Root canal therapy (RCT) aims to eliminate infection from the root canal system and to prevent reinfection¹. A major aspect of successful RCT is adequate cleaning and shaping of the canal while minimizing complications such as postoperative pain². One technique used to enhance cleaning is the maintenance of apical patency, defined as the extension of a small K-file slightly beyond the apical foramen to keep it free of debris³.

Advocates of apical patency argue that it prevents apical blockage, improves irrigation flow, and aids in complete debridement⁴. On the other hand, critics contend that apical patency may cause extrusion of debris and irrigants into periapical tissues, possibly leading to postoperative pain and inflammation^5,6. Postoperative pain is reported in 25–40% of root canal cases and significantly impacts patient perception of treatment quality⁷.

Several clinical and in vitro studies have attempted to analyze the relationship between apical patency and postoperative pain, but results have been inconclusive. Some researchers, like Arias et al., observed increased pain in cases with patency⁸, while others such as Siqueira et al. found no significant difference⁹. These inconsistencies may stem from differences in patient selection, instrumentation protocols, and pain assessment methods¹⁰.

This study seeks to clarify the impact of apical patency on postoperative pain in a well-defined clinical population. A randomized, controlled, prospective design was adopted to evaluate pain intensity at multiple intervals. The findings will help inform clinical decision-making on whether to adopt or avoid apical patency during root canal procedures.

This was a prospective, randomized clinical study conducted at the Department of Conservative Dentistry and Endodontics, involving 100 patients requiring primary root canal treatment in single-rooted teeth.

Inclusion Criteria:

• Patients aged 18–50 years
• Single-rooted teeth with a diagnosis of irreversible pulpitis
• No signs of periapical pathology (radiolucency)
• Good general health and ability to give informed consent

Exclusion Criteria:

• Retreatment cases
• Patients on analgesics or anti-inflammatory medication
• Pregnancy or lactation
• Systemic conditions affecting pain perception (e.g., diabetes, neurological disorders)
• Teeth with open apices or calcified canals

Randomization and Group Allocation:
Patients were randomly assigned into two groups of 50 each:

• Group A (Patency Group): Apical patency maintained using a #10 K-file extended 0.5–1 mm beyond the working length during cleaning and shaping.
• Group B (Non-Patency Group): Apical patency was not maintained; instrumentation remained strictly within the canal length.

Clinical Procedure:
Local anesthesia was administered, and standard access cavities were prepared. Working length was established using an apex locator. Rotary instrumentation with ProTaper Universal system and 5.25% sodium hypochlorite irrigation was used. Final obturation was completed using gutta-percha and AH Plus sealer. No intracanal medicament was placed.

Pain Assessment:
Patients recorded their pain levels using a 10-point Visual Analog Scale (VAS) at 6 hours, 24 hours, 48 hours, and 7 days post-treatment. Flare-ups were defined as severe pain or swelling requiring unscheduled intervention.

Statistical Analysis:
VAS scores were compared between groups using Student's t-test. Repeated measures ANOVA was applied to analyze trends over time. A p-value <0.05 was considered statistically significant.

Table 1: Demographic Distribution

In table 1, Group A consistently reported higher pain scores than Group B at 6 and 24 hours postoperatively, with statistically significant differences (p < 0.05). By 48 hours, the difference in pain scores between the groups became statistically non-significant. At 7 days, both groups had nearly negligible pain, indicating full recovery.

Table 2: Mean VAS Scores at Different Time Intervals

In table 2, A larger percentage of patients in Group A experienced moderate-to-severe pain (VAS ≥ 4) at early time points, especially at 6 hours (30% in Group A vs. 8% in Group B). By 24 hours, this difference narrowed but remained evident.

Table 3: Frequency of Moderate-to-Severe Pain (VAS ≥ 4)

In table 3, At 6 hours: 30% of Group A had moderate-to-severe pain vs. only 8% in Group B. At 24 hours: 16% of Group A reported pain vs. just 4% in Group B.

Table 4: Flare-Ups Requiring Intervention

Table 5: Gender-Wise Pain Perception at 6 Hours

In table 5, Females in Group A reported higher pain (VAS 4.7) than males (VAS 4.5) at 6 hours. Females in Group B reported lower pain (VAS 2.8) than males (VAS 3.0).

Table 6: Overall Mean Pain Reduction from 6 Hours to 7 Days

In table 6, Group A experienced a greater absolute drop in pain (VAS reduced from 4.6 to 0.4) compared to Group B (2.9 to 0.3).

The findings of this study suggest that apical patency increases the risk of early postoperative pain, particularly within the first 24 hours after root canal therapy. This supports the hypothesis that mechanical disturbance of periapical tissues and extrusion of irritants are key factors in early inflammation^11,12. However, since pain levels normalize by day seven, the impact appears to be temporary and self-limiting.

Our results corroborate studies by Arias et al. ¹³ and Tinaz et al. ¹⁴, who observed elevated pain scores in patency-maintained cases. In contrast, Siqueira et al. ⁹ found no significant difference, which may be due to variations in instrumentation, irrigation, and patient profiles. It is noteworthy that none of our patients experienced flare-ups, which suggests that apical patency, when performed with caution, does not predispose to severe complications.

From a mechanistic standpoint, patency files may push debris beyond the apex, causing neurogenic inflammation, as demonstrated in animal studies by Nair and Henry¹⁵. Clinically, this translates into transient pain. However, patency also prevents apical blockage, a benefit well documented in the work of Buchanan¹⁶ and Ruddle¹⁷, potentially contributing to long-term treatment success.

A significant strength of our study is the randomized design and use of a standardized pain assessment tool (VAS). However, we acknowledge certain limitations:

• Only single-rooted teeth were studied, which may not represent multirooted anatomy.
• No biochemical or histological markers were evaluated to quantify inflammation.
• Patients were not stratified by pain tolerance or psychological factors.

Future studies should explore the long-term success rates and retreatment needs associated with apical patency and analyze the cost-benefit ratio of the technique.

Apical patency in root canal therapy leads to a statistically significant increase in early postoperative pain, particularly in the first 24 hours. However, the pain is transient and resolves within a week without flare-ups or complications. While patency may improve canal cleaning and reduce blockages, clinicians must weigh its short-term drawbacks against its mechanical benefits. Proper technique and case selection remain essential for optimizing patient outcomes.

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Ng YL, Mann V, Gulabivala K. Outcome of primary root canal treatment: systematic review