Stress and strain patterns of 1-piece and 2-piece implant systems in bone: a 3-dimensional finite element analysis.

STATEMENT OF PROBLEM The transition from implant to abutment is solid in 1-piece (1P) and broken in 2-piece (2P) implant designs. This difference may affect occlusal load distribution and marginal bone response. PURPOSE To determine whether 1P and 2P implants with equivalent geometries exhibited stresses and strains differently under applied loading conditions. MATERIALS AND METHODS Design software simulated 1P and 2P implants restored with metal copings and embedded in 3 cylindrical bone block models that varied in dimensions, density, and percentage of bone-to-implant contact. Three-dimensional, finite element analysis simulated occlusal loading. Experiments evaluated stresses and strains relative to implant design and (1) periimplant bone thickness, (2) cortical bone thickness, (3) magnitude and direction of occlusal loading, and (4) % bone-to-implant contact. RESULTS Implants with equivalent dimensions exhibited comparable stresses and strains in all experimental conditions. Implant diameter and periimplant bone thickness influenced stress levels. Only small-diameter (3.0 mm) 1P implants in low-density bone exhibited stress levels that might adversely affect marginal bone stability. CONCLUSIONS Implant diameter and periimplant bone thickness influenced load distribution in bone, but the type of implant-abutment transition had no significant effect. Small-diameter 1P implants should be limited to dense bone to minimize stress concentrations.