The effect of annealing and surface topography on the mechanical stability of TiO₂ nanotubes on titanium implants during insertion test.

Abstract

While titanium dioxide (TiO₂) nanotubes are widely recognized for enhancing the osseointegration of dental implants, their clinical translation is severely hindered by poor mechanical stability, often leading to coating detachment during surgical insertion. Addressing this critical limitation, this study aimed to optimize the adhesion of TiO₂ nanotubes through annealing and to evaluate the protective role of substrate topography during simulated implantation. Nanotubes were grown via anodization on both machined and Sandblasted, Large-grit, Acid-etched (SLA) titanium substrates, followed by annealing from 300 °C to 700 °C. Results indicated that annealing at 500 °C provided the optimal balance of anatase crystallinity and adhesion stability, yielding the highest adhesion strength. However, simulated insertion tests revealed that high adhesion alone is insufficient; nanotubes on smooth machined surfaces suffered extensive delamination due to shear forces. In contrast, the SLA substrate demonstrated a unique mechanical shielding effect, where intrinsic micro-cavities effectively protected the nanotubes from abrasive friction. The study concludes that combining SLA surface topography with 500 °C annealing creates a synergistic defense, preserving the bioactive coating's integrity against insertion torques and overcoming the primary mechanical barrier to the clinical application of nanostructured implants.