The anti-oxidative properties of alpha-tocopherol in gamma-irradiated UHMWPE with respect to fatigue and oxidation resistance.

Abstract

Although addition of an antioxidant (alpha-tocopherol) is reported to prevent delamination in ultrahigh molecular weight polyethylene (UHMWPE) knee components, contribution of alpha-tocopherol as an antioxidant to the improvement of long-term fatigue performance of UHMWPE is an unknown mechanism. To solve this problem, bi-directional sliding fatigue tests were performed for gamma-irradiated (25 kGy), gamma-irradiated (25 kGy) with 0.3 wt% alpha-tocopherol added, and gamma-irradiated (25 kGy) with 0.3 wt% tocopheryl acetate added UHMWPE specimens. Internal defect initiation was quantified with scanning acoustic tomography (SAT). Also, oxidation index and crystallinity were obtained from infrared absorption spectra measured using Fourier transform infrared (FT-IR) microscopy. Only gamma-irradiated UHMWPE specimens resulted in severe fatigue fractures. alpha-Tocopherol-added UHMWPE specimens showed significantly lower projected area ratio of defects (1.80+/-0.82) than did gamma-irradiated (7.0+/-2.29) and tocopheryl acetate-added ones (8.50+/-2.01). The oxidation index of gamma-irradiated UHMWPE specimens (0.111+/-0.0052) was extremely higher compared to those of doped ones; 0.0179+/-0.0026 and 0.0144+/-0.0069 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The crystallinity of gamma-irradiated UHMWPE specimens (57.5+/-1.16) was lower compared to those of doped ones; 60.3+/-0.72 and 60.4+/-1.38 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The incorporation of alpha-tocopherol significantly improves the long-term fatigue performance of gamma-irradiated UHMWPE with oxidation stability. Also, the addition of alpha-tocopherol controls macromolecular structures resulting in the improvement of fatigue performance of UHMWPE.

• Authors: Nobuyuki Shibata, Naohide Tomita
• Journal: Biomaterials (Biomaterials) Vol. 26 Issue 29 Pg. 5755-62 (Oct 2005) ISSN: 0142-9612 [Print] Netherlands
• PMID: 15949542 (Publication Type: Journal Article)

Chemical References

• Antioxidants
• Biocompatible Materials
• Polyethylenes
• ultra-high molecular weight polyethylene
• alpha-Tocopherol
• Oxygen

Topics

• Antioxidants (pharmacology)
• Biocompatible Materials (chemistry)
• Gamma Rays
• Humans
• Knee Prosthesis
• Materials Testing
• Models, Chemical
• Oxygen (chemistry, metabolism)
• Polyethylenes (chemistry)
• Spectrophotometry, Infrared
• Spectroscopy, Fourier Transform Infrared
• Surface Properties
• Tensile Strength
• alpha-Tocopherol (chemistry)