Peri-implant tissue breakdown can be the result of microbial action as well as of biomechanical and occlusal overload. The long-term goal of the treatment of peri-implant breakdown is to arrest the progression of the disease and to achieve a maintainable site for the patient. Peri-implant bony defects around functioning implants can be treated with either non-surgical or surgical (resective or regenerative) techniques. Bone regeneration is possible in selected peri-implant bony defects of functioning implants if appropriate surgical techniques are utilized and the etiologic cause is eradicated.