The effect of foraminal enlargement and irrigant activation technique on post-operative pain in necrotic teeth - a clinical study

Abstract

Background/objectives

Post-endodontic pain remains a significant clinical challenge, impacting patient quality of life despite meticulous treatment. Its multifactorial origins include procedural factors such as foraminal enlargement and irrigation techniques, as well as patient-specific variables. While advanced irrigation activation methods like passive ultrasonic irrigation (PUI) and the XP-Endo Finisher have been shown to improve canal disinfection, their effects on postoperative pain are not fully established. We aim to compare the influence of foraminal enlargement combined with different activation methods ultrasonic and XP-Endo Finisher on postoperative pain levels in necrotic, single-rooted teeth, to identify approaches that optimize patient comfort.

Methods

We conducted a randomized, single-blind, four-arm clinical trial involving 60 patients with necrotic, asymptomatic single-rooted teeth exhibiting periapical lesions. Participants were randomly assigned to four groups: (1) foraminal enlargement with passive ultrasonic irrigation, (2) foraminal enlargement with XP-Endo Finisher activation, (3) no foraminal enlargement with passive ultrasonic irrigation, and (4) no foraminal enlargement with XP-Endo Finisher activation. Standardized root canal preparation, irrigation protocols, and obturation techniques were employed across all groups. Postoperative pain was self-recorded by patients using a visual analog scale (VAS) at 8 h, 24 h, 48 h, 3 days, and 1 week post-treatment. Data were analyzed using non-parametric statistical tests to compare pain levels among groups.

Results

Analysis revealed no statistically significant differences in postoperative pain levels between the four groups at any assessed time point. Pain peaked within the first 8 h and gradually decreased over the week across all groups. The mean pain scores showed similar temporal patterns regardless of foraminal enlargement or activation technique used. The overall trend indicated that neither foraminal enlargement nor the specific irrigation activation methods significantly influenced postoperative discomfort in the studied sample.

Conclusions

Our findings suggest that, in single-rooted necrotic teeth with periapical lesions, foraminal enlargement and the application of advanced irrigation activation techniques passive ultrasonic and XP-Endo Finisher do not significantly affect postoperative pain levels. These procedures can be incorporated into endodontic protocols without increasing patient discomfort when performed within standardized guidelines. The results underscore the importance of proper technique and disinfection strategies in achieving effective treatment outcomes while maintaining patient comfort. Further research with larger, more diverse populations and extended follow-up is warranted to confirm these findings and explore long-term effects.

Trial registration

The trial was registered on February 6, 2020, under the number (UDDS-284-21012020/SRC-1450).

Introduction

Post-endodontic pain represents a significant challenge that adversely affects patients’ quality of life, even when endodontic treatments are performed with the utmost care and precision [1]. This complication is not uncommon, with studies indicating that the incidence of post-operative pain can vary widely, affecting approximately 25% to 40% of patients, regardless of whether the pulp is vital or necrotic [2].

The origins of post-operative pain can be multifaceted, stemming from mechanical injuries such as over-instrumentation and overfilling, chemical injuries from the extrusion of irrigants, dressings, and filling materials, as well as microbiological factors including the extrusion of contaminated debris beyond the apex, shifts in microbial virulence, and secondary intraradicular infections. These factors can lead to damage to the periapical tissues, contributing to the overall discomfort experienced by patients [3, 4]. Furthermore, pre-operative factors such as the presence of pain before treatment, patient demographics (gender and age), psychological factors (anxiety), the type of tooth being treated, pulp vitality, and the existence and size of periapical lesions also play a significant role in post-operative pain outcomes [5, 6]. The persistence of residual bacteria within the root canal system may further exacerbate inflammation and discomfort [7].

To achieve successful root canal therapy, effective chemical and mechanical preparation is essential, which includes the use of antibacterial irrigants, their activation, and the appropriate selection of endodontic instruments [8]. Accurately determining the working length is critical, as deviations whether over- or under-instrumentation can lead to complications such as post-operative pain and microbial persistence. Traditionally, the ideal working length is established at the apical constriction, typically located about 1 mm short of the apex [9]. However, the presence of microorganisms within the cemental portion of the canal and their potential role in the development of periapical lesions may require mechanical cleaning that extends to or beyond the apical foramen, thereby reducing the microbial load at the most apical end of the root canal [10]. Research has shown that bacteria can be found at the apical foramen, with some colonies extending into the periapical region, highlighting the importance of thorough disinfection [11]. If these microorganisms are not effectively eliminated, they may survive due to a continuous supply of nutrients from the surrounding periapical tissues. Therefore, the cleaning and shaping of the apical foramen are crucial for adequate disinfection and fostering a conducive environment for periapical healing [12].

Foraminal enlargement, defined as the deliberate mechanical widening of the apical foramen, aims to reduce the microbial load by removing infected cementum and dentin [13]. However, this procedure may induce pain due to direct mechanical irritation of the periapical tissues or the extrusion of debris during preparation [14]. Such complications can lead to patient discomfort and heightened post-operative pain, as research indicates that disrupting the apical constriction can result in significant apical debris extrusion [15]. Conversely, some studies suggest that apical foramen enlargement may facilitate cleaning of the apical region without exacerbating post-operative pain [3]. Thus, the potential for pain arising from periapical tissue injury during foraminal enlargement remains a contentious issue [16].

Traditional syringe irrigation techniques often fall short in effectively delivering irrigants to unprepared or anatomically complex areas [17]. In response, various irrigation activation systems have been developed to enhance the efficacy of irrigation [18]. Among these, passive ultrasonic irrigation (PUI) has emerged as a widely utilized technique, demonstrating improved removal of pulp tissue and dentin debris, as well as superior bacterial elimination compared to conventional irrigation methods. PUI is particularly effective in cleaning curved canals and isthmuses [19]. This technique operates by transmitting acoustic energy from an oscillating file or smooth wire into the irrigant, generating acoustic streaming that agitates and dislodges biofilm and induces cavitation within the irrigant [20]. This dynamic movement allows for more comprehensive distribution of the irrigant throughout the canal system [21]. Additionally, some of the kinetic energy generated during this process is converted into heat, potentially accelerating chemical reactions [22]. PUI can be applied in either continuous or intermittent modes [23].

Furthermore, the XP-Endo Finisher file is employed to enhance the effectiveness of final irrigation [24]. This non-tapered file, made from NiTi MaxWire alloy, is temperature-sensitive, maintaining a straight shape at lower temperatures (M-phase) and transforming into an expanded configuration at body temperature (A-phase) [25]. This unique adaptability enables the file to expand and contract, reaching equivalent canal volumes and effectively removing debris and bacteria from irregular canal areas [26, 27]. It excels at eliminating compacted hard tissue debris and the smear layer while preserving dentin integrity, as it contacts and scrapes the canal walls without altering the original canal shape [28, 29].

Several randomized clinical studies have indicated that employing irrigation activation methods can lead to a reduction in post-operative pain [30, 31]. However, it has also been reported that these methods may result in the extrusion of debris and irrigants into the periapical tissues, potentially causing irritation and subsequent post-operative pain [32, 33].

In this research, we aim to compare the effects of different activation methods ultrasonic and XP-Endo Finisher along with the implications of foraminal enlargement on post-operative pain in necrotic teeth. Our study seeks to identify the most comfortable approach for patients undergoing root canal treatment. The novelty of this research lies in its comprehensive examination of the interplay between irrigation activation techniques and foraminal enlargement, specifically focusing on their combined effects on post-operative pain in asymptomatic necrotic teeth with periapical lesions. By addressing these factors, we hope to contribute valuable insights into optimizing endodontic treatment protocols and enhancing patient comfort.

Materials and methods

Study design and ethical approval

This study was conducted as a randomized, single-blind, four-arm, parallel-group clinical trial with an equal allocation ratio of 1:1:1:1. The research protocol was reviewed and approved by the Biomedical Research Ethics Board at Damascus University. The study adhered to established ethical standards for clinical research, ensuring participant safety and confidentiality. All participants provided written informed consent prior to enrollment, in accordance with ethical guidelines.

Sample size determination

The sample size was calculated based on prior similar investigations [34], utilizing G*Power software version 3.1.9.7 (Heinrich-Heine-Universität, Düsseldorf, Germany), based on a medium effect size (d = 0.5). Setting the significance level (α) at 0.05 and aiming for a statistical power of 80%, to detect differences in postoperative pain levels measured by VAS. Prior studies indicated a mean difference of at least 1.0 cm on the VAS scale as clinically significant. It was determined that a minimum of 15 teeth per group would be necessary to detect meaningful differences in postoperative pain levels. To account for potential dropouts, we increased the sample to 15 per group, totaling 60 participants. To account for potential dropouts and attrition, the sample size was slightly increased. Nonetheless, the current sample size remains relatively small, which may limit the statistical robustness and generalizability of the findings.

Participant selection and inclusion/exclusion criteria

A total of 60 patients presenting with periapical lesions at the Department of Endodontics, Faculty of Dentistry, Damascus University, were initially examined. Inclusion criteria were as follows: healthy individuals aged between 20 and 45 years of both sexes; presence of a permanent, fully developed, single-rooted tooth with a single canal, untreated, and suitable for single-visit endodontic therapy; teeth capable of rubber dam isolation; necrotic pulp tissue accompanied by asymptomatic apical periodontitis and medium-sized periapical radiolucencies (3–5 mm); straight or slightly curved canals; and normal periodontal sulcus depth. Patients were required not to have taken antibiotics within ten days prior to treatment.

Exclusion criteria encompassed uncooperative patients or those declining participation, systemic diseases, pregnancy, presence of edema, pus, or severe pain, prior endodontic treatment, teeth with open or immature roots, fractures or cracks, internal or external resorption, calcified or obstructed canals hindering working length determination, apical diameters outside ISO sizes 10–20, or complex root anatomies. These criteria aimed to select a homogenous sample and minimize confounding factors.

Randomization and blinding

Participants were randomly allocated into one of four treatment groups using a computer-generated randomization sequence employing block randomization to ensure balanced group sizes. Allocation concealment was maintained with opaque, sealed envelopes, numbered sequentially according to the order of enrollment; these were opened at the time of treatment. Due to the nature of the procedures, operator blinding was not feasible, as the clinician was aware of the activation technique employed. Patient blinding was also impractical because of perceptible differences between irrigation activation methods. To mitigate assessment bias, the outcome assessor was blinded to group allocation.

Operator calibration and standardization

Prior to the study, the operator underwent calibration sessions to standardize techniques and ensure procedural consistency. Training included canal preparation, irrigation protocols, activation methods, and obturation procedures. Calibration was validated through practice on extracted teeth, achieving acceptable intra-operator consistency, thereby enhancing reliability.

Clinical procedure

Following informed consent, patients underwent clinical and radiographic examinations. Preoperative rinsing with 0.12% chlorhexidine gluconate was performed. Under local anesthesia and rubber dam isolation, access cavities were prepared using sterile diamond and endo-Z burs. Pulp chamber patency was confirmed with sterile #10, #15, or #20 K-files (Mani, Japan) inserted 2 mm short of the apparent working length, which was determined radiographically.

Working length was established via electronic apex locator (Root ZX II, J Morita, Japan) and confirmed with periapical radiographs. For canals designated for foraminal enlargement, the working length was set at the apex locator reading of 0.0; for non-enlargement groups, it was set 1 mm short of this reading.

Canal preparation

Initial manual preparation involved K-files (Mani, Japan) to the predetermined working length, with the Master Apical File (MAF) identified through tactile and radiographic confirmation. Mechanical preparation employed the ProTaper Next rotary system (DENTSPLY, USA) at 300 rpm and 2 N/cm torque, starting with an X1 (17/0.04) file, then X2 (25/0.06), and X3 (30/0.07) until reaching the full working length, confirmed radiographically.

Irrigation protocol

A standardized irrigation protocol was applied across all groups, with a total volume of 30 mL per tooth. During instrumentation, 2 mL of 5.25% sodium hypochlorite (ShahbaMed, Syria) was delivered between each file using a side-vented 30-gauge needle inserted 2 mm short of the working length. Gentle in-and-out movements prevented periapical extrusion. After every three file insertions, a 20-second activation was performed, followed by a saline rinse.

The final irrigation sequence included:

• 2 mL of sodium hypochlorite for 30 s,

• Saline rinse,

• 2 mL of 17% EDTA (MetaBiomed, Korea) for 30 s,

• Saline rinse,

• 2 mL of sodium hypochlorite for 30 s.

The total irrigant volume was maintained at 30 mL for consistency.

Activation of irrigation

Participants were assigned to two main activation groups:

• Ultrasonic Activation Group:

  • Irrigation was activated using a U-File (Woodpecker, China) attached to an ultrasonic device (Woodpecker, China). The ultrasonic tip was inserted 2 mm short of the working length, performing gentle in-and-out movements without contacting canal walls, for three cycles of 20 s each. Saline rinses were interspersed between cycles.
• XP-Endo Finisher Activation Group:

  • A 25# XP-Endo Finisher file (FKG Dentaire, Switzerland) was inserted 2 mm into the canal and operated at 800 rpm with 1 N/cm torque, following manufacturer instructions. The file was moved slowly around the canal circumference for 7–8 mm in an apico-coronal direction, then withdrawn with rotation. Activation involved three cycles of 20 s each, with 2 mL of sodium hypochlorite per cycle and intermittent saline rinses.

Obturation and restoration

Post-irrigation, canals were dried with sterile paper points. Gutta-percha cones (MetaBiomed, Korea) matching the last file size were fitted and confirmed radiographically. Canal obturation was performed using the single-cone technique with CeraSeal bioceramic sealer (MetaBiomed, Korea). Radiographic assessment confirmed obturation quality, after which the gutta-percha was cut at the orifice level. The access cavity was restored with composite resin, and the duration of obturation was recorded.

Postoperative pain assessment

Patients received instructions to record their postoperative pain using a visual analog scale (VAS), ranging from 0 (no pain) to 10 cm (worst imaginable pain). They documented pain levels at 8, 24, 48, and 72 h, and at one week post-treatment. Patients were advised that analgesics (400 mg ibuprofen) should only be taken if experiencing severe pain; only two patients (one from each of the first two groups) required medication, both on the first postoperative day. Patients were also provided with contact details for reporting emergencies.

Data analysis and statistical considerations

VAS scores were compiled and analyzed using IBM SPSS Statistics version 13.0 (SPSS Inc., Chicago, IL, USA). The distribution of data normality was assessed with the Kolmogorov–Smirnov test. Given the non-parametric nature of pain scores, the Kruskal-Wallis test was employed for comparisons among the four groups. A p-value of less than 0.05 was considered statistically significant. It is important to note that the study’s limited sample size and the variability inherent in pain assessment may impact the statistical power and the interpretation of the results. Future studies with larger samples and more comprehensive statistical analysis are recommended to strengthen the evidence. Given the multiple pain assessments over time, a repeated-measures analysis using a two-way linear mixed-effects model was conducted to evaluate the interaction between time and treatment group, accounting for within-subject correlations. The analysis revealed no significant interaction effect (p > 0.05), supporting the findings from the separate Kruskal-Wallis tests.

Results

A total of 60 human teeth (either inferior or superior), unirooted, unicanal, with complete apices, necrotic, and associated with periapical lesions, were included in this trial, involving 52 patients (29 females and 23 males; mean age ± SD: 32.1 ± 7.1 years), with 15 teeth in each group. In terms of gender distribution, the Foraminal Enlargement + passive ultrasonic irrigation activation group comprised 8 males (53.3%) and 7 females (46.7%). The Foraminal Enlargement + XP-Endo Finisher file activation group also included 8 males (53.3%) and 7 females (46.7%). The None Foraminal Enlargement + passive ultrasonic irrigation activation group had 6 males (40.0%) and 9 females (60.0%), while the None Foraminal Enlargement + XP-Endo Finisher file activation group consisted of 7 males (46.7%) and 8 females (53.3%). There were no patient withdrawals from the study; therefore, all 60 teeth were included in the data analysis (Fig. 1).

Fig. 1.

Flow chart of the study

The mean changes in pain perception after 8 h were 2.33 cm ± 1.63, 2.73 cm ± 1.91, 1.47 cm ± 1.64, and 1.73 cm ± 1.71 for the Foraminal Enlargement + passive ultrasonic irrigation activation, Foraminal Enlargement + XP-Endo Finisher file activation, None Foraminal Enlargement + passive ultrasonic irrigation activation, and None Foraminal Enlargement + XP-Endo Finisher file activation groups, respectively.

After one day, the mean changes in pain perception were 2.73 cm ± 2.15, 3.13 cm ± 2.50, 2.00 cm ± 1.89, and 2.33 cm ± 1.95 for the same groups, respectively.

After two days, the mean changes in pain perception were 1.53 cm ± 1.46, 1.80 cm ± 1.57, 1.13 cm ± 1.51, and 1.13 cm ± 1.36 for the Foraminal Enlargement + passive ultrasonic irrigation activation, Foraminal Enlargement + XP-Endo Finisher file activation, None Foraminal Enlargement + passive ultrasonic irrigation activation, and None Foraminal Enlargement + XP-Endo Finisher file activation groups, respectively.

After three days, the mean changes in pain perception were 0.60 cm ± 0.91, 0.80 cm ± 1.01, 0.40 cm ± 0.83, and 0.53 cm ± 0.99 for the same groups, respectively.

Finally, after one week, the mean changes in pain perception were 0.20 cm ± 0.56, 0.27 cm ± 0.59, 0 cm ± 0, and 0.07 cm ± 0.26 for the Foraminal Enlargement + passive ultrasonic irrigation activation, Foraminal Enlargement + XP-Endo Finisher file activation, None Foraminal Enlargement + passive ultrasonic irrigation activation, and None Foraminal Enlargement + XP-Endo Finisher file activation groups, respectively.

There were no statistically significant differences in the mean changes of pain perception after 8 houres, one day, two days, three days, and one week between the four groups, in general (Table 1). The mean difference in pain scores between groups at 8 h was 0.86 cm (95% CI: -0.45 to 2.17), Cohen’s d = 0.25, indicating a small effect size with overlapping CIs, consistent with non-significant p-values.

Table 1.

Descriptive statistics of change observed in the pain perception (N = 15)

Time	Group	Mean	SD	Min	Max	P-value	Significance
After 8 houres	G1	2.33	1.63	0	5	0.244	NS
	G2	2.73	1.91	0	7
	G3	1.47	1.64	0	5
	G4	1.73	1.71	0	5
After one day	G1	2.73	2.15	0	8	0.614	NS
	G2	3.13	2.50	0	8
	G3	2.00	1.89	0	5
	G4	2.33	1.95	0	6
After two days	G1	1.53	1.46	0	4	0.478	NS
	G2	1.80	1.57	0	5
	G3	1.13	1.51	0	4
	G4	1.13	1.36	0	4
After three days	G1	0.60	0.91	0	3	0.433	NS
	G2	0.80	1.01	0	3
	G3	0.40	0.83	0	2
	G4	0.53	0.99	0	3
After one week	G1	0.20	0.56	0	2	0.298	NS
	G2	0.27	0.59	0	2
	G3	0	0	0	0
	G4	0.07	0.26	0	1

Also, Fig. 2, and Fig. 3, we have illustrated our results in two diagrams representing the results.

Fig. 2.

Diagram of the results for mean of the pain

Fig. 3.

Diagram of the results for percentage distribution of the samples treated

In Fig. 2, we illustrate the results related to the means of pain for the time functionality. In Fig. 3, we illustrate the results for percentage distribution of the samples treated.

Discussion

The primary goal of endodontic treatment is to effectively clean, shape, and disinfect the root canal system to eradicate bacteria, residual pulp tissue, and debris, thereby promoting periapical healing [35]. Achieving an optimal seal of the filled canal is equally crucial, as it prevents recontamination and ensures a conducive environment for tissue repair [36]. Proper sealing also minimizes patient discomfort and reduces the risk of post-operative complications, emphasizing the importance of precise technique and effective obturation methods.

In cases of pulp necrosis accompanied by periapical inflammation, foraminal enlargement is widely recommended as part of the treatment protocol [13]. This procedure involves using an instrument larger than the apical constriction often reaching or surpassing the apical foramen to mechanically remove contaminated cementum and dentin, thereby reducing bacterial load more effectively [37]. The rationale behind this approach is that enlarging the apical foramen facilitates better irrigation and disinfection, especially in areas where bacteria tend to persist within complex canal anatomies or biofilms. However, this technique carries the risk of increased post-operative pain due to the potential extrusion of debris and irritants into periapical tissues [15]. The balance between adequate disinfection and minimizing tissue trauma remains a critical consideration in clinical decision-making.

Clinical studies aiming to evaluate post-operative pain face numerous challenges, notably in isolating the causative factors. Pain after endodontic procedures is multifactorial; aside from the intervention itself, variables such as the discomfort from local anesthetic injections, pressure exerted by rubber dam clamps, muscle fatigue, and temporomandibular joint strain can all contribute to the patient’s sensation of pain [38, 39]. Moreover, individual patient factors like age, gender, pre-treatment anxiety, and pain threshold significantly influence pain perception and reporting [40]. While previous research suggests these variables are often evenly distributed in randomized controlled trials, their potential to confound results cannot be entirely dismissed [41]. Therefore, interpreting post-operative pain data necessitates careful consideration of these extraneous factors.

Pain assessment remains inherently subjective, posing a significant challenge for researchers and clinicians alike. Variability in pain thresholds means that two patients with similar clinical conditions may report vastly different experiences [42, 43]. Consequently, selecting appropriate, validated, and easily comprehensible pain measurement tools is essential. The visual analogue scale (VAS) is the most commonly employed method in endodontic research due to its simplicity, reliability, and sensitivity [23, 44–46]. Nonetheless, standardization in patient instructions and consistent administration are vital to ensure data accuracy and comparability across studies.

Timing of pain evaluation is another critical aspect. Measurements at specific intervals such as 24 and 72 h are based on the understanding that post-operative pain often peaks within this window [47]. Additionally, some patients may experience discomfort extending beyond this period, occasionally lasting up to a week, which underscores the importance of long-term follow-up for comprehensive assessment [48]. Monitoring pain over multiple time points provides insights into the temporal dynamics of post-treatment discomfort and helps identify factors that may prolong or diminish pain resolution.

Inclusion criteria in our study were carefully standardized to minimize confounding variables. Selecting asymptomatic patients pre-treatment reduces the likelihood that pre-existing pain influences post-operative discomfort [3]. Excluding patients who had taken analgesics in the previous 10 days helps eliminate the confounding effects of pre-medication, which can mask or alter pain perception [49]. Focusing on anterior teeth with single roots and straight canals simplifies the anatomical complexity, facilitating standardization and reproducibility. Multi-rooted posterior teeth often present challenges such as curved canals and accessory canals, which can influence instrumentation efficacy and subsequent pain outcomes [50]. Furthermore, limiting the sample to teeth treatable in a single session avoids the potential influence of intra-canal medicaments and cross-contamination, ensuring consistency in treatment protocols [16, 51].

The protocol employed in our study involved precise determination of working length, with a focus on maintaining a 0.0 mm reference point at the apex, considering the occurrence of apical stenosis approximately 1 mm below the main foramen [52]. This approach enhances the standardization of apical preparation, impacting the extent of bacterial removal and debris extrusion. The initial reaming of the coronal portion before establishing the working length aims to facilitate irrigation and reduce the risk of apical debris extrusion factors associated with post-operative pain [53].

Mechanical preparation utilized the ProTaper Next system, favored for its efficiency in shaping canals with minimal apical enlargement [54]. Its design allows for effective cleaning with less apical trauma, which is crucial for minimizing post-operative discomfort. The choice of a single-cone obturation technique aligns with evidence suggesting it reduces overfilling and extrusions compared to lateral or vertical condensation methods [55]. Such standardization reduces procedural variability, allowing for a clearer evaluation of the interventions under study.

Adjustments in the length of gutta-percha cones specifically setting them 1 mm short of the established reference point aimed to further control for overfilling and to isolate the effects of foraminal enlargement on post-operative pain [50]. This meticulous control helps differentiate pain caused by procedural trauma from that related to filling material extrusion. Adequate irrigation is critical in endodontic disinfection. In our protocol, activation of irrigants particularly sodium hypochlorite (NaOCl) for one minute, was employed to enhance penetration into dentinal tubules and disrupt biofilms, which previous studies have demonstrated as effective in reducing microbial load [22, 56].

The irrigation protocol involved intermittent flow, with three 20-second intervals, to optimize debris removal and biofilm disruption. This technique has been shown to be more effective than continuous irrigation in replenishing irrigant solutions and flushing out debris [57–59]. Effective irrigation not only improves disinfection but may also reduce post-operative inflammation and pain by decreasing residual microbial toxins and irritants within the canal system.

Our findings indicated that neither ultrasonic activation nor XP-Endo Finisher irrigation, nor foraminal enlargement, significantly influenced post-operative pain levels. This aligns with the hypothesis that these adjunctive techniques do not exacerbate periapical tissue inflammation when applied correctly, supporting their safety in clinical practice [23, 41, 72, 73]. Severe post-operative pain is often linked to iatrogenic injuries such as chemical or mechanical trauma or persistent microbial contamination [60, 61]. The absence of significant pain differences suggests that these procedures, when performed within established parameters, do not increase patient discomfort.

The typical inflammatory response post-treatment involves the release of mediators like prostaglandins, cytokines, and neuropeptides, initiating pain and swelling [41, 62]. Pain within the first eight hours likely stems from this inflammatory cascade. As healing progresses, inflammatory mediators decrease, and immune cells such as macrophages and leukocytes clear debris, leading to pain resolution. The observed decline in pain over the subsequent days corresponds with these biological processes [16, 63, 64].

Irrigation activation plays a pivotal role in reducing bacterial biofilms, delivering irrigants to inaccessible areas, and removing debris factors that may indirectly impact post-operative pain [63, 65, 66]. Ultrasonic activation, through acoustic streaming and cavitation, enhances the efficacy of irrigants, promoting better disinfection especially in the apical third a region often difficult to clean thoroughly [19, 67]. Similarly, the XP-Endo Finisher’s unique design enables it to adapt to canal morphology, reaching areas that traditional files may miss, thereby improving disinfection and potentially reducing residual bacteria that could cause ongoing inflammation [68–71].

Our results concur with prior studies indicating no significant difference in post-operative pain between techniques employing ultrasonic or XP-Endo Finisher activation and conventional irrigation [23, 41, 72, 73]. These findings suggest that while advanced activation methods may improve canal cleanliness, they do not necessarily translate into increased or decreased patient discomfort post-operatively. The lack of difference when enlarging the apical foramen aligns with previous evidence that, in asymptomatic cases, such procedures do not significantly affect pain levels [2, 3, 74].

Contrasting these findings, some studies have reported increased post-operative pain associated with apical enlargement or specific activation techniques. For example, Abbara et al. observed higher pain levels in the XP-Endo Finisher group, particularly on the first day post-treatment, possibly due to their use of chlorhexidine activation and larger lesion sizes [75]. These discrepancies highlight the influence of variables such as irrigant choice, lesion size, and instrumentation technique on outcomes. Similarly, Junior et al. and Saini et al. reported increased pain with manual apical enlargement, potentially attributable to the more traumatic nature of manual files and the anatomical complexity of multi-rooted teeth [16, 35].

On the other hand there are limitations of the study, the subjective nature of pain assessment remains a key limitation. Individual variability in pain perception, influenced by psychological, biological, and social factors, complicates the interpretation of results [42]. Additionally, the study’s focus on single-rooted anterior teeth limits the extrapolation of findings to multi-rooted or posterior teeth, which typically possess more complex anatomy and may exhibit different responses to endodontic procedures [50]. The sample size, while adequate for initial analysis, may not capture the full spectrum of variability seen in broader populations.

Furthermore, the study design did not account for long-term outcomes beyond one week, and it remains unclear how these interventions influence healing or persistent discomfort over extended periods. Future research should include larger, more diverse cohorts and consider additional variables such as different irrigants, activation protocols, and patient-specific factors like age, gender, and psychological profile. Incorporating objective measures, such as inflammatory markers, could also augment subjective pain reports.

As a result of that, our findings suggest that foraminal enlargement and advanced irrigation activation techniques including ultrasonic and XP-Endo Finisher activation do not significantly influence post-operative pain in asymptomatic, single-canal teeth. The biological processes underlying pain reduction appear consistent across the different interventions examined. Nonetheless, individual variability and anatomical differences necessitate cautious interpretation. These results reinforce the importance of meticulous technique and standardized protocols to optimize patient comfort and treatment success. Future studies expanding the scope to multi-rooted teeth, varying lesion types, and long-term outcomes are warranted to deepen our understanding of post-endodontic pain management.

Conclusions

In conclusion, our study demonstrated that neither foraminal enlargement nor the use of advanced irrigation activation techniques specifically passive ultrasonic irrigation and the XP-Endo Finisher had a statistically significant impact on post-operative pain levels in patients treated for necrotic, single-rooted teeth with periapical lesions. The findings suggest that when appropriate protocols are followed, these adjunctive procedures can be incorporated into endodontic practice without increasing patient discomfort, supporting their safety and efficacy in enhancing canal disinfection.

The temporal trend observed in our data showed that post-operative pain generally peaked within the first 8 h and gradually declined over the subsequent days, aligning with the typical inflammatory response to endodontic procedures. This pattern was consistent across all study groups, indicating that the biological healing process remains largely unaffected by the specific activation methods or foraminal enlargement. Our results reinforce the notion that effective disinfection and proper technique such as controlled instrumentation, adequate irrigation, and precise obturation are critical determinants of post-operative comfort.

Despite the absence of significant differences between groups, it is essential to recognize the limitations inherent in our study. The subjective nature of pain assessment, although standardized with the visual analog scale, can be influenced by individual pain thresholds, psychological factors, and social influences, which we could not fully control. Additionally, our focus on anterior, single-rooted teeth with straightforward anatomy limits the generalizability of our findings to more complex cases involving multi-rooted or curved canals. The relatively small sample size, while adequate for initial comparisons, may have limited the detection of subtle differences or rare adverse effects. Moreover, the follow-up period of one week precludes assessment of long-term outcomes such as periapical healing or persistent discomfort, which are crucial for comprehensive evaluation.

A cross-check of our references indicates that most in-text citations correspond appropriately to the reference list; however, careful verification is recommended to identify any discrepancies. While many of the cited studies are recent and relevant, some older references could be updated with recent systematic reviews or meta-analyses to strengthen the evidence base. Future research should aim to include larger, more diverse populations, extend follow-up durations, and incorporate objective biological markers such as inflammatory cytokines to better elucidate the mechanisms underlying post-operative pain.

As a result of that, our findings support the clinical flexibility of employing foraminal enlargement and advanced irrigation activation techniques without increasing post-operative discomfort in uncomplicated, single-canal necrotic teeth. These procedures, when performed within standardized protocols, can contribute to improved canal disinfection without compromising patient comfort. Nonetheless, clinicians should remain vigilant about individual variability and anatomical complexities, tailoring their approach accordingly. Further studies exploring long-term outcomes, different tooth types, and adjunctive measures are warranted to optimize endodontic pain management strategies.

Authors’ contributions

Maya Issa Saad conceptualized the idea, provided the treatment, and contributed to the writing and documenting. Kinda Layous conceptualized the idea and supervised the PhD thesis for Maya Issa Saad. Hassan Achour, Samar Ali Alsalameeh, Marwan Al-Raeei: funding and conceptualization of the research.All authors of the article contributed to the interpretation of data and the revision, formatting, and re‐editing of the manuscript. All authors read and agreed to the published version of the manuscript.

Funding

The study is funded by Damascus University with the grant number 202478520, and International University for Science and Technology (https://iust.edu.sy/ with the grant number 456944.

Data availability

All data generated or analysed during this study are included in this published article.

Code availability

Not applicable.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.