title: Ultra-high-molecular-weight polyethylene fiber reinforced dental composites: Effect of fiber surface treatment on mechanical properties of the composites.
abstract: OBJECTIVE
  Poor interfacial adhesion between the fibers and resin matrix in the ultra high molecular weight polyethylene (UHMWPE) fiber reinforced composites (FRCs) is the main drawback of the composites. This study aims to evaluate the effect of corona and silane surface treatment of the fibers on the mechanical properties of the UHMWPE FRCs.
  
  
  METHODS
  UHMWPE fibers were exposed to corona discharges for different periods of time (0s, 5s, 7s). The surface characteristics of the UHMWPE fibers were investigated by attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and nanoindentation technique. The flexural strength and flexural modulus of the FRCs made of the treated fibers were determined on 2mm×2mm×25mm specimens. The fracture toughness (the critical stress intensity factor, KIC) of the composites was also evaluated using a three-point single edge notch beam (SENB) bending technique. Statistical analysis of the data was performed with ANOVA and the Tukey's post-hoc test. The fiber-resin interface and the fracture surface were investigated using SEM.
  
  
  RESULTS
  The change in the surface mechanical properties and chemistry of the corona treated UHMWPE fibers were monitored. The fibers exposed to corona for 5s showed higher surface nanohardness. In the FRCs, the specimens reinforced with 5s corona treated silanized fibers showed higher mechanical properties (flexural modulus, flexural strength, and fracture toughness), SEM images revealed a better adhesion between the resin and fibers after 5s fiber corona treatment and silanization.
  
  
  CONCLUSIONS
  Corona and silane treatment of UHMWPE fibers provide dental FRCs with improved mechanical properties.
authors.affiliation: Department of Biomaterials, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Niloofar
authors.initials: N
authors.lastname: Bahramian
authors.affiliation: Iran Polymer and Petrochemical Institute (IPPI), P. O. Box 14965/115, Tehran, Iran. Electronic address: m.atai@ippi.ac.ir.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Atai
authors.affiliation: Department of Chemistry, Iran University of Science and Technology, 16846 Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Naimi-Jamal
mesh_terms: D001840:Dental Bonding; D003793:Dental Restoration, Permanent; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011095:Polyethylenes / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D011095:Polyethylenes; D012821:Silanes; C111601:ultra-high molecular weight polyethylene; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium
keywords: Corona treatment; Fiber reinforced composites (FRCs); Mechanical properties; UHMWPE fibers