By each clinician participating in the study; 40 patients (20+20) diagnosed with mild to moderate peri-implantitis, defined as 2-4 mm peri-implant bone loss, will be randomized to either test treatment with Labrida BioClean® or control treatment with titanium curettes. In total 240 patients (120 test and 120 controls) treated by 6 clinicians at 6 centers will be included in the study.