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Table of Contents   
ORIGINAL RESEARCH  
Year : 2014  |  Volume : 25  |  Issue : 2  |  Page : 143-146
Histological evaluation after electrothermal debonding of ceramic brackets


1 Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra University, Porur, Chennai, Tamil Nadu, India
2 Department of Orthodontics and Dentofacial Orthopedics, College of Dental Surgery, Manipal, Karnataka, India
3 Dean, Manipal College of Dental Sciences, Manipal, Karnataka, India

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Date of Submission21-Feb-2011
Date of Decision18-Oct-2011
Date of Acceptance01-Mar-2014
Date of Web Publication4-Jul-2014
 

   Abstract 

Aim: To evaluate the histological changes following electrothermal debonding (ETD) of ceramic brackets.
Materials and Methods: A total of 50 first premolar teeth from 14 patients were divided into two groups: Group I consisted of 20 teeth which served as control, and the brackets were debonded using conventional pliers. (7 teeth were extracted 24 hours after conventional debonding, 7 teeth were extracted 28 to 32 days after conventional debonding and 6 teeth were extracted 56-60 days after conventional debonding). Group II consisted of 30 teeth and the brackets were debonded using the ETD unit. (10 teeth were extracted 24 hours after ETD, 10 teeth were extracted 28 to 32 days after ETD and 10 teeth were extracted 56-60 days after ETD. Immediately after extraction, the teeth were sectioned and prepared for histological examination.
Results: The pulp was normal in most samples of the control group. In group II, mild inflammation was observed in the 24 hour sample while the 28 to 32 day sample showed signs of healing. The 56-60 day sample showed that the pulp was similar to the control group in 6 out of the 10 samples.
Conclusion: The ETD of ceramic brackets did not affect the pulp and the changes which were observed, were reversible in nature.

Keywords: Ceramic brackets, electrothermal debonding, pulp response 

How to cite this article:
Kailasam V, Valiathan A, Rao N. Histological evaluation after electrothermal debonding of ceramic brackets. Indian J Dent Res 2014;25:143-6

How to cite this URL:
Kailasam V, Valiathan A, Rao N. Histological evaluation after electrothermal debonding of ceramic brackets. Indian J Dent Res [serial online] 2014 [cited 2020 Jul 9];25:143-6. Available from: http://www.ijdr.in/text.asp?2014/25/2/143/135902
Attempts to improve an esthetic appearance of the orthodontic appliance have resulted in the development of the bonded brackets, that uses the acid etch technique to minimize the metallic appearance of bands. Other attempts at esthetic orthodontic appliances include lingual appliances, plastic brackets and finally ceramic brackets. [1]

The adhesives used for direct bonding have become so efficient that the removal of the bonded brackets can be difficult, especially in the case of ceramic brackets. Ceramic brackets have excellent properties of esthetics, strength and rigidity but lack the ductility of metal. The brittle nature of ceramic brackets has resulted in a higher incidence of fracture during debonding. [2],[3],[4],[5]

The term debonding refers to the removal of orthodontic brackets and residual adhesive from the enamel of the teeth. Effective debonding of bonded attachments may vary according to the bracket type, [4],[5],[6],[7],[8],[9] retention method, [7],[9] type of adhesive, [9],[10] enamel conditioning, [7],[11],[12] curvature of tooth and importantly, the debonding technique used. The most common debonding techniques used employ debonding pliers, [13],[14],[15] hand scalers, [13],[15],[16],[17] green rubber wheels, [13],[17] assorted rotary instruments [15],[16],[18] and automatic hand pieces. [19]

The conventional technique of bracket removal requires shearing or compression forces. The force necessary to separate the bracket from the tooth is sufficient to cause deformation of the bracket and in some cases, is capable of damaging the tooth or there may be fracture of the bracket itself. [20],[21]

An alternative method to conventional bracket removal that minimizes the potential for ceramic bracket fracture is electrothermal debonding (ETD), which was first described by Sheridian et al. in 1986. [22] Preliminary, in vitro and in vivo studies of ETD have been conducted on metal brackets by Sheridian et al. [22] However, the effects on the pulp using ETD on ceramic brackets still needs further assessment. Hence, the aim of this study was to assess the pulpal damage, if any, caused by electrothermal debonding (ETD) by histologically assessing the human pulp after ETD.


   Materials and methods Top


Fourteen patients, who had to undergo first premolar extractions as a part of their orthodontic treatment were selected for the study. A total of 50 premolars were thus identified. The criteria for the selection were that, these teeth were free of caries and did not display any signs of trauma. The facial surfaces of these teeth were bonded with ceramic brackets (Fascination -Dentaurum Company, Pforzheim, Germany) with Right on No Mix bonding System (T P Orthodontics, La Porte Indiana, USA) using the conventional bonding procedure.

These 50 first premolar teeth from 14 patients were randomly divided into two groups: Group I (mean age 22 years 4 months) served as a control and consisted of 20 bonded teeth. The brackets bonded to these teeth were then debonded using conventional pliers. 7 teeth were then extracted after 24 hours, 7 teeth were extracted after 28 to 32 days, and 6 teeth were extracted 56-60 days after the debonding. Group II (mean age 22 years 6 months) consisted of 30 bonded teeth. The brackets bonded to these teeth were then debonded using the electrothermal debonding unit (Dentaurum Company, Pforzheim, Germany). 10 of these teeth were extracted 24 hours after ETD, 10 were extracted 28 to 32 days after ETD and 10 were extracted 56-60 days after ETD. Immediately after an extraction, the teeth were sectioned and prepared for the histological examination by storing them in a 10% buffered neutral formalin solution. The teeth were subsequently decalcified, embedded in paraffin and 5 μm sections were obtained. The sections were stained with hematoxylin and eosin and were evaluated with a visible light microscope at 10 to ×40 magnification (Olympus, New Delhi, India). The histological parameters studied were the presence or absence of mesenchymal cells, vascular engorgement and extravasation with red blood cells, inflammatory cells, pulpal necrosis and abscess, while the dentinal changes evaluated included the odontoblastic reaction, embedding of odontoblasts, predentin reduction and presence or absence of atubular irregular dentin.


   Results Top


Control group: 5 of the 7 teeth in the 24 hour and 28-32 day sample and 4 of the 6 teeth in the 56-60 day sample, showed normal pulp under histologic section. Thus 14 of the 20 teeth in the control group were normal. The changes observed in the remaining 6 samples were mainly vascular engorgement and extravasation of red blood cells (RBC) which were of a mild nature. Dentinal changes were nil. In the experimental group, 9 of the 10 sections in the 24 hour sample showed histologic changes. They showed intense hyperemia, vascular engorgement and extravasation of RBCs. 5 of the 10 samples in the 28-32 day sections and 4 of the 10 samples in the 56-60 day sections showed histologic changes [Table 1] and [Figure 1], [Figure 2], [Figure 3].
Figure 1: Photomicrograph of a sample 24 hours following ETD showing dilated blood vessels with red blood cells filling the lumen

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Figure 2: Photomicrograph of a sample 28-32 days following ETD showing increased cellularity

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Figure 3: Photomicrograph of a sample 56 days following ETD showing almost normal pulpal architecture

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Table 1: Histologic evaluation of the teeth


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   Discussion Top


ETD is the technique of removing bonded brackets from enamel surfaces with a rechargeable battery device that generates heat. It has a cylindrical hand piece containing an element that is heated to approximately 450°F as the unit is activated. [23] To allow bracket debonding with ETD, the adhesive softens at a critical temperature between 300°F and 392°F. [24] Dentin being a poor conductor of heat usually protects the pulp from this high temperature. [6],[25],[26]

The ceramic debonding unit used in this study utilizes a debonding cycle, which lasts for a total period of 9 seconds. During the first 3 seconds, the heating element is heated to reach the temperature needed for debonding. In the next 6 seconds, the heating element begins its cooling phase.

In the control group, the pulp was normal in most sections. The vascular changes observed were minimal and could be due to an extraction procedure. Since the bonding material was also not removed prior to extraction, the changes could be attributed to strangulation and trauma to the pulp during extraction.

The effects seen at 24 hours after ETD were-hyperemia, engorgement and dilation of the blood vessels with extravasation of the red blood cells (RBCs) implying the start of an inflammation [Figure 1]. The pulpal response could be due to the insult of heat on the pulp. Heat conducted to the pulp through the dentin would cause vasodilation, resulting in an increased blood flow to the pulp, which is one of the first responses during an inflammatory reaction. If this inflow is greater than the blood outflow, the situation results in pulpal hyperemia and engorgement. The situation is reversible, depending on an initial status of the pulp and its ability to repair.

Mild inflammation was observed following ETD in the 28-32 day sample also [Figure 2]. The presence of this mild inflammation could possibly be explained by an inadequate healing time, and thus insufficient for the pulp to return to normal. Since the degree of an inflammatory response was mild, it can be inferred that the pulp was undergoing a healing process which was not complete in all the samples.

The samples which were observed 56-60 days after ETD, showed that the pulp architecture was predominantly normal. Thus, it can be inferred that the healing process was continuing. The results of this study differ with Sheridian et al., [27] who did an in vivo study with metal brackets and reported no evidence of pulpal disease, whereas hyperemia and extravasation of rbcs were observed in this study. The results are in accordance with those reported by Takla and Shivpuja. [23] Although they reported a higher degree of inflammation following ETD in the 28 to 32 day category, Dovgan et al. [28] reported that there was evidence of chronic inflammation while this study revealed an acuteinflammatory reactions.

Sheridian et al. [27] stated that, the correlation between the difference in dentin thickness in different teeth and an amount of heat conducted into the pulpal chamber was insignificant. According to Takla and Shivpuja, [23] premolar enamel and dentin thickness beneath the bonded bracket is thicker than for upper and lower incisors. Hence, there is less structural insulation for the pulp and potentially more adverse incisor pulp reaction. The sample for this study was teeth from a younger age group. Therefore, it could be inferred that they would have a rich blood supply and hence the ability to heal faster. Further, patients with compromised teeth that have large restorations or a questionable pulp status, could behave more adversely to this heat. Takla and Shivpuja [23] have recommended the performance of pulp vitality tests before ETD on these patients.

The important factor would be the amount of heat that is conducted to the pulp. It is not known how a high temperature human teeth can withstand before irreversible pulpal damage occurs. Sheridian et al. [22] reported that, the mean change in pulpal wall temperature was 3.2°C when human maxillary incisors were debonded in vitro with a thermal device.

Crooks et al. [29] reported that, by varying the resin type and thickness, the temperature of the pulpal wall during ETD may be altered. Though the resin was standardized in this study, the resin thickness could have been a variable. Rueggeberg and Lockwood [30] reported that, lower temperature changes during ETD with no mix systems when compared with two paste systems and this could be due to an incomplete resin polymerization in the two paste systems, which may have occurred due to an incomplete diffusion. However, in a later study in 1992, Rueggeberg and Lockwood [31] reported that, only the powder-liquid resins resulted in significantly lower temperature changes, a finding which was also reported by Crooks et al. [29] Thus the difference in the physical properties of the filler type in the resin may also alter an amount of heating reaching the pulp.


   Conclusion Top


The ETD of ceramic brackets found that, the pulp was predominantly unaffected by this procedure with most of the changes being of a reversible nature. The 24 hour sample showed that the pulp was hyperemic while the 28 to 32 day sample showed that the pulp was hyperemic with mild features of inflammation and the 56-60 day sample showed that the pulp was hyperemic, but the intensity had reduced and could lead to the conclusion that healing was taking place. Further, the changes observed were more or less similar to the control group, indicating that the changes observed could also be due to an extraction of the tooth.

 
   References Top

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28.Dovgan JS, Walton RE, Bishara SE. Electrothermal debracketing: Patient acceptance and effects on the dental pulp. Am J Orthod Dentofacial Orthop 1995;108:249-55.  Back to cited text no. 28
    
29.Crooks M, Hood J, Harkness M. Thermal debonding of ceramic brackets: An in vitro study. Am J Orthod Dentofacial Orthop 1997;111:163-72.  Back to cited text no. 29
    
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Correspondence Address:
Vignesh Kailasam
Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra University, Porur, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.135902

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    Figures

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    Tables

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