Micromotion analysis of different implant configuration, bone density, and crestal cortical bone thickness in immediately loaded mandibular full-arch implant restorations: A nonlinear finite element study.

Abstract

Excessive micromotion may cause failure of osseointegration between the implant and bone. This study investigated the effects of implant configuration, bone density, and crestal cortical bone thickness on micromotion in immediately loaded mandibular full-arch implant restorations. A finite element model of the edentulous mandible was constructed. Four implants were inserted in two different configurations, which were four parallel implants or tilted distal implants according to the all-on-four concept. Different cancellous bone densities and crestal cortical bone thicknesses were simulated. The framework was made of acrylic resin. A vertical load of 200 N was applied at the cantilever or on the distal implant (noncantilever loading). The maximum extent of micromotion was significantly influenced by the density of cancellous bone and to a lesser extent by implant configuration and the crestal cortical bone thickness. The all-on-four configuration showed less micromotion than the parallel implant configuration in some circumstances. The maximum micromotion detected with noncantilever loading was less than 1/3 of that with cantilever loading. Implant configuration had a limited influence on micromotion. Avoiding cantilever loading during the healing period should effectively reduce the risk of excessive micromotion in patients with low-density cancellous bone and thin crestal cortical bone.