|Year : 2015 | Volume
| Issue : 2 | Page : 66-71
Effect of Temperature Rise on Periodontal Tissue During Endodontic Treatment: An In Vitro Study
Anilkumar Chauhan1, Vimala Nilker2, Lalitagauri P Mandke2
1 Department of Conservative Dentistry and Endodontics, Saraswati Dhanwantari Dental College and Hospital, Parbhani, India
2 Department of Conservative Dentistry and Endodontics, D.Y. Patil University, School of Dentistry, Navi Mumbai, Maharashtra, India
|Date of Web Publication||17-Dec-2015|
Department of Conservative Dentistry and Endodontics, D.Y. Patil University, School of Dentistry, Navi Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Aim: The aim of the study is to investigate the influence of temperature rise on a single rooted tooth during biomechanical tooth preparation, obturation and root canal preparation for radicular post. Materials and Methods: Forty-five extracted human mandibular premolars with a single canal, extracted for orthodontic reasons, were stored in saline. Access cavity was prepared with endo access bur and pulp extirpations were done. The teeth were randomly divided into five groups of 9 teeth each. In group 1 and group 2 cleaning and shaping of the root canal was done using protaper file system and Hyflex system respectively. In group 3 and 4 obturation was done using Step-One obturation system and Calamus Dual respectively. In group 5 post space preparation was done using peeso reamers. Each sample tooth was embedded in alginate contained in Eppendorf tube. Tooth was placed in water bath with the two thermocouples attached at the apical and middle third which was in turn attached to thermometer. The rise in temperature was noted at the desired level and statistical analysis was done. Results and Conclusion: The mean temperature rise at the middle third for group 1, 2, 3, 4, 5 was 0.4°C, 0.15°C, 1.80°C,10.33°C, 9.46°C respectively. The mean temperature rise at the apical third for group 1, 2, 3, 4, 5 was 0.08°C, 0.08°C, 1.20°C, 6.91°C, 6.4°C respectively. ANOVA showed significant difference in mean temperatures of different methods. post hoc test comparison using Duncan's test revealed maximum rise in temperature during obturation using Calamus dual (Group 4).
Keywords: Canal preparation, obturation, periodontal damage, temperature rise
|How to cite this article:|
Chauhan A, Nilker V, Mandke LP. Effect of Temperature Rise on Periodontal Tissue During Endodontic Treatment: An In Vitro Study. Indian J Oral Health Res 2015;1:66-71
|How to cite this URL:|
Chauhan A, Nilker V, Mandke LP. Effect of Temperature Rise on Periodontal Tissue During Endodontic Treatment: An In Vitro Study. Indian J Oral Health Res [serial online] 2015 [cited 2019 Nov 12];1:66-71. Available from: http://www.ijohr.org/text.asp?2015/1/2/66/172038
| Introduction|| |
The aim of endodontic therapy of the necrotic or irreversibly diseased pulp is to allow the preservation of the tooth as a healthy functional unit. During endodontic treatment various manipulation and restoration of the teeth can be associated with increase in temperature of dental structure and periodontal tissue. During cleaning and shaping of the root canal system using rotary instrument, heat is generated due to the frictional force between the files and the remaining dentine structure. This temperature is transferred to the surrounding dental tissues, including the external surface of the root. The three-dimensional obturation of the root canal system can be achieved by various thermoplastification techniques. During the thermoplastic method of condensation, the plastification of gutta-percha leads to temperature rise on the external and internal root surface. Temperature elevations of 10°C above body temperature, of duration >1 min, may be sufficient to cause bone tissue injury. , Rise in temperature above critical 45°C causes surface resorption of the cementum and bone ankylosis. The preparation of the root canal to accept a postinvolves cutting the dentinal walls precisely so that a matched post may be fitted. Dentine has a low thermal conductivity  but the heat produced by the preparation procedures may pass on to the root surface, which is a potential insult to the periodontal ligament (PDL) and adjacent bone.
The aim of this study is to measure the temperature changes along the length of the root surface when various manipulations are carried out during various endodontic procedures with the aid of a thermocouple.
| Materials and methods|| |
Forty-five extracted human mandibular premolars with a single canal, extracted for orthodontic reasons, were stored in saline. The roots were stripped of soft tissue and calculus using hand instruments. All specimens were inspected to disclose any defects or root fractures and confirm the complete formation of apices. Access cavity was prepared with endo access bur (Dentsply Maillefer) and pulp extirpations were done, #10 k file was introduced into the canal until it just emerged from the apical foramen. The working length was established by subtracting 0.5 mm from this length. The canal was enlarged to the apical tip diameter of ISO size 40. 
The teeth were randomly divided into five groups of nine teeth each. In group 1 and group 2 cleaning and shaping of the root canal was done using ProTaper file system (Dentsply Maillefer) and Hyflex system (Coltene Whaledent, USA.), respectively, using torque control endo-motor (X-Smart, Dentsply Maillefer). The sequence for ProTaper file system (Dentsply Maillefer) was S1, S2 for shaping of the canal. Following the use of each ProTaper file, irrigation, recapitulation with a 10 file, then re-irrigation was carried out. Then, the finishing of the canal was done using F1, F2, F3, and F4 files. Following the use of the finishing files, the canal was flooded with irrigant, recapitulated and confirmed patency, then re-irrigated to liberate debris from the canal. The sequence used for Hyflex file system (Coltene Whaledent, USA.) was 0.08/25, 0.06/20, 0.04/30, and 0.04/40. Following each Hyflex file, irrigation, recapitulation with a 10 file, then re-irrigation was carried out. The canals were irrigated with 2 ml of 5% sodium hypochlorite solution after each instrument. Finally, the canals were flushed with 2 ml of 17% ethylenediaminetetraacetic acid. For the canals in group 3 and group 4 cleaning and shaping was done using ProTaper file system. The canal was enlarged to the apical tip diameter of ISO size 40.
The canals in group 3 were obturated using One-Step Obturation system. The One-Step system consists of a flexible central plastic carrier coated with a layer of alpha-phase gutta-percha. In the coronal part of the root canal, the softened gutta-percha was condensed with a plugger around the carrier. When the obturator was placed in the canal till the working length, temperature was noted at the middle and apical third. The canals in group 4 were obturated by continuous wave of condensation (WOC) techniques  using the Calamus Dual 3D Obturation System The Calamus Pack handpiece is the heat source that, in conjunction with an Electric Heat Plugger (EHP), is utilized to thermosoften, remove, and condense gutta-percha during the down packing phase of obturation. The EHP of ISO size 40 was selected for the study. The 23-guage single use cartridges were used. The Calamus EHP was activated and utilized to sear off the master cone at the cementoenamel junction. The large size plugger was used with short, firm vertical strokes to scrape warm gutta-percha off the canal walls and flatten the material coronally. The working end of the plugger was used to vertically press on this flattened platform of warm gutta-percha for 5 s. This action serves to automatically fill the root canal system, laterally and vertically, over a range of few millimeters and is termed a WOC. Depending on the length of the canal, only 2 or 3, heating and removal cycles were required until the preselected EHP was placed within 5 mm of the canal terminus. The temperature was measured at this apical third. The Calamus Flow handpiece was activated and a short 2 to 3 mm segment of warm gutta-percha was dispensed into the most apical region of the empty canal. The Calamus Flow handpiece was held lightly so it will "back-out" of the canal when injecting thermosoftened gutta-percha into the canal. The temperature was measured at this middle third.
In the canals of group 5, the postspace preparation was done using peeso-reamers of size (1.1 mm) (Mani, INC, Japan) at rotational speed of 8000 rpm [Figure 1]. The apical 4-5 mm of root filling should not be disturbed to avoid subsequent leakage and failure of the endodontic therapy.  The temperature was measured at the apical and the middle third during the procedure [Table 1] and [Table 2].
Experimental setup for temperature measurement
During the procedure reading with the highest temperature was noted. Tooth was embedded in alginate contained in Eppendorf tube. Alginate was used as a substitute for the PDL because its water content is very similar to the water content of the human body. Two small windows were created into the Eppendorf tube and through alginate to allow for the thermo couple temperature probe. One window was created at the apical third and the other at the middle third. The study was carried out in water bath at constant temperature of 37°C. Tooth embedded in alginate contained in Eppendorf tube was placed in water bath and the two thermocouples were attached at the apical and middle third, which was in turn attached to the thermometer and the study was conducted [Figure 2]. Thermocouple works on the basis of thermoelectric effect that results in an electric current when two dissimilar metal wires are joined together and subjected to temperature change. 
| Results|| |
The temperature was measured at the apical and middle third of the root during the procedure and the readings noted [Table 1] and [Table 2].
The ANOVA test and post hoc test (Duncan) test was done.
| Discussion|| |
Endodontic treatment generates heat within the dentine of the tooth that might be transmitted to the attachment apparatus. However, the poor thermal conductivity of dentine (1.36 × 10−3 cal / s/cm 2 /C/cm) will help dissipate the heat and prevent its transfer through the attachment apparatus.  The critical temperature for bone injury is 56°C; at which bone alkaline phosphatase is rapidly inactivated in vitro.  Eriksson and Albrektsson  conducted a sophisticated vital microscopic study of temperature threshold levels for heat-induced bone tissue injury, and concluded that the critical temperature for bone injury may be as low as 47°C. This temperature is 9°C lower than that associated with denaturation of alkaline phosphatase and only 10°C above human body temperature. The ProTaper files were specifically designed to provide superior flexibility, unmatched efficiency and greater safety. The unique feature of ProTaper instruments relates to their convex triangular cross-section. It reduces the contact area between the blade of the file and dentin and serves to enhance the cutting action and decrease torsional load. Peters et al.  in his study have concluded that the fatigue resistance of Hyflex CM is much higher, and canal preparation ability appears to result in less lower working torque, compared to other rotary instruments tested under similar conditions. The mean temperature rise in the middle third was 37.3°C with ProTaper system and 37.1°C with Hyflex CM system and in the apical third was 37.08°C with both the systems. At P < 0.025; for ProTaper file system (Dentsply Maillefer) the mean temperature rise is significant in the middle third and at P > 0.025 the mean temperature at the apical third is almost equal to the 37°C. At P < 0.025 for Hyflex CM file system (Coltene Whaledent, USA) for the middle third and the apical third the mean temperature rise is significantly greater than the base temperature of 37°C in the middle and apical third of the root canal. A temperature rise of 10°C above normal body temperature (37°C) is regarded as a critical level at which periodontal tissues could be adversely affected. , Though the temperature rise is shown to be statistically significant in the apical and middle third with the use of Hyflex CM rotary system, and the middle third of root canal with the use of ProTaper system at their respective P values, when correlated with the clinical situation, this temperature rise is significantly less than the critical temperature of 10°C, indicating that the use of ProTaper file and Hyflex file for cleaning and shaping does not damage the surrounding tissues. This result correlates with the study of Dimitrov et al.  who have found out that the root canal preparation with the endodontic motor system (Flex Master) did not cause overheating of the periradicular tissues [Table 3],[Table 4],[Table 5],[Table 6],[Table 7] and [Table 8].
Various advances in obturation procedures have led to the development of systems that delivers thermoplasticized gutta-percha material to the prepared canal space. The heat increases the flow of the material and produces a more homogeneous well-adapted root canal filing and dimensionally stable mass of gutta-percha.  Saunders  in his in vivo study during obturation using thermally softened gutta-percha found surface resorption of cementum in 27.7% of cases, with evidence of bone ankylosis in 22.2% of the cases after 40 days. Molyvdas et al.  in his study found the destruction of the apical PDL when the tooth was obturated with the delivery system that is, Obtura device was set at 170°C. Two different systems were used during obturation with thermoplasticized gutta-percha.
The potential for tissue damage due to excessive heat within the root canal system necessitates the evaluation of technique. The range of temperature used to soften the gutta-percha was 60-200°C. One-Step Obturation system used a carrier based thermoplasticized gutta-percha heated to a temperature of 60°C. In this study; change in temperature was recorded relative to ambient root temperature. It has been recorded that a rise of 10°C can cause damage to the surrounding tissue.  One-Step system (CMS Dental, Denmark) and Calamus Dual (Dentsply Maillefer) are the two obturation techniques used in this study. The temperature rise was measured at the apical third and the middle third during the obturation technique. The mean temperature rise for One-Step system (CMS Dental, Denmark) at the middle third and apical third was 1.80°C and 1.20°C, respectively. At P < 0.025 the mean temperature rise was significantly greater than the base temperature in the middle third and the apical third of the root canal. However, at no time, did the temperature change on the external root surface exceed 10°C. Though the temperature rise is shown to be statistically significant in the middle and apical third with the use of step-one obturation system but when correlated with the clinical situation, it does not have any damaging effect on the tooth structure. Similar the mean temperature rise for Calamus Dual system (Dentsply Maillefer) was measured. At the middle third and the apical third, the mean temperature rise was 10.33°C and 6.91°C, respectively. Hardie  in the study has recorded a temperature rise up to 27°C on the central region of the root surface during thermo-mechanical compaction technique of root canal obturation. Saunders  has found the mean temperature rise of 18.3°C at the midpoint of the root canal. Barkhordar et al.  in their study have found that when sealer was not used for obturation the maximum temperature rise seen form the base temperature of 37°C was during warm gutta-percha technique 44.02°C followed by Obtura 41.72°C and Ultrafil obturation technique 40.02°C. Weller and Koch  has found the mean temperature rise recorded on the root surface ranged from 4.22°C to 8.90°C when the canals were obturated using Obtura II heated gutta-percha system. Mc Cullagh et al.  in their study have found the average temperature rise by the thermal imaging system was 28.4°C with the range between 15.5°C and 40.0°C at the apical end and by the thermocouple was 13.9°C with the range of 8.7 to 21.0°C. Dentine is a thermal insulator, and thicker the dentine, less heat is transferred to the attachment apparatus.  The teeth used in this study have relatively thick walls (premolar). In a study by Lee et al.  it was found that temperature rises were lower in premolars (thicker) than in incisors (thinner). In addition, gutta-percha is a poor thermal conductor of heat, and does not allow heat transmission. It limits heat transmission through dentine by absorbing the heat, resulting in lower temperature on the root surface. In this study, the sealer was used during the obturation technique to simulate the clinical situation. The sealer acts as an insulator by lowering the surface temperature ~1°C to ~2°C. However, Hardie  has reported that sealer had no effect on surface temperature during thermo-mechanical compaction. The relatively low-temperature rise on the root surface may be even lesser in vivo; because of the circulation present in the periodontal membrane and the wetness of dentine; brought by the presence of fluids in the dentinal tubules.  At P < 0.05 the mean temperature rise was significantly greater than the base temperature in the middle third and the apical third of the root canal when the root canal was obturated using Calamus Dual system (Dentsply Maillefer). Though the temperature rise is shown to be statistically significant in the apical third but when correlated with the clinical situation, it is less than the critical temperature, indicating that it does not have any damaging effect on the tooth structure. The mean temperature rise at the middle third was 10.33°C, which is above the critical temperature so the operator should be cautious while using this system. In a clinical situation, the radicular supporting tissues also play a supporting role in dissipating heat. Tissue damage is related not only to the original temperature rise but also to the time period (>1 min) for which the tissue is subjected to the increased temperature (Moritz and Henriques,  Eriksson and Albrektsson  ) [Table 3].[Table 4],[Table 5],[Table 6],[Table 7] and [Table 8].
In the group 5 postspace preparation was done using peeso reamer. The mean maximum temperature rise during postspace preparation at the middle end and the apical end was 9.46°C and 6.40°C respectively. Saunders and Saunders  in their has found maximum temperature rise using parapost during postspace preparation with a mean value of 18.80°C and a range of 10-31°C and the least temperature rise was seen while using GPX reamer. Weller et al.  in their study has found that during postspace preparation the overall mean temperature increased ranged from 0.66°C to 4.81°C and was greatest at 8000 r.p.m. At P < 0.05 the mean temperature rise was significantly greater than the base temperature in the middle third and the apical third of the root canal when postspace preparation was done using Peeso reamer (Dentsply Maillefer). Though the temperature rise is statistically significant in the apical and middle third of the root canal, when correlated with the clinical situation it does not produce any damage to the tooth and surrounding tissues. Furthermore, Lipski et al.  studied the influence of water cooling on the root surface temperature generated during postspace preparation and concluded that continuous water cooling significantly reduces the temperature increase generated by postspace preparation and is safe and shows low risk of PDL tissue damage. An ANOVA test between the groups showed that the P value for the ANOVA is less than that of 0.05, indicating that there is a significant difference between the mean temperatures of different methods used. To find out which of these methods shows significant difference; post hoc test comparison was done using Duncan's test. In comparison between all five groups, group 4 showed a significant rise in temperature in the middle third of the root. The temperature rise in the apical third was not significantly different among any of the five groups [Table 6] and [Table 8].
| Conclusion|| |
Within the limitations of this study, it was found that there was a rise in temperature during endodontic procedures. Thermoplasticized obturation techniques cause rise in root surface temperature; however, it does not affect the prognosis. Care should be taken while postspace preparation, preferably with the use of a water coolant.
| Acknowledgments|| |
We would like to thank the Department of Oral Pathology Dr. D.Y. Patil University, School of Dentistry, Navi Mumbai, Maharashtra, India for providing experimental set up in conduct of the study.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]