While your tooth may seem like a solid piece on the outside, the core of the tooth is actually a soft material called the pulp where the nerves, blood vessels, and other important tissues rest. When a cavity grows severe enough to reach the pulp, the treatment is a root canal or pulp therapy.
When the procedure is complete, a crown is placed to protect the weakened tooth and hold its place until an adult tooth is ready to come in. These crowns can be stainless steel or a white cosmetic steel depending on the location of the tooth. These crowns are not meant to be permanent additions like adult fillings and crowns.