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 Table of Contents  
ORIGINAL ARTICLE
Year : 2013  |  Volume : 7  |  Issue : 1  |  Page : 2-8

Effects of conventional and laser activated intracoronal bleaching agents on ultrastructure and mineral content of dentin


Department of Conservative Dentistry and Endodontics, M A Rangoonwala College of Dental Sciences and Research Centre, Pune, India

Date of Web Publication19-Sep-2013

Correspondence Address:
Robin J Jain
Department of Conservative Dentistry and Endodontics, MA Rangoonwala college of Dental sciences and Research Centre, Azam Campus, Camp, Pune
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-2868.118413

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  Abstract 

Aims and Objectives: The purpose of this in vitro study was to evaluate the ultra structural changes induced in dentin after exposure to different conventiona and laser-activated intracoronal bleaching agents . Materials and Methods: Forty human maxillary teeth were taken and were decoronated through the cemento-enamel junction (CEJ) perpendicular to the long axis of tooth, the crown part was then cut parallel to long axis dividing the tooth into mesial and distal half. Experimental specimen were then divided into two groups (n = 20) in which group 1-35% hydrogen peroxide (Pola office SDI limited Australia) Group 2-30% hydrogen peroxide (J White Heydent GmbH Germany), the groups were further sub-divided into sub-group A - conventional application and Subgroup B - laser activation (Nd: Yag laser Fotona Fidellis III). The specimens were then evaluated under scanning electron microscope (FEI quanta 200 North America) to determine diameter of dentinal tubules and chemical analysis of the same was done. Results : Within the limits of this in vitro study, higher concentration of hydrogen peroxide used as intracoronal bleaching agent: (1) increases dentinal tubule diameter. (2) And also promote alteration in organic and inorganic components of dentin with reduction in calcium/phosphorous ratio leading to demineralization with insignificant difference between conventional application and laser activation. Conclusion : Laser activation of hydrogen peroxide bleaching agent can be added to the present treatment modalities for intracoronal bleaching techniques for faster and more accurate results.

Keywords: Dentinal tubule diameter, hydrogen peroxide, intracoronal bleaching, mineral content


How to cite this article:
Jain RJ, Jadhav SK, Hegde VS. Effects of conventional and laser activated intracoronal bleaching agents on ultrastructure and mineral content of dentin. J Dent Lasers 2013;7:2-8

How to cite this URL:
Jain RJ, Jadhav SK, Hegde VS. Effects of conventional and laser activated intracoronal bleaching agents on ultrastructure and mineral content of dentin. J Dent Lasers [serial online] 2013 [cited 2022 Jul 4];7:2-8. Available from: https://www.jdentlasers.org/text.asp?2013/7/1/2/118413


  Introduction Top


In this modern era where esthetics has become so important, patients are becoming more and more demanding toward their esthetic needs, tooth discoloration has become a major problem.

Dental bleaching is commonly carried out to correct discoloration of anterior teeth. One of the common problems encountered in endodontics today is discoloration of root filled teeth. Root filled teeth may discolor because of the incorporation of breakdown products from pulpal hemorrhage incompletely removed pulpal remnants or from root canal filling materials and sealers containing eugenol or silver salts. In the anterior region, this discoloration could distract from the appearance of the teeth and be a cause of major concern to the patient and dentist alike. [1]

Bleaching procedures can be broadly divided into intracoronal or extracoronal bleaching. In extracoronal bleaching the bleaching agents are placed outside the tooth on the enamel surface, whereas in intracoronal bleaching, bleaching agents are placed in the pulp chamber, in direct contact with dentin.

Intracoronal bleaching is an established, simple, cost effective, and conservative method of improving the color of discolored teeth that have received root canal treatment given by Spasser in the year 1961. The most commonly used bleaching agents to produce the desired esthetic color changes are hydrogen peroxide and sodium perborate, either used alone or in combination. [2] More recently 10% carbamide peroxide has been recommended.

Bleaching agents act by an oxidation-reduction reaction with the darkened substrate. [1],[3],[4] When the bleaching agent is placed into the pulp chamber, reactive oxygen is released from the degradation of the bleaching agent, the colored substance is chemically reduced and transformed into a colorless material, producing the whitening effect. [4] Although these bleaching agents are highly effective in lightening tooth color, concern has been expressed regarding their use, especially hydrogen peroxide, due to the associated postbleaching complications. These include alteration in the surface morphology of dentin, [5] change in chemical composition of dentin [6] increased dentin permeability [7] external cervical root resorption. [8],[9]

According to Rotstein, et al., one of the undesirable consequences of intracoronal bleaching is external root resorption. This has been attributed to excessive hydrogen peroxide diffusing into periradicular tissue possibly through cemental defects, [10] although the exact mechanism has not been determined, the incidence of external cervical root resorption associated with intracoronal bleaching is low. [11]

From both economic and safety reasons, it would be desirable to achieve the esthetic change in the minimum number of treatment sessions as well as to minimize exposure to the periradicular tissue to hydrogen peroxide. For this the use of laser energy is a relatively novel approach, the procedure can be completed with a single session depending on the tooth. The Nd: YAG laser can achieve a positive result in cases that are completely unresponsive to conventional bleaching. [12]


  Materials and Methods Top


Preparation of the specimen

Forty human maxillary teeth [Figure 1] were used and stored in normal saline at room temperature until required. The specimen were decoronated through the cemento-enamel junction (CEJ) perpendicular to the long axis of tooth with the help of diamond disc [Figure 2], the crown part was then cut parallel to long axis dividing the tooth into a mesial and a distal half [Figure 3], in such a manner that control and test fragments were obtained from the same tooth [Figure 4].
Figure 1: Forty maxillary teeth

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Figure 2: Specimen decoronated through CEJ

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Figure 3: Crown cut parallel to long axis

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Figure 4: Prepared sample

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Bleaching procedure

Experimental specimen were then divided into two groups ( n = 20) in which group 1 - 35% hydrogen peroxide (Pola office SDI limited Australia) [Figure 5] Group 2 - 30% hydrogen peroxide (J White Heydent GmbH Germany) [Figure 6], the groups were further sub-divided into sub-group A - conventional application [Figure 7] where bleaching agent was applied for 12 minutes at 5, 10, and 15 days interval) and subgroup B - laser activation [Figure 8] in which Nd: Yag laser (Fotona Fidellis III) [Figure 9] was used at 2 W power,15 Hz frequency, 15 seconds for 3 cycles.
Figure 5: Group 1 (35%H2O2 Pola office)

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Figure 6: Group 2 (30 % H2O2 JWhite)

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Figure 7: Subgroup - A (Conventional application)

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Figure 8: Subgroup - B (Laser Activation)

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Figure 9: (Nd:YAG laser 2W,15Hz,15Seconds 3 cycles)

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During the experimental period, for conventional application old bleaching paste was cleansed by tap water, and fresh bleaching paste was replaced 5, 10, and 15 days after first placement.

For laser activated bleaching procedure Nd: Yag laser with a bleaching hand piece (R24) in noncontact mode at a distance of 1-2 cm from the tooth with parameter set as 2 W power, 15 Hz frequency for 15 seconds for 3 cycles was used in a circular motion.

Following the bleaching procedure, the specimen were ultrasonically cleansed in distilled water, air dried, mounted on acrylic block and then examined under scanning electron microscope (FEI quanta 200 North America) [Figure 10] using the backscattered electron mode to determine the diameter of dentinal tubules and surface histochemical analysis by energy dispersive spectrometer (EDS) technique was performed. The weight percentage of calcium, phosphorous, sulfur, and potassium in the dentin of each specimen were measured.
Figure 10: (scanning electron microscope)

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  Observation Top


Scanning electron microscope analysis

Histochemical analysis by EDS technique


Group 1 (35%Hydrogen peroxide Pola Office)

Subgroup-A (Conventional application)

Subgroup- B (Laser Activation)

Group 2 (30%Hydrogen peroxide JWhite)

Subgroup-A (Conventional application)


  Discussion Top


The bleaching agents that are most commonly used for whitening of root-filled teeth nowadays are hydrogen peroxide, carbamide peroxide, and sodium perborate. Hydrogen peroxide is a reactive oxygen species and acts as a strong oxidising agent through the formation of free radicals, which attack the organic molecules responsible for tooth discoloration. When complex, pigmented organic molecules (chromaphores) are broken down by the action of free radicals, simpler molecules are produced, which reflect less light. During tooth bleaching, more highly pigmented carbon ring compounds are converted to carbon chains, which are lighter in color. The carbon double bond chains (yellow in color) are converted into hydroxyl groups, which are essentially colorless. The radicals also reduce colored metallic oxides like Fe 2 O 3 (Fe 3+ ) to colorless FeO (Fe 2+ ). The bleaching process continues until all of the original pigment is rendered colorless. [12]

Although there is little doubt regarding the clinical efficacy of nonvital bleaching using 30-35% hydrogen peroxide (either thermoactivated or not), serious concerns regarding the safety of this technique, in particular the risk of producing external cervical root resorption, pulpal irritation, changes in tooth structure, microleakage of restoration, reduced bond strength of composite restoration have rendered this technique unadvisable. [12] Some researchers have also shown that bleaching agents caused alterations in the chemical structure of human hard tissues. These materials changed the original ratio between the organic and inorganic components of the tissues and increased solubility. [13] While studies on the effect of bleaching on morphological changes to dental hard tissue are contradictory, it is generally agreed that bleaching materials can alter tooth mineral contents. Potocnik and Gaspersic using electron probe analysis demonstrated lowered concentrations of calcium and phosphorous and with mean Ca/K value of all bleached samples decreasing after bleaching. [14]

External cervical resorption usually begins on the cervical region of the root surface of the teeth. [15] Although the mechanisms responsible for resorption in bleached teeth has not yet been adequately explained, it has been proven that formulations using either 30% H 2 O 2 alone or in combination with sodium perborate are more toxic for periodontal ligament cells as compared with a perborate-water suspension. [16]

Dentin is primarily formed from secretory products of the odontoblasts and their processes. Mature dentin is made up of about 70% mineral, 20% organic matrix, and 10% water on a weight basis. [17] The primary component of the organic matrix is collagen. The relatively high organic content in comparison with enamel enables dentine to deform slightly under compression. Thus, dentin imparts the resiliency necessary for the crown to withstand the forces of mastication. [17] It has been established that use of bleaching agents such as hydrogen peroxide cause a decrease in dentine hardness. [18],[19] A significant change in mechanical properties of dentin may compromise the longevity of teeth due to a decrease in its overall strength and resistance to fracture.

In contrast, studies on the efficacy of intracoronal bleaching agents in artificially discolored teeth, however, indicate that sodium perborate is inferior to 30% hydrogen peroxide used either alone or in combination with sodium perborate. The success when bleaching with 30% hydrogen peroxide varies between 80% and 93%, after two bleaching session compared with 39-53% when using sodium perborate alone. [11],[20] The other intracoronal bleaching alternative 10% carbamide peroxide has been found to be less effective than sodium perborate when evaluated at 14 days

In this study we used lasers for activation of bleaching agent, the main advantage of laser being that procedure can be completed in single appointment. The choice of the wavelength is based on the light-target tissue relationship, in this study we used the 1064 nm Nd: YAG laser, same way the bleaching agent should also absorb the light and the tooth structure should be minimally affected. Therefore photo-initiators dyes are incorporated, which are adjusted to absorb the wave length of the light source used. [1] This photo-thermal bleaching effect is used by either Diode or Nd: YAG lasers. This rapid absorption heats the bleaching agent more quickly in laser activation than does a conventional application. [21]

Some manufacturer reports that many professionals prefer to activate the bleaching gel using a light source. [22] In this study the bleaching agents used were Pola office (SDI limited Australia) and J White power bleach (Heydent GmbH Germany) and were conventionally applied and laser activated. We undertook this study to determine possible ultrastructural changes in conventional and laser-activated bleaching products, using environmental scanning electron microscopy and energy dispersive surface technique.


  Results Top


Within the limits of the present study, higher concentration of hydrogen peroxide used as intracoronal bleaching agent:

Figure 11: Closed or partially open dentinal tubules

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Figure 12: Increase in dentinal tubule diameter

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Figure 13: Closed or partially open dentinal tubules

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Figure 14: Increase in dentinal tubule diameter

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Figure 15: Closed or partially open dentinal tubules

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Figure 16: Increase in dentinal tubule diameter

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Figure 17: Closed or partially open dentinal tubules

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Figure 18: Increase in dentinal tubule diameter

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  Conclusion Top


Laser activation of hydrogen peroxide bleaching agent can be added to the present treatment modalities for intracoronal bleaching techniques for faster and more accurate results.

Histochemical Analysis by Energy dispersive surface technique

Group 1: (35% hydrogen peroxide Pola Office) Subgroup-A (Conventional application) [Table 1]
Table 1: Energy-dispersive spectrometer technique evaluation

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Group 1: (35% hydrogen peroxide pola office) Subgroup-B - (laser activation) [Table 2]
Table 2: Energy-dispersive spectrometer technique evaluation

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Group 2: (30% hydrogen peroxide J White) Subgroup-A (conventional application) [Table 3]
Table 3: Energy-dispersive spectrometer technique evaluation

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Group 2: (30% hydrogen peroxide J White) Subgroup-B - (laser activation) [Table 4]
Table 4: Energy-dispersive spectrometer technique evaluation

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  References Top

1.Plotino G, Buono L, Grande NM, Pameijer CH, Somma F. Nonvital Tooth Bleaching: A review of the Literature an Clinical Procedures. J Endod 2008;34:394-407.  Back to cited text no. 1
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2.Lim MY, Lum SO, Poh RS, Lee GP, Lim KC. An in vitro comparison of the bleaching efficacy of 35% carbamide peroxide with established intracoronal bleaching agents. Int Endod J 2004;37:483-88.  Back to cited text no. 2
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3.Joiner A. The teeth bleaching: A review of the literature. J Dent 2006;34:412-419.  Back to cited text no. 3
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4.Dahl JE, Pallesen U. Tooth bleaching: A critical review of the biological aspects. Crit Rev Oral Biol Med 2003;14:292-304.  Back to cited text no. 4
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5.Titley K, Torneck CD, Smith DC. Effect of concentrated hydrogen peroxide solution on the surface morphology of cut human dentin. Endod and Dent Traumatol 1988;4:32-6.  Back to cited text no. 5
    
6.Rotstein I, Dankner E, Goldman A, Heling I, Stabholz A, Zalkind M. Histochemical analysis of dental hard tissues following bleaching. J Endod 1996;22:23-5.  Back to cited text no. 6
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7.Heling I, Parson A, Rotstein I. Effect of bleaching agents on dentin permeability to Streptococcus faecalis. J Endod 1995;21:540-2.  Back to cited text no. 7
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8.Harrington GW, Natkin E. External resorption associated with bleaching of pulpless teeth. J Endod 1979;5:344-8.  Back to cited text no. 8
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9.Madison S, Walton R. Cervical root resorption following bleaching of endodontically treated teeth. J Endod 1990;16:570-4.  Back to cited text no. 9
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10.Rotstein I, Torek Y, Misgav R. Effect of cementum defects on radicular penetration of 30% H2O2 during intracoronal bleaching. J Endod 1991;17:230-3.  Back to cited text no. 10
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11.MacIsaac AM, Hoen CM. Intracoronal bleaching: Concerns and considerations. Journal of Can Dent Assoc 1994;60:57-64.  Back to cited text no. 11
    
12.Fearon J. Tooth whitening: Concepts and controversies. International journal of Dentistry 2009;11:24-38.  Back to cited text no. 12
    
13.Chaves MG, Oliveira M, Pereira MN, Soares MR, Chaves Filho HD, Leite FP. Effects of external bleaching agents on dentinal tissues and cement-enamel junction. Dent Mater 2010;26.  Back to cited text no. 13
    
14.Potocnik IK, Kosec L, Gaspersic D. Effects of 10% carbamide peroxide bleaching gel on enamel microhardness, microstructure and mineral content. J Endod 2000;26:203-6.  Back to cited text no. 14
    
15.Patel S, Kanagasingam S, Pitt Ford T. External cervical resorption: A review. J Endod 2009;35:616-25.  Back to cited text no. 15
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16.Attin T, Paque F, Ajam F, Lennon AM. Review of the current status of tooth whitening with the walking bleach technique. Int Endod J 2003;36:313-29.  Back to cited text no. 16
    
17.Piesco NP. Histology of dentin. In: Avery JK, editor. Oral development and histology. New York: Theime Medical Publishers; 1994. p. 2.  Back to cited text no. 17
    
18.Chng HK, Palamara JE, Messer HH. Effect of hydrogen peroxide and sodium perborate on biomechanical properties of human dentin. J Endod 2002;28:62-7.  Back to cited text no. 18
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19.Lewinstein I, Hirschfeld Z, Stabholz A, Rotstein I. Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin. J Endod 1994;20:61-3.  Back to cited text no. 19
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20.Ho S, Goerig AC. An in vitro comparison of different bleaching agents in the discoloured tooth. J Endod 1989;15:106-11.  Back to cited text no. 20
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21.Garber DA. Dentist-monitored bleaching: A discussion of combination and laser bleaching. J Am Dent Assoc 1997;128:26-30.  Back to cited text no. 21
    
22.Ferreira EA, Souza-Gabriel AE, Silva-Sousa YT, Sousa-Neto MD, Silva RG. Shear bond strength and ultrastructural interface analysis of different adhesive systems to bleached dentin. Microsc Res Tech 2010.  Back to cited text no. 22
    


    Figures

  [Figure 1], [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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