Saudi Endodontic Journal

: 2022  |  Volume : 12  |  Issue : 2  |  Page : 149--157

Evaluation of the impact of two irrigating solutions on postendodontic treatment pain in teeth with pulpal necrosis: A systematic review of randomized clinical trials and updates

Faisal Alghamdi1, Leena Sabri2, Abeer Lamfon2, Abeer Abduljawad2, Samar Alzubaidi2,  
1 Department of Oral Biology, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
2 Department of General Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia

Correspondence Address:
Dr. Faisal Alghamdi
Department of Oral Biology, Faculty of Dentistry, King Abdulaziz University, P. O. Box 80209, Jeddah 21589
Saudi Arabia


Introduction: Some irrigating solutions have the potential to induce postendodontic treatment pain (PETP). Unfortunately, there is no clear guidance of suitable irrigating solution to contribute in reducing the PETP in the current literature. This study aimed to collect and evaluate all available updated studies that investigated the impact of sodium hypochlorite (NaOCl) against chlorhexidine (CHX) on PETP following root canal therapy in permanent teeth with pulpal necrosis. Materials and Methods: The reviewers searched PubMed, Scopus, Web of Science databases, and Google Scholar as an engine to retrieve relevant randomized clinical trials (RCTs). RCTs were done on comparing the effect of NaOCl and CHX on PETP in teeth of adult patients with pulpal necrosis. Reviews, animal studies, and other irrelevant studies were excluded. This systematic review was carried out in accordance with the preferred reporting items for systematic review and meta-analysis guidelines. The reviewers selected the articles based on specified eligibility criteria, performed data extraction, and evaluated the risk of bias. Results: Four articles met the inclusion criteria for the systematic review. Two studies were deemed to have a low risk of bias. The outcomes illustrated no statistically significant difference regarding PETP between the two irrigating solutions. Conclusions: Based on current studies, this review found that neither NaOCl nor CHX irrigating solutions could ensure the absence of PETP.

How to cite this article:
Alghamdi F, Sabri L, Lamfon A, Abduljawad A, Alzubaidi S. Evaluation of the impact of two irrigating solutions on postendodontic treatment pain in teeth with pulpal necrosis: A systematic review of randomized clinical trials and updates.Saudi Endod J 2022;12:149-157

How to cite this URL:
Alghamdi F, Sabri L, Lamfon A, Abduljawad A, Alzubaidi S. Evaluation of the impact of two irrigating solutions on postendodontic treatment pain in teeth with pulpal necrosis: A systematic review of randomized clinical trials and updates. Saudi Endod J [serial online] 2022 [cited 2022 Jul 5 ];12:149-157
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Full Text


Necrotic pulp is a clinical condition that indicates death of the dental pulp, it is asymptomatic but may be associated with pain or discomfort on pressure from the periradicular tissues.[1] Irrigating solutions are used for root canal treatment and they play a vital role in the elimination of microorganisms and provide various mechanical and chemical functions.[2] To eliminate pulp tissues and bacteria, several irrigating solutions were used.[3] Sodium hypochlorite (NaOCl) has been the most frequently utilized irrigating solution for root canal cleaning and disinfection for many years.[4] Several studies revealed endodontic applications of NaOCI, such as irrigating root canals, dissolving tissues, and eliminating dental microbes. Those dental benefits are owing to NaOCI characteristic of depressed resistance to flow allowing it to penetrate the canal's inner structure.[5] On the other hand, NaOCI doses in high concentrations could cause the bursting of red blood cells, create ulcers, prevent neutrophiles movement, destroy fibroblast and endothelial cells, and undermine facial nerves.[6] As a result, novel alternatives to root canal irrigation have evolved to mitigate these consequences.[7]

Chlorhexidine (CHX) has been indicated as an alternative irrigation agent in root canal instrumentation, due to its antibacterial properties. Unlike NaOCl, CHX does not irritate periapical tissues. However, it lacks the ability to dissolve tissue, NaOCl is clearly preferable.[8] The antibacterial effects of CHX are dependent on the level of the drug's active ingredient and the presence of dental tissue. Furthermore, 2% CHX has better antimicrobial efficacy than 0.12% CHX.[9] Some authors recommended CHX as a suitable irrigation option, particularly in cases of continuous Enterococcus faecalis[10] and as a final irrigation solution.[11] Allergic responses to CHX have been documented in the current literature.[12],[13] Moreover, CHX can cause the secretion of by-products including parachloroaniline and reactive oxide species, both of which are carcinogenic in humans.[14]

Pain in an endodontically treated tooth can be one of the manifestations presented after the procedure, patients with preoperative pain can have a higher incidence of postoperative pain,[15] Females more frequently experienced pain (65%) than males (35%),[16] however, factors associated with increased incidence of postoperative pain not scientifically clear. It has been proven that postoperative pain severity decreases gradually over time.[17] A systematic review[18] was conducted in 2008; which noted a prevalence rate ranging from 3% to 58% for pain after the endodontic therapy. The majority of the etiologic causes of postoperative pain were associated with inadequate disinfection, poor removal of residual tissue, and extrusion of contaminated debris into periradicular tissue.[19],[20],[21]

Even though numerous experimental studies and reviews have focused on the various clinical relevance's of irrigating substances (NaOCl and CHX) and even evaluated their efficacy in clinical trials,[22],[23] few systematic reviews have been conducted on the influence of these two irrigating solutions on postendodontic treatment pain (PETP). Thus, the aim of this review article was to collect and evaluate all available studies that investigated the impact of NaOCI against CHX on PETP following root canal therapy in permanent teeth with pulpal necrosis.

 Materials and Methods

Study protocol and registration

This study was conducted by two independent reviewers following the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines.[24] The protocol was registered in the International Prospective Register of Systematic Reviews: CRD42021262964.

Research question

The research question was framed as the following:

”In necrotic teeth subjected to endodontic treatment, can NaOCl produce greater postendodontic discomfort than CHX?”

Information sources

An electronic search was restricted to relevant articles published in the English language in the period from 2011 to 2021 due to the lack of updated reviews that were covered in this period. Furthermore, limited published articles and reviews cover this research area in the dental field.

Literature search strategy

An intensive electronic search was conducted in May 2021. The literature search was conducted using the following electronic databases: Public Medline (PubMed), Scopus, Web of Science, and Google Scholar digital databases. The search was conducted using the following combination of keywords and Boolean operators (”AND,” “OR”): ([pain] OR [postoperative pain] OR [postendodontic pain]) AND ([Hyperemia] OR [Edema] OR [Hyperesthesia] OR [Fis tula]) AND ([nonvital tooth] OR [necrotic tooth]) AND ([root canal preparation] OR [root canal instrumentation] OR [root canal therapy]) AND ([root canal irrigants]) AND NaOCl AND CHX OR [CHX gluconate]). The electronic search was complemented by a manual scan of the references list of included publications as well as contacting the authors of selected papers for further data or clarification. A detailed description of the search strategy is outlined in [Table 1].{Table 1}

Eligibility criteria

Studies were included if they followed the following applied criteria:

Published randomized clinical trial (RCT) studies were done on the PETP in adult patients with necrotic pulpPublished studies that show the effect of NaOCI against CHX to reduce the PETPStudies were conducted on patients that had pulpal necrosis with/without periapical lesions and root canal treatment was done with NaOCI and CHX as intracanal irrigationScientific papers were published between 2011 and 2021Scientific papers that were published in the English language.

Studies were excluded if they met any of the following applied criteria:

Narrative/critical or systematic reviewsIn vitro studies, case report/series studies, and in situ studiesEditorial or personal opinion articlesPublished studies that focused only on primary teeth or teeth with vital pulp/previously treatedPublished studies were done on the different clinical relevance's of the irrigating substances (NaOCl and CHX) related to the antimicrobial effect, number of endodontic treatment visits, instrumentation techniques, and excluded the PETPScientific papers that illustrated different types of intracanal irrigation to reduce the PETP and excluded the NaOCI or CHX usedPapers that discussed the effect of NaOCI and CHX to reduce the PETP by percentages and samples taken from animal sources.

Critical appraisal

Five independent reviewers (5 general practitioners) screened the titles and abstracts of the studies for the eligibility criteria following PRISMA guidelines. After reading the title and abstract, the Cohen's Kappa test was used to assess agreement between the reviewers on the eligibility of the retrieved studies. If there was a disagreement between reviewers, it was resolved following a conversation with a senior reviewer who is familiar with systematic review methodology. The Cohen kappa interagreement rate was 0.81 (labeled as “almost perfect”).

Data extraction

The five reviewers examined the entire paper separately and took into account the following variables: Title, abstract, material and methods, and major results. Four reviewers gathered all essential information from each included paper and entered it into a predesigned Microsoft office excel collection form created particularly for the data.

Data items

Data were gathered and organized into columns with the following information: Study (author and year), study design, sample (number, type of teeth), gender, the age range of the patients/mean average of age, the sample size of necrotic teeth (Number, NaOCI vs. CHX groups), preoperative pain, preoperative medication, pulp diagnosis, instrumentation system, presence of the foraminal enlargement, instrumentation system with size/taper file diameters used, the concentration of the irrigating solution, the number of endodontic visits, intracanal medication, sealing technique, type of cement, crown sealing, outcomes of each study. In addition, the evaluation techniques for analyzing postendodontic treatment symptoms (evaluation tools, follow-up period, categorization, analyzed symptoms, postoperative medications, pain outcome).

Risk of bias assessment of included studies

The quality of the approved studies was evaluated using the risk of bias assessment tool outlined in the Cochrane risk of bias tool (Risk-of-bias VISualization [robvis]).[25] This assessment was completed and verified by four reviewers independently. The risk of bias assessment tool includes seven specific domains. The domains were determined to be either “low,” “unclear,” or “high.” These assessments were reported for each selected study in the “risk of bias” figures. The review authors' judgment about the risk of bias for each selected study was categorized into “low risk,” or “unclear risk,” or “high risk” as the following: (1) Low risk of bias: All domains were assessed as “low risk,” (2) Unclear risk of bias: At least one domain was assessed as “unclear.” (3) High risk of bias: At least one domain was assessed as “high risk.”

Primary and secondary outcome measurements

Studies were evaluated and compared the effectiveness of two chemical substances (NaOCl and CHX) used in endodontic treatment on PETP for teeth with pulp necrosis as primary outcomesStudies were compared different instruments for analyzing PETP symptoms as secondary outcomes.

Synthesis of results

The data items were gathered in tables. In the first table, study characteristics were prepared as mentioned in data items. The second table was included evaluation techniques for analyzing postendodontic treatment symptoms (evaluation tools, follow-up period, categorization, analyzed symptoms, postoperative medications, pain outcome). The results were synthesized descriptively as complementary data.


Study selection

The article search yielded 585 records from all databases during the initial title and abstract review. After duplicate records were removed, the remaining 406 articles were screened. Three hundred and sixty-seven articles based on abstract and title were excluded. Thirty–nine full-text articles passed screening and were then check for eligibility. Only 35 studies were excluded from this review due to different reasons. Only 4 studies ultimately being included in the systematic review. A flow chart summarizing the search for articles in this systematic review is shown in [Figure 1].{Figure 1}

Study characteristics

The four human studies chosen for the review were conducted within the past 10 years and met all the inclusion, but none of the exclusion criteria. These studies investigated the impact of two different irrigating solutions (NaOCI and CHX) regarding the PETP subsequent to root canal therapy in permanent teeth with pulpal necrosis. The samples were examined to see if PETP was absent or present after using the mentioned two irrigating solutions. All the included studies in this systematic review were RCT study.[26],[27],[28],[29] The four studies in total had a sample size of 597 patients and 658 teeth. The sample size and age range of the studies were 62–240 patients and 13–79 years, respectively. The mean age of the total sample was reported in all four studies.[26],[27],[28],[29] All the included studies were conducted in Brazil.[26],[27],[28],[29] A total of three studies were reported the gender of the patients (131 males and 226 females).[26],[28],[29] Gender has not been determined in one study (240 patients).[27] All the selected articles that investigated uniradicular and multiradicular teeth[26],[27],[29] except one study included uniradicular teeth only.[28] Among the 658 teeth, 424 were necrotic pulp teeth, while the other 234 teeth were either irreversible pulpitis or previously treated.[26],[27],[28],[29] The other study characteristics of the four studies (preoperative pain, preoperative medication, instrumentation system, presence of the foraminal enlargement, surgical diameter of the instrument, the concentration of the irrigating solution, the number of endodontic visits, intracanal medication, sealing technique, type of cement, and crown sealing, and outcomes of each study) are collected and summarized in [Table 2].{Table 2}

Primary outcomes

All four studies described the effectiveness of two chemical substances (NaOCl and CHX) used in endodontic treatment on PETP for teeth with pulpal necrosis.[26],[27],[28],[29] Among 424 necrotic teeth, 245 teeth with NaOCI group and 179 teeth with CHX group as shown in [Table 2]. Two studies illustrated NaOCI and CHX were associated with decreased PETP rates.[28],[29] The other two studies were; one study showed no influence of two irrigating solutions on PETP[27] and the other study[26] concluded by the 8.25% NaOCl solution group was appeared to be safe, with the decrease in the incidence of PETP when compared to the other irrigating solutions.

Secondary outcomes

The secondary outcomes were evaluated symptoms of postendodontic pain after endodontic treatment. The period of symptom evaluation was at least 24 h and no more than 7 days after the postendodontic treatment [Table 3]. The studies used the visual analog scale (VAS) tool,[26] simple verbal classification form questionnaire,[28] and a self-explanatory questionnaire.[29] While one study[27] didn't report the type of evaluation used (loss of data). In addition to pain symptoms, two studies evaluated the presence of pain and discomfort.[26],[27] While one study evaluated the presence of pain and the number of used analgesic tablets[28] and another study evaluated the presence of pain alone.[29] Regarding the use of medication, in cases in which any type of pain or discomfort after endodontic treatment was reported, the endodontist was informed, and the patients were instructed to use anti-inflammatory drugs[26],[27] and analgesics.[28],[29] Thus, four studies found no statistically significant difference regarding the use of the NaOCl and CHX in the evaluation of PETP.[26],[27],[28],[29]{Table 3}

Risk of bias assessment

The quality of the included studies was assessed using the risk of bias assessment tool outlined in the Cochrane risk of bias tool (Risk-of-bias VISualization (robvis)).[25] The majority of studies mentioned in this review had a low risk of bias in all the seven domains with different percentages [Figure 2]. When analyzing the overall risk of bias among the four studies, two studies (50%) were classified as a high risk of bias[27],[29] and the other two studies (50%) had a low risk of bias[26],[28] as shown in [Figure 3]. Two studies were assigned a high risk of bias score due to discrepancies in provided information regarding the following domains: Allocation concealment, blinding of participants and personnel and blinding of outcomes assessment. The other studies received a low risk of bias score because there was enough information and valid results to make a clear judgment [Figure 3].{Figure 2}{Figure 3}


Although the present literature shows that endodontic treatment is often successful,[30],[31],[32],[33] the existence of PETP may result in a negative outcome.[18] The effect of two irrigating solutions (NaOCl and CHX) on PETP was investigated in this systematic review. It is critical to highlight that systematic review of RCTs has a significant link with clinical reality.

The pot-endodontic treatment pain is a substantial clinical discomfort, and the irrigation phase should be conducted with caution to prevent such therapy discomfort. When nonvital teeth were subjected to endodontic treatments during the root canal instrumentation, the use of irrigating devices and substances causes the ejection of debris and/or the chemical itself, increasing the risk of discomfort and inflammation of the periapical tissues.[34] When compared to vital pulps, the use of a radiopaque solution that the irrigation in root canals with necrotic pulps tends to flow beyond the instrumented area, and if extruded in the periradicular tissues, can fill random gaps, according to a study by Salzgeber and Brilliant.[35] In the four included studies, different concentrations and irrigation regimens of NaOCl (2.5%–5.25%) and CHX (0.2%–2%) were applied to assess pain and postendodontic treatment symptoms. In any case, NaOCl or CHX should be employed with caution throughout therapy to avoid pain. Only one of the included studies[28] measured the injection length of the chemical substance via the rubber stop in up to 3 mm short of the working length to decrease the danger of extravasation, to standardize the use of irrigating solutions and decrease bias.

The four selected articles[26],[27],[28],[29] didn't illustrate a statistically significant difference in pain level among the two irrigation solutions; in contrast to the study by Demenech, et al.[26] that verified a significant difference only at preparation time ≥10 min and the presence of overfilling maintained in the multivariate model incorporating irrigants. This finding might imply that the probable source of discomfort is related to the higher number of cases in the necrotic pulp group, according to this study.[26] In addition, the presence of bacteria and their endotoxins in a root canal with necrotic pulp may lead to discomfort.[36],[37]

The influence of the use of hand, rotary, and reciprocating instruments on PETP following the procedure has been investigated. Several studies[38],[39],[40],[41] have found that rotating and reciprocating systems cause less PETP compared with hand files and other systems. However, operator experience is a factor that also affects PETP following the procedure.[42] Even though the included studies used rotary[27],[29] and reciprocating[26],[28] instrumentation systems for root canal preparation, this variable poses no risk of bias for this systematic review because the different irrigating solutions (NaOCl or CHX) were compared using the same operative technique in all the included studies.

Four studies[26],[27],[28],[29] finished their endodontic therapy in a single endodontic visit, and they did not illustrate a statistically significant difference in PETP between the two groups of irrigating solutions [Table 2].

Although PETP is common in some endodontic cases, it's an uncomfortable and undesired sensation following endodontic therapy; nevertheless, it's crucial to note that pain evaluation is subjective, and each person's pain threshold is unique.[43] As a result, to achieve a satisfactory result in the evaluation of pain, an appropriate scale or questionnaire is required, so that the questions are absorbed by the patients and well analyzed by the researchers.

da Silva, et al.[28] and Almeida, et al.[29] used questionnaires to assess pain, while one study[26] used VAS to assess pain intensity and changes that occur during endodontic therapy but cannot detect the reason in agreement line with the findings of the published study used same evaluation tool (VAS).[44] Furthermore, the type of evaluation used in Bourreau et al., study was not reported.[27] However, the use of a pain scale is critical in this assessment. When correctly designed and used, the VAS can be deemed a viable scale instrument for estimating pain severity.[45]

Therefore, the data of these four selected systemic review studies should be interpreted with caution and additional well-designed RCTs comparing the effectiveness of NaOCl and CHX for PETP using clinical outcomes and analyzing uni-and multi-rooted teeth with adequate sample size and objective data are needed, to decrease the risk of bias and allow for better evaluation and interpretation of PETP associated to the use of endodontic irrigators.

Study strengths and limitations

The strength of this systematic review includes a thorough comparison of all peer-reviewed studies published within the 10 years in line with the inclusion and exclusion criteria. It presents comprehensive knowledge on the effect of NaOCI and CHX on PETP. To complete this review, the reviewers used Public Medline (PubMed), Web of Science, and Scopus as databases, and also Google Scholar as a search engine. One advantage of using Google Scholar was to prevent missing any appreciated research published in journals that are not cited in PubMed, Web of Science, and Scopus databases. Because of the comprehensive investigation in the literature and rigorous methodological qualification, this systematic review can be considered as low risk of bias. However, several limitations that might affect the quality of the evaluated findings must be considered. First, nonstandardization of pain scale evaluation durations was noticed. Second, the lack of data and variations in sample distribution by gender suggest a possible risk of bias, given that females have lower thresholds and tolerance to pain than males.[44] Meta-analysis could not be done due to variation in pain evaluation periods and missing data for provided by studies indicating the number of participants with PETP in nonvital teeth for each group investigated. In addition, PETP can be caused by a variety of reasons, including pulpal and periapical conditions, insufficient instrumentation, debris extrusion, occlusal trauma, preoperative discomfort, periodontal pathosis, and irrigation solution extrusion.[46] Furthermore, the VAS is deemed a subjective method that assesses pain only and this condition may be associated with other variables as well, but because the articles are standardized with similar groups, this decreases the risk of bias.


Regardless of the number of heterogeneous studies that differed largely in their designs, all the included studies were standardized with similar groups that reduced the risk of bias and helped in justification of the results and conclusions as mentioned in the present study strength and limitations section, it can be concluded that neither NaOCl nor CHX irrigating solutions could ensure the absence of PETP.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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