORT statement? J Orthod. 2010;37(4):250-61. https://doi.org/10.1179/14653121043191Links ]

29. Kloukos D, Papageorgiou SN, Doulis I, Petridis H, Pandis N. Reporting quality of randomised controlled trials published in prosthodontic and implantology journals. J Oral Rehabil. 2015;42(12):914-25. https://doi.org/10.1111/joor.12325Links ]

30. Lempesi E, Koletsi D, Fleming PS, Pandis N. The reporting quality of randomized controlled trials in orthodontics. J Evid Based Dent Pract. 2014;14(2):46-52. https://doi.org/10.1016/j.jebdp.2013.12.001Links ]

31. Montenegro R, Needleman I, Moles D, Tonetti M. Quality of RCTs in periodontology: a systematic review. J Dent Res. 2002;81(12):866-70. https://doi.org/10.1177/154405910208101214Links ]

32. Papageorgiou SN, Kloukos D, Petridis H, Pandis N. An assessment of the risk of bias in randomized controlled trial reports published in Prosthodontic and Implant Dentistry Journals. Int J Prosthodont. 2015;28(6):586-93. https://doi.org/10.11607/ijp.4357Links ]

33. Rajasekharan S, Vandenbulcke J, Martens L. An assessment of the quality of reporting randomised controlled trials published in paediatric dentistry journals. Eur Arch Paediatr Dent. 2015;16(2):181-9. https://doi.org/10.1007/s40368-014-0153-9Links ]

34. Acosta Gómez AP, Henao Giraldo GM, Henao Arango LG. Peróxido de hidrógeno al 35 por ciento y peróxido de carbamida al 10 por ciento para el blanqueamiento dental. Univ Odontol. 1999;19(39):14-20. [ Links ]

35. Bearn DR, Alharbi F. Reporting of clinical trials in the orthodontic literature from 2008 to 2012: observational study of published reports in four major journals. J Orthod. 2015;42(3):186-91. https://doi.org/10.1179/1465313315Y.0000000011Links ]

36. Turner L, Shamseer L, Altman DG, Weeks L, Peters J, Kober T et al. Consolidated standards of reporting trials (CONSORT) and the completeness of reporting of randomised controlled trials (RCTs) published in medical journals. Cochrane Database Syst Rev. 2012;11:MR000030. https://doi.org/10.1002/14651858.MR000030.pub2Links ]

37. Pandis N, Shamseer L, Kokich VG, Fleming PS, Moher D. Active implementation strategy of CONSORT adherence by a dental specialty journal improved randomized clinical trial reporting. J Clin Epidemiol. 2014;67(9):1044-8. https://doi.org/10.1016/j.jclinepi.2014.04.001Links ]

38. Sarkis-Onofre R, Poletto-Neto V, Cenci MS, Pereira-Cenci T, Moher D. Impact of the CONSORT Statement endorsement in the completeness of reporting of randomized clinical trials in restorative dentistry. J Dent. 2017;58:54-9. https://doi.org/10.1016/j.jdent.2017.01.009Links ]

39. Barbui C, Cipriani A, Malvini L, Tansella M. Validity of the impact factor of journals as a measure of randomized controlled trial quality. J Clin Psychiatry. 2006;67(1):37-40. https://doi.org/10.4088/JCP.v67n0106Links ]

40. Sjögren P, Halling A. Quality of reporting randomised clinical trials in dental and medical research. Br Dent J. 2002;192(2):100-3. https://doi.org/10.1038/sj.bdj.4801304Links ]

41. Altman DG. Endorsement of the CONSORT statement by high impact medical journals: survey of instructions for authors. BMJ. 2005;330(7499):1056-7. https://doi.org/10.1136/bmj.330.7499.1056Links ]

42. Hopewell S, Altman DG, Moher D, Schulz KF. Endorsement of the CONSORT Statement by high impact factor medical journals: a survey of journal editors and journal “Instructions to Authors”. Trials. 2008;9(1):20. https://doi.org/10.1186/1745-6215-9-20Links ]

43. SCImago. SJR: SCImago journal & country rank. 2015[acess 2017 Feb 10]. Available from: http://www.scimagojr.comLinks ]

44. Chan AW, Altman DG. Epidemiology and reporting of randomised trials published in PubMed journals. Lancet. 2005;365(9465):1159-62. https://doi.org/10.1016/S0140-6736(05)71879-1Links ]

45. Higgins JP, Green, S. Cochrane handbook for systematic reviews of interventions. Chichester: Wiley-Blackwell; 2014. [ Links ]

46. Pocock SJ, Hughes MD, Lee RJ. Statistical problems in the reporting of clinical trials. A survey of three medical journals. N Engl J Med. 1987;317(7):426-32. https://doi.org/10.1056/NEJM198708133170706Links ]

47. Borenstein M. Hypothesis testing and effect size estimation in clinical trials. Ann Allergy Asthma Immunol. 1997;78(1):5-11. https://doi.org/10.1016/S1081-1206(10)63363-7Links ]

48. Houle TT, Stump DA. Statistical significance versus clinical significance. Semin Cardiothorac Vasc Anesth. 2008;12(1):5-6. https://doi.org/10.1177/1089253208316440Links ]

49. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA. 1995;273(5):408-12. https://doi.org/10.1001/jama.1995.03520290060030Links ]

50. Pandis N, Polychronopoulou A, Eliades T. An assessment of quality characteristics of randomised control trials published in dental journals. J Dent. 2010;38(9):713-21. https://doi.org/10.1016/j.jdent.2010.05.014Links ]

51. Cairo F, Sanz I, Matesanz P, Nieri M, Pagliaro U. Quality of reporting of randomized clinical trials in implant dentistry: a systematic review on critical aspects in design, outcome assessment and clinical relevance. J Clin Periodontol. 2012;39 Suppl 12:81-107. https://doi.org/10.1111/j.1600-051X.2011.01839.xLinks ]

52. Egger M, Jüni P, Bartlett C. Value of flow diagrams in reports of randomized controlled trials. JAMA. 2001;285(15):1996-9. https://doi.org/10.1001/jama.285.15.1996Links ]

53. De Angelis C, Drazen JM, Frizelle FA, Haug C, Hoey J, Horton R et al. Clinical trial registration: a statement from the International Committee of Medical Journal Editors. Lancet. 2004;364(9438):911-2. https://doi.org/10.1016/S0140-6736(04)17034-7Links ]

54. Guyatt GH, Oxman AD, Schünemann HJ, Tugwell P, Knottnerus A. GRADE guidelines: a new series of articles in the Journal of Clinical Epidemiology. J Clin Epidemiol. 2011;64(4):380-2. https://doi.org/10.1016/j.jclinepi.2010.09.011Links ]

55. Oginni AO, Adeleke AA. Comparison of pattern of failure of resin composite restorations in non-carious cervical lesions with and without occlusal wear facets. J Dent. 2014;42(7):824-30. https://doi.org/10.1016/j.jdent.2014.04.003Links ]

56. Correa AC, Santana TR, Nahsan FP, Loguercio AD, Faria-E-Silva AL. The Impact of a customized tray on in-office bleaching tooth sensitivity: a randomized clinical trial. Oper Dent. 2016;41(1):15-22. https://doi.org/10.2341/15-029-CLinks ]

57. Rezende M, Bonafé E, Vochikovski L, Farago PV, Loguercio AD, Reis A, et al. Pre- and postoperative dexamethasone does not reduce bleaching-induced tooth sensitivity: A randomized, triple-masked clinical trial. J Am Dent Assoc. 2016;147(1):41-9. https://doi.org/10.1016/j.adaj.2015.07.003Links ]

58. Mena-Serrano AP, Garcia E, Luque-Martinez I, Grande R, Loguercio AD, Reis A. A single-blind randomized trial about the effect of hydrogen peroxide concentration on light-activated bleaching. Oper Dent. 2016;41(5):455-64. https://doi.org/10.2341/15-077-CLinks ]

59. Paula EA, Nava JA, Rosso C, Benazzi CM, Fernandes KT, Kossatz S, et al. In-office bleaching with a two- and seven-day intervals between clinical sessions: A randomized clinical trial on tooth sensitivity. J Dent. 2015;43(4):424-9. https://doi.org/10.1016/j.jdent.2014.09.009Links ]

60. Geus JL, Bersezio C, Urrutia J, Yamada T, Fernández E, Loguercio AD, et al. Effectiveness of and tooth sensitivity with at-home bleaching in smokers: a multicenter clinical trial. J Am Dent Assoc. 2015;146(4):233-40. https://doi.org/10.1016/j.adaj.2014.12.014Links ]

61. Rezende M, Ferri L, Kossatz S, Loguercio AD, Reis A. Combined bleaching technique using low and high hydrogen peroxide in-office bleaching gel. Oper Dent. 2016;41(4):388-96. https://doi.org/10.2341/15-266-CLinks ]

62. Kose C, Calixto AL, Bauer JR, Reis A, Loguercio AD. Comparison of the effects of in-office bleaching times on whitening and tooth sensitivity: a single blind, randomized clinical trial. Oper Dent. 2016;41(2):138-45. https://doi.org/10.2341/15-085-CLinks ]

63. Paula EA, Loguercio AD, Fernandes D, Kossatz S, Reis A. Perioperative use of an anti-inflammatory drug on tooth sensitivity caused by in-office bleaching: a randomized, triple-blind clinical trial. Clin Oral Investig. 2013;17(9):2091-7. https://doi.org/10.1007/s00784-013-0918-2Links ]

64. Geus JL, Rezende M, Margraf LS, Bortoluzzi MC, Fernández E, Loguercio AD, et al. Evaluation of genotoxicity and efficacy of at-home bleaching in smokers: a single-blind controlled clinical trial. Oper Dent. 2015;40(2):E47-55. https://doi.org/10.2341/14-121-CLinks ]

65. Al Shethri S, Matis BA, Cochran MA, Zekonis R, Stropes M. A clinical evaluation of two in-office bleaching products. Oper Dent. 2003;28(5):488-95. [ Links ]

66. Almeida LCA, Riehl H, Santos PH, Sundfeld MLMM, Briso ALF. Clinical evaluation of the effectiveness of different bleaching therapies in vital teeth. Int J Periodontics Restorative Dent. 2012;32(3):303-9. https://doi.org/10.1038/sj.bdj.2012.587Links ]

67. Alomari Q, El Daraa E. A randomized clinical trial of in-office dental bleaching with or without light activation. J Contemp Dent Pract. 2010;11(1):E017-24. [ Links ]

68. Alonso de la Peña V, Balboa Cabrita O. Comparison of the clinical efficacy and safety of carbamide peroxide and hydrogen peroxide in at-home bleaching gels. Quintessence international. 2006;37(7):551-6. [ Links ]

69. Alonso de la Peña V, López Ratón M. Randomized clinical trial on the efficacy and safety of four professional at-home tooth whitening gels. Oper Dent. 2014;39(2):136-43. https://doi.org/10.2341/12-402-CLinks ]

70. Auschill T, Hellwig E, Schmidale S, Sculean A, Arweiler NB. Efficacy, side-effects and patients’ acceptance of different bleaching techniques (OTC, in-office, at-home). Oper Dent. 2005;30(2):156-63. [ Links ]

71. Auschill TM, Schneider-Del Savio T, Hellwig E, Arweiler NB. Randomized clinical trial of the efficacy, tolerability, and long-term color stability of two bleaching techniques: 18-month follow-up. Quintessence Int. 2012;43(8):683-94. [ Links ]

72. Barlow A, Gerlach RW, Date RF, Brennan K, Struzycka I, Kwiatkowska A. Clinical response of two brush-applied peroxide whitening systems. J Clin Dent. 2002;14(3):59-63. [ Links ]

73. Barnes DM, Kihn PW, Romberg E, George D, DePaola L, Medina E. Clinical evaluation of a new 10% carbamide peroxide tooth-whitening agent. Compend Contin Educ Dent. 1998;19(10):968-80. [ Links ]

74. Basting RT, Amaral FL, França FM, Flório FM. Clinical comparative study of the effectiveness of and tooth sensitivity to 10% and 20% carbamide peroxide home-use and 35% and 38% hydrogen peroxide in-office bleaching materials containing desensitizing agents. Oper Dent. 2012;37(5):464-73. https://doi.org/10.2341/11-337-CLinks ]

75. Berga-Caballero A, Forner-Navarro L, Amengual-Lorenzo J. At-home vital bleaching: a comparison of hydrogen peroxide and carbamide peroxide treatments. Med Oral Patol Oral Cir Bucal. 2006;11(1):E94-9. [ Links ]

76. Bernardon JK, Sartori N, Ballarin A, Perdigão J, Lopes GC, Baratieri LN. Clinical performance of vital bleaching techniques. Oper Dent. 2010;35(1):3-10. https://doi.org/10.2341/09-008CRLinks ]

77. Bernardon JK, Ferrari P, Baratieri LN, Rauber GB. Comparison of treatment time versus patient satisfaction in at-home and in-office tooth bleaching therapy. J Prosthet Dent. 2015;114(6):826-30. https://doi.org/10.1016/j.prosdent.2015.05.014Links ]

78. Bernardon JK, Vieira Martins M, Branco Rauber G, Monteiro Junior S, Baratieri LN. Clinical evaluation of different desensitizing agents in home-bleaching gels. J Prosthet Dent. 2016;115(6):692-6. https://doi.org/10.1016/j.prosdent.2015.10.020Links ]

79. Bizhang M, Müller M, Phark JH, Barker ML, Gerlach RW. Clinical trial of long-term color stability of hydrogen peroxide strips and sodium percarbonate film. Am J Dent. 2007;20 Spec No A:23-7A. [ Links ]

80. Bizhang M, Chun YH, Damerau K, Singh P, Raab WH, Zimmer S. Comparative clinical study of the effectiveness of three different bleaching methods. Oper Dent. 2009;34(6):635-41. https://doi.org/10.2341/08-069-CLinks ]

81. Bonafé E, Loguercio AD, Reis A, Kossatz S. Effectiveness of a desensitizing agent before in-office tooth bleaching in restored teeth. Clin Oral Investig. 2014;18(3):839-45. https://doi.org/10.1007/s00784-013-1055-7Links ]

82. Bortolatto JF, Trevisan TC, Bernardi PS, Fernandez E, Dovigo LN, Loguercio AD, et al. A novel approach for in-office tooth bleaching with 6% H2O2/TiO_N and LED/laser system-a controlled, triple-blinded, randomized clinical trial. Lasers Med Sci. 2016;31(3):437-44. https://doi.org/10.1007/s10103-016-1866-2Links ]

83. Braun A, Jepsen S, Krause F. Spectrophotometric and visual evaluation of vital tooth bleaching employing different carbamide peroxide concentrations. Dent Mat. 2007;23(2):165-9. https://doi.org/10.1016/j.dental.2006.01.017Links ]

84. Browning WD, Cho SD, Deschepper EJ. Effect of a nano-hydroxyapatite paste on bleaching-related tooth sensitivity J Esthet Restor Dent. 2012;24(4):268-76. https://doi.org/10.1111/j.1708-8240.2011.00437.xLinks ]

85. Browning WD, Chan DC, Myers ML, Brackett WW, Brackett MG, Pashley DH. Comparison of traditional and low sensitivity whiteners. Oper Dent. 2008;33(4):379-85. https://doi.org/10.2341/07-134Links ]

86. Bruhn AM, Darby ML, McCombs GB, Lynch CM. Vital tooth whitening effects on oral health- related quality of life in older adults. J Dent Hyg. 2012;86(3):239-47. [ Links ]

87. Callan RS, Browning WD, Downey MC, Brackett MG. Comparison of two low sensitivity whiteners. Am J Dent. 2008;21(1):17-20. [ Links ]

88. Cardoso PC, Reis A, Loguercio A, Vieira LC, Baratieri LN. Clinical effectiveness and tooth sensitivity associated with different bleaching times for a 10 percent carbamide peroxide gel. J Am Dent Assoc. 2010;141(10):1213-20. https://doi.org/10.14219/jada.archive.2010.0048Links ]

89. Carvalho BCF, Leite RCSR, Ferreira MB, Carvalho EMOF. Avaliação da sensibilidade dentinária e manutenção da cor após clareamento. Rev Assoc Paul Cir Dent. 2006;59(1):45-8. [ Links ]

90. Cerqueira RR, Hofstaetter FL, Rezende M, Martins GC, Loguercio AD, Reis A et al. Efeito do uso de agente dessensibilizante na efetividade do clareamento e na sensibilidade dental. Rev Assoc Paul Cir Dent. 2013;67(1):64-7. [ Links ]

91. Cibirka RM, Myers M, Downey MC, Nelson SK, Browning WD, Hawkins IK, et al. Clinical study of tooth shade lightening from dentist-supervised, patient-applied treatment with two 10% carbamide peroxide gels. J Esthet Dent. 1999;11(6):325-31. https://doi.org/10.1111/j.1708-8240.1999.tb00415.xLinks ]

92. Collins LZ, Maggio B, Gallagher A, York M, Schäfer F. Safety evaluation of a novel whitening gel, containing 6% hydrogen peroxide and a commercially available whitening gel containing 18% carbamide peroxide in an exaggerated use clinical study. J Dent. 2004;32 Suppl 1:47-50. https://doi.org/10.1016/j.jdent.2003.10.014Links ]

93. Corbella S, Basso M, Roci E, De Siena F, Francetti L. Sbiancamento dentale domiciliare e ambulatoriale a confronto. Dent Cadmos 2009;77(7). [ Links ]

94. Cronin M, Charles C, Zhao Q, Dembling W. Comparison of two over-the-counter tooth whitening products using a novel system. Compend Contin Educ Dent.. 2005;26(2):140. [ Links ]

95. Costa JB, McPharlin R, Paravina RD, Ferracane JL. Comparison of at-home and in-office tooth whitening using a novel shade guide. Oper Dent. 2010;35(4):381-8. https://doi.org/10.2341/09-344-CLinks ]

96. Costa J, Lubisich E, Ferracane J, Hilton T. Comparison of efficacy of an in-office whitening system used with and without a whitening priming agent. J Esthet Restor Dent.. 2011;23(2):97-104. https://doi.org/10.1111/j.1708-8240.2010.00400.xLinks ]

97. Dawson PF, Sharif MO, Smith AB, Brunton PA. A clinical study comparing the efficacy and sensitivity of home vs combined whitening. Oper Dent. 2011;36(5):460-6. https://doi.org/10.2341/10-159-CLinks ]

98. Farhat PBA, Santos FA, Gomes JC, Gomes OM. Evaluation of the efficacy of LED-laser treatment and control of tooth sensitivity during in-office bleaching procedures. Photomed Laser Surg. 2014;32(7):422-6. https://doi.org/10.1089/pho.2014.3729Links ]

99. Freitas PM, Menezes AN, da Mota AC, Simoes A, Mendes FM, Lago AD, et al. Does the hybrid light source (LED/laser) influence temperature variation on the enamel surface during 35% hydrogen peroxide bleaching? A randomized clinical trial. Quintessence Int. 2016;47(1):61-73. https://doi.org/10.3290/j.qi.a34454. [ Links ]

100. Geus JL, Bersezio C, Urrutia J, Yamada T, Fernandez E, Loguercio AD et al. Effectiveness of and tooth sensitivity with at-home bleaching in smokers: a multicenter clinical trial. J Am Dent Assoc. 2015;146(4):233-40. 10.1016/j.adaj.2014.12.014Links ]

101. Delgado E, Hernández-Cott PL, Stewart B, Collins M, De Vizio W. Tooth-whitening efficacy of custom tray-delivered 9% hydrogen peroxide and 20% carbamide peroxide during daytime use: a 14-day clinical trial. P R Health Sci J. 2007;26(4):367-72. [ Links ]

102. Deliperi S, Bardwell DN, Papathanasiou A. Clinical evaluation of a combined in-office and take-home bleaching system. J Am Dent Assoc. 2004;135(5):628-34. https://doi.org/10.14219/jada.archive.2004.0252Links ]

103. Donly KJ, Donly AS, Baharloo L, Rojas-Candelas E, Garcia-Godoy F, Zhou X et al. Tooth whitening in children. Compend Contin Educ Dent. 2002;23(1A):22-8. [ Links ]

104. Donly KJ, Kennedy P, Segura A, Gerlach RW. Effectiveness and safety of tooth bleaching in teenagers. Pediatr Dent. 2005;27(4):298-302. [ Links ]

105. Donly K, Henson T, Jamison D, Gerlach R. Clinical trial evaluating two peroxide whitening strips used by teenagers. Gen Dent. 2006;54(2):110-2. [ Links ]

106. Donly KJ, Segura A, Henson T, Barker ML, Gerlach RW. Randomized controlled trial of professional at-home tooth whitening in teenagers. Gen Dent. 2007;55(7):669-74. [ Links ]

107. Donly KJ, Segura A, Sasa I, Perez E, Anastasia MK, Farrell S. A controlled clinical trial to evaluate the safety and whitening efficacy of a 9.5% hydrogen peroxide high-adhesion whitening strip in a teen population. Am J Dent. 2010;23(5):292-6. [ Links ]

108. Farrell S, Barker ML, Sagel PA, Gerlach RW. Use of a physical barrier to improve efficacy of a paint-on whitening gel: a seven-day randomized clinical trial. J Clin Dent. 2005;17(5):117-21. [ Links ]

109. Fernández E. Efficacy and tooth sensitivity of at-home bleaching in smokers: a two-center clinical trial. J Am Dent Assoc. 2015;146(4):233. [ Links ]

110. Ferrari M, Kugel G, Cagidiaco MC, Barker ML, Gerlach RW. Clinical trial evaluating the peroxide concentration response of whitening strips over 28 days. Am J Dent. 2004;17(4):291-4. [ Links ]

111. Gallagher A, Maggio B, Bowman J, Borden L, Mason S, Felix H. Clinical study to compare two in-office (chairside) whitening systems. J Clin Dent. 2001;13(6):219-24. [ Links ]

112. Gallo JR, Burgess JO, Ripps AH, Bell MJ, Mercante DE, Davidson JM. Evaluation of 30% carbamide peroxide at-home bleaching gels with and without potassium nitrate: a pilot study. Quintessence Int. 2009;40(4):e1-6. [ Links ]

113. Garcia-Godoy F, Villalta P, Barker M, Gerlach R. Placebo-controlled, 6-week clinical trial on the safety and efficacy of a low-gel, 14% hydrogen-peroxide whitening strip. Compend Contin Educ Dent. 2004;25(8 Suppl 2):21-6. [ Links ]

114. Gerlach R, Gibb R, Sagel P. A randomized clinical trial comparing a novel 5.3 percent hydrogen peroxide whitening strip to 10 percent, 15 percent, and 20 percent carbamide peroxide tray-based bleaching systems. Compend Contin Educ Dent. 2000;29(supplement):S22-8. [ Links ]

115. Gerlach RW, Barker ML, Sagel PA. Comparative efficacy and tolerability of two direct-to-consumer tooth whitening systems. Am J Dent. 2001;14(5):267-72. [ Links ]

116. Gerlach RW, Zhou X. Comparative clinical efficacy of two professional bleaching systems. Compend Contin Educ Dent. 2002;23(1A):35-41. [ Links ]

117. Gerlach RW, Sagel PA, Barker ML, Karpinia KA, Magnusson I. Placebo-controlled clinical trial evaluating a 10% hydrogen peroxide whitening strip. J Clin Dent. 2003;15(4):118-22. [ Links ]

118. Gerlach RW, Zhou X, McClanahan SF. Comparative response of whitening strips to a low peroxide and potassium nitrate bleaching gel. Am J Dent. 2002;15(Spec No):19-23A. [ Links ]

119. Gerlach RW, Barker ML. Randomized clinical trial comparing overnight use of two self-directed peroxide tooth whiteners. Am J Dent. 2003;16(Spec No)17-21B. [ Links ]

120. Gerlach RW, Sagel PA. Vital bleaching with a thin peroxide gel: the safety and efficacy of a professional-strength hydrogen peroxide whitening strip. J Am Dent Assoc. 2004;135(1):98-100. [ Links ]

121. Gerlach RW. Clinical trial comparing two daytime hydrogen-peroxide professional vital-bleaching systems. Compend Contin Educ Dent. 2004;25(8 Suppl 2):33-40. [ Links ]

122. Giachetti L, Bertini F, Bambi C, Nieri M, Scaminaci Russo D. A randomized clinical trial comparing at-home and in-office tooth whitening techniques: a nine-month follow-up. J Am Dent Assoc. 2010;141(11):1357-64. https://doi.org/10.14219/jada.archive.2010.0081Links ]

123. Giniger M, Spaid M, MacDonald J, Felix H. A 180-day clinical investigation of the tooth whitening efficacy of a bleaching gel with added amorphous calcium phosphate. J Clin Dent. 2005;16(1):11-6. [ Links ]

124. Giniger M, MacDonald J, Ziemba S, Felix H. The clinical performance of professionally dispensed bleaching gel with added amorphous calcium phosphate. J Am Dent Assoc. 2005;136(3):383-92. https://doi.org/10.14219/jada.archive.2005.0181Links ]

125. Goodson JM, Tavares M, Sweeney M, Stultz J, Newman M, Smith V et al. Tooth whitening: tooth color changes following treatment by peroxide and light. The J Clin Dent. 2005;16(3):78-82. [ Links ]

126. Grobler SR, Majeed A, Hayward R, Rossouw RJ, Moola MH, WKTJ. A clinical study of the effectiveness of two different 10% carbamide peroxide bleaching products: a 6-month followup. Int J Dent. 2011;2011:167525. [ Links ]

127. Guênes GMT, Lima AMA, Medeiros LADM, Penha ES, Pinto WT, Santos RL. Avaliação de diferentes sistemas de clareamento dental de consultório. RFO UPF. 2015;20(3):281-6. [ Links ]

128. Guerrero JC, Jiménez-Farfán MD, Lopez-Salgado A, Barker ML, Gerlach RW. Professional whitening strips in a university population. Am J Dent. 2007;20 Spec No A:15-8A. [ Links ]

129. Gurgan S, Cakir FY, Yazici E. Different light-activated in-office bleaching systems: a clinical evaluation. Lasers Med Sci. 2010;25(6):817-22. https://doi.org/10.1007/s10103-009-0688-xLinks ]

130. Hannig C, Lindner D, Attin T. Efficacy and tolerability of two home bleaching systems having different peroxide delivery. Clin Oral Investig. 2007;11(4):321-9. https://doi.org/10.1007/s00784-007-0128-xLinks ]

131. Henry RK, Bauchmoyer SM, Moore W, Rashid RG. The effect of light on tooth whitening: a split-mouth design. Int J Dent Hyg. 2013;11(2):151-4. https://doi.org/10.1111/j.1601-5037.2012.00568.xLinks ]

132. Hyland BW, McDonald A, Lewis N, Tredwin C, Petrie A, Hall S, et al. A new three-component formulation for the efficient whitening of teeth (Carbamide Plus). Clin Oral Investig. 2015;19(6):1395-404. https://doi.org/10.1007/s00784-014-1352-9Links ]

133. Ishikawa-Nagai S, Terui T, Ishibashi K, Weber HP, Ferguson M. Comparison of effectiveness of two 10% carbamide peroxide tooth-bleaching systems using spectrophotometric measurements. J Esthet Restor Dent . 2004;16(6):368-75. https://doi.org/10.1111/j.1708-8240.2004.tb00070.xLinks ]

134. Jadad E, Montoya J, Arana G, Gordillo LA, Palo RM, Loguercio AD. Spectrophotometric evaluation of color alterations with a new dental bleaching product in patients wearing orthodontic appliances. Am J Orthod Dentofacial Orthop. 2011;140(1):e43-7. https://doi.org/10.1016/j.ajodo.2010.11.021. [ Links ]

135. Javaheri DS, Janis JN. The efficacy of reservoirs in bleaching trays. Oper Dent. 2000;25(3):149-51. [ Links ]

136. Karpinia KA, Magnusson I, Sagel PA, Zhou X, Gerlach RW. Vital bleaching with two at-home professional systems. Am J Dent. 2002;15:13-8A. [ Links ]

137. Karpinia K, Magnusson I, Barker ML, Gerlach RW. Clinical comparison of two self-directed bleaching systems. J Prosthodont . 2003;12(4):242-8. https://doi.org/10.1016/S1059-941X(03)00102-5Links ]

138. Kihn P, Barnes DM, Romberg E, Peterson K. A clinical evaluation of 10 percent vs. 15 percent carbamide peroxide tooth-whitening agents. J Am Dent Assoc. 2000;131(10):1478-84. https://doi.org/10.14219/jada.archive.2000.0061Links ]

139. Kihn P, Barnes DM, Romberg E, Adachi E, George D. Clinical evaluation of a 15% in-office hydrogen peroxide tooth-whitening touch-up agent. Compend Contin Educ Dent. 2002;23(10):939-46. [ Links ]

140. Knösel M, Attin R, Becker K, Attin T. External bleaching effect on the color and luminosity of inactive white-spot lesions after fixed orthodontic appliances. Angle Orthod. 2007;77(4):646-52. https://doi.org/10.2319/060106-224Links ]

141. Knösel M, Attin R, Becker K, Attin T. A randomized CIE L*a*b* evaluation of external bleaching therapy effects on fluorotic enamel stains. Quintessence Int. 2008;39(5):391-9. [ Links ]

142. Kose C, Reis A, Baratieri LN, Loguercio AD. Clinical effects of at-home bleaching along with desensitizing agent application. Am J Dent. 2011;24(6):379-82. [ Links ]

143. Kossatz S, Dalanhol AP, Cunha T, Loguercio A, Reis A. Effect of light activation on tooth sensitivity after in-office bleaching. Oper Dent. 2011;36(3):251-7. https://doi.org/10.2341/10-289-CLinks ]

144. Kossatz S, Martins G, Loguercio AD, Reis A. Tooth sensitivity and bleaching effectiveness associated with use of a calcium-containing in-office bleaching gel. J Am Dent Assoc. 2012;143(12):e81-7. http://dx.doi.org/10.14219/jada.archive.2012.0075Links ]

145. Kozlovsky A, Sintov A, Artzi Z, Tal H. Clinical efficacy of a degradable film-forming product containing carbamide peroxide to reduce tooth discolouration. Oral Health. 1996;86(3):47-9. [ Links ]

146. Krause F, Jepsen S, Braun A. Subjective intensities of pain and contentment with treatment outcomes during tray bleaching of vital teeth employing different carbamide peroxide concentrations. Quintessence Int . 2008;39(3). [ Links ]

147. Kugel G, Aboushala A, Zhou X, Gerlach RW. Daily use of whitening strips on tetracycline-stained teeth: comparative results after 2 months. Compend Contin Educ Dent. 2002;23(1A):29-34. [ Links ]

148. Kugel G, Papathanasiou A, Williams 3rd A, Anderson C, Ferreira S. Clinical evaluation of chemical and light-activated tooth whitening systems. Compend Contin Educ Dent. 2006;27(1):54-62. [ Links ]

149. Kugel G, Aboushala A, Sharma S, Ferreira S, Anderson C. Maintenance of whitening with a power toothbrush after bleaching treatment. Compend Contin Educ Dent. 2004;25(2):119-31; quiz 32. [ Links ]

150. Kugel G, Ferreira S, Sharma S, Barker ML, Gerlach RW. Clinical trial assessing light enhancement of in-office tooth whitening. J Esthet Restor Dent . 2009;21(5):336-47. [ Links ]

151. Kugel G, Kastali S. Tooth-whitening efficacy and safety: a randomized and controlled clinical trial. Compendium of continuing education in dentistry. 1999(29):S16-21. [ Links ]

152. Leonard RH, Jr., Haywood VB, Eagle JC, Garland GE, Caplan DJ, Matthews KP, et al. Nightguard vital bleaching of tetracycline-stained teeth: 54 months post treatment. Journal of esthetic dentistry. 1999;11(5):265-77. [ Links ]

153. Leonard Jr RH, Bentley C, Eagle JC, Garland GE, Knight MC, Phillips C. Nightguard vital bleaching: a long-term study on efficacy, shade retention. side effects, and patients’ perceptions. J Esthet Restor Dent. 2001;13(6):357-69. https://doi.org/10.1111/j.1708-8240.1999.tb00408.xLinks ]

154. Leonard RH, Jr., Smith LR, Garland GE, Caplan DJ. Desensitizing agent efficacy during whitening in an at-risk population. J Esthet Restor Dent. 2004;16(1):49-55. https://doi.org/10.1111/j.1708-8240.2004.tb00452.xLinks ]

155. Lewgoy HR, Amore R, Alonso RCB, Di Hipólito V, Anauate Netto C, Barros Filho DA et al. Estudo in vivo do manchamento dental causado pela ingestão de café associada ao clareamento profissional. Rev ABO Nac. 2011;19(2):108-13. [ Links ]

156. Li Y, Lee SS, Cartwright SL, Wilson AC. Comparison of clinical efficacy and safety of three professional at-home tooth whitening systems. Compend Contin Educ Dent. 2003;24(5):357-60. [ Links ]

157. Lo EC, Wong AH, McGrath C. A randomized controlled trial of home tooth-whitening products. Am J Dent. 2007;20(5):315-8. [ Links ]

158. Lo Giudice R, Pantaleo G, Lizio A, Romeo U, Castiello G, Spagnuolo G et al. Clinical and spectrophotometric evaluation of LED and laser activated teeth bleaching. Open Dent J. 2016;10(1):242-50. https://doi.org/10.2174/1874210601610010242Links ]

159. Loguercio AD, Tay LY, Herrera DR, Bauer J, Reis A. Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial. Braz Oral Res. 2015;29:1-7. https://doi.org/10.1590/1807-3107BOR-2015.vol29.0099Links ]

160. Loyola-Rodriguez JP, Pozos-Guillen AJ, Hernandez-Hernandez F, Berumen-Maldonado R, Patiño-Marin N. Effectiveness of treatment with carbamide peroxide and hydrogen peroxide in subjects affected by dental fluorosis: a clinical trial. J Clin Pediatr Dent. 2003;28(1):63-7. https://doi.org/10.17796/jcpd.28.1.1q78t43054jk5911Links ]

161. Luo W, Westland S, Brunton P, Ellwood R, Pretty IA, Mohan N. Comparison of the ability of different colour indices to assess changes in tooth whiteness. J Dent. 2007;35(2):109-16. https://doi.org/10.1016/j.jdent.2006.06.006Links ]

162. Machado LS, de Oliveira FG, Rocha EP, dos Santos PH, Briso AL, Sundefeld ML, et al. Clinical trial evaluating color change and tooth sensitivity throughout and following in-office bleaching. Int J Periodontics Restorative Dent . 2013;33(2):209-15. https://doi.org/10.11607/prd.1410Links ]

163. Machado LS, Anchieta RB, Santos PH, Briso AL, Tovar N, Janal MN et al. Clinical comparison of at-home and in-office dental bleaching procedures: a randomized trial of a split-mouth design. Int J Periodontics Restorative Dent. 2016;36(2):251-60. https://doi.org/10.11607/prd.2383Links ]

164. Maghaireh GA, Alzraikat H, Guidoum A. Assessment of the effect of casein phosphopeptide-amorphous calcium phosphate on postoperative sensitivity associated with in-office vital tooth whitening. Oper Dent. 2014;39(3):239-47. https://doi.org/10.2341/12-527-CLinks ]

165. Marson FC, Sensi LG, Vieira LC, Araújo E. Clinical evaluation of in-office dental bleaching treatments with and without the use of light-activation sources. Oper Dent. 2008;33(1):15-22. https://doi.org/10.2341/07-57Links ]

166. Martín J, Ovies N, Cisternas P, Fernández E, Oliveira Junior OB, Andrade MF et al. Can an LED-laser hybrid light help to decrease hydrogen peroxide concentration while maintaining effectiveness in teeth bleaching? Laser Physics. 2015;25(2):025608. https://doi.org/10.1088/1054-660X/25/2/025608Links ]

167. Martins GC, Izidoro ACSA, Meister LMB, Kossatz S, Gomes OM, Loguercio A et al. Efeito do uso prévio de um dessensibilizante na sensibilidade do clareamento de consultório. São Paulo: Associação Paulista de Cirurgiões Dentistas; 2010. [ Links ]

168. Matis BA, Cochran MA, Eckert G, Carlson TJ. The efficacy and safety of a 10% carbamide peroxide bleaching gel. Quintessence Int . 1998;29(9):555-63. [ Links ]

169. Matis BA, Mousa HN, Cochran MA, Eckert GJ. Clinical evaluation of bleaching agents of different concentrations. Quintessence Int . 2000;31(5):303-10. [ Links ]

170. Matis BA, Hamdan YS, Cochran MA, Eckert GJ. A clinical evaluation of a bleaching agent used with and without reservoirs. Oper Dent. 2002;27(1):5-11. [ Links ]

171. Matis BA, Wang Y, Jiang T, Eckert GJ. Extended at-home bleaching of tetracycline-stained teeth with different concentrations of carbamide peroxide. Quintessence Int . 2002;33(9):645-55. [ Links ]

172. Matis BA, Cochran M, Wang G, Franco M, Eckert GJ, Carlotti RJ et al. A clinical evaluation of bleaching using whitening wraps and strips. Oper Dent. 2005;30(5):588-92. [ Links ]

173. Matis BA, Wang Y, Eckert GJ, Cochran MA, Jiang T. Extended bleaching of tetracycline-stained teeth: a 5-year study. Oper Dent. 2006;31(6):643-51. https://doi.org/10.2341/06-6Links ]

174. Matis BA, Cochran MA, Eckert GJ, Matis JI. In vivo study of two carbamide peroxide gels with different desensitizing agents. Oper Dent. 2007;32(6):549-55. https://doi.org/10.2341/07-10Links ]

175. Matis BA, Cochran MA, Wang G, Eckert GJ. A clinical evaluation of two in-office bleaching regimens with and without tray bleaching. Oper Dent. 2009;34(2):142-9. https://doi.org/10.2341/08-64Links ]

176. Medeiros MCS, Lima KC. Effectiveness of nightguard vital bleaching with 10% carbamide peroxide: a clinical study. J Can Dent Assoc. 2008;74(2):163-163e. [ Links ]

177. Mehta D, Venkata S, Naganath M, LingaReddy U, Ishihata H, Finger WJ. Clinical trial of tooth desensitization prior to in-office bleaching. Eur J Oral Sci. 2013;121(5):477-81. https://doi.org/10.1111/eos.12067Links ]

178. Meireles SS, Heckmann SS, Santos IS, Della Bona A, Demarco FF. A double blind randomized clinical trial of at-home tooth bleaching using two carbamide peroxide concentrations: 6-month follow-up. J Dent. 2008;36(11):878-84. https://doi.org/10.1016/j.jdent.2008.07.002Links ]

179. Meireles SS, Heckmann SS, Leida FL, dos Santos IS, Della Bona A, Demarco FF. Efficacy and safety of 10% and 16% carbamide peroxide tooth-whitening gels: a randomized clinical trial. Oper Dent. 2008;33(6):606-12. https://doi.org/10.2341/07-150Links ]

180. Meireles SS, Santos IS, Della Bona A, Demarco FF. A double-blind randomized controlled clinical trial of 10 percent versus 16 percent carbamide peroxide tooth-bleaching agents: one-year follow-up. J Am Dent Assoc. 2009;140(9):1109-17. https://doi.org/10.14219/jada.archive.2009.0337Links ]

181. Meireles SS, Santos IS, Bona AD, Demarco FF. A double-blind randomized clinical trial of two carbamide peroxide tooth bleaching agents: 2-year follow-up. J Dent. 2010;38(12):956-63. https://doi.org/10.1016/j.jdent.2010.08.003Links ]

182. Meireles SS, Goettems ML, Dantas RV, Bona AD, Santos IS, Demarco FF. Changes in oral health related quality of life after dental bleaching in a double-blind randomized clinical trial. J Dent. 2014;42(2):114-21. https://doi.org/10.1016/j.jdent.2013.11.022Links ]

183. Miller MB, Castellanos IR, Rieger MS. Efficacy of home bleaching systems with and without tray reservoirs. Pract Periodontics Aesthet Dent. 2000;12(6):611-4. [ Links ]

184. Moghadam FV, Majidinia S, Chasteen J, Ghavamnasiri M. The degree of color change, rebound effect and sensitivity of bleached teeth associated with at-home and power bleaching techniques: A randomized clinical trial. Eur J Dent. 2013;7(4):405-11. https://doi.org/10.4103/1305-7456.120655Links ]

185. Mohan N, Westland S, Brunton P, Ellwood R, Pretty IA, Luo W. A clinical study to evaluate the efficacy of a novel tray based tooth whitening system. J Dent. 2008;36(1):21-6. https://doi.org/10.1016/j.jdent.2007.10.002Links ]

186. Mokhlis GR, Matis BA, Cochran MA, Eckert GJ. A clinical evaluation of carbamide peroxide and hydrogen peroxide whitening agents during daytime use. J Am Dent Assoc. 2000;131(9):1269-77. https://doi.org/10.14219/jada.archive.2000.0380Links ]

187. Mondelli RF, Azevedo JF, Francisconi AC, Almeida CM, Ishikiriama SK. Comparative clinical study of the effectiveness of different dental bleaching methods-two year follow-up. Journal of Applied Oral Science. 2012;20(4):435-43. https://doi.org/10.1590/S1678-77572012000400008Links ]

188. Montenegro-Arana A, Arana-Gordillo LA, Farana D, Davila-Sanchez A, Jadad E, Coelho U et al. Randomized double-blind clinical trial of bleaching products in patients wearing orthodontic devices. Oper Dent. 2016;41(4):379-87. https://doi.org/10.2341/15-240-CLinks ]

189. Morgan S, Jum’ah AA, Brunton P. Assessment of efficacy and post-bleaching sensitivity of home bleaching using 10% carbamide peroxide in extended and non-extended bleaching trays. Br Dent J. 2015;218(10):579-82. https://doi.org/10.1038/sj.bdj.2015.391Links ]

190. Myers ML, Browning WD, Downey MC, Hackman ST. Clinical evaluation of a 3% hydrogen peroxide tooth-whitening gel l. J Esthet Restor Dent . 2003;15(1):50-6. https://doi.org/10.1111/j.1708-8240.2003.tb00282.xLinks ]

191. Nathoo S, Santana 3rd E, Zhang Y, Lin N, Collins M, Klimpel K et al. Comparative seven-day clinical evaluation of two tooth whitening products. Compend Contin Educ Dent. 2001;22(7):599-604. [ Links ]

192. Nathoo S, Stewart B, Petrone ME, Chaknis P, Zhang YP, DeVizio W et al. Comparative clinical investigation of the tooth whitening efficacy of two tooth whitening gels. J Clin Dent. 2002;14(3):64-9. [ Links ]

193. Navarra CO, Reda B, Diolosà M, Casula I, Di Lenarda R, Breschi L et al. The effects of two 10% carbamide peroxide nightguard bleaching agents, with and without desensitizer, on enamel and sensitivity: an in vivo study. Int J Dent Hyg. 2014;12(2):115-20. https://doi.org/10.1111/idh.12054Links ]

194. Nutter BJ, Sharif MO, Smith AB, Brunton PA. A clinical study comparing the efficacy of light activated in-surgery whitening versus in-surgery whitening without light activation. J Dent. 2013;41 Suppl 5:e3-7. https://doi.org/10.1016/j.jdent.2013.03.004Links ]

195. Ontiveros JC, Paravina RD. Color change of vital teeth exposed to bleaching performed with and without supplementary light. J Dent. 2009;37(11):840-7. https://doi.org/10.1016/j.jdent.2009.06.015Links ]

196. Palé M, Mayoral JR, Llopis J, Vallès M, Basilio J, Roig M. Evaluation of the effectiveness of an in-office bleaching system and the effect of potassium nitrate as a desensitizing agent. Odontology. 2014;102(2):203-10. https://doi.org/10.1007/s10266-013-0132-3Links ]

197. Papathanasiou A, Bardwell D, Kugel G. A clinical study evaluating a new chairside and take-home whitening system. Compend Contin Educ Dent. 2001;22(4):289-94. [ Links ]

198. Papathanasiou A, Kastali S, Perry RD, Kugel G. Clinical evaluation of a 35% hydrogen peroxide in-office whitening system. Compend Contin Educ Dent. 2002;23(4):335-8. [ Links ]

199. Perry R, Conde E, Farrell S, Gerlach R, Towers J. Comparative performance of two whitening systems in a dental practice. Compend Contin Educ Dent. 2012;34:15-8. [ Links ]

200. Polydorou O, Wirsching M, Wokewitz M, Hahn P. Three-month evaluation of vital tooth bleaching using light units-a randomized clinical study. Oper Dent. 2013;38(1):21-32. https://doi.org/10.2341/12-041-CLinks ]

201. Posso Moreno SL, Ramírez Ramírez DX, Rosas Jaimes JA, Güiza Cristancho EH. Comparación del blanqueamiento dental con peróxido de hidrógeno al 25 percent en consultorio, utilizando o no activación con lámpara de luz halógena. Univ Odontol. 2010;29(62):19-25. [ Links ]

202. Reis A, Tay LY, Herrera DR, Kossatz S, Loguercio AD. Clinical effects of prolonged application time of an in-office bleaching gel. Oper Dent. 2011;36(6):590-6. https://doi.org/10.2341/10-173-CLinks ]

203. Reis A, Dalanhol AP, Cunha TS, Kossatz S, Loguercio AD. Assessment of tooth sensitivity using a desensitizer before light-activated bleaching. Oper Dent. 2011;36(1):12-7. https://doi.org/10.2341/10-148-CRLinks ]

204. Reis A, Kossatz S, Martins GC, Loguercio AD. Efficacy of and effect on tooth sensitivity of in-office bleaching gel concentrations: a randomized clinical trial. Oper Dent. 2013;38(4):386-93. https://doi.org/10.2341/12-140-CLinks ]

205. Rezende M, Siqueira SH, Kossatz S. Clareamento dental-efeito da técnica sobre a sensibilidade dental e efetividade. Rev Assoc Paul Cir Dent. 2014;68(3):208-12. [ Links ]

206. Rezende M, Loguercio AD, Reis A, Kossatz S. Clinical effects of exposure to coffee during at-home vital bleaching. Oper Dent. 2013;38(6):E229-36. https://doi.org/10.2341/12-188-CLinks ]

207. Rezende M, De Geus JL, Loguercio AD, Reis A, Kossatz D. Clinical evaluation of genotoxicity of in-office bleaching. Oper Dent. 2016;41(6):578-86. https://doi.org/10.2341/15-207-CLinks ]

208. Rosenstiel SF, Gegauff AG, Johnston WM. Randomized clinical trial of the efficacy and safety of a home bleaching procedure. Quintessence Int . 1996;27(6):413-24. [ Links ]

209. Santana MAP, Nahsan FPS, Oliveira AHA, Loguércio AD, Faria-e-Silva AL. Randomized controlled trial of sealed in-office bleaching effectiveness. Braz Dent J. 2014;25(3):207-11. https://doi.org/10.1590/0103-6440201300072Links ]

210. Shahidi H, Barker ML, Sagel PA, Gerlach RW. Randomized controlled trial of 10% hydrogen peroxide whitening strips. J Clin Dent. 2004;16(3):91-5. [ Links ]

211. Shanbhag R, Veena R, Nanjannawar G, Patil J, Hugar S, Vagrali H. Use of clinical bleaching with 35% hydrogen peroxide in esthetic improvement of fluorotic human incisors in vivo. J Contemp Dent Pract. 2013;14(2):208-16. https://doi.org/10.5005/jp-journals-10024-1301Links ]

212. Sielski C, Conforti N, Stewart B, Chaknis P, Petrone ME, DeVizio W et al. A clinical investigation of the efficacy of a tooth-whitening gel. Compend Contin Educ Dent. 2003;24(8):612-4, 6-8. [ Links ]

213. Silva FM, Nacano LG, Pizi ECG. Avaliação clínica de dois sistemas de clareamento dental. Rev Odontol Brasil Central. 2012;21(56):473-9. [ Links ]

214. Simon JF, Powell L, Hollis S, Anastasia MK, Gerlach RW, Farrell S. Placebo-controlled clinical trial evaluating 9.5% hydrogen peroxide high-adhesion whitening strips. J Clin Dent. 2014;25(3):49-52. [ Links ]

215. Soares CJ, Silva NRd, Quagliatto PS, Campos RE. Avaliação clínica de clareamento caseiro com gel de peróxido de carbamida industrializado e manipulado em farmácia. Rev Odontol UNESP. 2006;35(1):69-74. [ Links ]

216. Strobl A, Gutknecht N, Franzen R, Hilgers RD, Lampert F, Meister J. Laser-assisted in-office bleaching using a neodymium:yttrium-aluminum-garnet laser: an in vivo study. Lasers Med Sci. 2010;25(4):503-9. https://doi.org/10.1007/s10103-009-0675-2Links ]

217. Sundfeld RH, Sundfeld Neto D, Machado LS, de Oliveira FG, de Alexandre RS, Palo RM, et al. Dental bleaching with a 10% hydrogen peroxide product: a six-month clinical observation. Indian J Dent Res. 2014;25(1):4-8. https://doi.org/10.4103/0970-9290.131046Links ]

218. Swift EJ, May KN, Wilder AD, Heymann HO, Wilder RS, Bayne SC. Six-month clinical evaluation of a tooth whitenin system using an innovate experimental design. J Esthet Restor Dent . 1997;9(5):265-75. https://doi.org/10.1111/j.1708-8240.1997.tb00952.xLinks ]

219. Swift EJ Jr, May KN Jr, Wilder AD Jr, Heymann HO, Bayne SC. Two-year clinical evaluation of tooth whitening using an at-home bleaching system. J Esthet Restor Dent . 1999;11(1):36-42. https://doi.org/10.1111/j.1708-8240.1999.tb00374.xLinks ]

220. Swift EJ Jr, Miguez PA, Barker ML, Gerlach RW. Three-week clinical trial of a 14% hydrogen-peroxide, strip-based bleaching system. Compend Contin Educ Dent. 2004;25(8 Suppl 2):27-32. [ Links ]

221. Swift EJ Jr., Heymann HO, Wilder AD, Jr., Barker ML, Gerlach RW. Effects of duration of whitening strip treatment on tooth color: a randomized, placebo-controlled clinical trial. J Dent. 2009;37 Suppl 1:e51-6. https://doi.org/10.1016/j.jdent.2009.05.009Links ]

222. T Tavares M, Stultz J, Newman M, Smith V, Kent R, Carpino E et al. Light augments tooth whitening with peroxide. J Am Dent Assoc. 2003;134(2):167-75. https://doi.org/10.14219/jada.archive.2003.0130Links ]

223. Tay LY, Kose C, Herrera DR, Reis A, Loguercio AD. Long-term efficacy of in-office and at-home bleaching: a 2-year double-blind randomized clinical trial. Am J Dent. 2012;25(4):199-204. [ Links ]

224. Tsubura S. Clinical evaluation of three months’ nightguard vital bleaching on tetracycline-stained teeth using Polanight 10% carbamide gel: 2-year follow-up study. Odontology. 2010;98(2):134-8. https://doi.org/10.1007/s10266-010-0130-7Links ]

225. Tsubura S, Yamaguchi R. Clinical evaluation of a new bleaching product “Polanight” in a Japanese population. Odontology. 2005;93(1):52-5. https://doi.org/10.1007/s10266-005-0047-8Links ]

226. Turkun M, Celik EU, Aladag A, Gokay N. One-year clinical evaluation of the efficacy of a new daytime at-home bleaching technique. J Esthet Restor Dent . 2010;22(2):139-46. https://doi.org/10.1111/j.1708-8240.2010.00325.xLinks ]

227. Vano M, Derchi G, Barone A, Genovesi A, Covani U. Tooth bleaching with hydrogen peroxide and nano-hydroxyapatite: a 9-month follow-up randomized clinical trial. Int J Dent Hyg. 2015;13(4):301-7. https://doi.org/10.1111/idh.12123Links ]

228. Ward M, Felix H. A clinical evaluation comparing two H2O2 concentrations used with a light-assisted chairside tooth whitening system. Compend Contin Educ Dent. 2012;33(4):286-91. [ Links ]

229. Wetter NU, Branco EP, Deana AM, Pelino JE. Color differences of canines and incisors in a comparative long-term clinical trial of three bleaching systems. Lasers Med Sci. 2009;24(6):941-7. https://doi.org/10.1007/s10103-008-0575-xLinks ]

230. Xu X, Zhu L, Tang Y, Wang Y, Zhang K, Li S, et al. Randomized clinical trial comparing whitening strips, paint-on gel and negative control. Am J Dent. 2007;20 Spec No A::28-31A. [ Links ]

231. Yudhira R, Peumans M, Barker ML, Gerlach RW. Clinical trial of tooth whitening with 6% hydrogen peroxide whitening strips and two whitening dentifrices. Am J Dent. 2007;20 Spec No A:32-6A. [ Links ]

232. Zantner C, Derdilopoulou F, Martus P, Kielbassa AM. Randomized clinical trial on the efficacy of 2 over-the-counter whitening systems. Quintessence Int. 2006;37(9):696-706. [ Links ]

233. Zekonis R, Matis BA, Cochran MA, Al Shetri SE, Eckert GJ, Carlson TJ. Clinical evaluation of in-office and at-home bleaching treatments. Oper Dent. 2003;28(2):114-21. [ Links ]

234. Zhao K, Zong L, Zhang Q, Att W. Clinical comparison between two bleaching techniques: a 180-day follow-up study. Quintessence Int . 2013;44(8):601-7. [ Links ]

235. Ziebolz D, Helms K, Hannig C, Attin T. Efficacy and oral side effects of two highly concentrated tray-based bleaching systems. Clin Oral Investig. 2007;11(3):267-75. https://doi.org/10.1007/s00784-007-0108-1Links ]

236. Ziemba SL, Felix H, MacDonald J, Ward M. Clinical evaluation of a novel dental whitening lamp and light-catalyzed peroxide gel. The Journal of clinical dentistry. 2005;16(4):123-7. [ Links ]

Received: May 13, 2017; Accepted: May 22, 2017; Revised: May 28, 2017

Corresponding Author: Jorge Perdigão. E-mail: perdi001@umn.edu

Declaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript.

Creative Commons License  This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.