Effects of different fixture geometries on the stress distribution in mandibular peri-implant structures: a...

The purpose of this study was to compare 3 different solid screw implant fixture designs of stepped cylindric tapered, straight cylindric nontapered, and cylindric with vertical groove tapered on stress distribution in the posterior mandible at a fixed interimplant distance of 1.0 cm.

Three-dimensional finite element analysis was used to compare stress distribution around the endosseous titanium implants using 3 different implant fixture geometries. Two identical dental implants of 3 commercially available fixture designs were embedded in each model with a fixed interimplant distance of 1.0 cm. Loads were applied to each of these fixtures: vertically 70 N, with an inclination of 60 degrees obliquely (buccolingually) 35 N, and horizontally (mesiodistally) 14 N. Tensile and compressive stresses on each simulated mandible were calculated using finite element analysis software. Finally, evaluation of the stress around 3 different implant fixtures was performed.

In the vertical and buccolingual directions, the highest tensile stresses (P(max)) and compression stresses (P(min)) mostly occurred around the cylindric with vertical groove tapered fixture design in both cortical and cancellous bone. In mesiodistal direction, the highest P(max) and P(min) values in cortical and cancellous bone mostly occurred around the straight cylindric nontapered fixture design.

On the basis of the knowledge of deterioration of osseointegration under undesirable stresses within the surrounding bone, the implant fixture design should be chosen carefully. The results of this study reveal that in a clinical situation of molar edentulism, 2 identical stepped cylindric fixture designs which were embedded at a fixed distance of 1.0 cm were the most desirable choice of stress distribution in the surrounding bone.