Biomechanical finite element analysis of small diameter and short dental implants: extensive study of commercial implants.

In recent years, mini and short dental implants have become increasingly popular as treatment alternatives for patients in whom the bone is unsuitable for a standard implant. As yet, no detailed scientific analysis of the mechanical and biomechanical impact of the reduced diameter and length of these implants has been published. We analysed 21 commercially available implants (13 mini, eight short) with respect to material behaviour and load transfer to the alveolar bone, using finite element (FE) analysis. Following μCT scanning and geometry reconstruction, FE models of mini implants and short implants were inserted into idealised bone segments. Mini implants were analysed in the anterior mandibular jaw region at a force of 150 N under immediate loading, using a contact analysis in the FE software package Marc Mentat 2007. Short implants were inserted in posterior bone segments and analysed in the osseointegrated state at an occlusal force of 300 N. Von Mises stresses (up to 1150 MPa) in mini implants partly exceeded the ultimate strength. Implant diameter and geometry had a pronounced effect on stresses in the cortical plate (up to 266 MPa). Strains in spongy bone and stresses in cortical bone around short implants were markedly increased compared to those in standard implants. An increased risk of bone damage or implant failure may be assumed in critical clinical situations.