A pulpotomy is a really good and reliable way to save a badly decayed baby tooth.
A pulpotomy is when the inflamed pulp chamber, usually on a baby molar, is removed, the area is sterilized, and the chamber is sealed. It is a very common procedure in children and has a good prognosis of success. 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. This is usually the "tooth ache" you feel. If untreated an abscess is likely to form.
Pulpotomies will buy you some time, but 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.
In baby molars a pulpotmy is used in the process of trying to save and restore the tooth.