Amalgam is a mix of silver particles (with or without other elements of e.g copper tin paladium), of varying size and shape combined with mercury to form a quick setting mix or amalgamation of materials. The best amalgam alloys are more corrosion resistant, show less flow or creep which can lead to early failure. They have a good strength and longevity but they do not bond to teeth. The larger the cavity the less suitable amalgam is as an alloy as the setting expansion and load, wear and tear will increase the risk of remaining tooth fracture. Although there are many concerns raised about the mercury toxicity from mercury in amalgam fillings, few authoritative bodies express concern that the minute levels of mercury released over a life time are a cause for concern to the individual.
Nevertheless dentists in Europe will stop using amalgam fillings—which contain mercury—in pregnant and nursing women and children under the age of 15 in 2018. The ban, which affects dentists in all the 28 member-countries of the EU, comes into effect in July 2018.
Composite fillings are made of glass particles and resin. By using a combination of various materials and particle shapes and sizes made by different manufacturers, they can have varied strength, polish-ability and appearance. Composites are bonded to the tooth with an acid etch and resin and set with a blue light. Most suitable for small fillings, the larger the cavity, the more the filling is subject to wear and tear and aging than amalgam or porcelain. We use composites mostly for fillings on front teeth and anticipate eight years from an average small filling. Composites may also be used for larger fillings but are challenging to achieve the best shape and sufficient contact points between teeth to prevent food from packing. Their expected lifespan is from five to eight years.