Glossary: Composite Resin

Composite resin fillings are a mixture of powdered glass and plastic resin, and can be made to resemble the appearance of the natural tooth. They are strong and durable and cosmetically superior to silver or dark grey colored amalgam fillings. Composite resin fillings are usually more expensive than silver amalgam fillings. They contain Bisphenol A a known endocrine disrupter chemical. Most modern composite resins are light-cured, causing a polymerization reaction to occur within the material. Once the composite hardens completely, the filling can then be polished to achieve maximum aesthetic results. Composite resins experience a very small amount of shrinkage upon curing, causing the material to pull away from the walls of the cavity preparation. This makes the tooth slightly more vulnerable to microleakage and recurrent decay. With proper technique and material selection, microleakage can be minimized or eliminated altogether. Besides the aesthetic advantage of composite fillings over amalgam fillings, the preparation of composite fillings requires less removal of tooth structure to achieve adequate bond strength. This is because composite resins bind to enamel (and dentin too, although not as well) via a micromechanical bond. As conservation of tooth structure is a key ingredient in tooth preservation, many dentists prefer placing composite over amalgam fillings when possible. Generally, composite fillings are used to fill a carious lesion involving highly visible areas (such as the central incisors or any other teeth that can be seen when smiling) or when conservation of tooth structure is a top priority.

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