Finite element stress analysis of the influence of staggered versus straight placement of dental implants

Bending moments resulting from non-axial overloading of dental implants may cause stress concentrations exceeding the physiologic supporting capacity of cortical bone, leading to various kinds of failures. The aim of this stu dy was to evaluate the effect of staggered (offset, tripodization) implant placement configuration and placement of wider-diameter implants in a strai ght-line configuration in mandibular posterior edentulism. A mandibular Ken nedy Class II partially edentulous finite element model was constructed. Se ven different partial fixed prostheses supported by 3 implants were designe d according to 2 main configurations: straight-line or staggered implant pl acement. In 5 of the designs, implants with various diameters and length we re placed along a straight line. In the other 2 models, offset placement of the middle implant buccally and lingually was simulated. A 400 N static lo ad was applied perpendicular to the buccal inclination of the buccal cusps on each unit. Tensile and compressive stress values on cortical bone in the cervical region of the implants were evaluated. Lower stress values were r ecorded for the configuration with wider implants placed in a straight line . Other configurations, including staggered implant placement, produced sim ilar stress values. Despite the offset implant placement, the stresses were not decreased, however, straight placement of wider implants may decrease bending moments.