A 980 nm Diode Laser as an Adjunctive Therapy on the Healing of Apical Periodontitis Following Endodontic Retreatment: A Randomized Controlled Clinical Trial Study

<b>Introduction:</b> Apical periodontitis is one of the common dental diseases. Microorganisms are the main reasons for these lesions; irrigations are used to remove them, but because of limited penetration, the rinsing agents may not always kill the microorganisms. Laser irradiation is effective in canal disinfection. The goal of this study was to compare the effect of calcium hydroxide (Ca(OH)₂ ) and diode laser on the improvement of apical periodontitis following root canal retreatment (RCR). <b>Methods:</b> Twenty-four teeth of 19 patients with periapical lesions which needed RCR were divided into two groups (Ca(OH)₂ and Ca(OH)₂+laser irradiation [LI]). In the first session, after gutta-percha removal, cleaning, and shaping, Ca(OH)₂ was used for 10 days. In the second session, in the Ca(OH)₂+LI group, the irradiation utilizing a diode laser (using non-initiated 200-µm fiber, continuous wave (CW), power output of 1W) was done. The periapical radiographic healing was assessed before the retreatment and after 3-month and 6-month follow-ups by periapical index (PAI) Qrstavik. The quantitative data were analyzed (<i>P</i><0.05). <b>Results:</b> The initial periapical lesion score was 3.75 and 3.88 in the Ca(OH)₂ and Ca(OH)₂+LI groups, respectively. In the Ca(OH)₂ and Ca(OH)₂+LI groups, 3 months after the RCR, the average periapical lesion score was 2.94 and 3.05, respectively. In the Ca(OH)₂ and CA(OH)₂+LI groups, 6 months after the RCR, the average periapical lesion score was 1.80 and 1.75, respectively. No significant differences were found at the 3 and 6 months between the experimental groups. <b>Conclusion:</b> The diode laser can reduce the periapical lesion, but there was no significant difference between CA(OH)₂+LI and Ca(OH)₂ at 3-month and 6-month follow-ups.