The effect of solution and gel forms of sodium hypochlorite on postoperative pain: a randomized clinical trial

Abstract Objectives The aim of this study is to evaluate the effect of using gel and solution forms of NaOCI during the chemomechanical preparation of the root canals on postoperative pain at different time intervals. Methodology 114 patients with mandibular molar teeth and symptomatic irreversible pulpitis were included in the study. All patients were divided into two groups based on the irrigant used during root canal preparation (n=57): Group 1, 5.25% NaOCI, Group 2, 5.25% NaOCI gel. All groups were filled with gutta-percha and AH Plus root canal sealer using single-cone technique. VAS scale (1-10) was used for postoperative pain assessment. After endodontic treatment, all patients were asked to record their postoperative pain levels at the 6th, 24th, 48th, 72nd hours, and 1 week later. The data were analyzed using Chi-Squared, Independent Samples T, Cochran Q and Friedman tests. Results Statistically significant difference was not found between the distributions of pain levels at different times according to the groups (p>0.050). A statistically significant difference was observed between the distributions of pain levels measured at different times in the solution group (p<0.001). A statistically significant difference was found between the distributions of pain levels measured at different times in the gel group (p<0.001). In both groups, highest postoperative pain levels occurred in the first 6 hours. Pain levels of the gel group as 38,5% mild, 17.3% moderate, 5.8% severe and pain levels of the solution group were obtained as 46.2% mild, 26.9% moderate, 9.6% severe at the 6th hour. Conclusions The use of the gel form of NaOCI during the chemomechanical preparation of the root canals showed similar postoperative pain when compared to the solution form.


Introduction
Postoperative pain is a widespread complication after root canal treatments, which is undesirable for patients and physicians. 1 The incidence of postoperative pain stated in cases is 39% after endodontic treatment and in the first 24 hours, this rate can even be up to 65% and above. 2  of the root canal. 5,6 Sodium hypochlorite (NaOCI) is the most widely used irrigation solution during root canal treatment. 3 In addition to its advantages such as antimicrobial activity and organic tissue solvency, however, it also has cytotoxic effects on periradicular tissues. When it is extruded from apical to periradicular tissues during root canal treatment, it damages endothelial cells and fibroblasts, facial nerve palsy, allergic reaction and necrosis may develop. 7 In a retrospective study conducted by members of the American Association of Endodontists, 42% of clinicians reported that using NaOCI causes postoperative pain or serious complications at least once a year. 8 That's why, researchers are in search of a more biocompatible irrigant.
It has been suggested currently that the use of the gel form of NaOCI is a potential option. 9,10 Studies have reported that the solution and gel forms of NaOCI have a similar effect on dentin. In the study of Zand,et al. 10 (2010) evaluating the smear layer removal activity of the solution and gel forms of NaOCI, and the study of Garcia, et al. 9 (2013)  www.randomizer.org). Each group was randomly and equally divided. The allocation ratio was 1:1. In the study, patients were not informed about the division and they were blinded. However, the clinicians could not be blinded due to the nature of the study.  for inferior alveolar nerve blockade. After rubber dam isolation, endodontic access cavity was prepared using high-speed burs (Dentsply Maillefer, Ballaigues, Switzerland). The working length (WL) was determined using apex locator (Propex Pixi, Dentsply Maillefer) and confirmed to be 0.5-1 mm shorter than the "radiographic apex" by periapical radiographs. The root canals were mechanically prepared using ProTaper Next (Dentsply, Maillefer, Ballaigues, Switzerland) up to X3. All ProTaper Next files were used with an endodontic engine (X-Smart, Dentsply Sirona) at the torque and speed values recommended by the manufacturer. After reaching the WL with size-15 K-type hand file, shaping was continued with brushing motion until the canal length was achieved with X1, X2 and X3 files, respectively. The files were withdrawn at the point where resistance was met before torsional overload occurred and the work continued after the apical opening was checked with size-10 K-type hand file. All patients were divided into two groups based on irrigant used during root canal preparation (n = 57): Group 1, 5.25% NaOCI solution (Imicrly, Konya, Turkey), Group 2, 5.25% Chloraxid gel.
Group 2 (NaOCI gel): Gel form of 5.25% NaOCI (Chloraxid gel, Cercamed, Stalowo Wolo, Poland) was used. After covering the root canal files with NaOCI gel, they were placed in the root canal. During instrumentation canals were irrigated with 5 mL saline.
The irrigation procedure in all groups was performed with a NaviTip irrigation needle (30-G; Ultradent Products Inc, South Jordan, UT), placed 2 mm short of the working length. Once the shaping of the root canals was completed, according to the final irrigation procedure, all canals were irrigated with 5 mL of 17% EDTA solution (Imicryl, Konya, Turkey), 5 mL of 5.25% NaOCI solution and 5 mL of saline, respectively.
After the quality of obturation was ensured with radiographs, coronal seal was provided with glass ionomer cement (Amalgomer, AHL, Kent, UK). The teeth was restored with composite resin (Filtek Z250, 3M ESPE, St. Paul, Minnesota, USA) and, then, occlusal contacts was checked and relieved where necessary.
Each patient was prescribed 400 mg of Ibuprofen and was instructed to take it every 8 hours when felt too severe and extremely unbearable pain to perform his daily activities.
Postoperative pain assessment Visual analogue scale (VAS) was used for postoperative pain assessment. After endodontic treatment, all patients were given a detailed form to record their postoperative pain levels at the 6th, 24th, 48th, 72nd hours, and 1 week later. VAS assessment in this form was explained to the patients in detail, and they were asked to mark on the form the pain they felt at the 6th, 24th, 48th, 72nd hours, and 1 week later.
One week after the treatment, patients were called by phone. The pain scores that the patients marked on the pain assessment form were learned and recorded in the patient file. According to the values recorded on the VAS, the pain levels were classified as no pain (0), mild pain (1-3), moderate pain (4-6) and severe pain (7-10).

Statistical analysis
The data were analyzed by using IBM SPSS V23.  However, its cytotoxic effects when extruded into periapical tissues are clinically worrying. 9 Currently, it has been reported that the use of the gel form rather than the solution form of NaOCI is similarly effective, so the clinical use of the former may be an appropriate  alternative to the latter. Although no statistically significant difference NaOCI, Sodium hypochlorite; n, Number of patient;* Chi-square test; **Friedman testi; a-f, There is no difference between times with the same letter.   and these studies report that more debris is extruded with conventional needle irrigation. [25][26][27] In addition, many studies in the literature evaluate the effect of irrigation activation techniques on postoperative pain.
In these studies, higher levels of postoperative pain were reported in the treatments performed using conventional needles compared to sonic, ultrasonic and laser irrigation, and postoperative pain levels were associated with the amount of debris extrusion. 5,28 Although a lack of evidence is present, we think that   endodontist was not possible due to the use of solution and gel form of NaOCI.
One of the limitations of this study is that the patients refused to come to the control sessions because root canal treatment was completed in one session. Therefore, pain levels were collected by phone calls. Although the clinicians could not be blinded due to the nature of the study, the researcher who made the phone calls could be blinded about the method of treatment.

Conclusion
Within the limitations of the study, using gel or solution forms of NaOCI during chemomechanical preparation of root canals, resulted in similar postoperative pain. For both formulations, pain level decreased over time.

Conflict of interest
The authors deny any conflicts of interest related to this study.