Bacteria accumulate in these tiny, hard-to-reach cracks, promoting decay.

The treatment of dental cavities goes back centuries. But it was not until 1875 that @G.@V. Black, a dentist at @Northwestern University Dental School, first described an organized approach to their treatment. His methods are still used today. Dr. Black removed the parts of the teeth that were decayed. He then extended the tooth preparation to include not only the cavity, but also certain other grooves and surfaces. This process, "extension for prevention," is considered prudent because it provides the tooth with some protection from further decay in the future. 

Most cavities discovered during a dental examination will need to be treated. In general, if a cavity has broken through the enamel and is into the underlying dentin, or if it is able to be penetrated with a dental instrument, requires treatment. Early dental cavities -- ones that have not spread to the dentin -- can simply be re-mineralized with fluoride or filled with amalgam. If the decay has spread further into the tooth structure, it can lead to gum disease. This needs to be treated more aggressively, with scaling and planing, flap surgery, or even a root canal.

The goal of treating cavities involves two basic principals:  first, removing the decayed portion of the tooth; second, rebuilding the missing tooth structure with a filling material. The dentist usually begins with an injection of a local anesthetic.