Analysis of Occlusal Stresses Transmitted to the Inferior Alveolar Nerve by Multiple Threaded Implants

Background: Potential nerve injury or loss of sensation can occur after mandibular implants placement or loading. To determine the proper distance from implants to the mandibular is critical nerve to avoid this type of damage. Hence, the purpose of this study was using biomechanical analyses to determine the safety distance from multiple implants to the inferior alveolar nerve. Material and Methods: Boundary Element Method, a numerical mandibular model, was designed to simulate a mandibular segment containing multiple threaded fixtures. This model allows us to assess the pressure, as induced by occlusal loads, on the trigeminal nerve. Such pressure distribution was evaluated against different distances from the fixtures to the mandibular canal, against the possible lack of the central fixture in a three-abutment configuration and against different levels of implant osseointegration. All the simulations considered a canal that is orthogonal to the implant axis. Results: The nerve pressure increased quickly when the implant-canal distance decreases in the range studied. The lack of the central implant to support the central abutment causes the major nerve pressures increase. Conclusions: Our study suggested a minimal implant-canal distance of 1 mm, in order to prevent inferior alveolar nerve damages caused by three connected implants. For clinical safety, we added an additional 0.5mm as a cushion so 1.5mm minimal distance should be planned to avoid any potential nerve injury.