16. Which one is the advantage of crown down technique? a. More time consuming b. If large, less flexible rotary instrument are used too rapidly and deeply in the root canal, a ledge may form c. Elliminates coronal interferences which allows better determination of apical canal sizes.

The correct answer is:<br /><br />c. Eliminates coronal interferences which allows better determination of apical canal sizes.<br /><br />The crown-down technique is a method used in endodontics to shape the root canal. It involves removing the coronal portion of the pulp chamber and then using a series of files to gradually enlarge the apical opening. This technique helps eliminate coronal interferences, allowing for better determination of apical canal sizes. It also helps in creating a more uniform canal shape and size, which can facilitate the cleaning and shaping process.