A pulpotomy is when the pulp chamber is removed, the area is sterilized, and the chamber is sealed. In some cases it is done on permanent teeth.
When a cavity gets really deep, close to the nerve of a tooth or even into the nerve, the pulpal tissue becomes irritated and inflamed. If untreated an abscess is likely to form, and makes the process of saving the tooth more difficult, sometimes unachievable, and the tooth may need to be extracted.
Pulpotomies cannot save an already abscessed tooth. It is often surprising how a seemingly small are of decay can be deep enough to reach the pulp. This is often due to the varied antomy of baby teeth and the rapid progression of decay. Although a vary reliable procedure, rarely, a tooth with a pulpotomy will have complications and need to be extracted. This is usually due to the remaining pulp tissue in the root canals giving some kind of trouble.
Teeth with pulpotomies are best protected with a stainless steel crown, which should last until the tooth falls out naturally.