Composite Bonding

Composite bonding is the use of dental composite resin — a tooth-coloured restorative material — to repair or reshape teeth. Dental composite resins, also called resin-based or filled resins, are made of synthetic resins that are insoluble, tooth-like in appearance, insensitive to dehydration, easy to manipulate and inexpensive. A typical composite is based on Bis-GMA and other dimethacrylate monomers combined with a filler such as silica and, in most applications, a photoinitiator; adjusting the proportions of these components tailors the material's physical properties. Compared with silver-mercury amalgam, composite offers a far superior appearance, and depending on the dentist's skill, the patient and the type and location of the damage, its longevity can be similar to that of amalgam. In practice the material is placed while soft and dough-like, and the tooth must be kept perfectly dry or the resin may fail to adhere. It is then hardened by exposure to blue light of a particular wavelength (typically around 470 nanometres), which sets off polymerisation. Because the light generally penetrates only 2 to 3 millimetres, a deeper restoration is built up and cured in increments, each layer set fully before the next is added, and the bite is carefully adjusted. A properly placed composite is comfortable, good-looking, strong and durable, and can last ten years or more. Resin-based composites appear on the World Health Organization's List of Essential Medicines.