Influence of marginal bone resorption on stress around an implant--a three-dimensional finite element analysis.

Average marginal bone resorption of about 1 mm after the first year of functional loading, which is followed by an annual loss of approximately 0.1 mm, has been reported in stable implants. However, finite element analyses on bone stress around implants have been limited to analysing the bone stress in the absence of any bone resorption. Thus, a three-dimensional finite element analysis was performed to compare the bone stresses in a non-resorption model with those in four models with bone resorption of two depths (1.3 and 2.6 mm) and types (horizontal resorption and angular defects). Axial and bucco-lingual forces were separately applied to the center of the superstructure and the maximum equivalent stress was calculated. The main tendencies of bone stress (highest stress concentration around implant neck, higher stresses under bucco-lingual than axial load, as well as in the cortical than cancellous bone) were the same in the non-resorption and resorption models. Bone stress distributions were similar in the non-resorption and horizontal resorption models, but differed from those in the angular defect models. Moreover, the changes of the bone stress values with resorption depth differed for the two resorption types. Thus, in FEA, accurate simulation of the marginal bone shape in the implant neck region is advisable.