if you use your finger to push along the gum area around the suspect tooth and can see or taste a different or foul taste this may be puss coming from the infected area and may have to have it extracted , a root canal may just add to your problem if it is recommended by a dentist , once a tooth is infected like that it is hard to save that tooth , I have delt with that a couple of times and in the end had to have them extracted anyway ,and cavitations can also cause health problems also , I sounds like your dentist may be able to help you in that area ( god luck , and hope you get this resolved soon so you can start feeling better)