BIOMECHANICAL PROPERTIES AND CLINICAL USE OF A POLYETHYLENE FIBRE POST-CORE MATERIAL

The development of fibre-reinforced composite (FRC) technology has led to substantial improvement in the flexural strength, toughness and rigidity of dental resin composites. A number of materials for this type of reinforcement such as carbon, graphite, glass, Kevlar as well as other types of fibre have been considered and appropriate techniques for their use have been investigated. The findings of these studies have shown that both strength and fracture toughness can be increased as a result of their incorporation1. This increased toughness has been attributed to the transfer of stress from the weak polymer matrix to the fibres that have a high tensile strength2. Ultra high strength polyethylene (UHSPE) fibres with higher specific strength, fracture toughness and chemical resistance than carbon, glass or Kevlar fibres were the next materials to be evaluated. It was found that the polyethylene fibres that were used initially were not satisfactory. UHSPE fibres are known to have a low melting point, high creep and, most importantly, a polyolefin backbone. An adequate interface bond between the fibres and various matrix resins is therefore difficult to achieve3, 4. They exhibit poor wetting properties and are difficult to bond because of low surface energies. Chemical inertness and the complete absence of polar groups on the fibres are additional factors4. Different surface enhancements such as plasma spraying, flame and radiation treatment were then studied to improve the properties of the material. Chemical exposure to chromic acid or sulphonic acid invariably resulted in a significant loss of fibre strength5. The addition of cold gas plasmas significantly improved adhesion of UHSPE fibres with epoxy matrices and higher interfacial shear strengths of plasma treated UHSP