Background: The goal of implant therapy is to achieve both functional and cosmetic improve- ments. Dental implantation into defective alveo- lar ridges should be performed with more caution than treatment using a fixed partial denture or bridge. To prepare dental implants with biologi- cal stability and optimal function, it is necessary not only to establish appropriate conditions for prostheses but also to consider how they blend in with surrounding periodontal tissues. There have been several studies on the classification of par- tially edentulous alveolar ridges, but most of them reported simple ridge-defect patterns alone. Such classifications may not provide enough informa- tion for making dental implant treatment plans.