Direct Composite Bonding

Dental composite resins are types of synthetic resins which are used in dentistry as restorative material or adhesives. Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive. Composite resins are most commonly composed of Bis-GMA monomers or some Bis-GMA analog, a filler material such as silica and in most current applications, a photoinitiator. Dimethacrylates are also commonly added to achieve certain physical properties such as flowability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent. Unlike amalgam which essentially just fills a hole and requires retention features to hold the filling, composite cavity restorations when used with dentin and enamel bonding techniques restore the tooth back to near its original physical integrity. Nevertheless, time to failure is still longer for amalgam, and it has remained a superior restorative material over resin-base composites, but with poor aesthetic qualities.

The main advantage of a direct dental composite over traditional materials such as amalgam is improved aesthetics. Composites can be made in a wide range of tooth colors allowing near invisible restoration of teeth. Composites are glued into teeth and this strengthens the tooth’s structure. The discovery of acid etching (producing enamel irregularities ranging from 5-30 micrometers in depth) of teeth to allow a micromechanical bond to the tooth allows good adhesion of the restoration to the tooth. This means that unlike silver filling there is no need for the dentist to create retentive features destroying healthy tooth. The acid-etch adhesion prevents micro leakage; however, all white fillings will eventually leak slightly. Very high bond strengths to tooth structure, both enamel and dentin, can be achieved with the current generation of dentin bonding agents.