Effect of Integrated Apex Locator Motor Modes on Postoperative Pain in Endodontic Retreatment (EAL-Pain)

Effect of Integrated Electronic Apex Locator Modes on Postoperative Pain After Root Canal Retreatment: A Randomized Controlled Clinical Trial

This randomized controlled clinical trial aimed to evaluate the effect of different integrated electronic apex locator (EAL) modes on postoperative pain following nonsurgical endodontic retreatment. A total of 144 patients requiring retreatment of mandibular premolar teeth with periapical lesions were randomly assigned to four groups.

In the control group, working length was determined using a conventional electronic apex locator. In the experimental groups, an integrated EAL motor was used with three different modes: apical reverse, apical slow down, and apical stop.

All procedures were performed under standardized conditions. Postoperative pain was assessed using a numeric rating scale (NRS) at 6 and 12 hours and on days 1, 2, 3, 5, and 7 after treatment.

The study aimed to determine whether simultaneous working length control using integrated EAL modes influences postoperative pain compared with conventional working length determination.

Study Overview

• Status: Completed
• Conditions: Postoperative Pain; Apical Periodontitis; Endodontic Retreatment
• Intervention / Treatment: Device: Electronic Apex Locator; Device: Integrated Apex Locator Motor

Detailed Description

Accurate determination and maintenance of working length is essential for successful endodontic retreatment. Electronic apex locators (EALs) are widely used to improve the accuracy of working length determination. Recently, endodontic motors with integrated EAL systems have been developed, enabling simultaneous working length control during canal instrumentation. These systems incorporate different automatic apical control modes, including apical reverse, apical slow down, and apical stop, which may influence clinical outcomes such as postoperative pain.

This randomized controlled clinical trial was conducted to evaluate the effects of different integrated EAL modes on postoperative pain following nonsurgical endodontic retreatment.

A total of 144 systemically healthy patients with previously treated single-rooted mandibular premolars diagnosed with asymptomatic apical periodontitis were included. Patients were randomly allocated into four groups (n=36 each): (1) conventional electronic apex locator (control group; Root ZX Mini), (2) integrated EAL motor with apical reverse mode, (3) apical slow down mode, and (4) apical stop mode (Ai Motor; Motopex; Woodpecker).

In the control group, working length was determined using a conventional EAL and confirmed radiographically. In the experimental groups, working length determination and instrumentation were performed simultaneously using an integrated EAL motor according to the assigned apical mode.

All retreatment procedures were completed in a single visit under standardized clinical conditions by a single experienced operator. Root canal filling materials were removed, canals were prepared using rotary instruments, and irrigation was performed using 2.5% sodium hypochlorite and 17% EDTA with ultrasonic activation. Final obturation was carried out using a single-cone technique with a bioceramic sealer.

Postoperative pain was assessed using an 11-point numeric rating scale (NRS) at 6 and 12 hours and on days 1, 2, 3, 5, and 7 after treatment. The primary outcome measure was postoperative pain intensity.

The study evaluated whether different simultaneous working length control strategies using integrated EAL modes affect postoperative pain compared with the conventional electronic apex locator method.

• Study Type: Interventional
• Enrollment (Actual): 144
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Rize Province
    • Rize, Rize Province, Turkey (Türkiye), 53000
      • Recep Tayyip Erdogan University Faculty of Dentistry

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Systemically healthy patients aged between 18 and 65 years
• Patients requiring nonsurgical endodontic retreatment
• Single-rooted, single-canal mandibular premolar teeth
• Diagnosis of asymptomatic apical periodontitis
• Presence of a well-defined periapical radiolucency (PAI > 4)
• Teeth with previous root canal treatment performed at least 4 years prior
• Root canal fillings extending to at least the apical third without overfilling

Exclusion Criteria:

• Patients with symptoms such as pain, swelling, or sinus tract
• Patients with a history of smoking or alcohol use
• Teeth with open apices or root resorption
• Teeth with intraradicular posts
• Teeth with insufficient coronal tooth structure
• Teeth with perforation, instrument fracture, or overfilled canals
• Teeth with root curvature greater than 30 degrees
• Teeth with periodontal disease or probing depth >3 mm
• Cases not suitable for single-visit retreatment
• Patients who used analgesics within 12 hours prior to treatment
• Patients who used antibiotics within the last month
• Patients with cognitive impairment or psychological disorders

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Conventional Electronic Apex Locator; Working length was determined using a conventional electronic apex locator (Root ZX Mini) and confirmed radiographically. Endodontic retreatment procedures were completed using standardized protocols.	Device: Electronic Apex Locator; Working length was determined using a conventional electronic apex locator (Root ZX Mini). The measurement was confirmed radiographically, and endodontic retreatment procedures were completed under standardized clinical conditions.; Other Names: Root ZX Mini
Experimental: Apical Reverse Mode; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor operating in apical reverse mode during endodontic retreatment.	Device: Integrated Apex Locator Motor; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor (Ai Motor, Motopex, Woodpecker). The device operates with different apical control modes, including apical reverse, apical slow down, and apical stop, which automatically respond when the file reaches the predefined working length.; Other Names: Apical Reverse Mode; Apical Slow Down Mode; Apical Stop Mode
Experimental: Apical Slow Down Mode; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor operating in apical slow down mode during endodontic retreatment.	Device: Integrated Apex Locator Motor; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor (Ai Motor, Motopex, Woodpecker). The device operates with different apical control modes, including apical reverse, apical slow down, and apical stop, which automatically respond when the file reaches the predefined working length.; Other Names: Apical Reverse Mode; Apical Slow Down Mode; Apical Stop Mode
Experimental: Apical Stop Mode; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor operating in apical stop mode during endodontic retreatment.	Device: Integrated Apex Locator Motor; Working length determination and canal instrumentation were performed simultaneously using an integrated electronic apex locator motor (Ai Motor, Motopex, Woodpecker). The device operates with different apical control modes, including apical reverse, apical slow down, and apical stop, which automatically respond when the file reaches the predefined working length.; Other Names: Apical Reverse Mode; Apical Slow Down Mode; Apical Stop Mode

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Primary Outcome Measure	Postoperative pain intensity was assessed using an 11-point numeric rating scale (NRS), where 0 indicates no pain and 10 indicates the worst possible pain. Pain scores were recorded at 6 and 12 hours and on days 1, 2, 3, 5, and 7 following endodontic retreatment.	6 hours, 12 hours, and days 1, 2, 3, 5, and 7 after treatment

Collaborators and Investigators

• Sponsor: Recep Tayyip Erdogan University

Study record dates

Study Major Dates

• Study Start (Actual): August 13, 2025
• Primary Completion (Actual): October 10, 2025
• Study Completion (Actual): October 17, 2025

Study Registration Dates

• First Submitted: April 7, 2026
• First Submitted That Met QC Criteria: April 7, 2026
• First Posted (Actual): April 14, 2026

Study Record Updates

• Last Update Posted (Actual): April 14, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Postoperative pain; Endodontics; Retreatment; Time factors; Electronic apex locators
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Periodontal Diseases; Mouth Diseases; Stomatognathic Diseases; Postoperative Complications; Pathologic Processes; Periapical Diseases; Jaw Diseases; Periodontitis; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain, Postoperative; Periapical Periodontitis
• Other Study ID Numbers: EAL-RCT-2025; 2025/113 (Other Identifier: Turkish Medicines and Medical Devices Agency); E-24931227-514.13.02-5708670 (Other Identifier: Turkish Medicines and Medical Devices Agency)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No