The finite element method (FEM) makes it possible to simulate biomechanical
situations on a computer. In the present study the so-called voxel method
[9, 14, 17, 18, 19] was used for the construction of the mandible model. Fo
r this, the relationship between the biological tissue (e.g. bone) and the
corresponding attenuation coefficient of CT data (Hounsfield units = HU) we
re utilized. The CT data were obtained from an edentulous patient provided
with a prosthesis borne on two titanium implants.
In a parallel study, the bite forces of the same individual were measured.
These were recorded digitally in three dimensions (cranio-caudal, anterior-
posterior and left-right) The forces determined by a special program were t
hen transferred to the FEM model implants. We were able to show that a bar
joining the implants had a far greater effect on maximum equivalent stress
than was expected from the measuring data alone. The highest stress at maxi
mum occlusive force was lowered by 704 % on using the connecting bar. On ch
ewing, a stress reduction of 59.9 % was observed. The reduction in stress a
chieved by the bar could, we believe, prolong the life of the implant.