Peri-implantitis has been defined as an inflammatory condition involving dental implants, surrounding mucosa and bone, which lose supporting bone. Bone, for a variety of reasons, is lost around the dental implant. Most patients are unaware that they have bone loss around the dental implant. Peri- implantits generally progresses in a painless fashion. The objective of this review is to identify case definitions and clinical criteria of peri-implant healthy tissues, peri‐implant mucositis, and peri‐implantitis and to introduce a classification system based on added clinical, and detailed radiological parameters with prognosis and staged treatment algorithms and todescribe the different approaches to manage both entities. The case definitions were constructed based on a review of the evidence applicable for diagnostic consideration. There is lack of a standard classification system to differentiate the various degrees of peri-implantitis, which produces dilemma in evaluating the stages clinical and radiological status, treatment and its outcome. Many classifications has been proposed in medical literature with their pros and cons but still there is lack of standard classification system of implant defects and definite treatment protocol according to the same. The classification should be easy to use, clearly understandable and help in communication by clinicians of different specialty.