Department of Mechanical Engineering and Engineering Science, The University of North Carolina at Charlotte, Charlotte, North Carolina 28223, USA.
J Biomed Mater Res B Appl Biomater. 2012 Aug;100(6):1545-55. doi: 10.1002/jbm.b.32723. Epub 2012 Jun 12.
Bioactive ceramics bond to bone and enhance bone formation. However, they have poor mechanical properties which restrict their machinability as well as their application as load bearing implants. The goal of this study was to machine bioactive fixation screws using a silica-calcium phosphate nanocomposite (SCPC50). The effect of compact pressure, holding time, and thermal treatment on the microstructure, machinability, and mechanical properties of SCPC50 cylinders were investigated. Samples prepared by powder metallurgy technique at compact pressure range of 100-300 MPa and treated at 900°C/1 h scored a poor machinability rating of (1/5) due to the significant formation of amorphous silicate phase at the grain boundaries. On the other hand, lowering of compact pressure and sintering temperature to 30 MPa/3 h and 700°C/2 h, respectively, minimized the formation of the amorphous phase and raised the machinability rating to (5/5). The modulus of elasticity and ultimate strength of machinable SCPC50 were 10.8 ± 2.0 GPa and 72.8 ± 22.8 MPa, respectively, which are comparable to the corresponding values for adult human cortical bone. qRT-PCR analyses showed that bone cells attached to SCPC50 significantly upregulated osteocalcin mRNA expression as compared to the cells on Ti-6Al-4V. Moreover, cells attached to SCPC50 produced mineralized bone-like tissue within 8 days. On the other hand, cells attached to Ti-6Al-4V failed to produce bone mineral under the same experimental conditions. Results of the study suggest that machinable SCPC50 has the potential to serve as an attractive new material for orthopedic fixation devices.
生物活性陶瓷与骨骼结合并增强骨形成。然而，它们的机械性能较差，限制了其可加工性以及作为承重植入物的应用。本研究的目的是使用硅钙磷酸盐纳米复合材料（SCPC50）加工生物活性固定螺钉。研究了压缩压力、保温时间和热处理对 SCPC50 圆柱体的微观结构、可加工性和力学性能的影响。在 100-300 MPa 的压缩压力范围内通过粉末冶金技术制备的样品，并在 900°C/1 h 下处理，由于晶界处形成了显著的非晶态硅酸盐相，其可加工性评分为（1/5）较差。另一方面，将压缩压力和烧结温度分别降低至 30 MPa/3 h 和 700°C/2 h，可以最小化非晶相的形成，并将可加工性评分提高至（5/5）。可加工的 SCPC50 的弹性模量和极限强度分别为 10.8±2.0 GPa 和 72.8±22.8 MPa，与成人皮质骨的相应值相当。qRT-PCR 分析表明，与 Ti-6Al-4V 相比，附着在 SCPC50 上的骨细胞显著上调了骨钙素 mRNA 的表达。此外，附着在 SCPC50 上的细胞在 8 天内产生了矿化的骨样组织。另一方面，在相同的实验条件下，附着在 Ti-6Al-4V 上的细胞未能产生骨矿物质。研究结果表明，可加工的 SCPC50 具有成为骨科固定装置的有吸引力的新材料的潜力。
