Antimicrobial Photodynamic Therapy for the Treatment of Apical Periodontitis

Objectives: To evaluate radiographically the in vivo reduction of the size of apical periodontitis after use of antimicrobial photodynamic therapy (aPDT) during single-session endodontic treatment, compared to multiple session. Methods: After experimental induction of apical periodontitis and root canals instrumentation, 40 teeth (80 root canals) were assigned into 4 groups: I (n=26) - root canals were dressed with a calcium hydroxide-based paste for 21 days followed by root canals filling; II (n=34) - roots canals were treated with the photosensitize phenothiazine chloride for 1 minute followed by irradiation with diode laser [l = 660 nm, 60 mW/cm²] for another minute (aPDT) and root canal filling in the same session; III (n=8) root canal were filled in the same session; and IV (n=10) -root canals were left empty. All teeth were restored. Radiographic analysis of the size of apical periodontitis was performed by measuring the lesions before and after 90 days of the treatment using the Image J Software. The reduction of apical periodontitis was calculated for each group. Mixed model was used for statistical analysis considering tooth and dog as random factors followed by Tukey’s post test. The significance level used was 5%. Results: aPDT (Group II) showed lower reduction in size of apical periodontitis (-0, 0238 %; 95% confidence interval- 95%IC: - 0,567 – 0,520) compared to Group I (0,632; 95%IC: 0,09 – 1,170). However, aPDT presented better results than Group IV (-0,556 %; 95% CI -1.149 – 0,039) and, despite the numerical tendency for more favorable outcome, no difference could be observed from Group III (-0, 5054; 95%IC -1.133 – 0,122). Conclusion: The treatment with aPDT did not show any difference in reduction of apical periodontitis compared to the single-session treated group. The Group I, which received a dressing with a calcium hydroxide-based paste, presented the greatest reduction of apical periodontitis.