Patient-friendly definition from the DentistsDirectory.org dental glossary.
Composite resin is a tooth-coloured restorative material made from a mixture of plastic (resin) and finely ground glass or ceramic particles. It is hardened (cured) with a blue light applied by the dentist. Because composite bonds chemically and micromechanically directly to tooth structure, it requires less removal of healthy tooth than older materials like amalgam — the dentist only removes decayed or damaged tooth, preserving more of the natural structure.
Composite is the most widely used tooth-coloured restorative material in modern dentistry. It is used for: filling cavities in any tooth; repairing chipped, cracked, or worn teeth; closing small gaps between front teeth (cosmetic bonding); reshaping teeth to improve smile symmetry; and as an alternative to amalgam in areas where metal-free restorations are preferred. It can be shaded to precisely match the surrounding tooth colour, making it nearly invisible in most cases.
Modern composite materials are durable and suitable for both front and back teeth, though very large fillings in back molars that endure heavy chewing loads can be more prone to wear and fracture than amalgam over many years. Composite restorations typically last 7–10 years or longer with good oral hygiene and regular dental care, though the life span varies significantly based on the size of the restoration, location in the mouth, and the patient's bite and habits. Composite stains more easily than porcelain, so front-tooth bonding may need polishing or replacement over time if exposed to frequent coffee, tea, or tobacco.