endodontic instument

8/11/2019 endodontic instument

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LECTURE II

PRECLINICAL ENDODONTIC

Instruments used for endodontictreatment

A. Instruments used for coronal and \or access

opening:

It includes some instruments familiar in restorative dentistry andothers which have been specially adapted for endodontics.

The endodontic explorer is a double-ended, extra-long, sharp

designed to help in the location of canal orifices and probing for

fractures on the pulp chamber floor. A long spoon excavator is

required to scoop out pulp chamber contents and flick away pulpstones during access cavity preparation. irrors and locking

twee!ers are ideally suited to the handling of paper points, gutta-percha and root canal instruments. "lastic instruments and

amalgam pluggers are needed to place interappointments

restorations. An endodontic millimeter ruler should be available

to assess root canal length. Irrigating syringe is important todeposit endodontic irrigant in the pulp spaces.

#urs both friction grip are used in the initial stages of access

preparation to established correct outline form and round burs

for low speed handpiece $normal and extra-long length%, are usedto lift the roof of the pulp chamber and eliminate overhanging

dentine. &afe-ended diamond or tungsten-carbide bur, both with

a non-cutting tip, is used to taper and smooth the access opening.The non-cutting tip is used to prevent gouging on the floor of the

pulp chamber, where important landmarks could be lost in pinpointthe location of root canals. "ulp chamber act as a map road for

you toward the canals

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Rubber dam

B. Instruments used for radicular portion of rootcanals:

1. Barbed broaches' they are made from soft steel wire. The

barbs are formed by cutting into the metal and forcing the cutportion away from the shaft, so that the tip of the barb points

towards the handle. They are mainly used for the removal of the

pulp tissues from the root canals and removal of cotton- wooldressings.

(. Reamers' reamers were the original intracanal instruments,used for removal of the pulp contents and for widening andsmoothing the canal walls. They are usually made by twisting a

tapered three-sided triangular blank of stainless steel, with

cross-sectional less than k-file, which makes reamers moreflexible than )-files. #ecause each angle of the blank is

approximately *+ degrees, a sharp knifelike edge is available.

These instruments have between half to one flute per millimeters

of length. The basic action of reamers is reaming, which involvesplacement of the instrument toward the apex until some binding

is felt and then turning the handle more than a full revolution.

lockwise turning will remove materials from the canal by way ofthe flutes revolution, whereas counterclockwise turning will force

materials apically. The maor effectiveness of hard tissue

removal by reaming is the insertion of the instrument by shavingthe dentin walls.

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/. K-files:There are various types of root canal file0 thefollowings are the main types' )-file, )flex, 1lexofile,1lex-2, 3edstr4m and &afety 3edstr4m, and &-file. The

following is a brief description for each' K-file:This instrument is manufactured from stainless

steel, by twisting four-sided square blank. The instruments have

one and a half to tow and a half flutes per millimeter length. Thesquare blank had angles of 5+ degrees, which did not cut as well

as the *+ degrees angle of the reamer. 3owever, reamers a half

to one flute per millimeters of length and thus files had many

more cutting edges. The 1iles less flexible and less prone to

fracture than reamers.1iles are predominantly used with a filing or rasping action, in

which little or no rotation of the instrument in the root canal.1iling involves placement of the instrument toward the apex until

some binding is felt and then removing the instrument by scraping

against a side of the dentin wall with little or no revolution of thehandle. This dragging against the side of the wall is also referred

to as rasping action. The maor effectiveness of hard tissue

removal by filing is in the outstroke or withdrawal of theinstrument by dragging the flutes on the dentin walls.

K-flex file:The )-flex file has a tapered diamond shapedcross-section. This instrument has a series of cutting flutes withalternate sharp less than *+6 cutting edges and obtuse non-

cutting edges. The cutting efficiency of the )-flex file is greater

than many brands of )-file, due to increased flexibility and abilityto remove debris as its alternating blades provide a reservoir for

debris

Flexofile: This type manufactured in the same manner asthe )-file but it has a triangular cross-section and non-cutting tip

that gives sharper cutting blades and more room for debris than

the conventional )-file.

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1lex-2 file' This type of files has a non-cutting tip, althoughmost root canal instruments have a sharp tip. 2emoval of the

sharp cutting edges from the tip of instruments helps to preventundesirable ledge formation. The notion that the tip of the

instrument demonstrates potentially active cutting surfaces led

to the theory of balanced force and the eventual design of the

1lex-2 file.

Hedstrm and safety Hedstrm files' 3edstr4m $3-type% files are made by cutting the spiraling flutes into the shaft

of a piece of round, tapered stainless steel wire. 3edstr4m files

cut only in one direction, which is retraction. The efficiency ofvarious endodontic instruments has been tested and, they foundthe 3edstr4m instruments significantly more effective than

other files types. The safety 3edstr4m file feature which is the

non-cutting safety side along the length of the blade reduces thepotential for strip perforations. 3edstr4m files, has two serious

drawbacks. It is weakened at each position of gouging during

manufacturer, resulting in a place for fracture if the flutes bind

in dentin and the handle rotated. Also, if it is handled incorrectlyand rotated clockwise after binding in dentin, its screw like

configuration may further drive the instrument apically and crack

the weakened and stressed root. They are especially indicated inthe instrumentation of immature teeth, where the walls are

irregular and may harbor considerable debris, also useful in

removing silver points or loose broken instruments from canals.

Both)-style of reamers and files are available in three shaftlengths (7, (8 and /7 mm for anterior and posterior teeth. The

si!es of both )-styles are designated according to the diameters

of the instrument at specified positions along its length. The tipsdiameters increase in +.+8mm increments up to si!e *+ file, and

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then by +.7mm increments up to si!e 79+. The diameter at the tipof the point is known as :+. The spiral cutting edge of the

instrument must be at least 7*mm along, and diameter at this

point is :7*. The file diameter increases at a rate of +.+(mm perrunning millimeter of length.

Color coding:

&ee the power point file

Restoring forces:

Any instrument action requires an engine. An endodontic file or

reamers has two parts' the operators hand and the instrument

shaft. The hand force engine is obvious, but the instrumentengine is not. As instrument is curved, elastic forces develop

internally. These forces attempt to return the instrument to its

original shape and are responsible for straighten of the final

canal shape. These internal elastic forces $called Restoringforces% act on the canal wall during preparation and influence the

amount of dentin removed. They are particularly influncential atthe unction of the instrument tip and its cutting edges. This

unctional point is the most efficient cutting surface along an

instrument. ;hen activated by the restoring forces, it removes

more tissue than can any other region of the file. 2estoringforces are what power of the changes in canal shape as they act

through the sharp surfaces of an instrument.Restoring forces

are directly related to the metal composition of the instrument,the cross-sectional area of the instrument, and the angle of

deflection. The greater the angle of deflection, the greater is

the power. The larger the instrument, the larger is the cross-

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section and the greater the power. The more rigid the materialthe instrument is manufactured from, the greater is the power.

So ho! can the dentist control this force"

7. 2adicular access minimi!es the deflection of all subsequent

instruments. This effectively increases the radius and

decreases the arc of the canal curvature by allowing theinstrument a straighter path to the apex, which generate a

lesser restoring force along its cutting edges and tip.

(. A triangular cross section is preferred, especially as apical

preparation diameter increases beyond a lessthan that of a square file of the same standardi!ed si!e. #y

using a specific method for calculating of restoring force ofboth instrument $reamer and file% of the same si!es, they

found that the triangular file would be expected to develop

only *(.8> as restoring force against the canal wall as squarefile assuming both were placed through the same curvature.

/. ?ess rigid metals.


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The ratio of the increase in stress to level off to progressivedeformation even if strain is added due to the martensitic

transformation. This results in the so-called super-elasticity, a

movement that is similar to slip deformation. The differencesbetween the behaviors of


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accomplished in different ways. Bne is by vibratory motion of theinstrument which is moved up and down in the root canal will,

abrade the root canal walls. avitation and acoustic streaming are

other properties of ultrasound. avitation is the formation ofcavities in the liquid and their subsequent collapse, which is

accomplished by intensive hydraulic shocks strong enough to

destroy metal obects. Acoustic streaming is the rapid movement

of fluid particles in vortex-like motion about a vibrating obect.

Sonic %nstr&ments The Cndo 78++ was developed as a sonic vibratory

handpiece to be attached to the turbine line of a dental unit. The

handpiece operates at a frequency of 78++ 3! and acceptsspecially designed icro-ega files.

any type of hand and power assisted instruments, are

available that claim to benefit one over the other, but theproceeding will be a receiving of the root canal preparation using

&t-&t and


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The differences are'7. The cutting head is much smaller on the Dates vs. the

"eeso.

(. The shaft is thinner on the Dates vs. the "eeso/. The diameters of the heads are different for the same

number instrument.

1or example, the numbers on both the Dates and the "eeso are

denoted by the number of circumferential grooves located on theshaft ust below the cutout for the latch.

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endodontic instument