World Journal of Dentistry
Volume 15 | Issue 1 | Year 2024

Evaluation of Two in Office Bleaching Systems with and without Laser Activation: An In Vitro Study

Sumarlangki Sayoo1, Narayanaswamy Shubhashini2, Vinaya K Ramachandra3, Annapoorna Kini4

1Woodland Hospital, Shillong, Meghalaya, India

2,4Department of Conservative Dentistry & Endodontics, RajaRajeswari Dental College & Hospital, Bengaluru, Karnataka, India

3Department of Periodontology, RajaRajeswari Dental College & Hospital, Bengaluru, Karnataka, India

Corresponding Author: Vinaya K Ramachandra, Department of Periodontology, RajaRajeswari Dental College & Hospital, Bengaluru, Karnataka, India, Phone: +91 9844301016, e-mail: drrvinayakumar@gmail.com

Received: 06 December 2023; Accepted: 07 January 2024; Published on: 20 February 2024


Aim: To compare and evaluate the efficacy of two in-office bleaching systems with and without laser activation.

Materials and methods: A total of 75 extracted anterior teeth were collected, cleaned, and stored in distilled water at 37°C for 60 days. The specimens were artificially stained using a tea solution. The solution was renewed each day, and the specimens were stained to a uniform shade of C4 as judged visually and by a spectrophotometer. The teeth were divided into five groups of 15 each—group I, control group; group II, bleaching using Pola Office bleaching system; group III, bleaching using Opalescence Boost; group IV, Pola Office activated with diode laser; and group V, Opalescence Boost activated with diode laser. The color evaluation was done both prior to and after the procedure and the resultant data was subjected to statistical analysis.

Results: The multiple comparisons of the mean difference of ∆E between groups, showed that group II (p = 0.002) and III (p = 0.003) showed a significantly lesser mean ∆E value as compared to group IV (p = 0.007), and V (p = 0.03). Similar results were observed for L values. For C and H, group III demonstrated better results followed by groups V, II, and IV.

Conclusion: Within the limits of this study, groups with laser activation demonstrated greater improvement in color for the evaluated parameters compared to groups without laser activation with the Opalescence Boost and laser group showing the best results.

Clinical significance: Lasers can serve as valuable adjuncts to traditional bleaching techniques as they significantly enhance the results.

How to cite this article: Sayoo S, Shubhashini N, R VK, et al. Evaluation of Two in Office Bleaching Systems with and without Laser Activation: An In Vitro Study. World J Dent 2024;15(1):53–59.

Source of support: Nil

Conflict of interest: None

Keywords: Diode laser, Opalescence boost, Pola office, Spectrophotometry, Vita Shade Guide


The whitening of tooth color through the application of a chemical agent to oxidize the organic pigmentation is referred to as “bleaching.”1 Discolored teeth, especially in the anterior region can result in considerable cosmetic impairment.2 It is important to identify the cause and manage the discoloration accordingly.3 The causes of tooth discoloration are usually varied and multifaceted.4 The most commonly encountered tooth discoloration is due to fluorosis which is caused by an excessive intake of fluoride during formation and calcification of enamel.5 Discoloration can be classified as extrinsic, intrinsic, or internalized.4 Extrinsic discoloration is caused by the deposition of external chromogens (i.e., metallic ions, tea, coffee, and tobacco) on the tooth surface or within the pellicle layer that adheres to the enamel surface. Intrinsic discoloration occurs when the chromogens are deposited within the bulk of the tooth, usually the dentin, and caused by systemic or pulpal origin. Extrinsic stains occasionally permeate into the tooth substance through a defect of the tooth, thereby causing intrinsic discoloration.6 Internalized discoloration results from a number of factors such as developmental defects, caries, and restorative materials.4

This study deals with tea-induced extrinsic tooth discoloration. Organic chromogens, such as tannins present in tea are taken up by the pellicle and cause staining with the color imparted being the chromogen’s natural color.4

The dentist’s intervention is largely essential for treating substantial tooth discoloration.3 Tooth discoloration can be treated by different treatment approaches starting from the least invasive method; such as whitening toothpaste, and professional cleaning (scaling and polishing) to remove surface stains and internal bleaching of nonvital teeth. More aggressive methods include external bleaching of vital teeth, microabrasion of enamel with abrasives and acids, macroabrasives, and crowns or veneers. Bleaching is one of the least aggressive modalities that has gained popularity.7

Oxalic acid was initially used to bleach teeth in 1848, and hydrogen peroxide (H2O2) was added in 1884.3 In 1916, Dr Walter Kane used hydrochloric acid to effectively remove fluorosis stains. Ames reported that H2O2 could be used as an alternative for eliminating fluorosis.8 McInnes outlined a technique where a combination of H2O2, hydrochloric acid, and ethyl ether was successfully used for bleaching the teeth of patients with endemic fluorosis.9 At-home bleaching involves the application of bleaching agents that liberate low levels of H2O2. Carbamide peroxide is a well-accepted agent for home-use bleaching supervised by a dentist. In contrast, in-office bleaching employs much higher levels of H2O2 (55%) for a short duration.10,11

By the early 20th century, in-office vital bleaching evolved to include the use of heat/light for activation of the process.12 Photooxidation is the technique of triggering whitening using light, and it can be carried out using plasma arc lamps, halogen bulb equipment, and lasers.13 Employing laser-assisted bleaching halved the treatment time mentioned by the manufacturer.14 Most patients are obsessed with saving time and obtaining rapid results. Therefore, to increase the rate at which oxygen breaks down to produce oxygen free radicals and to speed up the release of stain-containing molecules; heat, light, or lasers are applied to the bleaching agent to increase its temperature. This stimulates and catalyzes the bleaching process. Laser fundamentally differs from other light sources in that it emits a single-wavelength, well-defined monochromatic light that decreases the risk of increasing pulpal temperature. Laser bleaching can be accomplished in a single in-office visit while allowing one to target a particular tooth or even a chosen part of a tooth. Argon, carbon dioxide, and diode lasers have been approved for bleaching by the Food and Drug Administration.13

Diode is a solid active medium laser, manufactured from semiconductor crystals using some combination of aluminum or indium, gallium, and arsenic. The available wavelengths for dental use range from about 800 nm for the active medium containing aluminum to 980 nm for the active medium composed of indium.15 Diode lasers act by photothermal catalysis resulting in a reduction of H2O2 to oxygen and water and preferably release of perhydroxyl radicals from the bleaching gel providing effective bleaching. The use of diode lasers for bleaching is widely supported by literature.16,17

Opalescence Boost is an in-office bleaching system that contains 40% H2O2 whitening gel, chemically activated through easy syringe-to-syringe mixing. It contains potassium nitrate and fluoride that’s been proven to lower sensitivity, reduce caries susceptibility, and improve the microhardness of the enamel and also contains red pigments in the form of carotene.18,19 Pola Office is another in-office bleaching system that contains 35% H2O2. It is a neutral pH gel, contains desensitizers to maximize patient comfort, and requires minimal chair time.20 However, there are few studies in the literature that have compared the bleaching capability of the two systems especially with adjunctive laser application.

Our null hypothesis was that laser application did not enhance the bleaching ability of the above bleaching systems. Hence, the present study aims to evaluate and compare the bleaching efficacy of Pola Office and Opalescence Boost with and without laser activation.


This in vitro, experimental study was carried out from June to September 2020. The study was approved by the Institutional Ethics Committee (RRDCHET/02CON/2018). Sample size estimation for the present study was performed at 5% α-error with an effect size of 0.42 and 80% power using G*Power software (Version; Düsseldorf, Germany). A total of 75 anterior teeth extracted for orthodontic or periodontal reasons were collected from the Department of Oral and Maxillofacial Surgery of the hospital. The inclusion criteria were teeth free of caries, fractures, or restorations.

The teeth were cleaned of debris and calculus and stored in distilled water at 37°C till the period of study. Color evaluation was done before and after bleaching, using two different methods—Standard Vita Shade Guide (VITAPAN Classical, VITA Zahnfabrik, Bad Säckingen, Germany) and Spectrophotometer (VITA Easyshade V, VITA North America, California, United States of America). The Standard Vita Shade Guide is a subjective and visual method of evaluation. All shade correlations prior to and postbleaching were performed by the researcher using the above. Conversely, a spectrophotometer is an objective, instrumental method of shade matching and is favored over visual evaluation, as it makes the process more practical and statistically reliable. The spectrophotometric assessment of samples was based on the CIE L*a*b* system. The International Commission on Illumination expounded this system in 1967 and it’s referred to as CIE Lab. The color comparison before and after treatment is given by the dissimilarities between the two colors (ΔE), which is computed using the formula:

The specimens were artificially stained using a tea solution. The tea was prepared by boiling 2 gm of loose tea (Brooke Bond Red Label, Hindustan Unilever Limited, India) in 100 mL of distilled water for 5 minutes followed by filtering with gauze to remove the tea from the infusion. The tea solution was renewed each day, and the specimens were stained to a uniform shade of C4 as judged visually and by a spectrophotometer. The teeth were then divided into five groups of 15 each and the following treatment protocol was applied; group I, control group—no bleaching done; group II, bleaching using Pola Office bleaching system (SDI Limited, Victoria, Australia)—in this group a 1–1.5 mm thick layer of Pola Office gel was applied on the teeth, left for 15 minutes after which the gel was suctioned; and group III, bleaching using Opalescence Boost (Ultradent Products Inc., Utah, United States of America)—in this group, the Opalescence Boost was applied about 1–1.5 mm thickness approximately. For optimum effectiveness it was stirred or agitated every 5 minutes and left on the teeth for 15 minutes after which the gel was suctioned, group IV, Pola Office activated with a diode laser (Photon, Zolar Technology & Manufacturing Co. Inc, ON, Canada)—in this group the Pola Office was applied as above and irradiated with a diode laser (810 nm) at a power of 2 W for 60 seconds (two cycles of 30 seconds each) in noncontact mode and group V, Opalescence Boost activated with diode laser—in this group Opalescence Boost was applied and irradiated with a diode laser (810 nm) similar to the protocol followed in group IV (Flowchart 1).

The data thus derived was statistically analyzed (Fig. 1).

Flowchart 1: Consolidated Standards of Reporting Trials (CONSORT) flowchart

The data thus derived was statistically analyzed (Fig. 1).

Fig. 1: Mean “L” values among the study groups prior to and after bleaching

Statistical Analyses

The results were statistically analyzed with Statistical Package for the Social Sciences (SPSS) for Windows, Version 22.0. Released 2013. Descriptive analysis included expression of the different study parameters in terms of mean and standard deviation (SD).

Inferential Statistics

The Kruskal–Wallis test followed by the Mann–Whitney post hoc test was used to compare the mean values of different parameters between study groups before and after the bleaching procedure. Wilcoxon signed-rank test was used to compare the mean values of different parameters between, before, and after bleaching procedures in each study group. The level of significance (p-value) was set at p < 0.05.


Table 1 depicts mean ∆E, L, C, and H values between different study groups before bleaching using the Kruskal–Wallis test which shows no significant difference between the five groups for any parameter.

Table 1: Comparison of mean values of the different parameters among the study groups before bleaching
Comparison of mean values of different parameters between five groups before the bleaching procedure using the Kruskal–Wallis test
Parameters Groups N Mean SD Minimum Maximum p-value
ΔE Group I 15 9.05 5.30 3.6 19.3 0.99
Group II 15 8.57 2.95 5.5 14.8
Group III 15 8.09 4.40 1.7 14.9
Group IV 15 8.66 4.47 2.2 15.9
Group V 15 8.75 3.11 3.0 13.6
L Group I 15 3.19 4.35 −5.3 7.6 0.23
Group II 15 1.91 3.18 −5.5 5.1
Group III 15 1.95 4.63 −8.1 8.6
Group IV 15 1.47 3.71 −4.0 8.3
Group V 15 2.27 2.06 −2.8 4.5
C Group I 15 7.11 5.85 0.7 17.5 0.59
Group II 15 7.49 3.18 2.3 13.1
Group III 15 6.54 4.08 −6.4 10.9
Group IV 15 7.23 5.29 −8.0 14.8
Group V 15 7.27 3.35 0.3 12.2
H Group I 15 −7.72 4.37 −17.8 −0.4 0.19
Group II 15 −9.51 3.03 −14.3 −5.2
Group III 15 −10.11 4.66 −16.5 2.5
Group IV 15 −6.53 6.63 −13.7 10.0
Group V 15 −8.93 3.09 −12.1 −0.1

*, statistically significant

The ∆E value represents the difference in color with lower values signifying less color difference and higher values representing greater difference. All four study groups demonstrated a statistically significant difference in ∆E values after the bleaching procedure (p = 0.004). Groups II and III showed lower mean ∆E values when compared to groups IV and V. The Mann–Whitney post hoc test was employed to compare the mean ∆E values between the four groups following bleaching. A significant difference in ∆E values was noted between groups II and IV (p = 0.002) as well as between groups III and V (p = 0.03). However, the differences were not significant between groups II and III and IV and V (Table 2).

Table 2: Comparison of mean values of the different parameters among the study groups after bleaching
Comparison of mean values of different parameters between the four groups after the bleaching procedure using Mann–Whitney post hoc analysis
Parameters (I) group (J) group Mean difference (I–J) 95% CI for the difference p-value
Lower Upper
ΔE Group II Group III 0.48 −3.34 4.30 0.55
Group IV −3.06 −6.88 0.76 0.002*
Group V −3.66 −7.48 0.16 0.03*
Group III Group IV −3.54 −7.36 0.28 0.007*
Group V −4.14 −7.96 −0.32 0.03*
Group IV Group V −0.60 −4.42 3.22 0.88
L Group II Group III −1.22 −5.16 2.72 0.12
Group IV −2.77 −6.72 1.17 0.006*
Group V −3.92 −7.86 0.02 0.009*
Group III Group IV −1.55 −5.50 2.39 0.14
Group V −2.70 −6.64 1.24 0.04*
Group IV Group V −1.15 −5.09 2.80 0.48
C Group II Group III 3.76 0.83 6.69 0.001*
Group IV −1.03 −3.95 1.90 0.38
Group V 0.43 −2.49 3.36 0.34
Group III Group IV −4.79 −7.71 −1.86 <0.001*
Group V −3.33 −6.25 −0.40 0.009*
Group IV Group V 1.46 −1.47 4.39 0.18
H Group II Group III −4.98 −7.69 −2.27 0.002*
Group IV 0.47 −2.24 3.18 0.82
Group V −3.10 −5.81 −0.39 0.005*
Group III Group IV 5.45 2.75 8.16 <0.001*
Group V 1.88 −0.83 4.59 0.25
Group IV Group V −3.57 −6.28 −0.87 <0.001*

*, statistically significant

The “L” represents lightness or darkness with higher values representing greater difference. A statistically significant difference in L values was observed in all the study groups after bleaching (p = 0.008). Again, groups II and III showed lower mean L values compared to groups IV and V (Fig. 1). Multiple comparisons of mean L values between the study groups following bleaching revealed a significant difference between groups II and IV (p = 0.006) and groups III and V (p = 0.04) while groups II and III and groups IV and V did not demonstrate a significant difference (Fig. 1 and Table 2).

The “C” stands for chroma and refers to the strength or intensity of a color. All of the study groups exhibited a statistically significant reduction in C value following bleaching (p = 0.001). Group III showed the greatest reduction in chroma when compared to the other groups (Fig. 2). Mann–Whitney post hoc analysis revealed significant differences in C values between groups II and III (p = 0.001), groups III and IV (p < 0.001), and groups III and V (p = 0.009) (Fig. 2 and Table 2).

Fig. 2: Mean “C” values among the study groups prior to and after bleaching

The “H” is a hue and is one of the main properties of a color. As with the other evaluated parameters, there was a significant difference in the H value postbleaching. Group III demonstrated the greatest change in hue in comparison to the other groups (Fig. 3). Multiple comparisons of H values between the four groups showed significant differences between groups II and III (p = 0.002), groups II and V (p = 0.005), groups III and IV (p < 0.001) and groups IV and V (p < 0.001) (Fig. 3 and Table 2).

Fig. 3: Mean “H” values among the study groups prior to and after bleaching

Overall, with respect to ∆E and L, group V showed the best results followed by groups IV, III, and II. With regards to C and H values, group III exhibited the best outcomes followed by groups V, II, and IV.


In recent years, tooth discoloration has become a frequent cosmetic complaint. A growing number of patients seek dental consultation for tooth whitening procedures, fueled by their esthetic desires.21 Whiter teeth are believed to be associated with health and beauty resulting in patients insisting on “the perfect smile.”7

There are two main methods of dental bleaching; home applied and in-office.22 In dentistry, bleaching usually employs products containing some form of H2O2.5

At-home bleaching is the most extensively tutored bleaching technique and exhibits a high success rate.23 The at-home bleaching technique for teeth with vital pulp has been used for many decades; however, it was only in 1989 that Haywood and Heyman presented the whitening method with 10% carbamide peroxide gel.24 At-home dental bleaching is a conservative treatment of pigmented or stained teeth. The most frequently used substance in the at-home application is carbamide peroxide, which dissociates into H2O2 and urea. At-home bleaching can be achieved by using tooth bleaching materials containing up to 20% carbamide peroxide and 10% H2O2.11 This technique has the advantages of self-administration by the patient, less in-office time, high safety, low adverse effects, and low-cost.25 The at-home protocol requires the use of a bleaching tray and a waiting period of 2–3 weeks to see the treatment outcome which can affect patient concurrence. Further, inadequate patient compliance with the daily use of a bleaching tray that is not under the dentist’s control may increase treatment duration and costs. Patients also need to be diligently supervised in other clinical situations, such as the presence of extensive tissue recession or deep unrestored abfraction lesions.26

Compared with home bleaching, in-office bleaching has advantages in terms of clinician control, quick whitening results, reduced treatment time and avoidance of material ingestion and discomfort from wearing trays, avoidance of soft-tissue exposure, and greater prospect for immediate results augmenting patient motivation and satisfaction.27 High concentrations of carbamide peroxide (35–37%) and H2O2 (30–35%) are used as sources of oxidizing agents for professional use in the office.11 This can result in significant bleaching results after only one session.28 However, when increased concentrations of bleaching agents are used with longer application time or for multiple treatment sessions the risk of tooth sensitivity or gingival irritation exists.29,30 H2O2 can be used in its pure form or as the breakdown product of other bleaching agents such as sodium perborate and carbamide peroxide.31 One of the most accepted theories on the mechanism of action of bleaching agents is that free radicals liberated from H2O2 attack organic molecules and set them into a stable condition. This causes other free radicals to react with unsaturated chemical bonds and alter their electron arrangement and therefore transform the energy absorption of organic molecules. These changes in energy absorption create simpler molecules that reflect less light and therefore make enamel appear brighter.32

In-office bleaching agents can be activated by light or heat.33 Light emitting long wavelengths have lower energy photons with a high thermal character and these may induce unfavorable thermal effects. Shorter wavelengths such as the argon lasers or potassium titanyl phosphate (KTP) lasers have higher energy photons with less direct thermal characteristics. Thus, KTP lasers, argon, and diode lasers are commonly used for in-office bleaching treatments.5 Since in-office bleaching alone increases the chairside time, many studies were attempted where laser or light activation was used to accelerate the activation of the bleaching gel. Luk et al. reported that the interaction of the bleaching agent with light variables significantly affected color change and opined that the whitening efficacy of some bleaching materials was significantly improved by the application of light.28

With this rationale, our study aimed to compare the two in-office bleaching systems with and without laser activation. Dental lasers are a relatively novel treatment approach for teeth bleaching and are considered to be the most prized energy source for power bleaching with a simple and short application time.34 Moreover, the procedure can be completed in a single treatment visit. The choice of wavelength is based on the light–target tissue relationship. The bleaching gel, on the one hand, should absorb the laser light and the tooth structure, and on the contrary, should be minimally affected. Therefore, photo-initiators or dyes are incorporated, which are adjusted to absorb the wavelength of the light source used.35 Domínguez et al. examined the whitening efficacy of three whitening agents in combination with six different photoactivation systems. They concluded that only the groups that were photoactivated using a diode laser, halogen lamp, and light-emitting diode (LED) showed statistically significant differences (p = 0.005) in color change when compared with the control groups (without photoactivation).36 Another study by Bennett and Walsh compared the efficacy of LED and KTP laser when used in photodynamic bleaching of tetracycline-stained dentine. They observed that the KTP laser was superior to the LED array when used to activate the photodynamic bleaching gel system.37

However, the literature also contains studies that have shown no additional benefit of laser-activated bleaching when compared with the conventional bleaching technique. Hein et al. reported no difference in the whitening effect of bleaching gels [25–35% water (H2O2)] with or without three different lights (LumaArch, Optilux 500, and Zoom). They surmised that lights had no impact on the process as proprietary chemicals incorporated in the bleaching gels acted as catalysts in the whitening process and were wholly responsible for activation.38 Similarly, Hahn et al. could not find an improvement in tooth whitening as a result of LED or laser light treatments, when evaluating the color stability of bleaching with Opalescence XtraBoost (38% H2O2) using four different methods—activation with halogen, LED, laser or chemical activation.39

Son et al. have noted that diode laser irradiation improved the whitening effect of H2O2.40 Hence, we undertook this study to compare the bleaching efficacy of Pola Office and Opalescence Boost with and without diode laser activation. The extent of whitening pre- and post-bleaching was assessed using a spectrophotometer and Vita Shade Guide. In our study, groups IV and V where laser-activated bleaching was employed fared better overall in all the parameters evaluated when compared to groups II and III which did not employ the laser. Thus, the results of our study seem to lean more in favor of laser-assisted bleaching. A study by Fekrazad et al. can be cited in support of this claim. The authors compared the efficacy of power bleaching using Opalescence Xtra Boost and the laser bleaching technique using laser smile gel and diode laser as activators. They concluded that both laser-assisted and power-bleaching techniques were capable of altering tooth color, but laser bleaching was deemed to be a more efficient technique in this regard.41

The plausible reasons why laser and Opalescence Boost groups exhibited better efficacy in bleaching could be attributable to the reasons that follow. In general, lasers enhance bleaching by photooxidation of colored molecules in teeth or by interaction with components of the bleaching gel through photochemical reactions.42 Further, diode lasers are more effective when used on a darker medium. As the bleaching gel in Opalescence Boost is darker than the Pola Office gel, better outcomes were noted in the former group.


The key factors in determining the whitening of teeth with the bleaching systems available are the duration of application and peroxide concentration. The systems used in this study contained H2O2 in concentrations of 35–40%. Within the limits of this present study, laser-assisted bleaching was found to exhibit better results when compared to conventional bleaching thus rejecting our null hypothesis.

Clinical Significance

Thus, lasers can be employed adjunctively with bleaching agents to significantly enhance their effects. A few limitations of this study could be the limited sample size and the in vitro design. However, more long-term in vivo studies need to be undertaken employing different compositions and concentrations of bleaching agents along with different application times in order to develop a standardized protocol for in-office laser-assisted bleaching while minimizing its side effects. This will go a long way in developing the best possible treatment protocol for tooth bleaching and ensuring satisfied patients.


This work should be credited to the Department of Conservative Dentistry and Endodontics in RajaRajeswari Dental College and Hospital, Bengaluru, Karnataka, India.


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