Hello, I can understand your concern. First of all, it is possible that other tooth than the previously treated tooth is infected this time and requires root canal treatment. It cannot be confirmed without examination by the dentist and x-ray. Now regarding your questions for the previously treated tooth, yes, the root canal treated tooth can be re-infected as the science has not yet identified all the bacteria that are infecting the root canal of the tooth and some of them might be resistant to the treatment. In addition, there is a chance that one or more accessory canals of the tooth are not found by the dentist or treated adequately. In that case, the pain may recur. As it is already treated twice, you can take one more chance with the re-treatment at endodotist s or can decide to get the tooth extracted. To answer your second question, no, this is not a precursor to more problems down the road. The root canal is getting repeatedly infected and its treatment with antibiotics, re-root canal treatment or extraction can solve the problem and it may not cause other severe problems. However, treatment in any way is necessary to avoid resorption of bone underneath the tooth and severe episodes of pain. I hope this information helps you. Thank you for choosing HealthcareMagic. I wish you feel better soon. Best, Dr. Viraj Shah