Overview

This randomized controlled clinical trial aims to evaluate the effect of the number of rotary files on working length negotiation and postoperative pain in the second mesiobuccal (MB2) canals of maxillary first molars. Patients are assigned to one of four groups according to the number of rotary files used: single-, two-, three-, or four-file systems. Postoperative pain is assessed on each of the seven consecutive postoperative days (Days 1-7) using a visual analog scale (VAS), and working length negotiation success is recorded during canal instrumentation.

Eligibility

Inclusion Criteria:

• Systemically healthy individuals aged between 20 and 65 years
• Requiring primary endodontic treatment of maxillary first molars
• Diagnosis of asymptomatic apical periodontitis and pulp necrosis based on clinical and radiographic findings
• Presence of a second mesiobuccal (MB2) canal in the maxillary first molar
• Absence of or only minimal preoperative pain or symptoms
• Periapical lesions smaller than 5 mm in diameter
• Ability to comply with follow-up visits and effectively communicate during the treatment process

Exclusion Criteria:

• Presence of symptomatic apical periodontitis or acute apical abscess
• Retreatment cases (teeth previously treated endodontically)
• Use of medications such as narcotics, antibiotics, sedatives, or antidepressants within one week prior to treatment
• Presence of a sinus tract, periapical abscess, or facial cellulitis
• Pregnancy or breastfeeding
• Inability to understand or follow the study instructions