Primary (Baby) teeth in children have relatively large pulp spaces and a cavity does not have to get very large before it reaches the pulp chamber.
When the soft tissue in the pulp chamber is infected (has bacteria in it) or affected (is inflamed), it can be removed by a dentist under local anaesthetic. If the soft tissue in the canals is still healthy enough, a special medicated filling can be put into the chamber in an attempt to keep the remaining pulp (in the canals) alive. The process of removing the pulp from the chamber is the actual “pulpotomy”, though the word is often used for the entire process including placement of the medication.
Afterwards the tooth is restored with a regular filling or a stainless steel crown.
In some cases a permanent tooth might have decay down to the pulp but the pulp is still pretty healthy. If the roots haven’t finished forming yet, a partial pulpotomy might give it a chance to finish forming.
Likewise, when a young permanent tooth is traumatized – say, hitting teeth on the handlebars of a bike – it can be broken in such a way that the pulp is exposed. Again, a partial pulpotomy may help it to finish developing and be saved.
A partial pulpotomy is performed by excising a small portion of the exposed pulp tissue, and then covering it with a bio-compatible material such as MTA (mineral trioxide aggregate) as a direct pulp cap. Sealing this bridge from contamination by oral fluids is critical to success of the procedure.
Sometimes the tooth decay (or trauma) on a permanent tooth is so advanced that removal of the pulp tissue in both the chamber and canals is needed to prevent or address further infection. If this is indicated, your child will be referred to a dental specialist (an endodontist) who does only these types of procedures. With the removal of nerves and blood supply from the tooth, it is best that the tooth be fitted with a crown.