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ORIGINAL ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 1  |  Page : 82-89

Intracanal cryotherapy with two different temperature ranges in reducing postendodontic pain: A double-blind randomized clinical trial


Faculty of Dentistry, SEGi University, Petaling Jaya, Selangor, Malaysia

Date of Submission11-Jul-2020
Date of Decision23-Jun-2021
Date of Acceptance28-Jun-2021
Date of Web Publication8-Jan-2022

Correspondence Address:
J Sylvia Western
Faculty of Dentistry, SEGi University, No. 9, Jalan Teknologi, PJU5, Kota Damansara 47810, Petaling Jaya, Selangor
Malaysia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_122_21

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  Abstract 


Introduction: The use of intracanal cryotherapy in the reduction of postendodontic pain (PEP) has been investigated in several recent scientific publications. This study aims to compare the effect of intracanal cryotherapy at three different temperature ranges (room temperature, 2°C–4°C and 13°C–15°C) on PEP.
Materials and Methods: A parallel, double-blind randomized clinical trial was conducted at SEGi University, Malaysia. This trial included 51 participants who were diagnosed with symptomatic irreversible pulpitis and symptomatic apical periodontitis in single-rooted teeth. The root canal therapy was completed in single visit for all the patients. Prior to the obturation step, they were randomly allocated into three groups of 17 participants each (Group 1: room temperature [control], Group 2: 2°C–4°C, and Group 3: 13°C–15°C). The intracanal cryotherapy was performed over a period of 5 min. The PEP scores were measured using Wong Baker Faces Pain Rating Scale and recorded at different time intervals (6, 24, 48, and 72 h), and the data were statistically analyzed.
Results: Kruskal–Wallis test showed statistically significant difference in mean pain ranks between at least two out of three groups studied at 24 and 48 h (P ≤ 0.05). At 24 and 48 h, the pairwise post hoc Dunn test with Bonferroni adjustments showed statistically significant difference in pain scores within the Groups 1 versus 3 (room temperature vs. 13°C–15°C) and Groups 1 versus 2 (room temperature vs. 2°C–4°C) (P ≤ 0.05), while within the Groups 2 versus 3 (2°C–4°C vs. 13°C–15°C), there was no statistically significant difference.
Conclusion: Intracanal cryotherapy with 13°C–15°C saline is as effective as 2°C–4°C saline in reducing PEP and can be easily incorporated as one of the steps of root canal therapy.

Keywords: Cryotherapy, pain measurement, root canal irrigants, saline solution, temperature


How to cite this article:
Western J S, Zahir AS, Haja Mohainuteen AI, Ping BY, Hui CS, Ru CE, Dicksit DD. Intracanal cryotherapy with two different temperature ranges in reducing postendodontic pain: A double-blind randomized clinical trial. Saudi Endod J 2022;12:82-9

How to cite this URL:
Western J S, Zahir AS, Haja Mohainuteen AI, Ping BY, Hui CS, Ru CE, Dicksit DD. Intracanal cryotherapy with two different temperature ranges in reducing postendodontic pain: A double-blind randomized clinical trial. Saudi Endod J [serial online] 2022 [cited 2022 Jan 25];12:82-9. Available from: https://www.saudiendodj.com/text.asp?2022/12/1/82/335232




  Introduction Top


The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damage”[1] and is one of the major reasons for patients visit to dental clinics. Among various commonly performed dental procedures, root canal therapy is mostly perceived to be associated with pain[2] and might affect the doctor–patient relationship adversely.[3] The reported incidence of postendodontic pain (PEP) varies and ranges from 3% to 58%.[4]

PEP is usually caused by chemical, mechanical, or microbial injuries to the periapical tissue that result in acute inflammation. The causative factors mainly include microbial contamination due to missed canals, lack of apical patency, insufficient instrumentation, overinstrumentation, apical extrusion of debris, root canal irrigants or root canal filling materials, and hyperocclusion of access cavity restorations.[5] PEP may be minimized by preventing these procedural errors, pharmacological management of pain and inflammation, using crown-down preparation during cleaning and shaping, occlusal reduction, and more recently intracanal cryotherapy.[6]

Cryotherapy, which is the use of extreme cold temperatures for therapeutic purposes, has its historical roots dating 3000 BC, when Egyptians used cold compresses to treat inflammation over infected wounds.[7] Modern-day medicine uses cryotherapy in surgical oncology, dermatology, neurology, pain management, and in some psychiatric illnesses. In endodontics, several researchers have evaluated the efficacy of intracanal cryotherapy, that is the use of cold saline as a final rinse on PEP. [5],[8],[9],[10],[11],[12],[13] A systematic review and meta-analysis showed a moderate-quality evidence on the efficacy of intracanal cryotherapy on PEP at 6 and 24 h.[14] The most common dosage of intracanal cryotherapy used so far was 20 mL cold saline at 2.5°C for 5 min.[14] Further, an in vitro study showed that using 2°C–4°C normal saline as a final irrigant may reduce the vertical fracture resistance of the tooth.[6] In view of this, there is a need to determine whether intracanal cryotherapy with an optimal cold temperature (13°C–15°C) can reduce PEP as effectively as 2°C–4°C.

The purpose of this study is to comparatively evaluate the effect of intracanal cryotherapy performed using normal saline at three different temperature ranges (room temperature, 2°C–4°C, and 13°C–15°C) on PEP measured using Wong Baker Faces Pain Rating Scale (WBS)[15] [Figure 1] in patients with symptomatic apical periodontitis associated with symptomatic irreversible pulpitis.
Figure 1: Wong Baker Faces Pain Rating Scale

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  Materials and Methods Top


Study design

A prospective, parallel, randomized controlled clinical trial was conducted in SEGi Oral Health Centre, SEGi University, Malaysia. This equivalence trial was conducted after obtaining ethical approval from the University Institutional Ethics Board (Reg No: SEGiC/SR/FOD/02/2019–2020). Before starting the treatment procedures, all participants included in the study were informed about the nature and objectives of the study. Written informed consent was obtained from all the participants.

Sample size calculation

For a large effect size of 1.02 calculated from difference of means taken from a previously conducted clinical trial by Vera et al.[8] with an alpha error of 0.05 and power of 0.8, the sample size required was estimated as 13 participants per group. Further estimates, taking into consideration possible 15% dropouts, suggested a total sample size of 51 with 17 participants per group for 3 groups.

Patient selection and allocation

From a total of 124 patients who presented for emergency pain management to SEGi oral health center, 51 participants were included in the study based on the following inclusion and exclusion criteria.

Inclusion criteria

  • Patients diagnosed with symptomatic apical periodontitis associated with symptomatic irreversible pulpitis
  • Patients requiring emergency pain management with the registered pain scores of ≥ 8 in Wong Baker Faces Pain Rating Scale
  • Patients within the age group of 20–50 years.


Exclusion criteria

  • Pregnant patients
  • Those under medication for chronic pain
  • Immunocompromised patients
  • Patients presenting with difficult root canal anatomy evident in radiographs (curved canals, root resorptions, open apices, and calcified canals)
  • Subjected to procedural mishap or complication during treatment.


Five general dental practitioners with equal clinical experience performed the 51 root canal treatments in a single sitting over a time span of 1 year.

Root canal treatment procedure

Emergency pain management was performed under local anesthesia using 2% lignocaine with 1:100,000 adrenaline. After rubber dam isolation, the access cavity was prepared using sterile endodontic access cavity preparation burs (Dentsply Sirona, Ballaigues, Switzerland). The cervical third of the root canal was flared with a Gates-Glidden Drill (Dentsply Maillefer, Ballaigues, Switzerland). After removal of the irreversibly inflamed pulp, working length was determined using the electronic apex locator (Propex Pixi, Dentsply Sirona, Ballaigues, Switzerland) and was confirmed radiographically. A glide path was established using #08 or #10 K-files (Dentsply Sirona, Ballaigues, Switzerland). Canals were then cleaned and shaped using hand instrumentation with a step-back technique using K files (Dentsply Sirona, Ballaigues, Switzerland) under copious irrigation using 5.25% sodium hypochlorite, 2% chlorhexidine, and 17% ethylenediaminetetraacetic acid (EDTA). The master cone fit was checked clinically and radiographically. Final rinse using 5 ml of 5.25% sodium hypochlorite and 5 ml of 17% EDTA was performed for all patients.

Random allocation and blinding

At this stage, patients were randomly allotted by a single researcher into one of the three groups with each group consisting of 17 participants (allocation ratio 1:1): Group 1: root canal irrigation done with normal saline at room temperature (control group), Group 2: intracanal cryotherapy application with 2°C–4°C normal saline, and Group 3: intracanal cryotherapy application with 13°C–15°C normal saline. Randomization is done after the cleaning and shaping stage rather than at the beginning of the trial to minimize performance bias. Random allocation within the 3 groups was done using computer-generated random numbers with Research Randomizer software.[16] The randomization sequence was concealed using sequentially numbered opaque sealed envelopes to prevent selection bias. A single researcher mentioned the grouping allocation for the recruited 51 participants within these sequentially numbered opaque envelopes. Upon entry of patient details over the envelope, the envelope was opened by another researcher to disclose the group to which the patient was allocated. The group to which the patient got allocated was concealed to the patient being treated and the third researcher who recorded the PEP scores and collected data at 6 h, 24 h, 48 h, and 72 h using WBS postoperatively, and therefore, this is a double-blinded study. Blinding could not be done for the operator as the temperature of the syringes whether room temperature or cold was obvious while handling the syringes and could not be concealed. In this study, 20 ml of saline was used to perform intracanal cryotherapy over a period of 5 min following a framework proposed and used in previous research.[5],[17] As per the allocation into groups, 20 ml of normal saline at three different temperature ranges (Group 1: room temperature, Group 2: 2°C–4°C, and Group 3: 13°C–15°C) was delivered using a negative apical pressure irrigation device, EndoVac system (KaVo Kerr, Orange, California) which was inserted at 1 mm short of the working length.

Regulation of temperature of saline for the intracanal cryotherapy groups

The required temperature of saline for intracanal cryotherapy (2°C–4°C and 13°C–15°C) was attained by storing the 20 ml irrigation syringes filled with saline in the refrigerator. Before irrigation, the temperature of the saline solution within the syringe was measured using a digital thermometer with an external probe with a temperature accuracy of ±1°C and an LCD display. In case the desired lower limit of the temperature ranges (2°C for Group 2 and 13°C for Group 3) was not reached, the syringes were kept on a bowl of ice to regulate the temperature. Irrigation was only carried out once the lower limit of the desired temperature ranges (2°C–4°C and 13°C–15°C) was reached. This was to ensure that during the handling of the syringes for 5 min during irrigation, the temperature of the saline within the syringes remained within the desired temperature range (Group 2 - 2°C–4°C and Group 3 - 13°C–15°C). For all the 51 patients, this regulation of temperature was done by a single researcher and syringes at the desired temperature as per allocation were given to the operator for root canal irrigation.

Completion of root canal procedure

Following this irrigation regimen, paper points (Diadent GP Points, Diadent Group International Inc., Korea) were used to dry the canals. Obturation was completed with gutta-percha cones (Diadent GP Points, Diadent Group International Inc., Korea) and an MTA-based bioceramic root canal sealer (MTA Fillapex, MTA Angelus, Brazil) using lateral compaction technique. Obturation was checked with radiograph and the pulp chamber was filled with glass ionomer cement (GC FUJI IX GP, GC Corporation, Tokyo, Japan) followed by composite restoration (Tetric N-Ceram Bulk Fill, Ivoclar-Vivadent, Schaan, Liechtenstein).

Evaluation of postendodontic pain

All patients were given instructions on how to use the WBS scale and to fill up a Google Docs questionnaire sent through WhatsApp communication. They were instructed to mark their perceived level of discomfort digitally on the Wong Baker Faces Pain Rating Scale reporting the corresponding numeric value on the WBS (0/2/4/6/8/10) according to the pain levels felt at each period of observation in the sent questionnaire. The link to the online form and reminder to fill the form was sent through WhatsApp communication at 6 h, 24 h, 48 h, and 72 h after obturation and was recorded and tabulated by a single researcher who was blinded to allocation of patient groups. There were no dropouts at this stage of the trial, and there was 100% response rate from the participants. During the trial, no changes were made to the patient selection criteria, methods or outcomes measured. The data were then statistically analyzed using Kruskal–Wallis test and post hoc Dunn's pairwise comparison with Bonferroni adjustments with IBM SPSS Statistics for Windows, version 22 (IBM Corp., Armonk, NY, USA). P ≤ 0.05 was considered statistically significant. The confidence interval was set at 95%.


  Results Top


The baseline characteristics of the included participants were recorded and tabulated [Table 1]. A summary of the study is shown in the CONSORT flow diagram [Figure 2]. Kruskal–Wallis test showed that there was statistically significant difference in mean pain rank between at least two out of three groups studied at 24 h and 48 h follow-up period [Table 2]. That is, at 24 h, there was a statistically significant difference in mean pain rank between at least two out three groups studied, χ2 (2) =16.35, P = 0.0001, with a mean rank of 35.68 for Group 1, 23.06 for Group 2, and 19.26 for Group 3. Furthermore, there was a statistically significant difference in mean pain rank between at least two of the three different groups studied at 48 h, χ2 (2) =14.499, P = 0.001, with a mean rank of 34.50 for Group 1, 22.50 for Group 2, and 21.00 for Group 3. However, there was no statistically significant difference in mean pain rank between the three groups at 6 h and 72 h follow-up period.
Figure 2: CONSORT flow diagram of the randomized controlled trial

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Table 1: Baseline characteristics of the included participants

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Table 2: Kruskal–Wallis test results showing difference in mean rank of postendodontic pain between the three groups studied at different follow-up periods

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At 24 and 48 h, the pairwise post hoc Dunn test with Bonferroni adjustments [Table 3] showed significant difference in pain score between the Groups 2 and 1 and Groups 3 and 1 at P ≤ 0.05. There was no statistically significant difference between the Groups 2 and 3. This means that at the 24 h follow-up period, PEP in the Group 2 (mean pain score = 0.588) was statistically significantly lower than the Group 1 (mean pain score = 2.118) (P = 0.009). Furthermore, at the same 24 h follow-up period, PEP in Group 3 (mean pain score = 0.235) was statistically significantly lower than Group 1 (mean pain score = 2.118) at P = 0.001. At 48 h follow-up period, PEP in Group 2 (mean pain score = 0.235) was statistically significantly lower than Group 1 (mean pain score = 1.294) at P = 0.018. Furthermore, at the same 48 h follow-up period, PEP in Group 3 (mean pain score = 0.118) was statistically significantly lower that Group 1 (mean pain score = 1.294) at P = 0.008. However, there was no statistically significant difference in PEP between the two independent groups - Group 2 and Group 3 at all time periods of observation. A bar chart showing mean pain scores of the three groups studied at 6, 24, 48, and 72 h is depicted in [Figure 3]. There were no unintended events reported in all the three groups studied.
Figure 3: A bar chart showing mean pain scores of the three groups studied at 6, 24, 48 and 72 h

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Table 3: Results of pairwise post hoc Dunn test with Bonferroni adjustments at 24 h and 48 h follow-up period

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  Discussion Top


From the findings in the control group (room temperature saline), the pattern of PEP observed in this study is that the pain is more pronounced on the 1st and 2nd day (24 and 48 h) after obturation. While, at 6 h and 72 h follow-up period, it tended to be comparatively lower. Similar trend is reported in a systematic review on PEP where the trend of PEP was highest at the 24 and 48 h and continues to reduce thereafter.[18] Mechanism of PEP is that inflammatory mediators are released into the surrounding apical areas of the tooth in response to local irritation following root canal treatment procedures.[19] This stimulates pain conducting nerve fibers, causes vasodilation and oedema resulting in increased interstitial tissue pressure, and thereby increases pain perception.[19] Intracanal cryotherapy reverses this phenomenon by reducing the root surface temperature, which causes a decrease in nerve conduction and a local anti-inflammatory effect by vasoconstriction and deceleration of cellular mechanism.[10]

The results of the present study showed that at 24 h and 48 h follow-up period, intracanal cryotherapy reduced PEP more effectively compared to room temperature saline and is consistent with the previous studies.[5],[8],[9],[10],[12],[13] The results of the two studies by Al-Nahlawi et al. and Vera et al. showed that the mean pain scores of the intracanal cryotherapy group (2°C–4°C) were statistically significantly lower than the control group at 6 h follow-up period as well.[5],[8] This is in contrary to the present study where there was no statistically significant difference in PEP between all three groups studied at 6 h follow-up period. Also, studies by Vera et al., Gundogdu and Arslan, and Emad et al. showed statistically significant reduction in mean pain scores in the intracanal cryotherapy group compared to the control group at 72 h follow-up period.[8],[10],[13] Again, the present study showed no statistically significant difference in PEP within the three groups at 72 h follow-up period. The contrary findings in the present study at 6 and 72 h could be attributed to the fact that PEP in general occurs maximum at 24–48 h follow-up periods,[18] and therefore not profound at the early and later follow-up periods (6 h and 72 h). Consequently, the effect of intracanal cryotherapy was not apparent at 6 h and 72 h in the present study.

The results of the study by Alharti et al.,[11] which found no statistically significant difference in pain perception between intracanal cryotherapy group and room temperature group, were contrary to our findings. This could be attributed to the use of conventional syringes for intracanal cryotherapy in that study, wherein possible vapor lock effect could have prevented the cold irrigant from reaching the apical third of the canal.[9] Therefore, in the present study, negative apical pressure irrigation technique was used to counteract the vapor lock effect during root canal irrigation. However, the study by Keskin et al. demonstrated statistically significant reduction in PEP in the cryotherapy group compared with the control group similar to the present study, despite the use of conventional side vented needles for root canal irrigation. In the Keskin et al. study, the vapor lock effect could have been evaded as the needles were positioned 2 mm short of working length to facilitate movement of cold saline to the apical portion of the root canal.[9]

This study included patients diagnosed with symptomatic irreversible pulpitis and symptomatic apical periodontitis with pain scores ≥8, as these conditions are independent predictors of severe PEP.[20] We had included only those patients in good general health as use of intracanal cryotherapy is controversial in patients with some systemic diseases like Raynaud's disease and also in some cardiac conditions, wherein vasoconstriction might cause an increase in blood pressure.[8] Patients younger than 20 years of age were excluded due to the higher prevalence of anxiety levels in that age group.[21] Also, those older than 50 years were excluded as pain perception is generally reduced in that age group.[22] As procedural errors are identified as one of the prime confounding factors that may have an external effect on PEP, this study has excluded all cases where endodontic mishaps occurred during the root canal treatment procedure similar to the study by Alharthi et al.[11] Other possible confounders like age, gender, tooth type, occlusal contact, and preoperative pain scores were all identified and ensured equal distribution across the studied groups by randomization.

Surface cooling of oral mucosa to 12.9°C causes vasoconstriction leading to pain alleviation.[23] Based on this, an optimal temperature range of 13°C–15°C was chosen and compared with the commonly used temperature range of 2°C–4°C[14] for intracanal cryotherapy in this study. The findings of the present study confirmed that intracanal cryotherapy with 13°C–15°C normal saline is as effective as 2°C–4°C in reducing PEP. It supports the findings of Vieyra et al.'s study, which concluded that intracanal cryotherapy with 4°C could be as effective as 2°C in reducing PEP.[13] In this study, at 24 h and 48 h follow-up period, there was no statistically significant difference in PEP recorded between patients who received intracanal cryotherapy with 2°C–4°C and 13°C–15°C saline. The present study adds on to the existing research[5],[8],[9],[10],[12],[13] that intracanal cryotherapy with an optimum cold temperature of 13°C–15°C could be as effective as 2°C–4°C in reducing PEP.

Limitations of the present study are as follows:

  1. The scale used to measure pain was inherently subjective, although it was used as it is considered reliable and valid[10]
  2. In other situations where obturation techniques use heat softening of gutta-percha, the effect of intracanal cryotherapy may be negated, compromising the external validity of the present study.


Implications for further research:

  1. Although intracanal cryotherapy provides short-term benefits in pain reduction, its long-term effects on the outcome of root canal therapy are yet to be investigated[10]
  2. Its effects on the setting time and sealing ability of root canal sealers used are unclear
  3. Its role on apical microleakage and microorganisms is yet to investigated.



  Conclusion Top


Consistent with the existing literature, this study supports the use of intracanal cryotherapy in reducing PEP. It concludes that intracanal cryotherapy with the use of 13°C–15°C normal saline is equally effective as 2°C–4°C in reducing PEP in patients who have undergone root canal treatment. Intracanal cryotherapy is a short extra step that can be easily added to root canal therapy procedures and is proved to be effective in reducing PEP.

Acknowledgment

We would like to thank Prof. Datuk Dr. Khairiyah Abd Muttalib and Assoc Prof. Dr. Priyadarshini from the Faculty of Dentistry, SEGi University, for their technical support and guidance in this research.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

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