Biomechanical investigations of the secondary stability of commercial short dental implants in porcine ribs.

The use of short implants has increased widely within the last years. However, the stability of these implants has not yet been comprehensively investigated, in particular the difference in geometry and dimension of short implants. The aim of the present study was to investigate experimentally the difference of the secondary stability of different commercial short implants by measuring their displacements. Eleven implant geometries were investigated in this study. A total of 22 implants were inserted in porcine rib segments, two implants for each system. Implant displacements were measured using a self-developed biomechanical hexapod measurement system (HexMeS). The highest displacement was observed with Straumann BL NC 3.3x8.0 mm (266 mum), followed by Straumann Standard 4.1x6.0 mm (156 mum), while the lowest displacement of 61 mum was shown by Dentaurum type 1 implant (4.2x5.0 mm). No obvious difference of displacements was observed between hammered and screw-shaped implants with relevant dimensions. The experimental results were in good agreement with the numerical ones (19-42%) for Dentaurum implants. However, a difference of 70-80% was obtained for the Astra implant (4.0x6.0 mm) and Bicon implant (6.0x5.7 mm). The geometry of short implants directly affects their stability within the bone.