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Nickel Titanium Endodontic Instruments, properties, use and comaparison. Components, Design.
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Nickel Titanium Instruments in Endodontics: Part 2
Dr. Ashok AyerDepartment of Conservative Dentistry & EndodonticsCollege of Dental SurgeryBPKIHS, Dharan
Contents:
1. Components of an endodontic rotary instrument
2. Instrument Designs
3. K-file
4. Reamers
5. Hedström Files
6. Gates-Glidden Drills
7. Instrument design Modifications
8. LightSpeed and LightSpeed LSX Instruments
9. ProFile
10. GT and GTX Files
11. HERO 642, Hero Shaper
12. ProTaper Universal
13. ProTaper Next
14. K3
15. FlexMaster
16. RaCe, Bio Race
17. EndoSequence
18. Twisted File
19. Path files
20. Self-adjusting file
21. ENDO-EZE reciprocating files
22. The WaveOne single-file reciprocating system
23. Endo Express and Safe Sider
24. Revo-S Sequence
25. Mtwo
26. Conclusions
27. References:
Components of an endodontic rotary instrument
Components of Endodontic Instruments
Flute:
Groove in the working surface used to collect soft tissue and dentine chips removed from the canal wall.
The effectiveness of the flute depends on its depth, width, configuration, and surface finish.
Its effectiveness depends on its angle of incidence and sharpness.
Radial land/ marginal width:
Is a flat cutting surface present between two grooves/ flutes.
The land touches the canal walls at the periphery of the file and reduces the tendency of the file to screw into the canal,
Reduces transportation of the canal.
Reduces the propagation of microcracks on its circumference,
Supports the cutting edge, and
Limits the depth of cut.
Disadvantages: Clogging of the instruments, Friction and heat build-up, Inefficient cutting.
Rotary Profile niTi file, #5 (denTSPLY Tulsa dental, Tulsa, OK). note the instrument’s wide marginal land (arrows)
Relief: Surface area of land that is reduced to a
certain extent to reduce frictional resistance.
Helix angle:The angle the cutting edge forms with the
long axis of the file.Augers debris collected in the flute from the
canal. This angle is important for determining
which file technique to use.
Components of the Quantec niTi rotary instrument (Sybronendo, Orange, CA)
Rake angle Is the angle formed by the leading edge and the
radius of the file.
If the angle formed by the leading edge and the surface to be cut (its tangent) is obtuse, the rake angle is said to be positive or cutting.
If the angle formed by the leading edge and the surface to be cut is acute, the rake angle is said to be negative or scraping
Positive and negative rake angles.
Positive angle results in cutting action
Negative angle results in scraping action.
However, the rake angle may not be the same as the cutting angle.
The cutting angle, or the effective rake angle, is a better indication of a file’s cutting ability and is determined by measuring the angle formed by the cutting (leading) edge and the radius when the file is sectioned perpendicular to the cutting edge.
If the flutes of the file are symmetric, the rake angle and the cutting angle are essentially the same.
The pitch of the file is the distance between a point on the leading edge and the corresponding point on the adjacent leading edge.
Most files have a variable pitch, one that changes along the working surface.
Because the diameter increases from the file tip toward the handle, the flute becomes proportionately deeper, resulting in a core taper that is different from the external taper.
WaveOne variable pitch flute increases safety
Instrument Designs
1. The difference between the file’s minimum and maximum diameters can be reduced so that the torque required for rotating the larger diameter does not exceed the plastic limit of the smaller diameter.
2. The space between the tip and the maximum diameter can be reduced so that the required torque does not exceed the ultimate strength of any part of the file.
Cohen and Hargreaves. Pathways of pulp,10th edition
3. A zero taper or nearly parallel and fluted working portion of the file can be provided for curved canals so that the apical portion of the canal can be enlarged without undue file stress and compression of debris.
4.The continuity of the blade engagement can be interrupted.
5.The number of flute spirals can be eliminated or reduced to the smallest number necessary to prevent excessive torque, which results from the accumulation of debris.
6. Means can be provided to complete the file function before the flutes fill with debris.
7.Any land width can be minimized to reduce abrasion on the canal surface.
8.The file can be given an asymmetric cross-section to help maintain the central axis of the canal.
9.The number of flutes with similar helix angles can be reduced. When helix angles are dissimilar, screwing-in forces are reduced; when flutes have no helix angles, screwing- in forces are eliminated.
10. Positive cutting angles can be incorporated to enhance the efficiency of canal enlargement.
11. Blades can be made appendages or projections from the file shaft rather than ground into the shaft.
12. Channels can be cut along the long axis of the file to facilitate its removal if it breaks.
K-file
K-files were manufactured by twisting square or triangular metal blanks along their long axis, producing partly horizontal cutting blades.
The tip is cutting and pyramidal
Helical angle: 45˚
Noncutting tips, also called Batt tips, are created by grinding and smoothing the apical end of the instrument
NiTi K-files are extremely flexible and are especially useful for apical enlargement in severe apical curves.
They can be precurved, but only with strong overbending; this subjects the file to excess strain and should be done carefully.
Because of their flexibility, the smaller NiTi files (sizes up to #25) are of limited use.
Cross-sectional analysis of a K-file reveals why this design allows careful application of clockwise and counter clockwise.
Rotational and translational working strokes.
Modification of K- files:
K flex file:
Rhomboidal/ diamond cross- section
Increased flexibility and cutting efficiency
K- flex O file:
Twisting a triangular cross section blank
Non- cutting tip
Increased flexibility but less cutting efficiency
K- flex R file/ Roane file
Machined from triangular cross section blank
Modified safe-end tip. (reduction in cutting tip angle).
Balanced force technique, cuts during anticlockwise rotary motion
Triple flex file:
Triangular stainless steel wire is twisted
Has more flutes than reamer but less than K- file.
C + files:
Better buckling resistance than K – file
Sizes: 008, 010, 015
Length: 18, 21, 25 mm
Used for initial penetration and cut better, especially in calcified canals.
Reamers Triangular or square blank
Triangular blanks are more flexible, have a larger groove, more susceptible for fracture.
Square blanks are stable and rigid and have smaller groove.
Helical angle 20˚
Reaming: penetration, rotation (¼- ½) and retraction.
Retraction brings about the cutting action.
Less flutes compared to K-file:
Files: tighter flutes: 1.93- 0.88 mm Reamers: looser flutes: 0.80- 0.28 mm
Example; No. 30 file: 22 flutes per 16 mm of blade No. 30 reamer: 15 flutes per 16 mm of
blade.
Hedström Files Hedström files are milled from round stainless steel blanks.
Cutting action: Retraction
They are very efficient for translational strokes, but rotational working movements are strongly discouraged because of the possibility of fracture.
Helical angle: 60˚
Better cutting action than K-file (more positive rake angle).
Hedström files up to size #25 can be efficiently used to relocate canal orifices and, with adequate filing strokes, to remove overhangs.
Similarly, wide oval canals can be
instrumented with Hedström files as well as with rotary instruments.
Modifications:
Unifile/ Dyanatrak:
Designed with two spirals for cutting blades
Cross section: ‘S’ shaped double helix
High incidence of separation.
Others: Hyflex file, S- file, Triple helix
A- file:
Variant of H- file
More flexible
Flutes/ cutting edges are at acute angle to the long axis of the file.
When used in curved canals,
Flutes on the inner edge collapse and hence no dentine is removed,
On the outer edge it opens, filling the dentine on the outer curvature (simulates anticurvature filling)
U - file
Heath 1988
Cross- section: Six corners, two 90˚ cutting edges at each of the three points of the blade.
Radial land
Adapt well to curved canals
Non cutting tip
E.g. Profile, GT files, Light speed, Ultra-flex files
Gates-Glidden Drills
GG instruments are manufactured in a set and numbered 1 to 6 (with corresponding diameters of 0.5 to 1.5 mm)
GG drills are side-cutting instruments with safety tips; they can be used to cut dentin as they are withdrawn from the canal
GG instruments should be used only in the straight portions of the canal, and they should be used serially and passively
NiTi: FlexoGates
Instrument design Modifications
The instrument tip has two functions:
To guide the file through the canal and
To enlarge the canal.
A clinician who is unfamiliar with the tip design of a particular instrument is apt to do either of the following:
Transport the canal (if the tip is capable of enlarging the canal and remains too long in one position)
Encounter excessive torsion and break the file (if a noncutting tip is forced into a canal with a smaller diameter than the tip).
Transportation of the original axis of the canal can occur by remaining too long in a curved canal with a tip that has efficient cutting ability.
As long as the file is engaged 360 degrees, canal transportation is unlikely to occur.
Only with overuse does the file begin to cut on one
side, resulting in transportation.
Most instrumentation errors occur when the file tip is
loose in the canal, which gives it a propensity to transport the canal.
If the canal is smaller than the file, the prudent use of a cutting tip is more efficient.
If the canal is larger than the tip, using a less-effective cutting tip can help prevent transportation.
Cohen and Hargreaves. Pathways of pulp,10th edition
Instrument System Cross-Section Tip Design Taper Other features
Profile Non cutting Fixed taper 20 degree helix angle & constant pitch Triple U shape with radial lands.Neutral rake angle planes dentin walls.
LightSpeed Non cutting Specific instrument Thin, flexible noncut-ting
sequence produces shaft & short cuttinga tapered shape. Head.
ProTaper Non cutting Variable taper along Pitch & helix anglebalanced to preventtaper lock.Convex triangular shape, sharp cutting edges, no radial lands.
HERO Non cutting Fixed taper; 2,4,6 % Variable pitch. Files have a short cutting portion
(12- 16 mm).Triangular shape with positive rake angle for cutting efficiency.
No radial lands.
Grossman’s Endodontic Practice. 12th Edition
K3 Non cutting Fixed taper Variable pitch & core 2, 4,6 % diameter.
Positive rake angle for cutting efficiencyThree radial lands, relief for reduced friction
FlexMaster Non cutting Fixed taper Individual helical an-gles 2, 4, 6% for each instrument to
Intro file has 11% reduce screw-in ef-fect.
Convex triangular shape with sharp cutting edges & no radial lands
RaCe Non cutting Fixed taper Alternating cutting edges 2,4,6,8,10% along the length due to
alternating twisting & untwisting
Mtwo Non cutting Fixed taper Variable pitch, Steep 4, 5, 6, 7 % helical angle to reduce
screw-in effect.S- shape design with two cutting edges, no radial lands.
Minimum core width to improve flexibilityGrossman’s Endodontic Practice. 12th Edition
Nickel-Titanium Rotary Instruments
The specific design characteristics vary, such as tip sizing, taper, cross section, helix angle, and pitch.
New designs continually are produced, but the extent to which clinical outcomes (if any) will depend on design characteristics is difficult to forecast.
LightSpeed and LightSpeed LSX Instruments
Developed by Steve Senia and William Wildey in the early 1990s and now also known as LS1.
Long, thin non-cutting shaft and short anterior cutting part (0.25- 1.75mm)
A full set consists of 25 LightSpeed LS1 instruments in sizes #20 to #100, including half sizes (e.g., 22.5, 27.5); LSX does not have half sizes, and a set includes sizes #20 to #80.
The recommended working speed for LS1 instruments is 1500 to 2000 rpm and for LSX, 2500 rpm.
Both variants should be used with minimal torque, owing to the thin shaft.
Cross sections of LightSpeed LS1 cutting parts show three round excavations, the U-shape design common to many earlier NiTi instruments,
Whereas the LSX is shaped like a flat chisel in cross section.
design features of a LightSpeed instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM,
×200). C, Lateral view. D, design specifications.
Considerably more flexible than any other instrument on the market.
Cyclic fatigue is lower than with all other instruments, allowing the use of higher rpm speeds.
All Light-Speed instruments feature a noncutting tip.
Because of their design, LightSpeed LS1 and LSX require specific instrumentation sequences to produce canal shapes amenable to root canal filling.
The current recommendation calls for an apical 4-mm zone to be prepared to a cylindrical, nontapered shape.
This section may then be filled with the proprietary SimpliFill system
A low incidence of canal transportation and preparation errors.
Loss of working length was also minimal in most of these studies
Bergmans L et al. Int Endod J 35:820, 2002
Marending M, et al Compared the apical fit in two dimensions of the first K-file versus the first Lightspeed LSX instrument binding at working length after an initial crown-down preparation.
The apical large canal diameter was assessed more accurately by the LSX instruments
Instruments with a flat widened tip were found to determine apical cross-sectional diameter better than round, tapered instruments.
Marending M, et al. International Endodontic Journal, 45, 169–176, 2012.
ProFile
[DENTSPLY Tulsa Dental] was introduced by Ben Johnson in 1994.
Have increased tapers compared with conventional hand instruments
The ProFile system was first introduced as the “Series 29” hand instruments in .02 taper, but it soon became available in .04 and .06 taper.
The tips of the ProFile Series 29 rotary instruments had a constant proportion of diameter increments (29%).
Design features of a ProFile instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
Cross sections of a ProFile instrument show a U-shape design with radial lands and a parallel central core.
Lateral views show a 20-degree helix angle, a constant pitch, and bulletshaped noncutting tips.
Together with a neutral or slightly negative rake angle, this configuration facilitates a reaming action on dentin rather than cutting.
Also, debris is transported coronally and is effectively removed from the root canals.
ProFile instruments shaped canals without major preparation errors in a number of in vitro investigations.
A slight improvement in canal shape was noted when size .04 and .06 tapered instruments were used in an alternating fashion.
Bryant ST et al. Int Endod J 31:275, 1998. Int Endod J 32:155, 1999.
Comparative assessments in vitro suggested that ProFile prepared mesial canals in mandibular molars with less transportation than K3 and RaCe.
Loss of working length did not exceed 0.5 mm and was not affected by the use of .06 tapered instruments.
Bryant ST et al. Int Endod J 32:155, 1999.
Al-Sudani D et al. J Endod 32:1198, 2006.
Newer ProFile family of instruments is the Vortex (DENTSPLY Tulsa Dental).
The major change lies in the non-landed cross section, whereas tip sizes and tapers are similar to existing ProFiles.
Manufactured using M-Wire, Profile Vortex also have varying helical angle to counteract the tendency of non-landed files to thread into the root canal.
GT and GTX Files
Steve Buchanan in 1994.
This instrument also incorporates the U-file design and was marketed as ProFile GT.
The system was first produced as a set of four hand-operated files and later as engine-driven files.
Four tapers (.06, .08, .10, and .12).
The maximum diameter of the working part was 1 mm.
This decreased the length of the cutting flutes and increased the taper.
The instruments had a variable pitch and an increasing number of flutes in progression to the tip; the apical instrument diameter is 0.2 mm.
Instrument tips were noncutting and rounded, these design principles are mostly still present in the current incarnation, the GTX instrument.
The main differences are the NiTi alloy type used (M-Wire, manufactured by SportsWire, Langley, OK) and a different approach to instrument usage, emphasizing the use of the #20 .06 rotary.
Design features of a GT-file. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications
The GTX set currently includes tip sizes 20, 30, and 40 in tapers ranging from .04 to .08.
The recommended rotational speed for GT and GTX files is 300 rpm, and the instrument should be used with minimal apical force to avoid fracture of the tip.
Studies on GT files found that the prepared shape stayed centered and was achieved with few procedural errors.
A shaping assessment using μCT showed that GT files machined statistically similar canal wall areas compared with ProFile and LightSpeed preparations.
These walls were homogeneously machined and smooth.
Hata G et al. J Endod 28:316, 2002
Peters OA et al. Int Endod J 34:221, 2001.Park H: Oral Surg Oral Med Oral Pathol Oral Radiol Endod 91:715, 2001.
HERO 642, Hero Shaper
First-generation had neutral or slightly negative rake angles.
Second-generation systems were designed with positive rake angles, which gave them greater cutting efficiency.
HERO instruments (MicroMega, Besançon, France); the original system known as HERO 642 has now been replaced by HERO Shaper, with very little difference in the instrument design.
Cross sections of HERO instruments show geometries similar to those of an H-file without radial lands.
Tapers of .02, .04, and .06 are available in sizes ranging from #20 to #45.
The instruments are relatively flexible (the acronym HERO stands for high elasticity in rotation) but maintain an even distribution of force into the cutting areas.
HERO instruments have a progressive flute pitch and a noncutting passive tip.
Design features of a HeRO instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications
Research with HERO files indicates a shaping potential similar to that of the FlexMaster and the ProFile.
HERO Shapers were found to have a better centering ability compared to RaCe instruments in resin blocks.
Hülsmann M et al. Int Endod J 36:358, 2003. Garala M et al. Int Endod J 36:636, 2003.
Aydin C et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105:e92, 2008.
ProTaper Universal
The instruments were designed by Cliff Ruddle, John West, and Pierre Machtou.
Originally comprised just six instruments: three shaping files and three finishing files.
This set is now complemented by two larger finishing files and a set designed for retreatment procedures.
In cross section, ProTaper shows a modified K-type file with sharp cutting edges and no radial lands.
This creates a stable core and sufficient flexibility for the smaller files.
The cross section of finishing files F3, F4, and F5 is slightly relieved for increased flexibility.
A unique design element is varying tapers along the instruments’ long axes.
The three shaping files have tapers that increase coronally, and the reverse pattern is seen in the five finishing files.
The differences between Shaping and Finishing file shapes
Design features of a ProTaper instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
Tip diameter (mm)
Sx 0.19 At D9 = 1.1 mm
S1 0.185 At D14 =1.2 mm
S2 0.20 At D14 = 1.1 mm
Tip Diameter (mm) Taper (mm)
(D₀- D₃)
F1 0.2 0 7%
F2 0.25 8%
F3 0.30 9%
F4 0.40 5%
F5 0.50 4%
Cross section of Finishing files Triangular cross section of Shaping files
The finishing files have rounded noncutting tips.
The convex triangular cross section of ProTaper instruments reduces the contact areas between the file and the dentin.
The first is the preparation of a glide path, either manually or with special rotary instruments.
Optimal helical angle with variable pitch on the cutting flutes, designed to maximise efficiency and again prevent the file screwing into the canal.
The tip design is a modified non-cutting tip which acts as a guide in the root canal but does not cut.
A more lateral “brushing” working stroke. Such a stroke allows the clinician to direct larger files coronally away from danger zones and counteract any “threading-in” effect.
In a study using plastic blocks, the ProTaper created acceptable shapes more quickly than GT rotary, ProFile, and Quantec instruments but also created somewhat more aberrations.
Yun HH et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 95:228, 2003.
A study using μCT showed that the ProTaper created consistent shapes in constricted canals, without obvious preparation errors, although wide canals may be insufficiently prepared with this system.
It has been recommended that ProTaper be combined with less tapered, more flexible rotaries to reduce apical transportation.
Peters OA et al. Int Endod J 36:86, 2003. Javaheri HH et al. J Endod 33:284, 2007
Protaper Next
The convergence of a variable tapered design on a given file (ProTaper Universal), innovative M-Wire technology, and a unique offset mass of rotation.
Off-centred, rectangular cross section giving the files a unique, snake-like swaggering movement.
This improved action creates an enlarged space for debris removal, optimises the canal tracking and reduces binding.
X1, X2, X3, X4, and X5
Corresponding to sizes:17/04, 25/06, 30/07, 40/06, and 50/06, respectively.
Recommended speed is 300RPM with a torque from 4-5.2Ncm.
M-Wire technology: Improves the resistance to cyclic fatigue by almost 400% when comparing files of the same tip diameter, taper and cross-section.
Offset mass of rotation: Asymmetrical rotary motion and, at any given cross-section, the file only contacts the wall at 2 points.
Clinically, this provides 3 significant advantages: Reduced engagement due to the swaggering effect
which limits undesirable taper lock.
Affords more cross-sectional space for enhanced cutting, loading, and augering debris.
Allows any PTN file to cut a bigger envelope of motion compared to a similarly-sized file with a symmetrical mass and axis of rotation.
This means a smaller-sized and more flexible PTN file can cut the same-size preparation as a larger and stiffer file with a centered mass and axis of rotation.
K3
Dr. McSpadden; the Quantec 2000 files were followed by the Quantec SC, the Quantec LX, and the current K3 system (all by SybronEndo).
The overall design of the K3 is similar to that of the ProFile and the HERO in that it includes instruments with .02, .04, and .06 tapers.
The most obvious difference between the Quantec and K3 models is the K3’s unique crosssectional design: a slightly positive rake angle for greater cutting efficiency, wide radial lands, and a peripheral blade relief for reduced friction.
Design features of a K3 instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
Unlike the Quantec, a two flute file, the K3 features a third radial land to help prevent threading-in.
In the lateral aspect, the K3 has a variable pitch and variable core diameter, which provide apical strength.
This complicated design is relatively difficult to
manufacture, resulting in some metal flash
A round safety tip, but the file is about 4 mm shorter than other files
Tested in vitro, K3’s shaping ability seems to be similar to that of the ProTaper and superior to that achieved with hand instruments.
Bergmans L et al. Int Endod J 36:288, 2003.Schäfer E et al. Int Endod J 36:199, 2003.
FlexMaster
.02, .04, and .06 tapers.
The cross sections have a triangular shape, with sharp cutting edges and no radial lands.
This makes for a relatively solid instrument core and excellent cutting ability.
The overall manufacturing quality is high, with minimal metal flash and rollover.
Design features of a FlexMaster instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
Have rounded, passive tips; the tip diameters are 0.15 to 0.7 mm for size .02 instruments and 0.15 to 0.4 mm for size .04 and .06 files.
In addition to the standard set, the Intro file, which has a 0.11 taper and a 9-mm cutting part, is available
Several studies indicate that the FlexMaster allows centered preparations in both constricted and wider canals and that it performed on par with other systems.
Hübscher W et al. Int Endod J 36:740, 2003.
Hülsmann M et al. Int Endod J 36:358, 2003.
Weiger R et al. Int Endod J 36:483, 2003.
RaCe, Bio Race
The name, which stands for reamer with alternating cutting edges, describes just one design feature of this instrument
Light microscopic imaging of the file shows flutes and reverse flutes alternating with straight areas; this design is aimed at reducing the tendency to thread the file into the root canal.
Cross sections are triangular or square for #.02 instruments with size #15 and #20 tips.
The lengths of cutting parts vary from 9 to 16 mm
Design features of an RaCe instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200).C, Lateral view. D, design specifications.
The surface quality of RaCe instruments has been modified by electropolishing.
Two largest files (size #35, #.08 taper and size #40, #.10 taper) are also available in stainless steel.
The tips are round and noncutting
EndoSequence
The Sequence rotary instrument is produced by FKG in Switzerland and marketed in the United States by Brasseler.
This is another instrument that adheres to the conventional length of the cutting flutes, 16 mm, and to larger tapers, .04 and .06, to be used in a crown-down approach
Design features of a Sequence instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
A unique longitudinal design called alternating wall contact points (ACP) reduce torque requirements and keep the file centered in the canal
An electrochemical treatment after manufacturing, similar to RaCe files, that results in a smooth, polished surface.
This is believed to promote better fatigue resistance, hence a rotational speed of 600 rpm is recommended for EndoSequence.
Koch KA et al. Dent Clin North Am 48:159,2004.
Twisted File
In 2008, SybronEndo presented the first fluted NiTi file.
Manufactured by plastic deformation, a process similar to the twisting process that is used to produce stainless steel K-files.
According to the manufacturer, a thermal process allows twisting during a phase transformation into the so called R-phase of nickel-titanium.
The instrument is currently available with size #25 tip sizes only, in taper .04 up to .12.
Design features of a Twisted File (TF) instrument. A, Lateral view (scanning electron micrograph [SeM], ×50). B, Cross section (SeM, ×200). C, Lateral view. D, design specifications.
Twisted Files size #25 .06 taper were more flexible than ProFiles of the same size.
The manufacturer recommends a conventional crown-down technique after securing a glide path with a size #15 K-file.
Specifically, for a “large” canal, tapers .10 to .06 should be used, and in a “small” canal, tapers .08 to .04 are recommended.
Gambarini G et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105:798, 2008
Path Files
Mechanical glide path and Preflaring.
Available in 3 ISO sizes (013, 016 and 019) and 3 lengths (21, 25 and 31mm).
Flexible and resistant to cyclic fatigue, they offer many advantages compared to manual solutions
NiTi – Square Section – 2% Taper
High strength against cyclic fatigue
Flexibility
Tip design (transition angle reduction)
Reduced risk of ledges and canal transportation
PathFile™ K-File
Helio P. Lopes et al.
(Buckling Resistance of Pathfinding Endodontic Instruments):
The results indicated that the buckling resistance decreased in the following order: C+ file > C-Pilot file > PathFile
Considering that buckling resistance may influence the performance of instruments during the negotiation of constricted canals, the C+ files showed significantly better results than the other instruments tested.
Helio P. Lopes et al . J Endod 2012;38:402–404
Self-adjusting file
The instrument is made as a hollow, thin NiTi lattice cylinder that is compressed when inserted into the root canal and adapts to the canal’s cross-section.
It is attached to a vibrating handpiece.
Continuous irrigation is applied through a special hub on the side of its shank.
The SAF instrument adapted into a root canal that was initially prepared with #20 K-file.
Right: A #20 K-file in the canal.
Left: The SAF file in its relaxed form.
Center: The SAF file inserted into the same narrow canal.
It will apply delicate pressure on the canal wall, attempting to resume its original shape.
The abrasive surface and details of the lattice of the SAF instrument.
The extreme elasticity is the total of the elasticity of each of the delicate NiTi segments.
The VATEA continuous irrigation unit used with the SAF instrument.
The unit has two containers and provides a continuous flow (low pressure, 5 ml/min) of either irrigant (i.e., sodium hypo-chlorite and edTA) through double silicon tubes that are connected to the hubs on the front of the device.
It is controlled by finger-operated switches located on the handpiece.
A micro–computed tomography (microCT) analysis of the operation of the SAF instrument in a flat canal with extremely oval cross-section.
Right: Buccolingual and mesiodistal views of the root canal reconstructed from microCT.
Left: Cross-sections at 4 and 6 mm from the apex.
Red: before, blue: after treatment.
ENDO-EZE reciprocating files
The endo-eze file system (Ultradent, South Jordan, UT) is a recently introduced addition for Giromatic handpieces.
The set has four instruments that are designed to clean the middle third of the canal.
The sizes and tapers are 0.10 #0.025 taper, 0.13 #0.35 taper, 0.13 #0.45 taper and 0.13 #0.06 taper.
The use of stainless steel hand instruments is suggested for the apical third of the canal
The WaveOne single-file reciprocating system
Single-use, Single-file system to shape the root canal completely from start to finish.
M-Wire technology. Improving strength and resistance to cyclic fatigue
by up to nearly four times in comparison with other rotary NiTi files.
At present, there are three files in the WaveOne single-file reciprocating system available in lengths of 21, 25 and 31 mm
The WaveOne Small file is used in fine canals. The tip size is ISO 21 with a continuous taper of 6 %.
The WaveOne Primary file is used in the majority of anals. The tip size is ISO 25 with an apical taper of 8 % that reduces towards the coronal end.
The WaveOne Large file is used in large canals. The tip size is ISO 40 with an apical taper of 8 % that reduces towards the coronal end
The instruments are designed to work with a reverse cutting action.
All instruments have a modified convex triangular cross-section at the tip end, and a convex triangular cross-section at the coronal end . This design improves instrument flexibility overall
WaveOne apical cross-section, modified convex triangular
WaveOne coronal cross-section, convex triangular.
WaveOne variable pitch flute increases safety
The specially designed NiTi files work in a similar but reverse “balanced force” action using a pre-programmed motor to move the files in a back and forth “reciprocal motion”
The counter-clockwise (CCW) movement is greater than the clock-wise (CW) movement. CCW movement advances the instrument, engaging and cutting the dentine.
CW movement disengages the instrument from the dentine before it can (taper) lock into the canal.
Three reciprocating cycles complete one complete reverse rotation and the instrument gradually advances into the canal with little apical pressure required.
Clinical procedure
Endo Express and Safe Sider
Reciprocating Motion.
SafeSiders have 16 flutes compared to 24 flutes for files.
Less flutes leads less engagement with the walls of the canal which means less resistance, binding and virtually no instrument separation.
Flat-side of the SafeSider:Act as chisels in the clockwise and counter
clock-wise motion allow to remove debris easily.
SafeSiders are safely used at least 3 times more than NiTi instruments before they are discarded.
Revo-S Sequence
The asymmetrical cutting profile of the Revo-S facilitates penetration by a snake-like movement, and offers, a root canal shaping which is adapted to the biological and ergonomic imperatives.
It is composed of only two instruments for apical penetration (SC1 and SC2), and a recapitulating and cleaning instrument (SU)
Revo-S instruments for apical progression (SC1 & SC2), & cleaning (SU).
The working lengths are adapted for a crown-down preparation. The asymmetry alternates with the symmetry, in order to optimize the canal penetration (SC1), the strength (SC2), & the cleaning (SU)
Apical finishing instruments with an asymmetrical cross section allowing the final shaping of the apical third.
The selection of preparation diameter adapted to most clinical cases, and Cleaning without pushing debris beyond the apical foramen
Mtwo VDW, Munich, Germany
The standard set for this system includes four instruments with variable tip sizes ranging from #10 to #25, and tapers ranging from .04 to .06 (size 10/.04 taper, size 15/.05 taper, size 20/.06 taper, size 25/.06 taper
After this basic sequence, that gives the canal a #25/.06 shape, the system is conceived to permit three different approaches to root canal preparation.
The first sequence allows clinicians to achieve enlarged apical diameters using the size 30 (.05) taper, 35 (.04) taper or 40 (.04) taper;
The second leads to a .07 taper that can facilitate vertical condensation of gutta-percha, maintaining a size #25 apical preparation;
The third implies the use of the Mtwo apical files
SEM image of Mtwo instrument cross-section, showing the two blade cutting surfaces resulting in an “Italic S” design.
.
The Helical angle (HA) of Mtwo instruments is variable and specific for the different files
HA is more open (greater) for the bigger sizes (less flutes for instrument length), and it decreases for the smaller sizes (more flutes).
This determines a greater cutting efficiency for the bigger sizes and a greater mechanical resistance together with a tendency to advance in the canal for the smaller ones.
The HA is variable in the same instruments, it increases from the tip to the handle as does the spiral pitch,
While it is constant for the smaller files, especially for the #10 .04, the first rotary instrument that is introduced in the root canal.
The variable HA reduces the tendency of the instrument to be sucked down into the canal
The MtwoR instruments are specifically designed for the retreatment of obturation materials.
The retreatment files are Mtwo R 15/.05 and Mtwo R 25/.05, presenting an active tip that allows clinicians to easily penetrate obturation material.
Conclusion:
An explosion in knowledge and technology has created an exciting time in the specialty of endodontics.
New instruments and materials seem to appear faster than clinicians can learn about the preceding versions.
This has created an educational challenge for practitioners, universities, and manufacturers, requiring a greater degree of cooperation among these groups than ever before.
Clinicians should only use those instruments and materials
that have been shown safe and effective by independent studies.
Cohen and Hargreaves. Pathways of pulp,10th edition
Most systems include files with tapers greater than the #.02 stipulated by the ISO norm.
The Light-Speed LS1 and LSX are different from all other systems;
The ProTaper, RaCe, and Twisted File have some unique features; and most other systems have increased tapers.
Minor differences exist in tip designs, cross sections, and manufacturing processes, but the clinical effects of these modifications currently are unknown.
Even in vitro, tests have only begun to identify the effect of specific designs on shaping capabilities, and differences in clinical outcomes in regard to these design variations appear to be minimal.
Cohen and Hargreaves. Pathways of pulp,10th edition
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