Manufacture of Different Types of Thermoplastic

Abstract

The development of resins represented a great step forward in dental technique, the first thermopolymerisable acrylic resins being developed in 1936. Acrylic resins are better known as poly(methyl methacrylate) or PMMA. They are synthetically obtained materials that can be modelled, packed or injected into molds during an initial plastic phase which solidify through a chemical reaction-polymerisation (Phoenix et al., 2004). However, the disadvantages of thermopolymerisable acrylic resins, connected to increased porosity, high water retention, volume variations and irritating effect of the residual monomer (organic solvent, hepatotoxic), awkward wrapping system, difficult processing, together with the polymer development, have led to alternative materials such as polyamides (nylon), acetal resins, epoxy resins, polystyrene, polycarbonate resins etc. (Negrutiu et al., 2001). Thermoplastic resins have been used in dental medicine for fifty years. In the meantime, their use has spread due to their superior characteristics. Their ongoing development has yielded new classes of more and more advanced materials and technologies, which make possible the manufacturing of dentures with better splinting properties then traditional dentures.