IRCT201309119260N2 IRCT 2013-10-12 this study was self-funded by researchers. PDT in treatment of peri-implant diseases PDT= PhotoDynamicTherapy Efficacy of antimicrobial photodynamic therapy as an adjunctive to mechanical debridement in the treatment of peri-implant diseases: a randomized controlled clinical trial 2011-03-16 anticipated 30 Complete https://irct.ir/trial/9842 interventional Randomization: Randomized, Blinding: Single blinded, Placebo: Not used, Assignment: Other, Purpose: Treatment, Other design features: this is single-blind split mouth clinical trial. N/A peri-implant diseases. control: All implants underwent mechanical debridement, using plastic curettes followed by pocket irrigation with sterile saline. Hand instrumentation was carried out until the operator was assured that the implant surfaces were adequately debrided and no time restriction was considered. In control group, no further treatment was performed. intervention: in the PDT group, closed surface scaling followed by single-episode of photodynamic therapy. High medium photosensitizerwas injected inside the instrumented peri-implant pocket with a thin blunt needle, as far as mucosal margin starting from the apical portion of the pocket. The photosensitizer was left in the pocket for 3 minutes. Subsequently, the light emitting device with the wavelength of 630 nm and the intensity of 2000 mw/cm2, with a special tip was placed at the depth of pocket, according to the manufacturer’s instruction. The device, used in this research for implant surface irradiation, was in contact with 6 aspects per implant. Every aspect of implants was irradiated for 20 seconds, making a total of 2 minutes..