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Year : 2013  |  Volume : 7  |  Issue : 2  |  Page : 54-58

Clinical evaluation of laser bleaching vs. conventional in-office bleaching

Department of Prosthodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India

Date of Web Publication3-Jan-2014

Correspondence Address:
Rajeev Milen Mariam
Department of Prosthodontics, PMS College of Dental Science and Research, Venkode Post Office, Golden Hills, Vattapara, Thiruvananthapuram - 695 028, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-2868.124265

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Aims and Objectives: The purpose of this study was to objectively evaluate and compare the clinical efficacy of an in-office bleaching system using a titanium dioxide impregnated bleaching gel in conjunction with an 810 nm diode laser as opposed to a conventional in-office bleaching system. Settings and Design: The study was conducted in the Department of Prosthodontics, PMS College of Dental Science and Research, Vattapara. The study is an observational study of experimental design. Materials and Methods: Ten subjects were screened based on the inclusion and exclusion criteria. Resin dam was applied onto the gums and the teeth are isolated. Opalescence boost bleach gel is applied onto two quadrants of each patient, one with titanium dioxide and exposed to 810 nm GaAlAs diode laser and the other quadrant with conventional in-office bleaching using the same agent in trays. Comparison and assessment of degree of whitening between quadrants (and thereby techniques) was done using a Vita Shade guide. The dentinal hypersensitivity was assessed by means of air stimulus. Statistical Analysis Used: Non-parametric test (Wilcoxon signed test), was used to compare the effect of laser bleaching and conventional in-office bleaching based on visual analog score (VAS) score. To compare the shade difference McNemar test was used. Results: Statistically significant value, Z = 2.831 was obtained which proved that laser bleaching had significantly less sensitivity compared to conventional in office bleaching. McNemar test obtained a P value 1, showed that there is absolutely no difference in the brightness obtained by both laser bleaching and conventional in-office bleaching. Conclusions: Laser energy is able to effect physicochemical changes in enamel this is affected by crystalline changes within hydroxyapatite crystal and by the removal of the organic content or carbonate in the intercrystalline areas. Such changes also protect against the harmful effects due to extensive penetration of hydroxyapatite. Diode laser 810 nm has been shown to have effected such changes in bleaching settings.

Keywords: Laser bleaching, sensitivity, titanium dioxide, visual analog scale

How to cite this article:
Mathews MA, Mariam RM, Sudeep S, Dinesh N. Clinical evaluation of laser bleaching vs. conventional in-office bleaching. J Dent Lasers 2013;7:54-8

How to cite this URL:
Mathews MA, Mariam RM, Sudeep S, Dinesh N. Clinical evaluation of laser bleaching vs. conventional in-office bleaching. J Dent Lasers [serial online] 2013 [cited 2024 Feb 26];7:54-8. Available from:

  Introduction Top

Laser energy is a relatively novel approach for teeth whitening and presents some advantages over most available over-the-counter, home, and in-office bleaching procedures like markedly reduced chair time, inducing microcrystalline changes in the enamel and dentin providing the patient the advantage of little or no intraoperative and postoperative sensitivity and furthermore, resistance of the teeth involved to acidogenic environs and caries.

The aim of the study was to evaluate and compare clinically the efficacy of in-office bleaching system with diode laser activated bleaching system for tooth whitening, and to assess subsequent dentin hypersensitivity (DH). The objective of laser bleaching is to achieve tooth whitening using the most efficient energy source, while avoiding any adverse effect.

  Materials and Methods Top

The study population consists of 10 people, who required bleaching. The subjects were selected based on the following criteria.

Inclusion criteria

  • Patients in good systemic health
  • Patients who were willing to participate in the study.

Exclusion criteria

  • Teeth with intrinsic stains like tetracycline stains
  • Teeth with cracked structures, carious lesions, restorations, nonvital, and active periodontal disease
  • Patients with chronic or debilitating disease with daily pain episodes; those who were taking any analgesic, anticonvulsive, antihistaminic, sedative, tranquilizing, or anti-inflammatory medications in the 72 h preceding treatment
  • Those who had used any desensitizing toothpaste or mouthwash in the last 3 months.

The subjects were screened based on the inclusion and exclusion criteria. Shade was selected and recorded prior to the procedure. Resin dam or a quick dam was applied onto the gums to isolate the teeth. Opalescence office bleach is applied onto two quadrants of each patient, one with titanium dioxide which acts as a chromophore to absorb the laser beam from a 810 nm GaAlAs diode laser, 5 W power, continuous wave for three continuous cycles 10 s each and in the other quadrant the bleaching agent was applied directly without any photoactivator and was stimulated with light-emitting diode (LED) light source. DH is assessed by means of air stimulus and the shade is checked after the procedure and also recorded.

Dentin hypersensitivity sssessment

A visual analog scale (VAS) is used to measure DH. All patients are asked to define their level of DH by using a VAS consisting of equal units from 0 to 10 (a line of 10 cm). On this scale, 0 and 10 represented 'no pain/discomfort' and 'worst pain/discomfort imaginable', respectively. All pain assessments are performed in the morning in the same clinic, free of extraneous noise, music, or conversation. Patients are asked to mark the degree of pain they experienced by directing an air blast to the tooth surface before and after bleaching by each modality. Before and after each session, the patient is given a separate sheet of paper containing the printed interval scale (a line of 10 cm) so that he or she will not be influenced by the previous results. Data from the VAS are recorded by measuring in millimeters the distance between zero point and the sign marked by the patient on the 10-cm line [Figure 1].
Figure 1: Visual analog scale

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  Results Top

After compiling the results of the study we found that out of 10 subjects, most of them gave a VAS score of 4-5 in case of conventional bleaching system [Table 1] and [Table 2], with a significant improvement in tooth whitening [Figure 2]; whereas in case of laser bleaching, the VAS score was recorded in the range of 1-2, with similar significant improvement in tooth whitening [Figure 3] and [Figure 4]. Nonparametric test (Wilcoxon signed test), used to compare the effect of laser bleaching and conventional in-office bleaching based on VAS score. Statistically significant value, Z = 2.831 was obtained which proved that laser bleaching had significantly less sensitivity compared to conventional in-office bleaching. To compare the shade difference McNemar test was used and obtained a P value 1, showed that there is absolutely no difference in the brightness obtained by both laser bleaching and conventional in office bleaching.
Figure 2: Bar diagram showing shade change using both the techniques

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Figure 3: Pie chart shows shade difference in patients in laser bleaching

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Figure 4: Pie chart showing shade difference in patients in conventional bleaching

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Table 1: Depicts the VAS score and change in shade after laser bleachingss

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Table 2: Depicts the VAS score and change in shade after conventional bleaching procedure

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  Discussion Top

The use of hydrogen peroxide for conventional bleaching was introduced way back in 1884, today bleaching products are often found in the form of gels containing various concentrations of carbamide peroxide and hydrogen peroxide depending upon the application and methods. Over the years the disadvantages of conventional bleaching system can be summated as that it can cause cervical root resorption, increased teeth sensitivity, alteration of the surface topography and microhardness, decreased bond strength of the resin based restorative materials, and furthermore it can even be carcinogenic or it has tumor promoting capabilities. [1] Enamel demineralization after bleaching with 10% carbamide peroxide showed lower Ca: P ratio on the enamel surface, though microhardness was not significantly affected, an increased number of pores with large diameter had enhanced the adhesion and permeability of cariogenic bacteria. [2],[3] Peroxide containing bleaching agents affects the organic phase of enamel, on the surface and the inner structure, which led to porosity due to the penetration of hydrogen peroxide along enamel proteins. [4]

In conventional bleaching, 30-35% hydrogen peroxide is used commonly for power bleaching, which gets converted to superoxide (O 2 ), hydroxyl (OH), peroxyl (ROO), and alkoxyl (RO) ions. These by products are neutralized by three enzymes namely catalase, glutathione, and superoxide dismutase. But these enzymes which serve as a vanguard of protection against the harmful effect of these oxidative states are in scarce concentrations in the pulp. Ten percent carbamide peroxide is better than 30-35% hydrogen peroxide, however it constituently splits into 7% urea and 3% hydrogen peroxide. The larger core of urea, serves to mitigate the acidic effect of hydrogen peroxide by the production of carbon dioxide and ammonia, however it also has an adjuvant effect that helps in compensating for the meager 3% hydrogen peroxide by softening the enamel proteins such as enamelin and amelogenin, which lie in the interprismatic area of the enamel. Enamel contains 96% inorganic and 4% organic; this allows the penetration of the hydrogen peroxide to the deeper layers. This penetration to the deeper layers is not self-limiting, and may even reach the pulp, the pulp do not have the previously mentioned enzymes (catalase, glutathione and superoxide dismutase), this can lead to pulpal damage and ultimately dentinal sensitivity or even non vitality of the pulp, this could be explained by the theory proposed by Hsu et al. [5] When laser is directed on the tooth structure, as in bleaching procedure, the enamel proteins are denatured, concomitantly the infrared laser energy at 810 nm wavelength affects microcrystalline changes within the tooth structure. This proves beneficial in improving the resistance of the tooth to cariogenic attacks/acidogenic environment.

Other theories such as alteration of chemical composition (Stern and Sognnaes) stated that when laser is applied on enamel the carbonates get driven off, and the surface Ca 2+ and PO 4 is decreased and in microsieve theory, the surface calcium and phosphate migrate to the deeper layers leaving areas that can subsequently act as reservoir for future fluoride uptake and remineralization which explains the recrystallization in conjunction with laser activated fluoride therapy (LAFT). Laser increases the uptake and percentage of firmly bound fluoride and promotes recrystallization and lowers the critical pH from 5.5 to less than 1.31. A physical seal achieved by melting the surface through partial recrystallization of enamel prisms, alteration in enamel composition through decrease in carbonate (66%), water, apatite hydroxide (33%), and inorganic content resulting in reduction in lattice strain and decreased solubility. The SEM picture explains how laser works via organic blocking theory and alteration of chemical composition. It shows clearly how the surface carbonates and organic part of enamel (which rest in the interprismatic parts of the enamel) is stripped revealing the enamel rods which is exposed vividly [Figure 5] and [Figure 6].
Figure 5: Scanning electron microscopy picture of enamel before application of laser

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Figure 6: Scanning electron microscopy picture of enamel after application of laser

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The various advantages [6],[7] of laser bleaching are:

  • Increases the resistance of tooth structure to mineral loss from the organic acids involved in dental caries
  • Microcrystalline nature and surface topography of the enamel transformed biomechanically sound without being porous
  • Toxic effect of HP and its derivatives minimized
  • Fluoride content can be added to provide (LAFT) further protection and strength.

Sognnaes and Stern (1972) [8] first demonstrated the effect of laser irradiation on enamel resistance to demineralization (pulsed CO 2 laser energy densities of 10-50 J/cm 2 which increased dissolution resistance. Fox and Otsuka (1992), [9] showed laser irradiation alone reduced the critical pH at which enamel dissolution occurs from 5.5 to 4.78, enamel solubility at pH 4.5 reduced fivefold compared to untreated enamel thereby showed that LAFT could lower the critical pH further to 4.31.

The goal of power bleaching is to whiten the tooth efficiently by obtaining controlled temperature elevation, [10] but with no morphological and chemical changes of enamel. [11] External bleaching therapy with activation by light or laser may be accompanied by a temperature increase at the tooth surface, as well as in the pulpal chamber. However, the bleaching gel usually applied may act as an isolator, reducing intrapulpal temperature increase in comparison with that with laser irradiation only. [12] This means that laser activation (830 nm diode laser, 30 s, and 3 W) without the use of bleaching gel results in an intrapulpal temperature increase of approximately 16°C, whereas only an 8.7°C temperature increase was recorded when a gel was applied during activation. [13] The increase in the pulp chamber temperature with a diode laser used at 1-2 W is below the critical temperature increase of 5.5°C which is nowadays regarded as the threshold value, and should not be exceeded, to prevent irreversible pulp damage. [14] A temperature increase of 2-8 and 4-12°C was observed when a 960 nm diode laser was used to activate Opalescence Extra and Opus White for 60 s (0.9 W) and 30 s (2 W). [15] For a hydrogen peroxide bleaching agent, the mean maximum pulpal temperature rise was 2.95°C for a LED, 3.76°C for a 2ù neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, and 7.72°C for a diode laser. [15] With an output power of 1 W of a 810 nm diode laser, pulpal temperature increase was shown to be approximately 3°C with the Opus White gel, whereas a TiO2 emulsion showed almost no temperature changes in the pulp. [16] The heat element is favorable for accelerating the rate of reaction but unfavorable for maintaining pulp health.

  References Top

1.Tredwin CJ, Naik S, Lewis NJ. Scully C. Hydrogen peroxide tooth whitening (bleaching) products: Review of adverse effects and safety issues. Br Dent J 2006;200:371-6.  Back to cited text no. 1
2.Tezel H, Ertas OS, Özata F, Dalgar H, Korkut ZO. Effect of bleaching agents on calcium loss from the enamel surface. Quintessence Int 2007;38:339-47.  Back to cited text no. 2
3.Potocnik I, Kosec L, Gaspersic D. Effect of 10% carbamide peroxide bleaching gel on enamel microhardness, microstructure, and mineral content. J Endod 2000;26:203-6.  Back to cited text no. 3
4.Hegedius C, Bistey T. AFM study on effect of bleaching agents. J Dent 1999:509-15.  Back to cited text no. 4
5.Hsul CY, Jordan TH, Dederich DN, Wefel JS. Effects of low-energy co2 laser irradiation and the organic matrix on inhibition of enamel demineralization. J Dent Res 2000;79:1725-30.  Back to cited text no. 5
6.Tousignant GC, Boksman L. Dent Today 2007;26:120-3.  Back to cited text no. 6
7.Moritz A. Oral Laser Application. Berlin: Quintessence Verlags Publication; ed. 2006. p. 200-4.  Back to cited text no. 7
8.Vlacic J, Meyers IA, Kim J, Walsh LJ. Laser-activated fluoride treatment of enamel against an artificial caries challenge: Comparison of five wavelengths. Aust Dent J 2007;52:101-5.  Back to cited text no. 8
9.Fox JL, Yu D, Otsuka M, Higuchi WI, Wong J, Powell GL. Initial dissolution rate studies on dental enamel after CO2 laser irradiation. J Dent Res 1992;71:1389-98.  Back to cited text no. 9
10.Chang JC, Wilder-Smith P. Laser-induced thermal events in empty and pulp-filled dental pulp chambers. Lasers Surg Med 1998;22:46-50.  Back to cited text no. 10
11.Rohanizadeh R, LeGeros RZ, Fan D, Jean A, Daculsi G. Ultrastructural properties of laser-irradiated and heat-irradiated dentin. J Dent Res 1999;78:1829-35.  Back to cited text no. 11
12.Buchalla W, Attin T. External bleaching therapy with activation by heat, light or laser: A systematic review. Dent Mater 2007;23:586-96.  Back to cited text no. 12
13.Sulieman M, Addy M, Rees JS. Surface and intra-pulpal temperature rises during tooth bleaching: An in vitro study. Br Dent J 2005;199:37-40.  Back to cited text no. 13
14.Wetter NU, Walverde D, Kato IT, Eduardo Cde P. Bleaching efficacy of whitening agents activated by xenon lamp and 960-nm diode radiation. Photomed Laser Surg 2004;22:489-93.  Back to cited text no. 14
15.Zhang C, Wang X, Kinoshita J, Zhao B, Toko T, Kimura Y, et al. Effects of KTP laser irradiation, diode laser and LED on tooth bleaching: A comparative study. Photomed Laser Surg 2007;25:91-5.  Back to cited text no. 15
16.Verheyen P, Walsh LJ, Wernisch J, Schoop U, Moritz A. Laser-assisted bleaching. In: Moritz A, Beer F, Goharkhay K, Schoop U, Verheyen P, Walsh LJ, et al. editors. Ch. 10. Oral Laser Application. Berlin: Quintessence; 2006. p. 426.  Back to cited text no. 16


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2]

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