Evaluation of Tooth Sensitivity of In-office Bleaching with Different Light Activation Sources: A Systematic Review and a Network Meta-analysis
A systematic review and network meta-analysis were performed to answer the following research question: Are there differences in the risk and the intensity of tooth sensitivity (TS) among eight light activation systems for in-office bleaching in adults? Randomized controlled trials (RCTs) that compared at least two different in-office bleaching light activations were included. The risk of bias (RoB) was evaluated with the RoB tool version 1.0 from the Cochrane Collaboration tool. A random-effects Bayesian mixed treatment comparison (MTC) model was used independently for high- and low-concentration hydrogen peroxide. The certainty of the evidence was evaluated using the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. A comprehensive search was performed in PubMed, Bridge Base Online (BBO), Latin American and Caribbean Health Sciences Literature database (LILACS), Cochrane Library, Scopus, Web of Science, and grey literature without date and language restrictions on April 23, 2017 (updated on September 26, 2019). Dissertations and theses, unpublished and ongoing trials registries, and IADR (International Association for Dental Research) abstracts (2001–2019) were also searched. After title and abstract screening and the removal of duplicates, 32 studies remained. Six were considered to be at low RoB, three had high RoB, and the remaining had an unclear RoB. The MTC analysis showed no significant differences among the treatments in each network. In general, the certainty of the evidence was graded as low due to unclear RoB and imprecision. There is no evidence that the risk and intensity of TS are affected by light activation during in-office bleaching.SUMMARY
Objectives:
Methods:
Results:
Conclusion:
INTRODUCTION
A Brazilian study1 that evaluated patients’ desire to undergo dental bleaching reported that 85.9% of the patients wanted to undertake the treatment, and this desire was 2.31 times higher in patients who visited the dentist in the last year, compared to those who visited the dentist more than a year ago. Another cross-sectional study conducted in Iran2 reported that approximately 62% of patients preferred dental bleaching for cosmetic treatment. In Israel,3 a study showed that 56.2% of patients were not happy with the color of their teeth and that dental bleaching was the treatment most desired by patients. Therefore, dental bleaching has become the treatment of choice to improve patients’ smiles and self-esteem4 because it is a simple and non-invasive technique for the treatment of discolored teeth.
Currently, there are three types of dentist-supervised bleaching techniques: at-home bleaching, in-office bleaching, and combined bleaching technique.5,6 Regardless of the bleaching technique, the mechanism of action seems to be the oxidization of organic components of the dental substrate by unstable free radicals produced by the dissociation of hydrogen peroxide (HP), an oxidizing agent capable of diffusing into the dental structure.7
Although at-home bleaching is widely used by patients,8 in-office bleaching is usually chosen by patients who do not like wearing trays and who wish for more immediate results.9 There are various bleaching agent brands that vary in concentration,10 pH,11 application method,12 and duration of application,13 factors which may play a role in the degree of whitening. Additionally, bleaching agents can be used with light sources,14 with the aim of accelerating the bleaching effect. Light-emitting diodes (LEDs), lasers, halogen lamps, and plasma arc lamps (PACs) are some of the devices used for light activation of the bleaching gel.
It is known that different light activation systems vary in type of lamp, energy outcome, energy delivery, and generated heat. For instance, the heat produced by a PAC is much higher than that produced by a halogen lamp,15 which, in turn, is higher than that produced by an LED.16 Although we have shown in previous network analysis that these differences had no impact on the whitening outcome,17 they may affect patient experiences of tooth sensitivity (TS).
The systematic review of the literature with network meta-analysis performed in this work allows the comparison of different treatments in a single model and provides clinicians with scientific evidence on the effectiveness of multiple interventions.18 Mixed treatment comparison (MTC) models combine two sources of evidence: the indirect one that comes from different trials with a common comparator (such as bleaching without light) and direct comparisons of light activation (that is, head-to-head trials).19
Thus, the purpose of this systematic review was to compare the risk and intensity of bleaching-induced TS associated with different light sources: light-free and seven types of light-activated bleaching (halogen lamp, laser, LED/laser, LED, metal halide light, violet light, and PAC) for high- or low-concentration HP.
METHODS AND MATERIALS
Protocol and Registration
This study protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO) under number CRD42018095806 and followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement for reports.20
Eligibility Criteria
The following participant-intervention-comparator-outcome (PICO) framework research question was investigated in this study: Are there differences in the risk and intensity of tooth sensitivity associated with in-office bleaching performed in adults with eight different light activation systems (light-free, halogen lamp, LED/laser, LED, metal halide light, violet light, laser, and PAC)?
We included parallel and split-mouth RCTs that compared at least two of these different light activation systems. RCTs were excluded if they compared in-office dental bleaching with combined bleaching. To minimize publication bias, no year or language restrictions were applied.
Information Sources and Search Strategy
Controlled vocabulary (MeSH terms) and free keywords, defined based on the concepts of the PICO question, were used for the search strategy. The search strategy was first performed in MEDLINE (Table 1) via PubMed and then adapted to other databases (Cochrane Library, Brazilian Library in Dentistry, LILACS, and the citation databases Scopus and Web of Science) (Table 1). The reference lists of all primary studies were hand-searched for additional relevant publications. We also searched the first page of related article links of each primary study in the PubMed database to increase the sensitivity of the search.
Additionally, grey literature was investigated by searching dissertations and theses from the ProQuest Dissertations and Theses full-text database, Periódicos Capes Theses database, the abstracts of the annual conference of the International Association for Dental Research and its regional divisions (2001-2019), and the database System for Information on Grey Literature in Europe. The following clinical trial registries were also inspected to locate unpublished and ongoing trials: Current Controlled Trials, International Clinical Trials Registry Platform, ClinicalTrials.gov, ReBEC, and EU Clinical Trials Register.
Study Selection and Data Collection Process
Articles that appeared in more than one database were considered only once. After removal of duplicates, three review authors (BMM, AB, and TPM) screened the articles by title and then by abstract. When the title and abstract presented insufficient information, full-text articles were obtained to make a clear decision. Subsequently, the three reviewers classified those that met the inclusion criteria.
Each eligible article received a study ID combining the first author’s name and the year of publication. Relevant information about the study design, participants, interventions, and outcomes was extracted independently, using customized extraction forms. In the case of disagreements between the review authors, a fourth author was consulted (AR). Studies usually assess TS at different points in time, which is a source of variation among them; to deal with that problem, we collected the worst mean/score value from the numeric rating scale (NRS) or visual analog scale (VAS) for the risk and intensity of TS reported for the study group.
In studies with more than two experimental groups (ie, three- or four-arm studies), different pairwise comparisons were included in the network meta-analysis. However, to avoid double counts of the “shared group,” the number of events and participants was divided approximately evenly between comparisons for dichotomous outcomes. For continuous outcomes, the means and standard deviations were kept constant, and the number of patients divided among the comparisons.
Risk of Bias in Individual Studies
The risk of bias (RoB) of the eligible trials was determined by three independent reviewers using the RoB tool from the Cochrane Collaboration for RCTs.21 The assessment criteria are composed of six domains: selection bias (adequate sequence generation and allocation concealment), performance bias (blinding of participants and patients), detection bias (blinding of evaluators), attrition bias (incomplete outcome data), reporting bias (selective reporting), and other sources of bias. The last domain was not assessed in this systematic review. Disagreements between the reviewers were solved through discussion and, if needed, by consulting a fourth reviewer (AR).
Each domain level was judged as low, high, or unclear RoB. At the study level, the study was considered to have low RoB if all domains of each outcome had low RoB. If one or two key domains were judged as having unclear RoB, the study was classified as unclear RoB; if at least one key domain had high RoB, the study was considered to have high RoB.
Summary Measures and Statistical Analyses
Independent analyses were performed for two outcomes (intensity of TS with pain scales, risk of TS) and considered both high- and low-concentration bleaching gels. Products with HP concentrations higher than 25% were classified as high-concentration products, and those with concentrations equal to or lower than 25% were considered low-concentration products. This classification was done based on the previous knowledge of the different HP concentrations available in the international dental market. Although this arbitrary classification may have implications in the study results, lack of classification would merge a wide variety of HP concentrations into a single group, providing unrealistic findings.
Traditional and network meta-analyses were conducted using mean difference (MD) or standardized mean difference (SMD) for the intensity of TS and risk ratio (RR) for risk of TS. The choice of the effect measure for continuous outcomes depended on whether or not studies used different instruments/scales for measurement of the outcome. For the intensity of TS, we included in the meta-analyses studies that used VAS or NRS scales, and SMD was chosen as the effect measure.
Traditional meta-analysis was performed for all pairwise comparisons where evidence was available from one or more head-to-head studies. Random effect models with the DerSimonian and Laird variance estimator were used since high heterogeneity among studies was expected. The Mantel-Haenzel method was used for the risk of TS (dichotomous), and the inverse of the variance method was used for the intensity of TS (continuous). The I2 statistic and the Cochran Q test were used to measure heterogeneity among studies.
MTC is a Bayesian hierarchy model supported by Markov Chain Monte Carlo (MCMC) methods. Its versatility allows the simultaneous comparison of all eight treatments and the incorporation of trials with three or more arms. The evidence of each possible pairwise comparison was evaluated exclusively from direct evidence (head-to-head trials), exclusively from indirect evidence (trials with a common comparator), or from a combination of both, depending on what evidence was available for each pair. Both fixed and random effects with homogeneity of variances were adjusted, and the one with the better performance following the Deviance Information Criterion (DIC) was chosen. The consistency assumption was checked for all pairwise comparisons that had both direct and indirect evidence, using the Bayesian p-values produced by the node-splitting method proposed by Dias and others.22 The evidence of a pair was considered inconsistent if the p-value was lower than the significance level (α=0.05) adjusted for multiple comparisons. The results were displayed in point estimates and 95% credible intervals (CrIs, [CrIs are the Bayesian equivalent of frequentist confidence intervals]). Surface under the cumulative ranking curve (SUCRA) values (higher values indicate smaller risk or intensity of TS) were also calculated if at least one comparison of the network was found to have a significant difference. All analyses were implemented using the meta (multi-environment trail analysis) and GeMTC packages of the R statistical program (R Foundation).
Assessment of the Certainty of the Evidence Using Grading of Recommendations: Assessment, Development, and Evaluation
We followed the GRADE approach to appraise the confidence in estimates derived from network meta-analysis. Direct evidence from RCTs starts at high confidence and can be rated down based on RoB, indirectness, imprecision, or inconsistency (heterogeneity); publication bias can be rated to levels of moderate, low, and very low confidence. The rating of indirect estimates starts at the lowest rating of the pairwise estimates that contribute as first-order loops to the indirect estimate but can be rated down further due to imprecision or intransitivity (dissimilarity between studies in terms of clinical or methodological characteristics). If direct and indirect estimates are similar (ie, coherent), then the higher of their ratings can be assigned to the network meta-analysis estimates.
RESULTS
Study Selection
The database screening returned a total of 9442 studies, which was reduced to 5541 following the removal of duplicates. After title screening, 227 studies remained, and this number was reduced to 32 full texts that were assessed for eligibility (Figure 1).
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Characteristics of Included Articles
Study Design and Method of Tooth Sensitivity Evaluation—
The characteristics of the 32 eligible primary studies are listed in Table 2. The study design was balanced: nineteen studies used parallel design14,23–41 and thirteen studies used the split-mouth design.42–54
Twenty studies evaluated the intensity of TS; of these, fourteen employed the VAS for pain evaluation,a five employed the NRS,24,27,29,42,45 and only one36 employed both the VAS and NRS.
The risk of TS was evaluated in twelve studies.b
Age and Gender of The Patients in the Primary RCTs—
The patients ranged from 18 to 78 years old; ten studies did not report participant age.31,37,43,46,47,49–53 The mean age of all participants included in the RCTs that reported this information was approximately 27.9 years, showing a predominance of young adults (Table 2). Females were predominant in most studies that reported this characteristic.c
Bleaching Protocols—
High-concentration HP. Twenty-four studies used high-concentration HP.d The concentration of the products employed were: 35%, 37%, 38% (varying from 35% to 38%) (Table 2).
Low-concentration HP. Seventeen studies used low-concentration HP.e The concentrations of the products employed were: 6%, 15%, 20%, 25% (varying from 6% to 25%); when 35% CP was used, the study was included in the low-concentration HP subgroup as 35% CP corresponds to approximately 12% active HP58 (Table 2).
The application protocol of the in-office bleaching was quite varied. Several studies applied the product in three 15-minute applications in each clinical session.f However, variations with one to five applications per clinical session were also observed.
Most studies involved only a single clinical session,g but two to four clinical sessions with intervals between seven and 15 days were also observed (Table 2).
Different types of light activation were used. Six studies used halogen lamps,14,24,33,45,52,57 eighteen used LEDs/lasers,h five used only LEDs,24,30,33,42,45 seven used metal-halide light,24,32,40,46,47,51,54 three used a violet light,28,37,41 three used only a laser source,14,30,53 and two used PACs30,39 with various protocols.
Assessment of the RoB
The RoB of the eligible studies is presented in Figure 2. Six studies were classified as having low RoB,27,36,39,44,48,50 and three were considered to have high RoB.32,34,35,38 A few full-text studies reported the method of randomization and allocation concealment and therefore were classified as having unclear RoB.
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Traditional and Network Meta-analysis
In this phase, thirteen eligible studies could not be meta-analyzed. The studies by Bortolatto (2014),26 Bortolatto (2016),27 Kugel (2006),47 Martin (2015),48 and Martin (2015)35 were removed because the authors compared a low-concentration HP with a high-concentration HP. The studies by Henry (2013),46 Michielin (2015),37 Mondelli (2012),49 Papathanasiou (2002),52 Santos (2018),41 and Strobl (2010)53 were removed because the data could not be extracted. The studies by Ferraz (2018)29 and Ward (2012)54 were removed because the authors did not have a common comparator group. In summary, nineteen studies were included in the meta-analysis. Thirteen studies had only two arms,i two studies had three arms,14,57 and four studies had four arms.24,30,33,45 The geometry of the evidence is presented in Figure 3. In the network figures, each node represents a treatment, and the line thickness represents the number of studies included in the comparison.
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Risk of Tooth Sensitivity
Regarding the risk of TS, a total of five treatments with high-concentration products were compared in the network (Figure 3A), totaling ten pairs of comparisons with 351 patients. Direct evidence was available for eight pairs (Figure S1A) and no significant differences in risk among treatments were found. The results from the network meta-analysis are described in Figure 4 (lower diagonal). This network of evidence has some pairwise comparisons with only indirect evidence (LED vs. laser, for example) and six comparisons with both direct and indirect evidence, for which no inconsistency was found (Figure 5). Network results also show no difference among the five treatments.
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
In the consideration of products with low concentration, five treatments were compared (Figure 3B), totaling ten pairs of comparisons with 168 patients. Direct evidence was available for four pairs (Figure S1B) and no significant differences in risk were found. As we can see from the geometry of the network (Figure 3B), the four pairs of comparisons have only direct evidence, with the light-free condition as the common comparator. The results from this network meta-analysis are described in Figure 4 (upper diagonal), which also shows that there was no evidence of difference among the five treatments.
Intensity of Tooth Sensitivity
Regarding the intensity of TS, a total of seven treatments with high concentration products were compared in the network (Figure 3C), totaling 21 pairs of comparisons with 395 patients. Direct evidence was available for 14 pairs (Figure S2A), and no significant differences in intensity were found. The results from the network meta-analysis are described in Figure 6 (lower diagonal). This network of evidence has some pairwise comparisons with only indirect evidence (PAC vs. metal halide light, for example) and six comparisons with both, direct and indirect evidence, for which no statistical inconsistency was found (Figure 7). When all treatments were analyzed together, no evidence of difference was found.
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Citation: Operative Dentistry 46, 5; 10.2341/20-127-L
Considering products with low concentration, three treatments were compared (Figure 3D), totaling three pairs of comparisons with 128 patients. Direct evidence was available for two pairs (Figure S2B), and no significant differences in intensity were found. As we can see from the geometry of the network (Figure 3D), the pair comparing metal halide light to LED/laser has only direct evidence, with the light-free condition as the common comparator. The results from this network meta-analysis are described in Figure 6 (upper diagonal), which also shows no evidence of difference among the three treatments.
Sensitivity Analysis
In two studies that did not report the standard deviation (SD),43,45,50 we imputed an SD based on the average of the coefficients of variation of the other studies that reported the same finding.59 More extreme imputations (such as a value corresponding to the lowest coefficient of variation of the primary studies and a value that was as high as the reported mean) were evaluated in a sensitivity analysis, and no differences in the results reported here could be detected.
The studies by Almeida Farhat (2014),42 Alomari (2010),24 and Gomes (2008)45 used NRS pain scale to measure the intensity of TS, so SMD was used to summarize the effect of high-concentration products on intensity of TS. We also performed a sensitivity analysis by removing these three studies and using MD. The same conclusions in MTC analysis were observed whether the MTC was run with MD or SMD effect measures.
Assessment of the Certainty of the Evidence
In general, the quality of evidence was graded as low, due to unclear RoB and imprecision (Figures 4 and 6). Some comparisons were graded as very low, due to an unclear RoB in the vast majority of the studies, as well as imprecision and indirectness.
DISCUSSION
Although network meta-analyses are very common in health areas such as medicine and pharmacy,60–64 there are only a few available studies in the dental field.17,65,66 Perhaps this low number of network meta-analyses reflects the small number of potential treatment options compared to the innumerable drugs available in medicine and pharmacy. Nevertheless, it is a valid method for making comparisons between treatments, because it allows for the aggregation of a larger amount of evidence, either direct or indirect, which comes from large or small clinical trials.67–69 It allows the researcher to determine, among all available treatment options, which is the best18 in terms of efficacy and safety.
This systematic review and network meta-analysis was conducted to evaluate the risk and intensity of TS for different types of light activation used for bleaching. TS is the most common adverse effect reported by patients during bleaching70 and sometimes leads to treatment discontinuation.32,71 Many studies have evaluated clinical alternatives to minimize this undesirable side effect. Administration of different types of medications (non-steroidal analgesics, anti-inflammatories, corticoids, opioids), application of topical desensitizers (based on potassium nitrate or fluoride), reduction of product concentration, and use of different bleaching protocols23,50,71–74 have already been investigated.
Although in Europe the Scientific Committee on Cosmetic Products and Non-Food Products75 recommends that tooth-bleaching products should contain between 0.1% and 6.0% hydrogen peroxide, this is not a rule worldwide. Such low-concentration products can be used in-office, but they are most commonly used in at-home protocols in countries where in-office bleaching with high-concentration HP is allowed.
While some researchers focus on the investigation of alternatives to reduce bleaching-induced TS, others focus on the investigation of protocols to improve bleaching efficacy, light activation being among the possible alternatives studied so far. It is widespread knowledge that light, per se, can catalyze the decomposition of HP into free radicals, the reason this product is usually sold in dark vials. However, the increased number of free radicals is not associated with improved bleaching efficacy, as stated in previous systematic reviews of the literature,76–78 including one network meta-analysis.17
In addition to efficacy, the safety of alternative bleaching protocols requires investigation. It is desirable to know whether a bleaching protocol performed with any type of light can cause additional harm to the pulp. Theoretically, the higher quantity of free radicals produced by light activation could easily reach the pulp chamber and cause pulp inflammation79,80 and chemical irritation, which may trigger pain transmission through sensory nerves.25 Another issue that must be addressed in this discussion is that some light sources are no longer used in dentistry, such as PAC and halogen lamps. They were included in the present systematic review, however, as some clinicians may still have them in their offices. Additionally, they are important to provide improved network connectivity. Some in vitro studies have reported other disadvantages in using these light sources, such as the increase in pulp temperature, which is an additional source of damage to pulp tissue and TS.81,82
Few comparisons performed in this network meta-analysis found evidence that any type of light source was more harmful than others in terms of risk and intensity of TS, either for low- or high-concentration HP products. Network meta-analysis involves the pooling of individual study results, but the total number of trials in a network, the number of trials with more than two comparison arms, and heterogeneity may influence effect estimates.83 For more significant evidence, the nodes of a network must be well connected, because the lack of specific comparisons creates uncertainty in the results.84 This RCT highlights that there are many comparisons that lack either direct or indirect evidence, and this may serve as a research question for authors of RCTs.
Although all previous systematic reviews on this topic17,76–78 have reported that light activation does not add any benefit to the whitening outcome, they have differed in their conclusions about high-concentration HP products. He and others (2012)76 showed that light activation increases the intensity and the risk of TS during in-office bleaching, but this finding may be simply due to random bias, as few studies were eligible to be included by the time the study was conducted. Maran and others (2018)77 only observed higher levels of TS when light activation was associated with low-concentration HP. In this study, Maran and others (2018)85 compared light-activation bleaching to bleaching without light activation, thus increasing the power of the comparison and allowing the identification of a difference in the subgroup of low-concentration HP. SoutoMaior and others (2018)78 observed lower levels of TS when light activation was used, but their meta-analysis presented some methodological flaws that made their conclusions unreliable; examples include inclusion of studies with more than one effect size without accounting for the fact that the same control group was employed in both estimates, and the choice of a fixed-effect rather than random-effects model.
In the present study, different light sources were evaluated individually, while in the previous systematic review, data from different light sources were merged, increasing statistical power. However statistically significant results do not necessarily mean important clinical significance. Any small, clinically insignificant difference in effect size may be statistically significant if the sample size is large enough. Thus, care should be taken in evaluating statistically significant findings, and focus should be placed on the effect size and its precision.
The results of the present systematic review suggest that TS is neither exacerbated nor minimized by light activation with any type of light source. The amount of free radicals that reach the pulp with high- and low-concentration in-office bleaching products is already enough to reach the pulp chamber, causing cellular damage86 and TS.77 Because the quality of evidence was graded as low or very low for most of the comparisons, our confidence in the effect estimates generated is limited, because the true effect may be substantially different from what is reported here.
The reasons for downgrading the certainty of evidence are related to the unclear RoB of eligible studies and imprecision. Lack of description of how the random sequence was generated and how allocation concealment was guaranteed were the main reasons studies were considered to have an unclear RoB. The report of RCTs in accordance with the CONSORT statement87 is deficient in bleaching studies,j preventing review authors from evaluating the method of random sequence and allocation concealment. This deficiency highlights the need to conduct more rigorous studies to answer this specific research question. By using appropriate methods of randomization, allocation concealment, and examiner blinding, RCTs with low RoB may be published, producing more reliable conclusions.
Another critical topic to be evaluated in meta-analysis is the size of the statistical heterogeneity. Differences in methods, study design, study populations, the composition of materials, definitions, and measurements of outcome, follow-up, or other features make trials different,84 and therefore trials usually estimate effect sizes specific to the population they represent. If the heterogeneity is substantial, the point estimate produced by the meta-analysis may not serve as a good estimator of the effect size in different populations. Unfortunately, due to the low number of studies included in this network meta-analysis, heterogeneity in each pairwise comparison was difficult to assess, because the low number of studies produced imprecise estimates of heterogeneity.
CONCLUSIONS
We did not find evidence that the use of any type of light source causes increased risk and intensity of TS. However, for the majority of comparisons, the quality of evidence was graded as low or very low, limiting our confidence in the conclusions.
Flow diagram of study identification.
Summary of the risk of bias assessment, according to the Cochrane Collaboration tool.
Network of eligible comparisons. Risk of tooth sensitivity (TS) for: (A): High-concentration hydrogen peroxide (HP) and (B): Low-concentration HP. Intensity of TS for (C): High-concentration HP and (D): low-concentration HP.
n = number of patients in the pair comparison.
Mixed treatment comparison (MTC) results (risk ratio [RR] with 95% credible intervals [CrI]) and quality of evidence (gradings of recommendations assessment [GRADE]) for risk of tooth sensitivity (TS).
Forest plot of the evaluation of the inconsistency assumption between direct and indirect evidence used in the network meta-analysis of the risk of tooth sensitivity (TS) for bleaching with high-concentrate hydrogen peroxide (HP) with different light activation methods (p<0.05 indicates inconsistency of the pairs).
Mixed treatment comparison (MTC) results (mean difference [MD] with 95% credible intervals [CrI]) and quality of evidence (gradings of recommendations assessment [GRADE]) for intensity of tooth sensitivity (TS).
Forest plot of the evaluation of the inconsistency assumption between direct and indirect evidence used in the network meta-analysis of the intensity of tooth sensitivity (TS) for bleaching with high-concentrate hydrogen peroxide (HP) with different light activation methods (p<0.05 indicates inconsistency of the pairs).
Contributor Notes
Clinical Relevance
The use of light sources for in-office bleaching does not seem to exacerbate bleaching-induced tooth sensitivity.