Stress distribution in the single-unit osseointegrated dental implant: finite element analyses of axial and off-axial loading.

Occlusal overload may contribute to the extensive crestal bone loss often noted around late-failure dental implants. A particularly high risk of traumatic overload occurs with the posterior single-unit implant restoration because the restoration itself is usually wider than the implant, creating the potential for a cantilever effect with high bending moments. The objective of this study was to evaluate the simulated effects of axial and off-axial vertical loads on stress gradients at the implant/bone interface of a single-unit osseointegrated root-form endosseous dental implant. A two-dimensional finite element model was generated. A 490-N load was applied at 0, 2, 4, and 6 mm from the vertical axis of the implant. Off-axis loading resulted in greatly increased compressive stresses within the crestal cortical bone on the side to which the load was applied and similarly increased tensile stresses on the side opposite the load. These stresses increased considerably with each mm increase off axis of the applied load. These data suggest that off-axis loading of single-unit implant restorations provides a significant contribution to increased stresses at the implant/cortical bone interface. The distance off axis at which the load is applied is also significant.