The process of tissue repair is essential to re-establish function and tissue integrity. The ideal goal of endodontic treatment is to achieve periapical healing. Whenever there is an infection or injury, host evoke a protective response by immunoinflammatory process to maintain the original structure and biological function of the tissue. Periapical diseases are mostly due to disintegrated products of pulp tissue or due to toxins produced by the bacteria in root canal system. More than 90% of periapical lesion are dental granuloma, radicular cysts or abscesses. As non- surgical endodontic treatment is the most conservative route, it has largely substituted endodontic surgery for the management of teeth with periapical lesion. Preparation of root canal by only Chemo mechanical means is not effective to completely eradicate the persistent microorganisms present in root canal, hence, intracanal medicaments having antimicrobial property have been recommended as an adjuvant with chemomechanical preparation. This book presents that non-surgical endodontic treatment shows favorable outcome of periapical healing despite the lesion size, pre operative status of tooth or patient age.