Micromechanics of implant/tissue interfaces

A series of finite element models was developed for evaluation of the micromechanics of implant/tissue interfaces. Conventional finite element global models of a dental implant, assuming a continuum implant/bone interface, were developed so that general stress patterns in the implant and surrounding tissue could be obtained. Stresses in bone were concentrated on the alveolar crest and apex region for all global models having a direct bone/implant contact. The addition of a 100-microns-thick layer of fibrous tissue into the bone/implant interface concentrated the stresses in the middle third of the bone adjacent to the implant surface. Stresses in the middle third were ten times higher than in the cases without fibrous tissue. Interfaces modeled under the assumption of a volume-weighted average material stiffness of bone tissue and metal confirmed these general stress patterns, but provided no stress details of the interfacial zone. Finally, the equivalent material constants of the interfacial zone with and without fibrous tissue were calculated by homogenization theory. From these equivalent constants, local strains around single threads were calculated. These equivalent material properties are sensitive to the microstructure. Therefore, it is now possible for stress patterns within the interfacial zone to be quantified and the local micromechanical behavior around individual surface structures for whole implants accounted for.