An endosteal implant is placed directly into the alveolar bone and can be classified as either root form or plate form. The root form implant mimics the shape of a natural tooth root and is the most commonly used type. The plate form implant has a flat, blade-like shape designed for insertion into narrow ridges where root form implants are not feasible. Both types require surgical placement into bone to achieve osseointegration, distinguishing them from subperiosteal implants that sit on top of the bone under the periosteum. Thus, endosteal implants encompass both root and plate forms based on bone anatomy and clinical indications.

Reference: Contemporary Implant Dentistry, Carl E. Misch, 3rd Edition.