The use of non-ISO-tapered instruments for canal flaring

Before 1958, endodontic instruments had no standardized shape or pattern between successively larger sizes. Then Ingle established a nomenclature for the parts of the instrument and a standardization for the length of flutes, taper, and the relationship between successive sizes. His recommendations were endorsed and then supervised by the International Standards Organization (ISO). Recently several instruments have been introduced with greater than ISO-standard taper in order to produce preparations with increased taper from the tip to the orifice. The modifications would produce better and cleaner preparations leading to easier-to-place canal-filling materials. Methods for using these newer file systems and changes from the manufacturers' instructions for safer use are presented.