Effects of different inter-implant distances on the stress distribution around endosseous implants in posterior mandible: A 3D finite element analysis

The aim of this study was to evaluate the effects of different inter-implant distances on stress distribution in the bone around the endosseous titanium implants under vertical, oblique and horizontal loads in the posterior mandibular edentulousim by finite element analysis (3D FEA). 3D FEA models representing mandible and ITI ® implant (Straumann, Waldenburg, Switzerland) were simulated. The distances in-between the units were set at 0.5, 1.0 and 2.0 cm. Vertical (V) 70°N, 60° oblique (BL) 35°N in buccolingual direction and horizontal (MD) 14°N in mesiodistal direction loads were applied to each of these designs. The principal stresses (tensile and compressive stress) on each model were calculated using MSC MARC finite element analyze solver software. The tensile stress ( P max) values have been evaluated that they rose at the cervical region of buccal side when the inter-implant distances increased under V and BL loads and they diminished while the inter-implant distances decreased. In short inter-implant distances the compressive stress ( P min) has been presented with increased values and found at the lingual surface of the cervical region. The results of this study indicated that the magnitude of the stress was influenced by complex factors such as the direction of loads and the distance between adjacent fixtures. The stress occurring around fixtures differs significantly with various types of inter-implant distance. The evaluation of tensile and compressive stresses for cortical and cancellous bone under V, MD and BL loading conditions in aspect of inter-implant distance shows; the 1.0 cm of inter-implant distance is the optimum distance for two fixture implantation.