Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
J Mech Behav Biomed Mater. 2011 Oct;4(7):1206-18. doi: 10.1016/j.jmbbm.2011.04.003. Epub 2011 Apr 15.
Porous titanium (pTi) can possess a low Young's modulus equal to that of human bone, depending on its porosity. However, the mechanical strength of pTi deteriorates greatly with increasing porosity. On the other hand, certain medical polymers exhibit biofunctionalities, which are not possessed intrinsically by metallic materials. Therefore, a biodegradable medical polymer, poly-L-lactic acid (PLLA), was used to fill in the pTi pores using a modified in-situ polymerization technique. The mechanical and biodegradable properties of pTi filled with PLLA (pTi/PLLA) as fabricated by this technique and the effects of the PLLA filling were evaluated in this study. The pTi pores are almost completely filled with PLLA by the developed process (i.e., technique). The tensile strength and tensile Young's modulus of pTi barely changes with the PLLA filling. However, the PLLA filling improves the compressive 0.2% proof stress of pTi having any porosity and increases the compressive Young's modulus of pTi having relatively high porosity. This difference between the tensile and compressive properties of pTi/PLLA is considered to be caused by the differing resistances of PLLA in the pores to tensile and compressive deformations. The PLLA filled into the pTi pores degrades during immersion in Hanks' solution at 310 K. The weight loss due to PLLA degradation increases with increasing immersion time. However, the rate of weight loss of pTi/PLLA during immersion decreases with increasing immersion time. Hydroxyapatite formation is observed on the surface of pTi/PLLA after immersion for ≥8 weeks. The decrease in the weight-loss rate may be caused by weight gain due to hydroxyapatite formation and/or the decrease in contact area with Hanks' solution caused by its formation on the surface of pTi/PLLA.
多孔钛（pTi）可以具有与人体骨骼相当的低杨氏模量，这取决于其孔隙率。然而，随着孔隙率的增加，pTi 的机械强度会大大降低。另一方面，某些医用聚合物具有生物功能性，而金属材料本身并不具有这些功能。因此，使用可生物降解的医用聚合物聚 L-乳酸（PLLA），采用改进的原位聚合技术填充 pTi 的孔隙。本研究评价了用该技术制备的填充 PLLA 的多孔钛（pTi/PLLA）的力学性能和生物降解性能，以及 PLLA 填充的影响。开发的工艺（即技术）几乎可以将 pTi 的孔隙完全填充 PLLA。PLLA 填充对 pTi 的拉伸强度和拉伸杨氏模量几乎没有影响。然而，PLLA 填充提高了具有任何孔隙率的 pTi 的压缩 0.2%屈服强度，并增加了具有较高孔隙率的 pTi 的压缩杨氏模量。pTi/PLLA 的拉伸和压缩性能之间的这种差异被认为是由于 PLLA 在孔隙中对拉伸和压缩变形的不同阻力造成的。在 310 K 的 Hank's 溶液中浸泡时，填充到 pTi 孔隙中的 PLLA 会降解。由于 PLLA 降解导致的重量损失随浸泡时间的增加而增加。然而，pTi/PLLA 在浸泡过程中的重量损失率随浸泡时间的增加而降低。在 pTi/PLLA 浸泡 8 周后观察到在其表面形成羟基磷灰石。重量损失率的降低可能是由于羟基磷灰石的形成而导致的重量增加，和/或由于其在 pTi/PLLA 表面形成而导致与 Hank's 溶液的接触面积减小。
