comparison of the antibacterial effect of 810 nm diode laser and photodynamic therapy in reducing the microbial flora of root canal in endodontic retreatment in patients with periradicular lesions

introduction: the aim of this study was to compare the antibacterial efficacy of diode laser 810nm and photodynamic therapy (pdt) in reducing bacterial microflora in endodontic retreatment of teeth with periradicular lesion. methods: in this in vivo clinical trial, 20 patients who needed endodontic retreatment were selected. after conventional chemo mechanical preparation of root canals, microbiological samples were taken with sterile paper point (pp), held in thioglycollate broth, and then were transferred to the microbiological lab. in the first group, pdt with methylene blue (mb) and diode laser (810 nm, 0.2 w, 40 seconds) was performed and in the second group diode laser (810 nm, 1.2 w, 30 seconds) was irradiated. then second samples were taken from all canals. results: cfu/ml amounts showed statistically significant reduction in both groups ( p < 0.001). cfu/ml amounts were compared between the two groups and there was no statistical difference. conclusion: pdt and diode laser 810 nm irradiation are effective methods for root canal disinfection. pdt is a suitable alternative for diode laser 810 nm irradiation, because of lower thermal risk on root dentin.