The purpose of the root canal therapy is to eliminate the inspection and obtain a perfect obturation of the root canal, so that to prevent and cure the periapical lesions. Complex variation of the apical third, including the different kinds of the apical foramens, the curve of the root canal, high presence of the lateral canals et al, will influence the every step of the root canal therapy, increases the difficulty of it and affect the prognosis consequently. This review highlights the effect of anatomy of apical third of permanent teeth on root canal therapy.
