Fatigue behaviour of the chemically treated titanium grade 4 implant material

Abstract

As-received and sand-blasted commercially pure titanium plates were chemically treated in alkaline and hydogen peroxide solutions in order to improve osseointegration. Both surface modification methods were carried out under optimum conditions stated in the literature. The samples were subjected to a bending cyclic loading under a stress amplitude of 250 MPa and R=0. The fatigue life of the as-received samples decreased from 4.105 to 2.105 due to surface roughening effect of the surface treatments. On the other hand, sand blasting increased the fatigue life of the sample significantly, although it also increased the surface roughness. The reason is the blasting induced deformation and in turn compressive stresses in the surface vicinity. Chemical treatments applied did not affect the surface roughness of the sand blasted samples. However the fatigue life of the sand blasted samples decreased drastically after chemical treatment. Chemical surface treatments are generally accompanied by a post heat treatment. The decrease in the fatigue life of the sand blasted plates is stemmed from stress relieving effect of the post heat treatment. As a result surface modification methods applied for bioactivity should be also evaluated with respect to its effects on the fatigue performance of the material. The process parameters of the chemical surface treatment should be optimized taking into the account the fatigue life of the implant.