POLYMERS

Outline Criteria for the Selection of Polymers as Dental or Biomaterial

Outline Criteria for the Selection of Polymers as Dental or Biomaterial

What does the literature review tell us about the potential polymers especially "PMMA" employed in clinical dentistry application

PMMA is characterized by crystal clear transparency, unexcelled weatherability, and a useful combination of stiffness, density, and moderate toughness. The heat deflection temperatures range from 165 to 212°F, with a service temperature of 200°F. Improvement of the mechanical properties of PMMA can be achieved by orientation of heat-cast sheets. The dental industry has taken great advantage of polymer science to design ma-trials. Materials used in the oral cavity or external prostheses have very septic requirements, i.e., these materials must have physical, chemical, biological, anaesthetic requirements, not always felled by currently available materials (Robert, 1995, 722). A host of requirements must often be met, including adequate strength, resilience, wear or abrasion resistance, dimensional stability for fabrication and use, translucency or transparency to provide a match of the natural tissue replaced, good colour stability, resistance to the oral environment, show tissue tolerance and low toxicity, and exhibit ease of fabrication into a needed dental device. Since few resins full all the mentioned requirements, the search for improved dental materials has been limited to a few classes of polymeric materials (Miller, 1996, 129).

Poly(methyl methacrylate) (PMMA) has been widely used as a denture-base acrylic resin due to its excellent physical and mechanical properties. However, the material is highly prone to microbial fouling that often leads to Candida-associated denture stomatitis. Incorporation of phosphate groups into PMMA could facilitate adsorption of salivary antimicrobials and inhibit microbial adherence on the polymer surface. An in vitro study evaluated PMMA polymers containing varying amounts of phosphate group for their efficacy to inhibit Candida albicans adhesion, adsorb salivary histatin 5, and exhibit candidacidal activity.

Polymethyl methacrylate can be modified by copolymerization of methyl methacrylate with other monomers, such as acrylates, acrylonitrile, styrene, and butadiene. Blending with SBR improves impact resistance. The 2-hydroxyethyl ester of methacrylic acid is used as the monomer of choice for the manufacture of soft contact lenses. Copolymerization with ethylene glycol dimethacrylate produces a hydrophilic network polymer, also called hydrogel. Hydrogel polymers are glassy and brittle when dry but become soft and plastic after swelling in water. The most important properties of a hydrogel are its equilibrium water content and oxygen permeability.

Clinical application of polymers as dental materials/ biomaterials (give specific example, such as polymethyl methacrylate

Dentistry uses a variety of different polymer materials. Dental polymer materials are based on methacrylate, its polymer, and polyelectrolytes. The setting of restorative materials and adhesives is initiated chemically by mixing two components or by light. In both cases, polymerisation is incomplete and monomers, not reacted, release (Lapshin, 2010, 33).

Studies have documented that monomers may cause a wide range of adverse health effects such as irritation to skin, eyes or mucous membranes, allergic dermatitis, asthma, parenthesise in the fingers, and disturbances from central nervous system such as; headache, pain in the extremities, nausea, loss ...