BACKGROUND: Peri-implant diseases present in two forms - peri-implant mucositis and peri-implantitis.

MATERIALS AND METHODS: The literature was systematically searched and critically reviewed. Four manuscripts were produced in specific topics identified as key areas to understand the microbial aetiology and the pathogenesis of peri-implant diseases and how the implant surface structure may affect pathogenesis.

RESULTS: While peri-implant mucositis represents the host response of the peri-implant tissues to the bacterial challenge that is not fundamentally different from gingivitis representing the host response to the bacterial challenge in the gingiva, peri-implantitis may differ from periodontitis both in the extent and the composition of cells in the lesion as well as the progression rate. A self-limiting process with a "protective" connective tissue capsule developing appears to dominate the periodontitis lesion while such a process may occasionally be lacking in peri-implantitis lesions. Bacterial biofilm formation on implant surfaces does not differ from that on tooth surfaces, but may be influenced by surface roughness. Nevertheless there is no evidence that such differences may influence the development of peri-implantitis.

CONCLUSION: It was agreed that clinical and radiographic data should routinely be obtained after prosthesis installation on implants in order to establish a baseline for the diagnosis of peri-implantitis during maintenance of implant patients.