Hi.. Can understand your concern.. As per your complain if your root canal treated tooth is cracked so placement of crown will not be advisable as a cracked tooth will not be able to bear the chewing forces even after placement of crown and finally the tooth will break off along with crown and the entire treatment will go waste.. In case if after removal of the cracked portion of the tooth some of the visible natural crown structure is left intact a treatment modality known as POST and CORE can be done in which a small rod of inert material is placed into the root canal and cemented or glue there followed by building up a core with a filling material and crown is placed over it.. In case you have no sound tooth structure left then extraction followed by placement of a bridge or implant are the correct options. Hope this information helps.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.