Finite Element Stress and Strain Analysis of the Bone Surrounding a Dental Implant: Effect of Variations in Bone Modulus

Abstract
The long-term clinical performance of a dental implant is dependent upon the preservation of good quality bone surrounding the implant and a sound interface between the bone and the biomaterial. Good quality bone is itself dependent upon the appropriate level of bone remodelling necessary to maintain the bone density and the avoidance of bone microfracture and failure. Both processes are governed by the stress and strain distribution zn the hone. In this study, a dental implant which had the same geometry as the Branemark system, but with a bioactive surface coating added to produce a direct bond to the bone, was analysed. Ajinite element stress and strain analysis has been carried out for a range of bone density distributions under axial and lateral loading. The predictions indicated that there was no evidence of strain shielding around the neck of the implant. With lateral loading, high values of von Mises stresses (18 MPa) were predicted around the neck of the implant. A reduction in the elastic modulus of the bone around the neck of the implant by a factor of 16 only produced a twofold reduction in the peak stress. This resulted in stress levels capable of inducing fatigue failure in this much weaker bone. This analysis has demonstrated that it is extremely important to have good guality dense bone around the neck of the implant to withstand the predicted peak stresses of betweeen 9 and 18 MPa. Failure to achieve this ufter implantation and subsequent healing may result in local fatiguefailure and resorption at the nrck upon resumption of physiological loading.

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