Any suggestions for incision and drainage for abscessed tooth after a failed root canal?

Re treatment: That failed root canal tooth sould be treated with antibiotics and incision and draining of the abscess if necessary. After that that root canal should be re done if the tooth is savable , or extracted if not.

Don't do it yourself: Incision and drainage should only be done by the dentist or oral surgeon. This procedure is done usually with severe, life threatening infections that don't respond well to oral antibiotics. If that does not apply to you then you may want to go back to the dentist to see if antibiotics are needed. Then do something about the failing root canal= retreat or extract and place an implant.