title: The effect of alpha-tocopherol on the oxidation and free radical decay in irradiated UHMWPE.
abstract: We developed a radiation cross-linked ultra-high molecular weight polyethylene (UHMWPE) stabilized with alpha-tocopherol (Vitamin E) as a bearing material in total joint replacements. The stabilizing effect of alpha-tocopherol on free radical reactions in UHMWPE is not well understood. We investigated the effect of alpha-tocopherol on the oxidation and transformation of residual free radicals during real-time aging of alpha-tocopherol-doped, irradiated UHMWPE (alphaTPE) and irradiated UHMWPE (control). Samples were aged at 22 degrees C (room temperature) in air, at 40 degrees C in air and at 40 degrees C in water for 7 months. During the first month, alphaTPE showed some oxidation at the surface, which stayed constant thereafter. Control exhibited substantial oxidation in the subsurface region, which increased with time. The alkyl/allyl free radicals transformed to oxygen centered ones in both materials; this transformation occurred faster in alpha-TPE. In summary, the real-time oxidation behavior of alpha-TPE was consistent with that observed using accelerated aging methods. This new UHMWPE is oxidation resistant and is expected to maintain its properties in the long term.
authors.affiliation: Harris Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1206, Boston, MA 02114, USA.
authors.forename: Ebru
authors.initials: E
authors.lastname: Oral
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Rowell
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D011095:Polyethylenes / Q000737:chemistry* / Q000528:radiation effects*; D013696:Temperature; D024502:alpha-Tocopherol / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D005609:Free Radicals; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D006861:Hydrogen Peroxide; D024502:alpha-Tocopherol