Generations of NiTi Rotary Instruments PDF

# Generations of the NiTi rotary instruments From the 1990s, until now, NiTi rotary instruments have undergone revolutionary changes in terms of the construction and as a result physical characteristics of the NiTi instrument. Furthermore, the design, shape, and number of instruments used in each g...

# Generations of the NiTi rotary instruments From the 1990s, until now, NiTi rotary instruments have undergone revolutionary changes in terms of the construction and as a result physical characteristics of the NiTi instrument. Furthermore, the design, shape, and number of instruments used in each group have been highly modified. The aim of modifying and improving these instruments is to develop a NiTi rotary instrument which cuts and removes the dentine strongly and also is resistant to fracture even in the most challenging narrow, curved root canals. Another purpose of modifying and improving these instruments is to simplify the cleaning and shaping stage and to reduce the number of using instruments along with preserving the original shape of the prepared root canal. ## 1. First Generation This category of NiTi rotary instruments were first introduced to the market during the mid-1990s. The most important characteristic of the first-generation NiTi rotary files is having passive cutting radial lands along with fixed 0.04-0.06 tapers over the full working length. The main important NiTi rotary instruments within this category are LightSpeed Endodontics (1992), Profile-Dentsply (1993), Quantec-SybronEndo (1996), and GT system-Dentsply (1998). Several researches showed that all first-generation rotary instruments created smooth root canal walls which centered in the middle and caused low procedural errors. The main deficiency of this generation of NiTi rotary instruments was requiring numerous files to achieve these goals and complexity. ### Advantages * Optimum flexibility is the ability of the instrument to accompany the curvature of a root canal avoiding the formation of steps, perforations along the root canal or at the apical level; cutting efficiency; reduced working time for the operator, greater comfort for the patient and a lower incidence of postoperative pain. ### Disadvantages * They generate costs for the operator since they must be used only once; possibility of instrument fracture; poor cleaning in flattened root canals. ## 2. Second Generation The second generation of NiTi rotary files was introduced into the market in 2001. These instruments had active cutting edges with greater cutting efficiency, so the number of instruments required to achieve complete cleaning and shaping was almost less in comparison with the previous generation. Notable systems in this generation are ProTaper Universal-Dentsply, K3-SybronEndo, Mtwo-VDW, Hero Shaper-Micro-Mega, I Race, and I Race Plus-FKG Dentaire. Several studies have also approved the efficiency of these systems in fast preparation and also preserving the original shape of canals even in curved and calcified challenging cases although some researchers have reported some degrees of canal transportations along with tendency for breakage while usage. ### Advantages * High resistance to cyclic and torsional fatigue, lower fracture index, greater cutting efficiency, offers a shorter working time providing a reduction of stress for the professional, lower incidence of postoperative pain, therefore in greater comfort for the patient. ### Disadvantages * They generate costs to the operator since they must only be used once, possibility of fracture but with a lower incidence than with the first generation instruments The NiTi Alloy Phase R was also used in the manufacture of the Oscillating (Asymmetric) Systems, usually called Reciprocants, Oscillating Systems (Reciprocants) TF Adaptive (2013) (SybronEndo Kerr Group) ## 3. Third Generation It was in late 2007 that the manufacturers started to apply the heating and cooling technologies on NiTi alloys to improve the safety of these instruments, especially in the curved root canals. In making third generation of the NiTi rotary files, the manufacturers have highly focused on metallurgic properties of the NiTi alloy using heating and cooling procedures on wires which results in reduction of the cyclic fatigue of the files and also reduction of the separation risk of the instruments which is highly demanded by the practitioners. Applying M-wire and R-phase technologies and electrical discharge methods make instruments with high memory shapes and low risk of separation K3 XF Files-SybronEndo, Profile GTX Series-Dentsply, controlled memory (CM) Files (HyFlex CM)-Coltene, and Vortex Blue (Dentsply Tulsa) are notable files in this group which have been exposed to heat treatments to increase flexibility and safety. The CM property helps the instrument to save the shape of the canal when it is moved out of the canal. Flex files (NeoEndo) files have been predisposed to gold thermal treatment which increases their cutting efficiency along with cyclic fatigue resistance. ### Advantages * High resistance to cyclic and torsional fatigue, lower fracture index when used more than once, greater cutting efficiency, greater flexibility compared to first generation (15% more flexible), less working time for the professional, greater comfort for the patient, lower incidence of post operative pain. ### Disadvantages * They generate higher costs, because according to the manufacturer they must be used only once; possibility of fracture, but with a lower incidence compared to the instruments of the previous generation. ## 4. Fourth Generation Reciprocation which is described as any repetitive back and forth or up and down motion is another philosophy in canal preparation which was first introduced by Blanc, a French dentist, in the late 1950s. Instead of full rotation, the reciprocating NiTi rotary instruments have movements in which clockwise and counterclockwise degrees of rotation are quite equal. The reciprocation theory of canal preparation has led to development of the fourth generation of NiTi rotary instruments. The use of a single file technique to achieve a thorough cleaning and shaping goals at this phase was another success which was also derived from the reciprocating philosophy in cleaning and shaping the root canal systems Many studies have shown that the Wave One and the One Shape single-file systems can efficiently reduce the bacterial number in the root canal along with preserving the original shape of it. Wave One-Dentsply, self-adjusting file (SAF)-ReDent Nova, and Reciproc-VDW are featured instruments of fourth generation ### Advantages * Is indicated for root canals with severe anatomical complexity. High resistance to cyclic fatigue, lower fracture index. (300% more resistant), greater cutting efficiency, greater flexibility, 80% more flexible than conventional instruments, offers less working time, lower incidence of postoperative pain, greater patient comfor. ### Disadvantages * Contraindicated for wide or relatively wide and straight ducts. ## 5. Fifth Generation In this generation, the efficiency of canal shaping has been improved by offsetting the center of rotation. The offset designed files produce a mechanical wave of motion that distributes along the full length of the NiTi file which improves cutting and removing the debris in comparison with a centered mass rotating instrument. Furthermore, this offset design reduces the taper lock or the screwing effect which causes instrument separation. HyFlex/electrical discharge machining (EDM)-Coltene, Revo-S-Micro-Mega, One Shape Micro-Mega, and ProTaper Next-Dentsply are important files of the fifth generation. The Revo-S and the One Shape systems of the fifth generation, both manufactured by the Micro-Mega Company, offer proper root canal shaping by continuous clockwise rotation of the instruments inside the root canal system. One Shape which is just a single number 25/0.06. Taper instrument with asymmetrical cross section along the entire blade has variable cross section and longer pitch. Using the glide path, the instrument is optional in One Shape instrumentation strategy. Micro-Mega also offers optional using apical finishing files. These sterile single-use NiTi-finishing files are used after root canal shaping with One Shape in order to enlarge the root canal diameter. ### Advantages * They are 80% more flexible than the files of conventional rotary systems, more resistant to cyclic fatigue by 150% compared to the Universal Protaper System, shorter working time. ## 6. New generation system (NiTi Blue) New generation system (NiTi, Blue): They are manufactured with NiTi Alloy with Blue Treatment. NiTi Vortex BlueTM instruments (Dentsply/Sirona-United States) manufactured with Nitinol 508 and consisting of a blue titanium oxide layer, not seen in traditional super-elastic NiTi instruments. This relatively hard surface layer of Vortex Blue instruments can compensate for the loss of hardness compared to Profile Vortex M-Wire. Vortex Blue and shape memory technologies use special thermal processes to control the transition of extreme temperatures, making the instruments highly flexible. ### Advantages * Indicated for root canals that present a severe anatomical complexity. They follow the natural curvature of the root canal due to its great flexibility, greater resistance to cyclic fatigue (65% higher in relation to instruments manufactured with M-Wire® NiTi and 99% in relation to the first generation NiTi instruments), greater resistance to torsion, offers a lower working time, a reduced memory effect of the instrument (that is, it can be pre-curved slightly and not return to its original position), generating a less resistance of the instrument when introduced into the root canal. Vortex Blue instruments have improved material properties within creases fatigue resistance and flexibility compared to Profile Vortex (M-Wire) instruments. However, both NiTi Blue and M-wire alloy show better fatigue resistance compared to conventional nickel titanium alloy. Torsion resistance is also affected by the cross-sectional design, the metal mass and the properties of the alloy.