Aim: This study aims to assess the effect of root canal disinfection with a 980 µm diode laser following chemomechanical root canal preparation on the severity of pain after root canal treatment (RCT).

Materials and Methods: In present study, asymptomatic, single-rooted teeth with periapical index (PAI) score 3 or 4 were included. All patients were treated with two visits of root canal treatment including dressing with calcium hydroxide. Patients were randomly divided into two groups (n: 28). 'Control (no laser)': The final irrigation was performed using 5ml 2.5% NaOCI, followed by 5 ml 17% EDTA and 5 ml distilled water. 'Laser Disinfection (LD)': Root canals were irradiated with 980 µm diode laser after final irrigation at both visits. The pain levels were evaluated using visual analog scale (VAS) after 8, 24, 48 hours and 7 days. In addition, analgesic intake and time intervals were recorded by patients. The collected data were statistically analyzed with the Chi-square and Mann-Whitney U test (p<0.05).

Inclusion Criteria:

• Healthy patients
• Patients that had asymptomatic, single-rooted teeth with PAI score 3 or 4

Exclusion Criteria:

• antibiotic use with in the last month,
• anti-inflammatory analgesic use within the last five days,
• systemic disorder, pregnancy or lactation,
• traumatic occlusion,
• presence of other teeth requiring RCT,
• teeth with root canal fillings,
• calcified canals,
• root resorption,
• periodontal diseases,
• sinus tracts
• severe crown destruction preventing rubber-dam application

Not decided which collected IPD or which IPD that underlie results to share in a publication.