Osseointegration (from Latin osseus "bony" and integrare "to make whole") is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant ("load-bearing" as defined by Albrektsson et al. in 1981). A more recent definition (by Schroeder et al.) defines osseointegration as "functional ankylosis (bone adherence)", where new bone is laid down directly on the implant surface and the implant exhibits mechanical stability (i.e., resistance to destabilization by mechanical agitation or shear forces). Osseointegration has enhanced the science of medical bone and joint replacement techniques as well as dental implants and improving prosthetics for amputees. Definitions Osseointegration is also defined as: "the formation of a direct interface between an implant and bone, without intervening soft tissue". An osseointegrated implant is a type of implant defined as "an endosteal implant containing pores into which osteoblasts and supporting connective tissue can migrate". Applied to oral implantology, this refers to bone grown right up to the implant surface without interposed soft tissue layer. No scar tissue, cartilage or ligament fibers are present between the bone and implant surface. The direct contact of bone and implant surface can be verified microscopically. Osseointegration may also be defined as: Osseous integration, the apparent direct attachment or connection of osseous tissue to an inert alloplastic material without intervening connective tissue. The process and resultant apparent direct connection of the endogenous material surface and the host bone tissues without intervening connective tissue. The interface between alloplastic material and bone. History Osseointegration was first observed—albeit not explicitly stated—by Bothe, Beaton, and Davenport in 1940. Bothe et al. were the first researchers to implant titanium in an animal and remarked how it tended to fuse with bone. Bothe et al. reported that due to the elemental nature of the titanium, its strength, and its hardness, it had great potential to be used as future prosthesis material. Gottlieb Leventhal later described osseointegration in 1951. Leventhal placed titanium screws in rat femurs and said, "At the end of 6 weeks, the screws were slightly tighter than when originally put in; at 12 weeks, the screws were more difficult to remove; and at the end of 16 weeks, the screws were so tight that in one specimen the femur was fractured when an attempt was made to remove the screw. Microscopic examinations of the bone structure revealed no reaction to the implants. The trabeculation appeared to be