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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 3  |  Page : 189-195

Effect of two different volumes of sodium hypochlorite on endodontic treatment outcome following single-visit root canal treatment: A split-mouth, double-blind, randomized controlled trial


1 Department of Dentistry, AIIMS, Nagpur, Maharashtra, India
2 Private Practitioner, Nagpur, Maharashtra, India
3 Department of Community Dentistry, YMT Dental College, Navi Mumbai, Maharashtra, India

Date of Submission11-Jan-2022
Date of Decision09-Mar-2022
Date of Acceptance13-Apr-2022
Date of Web Publication30-Sep-2022

Correspondence Address:
Dr. Ganesh R Jadhav
Department of Dentistry, AIIMS, Nagpur, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_10_22

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  Abstract 


Aim: This split-mouth (SM), randomized controlled trial was planned to assess the influence of two different volumes (15 ml and 25 ml) of 2.5% of sodium hypochlorite (NaOCl) on the endodontic treatment outcome of teeth with apical periodontitis (AP) by radiographic and clinical evaluation.
Materials and Methods: The study protocol was approved by the ethics committee (25/XX/IEC/2017/11). Using block randomization, permanent lower molars with pulp necrosis and chronic AP (periapical index [PAI] of 3 or above) were allotted to two treatment groups as Group I (low volume [LV]) and Group II (high volume (HV)) wherein 3 ml and 5 ml of NaOCl irrigant were used after each Mtwo rotary file, respectively. This NaOCl was activated by a sonic handpiece. With power at 0.80, P < 0.05, and minimum clinically significant mean intergroup difference set at 0.40 units (standard deviation – 0.88 unit) while using the change in PAI score as the primary outcome, a total of 46 subjects per group were recruited to adequately show a difference in success at the 12-month follow-up. Clinical (at 24 h, 3, 6, 9, and 12 months) and radiographic (6 and 12 months) assessment of all cases was done.
Results: Due to SM design of the study, there was no difference in the demographics of subjects between both the groups. Pain scores between both groups were statistically nonsignificant preoperatively (P = 0.857) and at 24 h (P = 0.852). However, there was statistically significant difference in preoperative and 24 h pain scores in Group I (P = 0.000) and Group II (0.000). Comparison of intergroup preoperative and 12-month follow-up PAI scores revealed no statistically significant difference (P = 0.667). However, there was statistically significant difference in preoperative and 12-month follow-up PAI scores in Group I (P = 0.000) and Group II (P = 0.000). Intergroup comparison of PAI scores at baseline (P = 0.894) and follow-up (P = 0.526) revealed no significant difference.
Conclusion: Based on the results of the present study, it can be suggested that there is no significant advantage of using HV of NaOCl over LV as far as periapical healing and postendodontic pain are concerned.

Keywords: Apical periodontitis, randomized controlled trial, sodium hypochlorite, split-mouth study, visual analog scale


How to cite this article:
Jadhav GR, Mittal P, Kalra D. Effect of two different volumes of sodium hypochlorite on endodontic treatment outcome following single-visit root canal treatment: A split-mouth, double-blind, randomized controlled trial. Endodontology 2022;34:189-95

How to cite this URL:
Jadhav GR, Mittal P, Kalra D. Effect of two different volumes of sodium hypochlorite on endodontic treatment outcome following single-visit root canal treatment: A split-mouth, double-blind, randomized controlled trial. Endodontology [serial online] 2022 [cited 2022 Nov 30];34:189-95. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/3/189/357693




  Introduction Top


Intracanal milieu that favors bacterial growth is responsible for the development of apical periodontitis (AP). Endodontic treatment of teeth with AP has two principal objectives. The first immediate objective is to manage intraoperative pain and to avoid postoperative flare-up. The second long-term objective is to achieve clinical and radiographic healing. These objectives are achieved by the combination of mechanical action of endodontic instruments and chemical action of irrigants.[1] Sodium hypochlorite (NaOCl) has long been recognized as the most popular intracanal irrigant due to its antimicrobial, antibiofilm, and pulp tissue-dissolving properties.[2],[3],[4] These properties of NaOCl can be improved by either altering its concentration/volume or use of various irrigant activation devices.

Various concentrations of NaOCl are researched extensively to evaluate the difference in its efficiency. Verma et al. did not find any advantage of using higher concentration of NaOCl over lower concentration as far as endodontic treatment outcome is concerned.[5] During root canal irrigation, NaOCl may go beyond the root apex to the periapical region despite the use of side venting needles with minimum apical pressure.[6] This unavoidable, minute extrusion at higher concentration can irritate the periapical tissue.[7] Hence, considering the cost–benefit ratio, it is not recommended to use NaOCl at higher concentrations to improve its efficiency.

The action of NaOCl is due to its chlorine content.[8] This chlorine is consumed fastly within the first 2 min during the dissolution of organic tissue, and its properties are diminished in the later phase. Therefore “reservoir” of the accessible NaOCl is essential for its continued chemical action.[9] This can easily be achieved using larger volumes of NaOCl. Moreover, such large volume may allow the use of NaOCl at lower concentration to avoid any toxic effect to the periapical tissue. In a study by Huang et al., it was found that increased NaOCl volume was related with the higher dissolution of a biofilm from root canals.[10] On the contrary, Del Carpio-Perochena et al. found that NaOCl volume had no relation with its chemical-dissolving capacity on multispecies biofilms.[11] These conflicting results call for further investigations. Very few in vitro and ex vivo studies have evaluated the influence of NaOCl volume on various aspects of intracanal disinfection such as dissolution of biofilm and bacterial count reduction. However, till date, no randomized controlled trial (RCT) evaluated the effect of volume of NaOCl on its mechanism of action. Hence, there is a lack of universal consensus among clinicians conducting endodontic treatment regarding the standardized quantity of NaOCl needed for the best endodontic treatment outcome. Moreover, there is a paucity of evidence-based analysis of cost–benefit ratio of higher volumes of NaOCl. During conventional needle irrigation, entrapped air in the root canal, known as “vapor lock effect,” hinders the replacement of irrigants and therefore, the efficiency of irrigation may be limited.[12] Sonic activation of irrigant using devices such as EndoAactivator (EA) removes this “vapor lock effect,” thus improving the efficiency of irrigant.[13]

Hence, this split-mouth (SM), RCT was planned with a primary objective to assess the influence of two different volumes (15 ml and 25 ml) of 2.5% of NaOCl on the endodontic treatment outcome of teeth with AP. The secondary objective was to assess the incidence of postoperative pain.


  Materials and Methods Top


The study was designed as a SM, crossover RCT following the Consolidated Standards of Reporting Trials checklist [Figure 1].[14] The clinical trial was performed from March 2017 to January 2020 (around 34 months) after getting institutional ethical approval (25/XX/IEC/2017/11) from multiple centers in a city. The sample size was determined using the estimates of mean and standard deviation (SD) values from literature using the following formula:[15]
Figure 1: Consolidated standards of reporting trials flow diagram

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where Za is the z variate of alpha error, i.e., a constant with value 1.96, Zβ is the z variate of beta error, i.e., a constant with value 0.84.

With power at 0.80, P < 0.05, and minimum clinically significant mean intergroup difference set at 0.40 units (SD –0.88 unit) while using the changes in periapical index (PAI) score as the primary outcome, a minimum sample size of 45 subjects per group was required to adequately show a difference in success at the 12-month follow-up. Adequacy of sample size was ensured by assessing larger sample size (n = 79).

Inclusion and exclusion criteria

Inclusion criteria were healthy adults (ASA Class I or II) needing nonsurgical root canal treatment in asymptomatic/symptomatic (no pain to mild pain on Visual Analog Scale [VAS]), contralateral, permanent lower molars with pulp necrosis (diagnosed by negative response to pulp sensibility tests and confirmed by lack of bleeding on root canal opening), chronic AP (PAI of 3 or above), and intact contacts with proximal as well as opposing teeth. Tooth that is periodontally weak (according to pristine periodontal health criteria), previously accessed, or that requires to be used as an abutment was not included in the study. Subjects who have taken analgesic in the past 12 h or antibiotics in the past 2 weeks or those with a history of tobacco consumption were also excluded from the study. All participants (n = 46) were explained about the treatment protocol and written informed consent was taken.

Randomization method

Randomization of all mandibular molars into the two study groups was achieved using an online random generator which uses a permuted block randomization protocol (randomization.com). According to the generated code, a chairside clinical assistant loaded and supplied the respective volumes of NaOCl during the entire session of treatment. The irrigation syringe was covered using a nontransparent tape so as to conceal the volume of NaOCl loaded in a syringe. It was ensured that the participant, the primary investigator, and the evaluator were unaware of the volume of the irrigant used.

Standardization of radiographs and training for interpretation of periapical index

All radiographs were exposed using a long cone paralleling technique. Standardization of vertical and horizontal angulations was achieved using a customized addition silicone (Aquasil, Dentsply Maillefer, Tulsa, OK, USA) bite block held in a RINN sensor positioning device (Dentsply Maillefer, Tulsa, OK, USA). All radiographic parameters such as voltage (65 kV), current (5 mA), and exposure time (0.10 s) were kept constant for every radiograph using RadioVisioGraphy Imaging System (EZ Sensor Classic size 1.5, Vatech India Pvt. Ltd., New Delhi, India) and DC X-ray unit (Optima, Alerio X-rays, Tamil Nadu, India). The periapical lesion on radiograph was scored on the basis of PAI. Two observers (RA, SS – who were not related to the study with more than 8 years of work experience after postgraduation) were trained to interpret the PAI on radiograph by thorough, multiple training sessions until a joint agreement was arrived between them. Interobserver variability was rechecked by reevaluating the PAI for the second time 2 weeks after the initial examination by the same observers (RA and SS). In case of the disagreement between the observers, the higher of the scores was assigned. These findings were compiled on a Microsoft Office Excel Sheet (v. 2019, Microsoft Redmond Campus, Redmond, Washington, USA).

Working length determination

All endodontic procedures were performed by a single operator (GJ – an endodontist with more than 9 years of experience). The traditional Halsted technique was used to administer the inferior alveolar nerve block using 2% lignocaine with 1:80,000 epinephrine (Xicaine, ICPA Health Products Ltd., Mumbai, Maharashtra, India). Under rubber dam isolation, access opening was done and the pulp cavity was debrided thoroughly using sterile 10 ml normal saline (NS) (0.9% NaCl, M. A Surgical Distributors, Mumbai, Maharashtra, India). The glide path was established with an ISO 10 size C-PILOT file (VDW, Munich, Germany). C-PILOT file of size ISO 15 was used to determine the working length (WL) using an electronic apex locator (Root ZX Mini; J Morita, Tokyo, Japan). During WL determination, the file was advanced apically until it gives a signal of reaching the “apex.” This signal can be recognized in three ways, i.e., a digital display reading of “0,” a pulsing audition, and a flashing light. The file was then withdrawn till the apex locator gave the reading from “apex” to “0.5.” A silicone stopper was set at this length of file and it was documented as the WL of that particular root.

Chemomechanical preparation, obturation, and postendodontic restoration

Chemomechanical preparation was carried out using Mtwo rotary file system (VDW, Munich, Germany), following the manufacturer's instructions. It is recommended to use Mtwo rotary file system using single length technique along with brushing file movement. All canals were prepared using the following sequence of Mtwo files: 10/.04, 15/.05, 20/.06, 25/.06, and 30/.05. In the case of wide oval canals, such as distal canal, hand filing was done using 30/.02 #H file. In Group I low volume (LV) and Group II high volume (HV), 3 ml and 5 ml of 2.5% NaOCL (Cmident, New Delhi, India) irrigants were used after each file, respectively, by positioning a 30-G, 25-mm needle (NeoEndo Ltd., UK), 2 mm short of WL. Totally, 15 ml and 25 ml of 2.5% NaOCl irrigants were used in Group I and Group II, respectively. This NaOCL was activated by a sonic handpiece (EndoActivator, Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) set at 10,000 cycles/minute after using 30/.05 file. An activator tip of 25/0.04 was passively inserted in the canal within 2 mm of the WL. The tip was activated and moved in short 2–3 mm vertical strokes. The canals were cleaned with 5 ml of NS, and then 5 mL 15% ethylenediaminetetraacetic acid (EDTA) irrigant (Largal Ultra, Septodont, Saint Maur des Fosses, France) was used for 1 min. Finally, the canals were again washed with 5 ml of NS and dried with sterile paper points (Dentsply Maillefer, Ballaigues, Switzerland). Obturation was completed using epoxy resin-based root canal sealer (AH Plus sealer, Dentsply Maillefer, Ballaigues, Switzerland), sectional filling (warm vertical compaction), and backfilling using thermoplastic injection system (Calamus Dual, Dentsply Maillefer, Ballaigues, Switzerland). Postendodontic restoration was done with bonded adhesive composite resin (Z100; 3M Dental Products, Saint Paul, Minnesota, USA). An immediate postoperative radiograph was taken using preset exposure parameters. For root canal treatment of contralateral mandibular molar, the patient was recalled after 2 weeks and the same protocol was followed except for the volume of the NaOCl irrigant used.

Evaluation criteria

Clinical evaluation

Clinical evaluation of all cases was done at 24 h, 3, 6, 9, and 12 months by the second operator (PM – an endodontist with more than 5 years of experience). Cases were considered clinically successful if there was absence of pain, tenderness, sinus tract, associated soft-tissue swelling, tooth mobility (less than Grade 2), etc., Pain was evaluated using a VAS preoperatively as well as at 24 h after intervention. It was composed of four categorical scales on a 100-mm line with the cut points at 0–4 mm, 5–44 mm, 45–74 mm, and 75–100 mm, corresponding to no, mild, moderate, and severe pain, respectively. A respondent was asked to draw a line perpendicular to the VAS line on the point corresponding to his or her pain. The score was ascertained by calculating the distance between “no pain” and the patient's mark with the help of a ruler.

Radiographic evaluation

The same observers (RA and SS) carried out radiographic evaluations at 6 and 12 months. The periapical lesion on radiograph was scored on the basis of PAI. It is a scoring system for registration of AP on radiograph. The change in PAI observed at the 12-month follow-up visit was assessed [Figure 2].
Figure 2: Baseline (A), postobturation (B), and 12-month follow-up (C) radiograph of bilateral, mandibular molars in Group I and Group II

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Clustering effect was managed by blinding the second operator (PM.) as well as observers (RA and SS) during the follow-ups. Data obtained were compiled on a Microsoft Office Excel Sheet (v. 2019, Microsoft Redmond Campus, Redmond, Washington, USA). Data were subjected to statistical analysis using the Statistical Package for the Social Sciences (SPSS v. 26.0, IBM, Chicago, IL, USA). Descriptive statistics such as frequencies and percentages for categorical data and mean and SD for numerical data were depicted. The normality of numerical data was checked using Shapiro–Wilk test and was found that the data did not follow a normal curve; hence, nonparametric tests were used for comparisons. Intergroup comparison was done using Mann–Whitney U-test and intragroup comparison was done using Wilcoxon signed-rank test (up to two observations). For all the statistical tests, P < 0.05 was considered to be statistically significant.


  Results Top


Out of 81 patients enrolled in the study, 31 patients (26 patients were not meeting inclusion criteria and five patients refused to participate) were excluded. All participants were enrolled within the period of 34 months. Two patients were lost to follow-up postoperatively due to re-location of their residence. Two molars were eliminated due to overfilling (n = 1) and broken instrument (n = 1). A total of 23 patients were available for the final analysis with 46 teeth in each group. Due to SM design of the study, there was no difference in the demographics of subjects between both the groups. Moreover, inclusion–exclusion criteria were followed strictly so as to keep comparable clinical as well as radiographic characteristics in both the groups. The mean preoperative pain score was 7.94 ± 8.172 in Group I and 8.08 ± 8.417 in Group II and were nonsignificantly different (P = 0.857) [Table 1]. At 24 h, the mean VAS was 3.50 ± 6.274 and 3.08 ± 5.453 in Group I and Group II, respectively and were statistically nonsignificant (P = 0.852). However, there was statistically significant difference in preoperative and 24 h pain scores in Group I (P = 0.000) and Group II (0.000) [Table 2]. Comparison of intergroup preoperative and 12-month follow-up PAI scores revealed no statistically significant difference (P = 0.667) [Graph 1]. However, there was statistically significant difference in preoperative and 12-month follow-up PAI scores in Group I (P = 0.000) and Group II (P = 0.000). No patient in either group reported severe pain at 24 h. Intergroup comparison of PAI scores at baseline (P = 0.894) and follow-up (P = 0.526) revealed no significant difference.
Table 1: Intergroup comparison (n=48 per group) for the visual analog scale and periapical index

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Table 2: Intragroup comparison for the visual analog scale and periapical index

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  Discussion Top


In dentistry, the trialist has a choice to randomize experimental treatment either over participants or over intra-oral sites.[16] In case of randomization over participants (noncrossover or parallel-group design), all sites of a participant were given the identical line of treatment. This is the simplest and the most popular study blueprint in a clinical trial. In randomization over intraoral sites, various treatment protocols are randomly allocated to different oral sites, and SM design is one of such randomization schemes where two treatments are randomly assigned to one of the two halves of the mouth. Different individuals show different healing kinetics of periapical lesions due to genetic variability.[17] This variability can easily be evaded in SM studies that eliminate the intersubject variability as well as all confounding factors that improve the power of a trial.[18],[19] Moreover, in evidence-based dentistry, the highest level of evidence of any treatment protocol is achieved by conducting a well-planned RCT. Hence, the present study was planned as SM RCT which was conducted over 18 months. Furthermore, all other confounding factors were kept under control by adopting strict inclusion criteria and methodology so that the exclusive effect of NaOCl volume can be determined.

Long-term success of endodontic therapy depends upon the reduction of intracanal microbial load and disruption of biofilm that harbors bacteria along with its products. It can be achieved by meticulous amalgamation of mechanical instrumentation and chemical action of irrigant. Mtwo files were preferred in the present study because of its efficiency, safety, and simplicity in usage.[20] It has “s-shaped cross-section” and “two efficient cutting edges” that facilitate minimum radial contact with deep flutes for continuous upward evacuation of dentinal shavings. Moreover, its design improves flexibility and fatigue resistance that help in preserving the original canal curvature.[21] All endodontic rotary instruments act on the central body of the canal, leaving canal fins, isthmi, and cul-de-sacs untouched even after completion of the preparation.[22],[23],[24],[25],[26] These areas harbor tissue debris, microbes, and their by-products that result in persistent periradicular inflammation.[27] Therefore, irrigation is an essential part of root canal debridement as it allows cleaning beyond what might be achieved by mechanical instrumentation alone.[28] Although various newer irrigants are researched extensively, NaOCl remains to be a gold standard because no study has shown any other irrigants to be more effective. To improve its efficiency, the use of NaOCl at higher concentration is not recommended as NaOCl accidents are likely to occur at higher concentrations due to its concentration-dependent cytotoxicity. In addition, its higher concentration causes dentin deproteination, collagen degradation, and reduction in dentinal microhardness.[29],[30] Previous studies have shown that intracanal microbial reduction was not found to be consistently related to the concentration of NaOCl. Hence, in the present study, one of the lowest possible but clinically effective concentrations of NaOCl (2.5%) was opted. However, literature lacks any recommendations about the volume of NaOCl needed to achieve favorable clinical and radiographic outcomes. Hence, different volumes of NaOCl were used in various clinical studies. In this RCT, two most commonly used volumes of NaOCl (15 ml and 25 ml) were compared for evaluating the clinical and radiographic success of nonsurgical root canal treatment of teeth with AP.

Despite the thorough chemomechanical procedure, complex root canal anatomy may escape the effects of instruments and irrigants. Weak mechanical flushing action from the conventional hand-held syringe needle irrigation cannot remove the debris from such inaccessible canal irregularities. Conventional hand-held syringe delivers the irrigant only 1 mm deeper than the tip of the needle, thus limiting its ability to disinfect the canals. Moreover, vapor lock effect affects its efficiency. Bacteria can penetrate the dentinal tubules up to a depth of 250 μm and thus remains protected from the antibacterial action of irrigants. These persisting bacteria and pulp tissue remnants can result in treatment failures. Hence, removal of smear layer and penetration of irrigants into such areas is essential for successful endodontic treatment outcomes. This can be achieved by irrigant agitation techniques such as use of sonic devices which generates oscillating back-and-forth tip movement. The synergistic action of such vibrating tips along with up and down movement of handpiece produces a powerful hydrodynamic phenomenon that helps in efficient root canal debridement. Hence, EA System which works with this mechanism was used in the present study. EDTA was used in this study as it improves the action of NaOCl by removing the smear layer and debris from the canal.

In the present study, the success of endodontic treatment was evaluated on the basis on radiographic and clinical outcomes at the time of recall. One-year follow-up of all cases was done as the majority of radiographic changes are evident within the 1st year. PAI score was used to evaluate the radiographic success because it has a good reproducibility and potential for early detection of healing. It has been used successfully in many epidemiological studies, clinical trials, and retrospective analysis of treatment results in endodontics. A score of 1–2 is defined as healed or minimally inflamed and a score of 3–5 is defined as diseased tissue. Literature revealed a lower success in endodontic treatment of mandibular molars with AP due to its complex anatomy. Hence, mandibular molars with necrotic pulps and AP were included in the study. Likely limitations of this study include use of two-dimensional radiographs for evaluating the periapical healing; no study was performed to determine the bacterial burden residual in the canals after irrigation with 15 ml and 25 ml of 2.5% NaOCl. Studies involving microbiological analysis along with clinical outcomes may help better understand the biology of healing after endodontic treatment.


  Conclusion Top


Based on the results of the present study, it can be suggested that there is no significant advantage of using HV (25 ml) of NaOCl over LV (15 ml). This may be because healing begins once a most favorable drop in bacterial count is achieved through endodontic procedures. Even though the microbial reduction attained using a lower volume may be relatively less, it might have been sufficient to promote the healing as the residual bacteria would have been sealed off once satisfactory obturation was performed. However, the authors recommend the use of minimum of 15 ml of NaOCl during chemomechanical procedure. The present study is the first of its kind that explores the clinical effect of NaOCl volume in permanent teeth. Although the results obtained were found to be statistically nonsignificant, this topic warrants further exploration in order to confirm the findings. Furthermore, the results of the study cannot be generalized to teeth with different clinical and radiographic findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

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