Osseointegrated implants have been presented as an alternative to traditional prosthetic treatment. The success of dental implants depends largely on the functional and aesthetics criteria that may fail following peri-implant diseases, peri-implant mucositis as a reversible and peri-implantitis as irreversible condition. Peri-implantitis is the main cause which leads to the loss of bone to implant connection and results in the loss of the implant. It is defined as an inflammatory disease of the supporting soft and hard tissue around the implant. It is often compared to periodontitis, but unlike periodontitis it expands faster and is treated harder. Risk factors for the development of peri-implantitis are pathological microflora, smoking, poor oral hygiene, the residual cement, systemic diseases and periodontal disease diagnosed earlier. The clinical signs include formation of pockets, bone loss visible on the x-ray, the swelling of the surrounding tissue, bleeding and implant mobility. In the effort to avoid the loss of the implant the main topic of the recent research is the treatment of periimplantitis. Depending on the defect, non-surgical and surgical therapies are the methods of choice. Non-surgical therapy involves mechanical cleaning of bacterial plaque in pockets applying antiseptics and support antibiotic therapy. Surgical therapy is indicated in extensive defects. Mucoperiosteal flap is made to remodel the bone, remove the granulation tissue and to fill the defect with bone substitutes. New insights in the treatment of peri-implantitis involve the use of lasers and PRF. The goal of peri-implantitis treatment is to achieve reooseointegration which has been confirmed only in animal models so far. Vedrana Piha, diplomski rad 45 Although significant advances have been achieved in the study of peri-implantitis treatment, it still requires searching for the perfect method that will enable the recovery of soft and hard tissues around implants and achieve stabillity of the implant.