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Table of Contents   
ORIGINAL RESEARCH  
Year : 2011  |  Volume : 22  |  Issue : 5  |  Page : 622-626
Comparison of apical sealing and periapical extrusion of the ThermaFil obturation technique with and without MTA as an apical barrier: An in vitro study


Department of Conservative Dentistry and Endodontics, HKE's S N Institute of Dental Sciences and Research, Gulbarga, Karnataka, India

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Date of Submission01-Sep-2010
Date of Decision07-Dec-2010
Date of Acceptance26-Jul-2011
Date of Web Publication7-Mar-2012
 

   Abstract 

Aim: The aim of the study was to compare the conventional ThermaFil obturation technique and ThermaFil obturation with mineral trioxide aggregate (MTA) as an apical barrier, with regard to apical sealing and extrusion.
Materials and Methods: Twenty extracted human canines were instrumented using a crown-down technique and divided into two groups. The experimental group was obturated using ThermaFil obturation with MTA as an apical barrier and the control group was obturated using the conventional ThermaFil obturation technique. AH Plus sealer was used in both the groups. Apical extrusion was recorded. Teeth of both the groups were coated with nail polish, except for the apical 3 mm. After 24 h, they were suspended in black India ink for 48 h. Canines were decalcified, rendered transparent, and linear dye penetration was measured under ×40 stereomicroscope.
Results: There was a significant extrusion noticed in conventional ThermaFil obturation technique. Frequency of extrusion of sealer and/or gutta-percha was supposed to be evaluated using χ² test, but since the values of the samples of ThermaFil plus MTA group were zero, statistical analysis could not be conducted, whereas linear dye leakage was calculated with Mann-Whitney U test because the distribution was abnormal.
Conclusion: Although ThermaFil plus MTA group showed microleakage, extrusion of sealer and the core material was prevented in comparison with conventional ThermaFil obturation technique. It is advantageous to use MTA as an apical plug as there is no fear of apical extrusion and the root canal system can then be packed three dimensionally against this barrier using any thermoplasticized gutta-percha obturation technique.

Keywords: Apical barrier, microleakage, mineral trioxide aggregate, periapical extrusion, ThermaFil obturation

How to cite this article:
Kumar S, Deshpande S J, Rao AS. Comparison of apical sealing and periapical extrusion of the ThermaFil obturation technique with and without MTA as an apical barrier: An in vitro study. Indian J Dent Res 2011;22:622-6

How to cite this URL:
Kumar S, Deshpande S J, Rao AS. Comparison of apical sealing and periapical extrusion of the ThermaFil obturation technique with and without MTA as an apical barrier: An in vitro study. Indian J Dent Res [serial online] 2011 [cited 2020 Jan 21];22:622-6. Available from: http://www.ijdr.in/text.asp?2011/22/5/622/93445
Periradicular lesions of endodontic origin have been associated with the presence of bacteria and their byproducts in infected root canal system. [1] The primary treatment for these lesions is nonsurgical orthograde root canal therapy. [2] Ideally, this procedure should exclude bacteria and their byproducts from the periapical tissues, allowing regeneration or repair of these tissues to take place. Chemicomechanical cleaning and shaping of the root canal system removes a great deal of the microorganisms, but total debridement is impeded because of the complex root canal system with accessory canals, fins, cul-de-sacs, and communication between the main canals. [3] Hence, a three-dimensional obturation of the root canal system is required to entomb these remaining bacteria. In the process to achieve this goal, Johnson introduced a new obturation technique using flexible metal carriers coated with α-phase gutta-percha (ThermaFil Endodontic Obturator, Tulsa Dental Products, Tulsa, OK, USA). The advantage of this technique was the flow of the thermoplasticized gutta-percha into lateral and accessory canals, thus providing the three-dimensional obturation of the root canal system. [4]

Many studies have reported that the apical sealing ability of ThermaFil obturation is similar to that of gold standard lateral condensation technique. [5],[6],[7],[8],[9],[10],[11],[12],[13] However, the main disadvantage of this technique is the apical extrusion of the sealer and gutta-percha. ThermaFil technique produced a significantly greater incidence of apical extrusion when compared with the lateral condensation technique, as shown by studies of Gutman et al.[14] and Clark and ElDeeb. [15]

Various techniques have been tried to create a tight apical barrier against which the obturation can be done without the fear of apical extrusion, e.g. dentin chip apical filling, [16],[17],[18] calcium hydroxide apical filling. [19],[20],[21] However, each one of these has their own disadvantages. Holland et al.[22] found that if the dentin chips are infected, they can be a serious deterrent to healing, and Torneck et al.[23] found that some dentin chips may actually irritate and hinder repair. Pitts et al.[24] found that calcium hydroxide resorbs away from the apex faster than do dentin chips, resulting in increased microleakage over a period of time.

Recently, Torabinejad et al. introduced mineral trioxide aggregate (MTA) which provides an effective seal against dentin and cementum and promotes biologic repair and regeneration of the periodontal ligaments. [25],[26] Because of above-mentioned properties, the next logical application of this material could be its use as a tight sealing apical barrier against which the rest of the canal can be obturated without the fear of periapical extrusion.

Aim of the study

Hence, the aim of the study was to compare the conventional ThermaFil obturation technique and ThermaFil obturation with MTA as an apical barrier, with regard to apical sealing and periapical extrusion.


   Materials and Methods Top


Twenty extracted human canines with similar shapes and dimensions were selected and stored in 10% formalin solution. All teeth were numbered and stored for 6 h in 3% sodium hypochlorite solution to remove the attached tissues before access preparation. Teeth were divided into two groups: (a) the experimental group was obturated using ThermaFil obturation with MTA in the apical 1 mm and (b) the control group was obturated using the conventional ThermaFil obturation technique.

Preparation of specimens

Access preparation was done using round bur and high-speed airotor handpiece. Canal length was determined visually by passing a size 15 file into the canal until it was flush with the root surface at apical foramen. Working length was established by subtracting 0.5 mm from this length.

Canal instrumentation

Periapical radiographs from a proximal and buccolingual surface were taken with different files in each canal to verify the canal length. All canals were prepared mechanically with the pro-taper endodontic instruments (Dentsply, Maillefer, Ballaigues, Switzerland) using a crown-down technique in sequence of shaping instruments S1 and S2 up to the working length, followed by finishing instruments F1, F2, F3, F4 and F5. 3% sodium hypochlorite solution was used to irrigate the canals between the usages of each instrument. The final apical preparation was performed with finishing instrument F5. Prepared specimens were irrigated and dried with paper points.

Canal obturation

After instrumentation, the canals were divided into two groups. The experimental group was obturated with ThermaFil obturation technique with MTA in the apical 1 mm of the root canal and the control group was obturated with conventional ThermaFil obturation technique.

Conventional ThermaFil obturation group

The canals of the ThermaFil group were obturated as specified by the manufacturer. We selected a ThermaFil obturator of the same size as the size verifier (#50) that fitted passively at working length. A rubber stop was adjusted to coincide with the working length. The obturator was heated in the Therma Prep Oven (Dentsply, Maillefer) automatically regulated for 17 seconds. Sterile paper points were used to coat the canal walls till the working length with AH Plus sealer. The shaft level was severed at orifice using a tungsten carbide inverted cone bur in a high-speed handpiece. The carrier was stabilized with the index finger.

Radiographs were taken from the buccal and mesial aspects of each tooth to visually evaluate the obturation [Figure 1].
Figure 1: ThermaFil obturation without MTA

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ThermaFil obturation with MTA as an apical barrier group

The canals of this group were obturated in two parts.

MTA was mixed with sterile water and carried into the canal with the help of an appropriate amalgam carrier and this was condensed in the canal to seal the apical 1 mm with the help of a hand plugger. The hand plugger which fitted passively 1 mm short of the working length when inserted in the canal was selected to plug the MTA in the canal and most of the time it coincided with the no. 55 hand plugger. In case it did not fit passively, one size smaller or larger plugger was selected as needed. It was later checked with a radiograph, and in case the apical seal obtained was not satisfactory, the samples were discarded [Figure 2].
Figure 2: 1 mm of MTA as apical barrier

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Secondly, the rest of the canal was obturated with ThermaFil obturation technique. Sterile paper points were used to coat the walls of the canals at the working length with AH Plus sealer.

Radiographs were taken from the buccal and mesial aspects of each tooth to visually evaluate the obturation [Figure 3].
Figure 3: ThermaFil obturation with MTA

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Extrusion measurements

The apex was observed with a magnifying glass by two blinded observers, and in case of doubt, the higher value was considered. The observations were recorded using the following parameters:

0 Rating - No sealer or gutta-percha at the foramen.

1 Rating - Sealer and/or gutta-percha only at the foramen.

2 Rating - Sealer and/or gutta-percha beyond the foramen.

Microleakage measurements

The obturated roots were dried and coated on their external surfaces with nail polish, except for the apical 3 mm. A second layer of a different color was applied after the first layer had dried.

After the polish had dried, the specimens were immersed in black India ink at 37°C for 48 h. They were then thoroughly washed with physiological saline, and the varnish was carefully removed with a lecron carver, and the teeth were dried for 24 h. Samples were first cleared by placing them in 5% nitric acid, dehydrated with ascending concentration of ethyl alcohol, and cleared again in methyl salicylate. Linear apical dye penetration was measured for each specimen using a stereo zoom microscope at ×40 magnification [Figure 4].
Figure 4: Representative cleared specimens of both groups

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   Results Top


Extrusion

The percentage of canals with extruded sealer and/or guttapercha in each technique is given in [Table 1]. There was a significant extrusion noticed in conventional ThermaFil obturation technique.
Table 1: Incidence (%) of apical extrusion between conventional ThermaFil and ThermaFil plus MTA techniques

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Apical leakage

The mean leakage and SD values for each technique are presented in [Table 2]. A significant difference between the two groups was observed with ThermaFil plus MTA group showing higher amount of leakage.
Table 2: Mean leakage values of both groups

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Statistical analysis

Frequency of extrusion of sealer and/or guttapercha was supposed to be evaluated using χ² test, but since the values of the samples of ThermaFil plus MTA group were zero, statistical analysis could not be conducted, whereas linear dye leakage was calculated with Mann-Whitney U test because the distribution was abnormal.


   Discussion Top


MTA was developed at Loma Linda University by Torabinejad in 1993 as a root end filling material. The use of MTA as a root end filling material was identified because the material is hydrophilic and sets in the presence of water. [27] MTA received acceptance by the US Federal Drug Administration and became commercially available as ProRoot MTA (Tulsa dental products, Tulsa, OK, USA). [28]

Advantages of MTA

Physiochemical property of MTA

When MTA is compacted against dentin, it forms dentin-MTA interfacial layer over a long period of time and this layer resembles hydroxyapatite in structure and composition. [29] MTA is not only bacteriostatic but also bactericidal. Because of the release of hydroxyl ions, it sustains high pH for extended period of time and this makes it a potent inhibitor of  Enterococcus faecalis Scientific Name Search andida albicans which are considered as the most common species associated with the root canal failure cases. [30]

Bioactivity of MTA

MTA is bioactive silicate cement that is non-irritating to periapical tissues and also induces the regeneration of cementum and the periodontal ligament(PDL) [31],[32] Histological studies revealed biologic closure of apical foramen by the synthesis of new cementum and the generation of the PDL in the absence of inflammation. [33]

Sealing properties of compacted MTA

The sealing ability MTA has been shown to be superior to the other conventional materials used in Endodontics. [34],[35] MTA has been shown to resist leakage at a higher rate when placed in moist environment. [36] Another investigation suggested that 24-hour set gray MTA showed significantly less leakage than white MTA and that a 5-mm apical barrier of gray MTA provided the best apical barrier (allowing 24 hours for the MTA to set). [37] One more investigation showed that MTA placed without ultrasonic energy and challenged with a bacterial leakage model showed 100% leakage at the end of a 70-day test period. [38]

Analysis of the results

Microleakage

Even though microleakage was observed, the harmful effects due to microleakage have been counteracted by the antimicrobial properties of MTA. Also, as mentioned above, it is the intracanal delivery technique and not the MTA that contributes to the leakage as observed. By far, none of the obturation techniques have been shown to stop the microleakage absolutely. Microleakage can be minimized by manipulating MTA according to the manufacturer's instructions, improving the intracanal delivery technique, and providing sufficient time for the material to set.

Apical extrusion

MTA showed a great promise in our experiment in the prevention of apical extrusion of gutta-percha and sealer.


   Conclusion Top


It is advantageous to use MTA as an apical plug as there is no fear of apical extrusion and the root canal system can then be obturated three dimensionally against this barrier using any thermoplasticized gutta-percha obturation technique.


   Future Prospects Top


Further studies are required to improve the placement of MTA in the root canal with ultrasonic energy and to improve the setting time of the MTA because fast setting MTA would be beneficial and, above all, clinical trials are still required.

 
   References Top

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Correspondence Address:
S J Deshpande
Department of Conservative Dentistry and Endodontics, HKE's S N Institute of Dental Sciences and Research, Gulbarga, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.93445

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    Figures

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    Tables

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