In the Branemark system, it’s the osseointegration, the meshing of implant and bone. The properties of the implant are such that a chemical and mechanical bond is formed. The jawbone actually grows into the implant. But the real benchmark for the success of a dental implant procedure is this: The patient has to be happy with it. For years.
For certain people, a single implant to bridge a gap is called for. Another person might require two to support a bridge, or two to four implants to stabilize a lower denture. In other people, bone loss is already severe, and what remains cannot support an overdenture, so a tooth implant procedure is not the solution. However, when they work, they’re as real as it gets.