An in vivo interfacial gene expression model combined with biomechanical analysis was used in order to determine the relationship between the molecular events taking place during osseointegration and the biomechanical stability of the implant. Anodically oxidized and machined, threaded titanium implants were characterized topographically, chemically and ultrastructurally. The implants were inserted in rat tibiae and the implant bone torsion stability was evaluated. After measurements, the implants were removed and analyzed with qPCR. Results showed an increase in the breakpoint torque of 140%, 170% and 190%, after 6, 14, and 28 days, respectively, at the oxidized implants as compared to the machined. Gene expression analysis revealed higher expression of runt related transcription factor-2 (Runx2) (after 28 d), osteocalcin (OC) and tartrate resistant acid phosphatase (TRAP) (after 6, 14 and 28 d) and cathepsin K (CATK) (after 6 and 14 d) at the oxidized implants. On the other hand, machined implants were associated with higher expression of tumor necrosis factor-α (TNF-α) (after 6 and 28 d) and interleukin-1β (IL-1β) (after 6, 14 and 28 d) compared to the oxidized implants. In conclusion, the favorable cellular and molecular events at the oxidized implants were in parallel with significantly stronger bone anchorage during osseointegration.
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