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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 6  |  Page : 857-861
Evaluation of remaining dentin thickness around the prepared root canals and its influence on the temperature changes on the external root surfaces during different heated gutta-percha obturation techniques


Department of Conservative Dentistry and Endodontics, Tagore Dental College and Hospital, Chennai, Tamil Nadu, India

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Date of Submission20-Jun-2019
Date of Acceptance16-Jul-2019
Date of Web Publication22-Mar-2021
 

   Abstract 


Context: Temperature rise on external root surface has a deleterious effect on the periodontium. Aims: To compare and evaluate the temperature changes on the external root surfaces using three different heated gutta-percha obturation techniques and also to evaluate the effect of remaining dentin thickness (RDT) on the temperature rise during obturation. Settings and Design: In vitro study with a customized temperature measurement setup. Materials and Methods: Thirty decoronated human maxillary central incisors were cleaned and shaped using standardized method. RDT was measured using cone beam computed tomography. They were divided into three groups of 10 samples each. Group 1 was obturated by traditional warm vertical compaction, Group 2 using solid core obturation, and Group 3 by warm vertical compaction technique using GP heater in vibration mode. AH Plus sealer was used as cement sealer. During obturation, the temperature rise was measured using K-type thermocouples in the coronal, middle, and apical thirds. The highest temperature rise during the procedure was recorded. Statistical Analysis Used: Data were analyzed by one-way analysis of variance and post hoc Tukey's test. Results: Traditional warm vertical compaction had the highest temperature change followed by warm vertical compaction using GP heater in vibration mode and solid core obturation. Conclusion: There was a temperature rise on external root surfaces in the three techniques evaluated. Solid core obturation technique showed the least temperature change. There was no significance in the effect of RDT on temperature rise during obturation.

Keywords: Cone beam computed tomography, gutta-percha, obturation

How to cite this article:
Balagopal S, Bejoy Mony C M, Hemasathya BA, Nazrin M, James V, Sebatni A. Evaluation of remaining dentin thickness around the prepared root canals and its influence on the temperature changes on the external root surfaces during different heated gutta-percha obturation techniques. Indian J Dent Res 2020;31:857-61

How to cite this URL:
Balagopal S, Bejoy Mony C M, Hemasathya BA, Nazrin M, James V, Sebatni A. Evaluation of remaining dentin thickness around the prepared root canals and its influence on the temperature changes on the external root surfaces during different heated gutta-percha obturation techniques. Indian J Dent Res [serial online] 2020 [cited 2021 Aug 2];31:857-61. Available from: https://www.ijdr.in/text.asp?2020/31/6/857/311658



   Introduction Top


Long-term success of endodontic therapies depends on obturation.[1] Cold lateral compaction is the gold standard to compare the efficacy of other obturation techniques.[2] But this technique leaves voids with irregular distribution of sealer.[3] Hence, thermoplasticized gutta-percha (GP) techniques are used to give denser fillings within short durations.[4],[5],[6] However, the temperature changes on external root surfaces during obturation may have deleterious effects on the surrounding periodontium.

Apart from Schilder's warm vertical compaction, many newer GP warmed techniques make obturation easier for dentists and patients. It is commonly perceived that remaining dentin thickness (RDT) determines the temperature changes on external root surface during obturation.


   Aims Top


The aims of this study were as follows:

  1. To compare and evaluate the temperature changes on the external root surfaces using three different obturation techniques – traditional warm vertical compaction, solid core obturating material, and warm vertical compaction with GP heater with vibration mode device.
  2. To evaluate the effect of RDT on the temperature rise during these obturation procedures.



   Alternate Hypotheses Top


  1. Intracanal warmed GP techniques can rise the external root surface temperature that can be injurious to the periodontium.
  2. Temperature rise on the root surface is dependent on the RDT.



   Materials and Methods Top


Materials used

  1. D345-190 NTI Flex Diamond Disc (Kerr, USA).
  2. Gates Glidden – # 4, 3, 2, 1 (Dentsply Maillefer, USA)
  3. #15–40, 21 mm assorted (5247) and #45–80, 21 mm assorted (5248) K-files (Mani Inc., Japan)
  4. 5% sodium hypochlorite (Prime Dental Products Pvt. Ltd., India)
  5. Triple distilled water (J.K. Laboratories, India)
  6. 17% EDTA (RC Help, Prime Dental Products Pvt. Ltd., India)
  7. Cone Beam Computed Tomography (Orthophos XG 3D, Dentsply Sirona, USA)
  8. AH Plus (Dentsply DeTrey, Konstanz, Germany)
  9. 10-1/2 anterior root canal plugger, RCP10-1/2A (Hu-Friedy Manufacturing Co., USA).
  10. Gutta-Percha points – (Dentsply Maillefer, Switzerland).
  11. ThermaPrep plus with ThermaFil (Dentsply Sirona, Tulsa, USA).
  12. GP Easy II (Apoza, Taiwan)
  13. Hindustan Modelling wax no. 2 (The Hindustan Dental Products, India)
  14. K-type thermocouples, L-type connector, OL-102 Knob, K-type temperature indicator, three-way shunt-type integral switch – customized setup by RR Traders and Co. (India).


Methodology

Approval for this study was granted by the Institutional Research Committee of Tagore Dental College and Hospital, Tamil Nadu, India (on 12.12.2018). Thirty human maxillary central incisors with single canal and complete root formation, which were extracted for periodontal reasons, were included in this study. Teeth with root caries, root fracture, and developmental anomalies were excluded. All the samples were decoronated using Diamond Disc with water as a coolant such that the root lengths were standardized to 12 mm. The samples were randomly numbered from 1–30 with a permanent marker.

The working length was determined to be 1 mm shorter from the apical foramen. Coronal preparation was done using Gates Glidden drills #4, 3, 2, 1. Apical preparation was standardized to #50 with K-files and step-back preparation was performed upto #80 K-files. Irrigation was done with 5 mL of 5% sodium hypochlorite, triple distilled water, and 17% EDTA as canal conditioner after each instrumentation. These samples were mounted on wax [Figure 1] and subjected to CBCT analysis [Figure 2] for the measurement of RDT [Figure 3] and [Figure 4].
Figure 1: Teeth placed in wax jig

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Figure 2: CBCT machine (Orthophos XG 3D, Dentsply Sirona, USA)

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Figure 3: CBCT images of samples

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Figure 4: Remaining Dentin Thickness measurement in each thirds

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Thirty samples were divided into three groups containing 10 samples each. The canals were dried with paper points. AH Plus sealer was used and obturation was completed.

Group 1 – Obturated by traditional warm vertical compaction (Schilder's technique)

Group 2 – Obturated using ThermaFil solid core obturation technique. ThermaPrep plus obturator oven (Dentsply Sirona, Tulsa) using ThermaFil obturators (Dentsply Maillefer) is a carrier-based obturating system which has gained a lot of popularity due to the ease of obturation and an excellent radiographic display of the obturation.

Group 3 – Obturated using GP Easy II warm vertical compaction using GP heater in vibratory mode. GP Easy II (Apoza) is a newer obturating device which uses heat and vibration to cut, soften, and compact GP in the root canal.

During obturation, the temperature rise on the mesial aspect of external root surface of each sample was measured using three type K thermocouples (Chromel/Alumel) attached in the coronal, middle, and apical thirds (at 2.5, 6.5, and 10.5 mm, respectively, from the apex) and stabilized with wax. These three thermocouples were connected with L-type connector to a three-way shunt-type integral switch which was then connected to OL-102 Knob and finally connected to a temperature indicator (K-type) for displaying the temperature rise. The knob helps switch the temperature measurement from one-third to the other and makes the indicator to digitally display the temperature change. This was a fully customized setup. The highest temperature rise was recorded [Figure 5] and [Figure 6].
Figure 5: Temperature rise measurement by thermocouples during obturation

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Figure 6: Customized set-up for temperature measurement during obturation

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Statistical analysis

The values were entered into an Excel sheet (Microsoft) for calculation. With the recorded temperature changes, the temperature rise on external root surfaces using different obturation techniques was evaluated. The effect of RDT on the temperature change was also analyzed. One-way analysis of variance and post hoc Tukey's tests, respectively, were the tests used.


   Results Top


The mean temperature rise and RDT of samples under each group in their corresponding thirds are shown in [Table 1].
Table 1: Mean temperature rise and RDT of samples under each group in their corresponding thirds

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The overall temperature rise was more in the warm vertical compaction group which was followed by GP Easy II warm vertical compaction in the vibratory mode group. The ThermaFil solid core obturation group had lesser temperature changes.

Group 1 and Group 2 were statistically significant (P < 0.01) [Graph 1].



In comparison to root surface thirds,

Group 1 – temperature rise was maximum in the coronal third, followed by middle and apical thirds (Tukey's post-test, P < 0.01),

Group 2 – temperature rise was highest in the apical third, followed by middle and coronal thirds, and

Group 3 – temperature rise was recorded the maximum in the middle third and other thirds had similar temperature changes [Graph 2].




   Discussion Top


The main reason for this study was to evaluate the amount of temperature changes caused by different thermoplasticized GP obturation techniques. The disadvantages of such techniques are the increase in temperature inside the canal and dissipation of the same to the external root surface.[7] According to Eriksson et al., if the temperature rises to 60°C or more, there will be a permanent blood flow cessation followed by bone necrosis.[8],[9] The critical limit for preserving the surrounding periodontium is accepted to be 10°C rise in temperature.[8] The exact temperature at which reversible or irreversible periodontal injuries will occur has not been verified experimentally. Alkaline phosphatase is denatured around 46°C and this is thought to be the critical limit. According to Zhang et al., when the temperature rises to 47°C, there was release of sRANKL, which promoted osteoclastogenesis and induced bone resorption in the local environment.[10]

In this study, the effect of RDT on temperature rise was also evaluated. The expected result was that the temperature rise on the external root surfaces would be inversely proportional to RDT.[11] According to Budd et al., teeth with less root volume would be expected to have higher temperature rises than those roots with larger volumes during the removal of post using ultrasonics.[12] According to Lee et al., there was no significant relationship between temperature rise and RDT among the tooth groups in their study.[13] But in our study the temperature rise was independent of RDT.

CBCT was used to evaluate the RDT at various thirds. According to Hatton et al., accuracy of the ultrasonography in measuring the thickness of dentin discs in vitro was superior to micrometer measurements.[14] Fujita et al. used optical coherence tomography to explore the possibility of measuring RDT.[15] Traditional methods such as sectioning and muffle techniques cause destructive sectioning of specimens and physical reassembly of sections.[16] Hartmann et al. recommended CBCT to be a reliable method which shows no destructive sectioning of specimens.[17]

In this study, K-type chromium aluminium thermocouples, which are considered to be the traditional gold standard of temperature measurement, were used to measure the temperature changes on external root surfaces. They can sense temperature changes both inside and outside the canals.[7],[18] In this study, temperature changes in each third were measured and so the temperature change in one third at specific pin point mean area can be compared with that of the other thirds. They work on the principle that when two dissimilar metals are joined together to form two junctions, electromotive force is generated within the circuit due to the different temperatures of the two junctions of the circuit (Peltier effect). The only limitation is that it can measure temperature only at one point of the contacting surface.

Infrared thermographic analysis is another method to record temperature changes. The accuracy of the thermal imaging system depends on the emissivity of the material which is analyzed.[19] It records temperatures over a large surface area with the help of software packages which can identify points of temperature extremes and can record a real-time video image of temperature changes in color representation.[20]

Traditional warm vertical compaction had the highest temperature change in the coronal third. This may be attributed to the fact that the heat carrier/plugger contacts the coronal third more than the other two thirds (especially the coronal 3–4 mm).[21]

In solid core obturation, the molten GP produced by extracanal warming when introduced into the canal reaches the apical third and this initial high temperature is recorded as the highest. Due to extracanal heating of GP, this technique had the least temperature rise.

In warm vertical compaction by GP heater with vibration mode device, which is more like an automated version of warm vertical compaction technique, the tip (Tip#4-GP 040/.06) contacts the middle third for a longer duration and, thus the temperature was higher in that corresponding third.

Although this is an in vitro study, a thorough understanding of temperature rise on root surfaces using different obturation techniques is necessary, to curtail the ill effects produced by higher temperature rises to the surrounding periodontium. However, the values might vary in in vivo studies due to the surrounding periodontium, saliva, and so on.

The main limitation is that the periodontium was not simulated. The temperature and duration of each obturation technique vary. The results obtained (comparing RDT and temperature rise during obturation) cannot be compared with other studies, as this study was the first of its kind.


   Conclusion Top


Within the limitations of this in vitro study, it was concluded that

  1. Temperature rise was maximum in traditional warm vertical compaction technique, especially in the coronal third. The least temperature rise was recorded in solid core obturation technique.
  2. RDT had no effect on temperature rise as the latter was technique-dependent.



   Hypotheses Top


  1. Partially rejected – The intracanal warmed GP technique raised the external root surface temperature to high levels but did not rise it to the level that could be injurious to the periodontium.
  2. Rejected – Temperature rise did not depend on RDT.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Katebzadeh N, Sigurdsson A, Trope M. Radiographic evaluation of periapical healing after obturation of infected root canals: An in vivo study. Int Endod J 2000;33:60-6.  Back to cited text no. 1
    
2.
Smith CS, Setchell DJ, Harty FJ. Factors influencing the success of conventional root canal therapy – A five-year retrospective study. Int Endodontic J 1993;26:321-33.  Back to cited text no. 2
    
3.
Jarret IS, Marx D, Covey D, Karmazin M, Lavin M, Gound T. Percentage of canals filled in apical cross sections – An in-vitro study of seven obturation techniques. Int Endod J 2004;37:392-8.  Back to cited text no. 3
    
4.
Buchanan LS. The continuous wave of condensation technique: A convergence of conceptual and procedural advances in obturation. Dent Today 1994;13:80, 82, 84-5.  Back to cited text no. 4
    
5.
Clinton K, Van Himel T. Comparison of a warm gutta-percha obturation technique and lateral condensation. J Endod 2001;27:692-5.  Back to cited text no. 5
    
6.
Collins J, Walker MP, Kulild J, Lee C. A comparison of three gutta-percha obturation techniques to replicate canal irregularities. J Endod 2006;32:762-5.  Back to cited text no. 6
    
7.
Molyvdas I, Zervas P, Lambrianidis T, Veis A. Periodontal tissue reactions following root canal obturation with an injection thermoplasticized gutta-percha technique. Endod Dent Traumatol 1989;5:32-7.  Back to cited text no. 7
    
8.
Eriksson A, Albrektsson B, Grane, Macqueen D. Thermal injury to bone: A vital microscopic description of heat effects. Int J Oral Surg 1982;11:115-21.  Back to cited text no. 8
    
9.
Eriksson AR, Albrektsson T. Temperature threshold levels for heat-induced bone tissue injury: A vital-microscopic study in the rabbit. J Prosthet Dent 1983;50:101-7.  Back to cited text no. 9
    
10.
Zhang L, Zhou X, Wang Q, Wang Y, Tang L, Huang D. Effect of heat stress on the expression levels of receptor activator of NF-kB ligand and osteoprotegerin in human periodontal ligament cells. Int Endod J 2012;45:68-75.  Back to cited text no. 10
    
11.
Madarati AA, Qualtrough AJ, Watts DC. Factors affecting temperature rise on the external root surface during ultrasonic retrieval of intracanal separated files. J Endod 2008;34:1089-92.  Back to cited text no. 11
    
12.
Budd JC, Gekelman D, White JM. Temperature rise of the post and on the root surface during ultrasonic post removal. Int Endod J 2005;38:705-11.  Back to cited text no. 12
    
13.
Lee FS, Cura JV, BeGole E. A comparison of root surface temperatures using different obturation heat sources. J Endod 1998;24:617-20.  Back to cited text no. 13
    
14.
Hatton JF, Pashley DH, Shunk J, Stewart GP. In vitro and in vivo measurement of remaining dentin thickness. J Endod 1994;20:580-4.  Back to cited text no. 14
    
15.
Fujita R, Komada W, Nozaki K, Miura H. Measurement of the remaining dentin thickness using optical coherence tomography for crown preparation. Dent Mater J 2014;33:355-62.  Back to cited text no. 15
    
16.
Michetti J, Maret D, Mallet JP, Diemer F. Validation of cone beam computed tomography as a tool to explore root canal anatomy. J Endod 2010;36:1187-90.  Back to cited text no. 16
    
17.
Hartmann MS, Barletta FB, Camargo Fontanella VR, Vanni JR. Canal transportation after root canal instrumentation: A comparative study with computed tomography. J Endod 2007;33:962-5.  Back to cited text no. 17
    
18.
Jurcak JJ, Weller RN, Kulild JC, Donley DL. In vitro intracanal temperatures produced during warm lateral condensation of gutta-percha. J Endod 1992;18:1-3.  Back to cited text no. 18
    
19.
McCullagh JJ, Setchell DJ, Gulabivala K, Hussey DL, Biagioni P, Lamey PJ et al. A comparison of thermocouple and infrared thermographic analysis of temperature rise on the root surface during the continuous wave of condensation technique. Int Endod J 2000;33:326-32.  Back to cited text no. 19
    
20.
McCullagh JJ, Biagioni PA, Lamey PJ, Hussey DL. Thermographic assessment of root canal obturation using thermomechanical compaction. Int Endod J 1997;30:191-5.  Back to cited text no. 20
    
21.
Schilder H. Filling root canals in three dimensions. 1967. J Endod 2006;32:281-90.  Back to cited text no. 21
    

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Correspondence Address:
Dr. Sundaresan Balagopal
Tagore Dental College and Hospital, Melakottaiyur, Chennai - 600 127, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_508_19

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