Stress state near dental implants accounting bone tissues resorption

Abstract

The results of numerical modeling by the boundary integral equations method (BIEM) of the effect of bone tissues resorption on the stress state near screw dental implants under action of normal and inclined compressive loads are presented. The direct version of the BIEM for piecewise homogeneous sub-regions is used. The computation of the implant and the surrounding bone tissues stresses was carried out for plane strain state,  assuming the complete bonding of materials at the interface of the implant and bones (osteointegration) and consisted of two stages: 1) analysis of the entire implant structure with smoothed screw join between implant and the surrounding bone tissues; 2) studies of stress distribution taking into account the shape of the screw join of the implant and bone tissues. The model of the first stage of computations consisted of 7 sub-regions corresponding to the parts of the implant structure and bone tissues zones. On the second stage of computations it was assumed that those hollows in the spongy bone, which had formed in a bone after implant penetration, are conformed to the screw thread on the implant. The effect of bone tissues resorption on stresses concentration  in the screw join of implants  and spongy bone tissue is considered. The creating of  computation models was performed on the assumption that the result of bones resorption is the cavity formation around implants. The computations were performed under the assumption that the bone tissues are isotropic and homogeneous elastic materials.  It was found that as a result of resoprtion, there is a significant stresses redistribution in bone tissues and the implant with maximum equivalent stresses decreasing in the cortical bone tissue and increasing in spongy bone tissue. The results are presented as the distributions of stress intensity along the sub-regions boundaries  of the computational model.

Keywords

• implant
• screw joint
• bone tissues resorption
• method of boundary integral equations
• stress-strain state
• stress concentration