Root canal preparation is a critical procedure of root canal therapy, and it’s essential for high quality preparation to accurately measure the initial working width and determine the final working width of the apical portion of the root canal. An adequate working width should eradicate intracanal infection thoroughly and achieve the best effect of root canal cleaning and shaping under the premise of saving tooth structure as far as possible. In this paper, the concepts, techniques and controversies of working width of apical preparation were reviewed.
