Abstract: The present invention provides a treatment apparatus (1) for treating peri-implantitis. Treatment apparatus (1) is characterized by comprising: An application tip (2) that is adapted for insertion into the sub-gingival region between the screw fixture of a dental implant and the surrounding gingiva and/or bone, wherein the length of the application tip (2) is at least equal to the depth of the peri-implant pocket to be treated, and wherein the application tip (2) comprises one or more nozzles (3) for jetting pressurized sterile fluid (4) for removing the bacterial biofilms from the outer surface of the screw fixture of the dental implant in vivo; a handpiece (5) for holding and guiding the application tip (2); and a supply unit (6) for supplying pressurized sterile fluid (4) to the application tip (2).