FINITE-ELEMENT ANALYSIS OF CRESTAL BONE LOSS AROUND POROUS-COATED DENTAL IMPLANTS

Crestal bone loss is observed around various designs of dental implant s. A possible cause of this bone loss is related to the stresses actin g on periimplant bone. To investigate the relationship between stress state and bone loss, two-dimensional finite element models correspondi ng to bucco-lingual and mesio-distal sections of canine mandibles with one of two designs of porous-coated dental implants were analyzed. A fully porous-coated design consisting of a solid Ti6Al4V core had a po rous coating over the entire outer surface of the implant component, w hile a partially porous-coated design had the porous coating over the apical two-thirds of the implant surface only. Occlusal forces with ax ial and transverse components were assumed to act on the implant with interface bonding and effective force transfer at all porous coat-bone interfaces and no bonding for the non-porous-coated regions. The resu lts of the analysis indicated that at most implant aspects(buccal, lin gual, mesial, and distal), the equivalent stresses in crestal bone adj acent to the coronal-most, non-porous-coated zone of the partially por ous-coated implants were lower than around the most coronal region of the fully porous-coated implants. The region of lower stresses around the partially porous-coated implants corresponded to observed areas of crestal bone loss in animal studies, suggesting that crestal bone los s in this case was due to bone disuse atrophy. A number of parameters of the finite element models were varied to determine the effect on th e resulting stress fields and, therefore, possible long-term bone remo deling. Based on differences in observed bone structures by histologic al examination and results of finite element analyses with fully and p artially porous-coated implants, an equivalent stress equal to 1.6 MPa was determined to be sufficient to avoid bone loss due to disuse atro phy in the canine mandibular premolar region. (C) 1995 John Wiley & So ns, Inc.