Diagnosis: The tooth is being resorbed by the body. It is unknown why this happens, but it is fairly common in cats and it is very painful. Tooth resorption is the most common cause of tooth loss in felines. These lesions start with the outer enamel surface, usually at or below the gum line, and begin as a loss of tooth enamel and can eventually spread to the dentin and then the pulp canal, exposing the blood vessels and nerves to the tooth. 

Treatment: Depending upon the stage of resorption, the entire tooth with the roots may be extracted, or only a portion of the tooth is removed. In this case we removed the crown, (the part of the tooth above the gums) to stop the mouth from being painful. Since the tooth under the gumline had been resorbed there was no root to extract.