Efficacy of sonic irrigation activation approaches in managing post endodontic pain: a randomized clinical trial

Introduction

A satisfactory endodontic therapy is bounded to efficient filling, followed by proper cleaning and shaping. However, post endodontic pain (PEP) is a frequent complication, with incidence rates varying between 3% and 58% [1]. PEP is thought to arise from the displacement of bacteria, dentinal debris, and necrotic tissue during biomechanical preparation, which can trigger an inflammatory reaction in periapical tissues, resulting in pain [2, 3]. To minimize PEP, many researchers highlight the need to maintain a sterile environment throughout treatment, and choose appropriate instruments for biomechanical preparation [4]. Different nickel-titanium (NiTi) rotary systems with advanced technology and design can affect the amount of debris extrusion, which may contribute to variations in PEP, as excessive debris pushed beyond the apex can lead to inflammation and discomfort in the periapical area [5]. Manufactured with M-wire, ProTaper Next (PTN) (Dentsply-Maillefer, Ballaigues, Switzerland) increases the flexibility and cyclic fatigue, allowing efficient cutting and reducing the risk of taper lock and screw-in effects during root canal preparation [6, 7]. In contrast, TruNatomy (TN) is a newer generation of rotary file systems, designed to provide safe and effi­cient root canal preparation. TN files are specifically engineered to create a continuous taper while maximizing preservation of the pericervical dentin, helping maintain the tooth’s structural integrity, which can reduce the risk of debris extrusion and PEP [8].
Teeth with complex anatomy are at a greater risk of irrigant and debris being exceeded through the apex. Side-vented needles (SV) improve the irrigation process during root canal treatment by directing both debris and irrigants sideways rather than apically. This design reduces the likelihood of pushing material into periapical tissues, thus enhancing safety and effectiveness of the irrigation while minimizing the potential for post endodontic complications, such as PEP [9]. To prevent complications during irrigation, using a sonic irrigation system, such as EndoActivator (EA) that functions at frequencies between 1 and 6 kHz, can be advantageous. As an effect of oscillation and vibration, the breakdown of residual debris and cleaning of the dentin tubuli is enhanced. This improved cleaning action ensures better canal debridement, reduces extrusion’s risk, and contributes to more effective treatment, ultimately minimizing the chances of PEP [10].
As Ramamoorthi et al. [11] proved, traditional endodontic needles aggravate more postoperative pain compared with EA. This suggests that sonic activation provided by the EA system that improves irrigation efficacy by creating a more effective fluid movement, may help reducing PEP by minimizing debris extrusion and enhancing cleaning within the root canal system.
In the current study, to prevent root canal bacterial regrowth, minimize leakage, loss of temporary fillings, save chair time, lessen postoperative discomfort, and reduce analgesics’ application, the whole root canal treatment was completed in one session [12].

Objective

The aim of the study was to compare and evaluate the impact of PEP using side-vented needles and EA with two different file systems, i.e., PTN and TN, in the context of single-visit endodontics. According to the null hypothesis, an instrumentation with two different file systems combined with irrigation protocol has no effect on postoperative pain.

Material and methods

This randomized clinical trial was a factorial study, conducted from December 2022 to March 2023, after obtaining Ethical Committee approval (CTRI number: CTRI/2022/04/041662). The study was designed following the Consolidated Standards of Reporting Trials (CONSORT) statement, and conducted in accordance with the Declaration of Helsinki, ensuring adhering to ethical guidelines. Prior to initiating treatment, a written consent was signed by all individuals after understanding the treatment protocol.

Sample size and patient selection

Sample size was determined based on an alpha level (α) of 0.05 and a study power of 0.8, resulting in 35 participants per group, ensuring statistical significance and adequate power to detect meaningful differences between groups.
Patient selection started with a thorough intraoral evaluation, with pulp’s status assessed, followed by hard tissue and soft tissue evaluation. Intraoral radiograph was performed to check for the presence of periapical radiolucency, ensuring that only patients with asymptomatic irreversible pulpitis were included in the study. A total of 140 patients were enrolled into the study, as presented in Figure 1.

Inclusion and exclusion criteria

Inclusion criteria were age between 20 and 60 years, asymptomatic irreversible pulpitis, and permanent maxillary or mandibular molars.
Exclusion criteria were teeth with calcified canals, those with cracks, resorption, or immature roots, pregnant or lactating women, patients with any conflicting medical history that could interfere with the study, and individuals who received analgesics before a day.

Randomization protocol

In total, 140 volunteers were included in the study and divided into four groups (n = 35 per group) using a double-blind randomization method to minimize bias. To ensure impartial allocation, 140 opaque envelopes were prepared, each containing a random group assignment. These envelopes were selected by a dental assistant prior to treatment, ensuring that neither the clinician nor the patient knew to which group they were assigned until treatment. Authenticity of the system used was preserved with the clinician.

Treatment protocol

In order to maintain consistency, every procedure was performed by a single clinician. At first, 2% lignocaine was administered for patient’s comfort and after anesthesia, a rubber dam was applied to ensure sterile field and proper isolation of the tooth. Caries was removed from the tooth, and standard access cavity was prepared to gain access to the pulp chamber. Finite working length with #10 K-file and Propex Pixi apex locator (Dentsply-Maillefer, Ballaigues, Switzerland) was measured. A radiograph confirmation was achieved.

Canal preparation

Root canals were prepared according to a group assignment, utilizing a crown-down technique. The following groups were used for canal preparation: Group 1: PTN-SV, group 2: PTN-EA, group 3: TN-SV, and group 4: TN-EA. All root canal preparations were done according to the manufacturer’s instructions using X Smart endomotor (Dentsply-Maillefer, Ballaigues, Switzerland). By following this standardized treatment protocol, the study ensured consistency in the treatment process, allowing for reliable comparison of outcomes between different groups of samples.

Irrigation protocol

Using conventional syringe, irrigation was performed with 10 ml of 3% sodium hypochlorite in the prepared canal, after which, the canals were flushed with 2 ml of 17% EDTA solution for 1 minute to remove the smear layer and improve efficacy of NaOCl.
For groups 1 and 3 (PTN-SV and TN-SV), 3% NaOCl was applied to irrigate the canals up to 4 ml. A 30-gauge side-vented needle (Fanta Dental Materials Co. Ltd., Shanghai, China) was inserted 2 mm short of working length to deliver the irrigant. The design of side-vented needle helped directed the flow of irrigant laterally, preventing it from being pushed apically, thus reducing the risk of irrigant or debris being forced into the periapical area, which could lead to complications. For groups 2 and 4 (PTN-EA and TN-EA), the EA tip (size 20/0.02) was placed loosely 2 mm from working length. A 3% NaOCl solution was applied to irrigate the canal, and the EA was set at 10,000 cycles per minute, performing a pumping motion. The tip was moved vertically in 2-3 mm strokes for 1 minute to improve irrigant agitation and enhance canal cleaning.
After the final step of irrigation with normal saline and to receive the fluid, field-free paper points were employed. The canals were obturated with gutta-percha and AH Plus sealer. A postoperative radiographs were taken to confirm the accuracy of obturation, and to ensure there were no voids or gaps. Following obturation, the teeth were restored with composite resin to verify functional and aesthetic post endodontic restoration.

Postoperative instructions

After the procedure, patients were requested to complete a visual analogue scale (VAS) questionnaire to record their pain levels at four time intervals: 6 hours, 12 hours, 24 hours, and 48 hours, while pain-relieving brufen 400 mg was advised if required (in case of severe pain).

Follow-up evaluation

Pain level and of medicine intake were recorded by the patient who was requested to report back to the clinician and submit the forms at 48 hours follow-up appointment. Patients were reminded to complete the form over phone.

Results

The obtained data from the study were analyzed using statistical package for social sciences (SPSS) software, version 20.0, which is commonly used for performing statistical tests and data analysis. VAS scores for pain were employed as the primary outcome measure to assess PEP at different time points (6, 12, 24, and 48 hours). These VAS scores were summarized by calculating mean and standard deviation (SD) to provide a clear indication of the average pain levels and variability of the mean for each group. To compare the differences in PEP scores among the four groups, a post hoc test was performed. If a patient had severe pain, swelling, or any unwanted condition, they were used as secondary outcome. Statis­tical significance level was set at 0.05, thus a p-value below this threshold was considered significant. The demographic data of all groups were recorded, including age, sex, or location, as shown in Table 1.
Data presented the mean and standard deviation (SD) of posttreatment pain scores at 6, 12, 24, and 48 hours after treatment. For all groups, there was a significant reduction in pain scores over time, with p-values of 0.000 for all comparisons, indicating highly significant diffe­rences in pain scores at different time points (Table 2).
P-values for pairwise comparisons of VAS scores among four groups at 6, 12, 24, and 48 hours posttreatment were evaluated, revealing statistically significant differences in pain scores between the groups at each time point (Table 3).

Discussion

PEP can arise from a variety of factors, both mecha­nical and chemical, which occur during or after the root canal procedure. Mechanical factors, such as over-instrumentation, where instruments are forced beyond the root canal system, can cause trauma to periapical tissues, leading to inflammation and discomfort [12]. Similarly, the extrusion of irrigants or filling materials beyond the apical foramen into the periradicular area is another major contributor to PEP. This extrusion can introduce debris, irrigating solutions, or sealing materials into the surrounding tissues, causing an inflammatory response in the periapical region. Such inflammation can heighten the severity of posttreatment pain, often resulting in significant discomfort or delayed healing. Various methods are utilized to assess pain in patients, including the numerical rating scale, defense and veterans pain rating scale, and adult nonverbal pain scale. However, in this study, the VAS was chosen to assess pain due to its proven reliability and simplicity [13]. To reduce the risk of misinterpretation, the pain assessment questionnaire was designed to be straightforward and easy for patients to understand.
For PEP management, nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed, as they are effective in reducing inflammation and pain. In this study, brufen 400 mg, a widely used and efficient NSAID, was administered to manage PEP when necessary [14]. This approach ensured that the majority of patients experienced manageable pain levels, contributing to their overall comfort during the posttreatment recovery phase. Furthermore, irrigants, such as sodium hypochlorite (NaOCl), can be cytotoxic if extruded, which may worsen tissue irritation and increase the risk of PEP. As a result, meticulous control of instrumentation and irrigation methods is crucial to reduce these complications and enhance posttreatment recovery [6].
PEP is partly driven by substance P and calcitonin gene-related peptide, which are activated when periradicular debris are extruded into surrounding tissues. These neuropeptides bind to G protein-coupled receptors on nociceptors, sensitizing them and lowering their pain threshold. This process leads to a heightened pain perception and inflammation in the periapical area, contributing to the severity of PEP. Managing debris extrusion is the key element of minimizing this pain [11].
Teeth with apical periodontitis, periradicular lesions, and fistulation communication, were excluded from the study to avoid complications related to infection. In these conditions, there is a higher likelihood of irrigating solutions being extruded beyond the apex, potentially leading to further infection. Therefore, only teeth with asymptomatic irreversible pulpitis were included to ensure a more controlled and consistent environment for evaluating PEP [15]. The reduced PEP associated with PTN and TN files can be attributed to their advanced designs and materials. PTN files, made from M-Wire NiTi alloy, offer enhance flexibility and improve resistance to cyclic fatigue, allowing for smoother and more controlled instrumentation [7], with the file’s off-center rectangular design combined with progressive and regressive tapers. The specific design of the file allows mini­mizing the screw-in effect, which helps in preventing the taper lock, resulting in less stress to the tooth and smoother preparation; it also allows specialized reduction of the contact area between the file and root dentin. These features help decrease the possibility of pain during and after treatment [15]. Moreover, when used in conjunction with the EA method, these files help further alleviate posttreatment discomfort, highlighting important effects of both design and material choice on enhancing endodontic results.
Similarly, the TN NiTi rotary system (Dentsply, Sirona, USA) also demonstrates enhanced flexibility due to its heat-treated NiTi alloy and its slim, off-centered pa­rallelogram cross-section [16, 17]. This design, crafted from 0.8 mm NiTi wire, provides greater flexibility than traditional instruments. Studies by Van der Vyver et al. [8] have highlighted the durability of TN files, which owe their resilience to the combination of regressive tapers and heat-treated NiTi alloy. Furthermore, Falakaloglu et al. [18] reported that with the TN files, less debris was extruded compared with ProTaper Gold, suggesting that the TN system may lead to lesser PEP by reducing the risk of debris extrusion and improving overall treatment efficiency. Commonly known for having strong antibacterial properties and ability to effectively dissolve necrotic tissue and dentin debris, 3% NaOCl is utilized as an irrigation solution in endodontics. However, for better removal of inorganic material, such as the smear layer, 17% ethylenediaminetetraacetic acid (EDTA) is used. EDTA acts as a chelating agent that efficiently removes calcium from dentin, and improves the cleanliness of the canal walls for better seal and bonding. After EDTA irrigation, saline is applied to flush out any remaining irrigant and neutralize the chelating effect, which is important to avoid the prolonged interaction of EDTA with the dentin [19].
A study by Najim et al. [9] evaluated postoperative pain following irrigation with side-vented Navi Tips, and found less pain at 4, 12, and 24 hours compared with end-vented Navi Tips. The authors observed that irrigation with end-vented needles could lead to a vast amount of sodium hypochlorite extruding into the periapical area, which could potentially cause tissue necrosis, contributing to PEP due to excessive force applied. To minimize this risk, side-vented needles were selected in the present study, as they direct the irrigant laterally and reduce the chances of irrigant extrusion beyond the apex, preventing unnecessary tissue damage [9].
The EA works by creating vibrations through its up-and-down motion, and small vertical strokes help establish a powerful hydrodynamic effect. This movement enhances the penetration of irrigating solution into the canal, promoting better cleaning and debris removal [20]. The action of the EA ensures that the irrigant is effectively exchanged at the apex, preventing its extrusion beyond the root tip. This mechanism significantly reduces the risk of posttreatment discomfort, as it minimizes the chances of debris being pushed into the periapical tissues, which is a known cause of PEP. These factors collectively contributed to the reduction of PEP in the study, primarily due to the efficient removal of debris and proper irrigation during treatment [21].
The results of the present trial indicate that the TN files cause less PEP compared with the PTN files. This difference may be attributed to the design of the TN file, which is more flexible and requires fewer insertions during the instrumentation process compared with the PTN file. The increased flexibility of the TN files allows gentler preparation of the canal, decrease trauma to the surrounding tissues, and fewer insertions help mini­mize irritation. When comparing SV needles with EA, the study found that the EA resulted in lower PEP than SV needles. This can be explained by the dynamic, vibrating tip of the EA, which creates a more efficient hydrodynamic action that better flushes debris and irrigants from the canal, preventing extrusion beyond the apex and reducing posttreatment discomfort. Hence, the hypothesis was rejected.
The limitation of the study are only two file systems (PTN and TN) and two irrigation protocols, focusing exclusively on asymptomatic irreversible pulpitis. Future research might examine different file systems, irrigation protocols, and include a variety of pulpal diseases, such as necrotic pulp or apical periodontitis, to better understand their impact on PEP and improve treatment outcomes.

Conclusions

The study indicates that utilizing advanced file systems in combination with sonic agitation may alleviate PEP. Pain levels progressively decreased following the initial 6 hours of TN use.

Disclosures

1. Institutional review board statement: Not applicable.
2. Assistance with the article: None.
3. Financial support and sponsorship: None.
4. Conflicts of interest: None.

References