Biomechanical aspects of bone-level diameter shifting at implant-abutment interface

To evaluate the effect of diameter shifting at implant-abutment interface on load distribution at periimplant bone and within implant-abutment complex.

Eight different implant-abutment connections were designed and simulated numerically. Implant-abutment microgap at bone level was hypothetically set-off inward toward the central axis of implant to create "diameter shifting" or "platform switching" concept. The conceptual design was further characterized with horizontal set-off distance, emergence angle, and restorative height. A control model of conventional implant-abutment connection with restorative relation was also involved for comparison of developed stresses in periimplant bone and within implant-abutment complex. A 14 mm x 16 mm acrylic cylinder with vertically placed implant-abutment complex was considered for all designs. Principal and Von Mises stresses under vertical and oblique static loading conditions were evaluated numerically and presented descriptively.

Stress distribution at periimplant bone was almost identical with similar magnitudes for all designs. Increase in the horizontal set-off distance generated higher stress magnitudes and increased stress intensity within the implant-abutment complex.

: Platform switching based designs of implant-abutment connections need more mechanical studies to identify the optimum design for long-term mechanical stability.

Relocation of microgap and redefinition implant-abutment connection at bone level does not influence the stress characterization at periimplant marginal bone but may noticeably affect the mechanical properties of the implant-abutment connection.