Effect of water aging on the apatite formation of a low-modulus Ti–7.5Mo alloy treated with aqueous NaOH

Enhancing Titanium Osteoconductivity by Alkali-Hot Water Treatment

Titanium and its alloys are essential in orthopedic and dental treatments owing to their high strength, corrosion resistance, and superior biocompatibility compared with those of other metals. However, titanium alloys are bioinert. Previous studies have indicated that alkali treatment (AT) is a straightforward method to create a surface oxidization layer on titanium, thereby improving its bioactivity. Herein, alkali-hot water pretreatment was used to enhance the osteoconductivity of titanium and to identify a simple and efficient means of enhancing the interaction between osteoblasts and implants for clinical applications. Commercial pure titanium plates were ground (CP Ti) and subjected to alkali solution and hot water treatments (AWT). Single-process CP Ti specimens were prepared via either AT or hot water treatment (WT). Network-like structural features were observed in the AT specimens and were further refined and densified in the AWT specimens. Water contact angle testing revealed that the hydrophilicity of the titanium specimen (80° for CP Ti) increased by 19° for the AT specimens but decreased by 59° for the AWT specimens. Mouse preosteoblasts (MC3T3-E1 cells) were used for in vitro evaluation. After 24 h of culturing, the number of attached MC3T3-E1 cells on the AWT specimens was 1.5 times larger than that on the CP Ti specimens, suggesting that the alkali-hot water treatment enhanced the initial cell attachment. Cell proliferation evaluation indicated that fewer cells were detected in the AT and AWT specimens compared with those in the CP Ti or WT specimens. However, osteogenic differentiation evaluation on day 10 revealed a 1.5-fold higher alkaline phosphatase expression in cells cultured on the AWT specimens than in cells cultured on the CP Ti specimens. These findings demonstrate the good cytocompatibility and osteoconductivity of AWT Ti, highlighting its benefits in orthopedics and dental treatments.

Fabrication and characterization of porous Ti-7.5Mo alloy scaffolds for biomedical applications

Porous titanium and titanium alloys are promising scaffolds for bone tissue engineering, since they have the potential to provide new bone tissue ingrowth abilities and low elastic modulus to match that of natural bone. In the present study, porous Ti-7.5Mo alloy scaffolds with various porosities from 30 to 75 % were successfully prepared through a space-holder sintering method. The yield strength and elastic modulus of a Ti-7.5Mo scaffold with a porosity of 50 % are 127 MPa and 4.2 GPa, respectively, being relatively comparable to the reported mechanical properties of natural bone. In addition, the porous Ti-7.5Mo alloy exhibited improved apatite-forming abilities after pretreatment (with NaOH or NaOH + water) and subsequent immersion in simulated body fluid (SBF) at 37 °C. After soaking in an SBF solution for 21 days, a dense apatite layer covered the inner and outer surfaces of the pretreated porous Ti-7.5Mo substrates, thereby providing favorable bioactive conditions for bone bonding and growth. The preliminary cell culturing result revealed that the porous Ti-7.5Mo alloy supported cell attachment.