Guidelines for analysis and redesign of dental implants

This article describes the simulation of the mechanical behavior of two types of endosseous-threaded dental implants and the development of design guidelines for such implants. Two- and three-dimensional representations, static and dynamic cyclic loads, different material models, axial loads, and loads directed at the occlusal angle are all used. A novel model of trabecular bone is used to incorporate fatigue effects. Directional material behavior, progressive bone loss, and partial osseointegration are also modeled. Bone support using muscle attachment is modeled using spring constraints as opposed to fixed constraints used in previous studies. The tapered thread design from Brånemark Inc. exhibited higher stress levels in bone than those observed in the parallel profile thread from BUD Medical Devices, Inc. The BUD implant distributes stresses more evenly. Studies examining 25%, 75%, and 100% osseointegration showed cortical bone carried most of the load with resulting overload leading to crestal bone loss. Plots of stress showed that with increasing crestal bone loss, the majority of the load was transferred directly to the weaker trabecular bone tissue. Finally, it was shown that with proper implant redesign, loads can be transferred more evenly to the implant. This also improves fatigue life of the bone.