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

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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,

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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.

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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

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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

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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.

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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

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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

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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.

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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.

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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.

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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.

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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.

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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 <).

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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- 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.

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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.

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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

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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

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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’.

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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:

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- 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.

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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.

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- 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

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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.

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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).

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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).

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(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.

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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).

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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).

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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.

41

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

42

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.

43

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