Selective laser melting (SLM) of commercially pure titanium inherently yields a highly porous, rough surface (Ra ≈ 5 µm) because partially melted powder particles solidify in place. In this work SLM‑Ti was bioactivated by a mixed‑acid and heat (MAH) treatment: immersion in an H₂SO₄/HCl mixture followed by annealing at 600 °C.
Surface Morphology & Chemistry
SEM & roughness: Mixed‑acid etching created micro‑pores and raised surface roughness to Ra ≥ 8.6 µm.
Phase transformation: Subsequent annealing converted the outermost layer from titanium hydride to positively charged rutile TiO₂.
Wettability & apatite formation: Water contact angle plummeted from 95° to < 1°. Complete hydroxy‑apatite coverage formed within 1 day in simulated body fluid (SBF), indicating strong osteoconductivity.
Biological Response (MC3T3‑E1 Pre‑osteoblasts)
Early adhesion & proliferation: Cells bridged interparticle gaps within 0.5 h, and three‑day proliferation surpassed that on untreated SLM‑Ti and mirror‑polished cp‑Ti.
Differentiation markers: On the MAH surface alkaline‑phosphatase (ALP) activity surged on days 10–14; mineralized nodules peaked on day 21. RT‑PCR showed significant up‑regulation of Alp, Runx2, Ocn, and Opn.
Signaling pathways: Expression of Wnt/β‑catenin components and cyclin D1 (proliferation marker) also increased, suggesting cooperative activation by the rough topography and positively charged rutile layer.
Significance
Combining patient‑specific geometry (via SLM) with MAH bioactivation enables implants that not only match complex bone defects but also chemically bond to bone early and actively promote osteoblast differentiation and mineralization. Among advanced oxidized Ti surfaces in clinical use, this approach uniquely merges design freedom with high osteo‑inductive potency, offering strong potential for next‑generation custom orthopedic and dental implants.
Article information & citation
Seiji Yamaguchi, Phuc Thi Minh Le, Seine A. Shintani, Hiroaki Takadama, Morihiro Ito, Sara Ferraris, Silvia Spriano. Bioactivation Treatment with Mixed Acid and Heat on Titanium Implants Fabricated by Selective Laser Melting Enhances Preosteoblast Cell Differentiation. Nanomaterials, 11(4), 987, 2021.