CLEANING AND SHAPING USING ROTARY

INSTRUSMENTS

Dr. B.VENI ASHOKP.G

DEPT. OF CONSERVATIVE DENTISTRY AND ENDODONTICS

CONTENTS• INTRODUCTION• ROTARY SHAPING GUIDELINES• CROWN DOWN TECHNIQUE• CORONAL 2/3 ROTARY SHAPING TECHNIQUE• APICAL 1/3 ROTARY SHAPING TECHNIQUE• ROTARY SHAPING INSTRUMENTS• CLEANING AND SHAPING WITH DIFFERENT

ROTARY INSTRUMENTS• CONCLUSION

INTRODUCTION Rotary Shaping instruments are replacing the

conventional hand file systems to enhance shaping ability of the canal , reduce clinical mishaps like blocks, ledges, transportations and perforations.

When the clinician masters the “method-of-use” protocols of rotary shaping instruments unpredictable file breakage, metal fatigue, loss of cutting efficiency, variation in length, diameter and curvature of the canal can be avoided and better shaping of the canals with desired taper will be achieved.

Directions for use of NITI

Rotary Niti shaping instruments There are various Rotary shaping instruments that are

available in the markets. The concepts, strategies and techniques for successful use are not unique to any one system; they generally apply to all niti rotary systems regardless of their brand names or geometries.

Most widely used Rotary Niti instruments are : Profile system GT, Profile .04 .06 taper, Protaper, Quantec series, Light speed, Hero 645, k3 file series and many more..

Common features of nickel tittanum files.

instrument year Cross section

taper Rake angle tip

Light Speed 1992 U file 00 -ve Non cutting

Profile 1993 U file 02-06 -ve Non cutting

Orifice Shaper

1993 U file 05-08 -ve Non Cutting

Quantec 1996 Modifiled k file

02-12 +ve Cutting

Hero 642 1999 Modified H file

02-10 -ve Cutting

RaCE 1999 Modified K file

02-10 -ve Non Cutting

Flex master 2000 Modified K file

02-06 -ve Cutting

ProTaper 2001 Modified K file

Multiple reverse

-ve Non Cutting

K3 2001 Modifies k file

02-10 +ve Non Cuttingt

           

RADIAL LANDS

A Radial land is a surface that projects axially from the central axis, between flutes as far as the cutting edge.

Another way of evaluating radial land is blade support.

Rotary files has full radial lands. Ex: Profile, GT.

Or their lands were recessed Ex: Quantec

RAKE ANGLE the rake angle is the angle formed by the

cutting edge and a cross section taken perpendicular to the long axis of the instrument

The cutting angle on the other hand is the angle formed by the cutting edge and a radius when the file is sectioned perpendicular to the cutting edge.

HELICAL ANGLE: is the angle that the cutting edge makes with the long axis of the file

Variable helical angle debris will be removed in a more efficient manner and the file will be less likely to screw into the canal.

PITCH : is the number of spirals or threads per unit length. The result of a constant pitch and constant helical angles is a “pulling down” or “sucking down into the canal”.

This is particularly significant in rotary files with a constant taper.

K3 is the only file that addressed this issue. This file has purposely been designed with constant tapers but with variable pitch and helical angles.

Active and passive Instruments The Nickel titanium rotary instrument systems2 main categories: active and passive instruments. Active instruments: Have active cutting blades

similar to K flexo file. They have the ability to cut more efficiently, aggressively and tendency to straighten the canal curvature.

Passive Instruments : These instruments have a radial land between cutting edges and flute. The radial land touches the canal wall on its entire surface, guiding the instrument – stable and balanced with in the canal.

  Active Instruments Passive

Instruments

Profile RaCE

GT files Hero642

Light speed K3

  Flex master

  Protaper

 

ROTARY SHAPING GUIDELINES

Rotary shaping instruments are introduced into the canal only after the confirmation of straight-line access and the canal been scouted by a small hand instruments.

small flexible, stainless steel, ISO 0.02 tapered hand files confirm straight line access, cross sectional diameter and canal anatomy giving the clinician the idea to introduce the rotary instrument into the canal.

There certain standards or guidelines that has to be followed or kept in mind before and during use of the rotary instruments.

1.Straight line access : “on – off” position of handle of the file to be corrected.

2.Cross-Sectional diameter: To be confirmed with hand instruments, sufficient space to guide the rotary instruments is must.

3.Root canal system Anatomy: curvature, recurvature, dilaceration, dividing, merging.

4.Speed and sequencing: Rotary instruments experience less breakage when used with gear reduction electric motors, also using larger taper instruments first and then small tapers reduces breakage.

5.Lubrication and the “light-touch”: Always introduce the rotary instrument in a lubricated canal, that will avoid friction. The pressure that is given on the rotary instrument should be equivalent to the pressure when writing with sharp lead pencil.

CORONAL TWO THIRD ROTRARY SHAPING TECHNIQUE. a) Root canal first scouted with small number hand file. b) Rotary instrument that fits passively with in the canals orifice is selected.c) Regardless the name and brand of the rotary system to be used, crown down technique to be followed.d) When used properly, the instrument will pass passively and progressively into the canal according to the canal’s cross sectional diameter, curvature and anatomic form but never deepen the instrument into the canal which has not been scouted.

e) When the rotary files ceases to move, then the cutting is stopped immediately and the file is withdrawn from the canal to check for the debris accumulation along the cutting blades.

f) At this stage the dentist should decide to use either one size larger or one size smaller file to reduce dangerous taper lock.

g) Clearing debris from the instrument allows close inspection of the cutting blades for evidence of stress, strain or frank deformation.

h) after each Niti rotary, the clinician should passively irrigate , recaptuvate with a small clearing file to move debris into the solution and then irrigate to flush out debris and clear the canal.

i) when a confirmed glide path through the coronal two thirds of a canal, the clinician should either reintroduce the same rotary instrument to see if it will passively move deeper into the canal or proceed to the next small file.

The rule is, “take what the canal will give” and not try to force the instrument letting the preparation evolve to its optimal shape.

j) In more calcified or anatomically difficult canals, it may be necessary to recapitulate through a portion or the entire instrument series a second or third time to create a clean, smooth, flowing coronal two thirds of the canal.

Apical one third rotary shaping techniquea) Rotary NiTi instruments can be used to complete the

apical one third after a no.15 hand file can be pushed apically a few mms to the terminus.

b) Any given series of files, regardless of the difference in geometries among various instrument lines, can create a variety of apical-third tapers based on its method of use.

c) Rotary NiTi shaping files are best used starting with the larger instruments and working through with smaller instruments in a crown down manner.

d) Theoretically a Rotary niti file is designed to follow a canal length as its non-cutting, most flexible working end is guided by the pilot hole of circumferential dentin. If a portion of the file extends beyond the foramen, esp. in the curved canal, then there is no pilot hole to guide the instrument that, with its rapidly increasing taper and stiffness only leads to probability of iatrogenic mishaps.

e) Each instrument is rotated at the recommended RPMAnd passively directed apically.

e) When the rotating instruments resists apical movement, the clinician should irrigate, recapitulate and irrigate to confirm the glide path way and canal patency.

f) Then the canal prepartion is continued either by using the same file or the next smaller one.

g) Even in the presence of smooth and glided path care must be taken at the terminal 1-2 mm of canal to prevent instrument breakage. Best way to avoid this breakage is “thinking of shaping instruments as disposable items”

h) If the rotary shaping instrument used to finish the apical third of a canal have sufficient taper, preparation is automatically gauged, tuned and ready to pack.

ProFile 0.04 and 0.06 Taper andProFile Orifice Shapers

System GT

Canal Preparation According to the manufacturer, the ProFile GT

technique can be broken down into three steps:

1) Step-down with ProFile GTs 2) Then step back with ProFile 0.04 taper

files 3) Then GT file to create final canal shape. As in all rotary techniques, a step-down

approach is used once initial negotiation is completed with hand files and lubricant.

Standard GT files (0.12, 0.10, 0.08, and 0.06 tapers) are then used in a step-down manner at 150 to 300 rpm, allowing each to cut to their passive lengths.

Working length should be determined once the GT file has reached two-thirds of the estimated length of the canal.

In some cases, the 0.06 taper will reach full length. Since the standard GT files all have a 0.20 mm tip diameter, the 0.08 and 0.10 taper files should easily go to length if a 0.08 or 0.10 taper is desired for that particular canal.

Rather than using the GT file to the apical terminus, a variation of the technique involves the creation of an apical taper. ProFile 0.04 taper instruments, usually sizes 25 to 35, can be used in a step-back fashion, starting about 2 mm short of working length

The standard GT files can then be used in a step-down fashion again to create the final canal shape right to working length, or, if preferred, hand instruments may be used to shape the apical 2 mm of the canal.

If additional coronal flare is needed, an appropriate GT accessory file can be used.

Speeds must be kept constant, a light touch must be used, the GT files should not be used in a canal more than 4 to 6 seconds, and irrigation and lubrication must be continually used throughout the procedure

Small canal Small roots include mandibular incisors, buccal roots of maxillary molars and mesial roots of mandibular molars. Use yellow-banded 20 series in these cases.

Medium canal Medium roots are often the maxillary premolars, mandibular premolars and sometimes mandibular anteriors.The blue-banded 30 series may be most appropriate here.

Large canal Large roots will generally be found in maxillary anteriors, mandibular cuspids, some mandibular single-canal premolars, and palatal roots of maxillary molars and distal roots of mandibular molars. The black-banded 40 series of instruments was designed to handle these cases

ProTaper (Progressively Tapered) nickel titanium rotary files are specially designed to instrument difficult, highly calcified, and severely curved root canals.

The ProTaper technique

1 Explore the root canal with a stainless steel 10K hand file using a small reciprocating back and forth motion. Work passively and progressively until it is a few millimeters short of the estimated working length. Fill the pulp chamber full with (NaOCl) for all initial negotiation procedures.

• 2 start the ProTaper sequence with Shaping file N° 1 which has purple ring. The S1 is carried into the canal and moved apically to just short of the depth of the hand files. In more difficult canals, one or two recapitulations may be necessary to enlarge the coronal two thirds of the canal. Irrigate and go back in with 10K hand file to break up debris and then re-irrigate

3 The SX (no colour ring) is then used with a brushstroke action to selectively remove dentine, relocate the canal away from furcal danger and achieve straight line radicular access. With improved access, the SX is passively fit a little deeper into the canal until it encounters light resistance. Bounce off this resistance and brush out of the canal in an apical to coronal direction. Continue with the SX until about two thirds of the overall length of its cutting blades are below the orifice. Don’t forget to irrigate.

• 4 Once the pre-enlargement procedure is finished with excellent coronal two thirds access, use a precurved 10K hand file to negotiate the rest of the canal, establish patency, and confirm working length. When working length is confirmed and a smooth GLYDE path to the terminus is verified, use Shaping file N° 1 to length

• 5 Following the use of S1, irrigate and use Shaping file N° 2 which has a white ring on its handle. This file will typically go to full working length on the first pass. Following its use, irrigate

• 6 .When the coronal two thirds of the canal has been prepared, the apical one third can be finished. The Finishing file N° 1 has a yellow ring (ISO 020) and with the canal flooded with irrigant, carefully take the F1 to working length and immediately withdraw.

• 7 Gauge the size of the foramen by placing a 20 K hand file to length. If snug at working length then the canal is prepared and ready to obturate. If it is loose, use Finishing file N° 2 (red ring ISO 025). Irrigate and carry the F2 to length and gauge the size of the foramen by placing a 25 K hand file to length. If snug at length then the canal is prepared and ready to obturate. If it is loose use Finishing file N° 3 (blue ring ISO 030) and carefully carry it to length.

Quantec System and Graduating Taper Technique

Canal Preparation The Graduating Tapers technique involves a

modified step-down sequence, starting with a larger tapered file first and progressing with files of lesser taper until working length is achieved.

The technique involves canal negotiation, canal shaping, and, finally, apical preparation.

As in all instrumentation techniques, straight-line access to the canal orifices must be made first, followed by passive negotiation of the canal using No. 10 and No. 15 0.02 taper hand files.

A Quantec No. 25, 0.06 taper, 17 mm in length, is passively used. In most cases, this instrument should approach the apical third of the canal; at this point, the working length must be established.

A “Glide Path” is now established for all subsequent Quantec files by working No. 10 and No. 15 0.02 taper files along with sodium hypochlorite to the established working length.

During the shaping phase, each Quantec file, progressing sequentially from a 0.12 taper down to a 0.03 taper, is passively carried into the canal as far as possible

In all cases, light apical pressure, using a light pecking motion and never advancing more than 1 mm per second into the canal.

Each instrument time - 3 to 5 seconds. The sequence is repeated until a 0.06 or 0.05

taper reaches the working length. The apical preparation can then be

deemed complete or further enlarged by using the Quantec standard 0.02 taper No. 40 or No. 45 rotary instruments or hand files.

With the Quantec series, the correct amount of apical pressure must be maintained at all times; the continuously rotating instrument should either be inserted or withdrawn from the canal while allowing for its slow apical progression

The instrument, however, should be withdrawn after the desired depth has been reached and not left in the canal for an extended period of time, potentially causing canal transportation, ledge formation, and instrument separation.

Thus, to reduce procedural problems, there should always be a continuous apical/coronal movement of the instrument, and, if the rotating file begins to make a clicking sound (file binding), one should withdraw the file and observe for instrument distortion

LIGHT SPEED

Canal Preparation Proper coronal access, pre glaring with GG,

working length confirmed with15 size k file. Prior to using the LightSpeed in the

handpiece, the clinician should first select and hand-fit a No. 20 LightSpeed instrument that binds short of the working length.

Once fitted, that LightSpeed instrument is now inserted in the gear-reduction, slow-speed handpiece

There are two recommended motions with LightSpeed:

(1) If no resistance is felt, the LightSpeed is gently advanced to the desired length and withdrawn

(2) If resistance is felt, a very light apical pecking motion (advance and withdraw motion) should be used until working length is attained

Increasingly larger LightSpeed instruments are used to the working length, never skipping sizes, including the half-sizes.

Irrigation should occur at least once after every three instruments

Once the apical stop has been established, the LightSpeed should never be forced beyond this point.

If forced, buckling along the shaft may occur, potentially leading to fatigue and instrument separation

Rapid Body Shapers, Rotary Reamers, and Pow-R Rotary Files Rapid Body Shaper (RBS) (Moyco/Union

Broach; Bethpage, N.Y.) consists of a series of four nickel-titanium rotary engine reamers.

These instruments feature the patented nonledging Roane bullet tip and allow the practitioner to rapidly shape the body of the canal without the problems that can occur using Gates-Glidden drills

Canal Preparation Prior to using RBS, the apical region of the

canal must be prepared with a minimum No. 35 ISO instrument to within 0.5 mm of the apex.

The No. 1 RBS is then placed in a gear-reduction, slow-speed handpiece at 275 to 300 rpm and allowed to track down the canal 2 to 3 mm.

Constant and copious irrigation is necessary at all times.

The RBS is removed to clean the fluting and is reinserted to track another 2 to 3 mm down the canal.

This sequence is repeated until the No. 1 RBS is within 4 mm of the apex.

The No. 2 RBS is then used like the No. 1, also to within 4 mm or shorter from the apex.

The No. 3 RBS, followed by the No. 4 RBS, is used to within 7 mm of the apex, completing the body shaping.

The No. 1 RBS will feel very aggressive, whereas the No. 2 through 4 RBS feel almost passive in comparison.

Apical refinement is subsequently completed by hand instruments or via Pow-R nickel-titanium rotary instruments

Pow-R owing to their taper design, allow the

practitioner to clean and shape the middle and apical regions of the canal in a conservative manner.

These instruments come in standard ISO instrument sizes as well as in half sizes 17.5, 22.5, 27.5, 32.5, and 37.5 for more precise apical refinement.

HERO 642

A crown down technique is recommended with an apical preparation of at least size no:30

       Despite its aggressive design the instrument is easy to operate, with no higher apparent fracture risk than other rotary instruments.

Easy canals can be cleaned with 3 instruments Difficult canals with 5 or 6 - less than with other

NiTi techniques!

K3 Rotary NiTi system

Coronal third and middle third management :a)      After canal orifices have been located and enlarged with K3 enhanced-tapered body shapers, coronal third enlargement in larger canals will be done with .12, medium canals 0.10 and smaller canals accessed with 0.08 tapers.b)      K3 body shaper is used to light resistance, which is usually about 3 to 4mm down the canal, with EDTA gel and canal debris washed with 5.25% sodium hyperchlorite.c)      Body shaper files can be used as MAF after sufficient scouting of canals with stainless steel files or if they slide easily in a canal.

d)      The initial chosen body shaper is followed by successively smaller tapered body shapers( using crown down technique). Used in succession these three body shaping files alone may take the operator to the junction to the middle and apical third or further.

e)      Taking rotary files into the apical third without prior exploration with K files will increase chance that the canal will be blocked with dentinal mud, a ledge created wore of all separation of the instrument.

f)  After middle third scouting with K files, if the0.06 K3 with a tip size of 35 (or appropriate body shaper) will not progress to the desired level( the jn. Of middle and apical third) then a 0.063 K3 with a tip size of 30,25,20 or 15 can be employed. g)  Recapitulation and irrigation should be frequent ideally after every file.

 

Apical third management and deep body shape : a)      Deep body shape refers to the final and ideal shape of a prepared canal at the junction of the middle and apical thirds. This space might be considered as ‘Gate keeper” to the apical third.

b)    After apical third is opend, it must be explored with hand instruments beginning with 6 to 10 k files, operator shoul slowly and gently attempt to reach the estimated working length. After a 10 or 15 hand file reaches the working length, confirmation with radiographs and apexlocator is carried out.

 c)After true working length s reliably established and the glide path is created, K3 files are introduced with larget to smaller tip sizes used in coronal to apical direction until true working length is reached. 

Varying tip sequence .12 ETBS to resistance ( coronal third) .10 ETBS to resistance ( coronal third) .08 ETBS to resistance ( coronal

third/middle third) .06 K3 35 to resistance (middle third) .06 K3 30 to resistance (middle third) .06 K3 25 to resistance (apical third) .06 K3 20 to resistance (apical third) .06 K3 15 to TWL .06 K3 25 to TWL

Variable Taper sequence. .12 ETBS to resistance ( coronal third).10 ETBS to resistance ( coronal third).08 ETBS to resistance ( coronal/middle third).06 K3 40 to resistance ( coronal/middle third).04 K3 35 to resistance ( middle third).06 K3 30 to resistance ( Middle third).04 K3 25 to resistance (apical third).06 K3 20 to TWL.04 K3 25 to TWL.06 K3 25 to TWL 

Gauging the apex : Before a master apical file can be selected, it is

important to gauge the apex, that is to asses till what size the canal is patent. This technique is described with an example.

If a size 25 K file slides to the true working length and gives a resistance to apical displacement , then a K3 with a tip size of 30 or 35 with an appropriate taper can be used to true working length to create the shape above the working length to give an acceptable cone fit. Gauging the apex allows shape to be created above the foramen while maintaining its size, location and patency.

 

RaCE FILES(Reamers with alternating cutting edges)

The innovative design guarantees being able to work gently and maintains tactile sense.

Working speed (300-600 Rpm)

Apical pressure applied should be extremely gentle

Working time (5- 10 sec per instruments)

Orifice openerTip Diameter -40 Tip Diameter -35Taper - .10 Taper - .08Short shafts.Canal ShapersTip diameter – 25 3 instrumentsTaper -.02,.04,.06 Usual length files.

Each SMD® has eight petals corresponding to a maximum of eight utilizations of the instrument.

Hybrid canal shaping technique Ideal preparation : The ideal preparation for the hybrid

concept takes its pattern from the definition by Herbert Schilder and is slightly modified : “ a three dimensional continuously tapering cone in multiple planes with sufficient apical enlargement preserving foramen position and size.

a)      Access cavityb)      Straight line accessc)      Working length determinationd)      Master apical file size determinatione)      Glide path creationf)        Body shapingg)      Apical preparation( apical pre enlargement, apical enlargement ,apical light speed instrumentation, apical finishing.) 

SStraight line access :-     a)    removal of dentinal overhangs in outer aspect of orifice and coronal third, b)facilitate proper irrigation. C) decrease coronal interference and easy passage for instrumentation.d)GG burs. Working length : out of the five methods (different angulated radiographs, electronic apex locator, tactile sense, paper point , patient sensation) combination of at least the first two should be used. 

Master Apical file size : should be based on original canal diameter.“the optimal enlargement of each canal should be calculated.. based on its initial size of the file that binds at the apical portion of the canal and the apex should be enlarged at least three sizes greater than its original diameter. The apical cross sections of most of the roots are not round and consist of major and minor diameter. In determining the minor initial diameter the use of Lightspeed instrument has been shown by Levin et all, the more accurate than K file. Anatomic investigations confirm that in many cases, the original apical diameter is size 30 or 40 or even greater More over there is currently no way to estimate the major original canal diameter clinically.

GGlide Path: - up to size 20 stainless steel hand k file.-   This will enhance the fragile tips of small-sized NiTi rotary instruments to follow the path without exploring or cutting. BBody Shaping : Active instruments such as Protaper can perform this body shaping removing coronal; and middle third of the canal effectively. The Protaper shaping instruments SX,S1,S2 are ideal. They first shape the canal to a flared form with more taper in coronal than apical area, then the taper is moved down to the canal using the crown down technique which will pave way for ideal access to apical preparation.

 Apical Preparation : This step is divided into 4 steps, ( apical pre enlargement,

apical enlargement ,apical light speed instrumentation, apical finishing) but all these four steps may not be necessary for all cases, because different canals require different approaches.

a)      Apical Pre enlargement : The idea of apical pre enlargement is to cut quickly and

effectively the apical canal third to a size to which the canal at working length can quickly and safely be enlarged.

Protaper finishing instruments F1 to F3 will leave an ideal preparation form. only the 2 to 3 mm need to be enlarged. The more difficult the case(more curvature, small radius) clinician should think of using the passive instrument . in very difficult cases, NiTi rotary instruments can also be used by hand.

b)Apical Enlargement : after pre enlargement the apex safely, it often needs to be enlarged more based on the decision on which size MAF should be used for individual canal. Apical Enlargement can be done with Active or Passive instrument depending on the difficulty of the canal curvature. After having reached the working length with Protaper F3 instrument, it is not difficult to enlarge the apex even wider because other NiTi rotary instruments like FlexMaster or other active or passive tapered instruments in sizes such as 40 with a 0.06 or 0.04 and even size 50 with .02 taper can be used subsequently with minimal coronal interference, minimal cutting surface and there fore minimal torque load. The number of instruments for this step seems large, but each instruments cut minimally and cutting action is accomplished with 1 to 3 rotations. This process can easily be done using the instruments by hand, and is safer and faster than changing files in a motorized handpiece. 

Apical Light Speed Preparation. This is necessary when the desired MAF

size is bigger than a size that can be prepared with tapered instruments in a curved canal.

The apex will be enlarged to the desired size starting with a light speed instrument that is one light speed larger than the last instrument that previously reached the working length.

Step back is used with each increasing LightSpeed instrument which will result in 0.05 taper, 1mm increment will give 0.025 taper and will form a “pseudo-taper” which forms steps in the canal making the irrigation solution and gutta percha difficult to pass in the outer wall of canal curvature. 

Apical Finishing:  Apical finishing can be performed using the LightSpeed MAF size instrument or other passive instrument in a 0.02 or 0.04 taper and a size that follows to working length easily. The instrument will be forwarded to working length in a clockwise rotation or a watch-winding motion one or two times by hand. This smoothes the steps in the outer wall of the curvature and merges the step back taper into the more coronally located taper.

 Limitations : Coronally located canal curvatures, extremely severe curvatures, s shaped, ribbon shaped, C- shaped canals, Apical canal bifurcations, margining canals.     

 

Hybrid Sequence over View Easy cases Difficult cases

ProTaper Profile or GT Flex master Profile LightSpeed or RaCE or GT or K3 LightSpeed or ProFile or Hero or GT by hand

SOTOKAWA’S CLASSIFICATION OF INSTRUMENT DAMAGE

Main Causes of Breakage Rotation at too high speed. Application of excessive pressure to the

files. Non-respect of the operating sequences

recommended by the manufacturer. Overuse of the instruments, causing

breakage because of fatigue.

Canal centering It denotes the ability of the instruments to remain centered in the

canal. Centering ratio : The mean centering ratio is a measure of the ability of the

instrument to stay centered in the canal. A ratio of 1.0 would indicate perfect centering.

Glosson et al and Esposito et al attribute the maintenance of the original canal path to the property of NiTi alloy, claims that ProFile instruments remain better centered in the canal and is also been supported by Short et al who compared oi with stainless steel instrument, but no difference was found when compared with other NiTi rotary files.

In a study conducted by Kuhn et al, it was found that NiTi regardless of the tip design, remained significantly more centered and demonstrated less apical transportation than stainless steel files at size 25.

Conclusion : Many variable and interrelationships

influence the clinical performance of the new generation super elastic NITI –rotary-shaping instruments. Much of what is known about NITI-shaping instruments has been learned in clinical practice on patient’s record. Rotary instruments are here to stay, they will continue to improve , but they are not a panacea. However they are an important adjunct for canal shaping procedures.