Stress distribution and bone deformation around narrow-diameter implants at different placement depths and in different bone densities.

This study evaluated the biomechanical behavior of narrow-diameter Morse taper implants (3.5 mm) placed in bone of different densities and at different depths, using finite element analysis. Sixteen three-dimensional virtual models, meshed with tetrahedral elements, were created. Each model comprised cortical bone, cancellous bone, a Morse taper implant, an abutment, and a single maxillary central incisor crown. An oblique force (30 degrees buccally) of 150 N was applied to evaluate peri-implant stress distribution across four bone densities (D1, D2, D3, and D4) and at four placement depths (0, 1, 2, and 3 mm). The interfaces were modeled as perfectly bonded, except at the implant-abutment interface (friction coefficient = 0.3). All materials were assumed to be linearly elastic and isotropic. After a nonlinear analysis, the maximum and minimum principal stresses, maximum principal strain, and Mohr-Coulomb ratio were recorded. The results revealed a stress distribution pattern with lower peak stress values at shallower placement depths and in D1 bone. All groups showed a similar trend: as the implant placement depth increased, the point of greatest stress concentration shifted apically. Implant placement in cortical bone provided a protective effect under oblique loads. In D3 and D4 bone types, crestal placement showed better biomechanical performance than subcrestal placement.