“Root canal” has become a term that dental patients do not want to hear, but with the advances in dental technology that have made it much less scary. Local anesthetics and proper pain medication allow the procedure to be performed with little to no pain in most cases.
Teeth that decay even further can expose the canal filling material to bacteria which can cause a new infection. A loose, cracked or broken crown can expose the tooth to a new infection. A tooth that has sustained a fracture can also expose the tooth to a new infection.