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Associated Topics

Initial assessment of endodontic flare-up frequency after root canal therapy

Elias M Chatah DDS, B. Pharm. .


Systematic Review Conclusion

The authors concluded that the average incidence of endodontic flare-ups for 982 patients was 8.4 percent.

Critical Summary Assessment

A poor meta-analysis of limited evidence from six prospective case series suggest that on average 8.4 percent of patients experience pain from endodontic flare-ups within 48 hours following the initiation or continuation of root canal therapy. Large cohort studies are needed to confirm these findings.

Evidence Quality Rating

Limited Evidence

Structured Abstract

Clinical Questions:

In patients undergoing initial or continuation of root canal therapy, what is the frequency of endodontic flare-ups and factors affecting flare-ups?

Review Methods:

The reviewers searched one electronic database (MEDLINE) for articles published in English from 1966 to May 2007. The search yielded six prospective case series deemed eligible according to the inclusion and exclusion criteria. The reviewers included randomized control trials and prospective case series that presented a detailed diagnosis of the pulp and periapical region and that define flare-up as strong pain (assessed exclusively with VAS), with or without swelling occurring within 24 or 48 hours following endodontic treatment. Patients must have not received any medicinal therapy before or after endodontic treatment. The reviewers excluded articles with a different definition of flare-up than that of the reviewers, those lacking information on pain level evaluation timing or where pain evaluation was not within 24-48 hours after endodontic treatment, and the following publication types: retrospective studies, case reports, review articles, and expert opinion. The reviewers resolved any disagreement with discussion. The frequency of endodontic flare-ups was quantified by calculating a weighted average of flare-up incidence. Statistical heterogeneity was assessed using a standard chi-squared test of Q-statistic.

Main Results:

The reviewers included six studies, three of which focused on asymptomatic maxillary central incisors with pulp necrosis. One study included all types of teeth. Two studies included all teeth with partial necrosis and apical periodontitis, one of which also included previous root canal treatment. The average percentage of flare-ups for 982 patients was 8.4 standard deviation (SD) = 57. The six studies were heterogeneous. The reviewers were unable to investigate factors that influence flare-ups such as gender, number of appointments, or pulp status.


The reviewers estimated the frequency of endodontic flare-ups in adults manifesting as strong pain with or without facial swelling 48 hours following initial or continued root canal treatment to be 8.4 percent. The reviewers judged that the data from this meta-analysis was insufficient for investigating factors that influence flare-ups.

Source of Funding:

No sources of funding for this review were listed or discussed.


Importance and Context:

Although not well understood or defined, endodontic flare-ups are thought to involve local tissue changes and factors relating to microbes, procedures and pharmacology, and the patient's immune status. In addition to having a negative impact on patients' overall well-being, endodontic flare-up pain is disruptive to both patients and their clinicians and may negatively impact the productivity of both parties due to the urgent need for intervention. The literature has reported the cumulative incidence of flare-ups in a range from 1.58 to 15.7 percent [1, 2]. Effective management of endodontic flare-up pain requires an understanding of its etiology and frequency of occurrence, an important aspect of which is educating patients on the importance of compliance with post-op instructions and care.

Strengths and Weaknesses of the Systematic Review:

Although the reviewers defined flare-ups, they failed to include aspects such as whether or not the flare-ups were transient or needing retreatment, were observed radiographically, or were due to an infection or a post-op trauma. These oversights limit the clinical relevance of the results. Two reviewers independently reviewed the articles and resolved disagreements with discussions. They clearly described their search strategy, but it was limited to literature in English. In addition, they searched only one database and did not hand search or review grey literature. They clearly defined inclusion and exclusion criteria; however, it is unclear if these criteria were pre-specified. The authors did not follow their own inclusion/exclusion criteria, as three studies included asymptomatic teeth while the authors’ definition of a flare up clearly stated the presence of "pain." The reviewers did not assess study quality, and they did not seek expert opinion or contact with authors.

Strengths and Weaknesses of the Evidence:

Six prospective case series with 982 patients comprises the totality of the evidence. Prospective case series studies are uncontrolled and subject to selection and observer bias. Evidence from this type of study is weaker than that from a controlled study. Searching and including non-English literature would possibly have increased the number of eligible studies and therefore potentially the level of the evidence. Also, the studies used a visual analog scale to assess pain, which is inadequate to define flare-ups as it does not address swelling.

Implications for Dental Practice:

To identify patients “at risk” for flare-ups, the clinician needs to understand their etiology, the patient's presenting condition, and the state of the peri-apical tissue at presentation; however, this meta-analysis produced limited evidence to aid the clinician in this decision making. Well-designed randomized controlled trials or cohort and prospective studies are needed to produce more reliable data to improve the level of evidence on this topic. If a clinician is seeing a disproportionately large incidence of flare-ups relative to endodontic emergencies, his/her diagnosis and treatment approach should be reevaluated. References: [1]. Imura N, Zuolo ML - Factors associated with endodontic flare-ups: a prospective study. Int Endod J. 1996 Nov. 29 (6): 382-6. [2]. Harrison JW, Baumgartner JC, Svec TA. – Incidence of pain associated with clinical factors during and after root canal therapy. Part 1. Inter-appointment pain. J Endod. 1983 Sep. 9(9):384-7

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2018