Load transfer in tilted implants with varying cantilever lengths in an all-on-four situation

The aim of this study was to evaluate if tilting of the distal implant at different angulations (30° and 40°) with different cantilever lengths (4 mm and 12 mm) affects the stress and strain distribution in an 'all-on-four' situation.

A completely edentulous mandible was modelled with four tapered implants placed within the interforaminal region to receive an all acrylic fixed prosthesis. The two posterior implants were tilted at an angle of 30° and 40°. The prosthesis cantilever was given two different variables of 4 mm and 12 mm. For all models, the equivalent von Mises stress and strain was analysed using three-dimensional finite element analysis.

Statistical significance (p < 0.05) was seen when a comparison was made for the stress developed on the implant and cortical bone between the 30° and 40° distally tilted posterior implants in both situations. No significance was seen in the trabecular bone and on the strain developed in these situations.

The study shows that increasing the tilt of the distal implants does not increase the stress significantly. It also shows that the architecture of the mandible plays a major role during treatment planning of a completely edentulous patient.