Endosseous implants: the host-implant surface.

The long term success of dental implants depends on the formation and retention of a stable host-implant interface: in the case of endosseous dental implants probably by ankylosis. This situation is influenced by: site preparation, implant material, epithelial behaviour, stress distribution, and oral hygiene. Thermal trauma and wound contamination are important in site preparation, if unfavourable and irreversible changes in the bone are to be avoided. Metals, plastics, and ceramics have all been used for making implants. Of the metals titanium and some titanium alloys have proved particularly suitable. The plastics and ceramics have poor physical properties for dental implant construction on their own, although composites, many of which are biocompatible, such as hydroxyapatite reinforced polyethylene and carbon fibre reinforced carbon may overcome these problems. Epithelium tends to migrate from the oral cavity around an implant and whilst there is some evidence for an epithelial attachment this is little understood. Loads on bone can modify its behaviour leading to an increase or decrease in its rate of formation or resorption, and whilst this has never been quantified it is known that excessively rigid implants can lead to high stress gradients in the surrounding bone. Poor attention to oral hygiene may lead to inflammation in the tissues around an implant and hasten its loss.