Enhanced Osseointegration of Functionally Graded Co˗Cr˗Mo˗Ti/HA Implants: In Vitro and In Vivo Study in a Rabbit Model
Abstract
The present investigation aims to evaluate the effects of acid and laser surface treatments on the surface characteristics, biocompatibility, and osseointegration of functionally graded implants fabricated from a Co–Cr–Mo–Ti/HA alloy. The implant surfaces were modified using either an Nd: YAG laser or hydrochloric acid (HCl), while untreated implants served as controls. Atomic force microscopy (AFM) showed that the acid-treated surface exhibited the highest mean surface roughness (Sa) of 58.10 ± 0.24 nm compared to the laser-treated surface (42.64 ± 0.83 nm) and the untreated surface (37.73 ± 0.89 nm). The MTT assay also demonstrated a favourable cellular response on the acid-treated surface, with 98.31 ± 2.91% cell viability. Histological examination of the acid-treated implants revealed increased new bone formation, greater osteoblast activity, more organised trabecular bone, and closer bone–implant contact than observed in the control group. Biochemical analyses resulted in no treatment-related toxicity or pathological alterations in the investigated biomarkers. These results indicate that both acid and laser treatments improved the surface and biological performance of the implants relative to the untreated condition. Among the investigated treatments, acid treatment produced the greatest surface roughness and the most favourable cellular and histological responses. It therefore appears to be the more effective surface-modification method under the experimental conditions of this study. Tests on the Co–Cr–Mo–Ti/HA implant polished with acid etching showed a significant improvement in surface roughness, providing a fine nanostructure suitable for bone cell attachment and proliferation. In vitro MTT tests clearly showed that bone cells interacted much more actively and vigorously compared to the untreated control group (p < 0.05). Additionally, biochemical analysis results showed that liver and kidney function markers remained unchanged, indicating excellent biocompatibility, readiness, and high vitality of the developed implant.