Simulation of Impact Test for Determining “Health” of Percutaneous Bone Anchored Implants

Abstract

There is an ongoing requirement for a clinically relevant, noninvasive technique to monitor the integrity of percutaneous implants used for dental restorations, bone-anchored hearing aids, and to retain extra-oral prostheses (ear, eye, nose, etc). Because of the limitations of conventional diagnostic techniques (CT, MRI), mechanical techniques that measure the dynamic response of the implant-abutment system are being developed. This paper documents a finite element analysis that simulates a transient response to mechanical impact testing using contact elements. The detailed model allows for a specific interface between the implant and bone and characterizes potential clinical situations including loss of bone margin height, loss of osseointegration, and development of a soft connective tissue layer at the bone-implant interface. The results also show that the expected difference in interface stiffness between soft connective tissue and osseointegrated bone will cause easily measurable changes in the response of the implant/abutment system. With respect to the loss of bone margin height, changes in the order of 0.2 mm should be detectable, suggesting that this technique is at least as sensitive as radiography. A partial loss of osseointegration, while not being as readily evident as a bone margin loss, would still be detectable for losses as small as 0.5 mm.

Dental implant induced bone remodeling and associated algorithms

“…Furthermore, their study showed that the relationship between the bone density and stress in the bone surrounding the implant is inversely proportional to each other, which means that, as the bone density decreases, the mechanical stresses in the surrounding bone increases. To model different interfacial conditions between the implant and bone, Jones et al (2006), develop contact elements by correlating the modeling to the measured dynamic responses. In a more recent study, Perez et al (2008) developed a phenomenological interface model to simulate the mechanical effects of the osseointegration process at the bone-implant interface by correlating with experimental results in rabbits, where a significant increase in resonance frequency was obtained as positive osseointegration progresses.…”