2. Use stainless steel instruments - files
files used manually
files made by twisting wires of square,
triangular or diamond cross section
These have ISO taper
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3. ISO stands for
International Standards Organization
Taper is the amount by which the
diameter of an instrument
increases from tip to handle
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4. This is the taper set by the ISO
It is set at 0.02 per mm
This is commonly referred to
as
02 taper
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5. 02 taper does not match the
taper of root canals
Root canals have tapers close to
04, 06 or even 08
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6. By using a lot of instruments (files)
in complex protocols e.g.
Crown Down, Step Back
Techniques
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7. A series of files used from coronal to
apical sequentially with recapitulation
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8. S/S instruments have to be
used in reciprocating action
i.e. rotate clockwise, then anti-clockwise
or in push - pull action
If these are rotated continually
in one direction, these fracture
Not very flexible
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9. Push - pull action leads to
ledge formation in root canals
This action also pushes debris
into the canal causing
blockages
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10. By using these files manually in
reciprocating action
i.e. Balanced Force Technique
But this is a very slow process
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11. By using Greater Taper GT files
The Greater Tapers matchhRRoot Canal tapers
tC
needing fewer files
By making them of Nickel Titanium instead
of S / S so that these are flexible and can be
rotated continually in one direction without
risk of fracture
Thus NiTi GT Rotary instruments
were born
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12. Made of Nickel Titanium alloy
NiTi wires cannot be twisted
Therefore, made by machining - makes
these files very expensive
These have a Taper > ISO Taper
Tapers of 04, 06, 08, 10 & even 12
These tapers are similar to taper of root
canals
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18. Invented by Dr. Stephen
Buchanan of USA in the
1980’s
Has revolutionised
Endodontic Practice
Used in rotating action
with special hand piece
with a low speed, high
torque motor
Now several designs and
brands available
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20. NiTi exists in 2 forms with different
properties
Martensite
Low temp form, low modulus, high strain
Austenite
High temp form, high modulus, low strain
Shape memory
NiTi exhibits super elasticity
Under stress, martensite austenite
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21. Bends and returns to original shape
Martensite Austenite Martensite
Can negotiate curved root canals better
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22. A curved canal
prepared with
NiTi files
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22
24. Note Triple U
cross-section of
the rotary file
collect debris
Flat radial lands
keep the file
centred on the
natural root
canal while
enlarging it
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25. RaCe files have a
triangular cross-
section
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26. File tip is dome-
shaped to prevent
ledge formation &
canallttransportation
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27. Progressively Tapered files
Differing percentage of taper along
the length of the file
Makes the file even more flexible
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34. Fewer files needed due to better taper
Faster completion of canal preparation
Flexible, enabling easy use in curved
canals
More predictable outcome
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35. Mandibular
second molar with
abrupt curvature
of the distal canal.
Note the apical
control despite
the conservative
canal enlargement
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