Analysis of the occlusal stress transmitted to the inferior alveolar nerve by an osseointegrated threaded fixture

Background: Altered sensation can occur after the placement or loading of mandibular implants. Limited evidence exists with regard to the proper distance between the implant and the mandibular nerve to ensure the nerve's integrity and physiologic activity. The proper distance should come from evaluation of clinical data as well as from biomechanical analyses. Methods: A numeric mandibular model based on the boundary element method was created to simulate a mandibular segment containing a threaded fixture so that the pressure on the trigeminal nerve, as induced by the occlusal loads, could be assessed. Such pressure distributions were evaluated with different distances of the fixture from the mandibular canal and considering different bone densities. Although all simulations considered a canal that was orthogonal to the implant axis, in one case, the effects of an inclined canal were analyzed. Results: The nerve pressure increased rapidly with a bone density decrease. A low mandibular cortical bone density caused a major nerve pressure increase. Conclusion: Our study suggested a distance of 1.5 mm to prevent implant damage to the underlying inferior alveolar nerve when biomechanical loading was taken into consideration.