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ENDODONTIC INSTRUMENTS
Introduction and History
Endodontic treatment is based on the principles of debridement,
sterilization, and obturation of the root canal system.
However, successful treatment is dependent on the complete
removal of pulp tissue and pulp remnants, bacteria and bacterial
components from the pulp space.
Cleaning and shaping of the root canal in turn depends on various
factors like:
- Type of instrument used.
- Material.
- Techniques.
- Operator’s skill
Earlier, for the manufacture of root canal instruments, the
primary focus was mainly on 2 materials i.e.
- Carbon steel (i.e. a round, tapered piano wire was used)
- Stainless steel.
The stainless steel wire is ground along its long arms into a 4-
sided (square cross-section) or 3 sided (angular cross-section) tapered
1
shaft that is twisted into flutes. The number of flutes twisted into each
blade of a similar sized-instrument determines whether that instrument is
a reamer (less flutes) or a file (more flutes).
Before 1958, endodontic instruments were manufactured without
benefit of any established criteria. There was little uniformity in quality
control or manufacture, no uniformity existed in progression from one
instrument to the next, and there was no co-relation of instruments and
filling materials in terms of size and shape.
In 1959, a new line of standardized instruments and filling
material was introduced by Ingle and Levine.
i) Instruments shall be numbered from 10 to 100, the numbers to
advance by 5 units to size 60, then by 10 units to size 100.
ii) Each number shall be representative of the diameter of the
instrument in hundredths of a mm at the tip. e.g. No. 10 is
10/100 or 0.1mm at the tip.
iii) The working blade (flutes) shall begin at the tip, designated
site D1, and shall extend exactly 16mm up the shaft,
terminating at designated site D2.
The diameter of D2 shall be 32/100 or 0.32mm > than that of D1,
2
for e.g. No. 20 reamer 0.2 at D1
0.2+ 0.32 = 0.52mm at D2
This sizing ensures a constant increase in taper of 0.02mm per
mm for every instrument regardless of the size.
In addition, instruments handles have been colour coded for
easier recognition.
The 1S0 slightly modified Ingle’s original standarization.
i) Addition of D3 3mm from D1
ii) Specifications for shapes of the tip 75° tip ±15°
Instrument sizes should increase by 0.05mm at D1 between
No.10-60 e.g. No. 10,15 and 20 and by 0.1 from 60-150.
In January 1976, the American Standards Institute granted
approval of “ADA specification No. 28” for endodontic files and
reamers.
ADA spec. No. 28 (JADA, 1989, 118; 239) stated (finally revised
in March 81).
a) Instrument sizes 06 and 08 and 110 to 150 were added to the
original standardization.
3
b) D1 and D2 were changed to D0 and D16 respectively, to clarify in
terms of mm from the tip.
D0 at the point of the tip.
D16 measured 16mm from the tip.
Instruments are available in lengths of:
21mm
25mm
28mm
30mm
Reamers are also available in 40 mm length for use in preparing
root canals for endodontic implants.
SCAN FIGURE
Classification of Instruments
I According to Grossman
a) Exploring instruments –
i.e. to locate the canal orifice and determine its
patency Endodontic explores
Smooth broaches
b) Debriding instruments
4
i.e. to extirpate the pulp and remove any
foreign debris Barbed broach
c) Shaping instruments
i.e. to shape the root canal laterally and apically Reamers
Files
d) Obturating instruments
i.e. to cement and pack gutta-percha into the root
canal Spreaders
Pluggers
Lentulo-spirals
II. International standards organization (ISO) has grouped root canal
instruments according to their use
Group I Hand use only Files K-type (Kerr)
H-type (Hedstroem)
Reamers – K-type
Broaches
Pluggers
Spreaders
5
Group II : Engine driven latch-type.
Same design as Group I but made to be attached to a handpiece
(includes paste fillers also).
Group III: Engine driven latch-type – Drills / Reamers
Crates-Glidden Peeso A, D, O, K, O, T
(G-type) (P-type) (M-type reamers)
Group IV: Root canal points Gutta percha
Silver
Paper
III. According to Stock
Instruments can be classified as:
Twisted Machined
- K-files - H-file
- K-reamer - Flex-R
- K-flex - Heliapical
- Flexo - Canal Master
- Zipper Flexicut - Flexogates
- McSpadden Engine file
K-type instrument, Reamer/Files – OHP
First designed by Kerr manufacturing Co. in 1915.
6
These are the most widely copied and extensively manufactured
endodontic instrument, world-wide.
Now made of stainless steel.
Are produced by grinding graduated sizes of rounded “Piano”
wire into either a square or triangular configuration.
Cutting edges on spirals are then given where the instrument is
grasped by a machine and twisted counter-clockwise.
Files Reamers
Given tighter flutes Loose spirals
(1.93-0.88 mm) (0.80-0.28mm)
Square blank Triangular blank
- Are generally used for smaller, fragile instruments.
- Resists # better
- Used for larger instruments.
- Cutting efficiency is 2-5 times > square blank
- The cutting edges are known as “Rakes” of the blade
- Triangular design is brittle and the cutting efficiency is less
the more acute this rake, the sharper the blade
7
There are approximately twice the number of spirals on a file as
on a reamer of corresponding size.
(K-type) Reamers
Are used for drilling.
They cut by being tightly inserted into the canal, twisted
clockwise one ¼ to ½ turn to engage the blades into the dentin
and then withdrawn.
Penetration rotation Retraction and the cut is made during
retraction.
Reaming is the only method that produces a round, tapered,
preparation possible only in straight canals Reamers, in such
cases they are rotated ½ turn.
In slightly curved canals reamers should be rotated only ¼
turn as more stress will cause breakage.
Files as well as reamers can be used for reaming but conversely,
reamers do not work well as files – their flutes are too widespread
to rasp.
Files
8
Achieves its principal cutting action on “withdrawl”.
But it cuts on push motion as well.
The withdrawal cutting action can be effected in both filing and
reaming motion.
Filing action (Rasping)
Instrument is placed in the canal at the desired length, pressure is
exerted against the canal wall and while this pressure is maintained, the
instruments is withdrawn, without turning.
Reaming action (Drilling)
: same as for reamers.
Penetration rotation retraction
Files tend to set in the dentin more readily than reamer must be
treated more carefully.
Withdrawing will cut away this engaged dentin.
Efficacy of K-type Instrument
Tri-angular Reamers Square Reamers
Cut with greater cutting efficiency.
Lose their sharpness more rapidly.
# easily.
9
Wear does not appear to be factor in instrument function but
rather instruments fail because of deformation or fracture of the
blades.
Sotokawa studied discarded instruments and indicated metal
fatigue as the culprit in breakage and distortion. First, a starting point
crack develops on the file’s edge and then “metal fatigue fans out from
that point, spreading towards the file’s axial centre”.
Classification of instrument damage
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.
In order to overcome these problem, Ni-Ti has been substituted
for stainless steel – NITINOL
K-STYLE MODIFICATIONS
- After having dominated the market for 65 years, K-style
endodontic instruments came into a series of modifications
beginning in the 1980’s.
10
A] K-flex file
In 1982 Kerr manufacturing co introduced a new instrument
termed K-flex file.
Cross section is rhombus / diamond shaped.
It is viewed as the fore-runner of the so-called
hybrid instrument designs
those designs that attempt to integrate the strength and versatility
of K-type files with the aggressive cutting properties of H-type
instruments.
When twisted to produce spiral/flutes, it results in alternating
high flutes and low flutes.
The cutting edges of the high flutes are formed by the 2 acute <s
of the rhombus.
Increase the sharpness and cutting efficiency.
The alternating low flutes are formed by the obtuse <les of the
rhombus.
these provide more area for debris removal
The decreased contact by the instrument with the canal walls
provides a space reservoir, which with proper irrigation further
reduces the danger of compacting dentinal filing in the canal.
11
Another advantage increased flexibility.
FLEX-R-FILE
Developed by the union Broach company is one of the variations
in the design of the top.
ADA specifications No.28 and No.58 state that the design of the
tip of K-file is optional.
This instrument was designed to be used in the top balanced force
technique.
The tip <le is reduced, so the file stays untired within the original
canal and cuts all sides more evenly.
The fluted edges are milled rather than twisted. This allows better
control of instrument flexibility and cutting efficiency and
influences torsional strength.
Anti-clockwise rotary motion is used.
An important feature of this instrument is its modified safe-
ended/ non-cutting.
12
Weine, suggested trimming 1mm from the tip of the file and
rounding off sharp edges on a diamond nail file. In this way, files
sizes 10, 15, 20, 25 may be converted to 12, 17, 22 and 27.
The disadvantages of this technique are that the files are made
disposable and the edges may be difficult to smooth, which
therefore creates ledges during filing. A recent innovation by
Maillefer overcomes these problems using the intermediate files
“Golden Mediums”.
Zipper Flexicut
Produced by twisting a triangular shank made from SCS
spacecraft steel.
It is a high vacuum-fired chrome nickel steel.
Advantages:
- Flexibility.
- Non-aggressive tip.
Other companies have introduced such instruments as control
safe files, the anti-ledging tip <, safety H-file.
13
Flexo-File
This is a flexible instrument twisted from a stainless steel blank
of angular cross-section.
With 1.81 flutes/mm length.
Tip is modified to be non-cutting.
A recent addition “Golden Medium” is of parallel design but
provides a range of intermediate sizes (12, 17, 22, 27, and 32).
Zipper Flexicut
HEDSTROEM (H) – FILES
Machined from a blank of circular cross-section.
The flutes are produced by machining a single helix into the
metal, producing a series of intersecting curves which increase in
size from the tip to the handle.
The strength and flexibility of the instrument is determined by the
depth of the flute or the residual bulk of metal in the central
portion of the file.
The blades thus formed are virtually at rt. <s to the dentin surface
(+ve rake <).
14
Helical < of K and H type
Greater cutting efficiency is achieved in filing motion as the
helical < approaches 90° to the dentin surface.
Advantages:
H-files cut in one direction retraction.
The most efficient cutting motion is a pulling motion.
It was found to be 3 times more effective on than K-files, also did
not tend to pack debris at the apex.
Disadvantages:
They are fragile, hence are not used in torquing action.
ADA specification No. 58 was applied to H-files. It stated:
Included requirements for sterilization of handles.
Adds requirements that physical properties of the files remain
unchanged after cycling through a stenm autoclave and dry heat
sterilization sequence.
Modifications of the H-files
Mc Spadden was the first to modify the traditional H-file. E.g.,
Burns unifile, Dynatrak.
15
These files were designed with 2 spirals for cutting
blades – a double helix design.
In cross section, the blades present as ‘S’ shape
rather than the single helix tear-drop cross-sectional shape of the
H-file.
Mc Spadden claimed that unifile cuts more
efficiently than the standard H-file but it generally failed the
torque twisting test.
Authors found that it should not be twisted more
than ¼ turn.
Dynatrak file also developed by McSpadden was the first
instrument designed for use in the reciprocating handpieces
(Crinomatic). This variation of the unifile had a non-cutting pilot tip and
an altered helical pitch angle to prevent the instrument from binding,
when in use.
“S” File
Is a variation of the unifile in its double helix configuration as
well as variations in flute depth.
16
It differs from the unifile since the angle of the flutes remains
uniform through the length of the instrument and the depth of the
flutes increases from tip to handle.
Cutting by reaming is also possible due to its flute design.
Buchanan has further modified the H-type file as the safety Hedstroem
has a non-cutting side to prevent ledging in curved canals.
NT-SENSOR FILES
Another variation by Mac Spadden.
These instruments have 3 flutes, the third flute set as half the < of
the other two S-shaped flutes.
MAC FILE
Newest version.
Produced in nickel-titanium, which gives the instrument
superelasticity.
A-FILE
Modified by levy to function better with the automated canal
finder system.
17
Also available as a hand file.
Unique features of A-File
Steep depth of the flutes.
40° helical angle of the cutting blades (these cut more efficiently than
standard 60°/70° helical <).
Advantages:
Can be used in a curved canal (the steep blades on the inner wall
collapse and lose their cutting ability. It is more aggressive on the
external wall. Non-cutting tip follows lumen without ledging.
On withdrawl, H-file represents +ve cutting action on internal
wall (arrow) where stripping perforation frequently occurs, and
sharpened tip tends to ledge into external wall.
“U-file”
Developed by Heath.
Marketed as the canal Master ‘u’ files.
Triangular cross-section with two 90° cutting edges at each point
of the triangular blade.
Adapts well to the curved canal.
18
Non-cutting pilot tip ensures that the file remains in the lumen of
the canal, thus avoiding ‘zipping’ and transportation at the apex.
These files are used in both a push-pull and rotary motion.
19
APICAL PREPARATION TYPE HAND INSTRUMENTS
I] Canal Master Instruments Hand
Engine driven
- Developed by Wildey and Senia.
- 3 major feature a 1.0mm non-cutting pilot tip.
a small size-cutting head (3mm; since reduced to 1-2mm)
a non-cutting shaft with increased flexibility.
To overcome problems (rapid wear and breakage) with the canal
master, a new design of the cutting blades ensued canal master
‘u’.
Here the blades are the ‘u’ design developed by Heath.
Hand instruments come in sizes (20-80) with a number of half
sizes in between
22.5
32.5
42.5 etc
Engine driven instruments are in 150 sizes 50 – 100.
Originally it was recommended that these instruments be used in
a reaming action i.e. 90° turn to the right and 90° turn to the
left.
20
However, with the new u design, continuous rapid clockwise, yet
gentle “drilling action” is recommended.
Advantages:
It reduces the incidence of transportation within the canal.
Disadvantages:
Instrument breakage.
to overcome this problem, the canal master ‘u’ is made from
Nickel-Titanium – Ni-Ti canal Master ‘u’ (CMU).
Advantages:
- Less tendency for transportation, ledging and zipping.
- Less breakage.
- Less debris being forced through the apical foramen.
FLEXOGATES (Gates – Glidden Modification) (a.k.a. Handygates)
- Is a hand instrument also designed for apical preparation.
- Is a safe-tipped variation of the traditional G.G. Drill.
- It consists of a smooth, flexible shank which is circular and small
in cross section.
- The non-cutting tip is followed by approximately one
spiral/fluting on an extended head carried on a shank.
21
- As in G.G.D., the flexogates is made deliberately weak at the
handle end of the thin shank to ensure access for removal of
broken instruments.
BRISENO has compared flexogates and canal master in vitro and
found flexogates less likely to cause apical transportation.
HELIAPICAL
This instrument resembles a conventional file in the apical 4-
5mm, the remainder being a narrow blank shank. Care is needed
in its use; small sizes may # if a continuous rotational motion is
used.
‘BROACHES’
Are of 2 type Barbed
Smooth
Rasps are also included in this category.
ADA specification No. 63 seperates broaches and rasps.
The major difference between broaches and rasps lies in the depth
and < of cut in the wire shaft (core) which results in barbs of different
height and shapes.
22
Mc Spadden Engine File
Designed to be used in a rotary instrument slow speeds (300rpm).
Constructed from a superelastic Ni-Ti alloy. These instruments
are designed to avoid binding into canal walls by a) 15-35
sizes – flat areas are substituted for blades and cutting is achieved
by a planning action.; b) in sizes 40-60, the same is achieved
using 2 or more spiraled blades.
The most unique feature of this instrument is that it “pulls” the
canal systems contents out rather than forcing them apically.
Rasp Barbed Broaches
Barbs are equal to 1/3rd the diameter of the tip.
Taper is 0.015 mm/mm
Similar in design to barbed broaches, but having shallower and more rounded barbs produce more rough walled canal preparation.
Barb height should be ½ the core diameter.
Taper of broaches is 0.007mm/mm (less than half that of rasps).
Uses:
a. Are used primarily for the removal of intact pulp tissue.
b. To loosen the debris in the necrotic canals.
c. To remove paper points or cotton pellets from within the canal.
Available in different sizes
XXXF to XC
Break very easily.
23
Smooth Broaches
There is a smooth broach, which is sometimes used as a
Pathfinder.
Pathfinder CS, made of carbon steel, is less likely to collapse
when forced down a fine canal.
Manufactured (developed) by Kerr.
Is similar in appearance to the K-type file but possesses a
narrower taper to uniformly distribute the axial stress along the
instrument shaft, thus reducing the tendency to bend at the tip.
These instruments come in pre-sterilized single-unit packages and
are available in 19-21 and 25mm lengths and 2 sizes K1
K2
The carbon steel shaft is reported to provide greater sharpness
and strength for penetrating calcified root canals.
AUTOMATED ROOT CANAL PREPARATION DEVICES
If used in collaberation with hand instruments, most of the
devices can serve as useful adjuvants in root canal preparation.
‘Danger zones’, apical part of root canals, and narrow, curved
canals are the area suggested to be treated by hand instruments as it
24
generally is difficult to control the preparation of these areas using
engine driven root canal instruments.
Advantages:
- Easy to use.
- Saves time.
- Renders ideal preparation of root canal.
Reduction in fatigue
The overall strain becomes less and fatigue is decreased.
Moreover, procedural time may also be less compared to hand
instrumentation.
Reduction in treatment time
But several factors are involved like:
- Not all the devices reduce the treatment time.
- It depends on the type of tooth being treated.
- Expertise of the clinician.
Limitations:
They do not simplify the entire root-canal treatment procedure as
they have no role in the early phase of the treatment. Correct diagnosis,
proper access cavity, locating the orifices, debriding the canals and
determining the root canal length, have to be done manually using one’s
intelligence, knowledge and clinical experience. Moreover, most of
25
these devices can be used in the root canals only after the completion of
preparation of canals using 150 size No. 15.
Lack of tactile sensation
This is an advantage with hand instruments such registration with
instruments (apical stop) alerts the clinician to be cautious and greatly
aids in avoiding procedural mishaps. Continuous use of automated
handpiece against resistance may lead on to either # of the RC
instrument or cause mishaps. Newer models such as canal finder system
are designed to stop functioning on countering resistance in the root
canal. The problem of lack of tactile sensation can be overcome to a
great extent three proper and sequential use of automated root canal
instruments and expertise.
Classification.A. Reciprocal (impact specially designed short reciprocal
most to the cutting instrument).
B. Rotary.
C. Ultrasonic.
D. Sonic.
A. Handpieces that work on the principle of offering ‘alternating’
movement to RC instruments are termed ‘reciprocal handpieces’.
26
First engine driven rotary reciprocal RC shaping instrument was
introduced in 1899 by Rellins.
AUTOMATED ROOT CANAL INSTRUMENTS
ISO Groups II and III (According to Ingle):
Engine driven instruments can be used in 3 types of contra-
<handpieces:
Fully rotary (latch / friction grip).
Reciprocal quarter-turn.
Special handpiece that imparts a vertical stroke but with an added
reciprocating quarter turn that “cuts-in” when the instrument is stressed.
According to Stock
They can be classified according to the type of movement imparted
to the cutting instrument.
- Rotary
- Reciprocal.
- Vertical.
- Random.
I] ROTARY
Instrumentation with a full rotary handpiece is by straight line
drilling or side-cutting.
Uses:
27
- These are used primarily to develop coronal access to canal
orifices.
- They are used in perfectly straight canals (since they do not
bend).
- To prepare post channels for final restoration.
- To widen as much as two-thirds of the canal.
To overcome this problem (they do not bend), they should be
used in slower handpieces.
e.g, - Medidenta reduction Gear handpiece.
- Sensomatic handpiece.
Where the torque is controlled and speed is reduced to as much as
10RPM.
“NITIMAC” is a new gear reduction handpiece (NT Company,
USA).
- runs at 300 rpm
- 2 different types of Ni-Ti files have been designed by Mac
Spadden.
28
Sensor files Nitixl files
- Redesigned hedstroem type
instruments
Advantages:
- Flexibility.
- Resistance to #
- Made from Nickel-titanium
(u-style configuration).
- Now called NT-power files
- Are the finishing files
of these files allow preparation
of severely curved root canals
These files are manufactured with an off-centre tip that facilitated
negotiating around curvatures and ledges.
The two most popular engine-driven instruments are:
- Gates Glidden drills
- Peeso reamers (drills)
GGD – has a long, thin shaft ending in a flame-shaped head with a safe-
tip to guard against perforation.
Uses:
- For initial opening of the canal-orifices.
- Deeper penetration in both straight and curved canals.
- To remove the lingual shoulder in anterior teeth. The flame head
cuts laterally and is used with gentle, apically directed pressure.
Both are made of hardened carbon steel and corrode easily. Both
are inflexible.
29
- This instrument was designed to have a weak spot in the part of
the shaft closest to the handpieces, so that, if the instrument
separates, the separated part can be easily removed from the
canal.
- Working head is small.
- They comes in sizes / through 6
- These sizes have been now converted to the 150 instrument sizes
and colours.
Both are flame shaped
Has long sharp flutes
- Sharper cutting edges.
- More efficient.
Peeso Reamer
- Is most often used in preparing the coronal part of the root canal
for a post and core.
- It cuts laterally – sizes and dimensions of GGD and Peeso
Reamers
30
Peeso Reamer GGD
No. (diameter mm)
1
2
3
4
5
6
0.7
0.9
1.10
1.30
1.50
1.70
0.5
0.7
0.9
1.10
1.30
1.50
Orifice Opener
- Martin has developed an “Orifice Opener” used to flare and
prepare the cervical and middle portions of the canal.
- Used in a slow speed latch-type handpiece.
- Come in sizes 25-70.
- This ‘M’ series orifice opener is more flexible than GGD.
- But still recommended only for straight parts of the canal.
Canal Master System (introduced by Wildey and Senia)
- Are a k-style modification.
- Cutting head is shortened to only 3-4mm above the non-cutting
pilot tip.
- They are now made in Nickel-titanium (CM ‘U’).
- The recent advancement in this is the light speed system.
31
II] RECIPROCAL
This uses a special handpiece which contra-rotates the instrument,
through 90° 3000 times / minute (quarter-turn motion).
- These were first introduced in 1899 by Rellins.
- They may be classified depending on the direction of movement that
they impart.
Rotatory Vertical (push-pull)
- Giromatic
- Kerr M4
- Endo-Cursor
- Canal Finder system
- Intra-Endo 3- LDSY
- Endo Lift
Giromatic
Introduced in 1964
A variety of canal instruments can be used with the
Giromatic.
- Giro pointer – orifice opener (16mm).
- Giro broach.
- Giro-file – a hedstroem configuration
- Giro reamer
- Heli-Girofile (3 cutting blades in cross-section).
32
According to Weine
- Giromatic produced wider apical derivations (“Zip”) in canals
with sharp apical curvature.
Later instruments like “Triocut” were designed for Giromatic.
Kerr M4
- It is so named because it utilizes 4:1 gear reduction handpiece.
- It imparts a reciprocal “watch-winding” 30° motion to the
endodontic instrument.
- It is devoid of any vertical movement.
- Safety Hedstroem files are used with this type of instrument.
Disadvantages:
- Causes frequent breakage of instrument in the canals.
- Creates hour-glass preparations, ledges, zips.
- Creates strip perforations.
Canal Finder System
- Developed in France
- Is a specialized handpiece with a vertical movement of 0.3 to
1.0mm + a free rotational movement (1/4 turn).
33
(If there is no resistance in the canal, the instrument moves
upto 1mm; in case of minimal resistance, it move 0-3mm. In
several resistance in stops).
Increasing the vertical pressure will stop the vertical movement.
- The free-rotational movement allows the tip of the instrument to
move away from an obstruction in the root canal wall.
- Master, Hedstroem A-file /K-files either made of stainless steel /
nickel titanium can be used.
- The cutting instruments are specially designed. The files have
increased cutting efficiency as it has 40° helical angle, and the
flute depth is also more pronounced for better debridement.
- The files tip are rounded and negative cutting angle is given for
the first flute. This avoids procedural errors.
- The clinical Research Associates described it as “simple, easy,
predictable, automated instrument that compares favourably to or
exceeds, hand instrumentation and especially well suited for
narrow or highly curved canals.
Disadvantages:
- Causes zipping / transportation.
34
Uses:
- It can also be used in retreatment of root canals containing gutta-
percha.
Canal header
Is a modified speed reducing handpiece.
Has a vertical movement and of 4 – 8mm and a contra-rotational
movement which is restricted to 30°. Three cutting instruments are
available.
- K-file with a safe-ended tip for narrow canals.
- A more aggressive H-file.
- A universal file which is a flexible H-file with a safe-ended tip.
Intra-Endo 3-LDSY is a racer-type handpiece.
is a “look-alike” of the canal finder system.
apart from up and down movement, it can impart also full turn
movement; the latter occurring when axial pressure is applied.
the vertical movement is in the range of 0.4mm.
it canal also make use of conventional reamers and H-files.
Another type of “look-alike” of the canal finder system is the
Endo-lift (Kerr).
35
EXCALIBUR
produces a random lateral vibratory motion.
it vibrates only laterally and is devoid of any vertical movement.
the amplitude of movement is 1.5-2mm.
K-files are used at 20,000-25,000 rpm.
this devices may be classified as a subsonic instrument (oscillates at
1000-2000 frequency per sec.).
Disadvantages:
due to its effective cutting ability, it may remove dentin excessively.
tends to straighten the canals or causes strip perforation.
III] ULTRASONICS – is based on a system in which sound as energy
source activates a file. This results in a 3-D activation of the file. The
main debriding action was though be by”cavitation”.
- It denotes a device which imparts sinusoidal vibration of high
intensity to root canal instrumentation, in the range which is
above that of audible perception.
- Originally introduced to endodontics by Richman in 1957, it was
further developed and promoted through extensive research by
Howard Martin and Walter Cunningham in 1976).
36
Interestingly, ultrasonics was originally intended by them to be
used as a root canal sterilizing device.
- There are 2 methods of generating ultrasonic oscillations in the
file shank.
Magnetostrictive Peizo-electric
- Requires water-cooling i.e.
if NaOCl is used as an
irrigant, the water must be
led away from the stack via
additional tubing. This
makes the headpiece both
clumsy and expensive.
e.g. Cavi Endo (25,000 k hertz)
by Martin and Cunningham
followed by ENAC unit.
- More powerful.
- Does not require water-
cooling.
Disadvantages:
- apical widening.
- Ledges in curved canals.
e.g. ENAC, Neosonic, MiniEndo
(30-35,000 K hertz).
2 types of files- Both these handpieces use K-file.
- Diamond-impregnated file for the straight part of the canal.
- Can produce a tapered canal shape as the tip is constrained by
pressing against the canal wall.
37
Advantages:
- Cleaning of the root canal due to acoustic streaming (turoulence
along the shank of the file when immersed in a fluid).
- Causes less extrusion of root canal debris into the periapex.
- 10-15 No. files should be used as there are most flexible and less
likely to cause ledges.
Uses:
a) as a root canal shaping device.
b) As a debriding device.
- Acoustic streaming caused by high vibration of the file is the
main mechanism. The main action of ultrasonics was initially
thought to be by cavitation, a process by which bubbles formed
from the action of the file, become unstable, collapse, and cause a
vacuum like ‘implosion’.
- The instrument including the tip should be freely movable in the
canal to maintain optimum efficacy.
c) for the removal of posts, fractured instruments.
d) Coating the canal walls with sealer before filling.
38
SONICS
The principal sonic endodontic handpiece available today is the
o Micro Mega 1500 (MM 1500)
o Sonic Air Endo System
- These use compressed air at a pressure of 0.4MPa.
- Impart vibrations in the frequency of between 1500 and 3000Hz.
- A vibrational wave form is imparted to the file shank.
3 choices of files that can be used with sonic handpieces.
- Rispi Sonic.
- Shaper Sonic.
- Trio sonic.
Rispi Shaper Trio
- Developed by
Dr. Retano Spina
in Italy.
- Resemble rat-tail
file.
- Used in the
coronal 2/3rd of
the root canal.
- Has 8 cutting
blades.
- By Dr. L.M.
Lawrichesse in
France.
- Used in the
apical 1/3rd.
- Resembles a
husky barbed
broach.
- 16 cutting
blades.
- Also known as
Heliosonic or
Triosonic files.
- Resembles a
reamer.
- Useful for
coating the canal
wall with sealers
and placing
Ca(OH)2 pastes.
39
Disadvantages:
- Produces
undulating /
rippled canal
walls.
- Most effective in
widening the
canal (than
Rispisonic)
- Resembles a
triple-helix
Hedstroem file.
- Least effective
All these instruments have a safe-ended non-cutting tip of 1.5-2.0mm
in length.
the 150 sizes range from 15-40.
Micro-mega retropreparation tips are designed for periapical
surgeries. These are available in 3 standardized lengths (#35, #45, #55)
and in 2 lengths (2mm, 3mm) but these can only be used where there is
an existing hole in the tooth in which to insert.
when lateral movement is stopped in the canal, a vertical movement
of approx. 100µm is evident. The movement of the file shank creates a
form of acoustic microstreaming with 2 areas of turbulence.
One around the mid shank other at the tip
LASERS
The use of laser is still to be approved by the U.S. food and Drug
Administration. Nonetheless, the method appears promising.
Wachman was the first to suggest lasers.
40
Levy made use of Nd-YAG laser mounted with a fibre-optic to
clean and shape the canal (Neodynium, Yttrium aluminium garnet laser)
Wavelength of 1.06µm.
The laser beam is carried through a silica fibre accompanied by a
cooling system that delivers a spray of air and water.
Levy compared the laser technique with the conventional stop back
procedure. Using SEM evaluation he concluded that preparation with a laser
beam is possible, with an improvement in the cleanliness of the canal walls
when compared to conventional techniques.
Ultrasonics Sonics
Permit the use of either an inert
sterile or chemically active irrigant
selected by the clinician.
Oscillation is transverse.
Both use circumferential filing
method.
Irrigation is limited to filtered
H2O as delivered through the
dental unit cooling system.
It largely elliptical.
are affordably priced.
It does require setting up or
special connections as it involves
only a handpiece.
Chances of transportation of the
canals is less.
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INSTRUMENTS FOR SEALING THE ROOT CANAL
A. Hand and Finger Held instruments
i) Several varieties of specialized endodontic pliers and
forceps are available for placement of silver point and G.P. cones.
The pliers generally have a tapered groove along the beak for
firmly grasping the ridged silver cone, whereas the forceps may have
either grooved or serrated beaks for holding G.P. cones.
Endodontic forceps differ from common college or cotton
forceps in that they have a latch mechanism for locking the instrument
in the closed position. This mechanism allows easier transfer of
instrument and material from assistant to operator during treatment.
ii) Endodontic condense (pluggers) and Spreaders
Are smooth tapered metal instruments used to compress and compact
the G.P. material either laterally or vertically within the prepared root canal
space according to either the lateral or vertical condensation of G.P. filling
technique.
Spreaders Pluggers
Have more tapered and pointed
tips for lateral packing of the
material
Have slunt or flat-ended tips for
compression
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According to 150/ADA in 1990, these instruments are modeled as:
No.: 15-45 for spreaders.
No. 15-40 for pluggers.
This new attempt to bring order out of chaos would abondan the
old confusing numbering systems (1-10, D-11, D-11T, ABCD, XF, FF,
F, M, FM etc.).
- Long handled spreaders / pluggers are formed of chrome-plated
or stainless steel with the operative head at various angles to the
shaft.
- M-series plugger, spreaders are double-ended long-handled
instruments that correspond to the standard sizing and taper of K-
type files and reamers.
- The handles are color-coded.
- A specification for spreaders and plugger is currently developed
by the ANSI standard.
5 digit no.
The first 2 digits represent the diameter of the
instrument at the tip.
Remaining 3 digits designate the taper in
hundredths of mm.
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RECENT ADVANCES IN ENDODONTIC INSTRUMENTS
Titanium-Based instruments
Recently new alloys characterized by lower elastic modulus have
developed for root canal instruments in order to overcome undesirable
shaping effects especially in narrow-curved or severely curved canals.
Some of these instruments use titanium and a distinction has to be made
between Ni-Ti alloys and Ti-Al alloys.
Ti-Al
Most recently microtitane marketed by Micro-Mega have been
introduced (to improve the cutting efficiency of Ni-Ti).
These are titanium-based instruments and consist of about:
90% Ti.
5% Al by wt.
They are available as reamers, K-files and H-files for manual use.
- The fracture resistance of Ti-Al is same as flex S.S..
- Increased flexibility.
- Unlike Ni-Ti – no superelastic property.
- Cutting efficiency is less than flex S.S. as they cut more on the
outer surface of the canals in curved canals.
44
Ni-Ti
History
In the early 1960’s, a Ni-Ti alloy was developed by W.F.
Buchler, a metallurgist investigating non-magnetic, salt-resisting, water
proof alloys for the space programme at Naval Ordinance Lab, USA.
The term ‘NITINOL’, an acronym suggests the elements from
which the material is composed.
Ni-NICKEL
Ti-TITANIUM
Nol –NAVAL ORDINANCE LABORATORY
In dentistry, Andersen and Hilleman (1971) were first to
introduce it in the field of orthodontics.
Walia et al in 1988 inspired its introduction in endodontics.
Advantages over S.S.
- Nitinol files have 2-3 times more elastic flexibility.
- Superior # resistance in clockwise and counter clockwise torsion
owing to the ductility.
- Ni-Ti files can retain the shape of the curved canal and do not
straighten like stainless steel.
45
- Ni-Ti undergoes large amounts of elastic deformation when
compared to S.S.
Disadvantages over S.S.
- Cutting efficiency of Nitinol is only 60% than that of matching
S.S. file.
- Does not give any indication of #.
Properties of Ni-Ti
The alloys contain:
54% - Ni.
44% - Ti
2% or less cobalt.
These alloys undergo superelastic deformation and undergo a
stress inducted Martenisitic phase (close packed hexagonal phase-
weaker phase) transformation from a parent structure that is Austenite
(body-centred cubic lattice) – stronger and stable phase.
On release of stress, the structure reverts back to Austenite.
Austenite – Martensitic --> Austenite.
46
Features of Ni-Ti
a) Shape memory
- The ability of the material to revert back to its original shape.
- The transition temperature is lowered by adding Co and
increasing the content of Ni.
- The application of shape memory in endodontology is to remove
any deformations within the Ni-Ti instruments by heating them
above 125°C.
b) Super/Pseudo elasticity
- When stresses are induced on Ni-Ti, there is a stress-induced
formation of martensitic phase. This reverts immediately to
austenitic as soon as the stresses are removed. This process elicits
a springy (rubber-like) elastic property to the material -->
Pseudoelasticity.
- Ni-Ti files are machined rather than twisted.
It is known that grinding of Ni-based alloys difficult. This leads
to structural defects especially at the cutting edges of Ni-Ti. Some
authors have found that the cutting edges of Ni-Ti show irregularities,
structural defects or metal flast due to the manufacturing grinding
47
process. This was thought to be responsible for their relatively low
cutting efficiency.
Recently Maillefer Co. introduced the Nitiflex-K-file.
- Union Broach.
- Onyx-R-file.
These 2 instruments have proved to be superior to other Ni-Ti
instruments.
Topic of controversy
- Schafer has demonstrated that one cycle of steam sterilization or
autoclave is enough to produce a significant decrease in the
cutting efficiency of Ni-Ti K-files.
- On the other hand, neither 10 cycles of autoclaving nor steam
sterilization causes a reduction in the cutting efficiency of S.S.
instruments.
Ideal Requirements and Features of Ni-Ti Instruments
a) Cutting angle
- If slightly +ve, results in an effective cutting action.
- If too much +ve, the blade becomes engaged into the surface
excessively and binds without forming chips.
- A –ve angle will scrape the dentin rather than cutting it.
48
b) Flute design
- A progressively larger flute space, distance to the blade is
preferred so as to avoid any compaction of debris and also
provides an effective channel for its removal.
c) Radial land
- Gives more mass to the cutting edge thus preventing crack
formation and helps in deflecting the instrument around the
curvature.
d) Frictional Resistance
- A small marginal land area is required and the remaining radial
land is recessed thus decreasing the peripheral surface.
- A wide land can result in frictional resistance.
e) Notch
- If the notch is too close to the cutting edge, stresses will tend to
concentrate on the notch e.g. is H-file that will lead to crack
formation to ideally it should be away from the cutting edge.
f) Working surface/taper (Santa Claus principle)
- We decrease the surface of the instrument coming to contact with
the canal by giving greater taper and as a result, all the forces get
concentrated in a smaller area leading to better cutting.
49
g) Non-cutting tip (Pilot tip)
- In cases of canals of severe curvature.
Ni-Ti Rotary Instruments
- Profile series 29 followed by profile with ISO series.
- Quantec 2000 followed by Quantec LX, SC tips and Q Flare
series.
- HERO 642.
- Light speed.
Profile Family
I] 29 series
a) Hand instruments – 0.02 taper.
b) Rotary instruments – 0.04, 0.06 taper
II] ISO series
a) 0.04 and 0.06 ISO rotary instruments (also available as hand
instruments).
III] Profile Orifice shaper 0.05-0.08 taper
IV] Profile GT rotary instruments (also available as hand files)
I a) Profile 29 series with 0.02 taper- Introduced by Stephen Buchanan.
- Available in both S.S. and Ni-Ti instruments.
50
- Resemble the original engine driven Ni-Ti, ‘U’ files.
- Have a constitution 29% increase in tip diameter.
- All of them have a narrow 0.2% taper.
Advantages:
1) 8 files replace the 11 files of the traditional ISO sizes 10-
60.
2) These instruments are spread with more instruments at
smaller sizes and less instruments at the larger sizes.
3) Transition between sizes is enhanced due to greater and
gradual increase in diameter.
4) Come in total of 13 instruments instead of ISO 21
instruments.
b) Profile series 29 with 0.04 and 0.06 Rotary Type:
- These instruments were manufactured in order to have an added
advantage of greater taper.
- Have an increase of 29% in the tip diameter to make
instrumentation easier.
- Prevent procedural errors.
(The standard ISO are manufacture with a constituent
0.05/0.1mm of the width at the tip between each instrument e.g. the
51
difference in the area of cross-section of ISO size 10 and 15 is 50%
whereas between 55 and 60-9% only. That is why instrumentation with
the change over of instruments between 15 and 20 or 20 and 25 is
generally difficult but is easier between 35-40 or instruments higher in
size).
Disadvantages:
- Fewer instruments as the size increases thus causing more
deformations.
c) Profile 0.04 and 0.06 of variable Taper Rotary Instruments
- Have radial land which has a ‘U’ shaped flute and helps in lifting
the debris coronally.
- Has a safety tip design with minimum transitional angle to
prevent ledging and transporting.
- Can be used more efficiently around curved canals allowing the
creation of a tapered preparation.
0.06 Taper- Taper is 6%
- Length 0.21 and 25mm
- No. available : 15 to 40.
52
Use:
- For preparing the middle portion of the canal.
- Carries 2 coloured rings on the shank (identification).
McXIM Series (Mity files) (IEJ, 2000)
- are a series of Ni-Ti rotary instruments available in 5 different
tapers and 4 designs.
Tapers --> 0.3, 0.4, 0.045, 0.05 and 0.055 all with identical tip size 25.
- have flattened radial land and non-cutting tips.
- 4 different blade designs.
a) u-type.
b) Hedstroem with progressive radial lands.
c) 0.02 tapers with equal radial lands throughout their lengths.
d) With dissimilar helical angles to permit widening at the apex and
preferential side cutting.
0.04 Taper
- Taper is i) 4%
- Length ii) 21, 25 and 31mm
- No.’s available – 15-90 (15, 20, 25, 30, 35, 40, 45, 60, 90).
53
- Also available as hand instruments.
- Carries a single coloured ring on the shank.
Use:
- For preparing the terminal part of the canal.
Advantages: This instrument is much wider at D3 (end of the cutting
part of the instrument towards the handle). Therefore gives the necessary
coronal flare to the root canal automatically.
- the tip is bullet-nosed.
- Used in a 6:1 gear-reduction hand-piece at an rpm of 150-350.
- Prepares the root canal with a 3-D effect.
d) Profile O.S.
Use:
- are used for preparing the coronal section of the canal and also
for removing G.P. and sealer before inserting the post.
- RCT of milk teeth.
Identification: 3 coloured rings on the shank.- These instruments replaced the G.G.D. They shown to be more
effective in preparing the coronal portion when compared with
GGD, as the non-cutting tip of the instrument opens the coronal
area with more control than GGD.
54
- They operate at very slow speed of 350 rpm thus assuring safe
handling.
- The u-file radial landed flute design keeps the instrument centred.
e) New profile greater taper rotary instrument (GT)
New generation of endodontic instruments.
- Lets negotiation even in the most severely curved canals with less
risk of apical transporting, ledging or perforating.
- Variable pitched flutes provide reamer like efficiency.
f) GT Range
- All have gold plated shanks.
- Have flat outer edges with a patented 16-section designed to
prevent screwing of the instrument in the canal.
- 3 types identifiable by coloured rings on the shanks.
- Are said to impart predetermined shapes to the root canal
preparation.
55
GT Rotary GT Rotary 0.04 File GT Accessory files
- Taper is 6-12%
- Length: 21 and
25mm
- 4 in no. all have
ISO size at the
tip i.e.
D1=0.2mm
- The sleepest
taper is used first
for crown down
technique.
- 0.06 --> narrow
curved canals.
- 0.08 in most
smaller roots
like mesial roots
of mandibular
molars.
- Taper is 4%
- 21, 25 and 31
mm
- No.’s 20-35
sizes.
- Used for
preparation of
the terminal part
of the root canal.
- Identified by one
ring on the
shank.
- Taper is 12%.
- 21 & 25mm
- diameter 35, 50
and 70mm
- used in the final
phases of
preparation to
obtain a more
tapered coronal
portion.
- Used in large
canals.
56
II] Quantec 2000 Series
- Introduced by McSpadden.
- The original Quantec 2000 series had a 90°-tip. This sharp tip
appears to predispose to problems like zips, elbows and
perforations. So, they were replaced.
QLX Non-cutting.
QSE safe-cutting tip with (60°).
Quantec Endodontic File
Flute Design
- Have a +ve cutting blade angle, as a result the dentin is cut rather
than scraped.
- Ideal helical angle.
- Channels debris out of the canal quickly and efficiently.
- Peripheral structure was increased along with its cone structure.
- Radial lands adds support and also prevents stress cracks in the
flutes cutting edges.
- Available in graduating tapers from 0.02-0.06.
- Tip Design SC-safe cutting.
LX-non-cutting
57
SC
- Cuts as it moves apically.
Ideal for:- Small tight canals.
- Narrow curvatures in tight spaces.
- Calcified canals.
- Constricted / obliterated canals.
LX- Non-cutting tip, which maintains a central-axis.
- Deflects around severe curvatures.
Ideal for:- Severe curvatures.
- Enlargement of mid-root and coronal aspect.
- Delicate apical regions.
Advances in Micromotor
a) Quantec ETM (Electric Torque Control Motor)
- Helps to provide a smooth feel and tactile response, i.e. essential
for success.
58
b) Quantec E (Irrigation System)
- Helps to provide a constant irrigation flow directly over the
rotating file.
- Speed in 340 rpm.
III] HERO 642- Introduced by Daryl Green
- Is a micromega instrument which is made from Ni-Ti alloy.
- HERO 642 means.
H – High.
E – Elasticity.
Ro – Rotation.
642 – available in tapers of 0.06, 0.04 and 0.02.
- Used in a special contra angled handpieces at 300-600 rpm.
- Are modified Micromega Helifiles.
3 tapers6% - Sizes 20, 25, 30 - Used for the initial orifice opening.
Length 21 and 25mm Orifice opening
4% - Sizes 20, 25 and 30 - Used 2mm short of the W.L.
Length 21, 25 and 29mm the W.L.
2% - Sizes 20, 25, 30, 35, 40 & 45 - Used till the full W.L.
Length 21, 25 and 29mm
And additional 0.02 tapers in sizes 35 and 40.
59
These instruments have a Triple Helix Geometry
- 3 cutting edges for cutting in curette effect.
- No radial land so no packing of smear layer.
- An inactive tip.
- Progressive pitch.
Disadvantages:
- Lacks adequate taper of the canal.
IV] LIGHT SPEED
- Is an engine driven version of the Ni-Ti can Master ‘U’.
- Resembles the GGD and are used in low speed handpieces 1300-
2000 rpm (10:1 gear reduction).
- Flexible non-cutting shaft with length markings on the
instrument. The no.s indicate the length of the instrument from
the tip 21, 25 and 31 mm in length.
- Non-cutting pilot tip. This helps to keep the instrument within the
canal and avoid ledging.
- The instrument is also available in half-sizes, which is identified
by a double ring on the handle or a dot on the end of the handle.
- Available in sizes from 20-100 with intermediate sizes present in
between 20-60.
60
- Cutting tips vary in length from 0.25mm for size 20 to 1.75mm
for size 100 [ 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45,
47.5, 50, 52.5, 55, 57.5, 60, 65, 70, 80, 90, 100].
MAR
- Master apical rotary.
- Is the smallest light speed used for instrumentation in the apical
part of the canal.
Points to be kept in mind using Ni-Ti
- Always irrigate (as smear layer is accentuated with use of Ni-Ti).
(each Ni-Ti) - Used approx. for 700 rotations or 6-10 RCT’s.
- 5% NaOcl cause corrosion.
- Fracture resistance of Ni-Ti is unaffected by prolonged
exposure to NaOcl.
Disadvantages of Ni-Ti Rotary
Apical zip/tear drop transportations.
- Defined as an irregular widened area created by the master apical
file near the end point of the preparation.
Elbows
- Occurred with apical zip and formed a narrower region more
coronally.
61
Ledges
- Are irregular areas created by more removal of the dentin from
the outer aspect of the curved portion.
- Narrower region coronally.
Perforations
- Occurs as separate and distinct false canals not continuous with
the original canal.
Danger zones
- Is the area coronal to the elbow where excess dentin has been
removed from the inner aspect of the curve.
Transportation
External Internal
- Caused by failing to precurve instruments while using larger instruments.
- Apical foramen is torn and given an hour glass shape.
- 2nd type is worn and also gives an hour-glass shape.
- Usually begins as a ledge - Occurs when the portal of exit is moved internal to its external position by blocking position by blocking the canal with dentin mud. This results in a new false path.
62
Conclusion
- The evolution of endodontic instrumentation is an ongoing
process in which the benefits are continuously being refined.
- A successful clinician must have the tools of understanding
consistency and accuracy can also be attained three practices and
observation.
63