TF TM Adaptive : a novel approach to nickel - titanium instrumentation

instruments have been traditionally used with a continuous rotary motion, but more recently, a new approach to the use of nickel-titanium instruments in a reciprocating movement has been introduced by Yared (2004). The clockwise (CW) and counter-clockwise (CCW) rotations used by Yared were four-tenths and two-tenths of a circle respectively, and the rotational speed utilized was 400 rpm. The concept of using a single nickeltitanium instrument to prepare the entire root canal was made possible due to the fact that a reciprocating motion is thought to reduce instrumentation stress. Recent literature data show that reciprocating motion can extend cyclic fatigue resistance of nickel-titanium instruments when compared to continuous rotation, mainly because it reduces instrument stress. As the instrument rotates in one direction (usually the larger angle), it cuts and becomes engaged into the canal, then disengages in the opposite direction (usually with the smaller angle); and the stresses are, therefore, reduced. Following these concepts, new instruments have been recently commercialized: Reciproc® (VDW, Germany) and WaveOne® (DENTSPLY Tulsa Dental Specialties), which uses specially developed motors that produce reciprocating movement (using approximately 150°-30° angles). This reduction of instrumentation stress (both torsional and bending stress) is the main advantage of reciprocating movement, even if it has been shown that a lot of different reciprocating movements can be used. Each one affects the performance and the safety of the nickel-titanium instruments. Therefore, when discussing the advantages and disadvantages of reciprocation, the exact motion should also be mentioned, since the actual angle of reciprocation can have a substantial influence on both the clinical and experimental behavior of nickeltitanium instruments. Another possible advantage of reciprocation is a better maintenance of the original canal trajectory, mainly related to lower instrumentation stress and, consequently, its elastic return. However, it must be underlined that reciprocation does not affect the inherent rigidity of the instruments. If a quite rigid nickel-titanium instrument of greater taper is slightly forced into a curved canal, it will create more canal transportation than a more flexible one, due to its inherent tendency to straighten. Moreover, tip design can strongly influence canal transportation, with a cutting tip being more dangerous than a non-cutting pilot tip. While reciprocation with nickel-titanium TF Adaptive: a novel approach to nickel-titanium instrumentation