detailed knowledge related to rotary endodontic instruments including history, properties,advances,importance etc.

2.  Part:1
 Introduction
 History
 Why Rotary Instrumentation?
 Properties of Nickel-Titanium
 Advances in Nickel-Titanium metallurgy.
 Basic design features of rotary file
 Tip
 Taper
 Helical angle
 Radial land
 Rake angle
 Pitch

3.  important relationships of the components of file
designs and canal anatomies that enable us to
improve our technique?
 Breakage
 What is torsion/torque ?
 Sotokawa classified Instrument damage
 Gates-Glidden Drills

4.  Endodontic instruments play a significant role in the
success of endodontic treatment starting from the
preparation of the access cavity to the final
obturation of the root canal space. A continuously
tapering funnel shape with the smallest diameter at
the end point and the largest at the orifice has been
deemed to be the most appropriate canal shape for
filling with gutta-percha and sealer.
Rotarysystem:an insight JDOFR vol.10;issue:2;jul-dec2014

5.  Successful endodontic treatment relies upon
endodontic instruments used for cleaning and shaping
of the root canal system, which ultimately determines
the clinical outcome.
 Rotary systems have proved to be safer, quicker and
more efficient over the conventional instruments.

6.  1838-Edward Maynard-development of the first endodontic
hand instrument.
 The first description of the use of rotary devices- by
Oltramare.(Oltramare in 1892 use a fine needles with a
rectangular cross-section, mounted them into a dental hand
piece and were passively introduced into the root canal to the
apical foramen then the rotation started.)

7.  1889 William H. Rollins developed the first endodontic
handpiece for automated root canal preparation.
 1928 - ‘Cursor filing contra-angle’ was developed by the
Austrian company W&H(combined rotational and vertical
motion of the file.)

8. 1958 –Racer handpiece (In 1958 W&H company start
Marketing The Racer-hand piece in Europe and worked
with a vertical file motion.)
1964 -Giromatic handpiece (a reciprocal 90º rotation)
Canal Finder was the first endodontic handpiece with a
partially flexible motion.

9.  enhanced ability to collect and remove debris
from the canal system.
 better control for maintaining the central axis of
the canal, reducing the incidence of ledging or
perforating.
 reduction in the time required for
instrumenting the canal.

10.  Historically, carbon steel and stainless steel instruments
were used for root canal instrumentation.
 In 1988, Walia and colleagues introduced nickel-titanium
(NiTi) files to endodontic.
 Since then, many NiTi file systems have been developed.
Rotary NiTi instruments have become popular as they can clean
and shape root canals with fewer procedural errors and more
predictability than stainless steel hand files.

11.  Nickel–titanium (NiTi) was developed in 1964
by Buehler et al in the Naval Ordnance
Laboratory (NOL)
 55 NiTiNOL
 60 NiTiNOL

12. Nickel titanium is termed an exotic metal because it does
not conform to the normal rules of metallurgy. As a super-
elastic metal, the application of stress does not result in the
usual proportional strain other metals undergo. When stress is
initially applied to nickel titanium the result is proportional
strain. However, the strain remains essentially the same as the
application of additional stress reaches a specific level forming
what is termed loading plateau: during which the strain
remains essentially constant as the stress is applied.
Eventually, of course, excessive stress causes the file to fail

14. Super elasticityShape memory and

15. Stainless steel
Excellent
flexibility
Conforms to
canal curvature
Plastic
deformation
Less flexible
Straightens and
transport canal
Permanent
deformation
Nickel titanium

17. Advances in Nickel-Titanium Metallurgy
1) M-wire NiTi - Developed by Dentsply Tulsa
Dental Specialties (Tulsa, OK, USA)
• Advantage: This material has greater flexibility and
an increased resistance to cyclic fatigue when
compared to traditional NiTi alloys.

18. 2) R-phase NiTi – Developed by SybronEndo
(Orange, CA, USA)
• Advantage: Files have reduced stiffness and
more fracture resistance compared to standard
NiTi files.
3) Controlled-Memory (CM) NiTi :
•Advantage: Files have superior cyclic fatigue
resistance and increased torque strength over
traditional NiTi files.

19. Strategies for Improved Nickel-Titanium
Instruments
Electropolishing the machined surfaces.
Ion implantation to create harder surfaces, and
use of special surface coatings.
Boron-ion implantation more than doubled the
surface hardness of Nitinol at the nano-indentation
depth of 0.05 µm, yielding a hardness value greater
than that of stainless steel.
(Lee DH et al. J Endod 1996;22:543-6)

20.  Schafer used a physical vapor deposition
(PVD) process to create a titanium nitride
surface coating on NiTi instruments.
 Surface-coated instruments had greater
cutting efficiency (penetration into plastic
samples with cylindrical canals) compared
with control instruments.
 Their cutting efficiency was not altered by
repeated autoclave or sodium hypochlorite
sterilization.
(Schafer E. Et al. Int Endod J 2002;35:867-72)

21. Does the quality of manufacturing make much difference ?
Yes !
the quality of manufacturing is the most basic consideration for
determining the success or failure of files independent of its
composition or design.
Less than ideal manufacturing quality controls result in the
formation of micro-cracks and defects along the surface of a file.
Cracks can propagate to failure at a stress level lower than the
stress ordinarily encountered during instrumentation and other
defects can cause stress concentration points that lead to file
failure and jeopardize endodontic success.

23. Active/cutting
Active tips: It has cutting edges
on its surface and can help to
shape the narrow, calcified
canals. However, it has a
disadvantage of accidental
apical perforation or
transportation. E.g. Quantec
file.

24. Passive/non cutting
No cutting edges present and
create a concentric circle at the
end of the root. Eg.
ProfileGT,lightspeed ,etc

26.  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.

27.  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

28.  Taper denotes the per millimetre increase in file
diameter from the tip towards the file handle.

29.  constant taper:
E.g.profile system .
 Varying or graduating
taper: E.g. Quantec
system.
 Progressive taper: E.g.
ProTaper system .

30. Feature is incorporated to :
1. reduce canal
transportation
2. screwing in forces
3. supports the cutting edge
4. Limits the depth of cut.

31. The angle the cutting edge forms with the long axis of the
file.
Files with a constant helical flute angle allow debris to
accumulate, particularly in the coronal part of the file.
Additionally, it will be more susceptible to the effect of
“screwing in” forces.
By varying the flute angles, debris will be removed in a
more efficient manner and the file will be less likely to
screw into the canal
Helix angle:

32.  In the K 3, the helical angle increases from the tip to
the handle.
In RaCe file is unique and utilizes an “alternating
helical design” that reduces rotational torque.
This design feature also reduces the tendency of the file
to get “sucked into” the canal.
(zarna sanghv et al. the jol of ahmedabad
dental college and hospital; 2011 ;2(1))

34. Negative angle results in
scraping action
Positive angle results in
cutting action

35. If the flutes of the file are symmetric, the rake
angle and the cutting angle are essentially the
same.
Neutral or zero rake angle: When the face
of the blade coincides with the radial line it is said
to be neutral or zero rake angle (planing). E.g.
LightSpeed, Greater taper (GT) file systems.

40. WaveOne variable pitch flute
increases safety
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
K3 file has been designed with
constant tapers, but with variable
pitch and helical angles. The result is
a dramatic reduction in the sense of
being “sucked down into” the canal.

41. In the most basic terms , the strength of a file is due to
the cohesive forces between atoms. As forces that tend to
deform a file are increasingly applied, the forces to separate
atoms increase and their attractions decrease.
force of
separation
force of
attraction

42.  fracture of files usually can be characterized in
two ways.
1. One cause of fracture is accompanied by an apparent
deformation of a file and the separation occurs as a result of
slippage between the planes of its crystalline boundaries,
most often due to the excessive forces of torsion .
2. Another fracture may occur across the grain of the metal
with little or no apparent deformation.This type of fracture
can be seen as a result of fatigue most often caused from the
excessive stresses .
Of course, most fractures are a combination of different
forces of separation.

43. axial force of being twisted when one part of a file rotates at a
different rate than another part.
When a file resists rotation during hand instrumentation with
conventional .02 tapered files, excessive torque can usually be
tactilely perceived and file breakage can usually be avoided.
 even the use of torque limiting handpieces during rotary
instrumentation does not provide the means for adjusting to
varying circumstances(curvatures,the amount of file
engagement,nor the diameters of the file that are engaged)
 Any excessive torque can not always be avoided preset torque
limitations.

44. On the other hand, the torque limits can be set so low that
file failure would be difficult, but effective canal enlargement
would also be limited.
Understanding the factors that cause excessive torque is the
most reliable means for avoiding torsion failure.
Causes of torsion stress :
(1) the force of cutting, specifically, how effectively a chip is
formed and deflected from the wall of the canal.
 (2) the force of screwing-in due to the spiralled blades that
become engaged in the wall of the canal without deflecting the
chips that are formed.

45.  Abrasion of rotating accumulated debris against
the canal wall increases torsion stress. The file
efficiency is decreased when the debris prevents the
cutting edge from engaging the canal wall.

46. (3) the force of abrasion of the non-cutting surface of the file
against the wall of the canal
(4) the force of distortion resulting from rotating in curvatures
(5) the force the debris exerts on the wall of the canal as it
accumulates in the flutes.
Incorporating designs to reduce any of these forces increases the
file’s efficiency.
. Another approach is to provide designs that can accommodate
greater forces, although the efficiency may remain unchanged.

47. Type I : Bent instrument.
Type II : Stretching / straightening of twist contour.
Type III : Peeling off metal at blade edges.
Type IV : Partial clockwise turn.
Type V : Cracking along axis.
Type VI : Full fracture.

48. 1. A file with a more efficient cutting design requires less
torque, pressure or time to accomplish root canal
enlargement.
2. In a straight canal, the ability of a file to withstand torsion is
related to the square of its diameter.
3. In a curved canal, the ability of a file to resist fatigue has an
inverse relationship with the square of its diameter.
4. The torque required to rotate a file varies directly with the
surface area of the file’s engagement in the canal.

49. 5. Fatigue of a file increases with the number of rotations of
the file and the degree of curvature of the canal.
6. To improve efficiency, the smaller the surface area of a file
engaged in the canal, the greater the rotation speed should
be.
7. The greater the number of flutes with similar helix angles,
the greater tendency a file has to screw into the canal and
become bound.
8. Less canal transportation occurs with a file having greater
flexibility, an asymmetrical cross-section design, and/or a
land.

50.  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 should be used at the speed of
750 to 1500rpm in brushing
strokes.
 GG instruments should be used
only in the straight portions of
the canal, and they should be
used serially and passively.

51.  Uses:
1. Coronal flaring during RC preparation.
2. Enlarge root canal orifices.
3. Removal of lingual shoulder during access preparation of
anterior teeth.
4. During retreatment cases or post sapce prepration for
removal of gutta percha

52.  Flexogates are modified gates-gliddens.
 They are made up of NiTi.
 They are most flexible and used for apical prepration.
 Rotary instruments used mainly for post space prepration.
 They have safe ended non-cutting tip.
 Tip diameter varies from 0.7 to 1.7 mm .
 Should be used in brushing motion.