Abutment-to-fixture load transfer and peri-implant bone stress

Purpose: To uncover design principles for the abutment-fixture complex that reduce the stress concentration on the bone. Methods: A 3-dimensional finite element model was used to vary shape, elasticity, and connectivity of the abutment-fixture complex. We compared peri-implant bone stress of these designs. Results: Peri-implant bone stress was increased when the abutment could slide frictionless along the rim of the fixture, allowing the abutment to "lean into" the fixture rim and transfer loads near the bone crest. Conversely, bone stress was reduced when no motion was allowed (or no contact was made at all) between the abutment and the fixture rim. Bone stress was also reduced when the fixture was stiffer and thus more resistant to deformation, or when the fixture was wider.