Bonding is the process of applying a composite resin restorative material to teeth in order to improve their appearance; repair any chip-off or crack; lengthen the size or increase width; and as a cosmetic alternative to amalgam fillings. Composites have advantage of color matching and easy processing.  Fillers and modifiers are added to the resin to give it desired properties of color and strength.  Common fillers include quartz, glass, zirconium, silica, barium, and strontium and glass particles.

Bonding is probably the simplest of dental operation which can be done in on session lasting between 30 to 50 minutes.  Treatment of multiple teeth may need to schedule more visits. No anesthesia is required except, possibly, in case of a filling. The area to be treated is abraded or etched by applying an etching gel, normally containing 37% phosphoric acid, to make the surface rough.

A liquid plastic conditioner is applied to the roughened surface which seeps into the surface. Once the conditioner is hardened it makes a tough mechanical bond with the tooth. This prepared surface is now ready to make a chemical bond with the composite. The composite material of the right color is applied layer by layer to obtain the desired thickness.  When sufficient (slightly more than necessary) material has been applied it is molded into the desired shape and smoothed.  Hardening is done for 20 to 40 seconds with a special light which triggers a catalyst additive in the composite. This catalyst triggers only with light of 420-450 nanometer wavelength (violet color), and hence, allows the dentist sufficient time to do a thorough job of molding even in daylight.

The color of the composite restorations can be stained by tea, coffee, or smoke of cigarette or cigar, etc. Routine brushing and flossing is necessary to keep deposits away which could also stain the teeth as well as the filling. Bonding can last for years, provided regular oral hygiene is maintained. However, it is not as strong as amalgam. Chewing on hard stuff like ice, or pins can cause damage. Newer composite filling materials have been developed that have mechanical properties that are comparable, rather even better than the amalgam filling materials.