What irrigation and canal dressings are most effective in the treatment of Apical Periodontitis?


Root canal treatment (RoCT) involves a chemo-mechanical disinfection process to remove substantial microbial load present in the root canal system  which causes peri-apical pathology such as Asymptomatic Apical Periodontitis (AAP). The aim of this procedure is to maintain the affected tooth on the arch as a functional unit and restore a healthy periodontium (Nair, 2004).  Due to the complexity of the root canal system, the elimination of microbes cannot only be achieved with mechanical instrumentation but also in conjunction with the use of biocidal agents such as sodium hypochlorite (NaOCl) or chlorhexidine.  Chelating agents such as ethylenediaminetetraacetic acid (EDTA) are also often used along with NaOCl to remove the smear layer produced by mechanical instrumental and therefore achieve an effective and thorough disinfection. When RoCT is not completed in one visit, additional microbial reduction can be achieved by using interappointment intracanal medication. The most used is non-setting calcium hydroxide. Determining the most effective method of disinfection is essential to achieve predictable clinical outcomes.

The aim of this systematic review and meta-analysis was to answer two questions:

  • In patients with AAP, what is the effectiveness of instrumentation and irrigation with NaOCl and EDTA compared to any other root canal irrigant(s) in terms of clinical and patient-related outcomes?
  • In patients with AAP, what is the effectiveness of calcium hydroxide compared to any other root canal dressings in terms of clinical and patient-related outcomes?


A protocol was registered with PROSPERO and the review developed, conducted, and reported using PRISMA guidelines. Searches were conducted in English language only in SCOPUS, PubMed and Embase along with a grey literature and major journals contents search from inception to July 2021. Two reviewers independently screened, selected, and extracted data with risk of bias being assessed using a revised Cochrane risk-of-bias (RoB2). The primary outcome was ‘tooth survival’ while other important outcomes such as ‘pain, tenderness, swelling, need for medication’; ‘radiographic evidence of reduction of apical lesion size or normal periodontal ligament space’. Qualitative and quantitative data was analyzed for all selected studies and a narrative synthesis was performed. A meta-analysis was conducted with a predefined confidence interval of 95%. The overall quality of the evidence for each of the outcomes where meta-analysis was possible was rated using the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) approach by two review authors independently.


  • 6 Randomized control trials involving a total of 672 patients were included. Two studies were focusing on irrigant solutions while 4 studies were focusing on interappointment canal dressings.
  • 2 studies were considered as low risk of bias while the 4 remaining were considered as some concerns.
  • 3 studies (410 patients) contributed to the meta-analysis focusing on the comparison ‘single visit protocol versus the use of calcium hydroxide as medicament for multiple visits protocol’.
  • Meta-analysis highlighted a statistically significant difference in favour of single visit protocol compared to two visits protocol with use of calcium hydroxide as a medicament in the root canal system in between visits.
Studies Weight RR (95%CI)
Weiger et al, 2000 14.6% 1.17 [0.90 to 1.54]
Peters & Wesselink, 2002 8.2% 1.15 [0.79 to 1.66]
Paredes-Vieyra & Jimenez Enriquez, 2012 77.2% 1.09 [1.02 to 1.16]
Overall 100% 1.10 [1.03 to 1.16]


The authors concluded:-

Overall, there is moderate-grade evidence to support that single visit root canal treatment is associated with better outcomes regarding ‘radiographic evidence of normal periodontal ligament space (strict criteria)’, when compared with the use of calcium hydroxide. Similar results are reported for the outcome ‘radiographic evidence of reduction of apical lesion size (loose criteria)’, when comparing 1% and 5% NaOCl or single visit protocols versus calcium hydroxide medicament. Two percent chlorhexidine and 5.25% NaOCl and EDTA as irrigant solutions or 1% and 5% NaOCl are associated with similar outcomes regarding the outcome ‘pain at 7 days’.


The authors registered a protocol for the trial on PROSPERO and searched several major databases limiting themselves to English language. Their research protocol was adequate and enhanced by standard tools for critical evaluation. 6 randomized control trials were identified including 672 patients to address their two questions. A statistically significant result in favour of single visit compared to multivisits using calcium hydroxide medicament for the outcome ‘radiographic evidence of normal periodontal ligament space (strict criteria)’ was established with a moderate grade evidence. Other results such as the use of different concentrations of NaOCl (1% versus 5%) or the use of chlorhexidine 2% vs NaOCl and EDTA showed no significant difference in terms of clinical and patient related outcomes. No meta-analysis could be performed for these results due to the limited number of studies, the heterogeneity of protocols and specific outcomes. The authors acknowledge the scarcity of evidence available to evaluate the role of a specific step in endodontic treatment which is complex and which success depends on multiple factors. They also acknowledge the limited number of studies included and the weight of a single study impacting on the results of the meta-analysis. This systematic review is part of a series of high-quality systematic review designed to inform guidelines for the European Society of Endodontics. The lack of standardized studies with reproducible outcomes required to establish statements based on evidence was highlighted. Therefore, further high-quality studies with standardized outcomes are required (El Karim et al, 2022).


Primary paper

Rossi-Fedele G, Rödig T. Effectiveness of root canal irrigation and dressing for the treatment of apical periodontitis: A systematic review and meta-analysis of clinical trials. Int Endod J. 2022 May 17. doi: 10.1111/iej.13777. Epub ahead of print. PMID: 35579074.

Review protocol on PROSPERO

Other references

Nair PN. Pathogenesis of apical periodontitis and the causes of endodontic failures. Crit Rev Oral Biol Med. 2004 Nov 1;15(6):348-81. doi: 10.1177/154411130401500604. PMID: 15574679.

Weiger R, Rosendahl R, Löst C. Influence of calcium hydroxide intracanal dressings on the prognosis of teeth with endodontically induced periapical lesions. Int Endod J. 2000 May;33(3):219-26. doi: 10.1046/j.1365-2591.1999.00298.x. PMID: 11307438.

Peters LB, Wesselink PR. Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms. Int Endod J. 2002 Aug;35(8):660-7. doi: 10.1046/j.1365-2591.2002.00541.x. PMID: 12196219.

Paredes-Vieyra J, Enriquez FJ. Success rate of single- versus two-visit root canal treatment of teeth with apical periodontitis: a randomized controlled trial. J Endod. 2012 Sep;38(9):1164-9. doi: 10.1016/j.joen.2012.05.021. Epub 2012 Jul 26. PMID: 22892729.

El Karim I, Duncan HF, Cushley S, Nagendrababu V, Kirkevang LL, Kruse C, Chong BS, Shah PK, Lappin MJ, McLister C, Lundy FT, Clarke M. Establishing a Core Outcome Set for Endodontic Treatment modalities. Int Endod J. 2022 Jul;55(7):696-699. doi: 10.1111/iej.13749. PMID: 35692086.


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