Peri-implantitis surrounding oral implants is an inflammatory process affecting the soft and hard tissues resulting in rapid loss of supporting bone associated with bleeding and suppuration. The etiopathogenesis of early and late peri-implantitis is less well understood and seems to be related to the peri-implant environment and to the soft tissues/implant interface, to patient-related factors (smoke, systemic diseases, plaque control) and to host-parasite equilibrium. However, there is wide scientific evidence that demonstrates the direct correlation between oral microbiota and peri-implant mucositis or peri-implantitis. In particular, adherence and colonization of microbiota on plaque-exposed biomaterials, like c.p. titanium, are discriminant factors for the development of infection. Regenerative or resective surgical approaches are proposed for the treatment of peri-implantitis depending on the morphology and the shape of bone defects. The therapeutical approach of peri-implantitis surrounding dental implants comprises several aspects such as the removal of supra-gingival bacterial plaque, an appropriate surgical approach, the removal of granulation tissue and detoxification of the exposed implant surface, the elimination of the anaerobic ecosystem by the removal of peri-implant pocket (gingivectomy or apically repositioned flap) or by the regeneration of the peri-implant hard tissues and, finally, the establishment of an efficient plaque control regimen