Penetration of 35% Hydrogen Peroxide into the Pulp Chamber in Bovine Teeth after LED or Nd:YAG Laser Activation

Transcription

1 Publication Penetration of 35% Hydrogen Peroxide into the Pulp Chamber in Bovine Teeth after LED or Nd:YAG Laser Activation Samira Esteves Afonso Camargo, DDS, MsC Postgraduate student, School of Dentistry, Department of Oral Pathology Paula Elaine Cardoso, DDS, MsC Postgraduate student, School of Dentistry, Department of Endodontics Marcia Carneiro Valera, DDS, MsC, PhD School of Dentistry, Department of Endodontics Maria Amélia Máximo de Araújo, DDS, MsC, PhD School of Dentistry, Department of Restorative Dentistry Alberto Noriyuki Kojima, DDS, MsC Postgraduate student, School of Dentistry, Department of Dental Materials Correspondence to: Samira Esteves Afonso Camargo Winkelfeldweg, 15, Oberisling, Regensburg 93053, Germany; 82

2 CAMARGO ET AL Publication Abstract This aim of the present study was to evaluate the pulp chamber penetration of 35% hydrogen peroxide activated LED (lightemitting diode) or Nd:YAG laser in bovine teeth, after an in-office bleaching technique. Forty-eight bovine lateral incisors were divided into four groups, acetate buffer was placed into the pulp chamber and bleaching agent was applied as follows: group A (n = 12), activation was permed LED; group B (n = 12), activation was permed Nd:YAG laser (60 mj, 20 Hz); group C (n = 12) received no light or laser activation; and the control group (n = 12) received no bleaching gel application or light or laser activation. The acetate buffer solution was transferred to a glass tube and Leuco Crystal Violet and horseradish peroxidase were added, producing a blue solution. The optical density of this solution was determined spectrophotometrically and converted into microgram equivalents of hydrogen peroxide. The results were analysed using ANOVA and Tukey s test (5%). It was verified that the effect of activation was significant, as groups activated LED or laser presented greater hydrogen peroxide penetration into the pulp chamber (0.499 ± μg) compared with groups that were not (0.198 ± μg). There was no statistically significant difference in the penetration of hydrogen peroxide into the pulp chamber between the two types of activation (LED or laser). The results suggest that activation laser or LED caused an increase in hydrogen peroxide penetration into the pulp chamber. (Eur J Esthet Dent 2009;4:82 89.) 83

3 Publication Tooth bleaching is now a commonly used treatment because of its easy application. It offers tooth color harmony, an essential component of esthetics. Also, tooth bleaching is relatively non-invasive and allows preservation of dental tissue. 1 Bleaching techniques vital teeth can be permed patients under the clinician s supervision with 10 to 22% carbamide peroxide or 3 to 9.5% hydrogen peroxide, or in-office with 35 to 37% carbamide peroxide or 30 to 38% hydrogen peroxide. 1,2 It is known that the mechanism of action of bleaching agents involves oxidation of organic components in which the structure to be bleached donates electrons to the bleaching agent, opening in the pigmented carbon rings and converting them to chains that are lighter in color 3. This reaction is possible because of the low molecular weight of peroxide solutions, allowing their diffusion through enamel and dentin. 4,5 The penetration of the bleaching agent through dental tissues can be facilitated alterations that it promotes in the chemical composition of teeth, decreasing the proportion of calcium and phosphate in enamel and dentin. 6,7 However, in vivo this mineral damage is reversible, because of the remineralization potential of dental tissues after bleaching treatment. 8 One of the greatest concerns about tooth bleaching relates to peroxide penetration through enamel and dentin, reaching the pulp. However, the effects of peroxide penetration are still controversial. While some authors consider this bleaching agent safe, 8 others believe that hydrogen peroxide can cause irritation in pulp tissue 9 or an alteration in the dental structure. 2,10 The photoactivation mechanisms of bleaching agents could induce peroxide penetration into the pulp chamber. The bleaching agent is activated with a light source to accelerate its decomposition, releasing free radicals such as O - or oxidizing the pigments of discoloration. 11 However, it is possible that this light curing induces oxidative radical penetration into the pulp chamber. The purpose of this study was to evaluate the penetration of 35% hydrogen peroxide activated light-emitting diode (LED) or Nd:YAG laser into the pulp chamber of bovine teeth, after an in-office bleaching technique. Materials and methods This project was developed in accordance with the Code of Ethics in Research. Forty-eight bovine lateral incisors were extracted and stored in physiologic saline solution at -18 C until used. All teeth were examined under a stereomicroscope (Zeiss Stemi C 2000) to select those without surface defects. The roots were cut with disks up to 3 mm from the cementoenamel junction. The pulp tissue was removed using Hedström files (Mailleffer, MI, USA) and the pulp chamber was irrigated with saline. The pulp cavities were widened using a round bur (n. 1016, KG Sorensen, Barueri, SP, Brazil) to allow the introduction of a micropipette into the pulp chamber. Teeth with similar sizes were selected to achieve standard pulp chamber size, to allow application of 100 μl of acetate buffer in the bovine teeth. Teeth were divided into four groups, according to the procedure of the bleaching gel (35% hydrogen peroxide; Whiteness HP, FGM, Joinville, SC, Brazil) activation. In 84

4 CAMARGO ET AL Publication Results (in μg) bovine teeth the four experimental conditions were: group A (LED), ± μg; group B (Nd:YAG laser), ± μg; group C (no activation), ± μg; and the control group presented no hydrogen peroxide penetration (0 μg) (Fig 1). Groups treated with bleaching agent showed greater hydrogen peroxide penetration compared with the control group. However, only groups A (LED) and B (Nd:YAG laser) presented a significant difference (P < 0.005). Comparison of the experimental groups, except the control group, demonstrated that there was a stagroup A (12 teeth), the activation was permed LED (Biolux laser, Bio-Art); in group B (12 teeth), the activation was permed Nd:YAG laser (PulseMaster 600 IQ apparatus, Dental American Technologies, Corpus Christi, TX, USA) and the parameters used were 60mJ and 20Hz. In group C (12 teeth), the bleaching gel was applied without curing light; and in the control group the teeth were immersed in distilled water. Teeth were isolated using two layers of nail polish, leaving a standardized buccal area exposed application of the bleaching agent. The pulp chambers were dried and 100 μl of 2 mol/l acetate buffer was placed into the pulp chamber of each tooth. The acetate buffer was necessary to stabilize the hydrogen peroxide that might penetrate into the pulp chamber on later quantification. All teeth were vertically fixed on a wax plate to allow application of the treatment agent. In groups A and B, 2 minutes after bleaching gel application, the treatment was activated LED or Nd:YAG laser (60 mj/20 Hz), respectively, 1 minute. The light and laser irradiation were applied perpendicular to the tooth s vestibular surface, without contact with the bleaching agent. These procedures were repeated three times, at intervals of 5 min, totaling 20 min of application each. In group C, the bleaching agent was applied on the vestibular surface 20 min, after which it was removed and the surface was washed with a water jet. In the control group, there was no application of bleaching agent and the vestibular surfaces were immersed in distilled water 20 min. The acetate buffer solution was removed using a microsyringe (Terumo Microsyringe MS-100, Terumo, Tokyo, Japan) and transferred to a glass tube. The pulp chamber of each tooth was rinsed twice with distilled water placed in the same glass tube. Leucocrystal Violet (100 μl of 0.5 mg/ml; Sigma-Aldrich, St Louis, MO, USA) and 50 μl of 1 mg/ml horseradish peroxidase (Sigma-Aldrich) were also added to each tube and the solution was diluted to 3 ml with distilled water. The optical density of the resulting blue color in the tubes was measured with a spectrophotometer (UV Spectrophotometer UV-1203, Shimadzu, Kyoto, Japan) at a wavelength of 596 nm. A standard curve of known amounts of hydrogen peroxide was used to convert the optical density values obtained from the samples into microgram (μg) equivalents of hydrogen peroxide. Optical density readings were normalized to the control group (= 0), and differences between median values were statistically analyzed using the two-way analysis of variance (ANOVA) and Tukey s test (5% level of significance). Results 85

5 Publication Fig 1 Hydrogen peroxide penetration values according to experimental conditions: LED (Group A), laser (Group B), no activation (Group C), and control group. tistically significant difference between groups A and B in relation to group C (no activation) (P < 0.005). Groups A and B were not statistically different from each other (P = ) (Table 1). Discussion The penetration of bleaching agents occurs mainly due to their low molecular weight and ability to denature proteins, which increases the ion movement through the enamel and dentin. 12,13 Theree, the longer the period of contact between hydrogen peroxide and enamel, the greater its penetration, in both quantity and depth. 14 Haywood 4 reported that 35% hydrogen peroxide reaches the pulp more quickly, and that in 15 minutes of exposure, there was 12 times more peroxide penetration than when 10% carbamide peroxide was used. In the present study it was verified that 35% hydrogen peroxide penetrated into the pulp chamber after 20 minutes of exposure to the bleaching agent. Peroxide penetration into the pulp can be facilitated alterations that the bleaching agent promotes in dental tissues. The hydrogen peroxide is able to induce chemical alterations in the composition of teeth, reducing the quantity of calcium and phosphate in enamel and dentin. 15 However, this mineral loss is not of clinical significance because of the remineralization potential of dental tissues after tooth bleaching. 16 Turssi et al 17 reported that in the group treated with 35% hydrogen peroxide only, there was no significant increase in enamel permeability when the bleaching agent was activated the LED/laser or Quartzt tungsten Halogen (QTH) light devices, and all bleached groups showed greater permeability than the unbleached/non-irradiated group. Table 1 Tukey test (5%) experimental and control groups. Groups Mean (± SD) Homogeneous groups* LED ± A Laser ± A No activation ± B Control 0 B *Different letters correspond to statistically different data. 86

6 CAMARGO ET AL Publication The pulp tissue can protect itself from damage hydrogen peroxide (under conditions of oxidative stress from bleaching agent application) through the enzymatic breakdown of the molecule peroxidase and catalase. 10 These cellular enzymatic systems eliminate the excess oxygen. However, it is not known how much hydrogen peroxide can be tolerated the pulp tissue. 9,18 Bleaching agents can be activated light sources, such as argon, CO 2 or Nd:YAG lasers, LED, halogen lamps, plasma arc lights or heated manual instruments. 11 Thus, heat and light have been used empirically in attempts to catalyze hydrogen peroxide decomposition and speed up tooth whitening. 19 In the present study, it was shown that these light sources can lead to increased bleaching agent penetration into the pulp chamber, which can induce in vivo pulp damage. However, no pulpal pressure of the dentinal fluid was simulated recorded that could reduce the diffusion rate of the hydrogen peroxide directed to the pulp. Light sources as laser or LED are not significantly absorbed colorless bleaching gel, because most of the energy is reflected or transmitted. Theree, it is essential to use a colored bleaching agent so that it can absorb the light. 20, 21 In the present study, Whiteness HP (35% hydrogen peroxide) was used because of its red coloration. Baik et al 20 and Luk et al 21 reported that the application of laser lights significantly improved the whitening efficacy of some bleaching materials, but it caused significant temperature increases in the outer and inner tooth surfaces. Baik et al 20 showed that light sources, such as argon lasers and plasma arc lights, increased the temperature of the bleaching gel and the temperature inside the pulp. Increased intrapulpal temperature can affect patient sensitivity and pulp health. However, Hein et al 19 and Ladalardo et al 22 reported that use of LED induces a maximum increase of 2 C, heating only the bleaching agents and not the dental tissues. Although in the present study the tooth temperature changes were not evaluated, it was shown that hydrogen peroxide showed a greater penetration in groups treated LED or laser Nd:YAG activation. Thus, the activation induced hydrogen peroxide penetration into the pulp chamber. In contrast, Papathanasiou et al 23 evaluated the effectiveness of light-curing (heat conversion) versus no light-curing (no heat conversion) of 35% hydrogen peroxide in an in-office tooth-whitening system. They verified that light source activation did not cause a statistically significant difference compared with no activation, indicating that light curing is optional with this 35% toothwhitening system. In the present study, the peroxide penetration only into the pulp of bovine teeth was evaluated. It is known that bovine and human teeth present morphological differences, as bovine teeth are more porous and have a different number of dentinal tubules compared with human teeth. When bovine teeth are used to simulate procedures of dentin hybridization in areas close to the pulp, there is low permeability because the diameter of dentin tubules in bovine teeth is smaller and the intertubular dentin area is larger than in human teeth. 24 It has been reported that the peroxide penetration in human teeth is greater than in bovine teeth. 2 Studies of the pulp sensitivity during vital bleaching show that although pulp re- 87

7 Publication actions are common, they can be considered reversible. 8-10,12 However, it would be interesting to perm more studies regarding the effects in vivo of bleaching agents, especially when light activation is used. Conclusions Bleaching agent activation LED or Nd:YAG laser increased the bleaching agent penetration into the pulp chamber. However, this penetration may not accurately reflect the situation in human teeth, as bovine teeth were used and the pulpal pressure of dentinal fluid was not recorded. References 1. Rosenstiel SF, Gegauff AG, McCafferty RJ, Johnston WM. In vitro tooth color change with repeated bleaching. Int 1991;22: Camargo SE, Valera MC, Camargo CH, Gasparoto Mancini MN, Menezes MM. Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique. J Endod 2007;33: Goldstein GR, Kiremidjian- Schumacher L. Bleaching: is it safe and effective? J Prosth Dent 1993;69: Haywood VB. Overview and status of mouthguard bleaching. J Esthet Dent 1991;3: Haywood VB, Heymann HO. Nightguard vital bleaching: how safe is it? Int 1991;22: McEvoy SA. Chemical agents removing intrinsic stains from vital teeth. II. Current techniques and their clinical application. Int 1989;20: Rotstein I, Lehr Z, Gedalia I. Effect of bleaching agents on inorganic components of human dentin and cementum. J Endod 1992;18: Matis BA. Degradation of gel in tray whitening. Comp Cont Educ Dent 2000;28:S28,S31-35;quiz S Li Y. Tooth bleaching using peroxide-containing agents: current status of safety issues of gel in tray whitening. Comp Cont Educ Dent 1998;19: Benetti AR, Valera MC, Mancini MN, Miranda CB, Balducci I. In vitro penetration of bleaching agents into the pulp chamber. Int Endod J 2004;37: Blankenau R, Goldstein RE, Haywood VB. The current status of vital tooth whitening techniques. Comp Cont Educ Dent 1999;20: Gokay O, Yilmaz F, Akin S, Tuncbilek M, Ertan R. Penetration of the pulp chamber bleaching agents in teeth restored with various restorative materials. J Endod 2000;26: Walsh LJ. Safety issues relating to the use of hydrogen peroxide in dentistry. Austr Dent J 2000;45: ;quiz Seale NS, Wilson CF. Pulpal response to bleaching of teeth in dogs. Pediatric Dent 1985;7: Rotstein I, Dankner E, Goldman A, Heling I, Stabholz A, Zalkind M. Histochemical analysis of dental hard tissues following bleaching. J Endod 1996;22: McCracken MS, Haywood VB. Demineralization effects of 10 percent carbamide peroxide. J Dent 1996;24: Turssi CP, Schiavoni RJ, Serra MC, Froner IC. Permeability of enamel following light-activated power bleaching. Gen Dent 2006;54: Thitinanthapan W, Satamanont P, Vongsavan N. In vitro penetration of the pulp chamber three brands of carbamide peroxide. J Esth Dent 1999;11: Hein DK, Ploeger BJ, Hartup JK, Wagstaff RS, Palmer TM, Hansen LD. In-office vital tooth bleaching: what do lights add? Comp Cont Educ Dent 2003;24: Baik JW, Rueggeberg FA, Liewehr FR. Effect of lightenhanced bleaching on in vitro surface and intrapulpal temperature rise. J Esth Rest Dent 2001;13: Luk K, Tam L, Hubert M. Effect of light energy on peroxide tooth bleaching. J Am Dent Assoc 2004;135: ;quiz Ladalardo TC, Pinheiro A, Campos RA, Brugnera Junior A, Zanin F, Albernaz PL, Weckx LL. Laser therapy in the treatment of dentine hypersensitivity. Braz Dent J 2004;15: Papathanasiou A, Kastali S, Perry RD, Kugel G. Clinical evaluation of a 35% hydrogen peroxide in-office whitening system. Comp Cont Educ Dent 2002;23: ,340, ;quiz Tonami K, Takahashi H. Effects of aging on tensile fatigue strength of bovine dentin. Dent Mat 1997;16: