Effect of Photodynamic Therapy on Postoperative Pain in Posterior Teeth with Symptomatic Apical Periodontitis

•Symptomatic apical periodontitis (SAP) produces discomfort to palpation, percussion, and spontaneous pain.•With the presence of necrotic content, the complete relief of the symptoms may not be achieved, and oral medication is frequently required.•This study showed that photodynamic therapy (PDT) is an adjunct step helpful to relieve pain in patients with SAP. This study aimed to evaluate the impact of photodynamic therapy (PDT) after root canal preparation on pain relief in posterior teeth presenting with symptomatic apical periodontitis (SAP). A visual analog scale (VAS) was completed by the patients which registered their pain perception as none (0), mild (1-3), moderate (4-7), or severe (8-10). Only patients who registered moderate or severe pain were included. Seventy patients were allocated to two groups (n=35): a control group (CG) without the PDT application and an intervention group with PDT application (PG). The same chemo-mechanical preparation was achieved in both groups. In the PG, 150 µM methylene blue (MB)Please remove the underline was placed inside the canal for 2 minutes and a 660 nm wavelength laser was applied through a fiber for 3 minutes (100 mW, 600 J/cm², total 18J). The patients were asked to register their pain perception in the VAS document after 24-h, 72-h, and 1-week intervals. The number of tablets taken for pain relief was also recorded. The Mann-Whitney, Students T-test and Fisher´s exact tests were used for statistical analysis (P < .05). After 1 week, 32 patients in the CG and 33 in the PG returned their VAS cards. The PG resulted in lower pain levels after the 24-hour interval (median 0) than the CG (median 2); there was no difference between both groups at 72-h and 1-week intervals. The decrease in pain was higher in the PG at all time-intervals when compared to the CG. There was no difference in the mean number of tablets taken for pain relief (P > .05). Within the limitations of this study, it can be concluded that PDT was efficient in decreasing pain in teeth presenting with SAP. There was no difference observed after 72 hours and there was no impact on the intake of pain relief medication.