If a baby tooth decays into the nerve or pulp (located at the core of the tooth), the baby tooth will eventually become infected.
If the tooth becomes infected, the tooth cannot be saved and will require extraction. If a baby tooth is taken out too early, the space reserved for the permanent tooth that will come up to replace it gets lost, which will cause severe crowding and an incorrect bite later in life.
Before the baby tooth becomes infected, it is possible to do a pulpotomy. This removes just the top part of the pulp that is affected by the bacteria from the tooth decay. This protects the rest of the pulp from becoming infected, and the baby tooth can stay in the mouth to reserve the space for the permanent tooth.
A pulpotomy is a fairly quick procedure performed under local anaesthetic, and is completed in a single visit.