The Journal of Contemporary Dental Practice
Volume 20 | Issue 11 | Year 2019

Evaluation of Light Activation on In-office Dental Bleaching: A Systematic Review

Sara Alshammery

Restorative Department, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia

Corresponding Author: Sara Alshammery, Restorative Department, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia, Phone: +966 504186949, e-mail:

How to cite this article Alshammery S. Evaluation of Light Activation on In-office Dental Bleaching: A Systematic Review. J Contemp Dent Pract 2019;20(11):1355–1360.

Source of support: Nil

Conflict of interest: None


Aim: This review was undertaken to evaluate the efficacy of light activation on in-office dental bleaching in terms of color change and photosensitivity with available literature evidence.

Materials and methods: The articles were searched from MEDLINE/Pubmed and Journal of Web, which were published from 2001 to 2019.

Results: Out of the 124 references obtained, 13 articles in English language were read in full, which fulfilled the inclusion criteria.

Conclusion: Light activation of hydrogen peroxide on in-office dental bleaching does not affect effectiveness of bleach.

Clinical significance: Though claimed that in-office bleaching activated with light betters color change, the present review did not confirm this belief.

Keywords: Color change, Dental vital bleaching, Hydrogen peroxide, In-office dental bleaching, Sensitivity.


Dental esthetics and smile play a significant factor in dental treatment seeking, resulting in patient demand for tooth bleaching. Early men too experimented with different chemicals to whiten their teeth.1 The first commercially marketed whitener was 10% carbamide peroxide used way back in 1989.2 Various products and technology are described for bleaching teeth such as differing concentrations of agents, application times, and modes and the activator used with the bleaching agent.3 Dental vital bleaching is available in three categories as in office bleaching (professionally administered), over-the-counter bleaching (self-administered), and dentist-supervised take-home bleaching (professionally dispensed). Of these, the in-office involves direct dentist’s supervision in order to avoid soft tissue trauma, gel ingestion, decreased therapy time, and to yield a rapid whitening result. Patients today desire to visualize the outcome of bleaching immediately, which has resulted in usage of higher concentrations of chemicals added as whiteners with different light sources. These are thought to accelerate the bleaching process. Various sources are used as light activating sources to activate bleaching process like Light emitting diodes (LEDs), Lasers, Plasma arc lamps (PAC) and halogen lamps. The principle of using a light source is that it heats the hydrogen peroxidase (HP), thereby increasing the HP’s disintegration into free radicals that oxidize the complex organic molecules.4

Though light activation of vital bleaching is documented in literature, the effectiveness has been questioned by many authors.46 Also, tooth sensitivity is reported in several studies due to the release of excess free radicals that reach the pulp.710 Doubts have been raised regarding the role of these activators in increasing efficiency without causing injuries to tooth, periodontium, and oral soft tissues. Hence, this review was undertaken with the objective to evaluate the efficacy of a light source on in-office vital bleaching of tooth.


An independent researcher explored the electronic databases (MEDLINE via Pubmed) and citation databases (Scopus and Web of science). Reference checks of the primary studies were made for further relevant publications. Terms used for the search were in-office bleaching, dental bleaching, vital bleaching, and light source.

Clinical studies (in vivo and in vitro) conducting in-office dental bleaching with light on adult patients, published between 2000 and January 2019, were included.

Eligibility Criteria

Clinical trials of parallel design and split mouth design, which evaluated in-office dental bleaching with or without light activation, on patients were included. Only articles in full, published in English language, were considered. Randomized trials using a combination of both home bleaching and in-office bleaching were excluded. Dissertations, theses, or abstracts in any annual conferences were not included. Articles eligible for the review were given a separate ID, comprising the first author and the year of study. Parameters of color comparison and tooth sensitivity were noted (Table 1).

Risk of Bias in Selected Studies

In order to have a quality check on selected clinical trials, two independent reviewers assessed the risk of bias using the Cochrane Collaboration tool. The assessment criteria were concealment of group allocation, blinding of outcome parameters, incomplete outcome data, and reporting only selective outcomes. Any disagreements between the reviewers were sorted through discussion. Each criterion was judged as having either a low, high, or unclear risk of bias. If all the outcomes had a low risk of bias, then the study was considered to be of low risk. If any outcome presented an unclear risk, then the authors were contacted to consider the study into either high risk or low risk.

Table 1: The characteristics of the final articles are mentioned in Table 1
StudyStudy designNo of teeth/patientsGroupsTooth evaluationBleaching procedureLight typeColor change (assessment and outcome)Tooth sensitivity (assessment and outcome)
Matis11Parallel design32 patientsEight groups, six groups with light activation and two groups without light activationVarying concentration of 15–40% HP in tray and paint on techniqueLED activationColorimeter data showed a value of 6.77 immediately after treatment All groups showed a reversal of color irrespective of HP concentration and light activation
Marson12Parallel design40 patientsGp I—35% HPAnterior teeth35% HP with a 1-week break between sessions for 6 monthsHalogen, LED, laserSpectrophotometer and vita classical shade guide
Gp II—35% HP plus halogen curing light XL 3000No difference in color stability between groups after 6 months
Gp III—35% HP plus Demetron LED
Gp 4—35% HP plus LED/laser
Calatayud13Split mouth design21 patientsGp I—H2O2 application with light activation for 10 minutesCentral incisor, lateral incisor, caninesQuick white 35% H2O2 and activation with a diode lampDiode lampClassic vita guide
Gp II—H2O2 application without light activationSlight improvement in the group with light activation
Kugel14Split arch33 patientsGp I—25% HP + light activationAnterior teeth25% HPWhite light activationPhotography
Gp II—25% HPNo difference between light-activated and chemically activated bleach
Gp III—only light activation
Hayward15Clinical study21 study subjectsIn-office bleaching followed by 14 days at home treatment11 and 21Application of 44% carbamide peroxide gel in chair with LED light activation followed by 35% carbamide peroxide gel for 14 days at homeLED lightSpectrophotometerVAS
Color change of 1.8 units after LEDSlight increase in sensitivity after LED/gel activation
Moncado16Prospective clinical trial—parallel group87Gp I—15% H2O2 and nitrogenous titanium di oxide and light activatedAnterior teethH2O2LED composed of 410 nm and 1800 mW and three IR laser diodes of 830 nm and 450 m W/cm2VAS—8.68 ±17.99. No difference in tooth sensitivity
Gp II— 35% light activated
Gp III—35% H2O2 without light activation
Janaina17Parallel study design40Gp I—35% H2O2Anterior teeth37% H2O2 with a bleaching time of 135 minutes without light activation and 72 minutes with activationLED activationReflectance spectroscopyVAS
Gp II—35% H2O2 with photothermal catalysis by LED–laser systemSimilar color and luminosities were seen after treatment in both groupsGp I presented a greater sensitivity index (37.6 ± 5.9%), while Gp II with 11.1 ± 3.31
Presoto18Case presentationOne female patient1 case - repotCentral incisorH2O2Photocatalytic equipment composed of six violet LEDs and three IR lasers (808 nm)VAS with intensity of 20% in a shock sensation with a 1-second duration at 4 days.
H2O2 with Lase peroxidase lite 6%
Park19In vitro study60 extracted human molarsGp NC—glycerin gelMolarsH2O2 gel and varnishLED lightContact-type intraoral spectrophotometer
Gp QPRO—20% hydrogen peroxide varnishColor change was lower in NC group and greater in zoom-WL group
Gp zoom-NL—25% hydrogen peroxidase gel without light activation
GP zoom-WL—25% HP gel with LED light activation
Omidi20Randomized clinical trial of parallel design60 healthy humansGp I—without light activationAnterior teethH2O2 gel of 37.5% concentrationLED and QTHSpectrophotometer
Gp II—LED light activatedNo significant difference in teeth whitening
Gp III—QTH activated
Kury21Case seriesThree casesCase 1—violet LED without peroxidase agentH2O2 and carbamide peroxide for 3–8 weeksViolet LEDSpectrophotometerVAS
Case 2—violet LED light with 37% carbamide peroxideCase 1—A2 shadeCase 1—score 0
Case 3—violet LED light with 35% H2O2Case 2—B2 shadeCase 2—score 2–3 at end of 3 weeks
Case 3—A1 shade (at the end of session)Case 3—score 3 at 3rd week end
Santos22Parallel design RCT80 patientsG1—violet LED13–23Application of H2O2 and carbamide peroxideViolet LEDVita classical digital easy shade spectrophotometerVAS—at 180 days, no tooth sensitivity reported
G2—violet LED + carbamide peroxide43–33At 2 week follow-up similar change in color
G4—violet LED + gingivoplasty
Zouiten23Case report24-year-old female patient with fluorosed teeth32% H2O2 light activation combined to an ambulatory treatment with white smile home bleachingAnteriors + premolarsH2O2SpectrophotometerVAS
Whitening effect same after 18 monthsNo photosensitivity reported after 18 months

All figures placed at the end of text


The search strategy was completed in January 2019, with duration of search lasting for 4 months (October 2018–January 2019). A total of 124 studies were identified in the database of which 22 were excluded as they did not meet the eligibility criteria of the review. Of the 102 articles obtained, 26 articles were excluded after the titles were read to include 76 articles. Of which, finally, 13 complete articles published in English language were included in the study after reading the abstract carefully, which met the inclusion criteria of the reviewer.

Nine articles were randomized clinical trial, with two following a split mouth technique and the rest were of concurrent design parallel study, three case reports, and one was an in vitro study. The different methods of in-office activation were LED activation in seven studies, a combination of halogen LED and laser in one study, use of diode lamp in one, a combination of LED and infrared (IR) laser diode in one, violet LED activation in two, and a combination of violet LED and IR laser activation in one study (Flowchart 1).

Of the 13 articles that were reviewed, color change by light activation was slightly better in only one study (Calatayud et al.). In all the other studies, there was no significant difference in the color change between any in-office bleaching activation modality. The study results did not present any association of light activation with in-office bleaching to sensitivity.


The current review aimed to evaluate the efficacy of light-activated in-office dental bleaching in terms of color change and tooth sensitivity, based on articles published between 2001 and 2019. Consensus was reached between tooth sensitivity and light activation that the latter did not result in tooth sensitivity. Out of the 76 abstracts read, 63 were excluded making the final selected articles to a total of 13. Of the 13 articles reviewed, 9 were randomized clinical trial of which 7 had parallel design and 2 had split mouth technique, 1 was in vitro study, and 3 case reports.

Flowchart 1: Literature search flowchart for systematic review on evaluation of light activation on in-office bleaching of tooth

Tooth sensitivity arises when hydrogen peroxide molecules pass through the enamel and dentin into the pulp chamber resulting in pulpal inflammation. This affects the sensory nerves, which in turn perpetuate an increased response to stimuli. Various factors that affect tooth sensitivity are dental cracks, dentin exposure, or dimensions of the pulp chamber. Tooth sensitivity in all studies was measured by a visual analog scale (VAS), ranging from 0 to 100, where 0 marks no pain and 100 presents extreme pain.

Three studies in the review used violet LED for light activation and presented no photosensitivity.22,24,25 Violet LED is used as a light source to promote bleaching instead of chemical agents. Visible violet light in the wavelength of 405 nm is used in the absence of any peroxide agent. Violet light emits photons that propagate at smaller wavelength and higher frequency, thus exhibits less penetration into the dental tissue and hence presents decreased sensitivity. This property proves to be beneficial as it promotes breakage of the large pigment chains at low heat.24,25 The lower penetration of violet LED leads to lesser molecular alteration and lesser depth operation, thus preserving the pulp.

Three studies5,17,30 used the bleaching protocol in combination with a hybrid light (LED and laser) source. Studies have shown that the time taken for bleaching with hybrid light is lesser than LED alone. This shows that shorter clinical time is required for bleaching with a hybrid light source. Frietas et al.5 reported in their study that the group with hybrid light source activation showed considerable reduction in pulp inflammation. Although the low-power laser demonstrates anti-inflammatory and biomodulation potentials, still no scientific evidence of its effect on reducing post-bleaching sensitivity is proven.

The study results did not present any association of light activation with in-office bleaching to sensitivity. This is in concordance with the results of a systematic review by Ray26 done on 11 studies that produced weak evidence to the use of light activation with in-office vital bleaching. Regardless of the HP concentration used, light activation used increased tooth sensitivity. Hypothetically, both heat and light sources accentuate the disintegration of hydrogen peroxide to form oxygen and perhydroxy free radicals, which are thought to increase bleaching efficiency.27,28

In-office bleaching has several advantages like it is a quick procedure and less riskier as performed by procedure. It also presents certain disadvantages like it is expensive and results are unpredictable as they are dependent on several factors. The final result of bleaching is dependent on patient’s age, original tooth color shade, concentration of bleaching agent, and the time factor.

A study done by Hahn et al.29 reported that light activation of HP for bleaching does not prove beneficial as the color is not stable after 3 months, and that the increase in temperature can affect pulp. Torres et al.30 also opine that though photoactivation results in fast bleaching, color regression was observed in less than a year.

The review has two elements of error owing to the subjective analysis of color assessment (shade guide) as the same evaluator can interpret different shades at different times and the objective analysis of the spectrophotometer, which can give varied results because of mirror changes.

Further studies are recommended to reach a definite consensus on the efficacy of light activation on in-office dental bleaching by using standardized protocols for research like standard concentration of bleaching material, standard application time, assessment time, and duration of the bleaching effect.


The present review provides no positive association of light activation of in-office dental bleaching with either increasing efficacy or the risk of tooth sensitivity. The result needs to be interpreted with caution considering the variations in procedure, process, and techniques (hydrogen peroxide concentration, bleaching sessions, light activation sources, and products used).


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