When a tooth has had an impact that is hard enough to cause internal damage, but not hard enough to break the tooth, or has inflammation of the pulp, the tooth may become discolored. The discoloration often starts out as pink or purple. Some affected teeth do not show obvious discoloration at first, but over time develop gray, tan, brown, or ivory discoloration. Studies have shown that more than 90% of discolored teeth are teeth in which the pulp has died. The necrotic (dead) contents of the pulp continuously leak out of the root of the tooth, causing chronic inflammation. Most discolored teeth are dead teeth, and must be treated either by extraction or root canal therapy (see separate entry on endodontic treatment).