Osseointegration under immediate loading: biomechanical stress-strain and bone formation--resorption.

During the past 10 years, clinicians have used two-piece implants as a one-piece system for immediate loading to accomplish early recovery for function and esthetics. The statistical analysis by the Institute of Clinical Materials demonstrates high survival rates of 92.3 +/- 8.3%. Animal experiments of beagle dogs have been carried out to analyze successful conditions of immediate loading according to the dependency of bone formation--resorption upon the biomechanical stress--strain of bone. Histometric investigations clarified that the micromotion of less than 30 microns at the implant-bone interface did not interfere with the osteogenesis and new bone growth at the implant-bone interface. Bone formation and resorption are discussed from the standpoint of minimum effective strain on living bone.