Three treatments are available.
1st one, Nonsurgical root canal treatment.
pros: can save the tooth.
cons: mutiple time visit to clinic at 7-10 days interval / 1-2 months interval (depending which kind of medication is given to resolve the infection by the dentist).so needs a lots of patience to save the tooth.
If responding and infection start healing via radiograph then congratulations. if not responding after giving medication also (can happened) then Apicoectomy ( cutting the apical root part along with cleaning of the infection) is the option.
pros: can able to save the tooth still.
cons: cant able to done in all tooth specailly posterior due to accessibility issue. so the third option is Extraction and replacement.