A filling can repair a tooth affected by wear, decay, cracks, or fractures. Fillings are appropriate when the damage to the tooth is minimal – when 1/3rd or less of the tooth needs replacement.
The decayed or affected portion of the tooth is removed and replaced with a filling, which can be made up of different materials, most often a bonded composite (plastic) material
Onlays are suitable when there is extensive damage to the tooth. They are essentially a larger filling that covers the cusps of the tooth or the entire biting surface.