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 Table of Contents  
SYSTEMATIC REVIEW
Year : 2012  |  Volume : 3  |  Issue : 2  |  Page : 55-66

Evidence-based assessment of the efficacy and effectiveness of light/laser activation in in-office dental bleaching


1 Department of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles; Evidence-Based Study Group, Evidence-Based Decisions Practice-Based Research Network (ebd-pbrn.org); Biomaterials Section, Department of Conservative Dental Sciences, King Abdulaziz University Faculty of Dentistry, Jeddah, Saudi Arabia
2 Department of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles; Evidence-Based Study Group, Evidence-Based Decisions Practice-Based Research Network (ebd-pbrn.org)
3 Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, School of Dentistry, University of California, Los Angeles
4 Evidence-Based Study Group, Evidence-Based Decisions Practice-Based Research Network (ebd-pbrn.org)

Date of Web Publication3-Sep-2012

Correspondence Address:
Francesco Chiappelli
UCLA School of Dentistry, CHS63-090, Los Angeles, CA 90095

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Source of Support: None, Conflict of Interest: Chiappelli F has editorial involvement with Dental Hypotheses.


DOI: 10.4103/2155-8213.100388

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  Abstract 

Many in-office bleaching techniques use the light/laser in conjunction with the bleaching agent claiming more favorable bleaching results. Controversy still exists in the literature as to the role of a light/laser in bleaching results. The goal of this study is to determine, through Comparative Effectiveness-Efficacy Research and Analysis for Practice (CEERAP), if the co-use of light/laser activation with the chemical bleaching agent has improved teeth whitening compared to using the chemical bleaching agent alone. Systematic reviews and randomized clinical trials on the research question were obtained using multiple search engines. Assessment of the level and quality of evidence and acceptable sample analysis were performed for the Randomized Clinical Trials (RCTs). Due to heterogeneity of the acceptable studies, meta-analysis was performed only on the two most homogenous studies. Qualitative assessment of the acceptable studies was performed. The strength of clinical recommendation was assessed. Only one qualitative systematic review was found. Eight articles were accepted as high quality RCTs. The meta-analysis shows preferable outcome when using the light activation with the bleaching material than when using the bleaching material alone. Qualitative assessment of the acceptable studies shows conflicting results. Most studies agreed that the use of light is proven to increase the whitening effect of the bleaching agent, especially for a short term after treatment. Additional studies with greater consistency in methodology and outcomes are needed to be able to reach a definite consensus regarding the effectiveness of using light during bleaching through an overarching meta-analysis for more powerful statistical results.

Keywords: Evidence-based dentistry, in-office bleaching, light activated bleaching, meta-analysis, teeth whitening


How to cite this article:
Ajaj RA, Chiappelli F, Phi L, Giroux A, Maida C, Garrett N, Polinovsky O. Evidence-based assessment of the efficacy and effectiveness of light/laser activation in in-office dental bleaching. Dent Hypotheses 2012;3:55-66

How to cite this URL:
Ajaj RA, Chiappelli F, Phi L, Giroux A, Maida C, Garrett N, Polinovsky O. Evidence-based assessment of the efficacy and effectiveness of light/laser activation in in-office dental bleaching. Dent Hypotheses [serial online] 2012 [cited 2017 Mar 25];3:55-66. Available from: http://www.dentalhypotheses.com/text.asp?2012/3/2/55/100388


  Introduction Top


There continues to be increasing demand for esthetic dental treatments, with many patients seeking the so-called "Hollywood smile" or bright white smile. Dental bleaching is one of the most conservative esthetic approaches to treat discolored and/or stained teeth. For that reason, many bleaching materials and techniques are currently available, and include materials used at home by the patients or applied only in the dental office. Many in-office bleaching techniques use the light/laser in conjunction with the bleaching agent as a method to deliver heat for faster chemical decomposition of hydrogen peroxide, thus claiming more favorable bleaching results. Dental bleaching act through redox reaction (oxidation/reduction reaction), which takes place with hydrogen peroxide as the oxidizing agent that releases free peroxide radicals (HO 2 ) with unpaired electrons (O ) and becomes reduced. Lights and heating devices are claimed to accelerate the rate of bleaching but controversy still exists as to the role of a light/laser in bleaching, other than as a method of heating the material or activating a catalyst and to date, none of the light bleaching systems have ADA approval. [1]

It has been claimed that the use of light activation can accelerate the bleaching process leading to more decomposition of hydrogen peroxide to the active free radicals. [1] Hein et al. [2] tested the use of hydrogen peroxide at 30% and 35% with and without the contribution of bleaching lights (LumaArch, Optilux 500 and Zoom!). The authors reported that the 3 test lights did not lighten teeth more than their bleach gels alone and that all teeth lightened to nearly the same degree but LumaArch required 60% less time and Zoom! used 1/3 lower H 2 O 2 concentration than the other two bleaching systems. From laboratory tests, the authors indicated that the chemicals mixed into each bleach gel just before use acted as catalysts and were probably responsible for more rapid lightening produced by LumaArch gel and the need for less H 2 O 2 in Zoom! gel. The authors also indicated that neither the heat produced by the accessory lights, nor the light output itself were responsible for the catalytic activity with any of the 3 systems tested. [2]

Other studies claim that the use of the light/laser activation might increase the intra-pulpal temperature and lead to pulpal tissue damage. [3] In a systematic review, Wolfgang and Attin [3] stated that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue if the increase in the intra-pulpal temperature exceeds the critical value of 5.5°C. [3] Wetter et al. [4] concluded that in comparison with diode radiation, xenon arc lamp induced a safer temperature increase. [4] On the other hand, a study by Yazici et al. [5] showed that the increase in pulpal temperature using the Zoom! light is not significant when used for the recommended exposure time. [5]

This research will evaluate the effect of combining the light/laser activation with a bleaching agent and the degree of teeth whitening compared to the use of a bleaching agent alone. Some studies claim that they have similar end results. [6],[7],[8],[9],[10],[11],[12],[13] Kugel et al. [6] concluded that the use of light enhancement for in-office whitening led to immediate color change, after which there was a significant color and shade rebound within 7 days as well as moderate-to-severe tooth sensitivity during and after treatment. [6] Another study by Kugel et al. [7] compared the use of chemical and light-activated tooth whitening, and concluded that the use of light did not demonstrate any benefit over the chemically activated tooth whitening system after a 2-week recall. However, the light was used with 15% hydrogen peroxide and not with the higher concentration of 38% hydrogen peroxide used for bleaching agent alone. This makes this comparison unreliable or a conclusion that the same whitening effect can be achieved when using light with a lower peroxide concentration. [7] In a clinical evaluation of 35% hydrogen peroxide in-office whitening system, Papathanasiou et al. [8] indicated that the light-curing was optional with 35% tooth whitening system because there was no statistically significant difference between the light-activated and non-light-activated cases. [8] A study by Gomes et al. [9] to evaluate the influence of light exposure associated with 35% hydrogen peroxide or 15% hydrogen peroxide on the microhardness and color change of bovine enamel, concluded that the in-office bleaching outcome was not improved by using the light associated with these systems. [9] Gurgan et al. [10] evaluated the efficiency of in-office bleaching systems with different light sources for color change and possible side effects, such as tooth sensitivity and gingival irritation, and concluded that all techniques resulted in shade change that was not different among the groups, using shade guide evaluation. However, the spectrophotometer readings showed different findings. They also concluded that bleaching with diode laser resulted in less tooth and gingival sensitivity than the other bleaching systems. [10] Dietschi et al. [11] performed an in vitro colorimetric evaluation of the efficacy of various bleaching methods and products (different concentrations of carbamide peroxide home bleaching, hydrogen peroxide and carbamide peroxide power bleaching with or without light activation). They found that all products and protocols produced a similar bleaching effect on enamel; however, the home bleaching regimen proved largely superior to lighten dentin. [11] Bernardon et al. [12] concluded that the use of light irradiation did not improve bleaching efficacy. [12] Marson et al. [13] found that in-office dental bleaching treatments of vital teeth with 35% hydrogen peroxide did not prove to be more effective when light sources were used. [13]

On the other hand, other studies claimed that the use of light/laser activation have superior results. [14],[15],[16],[17],[18],[19] Sulieman et al. [14] did a comparison of three in-office bleaching systems based on 35% hydrogen peroxide with different light activator and found that the least change was noted when there was no light used. [14] Luk et al. [15] studied the effect of light energy on peroxide tooth bleaching, and reported that color and temperature changes were significant when using light and that the application of light significantly improved the whitening efficacy of some bleach materials, but caused significant temperature increase in the outer and inner tooth surfaces. [15] Ontiveros and Paravina [16] tested the color change of vital teeth exposed to bleaching performed with and without supplementary light and found that using supplementary light showed significantly greater bleaching-dependent changes in color than treatment without light when assessed using instrumental and visual methods; however, no significant difference was detected using the Vitapan Classical. [16] Tavares et al. [17] stated that peroxide and light treatment significantly lighten the color of teeth to a greater extent than did peroxide or light alone. [17] Wetter et al. [18] concluded that the use of laser has significantly better results than using the same agent alone or in combination with LED. [18] Alomari and El Daraa [19] performed a randomized clinical trial of in-office dental bleaching with and without light activation, and found that using light activation with in-office bleaching seems to increase the efficacy of treatment for a short period of time only (immediately after bleaching) but there was no significant change in long-term results (measured at one month post treatment) between the light-activated and without light groups. [19]

Ziemba et al. [20] mentioned that the use of UV light alone can cause the stain molecules (chromophores) to react on their own without the use of the chemical agent because the energy of the UV light is high enough to destroy the conjugated double bonds responsible for the discoloration. [20] This finding means that the light source can act directly, on its own, to whiten teeth and not only through the activation of the bleaching agent, which gives the use of light in whitening a dual mechanism in augmentation of teeth whitening. This was confirmed in a study by Tavares et al. [17] who used a placebo gel with light activation using short-arc gas plasma lamp emitting light in the blue-green light spectrum (400-500 nm) and found that the teeth shade did change toward lighter shades. [17] Another study by Hein et al. 2] contradicts the Tavares study, claiming that this lightening effect may be due to teeth dehydration and not the light per se, and that without knowing the exact chemistry of the placebo gel, we cannot assess its contribution to the dehydration of teeth. [2]

The goal of our study is to find out, through CEERAP, in patients with discolored teeth who are seeking in-office bleaching (e.g. after orthodontics treatment), specifically, the co-use of light/laser activation with the chemical bleaching agent, will have better whitening end-results than when using the chemical bleaching agent alone for the same concentration and application time. This formulates our PICO question where the:

Population / persons with discolored teeth who are seeking in-office bleaching, Intervention / in-office dental bleaching with light/laser activation, Comparison / in-office dental bleaching without light / laser activation and the Outcome / degree of whitening.

For this research question we state the Null Hypothesis as: there is no difference in the teeth whitening effect when using light activation with the chemical bleaching agent compared to using the chemical bleaching agent alone for in-office dental bleaching. So the Research Hypothesis would be: there is a higher teeth whitening effect when using light activation with the chemical bleaching agent compared to using the chemical bleaching agent alone.


  Materials and Methods Top


Evaluation of the hypothesis

Search strategy

The search for systematic reviews and randomized clinical trials was performed via electronic bibliographic databases using a combination of the following key words: Dental, teeth and in-office bleaching, in-office whitening, bleaching light, bleaching techniques, bleaching laser, vital teeth bleaching, light activation and external dental bleaching. To search for systematic reviews, the following search engines were explored: PubMed, Cochrane library (Cochrane reviews and other reviews), and OvidSP library. The Search for randomized clinical trials was done using the same keywords and the following search engines: PubMed, Google scholar, Cochrane library, OvidSP, and ADA website.

Determination of the relevance

The relevance of the identified systematic reviews and clinical trials to the study and PICO question was assessed using the following inclusion criteria: In-office bleaching, discolored teeth, vital teeth (external bleaching), quantified measurement of whitening, comparing the co-use of light to using the chemical bleaching agent alone, and English language studies. And the following exclusion criteria: Home bleaching, restored teeth, non-vital teeth (intra-coronal bleaching), non-quantified measurement of whitening, other non-bleaching methods to correct discoloration (e.g. veneers), no comparison between the co-use of light and the use of chemical bleaching agent alone, and non-English language studies. To further filter articles and to assure that each study fulfills the requirements for its intended use by this study, the PICO question was applied to the methodology and results of each study after applying the inclusion and exclusion criteria to ascertain adherence of each identified paper in the bibliome to the PICO question of the study.

Measurements

Assessing the level of the evidence was described in the Journal of Evidence-Based Practice.[21] For the assessment of the Quality of the Evidence, this is obtained by means of fully validated and reliable instruments, which are designed to quantify the quality of the reported research on the basis of common standard criteria of research methodology, design and statistical analysis. [22] To quantify the Quality of the Systematic Reviews to get the best available evidence of more than one systematic review, the revision of the 'assessment of multiple systematic reviews' (R-AMSTAR) instrument was used. [23] For the Quality of the Clinical Trials, the Jadad Scale[24],[25] was applied to all the relevant clinical trials where five questions were answered with "Yes" or "No" giving 1 point for "Yes" answer and 0 point for "No" answer. For each study, the score will go from 0 to 5 with scores of 0 or 1 indicating poor quality studies and scores of 4 or 5 indicating high quality studies. Another instrument used was the R- Wong Scale,[24],[26] the revised Wong scale (R-Wong) was developed by J. Wong for the evaluation of the quality of the contents of the papers using the WWH (What/Who/How) questions where the total score for each paper will thus range from 9 to 27 for clinical trials. Three readers scored the 16 relative articles and the scores, total, mean and standard deviations were calculated. To evaluate the inter-rater reliability, the correlation coefficient (r) and the amount of shared variance (r 2 ) between readers were calculated. The average (mean) score, total, mean and standard deviation across readers were also calculated. For the acceptable sampling analysis, a computer program MDAS (Medial Data Analysis System) for the Friedman test statistics for homogeneity of the non-parametric values was used. Statistically significant results would indicate that the scores among the studies are heterogeneous so we would cut off the low quality studies and get more homogenous scored studies of higher quality. The percentile rank of the cut off score was calculated using the formula: Number of scores below X/n • 100 [27] ; where: X is the selected score and n is the number of the set of scores. The MDAS program was used as a variant of the Cochran Q statistic of homogeneity of the non-parametric scores for the acceptable samples and the X 2 and p0 values were re-calculated. Meta-analysis was performed on two independent most homogenous studies to accumulate experimental and correlational results across them.

Strength of recommendation

The Grading of Recommendation Assessment, Development, and Evaluation (GRADE) Working Group developed an instrument called the GRADE system in order to grade the quality of the evidence in studies and to evaluate the strength of recommendation of the intervention at hand. [28] The GRADE looks at four factors to determine the quality of the evidence: study design, study quality, consistency, and directness. After combining the four components and assessing the grade of the evidence, the strength of recommendation of the intervention is established. [27] The GRADE, however, only makes a qualitative assessment of the evidence and does not generate quantifiable data. In a study by Phi et al., they quantified both the grading of the quality of evidence and also the strength of recommendation of the original GRADE, hence expanded the GRADE. [29] This expansion of the GRADE (Ex-GRADE) created a new instrument that could produce tangible data and possibly bridge the gap between evidence-based research and evidence-based clinical practice. [29] The Ex-GRADE was used to evaluate the strength of recommendation among the 8 acceptable studies to determine the studies with the highest confidence to adhere to and give the best clinical recommendation based on predetermined criteria by the Ex-GRADE instrument. With a total of 8 questions, the minimum total score possible a primary source or systematic review will receive is 8 and the maximum total score possible is 32. Studies with scores between 8 and 15 are weak. Studies scoring between 16 and 23 are good with some uncertainty. Studies scoring between 24 and 32 are strong. All searches were done during the period from January to March 2011. Three readers scored the eight accepted studies with the calculation of the total, means and standard deviations for the questions and the studies for each reader. The correlation coefficient of the scores for the three readers was calculated to get the amount of shared variance. The average scores of the correlated results were calculated.

For the acceptable sampling of the strength of recommendation, the Friedman test statistics for homogeneity of the non-parametric values was used using the MDAS (Medial Data Analysis System) program. Statistically significant results would indicate that the scores among the studies are heterogeneous, so there was a need to cut off the low quality studies and get more homogenous scored studies of higher quality. The percentile rank of the cut off score was also calculated using the same formula used previously.

The correlation coefficient was then recalculated using the acceptable samples to get the amount of shared variance (r 2 ). The MDAS program was used again for the Friedman test statistic of homogeneity of the non-parametric scores for the acceptable samples and the X 2 and P values were re-calculated.


  Results Top


Search results and determination of the relevance

The systematic reviews obtained from the search yielded only one systematic review which was relevant to the PICO question. This systematic review is: External bleaching therapy with activation by heat, light or laser-A systematic review. [3] [Figure 1] shows a summary of articles selection process for the systematic reviews where 111 studies were found from the initial search, 18 systematic reviews were left after removing the duplicates and one systematic review remained after applying the inclusion/exclusion criteria and PICO question. Of all the clinical trials searched, most of the articles were overlapping (duplicates) and when the results were assessed for relevance to the inclusion and exclusion criteria, eighteen total clinical trials were identified as candidates. For further determination of the relevance and to make sure that each clinical trial fulfills the requirements for its intended use by this study, the PICO question was applied as a whole to the methodology and results of each of the eighteen randomized clinical trials. [Figure 2] shows a summary of articles selection process for the randomized clinical. Sixteen RCTs were pertaining to the PICO question. These articles are:

  • Clinical Performance of Vital bleaching Techniques, by Bernardon et al. [12]
  • A Randomized Clinical Trial of In-Office Dental Bleaching with or without Light Activation, by Alomari and El Daraa. [19]
  • Clinical Trial Assessing Light Enhancement of In-Office Tooth Whitening, by Kugel et al. [6]
  • Color Change of Vital Teeth Exposed to Bleaching Performed with and without Supplementary Light, by Ontiveros and Paravina. [16]
  • Different Light-Activated In-Office Bleaching Systems: A Clinical Evaluation, by Gurgan et al. [10]
  • The Efficacy of Three Different In-Office Bleaching Systems and Their Effect on Enamel Microhardness, by Polydorou et al. [30]
  • Clinical Evaluation of In-Office Dental Bleaching Treatments With and Without the Use of Light-Activation Sources, by Marson et al. [13]
  • Clinical Evaluation of a Novel Dental Whitening Lamp and Light-Catalyzed Peroxide Gel, by Ziemba et al. [20]
  • Clinical Evaluation of Chemical and Light-Activated Tooth Whitening Systems, by Kugel et al. (2006). [7]
  • Effect of Light Energy on Peroxide Tooth Bleaching, by Luk et al. [14]
  • Clinical Evaluation of a 35% Hydrogen Peroxide In-Office Whitening System, by Papathanasiou et al. [8]
  • Light Augments Tooth Whitening with Peroxide, by Tavares et al. [17]
  • Clinical Efficacy of a Bleaching System Based on Hydrogen Peroxide with or without Light Activation, by Calatayud et al. [31]
  • A Clinical Comparison of Two Bleaching Systems, by Whitman and Simon. [32]
  • Comparison of Three In-Office Bleaching Systems Based on 35% Hydrogen Peroxide with Different Light Activators, Sulieman et al. [14]
  • In-Office Vital Tooth Bleaching-What Do Lights Add? By Hein et al. [2]
Figure 1: Summary of Articles Selection Process (Systematic Reviews) One hundred and eleven studies were found from the initial search, 18 systematic reviews were left after removing the duplicates and one systematic review remained after applying the inclusion/exclusion criteria and PICO question

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Figure 2: Summary of Articles Selection Process (Systematic Reviews) Search for RCTs was done using several search engines. More than 4000 articles were found. After removal of duplicates from each search engine, there were 1910 total studies. After removal of the duplicates from the 1910 articles, 998 articles remained. When assessed for relevance to the inclusion/exclusion criteria, eighteen total clinical trials were identified as candidates. Of the 18 articles, sixteen RCTs were pertaining to the PICO question. Eight articles remained after acceptable sampling analysis

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Measurements and quantification

Upon assessing the level of the evidence for the clinical trials, this study has level 1 good-quality, patient-oriented evidence, because of the inclusion of high-quality individual randomized clinical trials. For the Quality Assessment of the systematic review, only one qualitative systematic review was found and qualitative analysis of the randomized clinical trials was performed. To assess the quality of the clinical trial, the Jadad scale was applied to all the relevant clinical trials to assess their quality. [Table 1] shows the Jadad scale for each article. The Wong scale was the other more reliable instrument used to evaluate the quality of evidence. The three readers scored the 16 articles and for the evaluation of the inter-rater reliability, the correlation coefficient (r) between readers was calculated to be 0.89 and the amount of shared variance (r 2 ) was calculated to be 0.8. The inter-rater reliability scores for the R-Wong scale is presented in [Table 2]A. The average (mean) scores, total score for each study, and the mean and standard deviations of each question across the studies for the R-Wong instrument are presented in [Table 3]A.
Table 1: Jadad scale

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Table 2:

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Table 3:

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Data analysis

Acceptable sampling (Quality of the Clinical Trials)

Acceptable sampling analysis of the identified clinical trials in the study revealed statistical significance (Friedman X 2 = 50.98, cases = 16, df = 8; P < 0.0001) where a cut off was selected at score 18 so any article scoring below 18 will be considered as poor quality studies and are removed from the accepted samples, this score corresponded to the 50 th percentile rank. Eight out of the sixteen articles were accepted as a high quality articles. These articles are:

  • Clinical Performance of Vital bleaching Techniques, by Bernardon et al. [12]
  • A Randomized Clinical Trial of In-Office Dental Bleaching with or without Light Activation, by Alomari and El Daraa. [19]
  • Color Change of Vital Teeth Exposed to Bleaching Performed with and without Supplementary Light, by Ontiveros and Paravina. [16]
  • Clinical Evaluation of a Novel Dental Whitening Lamp and Light-Catalyzed Peroxide Gel, by Ziemba et al. [20]
  • Clinical Evaluation of a 35% Hydrogen Peroxide In-Office Whitening System, by Papathanasiou et al. [8]
  • Light Augments Tooth Whitening with Peroxide, by Tavares et al. [17]
  • Clinical Efficacy of a Bleaching System Based on Hydrogen Peroxide with or without Light Activation, by Calatayud et al. [31]
  • In-Office Vital Tooth Bleaching-What Do Lights Add? By Hein et al. [2]


The acceptable sample analysis for this group of reports selected for high quality (upper 50 percentile) revealed statistically significant difference in the scores between the articles (Friedman X 2 = 24.88, cases = 8, df = 8; P = 0.006).

Overarching statistical significance (Meta-Analysis)

For the overarching statistical significance, meta-analysis was performed on the set of independent homogenous studies to accumulate experimental and correlational results across them. Reviewing the acceptable studies, it was obvious that the designs and methodology are very divergent, which makes the studies heterogeneous and the results could not be used together in a single meta-analysis. Two among the least heterogeneous studies could be used to perform meta-analysis. The meta-analysis and the forest plot are presented in [Figure 3]. "A" represents the control group (using the chemical agent alone) and "B" is the treatment group (using light activation in conjunction with the bleaching agent). A fixed model meta-analysis was used and the forest plot shows that the analysis favors B.
Figure 3: Meta-analysis and forest plot of the 2 least heterogeneous studies. In this forest plot, "A" represents the control group (using the chemical agent alone) and "B" is the treatment group (using light activation in conjunction with the bleaching agent). This is a fixed model meta-analysis and the forest plot shows that the analysis favors B

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Strength of recommendation

The EX-GRADE

The scores were given by three readers and the correlation coefficient (r) and amount of shared variance (r 2 ) were found to be 0.89 and 0.80 respectively which means that 80% of the scores among the three readers are the same and the data are correlated. The inter-rater reliability for the strength of clinical recommendation is presented in [Table 2]B. The average (mean) of the scores of the three readers, the total score for each study, and the mean and standard deviations of each question across the studies for the Ex-GRADE instrument were calculated and presented in [Table 3]B.

Acceptable sampling for the strength of recommendation

Acceptable sampling analysis shows statistical significance (Friedman X 2 = 34.67, cases = 8, df = 7; P < 0.0001). As above, a cutoff was selected at score 21; any article scoring below 21 will be considered as poor strength of recommendation studies and will be removed from the accepted samples. This score corresponds to the 62 th percentile rank. Three out of the eight articles were accepted as having high strength of recommendation. These articles are:

  • Clinical Performance of Vital bleaching Techniques, by Bernardon et al. [12]
  • Clinical Evaluation of a Novel Dental Whitening Lamp and Light-Catalyzed Peroxide Gel, by Ziemba et al. [20]
  • Light Augments Tooth Whitening with Peroxide, by Tavares et al. [17]


Acceptable sampling of the sub-group of papers at the upper 62 percentile of strength of recommendation revealed homogeneity of the outcomes (Friedman X 2 = 13.08, cases =3, df = 7; P = 0.07).


  Discussion Top


Statistical inferences

Overarching analysis data

The data from the overarching statistical analysis (meta-analysis) on the two most homogenous studies could not be used for statistical inference because only two studies were used, which led to low power of the meta-analysis test statistics. Yet, these two studies used different light activation sources and one study was looking at bleaching effect on canines and central incisors and the other study was looking at the bleaching effect on all maxillary anterior teeth. Different teeth might respond differently to bleaching; also same teeth on different patients might respond differently to bleaching materials, which makes it difficult to quantify and generalize the bleaching effect outcomes.

Interpretation and qualitative analysis

Bernardon et al. study [12]

This article has a high strength of recommendation. This study measured the bleaching effect at 1, 2, 4, 8, and 16 weeks and did not measure the immediate bleaching effect. This might indicate that the higher bleaching effect with light is due to more dehydration due to the heat which will reverse quickly after rehydration (immediate effect only). The authors concluded that similar results were observed when teeth were bleached using in-office technique and light irradiation with both Spectrophotometer and Shade guide. The use of light should be considered optional for this technique.

Alomari and El Daraa study [19]

This study found that the use of light (other than BrightSmile® ) did not affect the initial outcome. At one month the use of light fails to improve the results. The authors concluded that using light activation with in-office bleaching seems to increase the efficacy of treatment only for short period of time, which confirms our explanation for the previous study.

Ontiveros and Paravina study [16]

This study concluded that treatment with light shows significantly greater bleaching when assessed using instrumental method and Vita BleachGuide 3D-Master and that there was no significant difference detected using Vitapan Classical shade guide. It is worth mentioning that they used different p0 value to evaluate the results using the instrumental method (0.05) than the p0 value to evaluate the results using the shade guides (0.01). Also it was mentioned that there is a conflict of interest with Vita Bleachguide 3D-Master and the University of Texas Health Science Center and Dr. Paravina. This might led to the fact that the evaluators got better training in using the Vita Bleachguide 3D-Master shade guide or that there was a bias in the evaluation to prove that this shade guide would give results more consistent to the objective method of evaluation.

Ziemba et al. study [20]

This article has a high strength of recommendation. The authors found that immediately after treatment there was significantly greater average shade change of the light group compared to the no light group. After seven days some rebound was seen and there was more rebound found in the light group compared to the no-light group. After one month there was more significant rebound seen and still it was more in the light group compared to the no light group.

Papathanasion et al. study [8]

The study concluded that the use of halogen curing light to increase the activation of 35% hydrogen peroxide is of no benefit to the dentist or the patient. Although the authors used split mouth design, they did not mention if they isolated the control side from light activation of the other side.

Tavares et al. study [17]

This article has a high strength of recommendation. The authors performed an interesting study by measuring the bleaching effect of not only the bleaching agent alone versus the light activated bleaching agent, but also the bleaching effect of light activation alone. They concluded that light augments the effect of peroxide tooth whitening and appeared to have a tooth whitening effect by itself that persisted for six months using low-concentration (15% HP). Their results contradict those of other studies, which stated that light has no effect or whether those who stated that even with greater bleaching effect when light is used, and that this bleaching effect is temporary and shade rebound happens quickly in the light activated group. They also linked their results to the rational of forbidding flash photography of artwork because curators recognized that colored surfaces are bleached when exposed to light. Whether we can relate the use of flash light in museums, where these artworks are supposed to be kept and exposed to the light effect for hundreds of years, to the bleaching of teeth after exposure to light activation for few minutes is something that can be considered.

Calatayud et al. study [31]

The authors concluded that LED lamp can increase the bleaching of HP by 0.4 units which is barely discernable by patients or by some professionals. Their results confirmed our speculation about the findings of Tavares et al. study. So even if light does have a bleaching effect on matters, which was significant statistically, is it cost-effective or noticeable? In other words, is it clinically significant? The findings and discussion of Calatayud et al. agreed that this effect is not clinically noticeable or significant.

Hein et al. study [2]

The authors compared the use of chemical bleaching agent alone to the co-use of light in three different bleaching systems, and found that all the three systems used (LumaArch, Opalescence Xtra Boost and Zoom!) lightened the anterior teeth nearly to the same degree with or without the use of light.


  Limitations Top


Previous studies limitations

There is high chance for systematic error due to low instrument reliability either using the subjective method for shade assessment (Shade guide) because even the same evaluator can give different shade assessment to the same shade at different times, or the objective method (spectrophotometer) because even minor changes in instrument position or direction can give wide variation in the results.

Also, the uncontrollable independent variables was one of the limitations as different patients and different teeth in the same patient have different susceptibility to bleaching agent, also type of food intake and life style that might affect the speed of color rebound of teeth.

There was also limited numbers of studies with valid protocol; some studies were comparing the light-activated chemical bleaching agent to non-light activated chemical bleaching agent with different chemical concentration. Studies need to use the same chemical agent in the comparison because the bleaching material concentration is one of the major factors that affect the outcome of bleaching. Other studies using the split mouth or opposite arch design did not protect the control side from the bleaching light; some studies found that light by itself can have a bleaching effect which makes it crucial to isolate the control side from light. Some studies did not use the same type of teeth in the same patient for the control and intervention groups because this will control important variables such as patient susceptibility, dentin thickness, initial shade, food intake and smoking (life style).

Study limitations

The small number of acceptable studies to be included in the analysis due to limited number of valid research and high quality research addressing this problem which will lower the power of the test statistics in case the outcomes can be combined in a single meta-analysis.

Also the wide variation of independent variables among studies in material concentration, material application time, type of light, light application time, measurement method (e.g. type of shade guide), and time of measurement (effect of relapse).

This variation and lack of standardization in the design and methodology did not allow for pooling of the outcome in single statistical meta-analysis due to the heterogeneity in the methods and designs.


  Conclusion and Recommendations Top


Conclusion

From the meta-analysis of the two most homogenous studies, it was shown that the use of light added to the effect of using the bleaching agent alone and more favorable (lighter teeth) outcomes are found when using light activation. The sample size and the inconsistency in the studies designs did not permit us to have a statistical inference from this finding.

From the qualitative analysis, the use of light is proven to have greater whitening effect when used with the bleaching agent especially for a short term after treatment. This might be attributed to teeth dehydration, which will give the tooth a lighter shade temporarily until the tooth is rehydrated by saliva soon after the bleaching session is done.

Yet the difference in shade lightening outcome between the light activated and non-light activated groups are not established to be clinically relevant even if it was statistically significant and rebound was found at one week post-treatment evaluation in most studies. Additional more consistent research is needed to determine the cost/benefit ratio.

Recommendations

Research recommendations

Additional well-controlled studies are needed to be able to reach a definite consensus regarding the effectiveness of using light with a bleaching agent to achieve overarching meta-analysis. There should be standardization in the protocol of doing research on dental bleaching light activation efficacy and effectiveness. The use of a standard concentration of the most commonly used in-office bleaching materials (35% H 2 O2 ) and the use of standard application time for both the bleaching agent and the light application is crucial. The time for measurement of the post-bleaching shade must me standardized to more than one time period and the shade must be measured immediately after bleaching and compared to the shade after multiple standard time periods of one week, one and three months. This will enable the researcher to evaluate the immediate shade change, the shade change after teeth are rehydrated and also after the three months period which is the approximate time given for the patient for the bleaching effect.

It is important to have more than one evaluator with testing the consistency of their evaluations and to test the reliability of the shade evaluation for each evaluator to reduce the chance of inter-rater and intra-rater variations respectively. When using the spectrophotometer it is important to make sure to reproduce the direction and distance of the instrument and to test the reliability of the readings. The participants in the research should be advised for the type of diet intake that might affect the speed of rebound of the color of the teeth and smoking should be prohibited or at least reported in the studies.

Clinical recommendations

Up to date, the use of bleaching lights did not prove to have superior whitening effect than using the chemical bleaching agent alone due to paucity of the evidence. Most of the added benefit of using the light and laser was shown to be immediately after bleaching and tooth shade rebound was recorded at the first week in most of the studies. Light-activated bleaching is a safe method as long as it was applied and performed following the manufacturers' instructions and proven by some studies to have superior teeth lightening effect temporarily after bleaching.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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