The rise in the failure rate of root canal treatment over the last few years makes this topic popular among professionals and researchers in the field of dentistry. Previous studies have shown that the E. faecalis is the commonest microorganism found in persistent infection. This book highlights the involvement of root cementum and root apex other than root dentin in persistent infection by E. faecalis. This knowledge would help the dentist in increasing the success rate of root canal treatment and also gives an insight for researchers in least studied aspect such as the role of E. faecalis...