Effective of diode laser on teeth enamel in the teeth whitening treatment

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1 Effective of diode laser on teeth enamel in the teeth whitening treatment U. Klunboot *a,b, K. Arayathanitkul a,b, R. Chitaree a,b, N. Emarat a,b a Dept.of Physics, Mahidol University, 272 Rama 6 Rd., Bangkok, Thailand 10400; b Thailand Center of Excellence in Physics, Research Center in Integrated Physics (Physics Education), P.O.Box 70, Chiang Mai University, Chiang Mai, Thailand ABSTRACT This research purpose is to investigate the changing of teeth color and to study the surface of teeth after treatment by laser diode at different power densities for tooth whitening treatment. In the experiment, human-extracted teeth samples were divided into 7 groups of 6 teeth each. After that laser diode was irradiated to teeth, which were coated by 38% concentration of hydrogen peroxide, during for 20, 30 and 60 seconds at power densities of 10.9 and 52.1 W/cm 2. The results of teeth color change were described by the CIEL*a*b* systems and the damage of teeth surface were investigated by scanning electron microscopy (SEM). The results showed that the power density of the laser diode could affect the whiteness of teeth. The high power density caused more luminous teeth than the low power density did, but on the other hand the high power density also caused damage to the teeth surface. Therefore, the laser diode at the low power densities has high efficiency for tooth whitening treatment and it has a potential for other clinical applications. Keywords: Teeth whitening, CIEL*a*b*, SEM 1. INTRODUCTION Many dental works have been developed to improve the appearance of a person s teeth. Tooth whitening treatment is one of them. Alkhatib [1] presented that a number people were concerned with their teeth color. This reason motivated more researches on developing brighter teeth treatments. This is evident that, in the past 5 years, the research in this field has increased over 300% [2]. The teeth whitening started since 1799 by Macintosh [3]. In 1937, J.W. Ames applied Hydrogen Peroxide (H 2 O 2 ) to tooth bleaching [4]. Carbamide Peroxide (CH 4 N 2 O H 2 O 2 ) was also used as a bleaching agent by Haywood and Heymann who invented the treatment call Nightguard Vital Bleaching in 1989 [5]. Patients who use this treatment have to spend a few hours per day for at least 2 weeks to complete the treatment period. This should be noted that the treatment has a potential to create tooth sensitivity and gingival irritation. However, this technique is popular because of the lower cost than others techniques and the simplicity of process. More recently, a laser treatment was introduced to help tooth bleaching. The laser activated bleaching provides several advantages over the treatment by the bleaching alone. These include the reduction of the tooth sensitivity and gingival irritation due to a shorter exposure time treatment, but this treatment is more costly. Some laser sources used in bleaching treatment include argon laser, CO 2 laser and diode laser [6][7]. Many reviews have compared performances of light sources and the experimental results pointed out that the laser diode was suitable for treatment especially in the part of soft tissue [8][9][10][11]. Moreover, that research also investigated effects from the laser treatment in terms of the optical light application and period of radiation [12][13]. phone , ; fax Optical Sensors and Biophotonics III, edited by Jürgen Popp, Dennis L. Matthews, Jie Tian, Chih-Chung Yang, Proc. of SPIE-OSA-IEEE Asia Communications and Photonics, Vol. 8311, 83111H 2011 SPIE-OSA-IEEE CCC code: X/11/$18 doi: / Proc. of SPIE Vol H-1

2 Currently 3 methods; shade guide, photography and spectrophotometry [14] are commonly used to examine the teeth color change [15][16]. Other aspects to be considered in the treatment include temperature increase while treating and tooth surface damage after treating [17][18]. The temperature increase (>5.6 C) in pulpal tissues of teeth is very critical [19], because the pulpal tissues turn to a necrosis [20]. This prompted the researchers to find a suitable power for treatment. Equally important, the morphology of teeth surface after treatment must not change after treatment. Researcher studied the damage of whitening gel to the surface of teeth by Scanning Electron Microscopy (SEM) [21][22][23], they found that the concentration of whitening gel and duration time could destroy the surface of teeth. In all, types of lasers, power of lasers and radiation time become important factors to be studied because they can cause damage to the surface of teeth [24][25][26]. From literature reviews, this is also evident that the research on laser teeth whitening still lacks the study of color change in quantitative way. Therefore, in this study we will investigate and evaluate the color change and the morphology of teeth surface before and after the laser diode treatment so as to find appropriate optical power application and suitable radiation time for the most effective treatment. 2.1 Bleaching agent 2. METHODOLOGY The bleaching agent, Opalescence Boost, contain 38 % hydrogen peroxide and composed of PF (potassium nitrate and fluoride), which has been proven to reduce caries susceptibility and lower sensitivity. This agent is also indicated for using without activation by a light source. 2.2 Light source The diode laser (GaAlAs diode, LDM-808 Series, Roithner Laser Technik GmbH, Vienna, Austria) emitting the wavelength of 808 nm was used for irradiation. 2.3 Preparation of teeth The 42 extracted human teeth (approved by the ethics committee of Mahidol University Institutional Review Board; project no. 2010/ ) were used for the in vitro experiment. The extracted teeth were stored in the sodium chloride solution for 48 h for disinfection, and then kept in 0.9% saline solution prior to the experiment. This solution has no influence on the mechanical properties of teeth during storage. Before the experiment, all teeth had been immersed into a staining solution which was made of coffee for seven days at a constant temperature of 37 C. This solution was stirred every day to prevent the development of the sediment at the bottom of a container. After the staining period, the teeth were cleaned with distilled water and completely dried. The cleaned teeth samples were then molded to acrylic bases for convenient handling and they were signified with the numbering. 2.4 Experimental design All extracted teeth were randomly divided into 7 groups; Groups G1, G2 and G3 were irradiated with laser diode at the power density of 10.9 W/cm 2 and groups G4, G5 and G6 were shined with laser diode at power density of 52.1 W/cm 2 as shown in Table 1. An approximately 2 mm thick layer of the bleaching agent was applied on the surfaces of teeth covering completely the area and kept for 15 minutes on the control group, G7. Groups G1 and G4 were applied by the bleaching agent and immediately irradiated with the diode laser for 20 second period. The bleaching agent had been coated on the teeth surface for 7 minutes and then irradiated again for 20 seconds. These procedures were then repeated. After third irradiation, the agent was immediately came off, the teeth samples were cleaned with water and dried. Groups G2 and G5 were irradiated with the diode laser on the teeth surface which applied the bleaching agent during 30 seconds for 2 cycles and the bleaching agent had remained to the teeth for 7 minutes. Groups G3 and G6 were applied by the bleaching agent and immediately irradiated with diode laser during 60 seconds and then the teeth samples were rinsed with water and dried. Proc. of SPIE Vol H-2

3 Table 1. Irradiation parameters Group Power (W) Power density (W/cm 2 ) Radiation time (sec) G triple G twice G once G triple G twice G once G7 (Control group) Color analysis After the treatment, the teeth samples were cleaned with distilled water and dried. For the color analysis we evaluated the teeth color twice before and after treatments with spectrophotometer (Model USB4000, Ocean Optics) in terms of the CIE L*a*b* color space. And then the differences between the L*a*b* values were appraised. The three coordinates of CIEL*a*b* represent the color space; L*is the luminosity dimension or whiteness (L* = 0 yields black and L* = 100 indicates diffuse white), a* is position between red and green (negative values indicate green and positive values indicate red), and b* is position between yellow and blue (negative values indicate blue and positive values indicate yellow).the chroma (C*) or color saturation was obtained through the following formulae, 2.6 The surface morphology (C*) 2 = (a*) 2 +(b*) 2 (1) After the color analysis, the surface morphology in the enamel of teeth from all treatment was investigated by scanning electron microscope (Hitachi TM100, Japan). All teeth were placed on stubs for 2weeks for completely dehydration. After that the surface of teeth was coated with a thin layer of gold, using a sputtering apparatus. 2.7 Statistical analysis The L*a*b* values between before treatment and after treatment in the same group were analyzed using paired sample t- test. The total color differences between groups were tested by one-way ANOVA followed by Tukey s post hoc tests. 3.1 Color analysis 3. RESULTS The teeth color changes measured by spectrophotometer before and after treatment were shown in Table 2, which presented in terms of the L*, a* and b* values at all treatment. The L* values of teeth in the group control (G1) before treatments were not significantly different from that after the treatments. All treatment groups (G1 to G6) showed significant difference between before and after treatments at p-value < 0.05 of the L* values. All teeth showed a prominent yellow hue and negligible contribution from red color. The a* values are between 0.0 and 2.8 and the b* value are between 12.6 and When we analysed statistic, we found that the a* and b* values have the same statistical as L* values.all treated groups (G1 to G6) showed significant difference between before and after treatments at p-value < Proc. of SPIE Vol H-3

4 Table 2. The L*a*b* values of all treatments Group L* before after before a* after b* before after G G G G G G G The mean values of the chroma change, C*, along with the mean values of the lightness change, L*were shown in Fig1. All groups showed a positive value of L* which implies that all teeth had an increasee in lightness. All treatment groups (G1 to G6) were significant difference from that of the control group at p-value < 0.05 except for group G3, which was no significant difference from the control group. The highest lightness change occurs in G5, G4 and G6 groups, whichh were irradiated with 52.1 W/cm 2 of laser diode with the double-exposure of 30 seconds, the triple-exposuree 20 seconds and single-exposure of 60 seconds respectively. For the chroma change, C*, The treatment groups were significantly different from the of the control group at p-value < 0.05 except for groups G5 and G6 groups, which weree no significantly different from the control group. 25 Lightness Change, L* G2 G3 G5 G7 G6 G4 G Chroma Change, C* 6 7 Fig. 1. Change in croma (ΔC*) and whiteness (Δ L*) of treated group and control group. 3.2 The surface morphology The surfaces of the teeth were examined by SEM. The results of SEM images showed that groups G1, G2 and G3 (power density 10.9 W/cm 2 ) cause no tooth surface loss. However, in groups G4, G5 and G6 (power density 52.1 W/cm 2 ) the damage the surface of teeth was evident. The most damage was observed from 60 second radiation time. Fig 2 shows the comparison between the surface of teeth from groups irradiated with the laser diode at the power density of 10.9 W/cm 2 and 52.1 W/cm 2. Proc. of SPIE Vol H-4

5 G1 G4 G2 G5 G3 G6 G7 Fig. 2. Scanning electron microscopy of teeth surface following whitening treatment with different procedures, (G1-G7), bar = 20 µm and original magnification 5000x. Proc. of SPIE Vol H-5

6 4. DISCUSSIONS Research in the tooth whitening treatment can be done in various aspects. Briso and coworker [27] compared the experimental results between the treatments with and without light source. They found that with the light source the treated teeth became whiter. To examine the teeth color quantitatively, the CIE L*a*b* color system was used to describe the teeth human color by Andrew [28]. Niklaus [10] studied about the teeth color change in terms of the lightness change, L*, and the chroma change, C* by using two light sources and two kinds of the whitening gel. Regarding to the L*a*b* values obtained in this study, the color analyses showed that the lightness increased in all treated groups. The L* values are positive. This means that after the treatment all treated groups had whiter teeth than before the treatment. In addition, the color analyses showed that the color shifted to light yellow (positive b*). An average increase of color saturation showed the teeth color changed from gloomy to brighter teeth (positive C*). Therefore, the laser diode could effectively be used in the tooth whitening treatment. This is, in fact, with confirms versatility of the laser diode in dentistry [8] and Niklaus s research [17]. Fig 1 shows the lightness increases for all treated groups. When we compared results from each group in terms of power density, G4, G5 and G6 which were irradiated at the power densities of 52.1 W/cm 2 of 808 nm laser diode over a duration of radiation of the triple-exposure of 20 seconds, the double-exposure of 30 seconds and single-exposure of 60 seconds respectively had higher lightness increase than other groups had. This is because the high power density stimulated the hydrogen peroxide molecules more effectively [7].In addition, when we compared the groups, which were irradiated at the same power density, we found that the teeth in groups being stimulated with the double-exposure of 30 seconds and the triple-exposure of 20 seconds had a higher L* values than being stimulated with the single-exposure of 60 seconds. This is clear that, these two groups were significantly different at p-value < 0.05, when being compared to the groups of single-exposure of 60 seconds. However, the groups of double-exposure of 30 seconds and triple-exposure of 20 seconds were found to be insignificantly different between two groups at p-value < The condition of the teeth surfaces after treatment is another concern for patients. An examination of the teeth surface is required so as to check an appropriate laser power density safely applied to the teeth without causing any damage. Therefore, SEM images of teeth surface was used to specify the power density of laser diode irradiation. Consequently, this result in teeth whitening treatment can be safely applied to the dentistry. Few researches have been published on the analysis of the achievement of morphology of teeth surface. M. Maurem [24] showed that the teeth surface were destroyed when they used Nd:YAG laser at high energy for the laser tooth whitening treatment. K. Goharkhay [25] found that the second harmonic of Nd:YAG laser could be used in the treatment and the low power of this laser did not create the wrinkle of teeth surface. D. Arantzs [26] used many light sources to stimulate the hydrogen peroxide and studied the teeth surface changed by SEM, they found that all light sources made no difference to the furrow of teeth surface. In this study, the surface of teeth were destroyed in the group treated by the laser diode with the power density of 52.1 W/cm 2 (Fig 2), but the group of power density of laser diode 10.9 W/cm 2 did not create the wrinkle on the teeth surface. The power density of laser diode can influence the furrow of teeth surface and the teeth color change. Therefore, the power density of the laser for tooth whitening treatment must appropriately be applied. From our study, an appropriate power of the laser was found to be 10.9 W/cm 2 and radiation times were 20 and 30 seconds. The conclusions were confirmed by having high brightness teeth and still healthy teeth surfaces. 5. CONCLUSIONS The oxidation of the hydrogen peroxide can quickly be activated when an optical power is applied to the hydrogen peroxide. So this technique can prevent tooth sensitivity and gingival irritation. In this research we showed that the high power density from laser caused more white teeth than the low power density did, but the high power density of the laser also destroy on the surface of teeth. Therefore, an operator must carefully choose a suitable power density and radiation time, which is safe for the surface of teeth, in an operation. In this research the groups of irradiated double-exposure of 30 seconds of the laser diode at power density of 10.9 W/cm 2 is the better density that creates safety the surface and still effective for the whitening treatment operation. Proc. of SPIE Vol H-6

7 ACKNOWLEDGEMENTS The authors would like to thank Applied Optics Research group and Physics Education Network of Thailand group (PENThai) for their supports on materials and equipment. REFERENCES 1. J. Andrew, J.P. Carole, A. Coralie, T.A. Alex and J.S. Naomi, A novel optical approach to achieving tooth whitening, Journal of Dentistry 36s, s8-s14 (2008). 2. S.C. Daniela, S.Jr. Landulfo, A.N. Ranata, Z. Fatima and B.Jr. Aldo, Comparison of temperature increase in in vitro human tooth pulp by different light sources in the dental whitening process, Lasers Med Sci24, (2009). 3. K. So-Ran and H.G. Linda, Tooth Whitening in Esthetic Dentistry: principles and techniques, Singapore, G. Chudasama, A. Cohen, S. Dalmao, A. Dev, K. Dobson, J. Duinker, D. Dumitru and N. Fallahi, An Evidence Based Study On the Benefits and Risks of Home Bleaching Products, In University of Toronto Faculty of Dentistry, Canada, p V.B. Haywood and H.O. Heymann, Nightguard vital bleaching, Quintessence Int20, (1989). 6. F. de A. Marcelo, C. Huck and S.M.C. Maria, A Vital Tooth Bleaching Technique with a Compound Light System LED, The Journal of Oral Laser Applications 3(3), (2003). 7. B. Wolfgang and A. Thomas, External bleaching therapy with activation by heat, light or laser A systematic review, Dental Materials23, (2007). 8. S. Pirnat, Versatility of an 810nm Diode Laser in Dentistry: An Overview, Journal of Laser and Health Academy, 4, 1-9 (2009). 9. L.J. Walsh, The current status of laser applications in dentistry, Australian Dental Journal 48(3), (2003). 10. U.W. Niklaus, C.S.B. Marcia and E.P. Jose Pelino, Dental Bleaching Efficacy With Diode Laser and LED Irradiation: An In Vitro Study, Lasers in Surgery and Medicine35, (2004). 11. W. Kabbach, D.M. Zezell, M.C. Bandeca, T.M. Pereira and M.F. Andrade, An in vitro thermal analysis during different light- activated hydrogen peroxide bleaching, Laser Physics 20(9), (2010). 12. G. Marcato, V. Lazzarini, G.F. Semez, C. Fornaini and J.P. Rocca, Laser Assisted Non Vital Tooth Whitening in one step: Comparison of Two Wavelengths, ISLD 10 th congress, P. Bonetti, A. Baldissarri, R. Brancati, R. De Gregoriis, M.F. Bertrand and J.P. Rocca, Tetracyclines and Tooth Discoloration: Nd:YAG and Diode Lasers Management, ISLD 10 th congress, G. Mclaughlin and G.A. Freedman, Color atlas of tooth whitening, Ishiyaku Euro America Publishing, Missouri, (1991). 15. P. Kafas, M. Theodoridis, D. Dionysopoulos, I. Andreou and N. Dabarakis, Diode Laser Tooth Whitening Improved Enamel Luminosity: A Case of Digital Photometry, Research Journal of Medical Sciences 2(4), (2008). 16. D.B. Willeam, Use of Shoad Guides for Color Measurement in Tooth-Bleaching Studies, Journal of Esthetic and Restorative Dentistry 15(1), s13-s20 (2003). 17. U.W. Niklaus, W. Deboraayala, K. Lkatiemy and E. C. de Paula, Bleaching Efficacy of Whitening Agents Activated by Xenon Lamp and 960-nm Diode Radiation, Photomedicine and Laser Surgery 22(6), (2004). 18. A. Ruha Yazici, K. Azita and K. Gerard, Effects of an In-office Bleaching System (ZOOM ) on Pulp Chamber Temperature In Vitro, The Journal of Contemporary Dental Practice 8(4), 1-5 (2007). 19. R.G.T. Carlos, M.F.C. Taciana, C.D.A. Felipe and B.B. Alessandra, In vitro assessment of pulp chamber temperature of different teeth submitted to dental bleaching associated with LED/laser and halogen lamp appliance, General Dentistry 56(5), (2008). 20. R.G.M. Vinicius, Y.T. Edgar, U.W. Niklaus, D.N. Ruchele and E.C. de Paula, Intra pulpal Temperature during Preparation with the Er:YAG Laser: An in Vitro Study, Photomedicine and Laser Surgery 23(2), (2005). 21. J. Tao, M. Xiao, W. Zhejun, T. Hua, H. Jiming and W. Yining, Beneficial effects of hydroxyapatite on enamel subjected to 30% hydrogen peroxide, Journal of dentistry 36, (2008). 22. R. Yan-Fang, A. Azadeh and M. Hans, Effects of tooth whitening and orange juice on surface properties of dental enamel, Journal of dentistry 37(6), (2009). 23. K. Kohji and T. Ysujimoto, Effects of the Hydroxyl Radical and Hydrogen Peroxide on Tooth Bleaching, Journal of Endodontics 30(1), (2004). Proc. of SPIE Vol H-7

8 24. M. Maurem, P.G.P. Maria, M.S. Ana, G.M. Eduardo, L.de Silva, A.S. Andre and H.B. Luiz, The Influence of the Nd:YAG Laser Bleaching on Physical and Mechanical Properties of the Dental Enamel, Journal of Biomedical Materials Research Part B:Applied Biomaterials 90B, (2009). 25. K. Goharkhay, U. Schoop, J. Wernisch, S. Hartl, R. De Moor and A. Moritz, Frequency doubled neodymium: yttrium-garnet and diode laser-activated power bleaching-ph, environmental scanning electron microscopy, and colorimetric in vitro evaluations, Laser Med. Sci 24, (2009). 26. D. Arantza, A.G. Juan, C. Angel and G. Clara, Influence of the Light Source and Bleaching Gel on the Efficacy of the Tooth Whitening Process, Photomedicine and Laser surgery 28(1), (2011). 27. A.L.F. Briso, M.S.M. Fonseca, L.C.A.G. de Almeida, S.J. Mauro and P.H. dos Santos, Color Alteration in Teeth Subjected to Different Bleaching Techniques, Laser Physics 20(12), (2010). 28. J. Andrew, Tooth colour: a review of the literature, Journal of Dentistry 32, 3-12 (2004). Proc. of SPIE Vol H-8