Dental Diseases are very common and the treatment of choice is root canal treatment when the infection reached to the pulp, but when the procedure is not carried out in the correct manner various diseases are occur even after the root canal treatment termed as Post Treatment Endodontic Diseases ( PTED). Etiology of PTED is multi factorial and the treatment is complex. so this book reviewed all the causative factor of Endodntic Diseases and also provide comprehensive, preventive and corrective measures to treat these diseases for the benefit of the reader which will enhance their clinical skills and ultimately providing better treatment to the patient.