Periodontal disease is one of the most common dental pathologies which is found in more than 80% of the Japanese adult population. It is also one of the major causes of tooth loss where more than 50% of the tooth are lost due to the periodontal disease. To reconstruct the dental defects, and re-establish the lost functions due to the periodontal disease are very important aspects of the clinical dentistry. Because of the aging society, these services will become even more critical. To lose a tooth not only means a compromised masticatory efficiency, but it has a profound effect on the patient's QOL and ADL. That is why the rehabilitation of the dental function becomes so important. There are two major clinical procedures for the reconstruction of the lost dental functions. They are (1) bridge or partial denture, and (2) implant-supported prostheses. Among other problems, the crown-root ratio of the periodontally involved teeth are less than adequate to serve as an abutment tooth for a bridge, or a clasped tooth for a partial denture. Their prognosis is questionable because of an excessive load over the diseased tooth. Implant-supported prostheses, in contrast, have an excellent long term prognosis because the prosthetic appliances are directly supported by the jaw bone.