Impact of nickel–titanium instrumentation of the root canal on clinical outcomes: a focused review

Nickel–titanium (NiTi) root canal instruments have improved the technical quality of enlarging and shaping. These instruments have been shown to prepare even severely curved root canal with fewer procedural errors than traditional stainless steel hand instruments. While it would appear that these instruments might enhance clinical outcomes, very few studies have assessed their impact when used in primary root canal treatment. Clinical studies investigating the outcome of primary root canal treatment using nickel–titanium hand or rotary instruments were identified (MEDLINE database) using appropriate key words in an attempt to determine if there have been enhanced outcomes with these instruments. Evidence from one clinical trial suggests that (i) better maintenance of the original canal curvature and shape results in increased success rates and (ii) that ledging of root canals results in reduced success rates. Evidence from two studies indicates that the use of NiTi—either hand or rotary—instruments significantly increases success rates of primary nonsurgical root canal treatment compared with the use of stainless steel hand instruments, while three investigations failed to show any significant differences.