The Influence of Nanostructured Hydroxyapatite Surface in the Early Stages of Osseointegration: A Multiparameter Animal Study in Low-Density Bone.

Background and Objective The success rates of dental implants in low-density bone have been reported as a challenge, especially for early or immediate loading in the maxilla posterior area. Nanoscale architecture affects the roughness, surface area, surface energy of the implant and can enhance osseointegration. This study aimed to evaluate the implant-surface topography and biomechanical, histomorphometric, and histological bone responses to a new nanostructured hydroxyapatite surface placed in the iliac crest of sheep. Methods Ten female sheep (2-4 years) received 30 implants (n=10/group): HAnano® coated (Epikut Plus®, S.I.N. Implant System, Sao Paulo, SP, Brazil), SLActive (BLX®, Straumann, Basel, Switzerland), and TiUnite (NobelActive®, Nobel Biocare, Goteborg, Sweden) surfaces. Scanning electron microscopy with energy-dispersive spectroscopy evaluated the implant surface topography, the insertion torque value, and resonance frequency analysis evaluated the primary stability, bone-implant contact, and bone-area fraction occupancy were evaluated after 14 and 28 days after implant placement. Results The surface morphology was considerably comparable between the implant groups'; however, the TiUnite® group presented a remarkable different surface. The SLActive® and TiUnite® groups presented an insertion torque average of 74 (±8.9) N/cm that was similar to that of HAnano® 72 (±8.3) N/cm (p >0.05). The resonance frequency evaluated with Osstell®/SmartPeg® or Penguin®/MulTipeg® showed similar results when assessing implants from the same group. BIC and BAFO significantly increased (p<0.05) throughout the experimental periods to all groups, but BIC and BAFO values were similar among the implants at the same time point. After 4 weeks, bone-implant contact was higher than 80% of the total length analyzed. New bone occupies around 60% of analyzed area around the implants. Conclusion HAnano® coated surface promoted comparable osseointegration as SLActive and TiUnite in the sheep model. The three tested surfaces showed comparable osseointegration at the early stages of low-density bone repair in the sheep model.