The importance of the horizontal dimensions or working width (WW) of the root canal system has not been addressed in most of the research. In long oval or flat canal preparations, the WW is very important as it alters the operator to the possibilities of incomplete root canal preparation. The concepts, techniques, and technologies to measure initial horizontal dimensions and to determine final horizontal dimensions accurately or properly are underdeveloped. Understanding the current concepts and techniques of cleaning and shaping of root canal system; carefully maintaining the aseptic chain,...