Evaluation of postoperative pain following foraminal enlargement in asymptomatic necrotic teeth undergoing root canal treatment: a systematic review and meta-analysis

Article information

Restor Dent Endod. 2026;.e40

Publication date (electronic) : 2026 August 11

doi : https://doi.org/10.5395/rde.2026.51.e40

Mohammad Sabeti^1,, Seyed Mohammadreza Masoumi², Rachel Li³, Mohammad Hosein Amirzade-Iranaq⁴

¹Doctor of Dental Surgery (DDS) Program, UCSF School of Dentistry, San Francisco, CA, USA

²Doctor of Dental Surgery (DDS) Program, UCLA School of Dentistry, University of California, Los Angeles, CA, USA

³Doctor of Dental Surgery (DDS) Program, UCLA School of Dentistry, University of California, Los Angeles, Los Angeles, CA, USA

⁴Department of Oral and Maxillofacial Medicine, Postgraduate Resident of Oral Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

^*Correspondence to Mohammad Sabeti, DDS, MA Doctor of Dental Surgery (DDS) Program, UCSF School of Dentistry, 707 Parnassus Ave. Room-D 3226, San Francisco, CA 94143-0758, USA Email: Mike.sabeti@ucsf.edu

Citation : Sabeti M, Masoumi SM, Li R, Amirzade-Iranaq MH. Evaluation of postoperative pain following foraminal enlargement in asymptomatic necrotic teeth undergoing root canal treatment: a systematic review and meta-analysis. Restor Dent Endod 2026;51(4):e40.

Received 2025 November 13; Revised 2026 February 27; Accepted 2026 March 11.

Abstract

INTRODUCTION

The success of root canal treatment is critically dependent on the effective management of the apical third of the root canal system. This region exhibits a complex and often unpredictable anatomy, characterized by a high density of lateral canals and isthmi, which complicates cleaning and disinfection [1–4]. The tenacity of microbial biofilms within this intricate anatomy, particularly near the apical foramen, presents a persistent challenge to achieving complete bacterial elimination [5,6]. Inadequate debridement of this critical zone can leave behind residual bacteria and their byproducts, which are a primary etiology for the failure of endodontic therapy [7,8]. Indeed, the persistence of microorganisms within the apical 2–3 mm of the root canal is a well-established factor in the development of periradicular pathology [7].

To overcome these challenges, foraminal enlargement (FE) has been proposed as a technique to enhance disinfection by mechanically enlarging the apical foramen [9,10]. The rationale is that this creates more favorable conditions for periapical tissue healing by improving the efficacy of irrigants and intracanal medications [9,10]. This is supported by evidence suggesting that root canal treatment outcomes are significantly improved when the master apical preparation size is 30 or greater [11]. Furthermore, FE is considered an effective disinfection strategy that does not typically induce significant postoperative symptoms [12]. However, this technique is not without controversy, as other evidence indicates that FE may increase the risk of procedural errors such as overinstrumentation, as well as the extrusion of debris and sealer, potentially leading to a higher incidence of postoperative pain and swelling [13,14].

Postoperative pain remains one of the most common complications following endodontic treatment, with a reported incidence of 25%–40% [15,16]. Its severity can range from mild discomfort to debilitating pain and is strongly associated with delayed healing, patient dissatisfaction, and the potential need for further intervention [15,16]. This pain often serves as a clinical indicator of underlying complications, including tissue trauma from overinstrumentation. Consequently, the use of prophylactic analgesia is frequently recommended to mitigate postoperative pain and optimize overall treatment outcomes [15,16].

Previous systematic reviews investigating postoperative pain following FE have been limited by substantial clinical and methodological heterogeneity [17,18]. These reviews combined studies with different pulpal and periapical diagnoses, varying treatment protocols, and both single- and multi-visit approaches, which fundamentally limits the interpretability of pooled results. Postoperative pain after nonsurgical root canal treatment (NSRCT) is strongly influenced by baseline inflammatory status and procedural variables [19]. Teeth with preoperative symptoms exhibit elevated inflammatory activity that independently increases postoperative discomfort, potentially obscuring the specific contribution of apical instrumentation procedures [19]. Likewise, multi-visit treatment protocols introduce additional confounding factors [20], including intracanal medicaments and temporary restorations [21], which may affect periapical tissues and postoperative pain outcomes.

To minimize these sources of heterogeneity and isolate the specific effect of FE, the present review was deliberately restricted to asymptomatic necrotic mature teeth treated with a single-visit NSRCT protocol. By focusing exclusively on methodologically homogeneous randomized controlled trials (RCTs), this study aims to provide a more precise evaluation of the association between FE and postoperative pain.

METHODS

The conduct and reporting of this systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [22]. The review protocol was prospectively registered with PROSPERO (International Prospective Register of Systematic Reviews) under registration number (CRD420250652786). As this study is a systematic review of published randomized clinical trials and does not involve direct interaction with human participants, institutional review board approval and informed consent were not required.

Information sources and search strategy

A comprehensive search strategy was developed in collaboration with a systematic review librarian. The search utilized a combination of keywords and equivalent MeSH (Medical Subject Headings) terms (Table 1) to interrogate four major electronic databases from inception until May 20, 2025: MEDLINE via PubMed, Web of Science, Embase, and the Cochrane Central Register of Controlled Trials. To mitigate publication bias, gray literature was searched via Google Scholar (screening the first 100 results) and ProQuest Dissertations & Theses Global. Additionally, a manual search of reference lists from relevant articles and book chapters was performed.

Table 1.

Search strategy

RESULTS

Study selection

The systematic literature search and selection process are detailed in the PRISMA flow diagram (Figure 1). Initial database searches yielded 2,644 records. After the removal of 1,225 duplicates, 1,419 records underwent title and abstract screening, resulting in the exclusion of 1,393 records. Twenty-six full-text reports were sought for retrieval, and none were unavailable. All 26 reports were assessed for eligibility, of which 20 were excluded. Six studies [16,24–28] ultimately met the predefined inclusion criteria and were included in the qualitative and quantitative syntheses (Table 2). The reasons for full-text exclusion are presented in Table 3 [12,13,29–41].

Figure 1.

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow diagram illustrating the selection process of studies and results of the literature search for inclusion in the qualitative and quantitative analysis.

Table 2.

Characteristics of the included studies

Table 3.

Excluded studies with the reason for study exclusion from the review

Risk of bias in studies

The overall risk of bias for each study was determined based on the judgments across all domains. The results of the risk of bias assessment are presented in Figure 2.

Figure 2.

Risk of bias assessment of included randomized controlled trials (RoB 2).

Results of syntheses

A meta-analysis was performed incorporating all six studies (pooled n = 426 teeth) [16,24–28]. The overall pooled analysis across all postoperative timepoints demonstrated a statistically significant increase in postoperative pain in the FE group compared to the control group (SMD, 1.02; 95% CI, 0.24–1.80; p = 0.01) (Figure 3). The certainty of this evidence was graded as low (Table 4), although considerable statistical heterogeneity was observed (I² = 92.3%).

Figure 3.

Overall forest plot. It shows the mean visual analogue scale scores measured at various time intervals (12, 24, 48, 72, 168 hours [1 week]). Squares and horizontal lines represent the standardized mean difference (SMD) and 95% confidence interval (CI). The square areas correspond to the weight of each study included. SD, standard deviation.

Table 4.

Summary of findings and GRADE certainty of evidence

Subgroup analyses were conducted based on postoperative follow-up intervals (12, 24, 48, 72, and 168 hours). A test for subgroup differences was not statistically significant (χ² = 5.22, df = 4, p = 0.27), indicating that the effect of FE on pain was consistent across timepoints. The overall effect remained statistically significant in both common-effect (SMD, 0.55; 95% CI, 0.43–0.66) and random-effects models (SMD, 1.02; 95% CI, 0.24–1.80).

The specific results for each time point, calculated using a random-effects model, were as follows:

• 12 hours (two studies, n = 111): SMD, 0.46 (95% CI, 0.08 to 0.84; p = 0.02), I² = 0%

• 24 hours (six studies, n = 426): SMD, 1.23 (95% CI, –0.03 to 2.50; p = 0.06), I² = 96%

• 48 hours (four studies, n = 341): SMD, 2.68 (95% CI, –0.94 to 6.31; p = 0.15), I² = 97.8%

• 72 hours (five studies, n = 286): SMD, 0.36 (95% CI, 0.13 to 0.60; p = 0.002), I² = 10.1%

• 1 week (168 hours) (three studies, n = 186): SMD, 0.18 (95% CI, –0.11 to 0.46; p = 0.23), I² = 0%

Exploration of heterogeneity and publication bias

Considerable statistical heterogeneity was identified, particularly within the 24-hour (I² = 96%) and 48-hour (I² = 97.8%) subgroups. Assessment of publication bias using a funnel plot revealed mild asymmetry (Figure 4), although this finding was interpreted cautiously because of the small number of included studies. The Baujat plot identified two studies that contributed disproportionately to the overall heterogeneity and influence on the pooled estimate (Figure 5).

Figure 4.

Funnel plot with 95% confidence intervals for the publication bias assessment.

Figure 5.

Baujat plot showing the contribution of individual studies to overall heterogeneity and their influence on the pooled effect estimate.

Sensitivity analysis

A leave-one-out sensitivity analysis (Figure 6) confirmed that the exclusion of the identified outlier studies substantially reduced the overall heterogeneity (as indicated by reductions in I² and τ²) without changing the direction or statistical significance of the pooled effect, confirming the robustness of the primary finding (Figures 7 and 8).

Figure 6.

Leave-one-out sensitivity analysis showing the standardized mean difference (SMD), 95% confidence intervals (CI), and heterogeneity (I²) after sequential omission of individual studies across all measured time intervals.

Figure 7.

Sensitivity analysis (excluding Yaylali et al. [16] and Gandhe et al. [28]). This forest plot illustrates the mean visual analogue scale scores at various time intervals (12, 24, 48, 72, 168 hours [1 week]) after the exclusion of the studies by Yaylali et al. [16] and Gandhe et al. [28]. Squares and horizontal lines represent the standardized mean difference (SMD) and 95% confidence intervals (CI), respectively. The area of each square corresponds to the weight of each included study. SD, standard deviation.

Figure 8.

Funnel plot showing publication bias assessment after excluding Yaylali et al. [16] and Gandhe et al. [28], with 95% confidence intervals.

DISCUSSION

This systematic review and meta-analysis, incorporating data from six RCTs [16,24–28], provides evidence that FE during single-visit NSRCT of asymptomatic necrotic teeth is associated with a statistically significant increase in patient-perceived postoperative pain. The overall pooled analysis demonstrated a significant effect (SMD, 1.02; 95% CI, 0.24–1.80; p = 0.01), indicating that the procedural decision to instrument the apical foramen has a tangible impact on postoperative symptoms. The temporal pattern of this pain is critical: peak levels were consistently observed within the first 48 hours, with a sharp decline thereafter and no reports of severe pain persisting beyond one week.

A principal finding of this review is the considerable statistical heterogeneity (I² = 92.3%) present in the initial analysis. This heterogeneity is not merely a statistical concern but reflects underlying clinical and methodological diversity. The sensitivity analysis, a cornerstone of robust meta-analytic methodology, identified two studies as outliers whose exclusion substantially reduced heterogeneity without altering the direction or significance of the primary finding [16,28]. This reinforces the conclusion that the association between FE and increased pain is a robust phenomenon, not solely dependent on specific outlier results.

The funnel plot asymmetry observed prior to this exclusion was interpreted with caution due to the limited number of studies, a known limitation in tests for publication bias. The non-significant result of Pustejovsky’s regression test (p = 0.9078) provides statistical support for the absence of significant publication bias in the final analyzed cohort, increasing confidence in the validity of the pooled estimate.

Our findings diverge from those of two prior systematic reviews on this topic [17,18]. A critical examination reveals that this divergence likely stems from fundamental differences in methodological rigor and inclusion criteria.

Fatima et al. [17] included studies with significant methodological inconsistencies, such as Machado et al. [29], which involved teeth with preexisting access cavities and groups that performed instrumentation 0.5 mm beyond the foramen (intentional FE, IFE). IFE is a distinct, more aggressive intervention that directly manipulates periapical tissues and is associated with high rates of sealer extrusion, a known irritant [29]. Furthermore, both Fatima et al. [17] and Borges Silva et al. [18] included Saini et al. [12], which utilized a two-visit protocol with intracanal medication. The inclusion of multi-visit treatments introduces a major confounding variable, as the medication itself can influence postoperative symptoms. For this reason, the present review was deliberately restricted to single-visit NSRCT to isolate the specific effect of FE on postoperative pain.

Borges Silva et al. [18] further included Morse et al. [30], a study involving patients with systemic diseases who received postoperative antibiotics. Both factors are potential confounders for perceived pain, complicating the isolation of the effect attributable solely to FE.

Crucially, neither prior review conducted sensitivity analyses to explore the impact of this pronounced heterogeneity on their findings. By employing strict, homogenous inclusion criteria limited to single-visit NSRCT in otherwise healthy patients with working lengths set at 0.0 mm, and by performing comprehensive sensitivity analyses, our review provides a more precise and reliable estimate of the specific effect of FE on postoperative pain.

The outlier status of Yaylali et al. [16] and Gandhe et al. [28] warrants specific discussion, as it elucidates factors that may exacerbate postoperative pain.

Yaylali et al. [16] reported a markedly higher incidence of severe pain (34% at 24 hours) compared to other included studies. A plausible explanation is their exclusive focus on molar teeth. The complex anatomy of molars, including accessory canals, isthmi, and challenging access, can lead to more prolonged and traumatic procedures, which are independently associated with higher postoperative pain [42]. Interestingly, the lack of a significant difference in analgesic use between their groups suggests that the underlying pain stimulus (the molar procedure) was potent in both FE and control groups, but the FE intervention may have intensified it.

Regarding potential sex-based bias, while Cruz Junior et al. [25] exclusively enrolled female participants citing lower pain thresholds, contemporary evidence indicates that VAS scores do not consistently differ by gender [43,44]. Therefore, this design choice is unlikely to have significantly biased the overall results of our synthesis.

Analgesic consumption is a critical confounder in pain studies. In this review, three included studies reported either no statistically significant difference in analgesic consumption between groups (p > 0.05) or only small absolute differences in the proportion of patients requiring medication, which were unlikely to be clinically meaningful [16,24,25]. In the study by Yaylali et al. [16], 26% of patients in the FE group and 17% in the control group used ibuprofen during the first two postoperative days, with no significant difference between groups. Similarly, Silva et al. [24] reported no cases of severe pain and no group differences in analgesic use at any time point. Cruz Junior et al. [25] observed analgesic intake in only two patients (8.7%) in the FE group and none in the control group at 24 hours, with no statistically significant difference; no medication was required after 72 hours in either group. These findings are consistent with an earlier clinical trial [12], which likewise found that FE did not significantly influence postoperative analgesic consumption.

The finding of increased pain with FE is biologically plausible. The apical foramen represents a physiological constriction, and its intentional enlargement inherently causes additional mechanical and chemical irritation to the periapical tissues. Overinstrumentation, even when controlled to 0.0 mm, can generate microcracks in the radicular dentin and directly traumatize the periodontal ligament, initiating an inflammatory response [45]. In addition, the loss of the natural apical constriction increases the risk of extruding irrigants (e.g., NaOCl), debris, and sealer into the periapical space [46]. While most studies in this review used consistent irrigation protocols, the choice of sealer and obturation technique varied (e.g., AH Plus [Dentsply Sirona, Ballaigues, Switzerland] vs. EWT sealer [Kerr Corporation, Orange, CA, USA]; single-cone vs. warm condensation), which could contribute to unexplained heterogeneity in the pain response. These extruded materials act as foreign-body irritants, provoking and sustaining inflammation that manifests clinically as pain.

The strength of this review lies in the stringent methodology employed to enhance internal validity. By excluding patients with preoperative pain, retreated teeth, multi-visit treatments, and those with systemic diseases, we minimized major confounding variables. Preoperative pain obscures the origin of postoperative symptoms [47], retreatment cases present preexisting complications and altered microflora [48], and multi-visit protocols introduce the confounding effect of intracanal medicaments. Furthermore, by strictly defining FE as instrumentation to 0.0 mm (as verified by an EAL) and excluding studies that instrumented beyond the foramen [29,31], we isolated the effect of FE from the more traumatic intentional foraminal overinstrumentation.

The consistent use of the VAS across all included studies strengthens the comparability of the outcome data. The VAS is a validated, sensitive tool for quantifying subjective pain experience, and its uniform application provides confidence that the measured effects are real and not an artifact of inconsistent assessment methods [46].

Several limitations of this study should be considered. First, the VAS is subjective and may introduce variability in pain reporting that is unrelated to the procedural intervention [49]. Second, although analgesic use was generally comparable between groups, it may have partially masked pain intensity and led to underestimation of the true effect of FE. Third, because this review included only single-visit NSRCT of asymptomatic necrotic teeth, the findings may not be generalizable to multi-visit treatments or symptomatic cases with different inflammatory conditions. Fourth, the small number of included studies reduces the precision of pooled estimates and limits the reliability of subgroup and publication bias analyses. Fifth, the lack of consistent differentiation based on periapical radiolucency may have introduced unmeasured confounding, as baseline periapical inflammation can influence postoperative pain. Finally, variations in instrumentation systems, sealers, and obturation techniques may have contributed to residual heterogeneity by affecting the degree of periapical irritation. Future studies should incorporate standardized protocols, stratification by periapical status, objective inflammatory markers, and longer follow-up periods.

CONCLUSIONS

In conclusion, this systematic review and meta-analysis demonstrates that FE during single-visit NSRCT of asymptomatic necrotic teeth is associated with a significant, though transient, increase in postoperative pain, predominantly within the first 72 hours. This finding provides clinicians with critical evidence-based insight for clinical decision-making. The benefits of FE, such as potential enhancements in apical debridement and disinfection, must be carefully weighed against the predictable outcome of increased patient discomfort in the immediate postoperative period following single-visit NSRCT. Therefore, when FE is deemed necessary to address complex apical anatomy or persistent infection, its application should be selective and accompanied by proactive strategies for pain management, including patient pre-warning and the prudent prescription of analgesics.

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