Fatigue Life of Bioactive Titanium Dental Implants Treated by Means of Grit-Blasting and Thermo-Chemical Treatment

Objective: This study focuses on the fatigue behavior of titanium dental implants as-received, with a grit-blasted surface and with a new bioactive surface treatment (2Steps). Background: The 2Step process consists of (1) an initial grit-blasting process to produce a micro-rough surface, followed by (2) a combined thermo-chemical treatment that produces a potentially bioactive surface, that is, that can form an apatitic layer when exposed to biomimetic conditions in vitro. The 2Step treatment produced micro-rough and apatitic coating implants. Methods: Residual stresses were determined by means of X-ray diffraction. The fatigue tests were carried out at 37 degrees C on 500 dental implants, and the S-N curve was determined. The fatigue-crack nucleation for the different treatments was analyzed. Results: The fatigue tests show that the grit-blasting process improves the fatigue life. This is a consequence of the layer of compressive residual stresses that the treatment generates in titanium surfaces. Dental implants that had its surfaced prepared with the 2Step procedure (grit-blasting and thermo-chemical treatment) had its fatigue life decreased by 10% due to the incorporation of oxygen to the surface and the relaxation of the compressive residual stress produced by the heat treatment. Conclusions: Thermo-chemical treatment is an excellent compromise between the improvement of bioactive and mechanical long-life behaviors.