Investigation of bone inelastic response in interaction phenomena with dental implants

The aim of the paper is to analyze the effects of misfits in multi-implant oral prostheses caused by defects in manufacturing of bar connecting implants. The consequent stress-strain state on peri-implant bone tissue must be carefully considered because of the significant effects induced.

The case of a two-implant prosthesis connected by a titanium cast bar in the pre-molar mandible region is investigated. The complex geometry requires the use of refined finite element model. In consideration of the action induced on the bone tissue, a specific constitutive model that includes inelastic behavior is implemented. The linear misfits considered, estimated with reference to experimental works already present in the literature, induce relevant strains in the peri-implant bone tissue up to a post-elastic phase. Relaxation phenomena are also evaluated. The interaction between the bone and implant is modeled by using contact elements to represent possible detachments at the bone-implant interface.

The response of the bone material is reported with regard to the stress/strain field induced, evaluating the inelastic behavior in terms of plastic and relaxation responses. The effects on the peri-implant bone tissue at the interface are evaluated.

The analysis confirms that the interaction phenomena between the multi-implant oral prostheses and bone induced by the misfit defects of normal intensity induce significant strain in the bone tissue and inelastic phenomena must be taken into account. Local permanent strains of bone tissue and relaxation phenomena represent short-term tissue response for a correct interpretation of the real biomechanical behavior of multiple implant frames.