This presentation is about all the techniques we use to instrument during root canal treatment. includes hand and engine driven techniques and everything an undergraduate and postgraduate students need to know about instrumentation techniques.

1. Instrumentation techniques
Dr. Hamza
Department of Operative Dentistry.
Armed Forces Institute of Dentistry.
NUMS,Rawalpindi.

2. Hand instrumentation
• The modified double flared approach
• File manipulation: the filing and reaming
motions

3. The modified double flared approach
• Preassessment of the case
• Field isolation with rubber dam
• Creation of straight-line access
• Irrigation of the pulp chamber (2.5–5% NaOCl)
• Localization of root canal orifices and penetration with
flexible K-files size 15–20 (watch-winding) (if necessary
start with smaller files)
• Careful shaping of the straight coronal portion (preflaring)
with the alternating use of hand files, Gates–Glidden burs
and Ni–Ti rotary files (if preferred)
• To avoid ledge formation:
– use only light apical force
– work at different depths
– vary between different file sizes
– recapitulate with a small instrument

4. • Reconfirm straight-line access (thus no strain on the file
when placed coronally from the curve)
• Crown-down clearance up to 3–4 mm from the estimated
working length (create and confirm glide path first)
• Keep using irrigants; do not work in dry conditions
• Working length determination: size 15 flexible K-file (if
necessary start with smaller files) with balanced force
motion to the apical constriction (use an electronic apex
locator)
• Create and confirm glide path (flexible K-file size 15–20)
• Apical preparation to size 30–35 (6% taper)
• Apical gauging (if necessary proceed with larger files)
• Final irrigation

5. File manipulation: the filing and
reaming motions

6. Filing motion
• The filing motion is especially suitable to the Hedstroem file
• It removes dentin from the root canal wall when the
instrument is inserted to a given length and then pressed
against the canal walls at the same time as it is drawn
coronally
• This action is performed and resumed with certain amplitude
• There are difficulties with this method
– The tendency to grooving into the dentinal canal wall, without a
conscious effort being made to move the file circumferentially
– Packing of debris ahead of the instrument tip, which may block the
root canal
• The push–pull motion is also possible with K files but should
be restricted to size 15 (or less) as rasping with larger
instruments may cause iatrogenic damage

7. Reaming motion
• The reaming motion denotes a clockwise or
counterclockwise rotation of the instrument in
the root canal
• It is the preferred method for reamers and
(flexible) K-files
• Types of reaming motion
– Watch winding
– The balanced Force Technique

8. Watch winding motion
• Watch-winding is a clockwise/counter-clockwise
rotation of the instrument through an arc of 30–
90° while advancing the instrument into the
canal
• The reciprocating back and forth rotational
movement alternately pulls the instrument into
the canal (clockwise), and then (counter-
clockwise) cuts the engaged dentin
• At a certain point watch-winding will not
advance the instrument further into the canal

9. • In many cases, three to five push– pull filing
strokes will loosen the shaft and allow watch
winding to advance the instrument further
apically.
• The watch-winding method is less aggressive
than the original “quarter turn–pull” and should
be used with light apical pressure
• With precurved stainless steel instruments this
technique is extremely useful for initial
negotiation of root canals, especially those that
are severely curved or narrow

10. The Balanced Force motion
• The balanced force motion was devised by Roane
and coworkers and endorsed by Charles and
Charles on the basis of a mathematical model
• It is essentially a reaming action using clockwise
movement to insert the file and counter-clockwise
movement to remove dentin
• The file is placed into the root canal until it binds
against the wall
• The file is then rotated through 60–90° with light
apical pressure
• This creates threads within the dentin

11. • The instrument is moved counterclockwise through 120–
360° with mild apical pressure which crushes and breaks off
the dentin threads and enlarges the root canal
• A final clockwise rotation allows flutes to be loaded with
debris and removed from the root canal
• This technique has been shown to be efficient and less
prone to cause iatrogenic damage
• The technique must be used with flexible K-files that are
not precurved
• A technique of reverse balanced force instrumentation has
been developed for use with GT hand files where the flutes
of the shaft are machined in an opposite thread to normal
files

13. Engine driven instrument handpieces
• Engine-driven instruments can be used in
three types of contra-angle hand pieces
– Full rotary hand piece, latch or friction grip
– Reciprocating/quarter-turn hand piece
– Special hand piece that imparts a vertical stroke
but with an added reciprocating quarter turn that
‘‘cuts in’’ when the instrument is stressed

14. Nickel–titanium rotary
instrumentation
• Ni–Ti rotary systems advocate
preflaring of the coronal portion of the
root canal and relocation of the canal
orifices with Gates–Glidden burs prior
to deeper instrumentation
• Pre-flaring can also be carried out with
Ni–Ti rotary files such as orifice
openers or accessory files from the
system
• These instruments for initial shaping
tend to produce centered preparations,
however; anti-curvature relocation of
the canal orifice is more difficult to
obtain

15. • Some of the newest systems (e.g. ProTaper)
seem to behave differently.
– their active cutting design
– lacking radial land areas
– Removes dentin more selectively
– Allows coronal relocation
• Meticulous manipulation of this file is,
however, essential to get the particular effect
and to avoid strip perforations

17. • Continuous reaming motion by
automated hand pieces driven
by electrically driven motors
• Ni–Ti rotary files exist in an
austenitic phase that
transforms to a martensitic
structure on stressing at a
constant temperature
• In this stress-induced
martensitic phase only a light
force is required for bending

18. • Limited and constant stress is needed for optimal
performance
• This is accomplished by using constant speed (rpm) and
light apical pressure
• Ni–Ti rotary systems have a speed range (rpm) and torque
limits (N/cm²) for optimal performance that are specified
by the manufacturer for each file separately
• Above the allowed torque, plastic deformation and
instrument fracture may occur
• If the torque-limit value is set too low, the file will stop
cutting even when safe
• Increased speed (higher rpm) seems to increase shaft
stiffness

19. Important points of use of Ni Ti
Rotary instruments
• Brushing motion
• “pecking” movement
• Smooth steady pressure
• Observe the recommended sequencing of files
• used with a light touch and minimal apical
pressure

20. • One must not rotate the file for too long in the
canal and during this period of time, the
instrument must not stop rotating
• Use of an irrigating solution while cleaning and
shaping the root canal system is an accepted
practice
• Irrigation plays an important role in lubricating
the canal and in facilitating chip and debris
removal
• Some irrigants also serve the very important
purpose of root canal disinfection

21. Manual Hand Instruments

22. Dimensions of hand files

23. K Files Cross section

24. K Reamers Cross section

25. H Files Cross section

26. Ni Ti Files
• Nickel–titanium’s unique property of super-
elasticity may allow hand (and rotary) files to
be placed in curved canals with less lateral
force exerted
• Such files are made from
– Nitinol,1 an equiatomic Ni–Ti alloy (using about 55
wt% Ni and 45 wt% Ti, and substituting some Ni
with less than 2 wt% Co) with a low modulus of
elasticity and a greater resistance to plastic
deformation

27. NI TI Rotary Files

28. Establishment of working Length
• Determination of the apical limit for preparation
of root canals (working length) is a most critical
procedural step
• Canals should be instrumented neither too short
nor too long
• Instrumentation short of the canal exit risks
leaving inflamed tissue and infectious elements in
the root canal space, while instrumentation
beyond the apical foramen may force infectious
debris into the periapical tissue compartment
and cause an endodontic flare-up

29. • Over preparation may also pave the way for
overfilling with lingering foreign body reaction
and incomplete regeneration of the
supporting tissues as a result
• It is believed that the apical termination of the
intervention should be at the apical
constriction because this location indicates
the junction between the periodontal and
pulpal tissues

31. Methods for determination of
Working length
• Working length by Radiographs
• Working length by Apex Locators
• Working Length by Paper point test
• Working length by perception of pain

32. Radiographic method
• An estimate of the approximate
length of the tooth is made
from a preoperative parallel
radiograph
• A file is placed in the root canal
about 1 mm short of this
estimated length ensuring that
a coronal reference point is
selected that is reproducible,
stable and durable
• The file should be large enough
to be visible on the radiograph
(e.g. size 10 but size 08 may also
suffice)

33. • A parallel radiograph is then
taken
• In teeth with multiple canals,
diagnostic files should be placed
in all canals and a single view
taken to minimize exposure to
radiation
• Once a parallel view periapical
radiograph of the tooth with
diagnostic file(s) in the canal has
been obtained, working length is
calculated taking account of
image distortion by comparing
the actual and radiographic
distance between the tip of the
file and the reference point
indicated by the rubber stop

34. • In most cases, the tip of the file
will be short of the radiographic
apex
• This is often accepted as the
length of the canal if the
distance is within 1 mm
• If the discrepancy is greater
than 1 mm, then the distance
between the file tip and the
radiographic apex should be
measured and 1 mm subtracted
from this measurement (as in
the central incisor)
• This residual discrepancy is
added to the length of the
diagnostic file to give the
estimated length of the canal

35. • In some cases, the file
may be longer than the
radiographic apex, in
which case the distance
between the file tip and
a point 1 mm short of
the radiographic apex
should be measured
• Subtracting this figure
from the length of the
diagnostic file will give
the length of the canal

36. Working length by Apex Locators
• Electronic apex locators in theory enable the
location of the true position of the apical
terminus, utilizing the fact that root canals, in
common with other tubes with one end
immersed in an electrolyte solution, exhibit
certain electrical characteristics that are relatively
constant
• Impedance value at the apical foramen that is
between the periodontal ligament and the oral
mucosa, measured via the root canal is a relative
constant

37. Functioning of EAL
• EALs work by applying an alternating
current between two electrodes, one of
which is attached to the file and the
other via a clip to the lip or cheek
mucosa
• The frequency of this current, which also
influences impedance, is usually fixed in
a given make of instrument but differs
between makes
• As the file is passed down the canal, the
EAL measures the impedance and
compares the value with its calibrated
standard
• A countdown scale indicates a “zero” or
“apex” reading when the calibrated
value is matched
• All currently available conventional EALs
use this principle but display the
information differently

38. • The current generation of EALs
has overcome the problem with
electrolytes in root canals by
measuring the impedance at
multiple current frequencies
• The Root ZX (J Morita, Kyoto,
Japan) compares the ratio of
impedance at two frequencies to
derive the apical position
• The Elements Diagnostic Unit
(SybronEndo) ( fourth generation
apex locator) measures
resistance and capacitance
separately rather than the
resultant impedance
• The Raypex® 5 (VDW) which
also uses multiple frequencies,
claims to be a fifth generation
apex locator with greater
accuracy

39. Tactile method
• Tactile sense alone can be used to gauge the
position of the apical terminus
– Not all teeth possess an apical constriction due to the
presence of apical resorption caused by apical
periodontitis
– Second, the ability to gauge the apical constriction
relies on the preexistence of a natural canal taper that
has a minimal constriction only at the termination of
the canal (four distinct patterns of apical constriction)
– Third, the tactile detection of the apical constriction
relies upon the selection of a file size that will first
bind only at the apical constriction

40. Paper-point method
• Use of a sequence of paper points that show
the position of the apical foramen by virtue of
the junction of tide-mark of the blood-wetted
and dry tip of the
• it is unreliable by itself because of seepage of
exudate or blood into the canal and by
capillary action along the paper point paper
point