Dental implantology is a rapidly advancing area of dentistry providing a number of alternative treatment possibilities for patients with partially or fully edentulous mouths. The following article is the first in a series of three dealing with various aspects of dental implantology, with a particular emphasis on those areas related to field of periodontology. In this paper we shall consider the biological basis of dental implants, different implant systems, and the peri-implant sulcus. Forthcoming articles will cover the diagnosis and treatment of peri-implantitis and failing implants, guided bone regeneration around implants, immediate implant placement, the placement of implants in the posterior maxillae, and implant maintenance.