Nickel (CHEM000049)

Nickel is a solid, silver-white, hard, malleable transition metal with an atomic number of 28. It resists corrosion even at high temperatures. It is present in many alloys in widespread use, including stainless steels. It may also be present as an impurity in any alloy. Nickel is used in the production of coins, jewellery, and nickel-cadmium batteries, and as a catalyst for the hydrogenation of liquid oils to solid fats such as oleomargarine and vegetable shortening. Nickel-containing dental alloys continue to be used successfully in the provision of various forms of dental care. Many of these alloys have applications in the construction of restorations designed to remain in clinical service for many years, including crowns, fixed bridgework, and removable partial dentures. Furthermore, nickel containing alloys find extensive application in orthodontics, including metallic brackets, arch wires, bands, springs and ligature wires. Many instruments and devises, for example, endodontic instruments also contain nickel. Allergic responses are mediated through the immune system. In a sensitized individual, allergic responses can be initiated by relatively small amounts of the allergen; for example, if nickel ions are released from a nickel plated material following direct and prolonged contact with the skin. Individuals are first sensitized to the allergen. Subsequent exposures, if sufficiently high, may then result in an allergic reaction. A number of allergens are used in the clinical practice of dentistry, notably eugenol, mercury, nickel, chromium, cobalt, components of resin-based materials and a host of other chemical agents. The majority of dental allergies, including allergic responses to nickel-containing dental alloys, comprise Type IV hypersensitivity reactions, cell-mediated by T-lymphocytes. Physiologically, it exists as an ion in the body.(7, 8).