When teeth are heavily decayed they may be too weak to survive with just a filling. They are more likely to fracture and lose considerable tooth substance. The greater risk is that a fracture line may go below the margin of the gum, which makes restoration more difficult, or near impossible. By placing a crown, a tooth may be given a new lease of life.

Six Month Smiles
American Dental Association
Irish Dental Association
British Dental Association
Irish Endodontic Society