Influence of eccentric cyclic loading on implant components: Comparison between external joint system and internal joint system

The purpose of this in vitro study was to investigate the influence of eccentric loading on implant components by measuring screw loosening and observing these components under several load positions and magnitudes. The external and internal joint system implants with butt joint connection were subjected to cyclic loading tests according to the specifications of ISO 14801. Load position was set at 0, 4, or 8 mm, and load was set at 100 or 300 N. On the external joint system, the reverse torque values decreased with distal shift in the loading position and an increase in magnitude of load, and abrasion and deformation on the anti-rotation device were observed. On the internal joint system, no large decrease in reverse torque was observed even though increasing the load position and load, however, abrasion and deformation on the anti-rotation device as well as fracture at implant/abutment connection were observed.