Young-Taeg Sul, Byung-Soo Kang, Carina B Johansson, Tomas Albrektsson
Nanoimprinted SLA implants exhibited enhanced early interfacial biomechanics and qualitative bone response compared with SLActive. RTQ-rotation analysis revealed exploratory differences in interface stiffness, toughness, and failure resistance not detected by conventional peak torque measurement alone. Within the limitations of this 3-week rabbit model, these findings suggest that hydrophilic microtopography may not represent the biological limit of early osseointegration and that hierarchical NIM architecture combined with biofunctional chemistry may promote early bone-implant integration.
PURPOSE: To evaluate whether hierarchical nano-in-micro (NIM) architecture combined with biofunctional chemistry enhances early osseointegration compared with a hydrophilic SLActive surface and to characterize interfacial biomechanics using a newly developed continuous removal torque-rotation (RTQ-rotation) analysis system.
MATERIALS AND METHODS: Nanoimprinted SLA implants incorporating pit-confined NIM architecture and amine/carboxyl (-NH₂/-COOH) functional groups were compared with SLActive implants in a paired rabbit femoral model after 3 weeks (n = 11). Surface morphology and chemistry were analyzed by SEM/FE-SEM and XPS. The RTQ system continuously recorded torque versus rotation angle to assess interfacial strength and exploratory descriptors of stiffness, toughness, and failure behavior.
RESULTS: Conformal NIM architectures (10-80 nm) with biofunctional surface chemistry were imprinted within pre-existing micropits of SLA, SLActive, TiUnite, OsseoSpeed, and TSIII SA surfaces while preserving original microtopography. Nanoimprinted SLA implants demonstrated significantly higher removal torque than SLActive controls (84.1 ± 8.2 Ncm vs 65.1 ± 10.0 Ncm; p = 0.002). RTQ-rotation analysis revealed approximately 75% higher interfacial stiffness (3.96 vs 2.26 Ncm/degree), faster torque engagement (75.6 Ncm at 19.1-degree rotation), and increased resistance to progressive interfacial failure. Qualitative histology demonstrated more continuous early bone formation along nanoimprinted implant surfaces.
CONCLUSIONS: Nanoimprinted SLA implants exhibited enhanced early interfacial biomechanics and qualitative bone response compared with SLActive. RTQ-rotation analysis revealed exploratory differences in interface stiffness, toughness, and failure resistance not detected by conventional peak torque measurement alone. Within the limitations of this 3-week rabbit model, these findings suggest that hydrophilic microtopography may not represent the biological limit of early osseointegration and that hierarchical NIM architecture combined with biofunctional chemistry may promote early bone-implant integration.