Perforation / orthodontic courses by Indian dental academy

Introduction

The complexity of the root canal systems, make it impossible to sterilize

them.

Fortunately in most cases of root canal treatment a reduction in the

microbial content of the canal system in system is sufficient to promote

periradicular healing.

In the mechanical method, metallic instruments of graded sizes are used

to remove intracanal dentine together with microorganisms. The method

largely relies on the ability to clear a significant surface area of molecular walls

of the RC system.

Microorganisms may be destroyed by antibacterial fluids to irrigants.

The combined action of mech and chemical cleaning is more efficient

than either method alone, and allows a more conservative canal preparation.

Objectives : Of Cleaning and Shaping the root canal.

Generally speaking the two main objectives in canal cleaning and

shaping are biologic and mechanical.

Biologically, the goal of intracanal procedures is to remove all pulp

tissue remnants and microorganisms and their substrates, along with infected

dentin and predentin.

Mechanically, three-dimensional shaping of the canal is the objective

I. Biologic objectives :

The biologic objectives are as follows.

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1. Confine all instruments within the root canal space

2. Avoid pushing contaminated debris past the canal confines of the apical

constriction.

3. Remove all the potential irritants from the entire canal system.

4. Establish the exact working length and completely clean and shape the

canal system during the first treatment visit.

5. Create sufficient width in the coronal half of canal system to allow for

copious flushing and debridement.

II. Mechanical objectives :

1. Prepare a sound apical dentin matrix at the dentine.

Cementum junction – The development of this matrix provides the resistance

form to the intraradicular cavity preparation.

- The matrix or canal narrowing prevents over extension of instruments and

controls the apical movement of gutta percha and sealer during obturation.

Matrix resistance

2. Prepare the canal to taper apically, with the narrowest cross-sectional

diameter at the apical termination (apical dentin matrix)

The Retention

3. Develop a continuously tapering funnel – type preparation in three

dimensions within the entire root canal system.

The objective addresses the need to view every root canal system as a

unique individual three dimensional system. Adherence to this concept also

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parallels the “extension for prevention” concept that is, through removal of the

irritant enhances through canal obturation.

4. Confine clearing and shaping procedure to the canal system.

- Adherance to this principle presents violation of periradicular tissues.

- This principle is evident when foramina are transported during excessive

instrumentation.

Foraminal transportation can be either

1. External

2. Internal

1. External transportation takes a forms and may occur when instruments is

carried out beyond the apical dentin matrix.

i. One result is the ripping of the apical end of the canal resulting in a:

i. teardrop

ii. elliptical

iii. Zipped foramen

ii. In its grossier form outright perforation of the root results.

2. Internal transportation occurs when excessively large instruments are used

in the apical third of a curved canal.

Results in :

1. Ledging

2. Canal blockage

3. Loss of canal length

4. Development of false canals.

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Generally, both types of transportation’s of the apical foramen can be

prevented by containing cleaning and shaping procedure within the canal

system.

5. Remove all residue of cleaning and shaping procedures that could prevent

patency of the apical foramin – that is

Removal of debris is accomplished with a NaOcl or 15 file along with

copious and frequent irrigation. This is known as RECAPITULATION and is

essential to all cleaning and shaping procedures.

Anatomic Considerations in radicular cavity preparation

The primary objectives of precise measuring and confirming of the

length of tooth is to limit instrumentation and subsequent filling to the root

canal.

The apical termination of the canal is thought to be the junction of the

internal dentin and the external cementum, the cemento dentinal junction at the

foramen.

Kuttler, Green and others demonstrated that this cemento dentinal

junction is after found about 0.5 to 1mm from the external surface of the root

seen in the radiograph.

Once a good deal of experience is gained, the clinician may be able to

find the foramen.

If the patients are not anesthetized, their reactions may often be counted

upon. There is a decided difference in discomfort reaction between the

instrument touching or even approaching the periradicular tissue at the CD

junction and an instrument touching a shred of remaining vital pulp.

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Pulp remnants evoke a sharp instantaneous response where as the

reaction at the cemeto dentinal junction ranges from a mild awareness to

possibly no reaction at all. Any warning at all by the patient calls for a

reconfirmation of the tooth length.

Techniques of Radicular Cavity Preparation

Over the years there has been a gradual change in the ideal configuration

of a prepared root canal. At one time the shape was round and tapered, almost

parallel.

After, schilder’s classic description of “cleaning and shaping”, the more

accepted shape for the finished canal has become a gradually increasing taper,

with the smallest diameter at the apical constricture, and terminating larger at

the coronal orifice.

This gradually increasing taper is effective in final filling, for a

Buchanan has pointed out, the “apical movement of the core in to the tapered

apical preparation----- only tightness the apical seal.

As previously stated, two approaches to debriding and shaping the canal

have finally emerged

Either starting at the apex with fine instruments and working one’s way

back up the canal with progressively larger instruments – the SERIAL OR

“STEP – BACK” technique.

Or, starting at the cervical orifice with larger instruments and gradually

progressing towards the apex with smaller and smaller instruments – the

“STEP – DOWN” – technique also called “CROWN – DOWN” technique.

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Methods of Instrumentation

Many methods of instrument action within the canal system have been

expressed over the years. The most common of these actions is the PUSH-

TURN PULL MOTION.

In which a K-file is inserted to the working length and given 1/6, 1/8 or ¼

turn, engaging the canal wall and then with drawn with pressure against the

canal wall.

The push pull action is referred to as the “filing action” and is often

considered adequate for straight canals is larger teeth.

A “REAMING ACTION” is defined as a boring action designed to drill

out an apical matrix and remove irregularities in the apical third of the

canal this approach is limited to straight rooted larger canals.

The major problem with both of these techniques is that neither takes is to

account the degree of irregular canal anatomy often encounted.

“CIRCUMFERENTIAL FILING” is defined as moving the file around the

circumference of the canal space while at the same time stroking the

instrument is a 1-3mm amplitude.

Favors the development of a flared as funneled canal

preparation

Aids in opening orifices of the canals.

Finally the tooth anatomy dictates the technique or goal of teaching.

According the STOCK, he divided the Biochemical preparation

techniques in to

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I APICAL – CORONAL technique

In which the WL is established and the

full length of the canal then preparation,

sequent increasing in size.

- Standardized preparation

- Step back preparation

- The ROANES technique

(Balanced force techniqe)

II CORONAL - APICAL techniques

Coronal potion is prepared before the WL

is determined, sequentially prepared from

coronal end to full WL.

- Step down techniqe

- Double flared technique

- Crown down preassureless

technique

- Canal master technique

Disadvantages of APICAL – CORONAL preparations

Potential for extrusion of debris.

Apical blockage

Alteration of working length

Tendency for canal discrepancy, when large inflexible instruments are used.

Coronal Apical techniques (ADVANTAGES)

Early debridement , under extension of debris.

Early coronal widening, better, access, decreases penetration of irrigant

Better control over apical instrumentation.

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Step Back Preparation

Weine, Martin, Walton and Mullaney were early advocates of step-back,

also called Telescopic or Serial Root Canal Preparation.

Designed to overcome instrument transportation in the apical third

canal, it has proved quite successful.

This method of preparation has been well described by Mullaney.

Mullaney divided the step-back preparation into 2 phases.

Phase I : Apical preparation starting at the apical constriction.

Phase II : Preparation of the remainder of the canal, gradually stepping back

while increasing in size.

Although the stepback was designed to avoid zipping the apical area in

curved canals, it applies as well to straight canal preparation.

It has been mentioned that the guide line for the termination of the apical

preparation has been cited as three sizes larger than the first instrument that

binds at the apical terminus.

The fall range of sizes is recommended as a guide time for the shape of

the canal system, type and flexibility of the instrument used.

One of the first axions of endodontitis is “always use a curved

instrument in a curved canal” curving the file to match the canal is paramount

to success in the step-back more ever.

Figure 2 – Step-Back Preparation :

A. Phase I – Apical preparation up to file No. 25 with recapitulation using

prior size files.

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B. Phase II – Stepping –Back procedure in 1mm increments Nos. 25 through

45, Recapitulation with 25 file to full working length.

C. Refining phase II-A – Greater glidden drill No. 23 and 4 used to create

coronal and mid root perparations.

D. Refining phase II-B No.25 file, circumferential filing smooths step-back.

E. Completed preparation – a continuous flowing flare preparation.

Step-Back – Phase I – It must be assumed that the canal has been

explored and the working length of the tooth has been established, i.e, the

apical constriction identified.

- The first active instrument to be inserted should be a fine (No. 08, 10, or 15)

K-file, curved, and coated with a lubricant such as gly-oxide, Root canal

preparation or liquid soap.

- If a curved No.15, for example refuses to go to place easily, are drops back

to a No. 10 or even a No.8.

- The motion of the instrument is “watch winding” two or three quarter –

turns clockwise counterclockwise and then retract. Upon removal, the

instrument is wiped clean, recurved, relubricated and repositioned, watch

widening is then repeated. This procedure is repeated until the instrument is

loose in posterior.

- The next size K-file is used in the same manner, very short (1.0mm) filing

strokes can also be used at the apex.

- It is most important that a lubricant be used in this area. In very fine canals,

the irrigant that will reach this area, will be insufficient to dissolve tissue,

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lubrication emulifies tissue allowing instrument tips to macerate and

remove this tissue.

By the time a size 25 K-file has been used to full length, phase I is

complete.

- It is emphasized here that irrigation between each instrument use is now in

older, as well as recapitulation with the previous smaller instrument carried

to full depth and watch wound. All these maneuvers will ensure patency of

the canal to the apical constriction.

II Phase II –

- In a fine canal, the step-back process begins with a No.30 K-style file. Its

working length is set one millimeter short of the full working length. It is

precurved, lubricated, carried down the canal to the new shortened depth,

watch wound and retracted.

The same process is reported until a No.30 is loose at this adjusted

length (Figure). Recapitulation to full length with a No. 25 file follows to

assure patency of the constriction.

The next curved instrument i.e., No. 35 again shortened by 1.0mm from

the No. 30. (2mm from the apical No.25). It is curved, lubricated, inserted,

watch wound and retracted followed by recapitulation and irrigation.

Figure:

- A step-back /telescopic preparation. Working length of 20mm used as

example.

- Coronal part of canal enlarged with circumferential filing or Gater Glidden

drills.

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- Thus the preparation step-back up the canal one millimeter and one larger

instrument at a time.

- It is at this point that H-files are effectives, this is also the area of canal

preparation that can be done with power driven, Gater Glidden drills

starting with the smaller drills (No.1 and 2) and gradually increasing in size

to No. 4,5 and 6. Proper continuing taper is developed to finish phase II A

preparation.

- Refining phase II B is a return to a size No.25 instrument, smoothing all

round the canal walls with vertical push-pull stroker to perfect the taper

from the apical constriction to the cervical orifice – safe ended H-file is

most efficient.

- At this point Buchanan recommends NaOcl to left in place to the apex for 5

to 10 minutes. This is only way the auxiliary canals can be cleaned.

- Hand powered Gates Glidden drills may be used for final finish.

According to Grossman

Advantages of the step-back preparation over the conventional method.

1. Less likely to cause periapical trauma.

2. Facilitates the removal of more debris

3. Greater flare facilitates packing of additional G.P. by lateral/vertical

condensation technique.

4. Development of apical matrix / prevents overfilling.

5. Greater condensation pressure can be exerted.

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Negotiation of narrowly Curved Root Canals : (According to Grossman)

- The apical segment of the root canal is cleaned and shaped with a prepared

No.10 file and shaped to canal length.

- Figure – modification of an instrument to clean and shape narrow root

canals.

A. Sequentially larger file is found to be short of the working length.

B. One millimeter is cut off a smaller file.

C. The tip is reestablished with a diamond file.

- If the next prepared file (No.15) binds firmly 1mm or 2mm short of the

working length, it should not be forced apically beyond this point of cotnact

(Figure).

- The No.15 file is removed, and the canal is irrigated with a 5.2% solution of

sodium hypochlorite. Because the next size file is not available, the operator

can create one by cutting off part the instrument tip of the No. 10 file.

- Cutting off 1mm of the tip of No.10 file converts it into a No.12 file.

- The stainless steel tip of a file can be cut with sharp iries scissors (Fig). A

diamond file is used for reestablish and to smooth the inter tip. The

instrument is curved, sterilized and is ready for use in the apical third of the

preparation.

- Figure 2

Variation in cleaning and shaping for double curved or S- shaped root

canals. A small H-file is used to reduce the middle third curve of the root canal

and leaves only the apical curve to be instrumented.

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Double-Curved Root Canals :

Double curved or bayonet shaped canals are cleaned and shaped with

one main variation.

- When the area of the apical foramen has been cleaned and shaped with a

prepared No. 10 file, the middle third curve is eliminated by filling it with a

H-file that straightens out the enlarged canal. (Figure).

- A small H-file is introduced into root canal until the junction of the middle

and apical thirds reached. The liner portion of their curves is then filed

away.

Dilacerated Root Canals :

Dilacerated or extremely curved canals can be instrumented by

enlarging the middle and cervical third of the root canal first.

Figure – Modify of instrument to clean and shape a dilacerated root canal.

A and B, root canal before and after cleaning and shaping.

C- the flares of small, curved file are dulled on the outer portion of the

apical third and on the inner portion of the middle third of the root canal.

- A small H-file is inserted to the beginning of the dilaceration – without

forcing the file apically circumferential filing is prepared once, and canal

irrigated and refiled to working length with a prepared No.10 file.

- Repeat this procedure until the middle and cervical thirds are open wide

enough that the apical third can be instrumented without forcing the

instruments.

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- When the cervical and middle thirds of the canal are open, one should

prepare a No.15 file by dulling the flutes on the outer portion of the apical

third, and the inner portion of the middle third of the curved instrument

(Figure).

- This procedure prevents transportation of the apical foramen and over

instrumentation in the dilacerated area.

Modified Manipulation of Instruments :

Anticurvature filing :

- Denotes filing preferentially away from the inner curvatures or facial

aspect, the site of potential perforation.

- This method, involves filing buccal, mesial and ling walls of the root

canal with more strokes than the furcal wall by a ration of 3:1 is

effective.

Step-Down Technique

Initially, Marshall and Pappin advocated a “Crown Down Pressureless

Preparation” in which Gates Glidden drills and larger size files are first used in

the coronal two thirds of the canals and then progressively smaller files are

used from the “crown down” until the desired length is reached. This has

become known as the Step-down technique.

- The primary purpose of this technique is to minimize or eliminate the

amount of necrotic debris that could be extruded through the apical foramen

during instrumentation.

- One of the primary advantages of the step-down preparation is the freedom

from constraint of the apical enlarging instruments.

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- By first flaring the coronal two-thirds of the canal, there is increased access

allowing greater control and less change of zipping near the apical

constriction.

- In addition, it “provides a coronal escape way that reduce the piston in a

cylinder effect” responsible for debris extrusion from the apex”.

Step-Down technique :

In this method, working length of tooth is not first established. The

access cavity is filled with NaOcl and the first instrument is introduced into the

canal.

Figure – (Step-Down canal preparation) :

Straight canal used as example :

A. “Pre-Gates” preparation of coronal half of canal to receive second phase

instruments.

B. No. 2 Gates Glidden drill widens preparations to receive.

C. No. 3 Gates glidden (size of 80 file) to provide unobstructed access for

instrument to follow.

D. Starting with larger instruments (No.40), canal is progressively enlarged

apically 1 to 2 mm at a time until.

E. No. 25 file reaches cemento dentinal junction.

If it appears that a No.35 file until pass, it is carried into the canal to the

point of resistance. If resistance is encountered at (for instance) 13mm

(FIGURE) the preoperatives radiograph is consulted to determine if it is canal

curvature or narrowing that is stapping the instrument.

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Radicular access is now prepared upto this point taking care not to ledge

the wall of a curve begins here.

If No.2 Gates Glidden drill (size of a No.60 file)followed by a No.3

Gates (size of a No.80 file) is used without apical force to flare out the

radicular access (FIGURE) and copious irrigation follows.

If initially the No.35 Instrument does not penetrate to this depth, smaller

instruments must be used to prepare the radicular access upto this size before

the Gates Glidden flaring begins. This is referred to as “PRE-GATES

PREPARATION”.

At this point, Morgan and Mantgomery suggest that “a provisional

working length”, 3mm short of the radiographic apex be established. The next

step of preparation now begins in the presence of NaOCl.

A No. 30 file is placed in the canal until resistance is encountered and is

rotated twice in a clockwise passive penetrating movement.

Then a No.25 file repeats this reaming procedure, fall by a No.20, a

No.15, etc. until the provisional working length is reached.

At this point, true working length must be established at the apical

construction.

This is the point of resistance form. Irrigation follows.

To make sure the apical area is thoroughly cleaned, successively larger

files are used to reach the construction until a No.25, at least is used to full

working depth (FIGURE).

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Final smoothening of the walls and perfection of the continuing flaring

shape are accomplished with No.30 to 35. Safe end H-files used

circumferential.

Efficacy of the step down technique Compared to the step-back

“circumferential filing tech with precurred files. Morgan found that the step-

down tech had better shape and terminus.

Another study found less belives extruded from the apex with the step

down tech.

Positive disadvantage include

1. Hedges

2. Apical blackage

3. Perforations especially in narrow canals but may be overcome by

careful manipulation of files and frequent recapitulation.

HYBRID TECHNIQUE (Step – Down / Step Back)

GOERIG, and later BUCHANAN suggested a combination of the step-

down / Step – back technique

- Buchanan preparation what he calls Early Radicular Access (ERA) which is

a step – down process, preferably done with Gates glidden drills with No1

and advancing up through No6. This is carried out in straight part of the

canal.

- In the event a No.1 Gates cannot be introduced, Buchanan prepares a “Pre-

Gates” canal space with smaller files until the No1 Gates will effortlessly

reach full depth. This is followed by a No.2, then the No.3 at half depth and

a 4, 5 and 6 only at the orifice level.

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- Once the coronal flaring in complete true working length, may be

established at the apical constriction. This is where resistance form will be

established.

- The Step-Back part of the preparation begins with a precurved, lubricated,

fine file (No. 8, No.10 or No 15) inserted passively. Step back begins with

the next larger inserted passively. Step back begins with the next larger size

instrument 1.00 short of working length. As each larger precurved

instrument is introduced the step-back is 1.0mm until the previously

prepared step down portion of the canal is reached.

- Following extensive irrigation the entire canal is correctly tapered with a

small H-file.

- Out of these 2 methods, The hybrid approach was developed.

Starting coronally with larger instruments, often power driven, one

works down the straight coronal portion of the canal with progressively smaller

instruments – the step-down approach.

Then at this point, the procedure is reversed starting at the apex with

small instruments and gradually increasing in size as one works back up the

canal – the step – back approach.

This HYBRID approach could be called – STEP –DOWN-STEP

BACK technique or MODIFIED DOUBLE FLARED TECHNIQUE.

Any one of these methods of preparing the root canal will ensure staying

within the confines of the canal and delivering or continuously tapered

preparation and as Buchanan has noted, eliminate blocking apical ledging,

zipping and perforation.

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STANDARDIZED PREPARATION

The premise of this technique is that most root canals are circular in

cross-section in the apical third, the aim is to prepare the root canal by

enlarging it sequentially to a selected size as follows.

Determine the WL

Introduce the smallest reamer into the canal and rotate it clockwise to

engage dentin and then withdraw.

Repeat with successively larger reamers until the reg. Size is reached

apically (size 20)

A canal shape should be produced, which matches the last reamer.

This technique occasionally works, particularly if the canals are narrow,

of circular cross section and enlarged to a large canal size. The technique is

unlikely to debride canals with more complicated shapes.

BALANCED FORCE CONCEPT USING FLEX-R-FILES:-

After 12 years of experimentation, Roane and Sabala introduced their

Balanced force concept of canal preparation.

Essentially, the entire preparation beginning with flaring of the canal

coronal and middle thirds of the canal with Gates glidden bills, size 1 through

6. This essentially increases the radius and decreases the arc of the curve of the

canal, thus making it straighter and more assessable to reaming instruments

At this point, the balanced force instrumentation begins. It involves

placement, cutting and removal using only rotatory motions.

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Insertion is done with a half-turn clockwise ratio with slight apical

pressure.

Cutting is accomplished using counter clockwise rotation, “again with

apical pressure, adjusted to match the files strength is very light for fine

instruments and heavy for large instruments”.

FLEX-R-FILE

Machine from a blank of triangular cross section.

Resembles a twisted instrument.

Greater contract of strength and flexibility.

Increased flexibility and increased strength

Designed to cut most efficiently in Anti clockwise rotatory motion.

Modified safe ended tip.

THE ROANE TECHNIQUE (B-T)

Main features

1. Canals prep to predesigned dimensions, of which 3 are recognised and

designated 45, 60 and 80 accord to size of apical prep

2. These dimension refer to size of the file used at the 3rd Step back to the size

of MAF.

Each step back from MAF at the Ph is 0.5mm shorter.

3. Prep to Radiographic length.

Raane firmly believes in enlarging the apical area to sizes larger than

generally recommended up to size 80 in single canal teeth, for example and

size 45 for multiple canal teeth. These sizes are not absolute, of course and

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final shaping depends upon treat bulk and/or fragility, or extreme curvature of

the canal.

He also believes in carrying the preparation through to “full length” the

radiographic apex of the teath.

Preparation with large instruments (i.e., 30) extents to full root length.

Use of larger instruments in the 2nd and 3rd steps forms apical constriction.

In canals to the prepared to a No.45 instrument, for eg, the No.30

instrument is carried to full root length root length and larger instruments are

stepped back from that No.40 at 0.5mm back, No.45 at 1.0mm back up the

canal until Gates Glidden preparation is reached.

Clockwise rotation, which “sets” the instrument, should never exceed

180 degrees; otherwise the instrument will start to unwind.

In this way and counterclockwise cutting and removal, the instruments

advance toward the apex, continuing this technique, the clinician enlarges the

apical third of the canal by advancing up the scale of larger and larger

instruments. Flex-R files prevent the instruments from gouging into the curved

walls. The Flex-R files are not pre curved and are used in a controlled rotatory

motion, which is said to balance forces acting on a file in a curved canal and

prevent procedural errors.

“When enlargement has been accomplished, a final year clockwise

cleaning rotation is used to load canal debris into the flutes and to elevate the

debris away from the apical foramen”. Irrigation follows.

Canal Master:

- The cutting portion of this instrument resembles a reamer with blunted

edges.

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- 0.75mm non cutting pilot tip

- Most efficient means of cutting cutting is using a clockwise rotating motion

thro’ 60°.

Canal master ‘U’

Canal Master technique:

Redesigned so that only the apical 1-2mm is engaged in dentin removal.

Apical 0.75mm of inst., is safe-ended to facilitate maintenance of canal

curvature.

Claimed this tech avoids the need for recapitulation.

Canal Master ‘U’ Preparation

Senia and Wildey completely redesigned endodontic instruments and

introduced the canal master “U” instrument. The canal master more closely

resembles a Gates Glidden drill in appearance and action.

Technique : A (step down/ step back) approach is recommended in using these

instruments.

Length of the tooth is first established, followed by circumferential filing to

the apical constriction up through a N0. 15 file. Capious irrigation is used

throughout.

When full canal potency is established, the step-down flaring of the

cervical-mid canal is carried out using the canal master rotary instruments

in a slow speed hand piece.

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A limit to the depth of the powered rotary penetration is necessary, so a

provisional rotary length (PRL) is established at either the 1st curve in the

canal or 5.0mm back from the apex.

Starting with No. 50 rotary instrument, the canal is enlarged to the PRL.

The No. 50 is followed by the no. 60, no. 70, no. 80 until a flare is

established.

Slow gentle apical pressure is used with each rotatory instrument followed

by recapitulation to the apex with the no. 15 file and irrigation.

At this point the canal is flooded with 17% EDTA which is allowed to

remain for 5 minutes. Then hand instrumentation begins, taking off from

the PRL with a No. 20 canal master ‘U’ instrument. It is used in a gentle

pressure, rapid full clockwise motion being constantly rotated as it cuts its

way to full working length.

Preparation continuous, advancing up the instrument sizes until one feels

that the apical area is completely debrided, for e.g., to size 35 or 40.

To complete the flare, a step back procedure follows, shortening by 1.0mm

each successively larger canal master – No. 45, 50, 55, 60, 70, 80 etc.

Final smoothening of the canals can also done with a non cutting tip H file

used circumferentially.

Through evaluation of this technique is needed, but early results seem

promising in terms of the shape produced.

Intermediate file sizes are available, enabling cases negotiated of curves.

The instruments have a tendency to fracture. The disadvantages are

those of any technique using purely rotating motion.

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NiTi Power File Preparation:

- McSpadden developed a SENSOR FILE a variation of the original

Hedstreem files, that varies in design with the size of the instrument, these

instruments have 3 flutes, the 3rd flute set at half the angle of the other z

shaped flutes.

- These files are produced in all sizes in stainless steel and in sizes 35 and

above in nickel-titanium.

Technique – After establishing tooth length, McSpadden begins a step-back

preparation with a Na. 15 NiTi instrument in a controlled, slow speed (Less

than oo RPM) rotating hand piece. The no. 30 and 25 are similarly used.

Step down tapering is begun in the cervical mid canal with either the larger

size NiTi or Gates Glidden drills.

The apical preparation is then completed with step back, larger and larger

instruments to meet the mid canal preparation. Final canal cleaning is done

with a CaviEndo ultrasonic system.

Canal Finder System Preparation

Canal Cleaning and shaping with the automated, air driven canal finder

system handpiece and ‘A’ style headstroem filler is best done as a step-down /

step-back preparation.

The unique features of ‘A’ files are :

1. Step depth of fillers.

2. 40 Degress helical angle of cutting blades.

3. More efficient cutting results.

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- The canal finder is more effective than any other technique or deveice in

negotiating very fine, very curved or even partially calcified canals.

- The canal finder delivers a vertical stroke that “drives the special H-files

apically with the non cutting plane tip.

- The instrument and the canal must be well lubricated with soluset (contain

EDTA and similar to root canal preparation).

- At this point step-back preparation begins, starting with a No. 8 or 10,

followed by No.15 up the scale until the apical area is enlarged to atleast

No.25.

- Stepping back from apex, a fully flared cavity is developed by the files

forced against all of the canal walls as it strokes vertically.

- Because H-files cut in a pulling motion, the canal finder is less apt to force

debris apically.

ULTRASONIC SYSTEMS

Ultrasonic endodontics has brought a new era of biotechnology to root

canal therapy. This technology which has ultrasound energy, continues the

traditional endodontic concepts of debridement and irrigates with ultrasonic,

biologic, chemical and physical actions.

Root canal systems are rapidly and effectively cleaned, irrigated,

disinfected and shaped by the clinician using an ultrasonic system.

Preparation of root canal with ultrasonic system for canal obturation

consist of 4 interrelated and dependent phases.

1. Mechanical debridment of hard and soft tissue within the canal system

2. Chemical debridement the canal system

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3. Disinfection

4. Final shaping of the canal system

Diamond coated files have also been introduced to the combination of

ultrasound energized debridment, activated irrigation and aid in canal cleaning

and disinfection.

Technique : Initial root canal lengths determination and apical preparation are

accomplished with small hand files.

- Subsequent canal preparation is performed with smaller sized ultrasonic

files, which are precurved prior to entry into the canal.

- The file motion used in ultrasonic root canal preparation is essentially a

push – pull action enhancing dentin removal.

- Circumferential more cement of the files is also associated to achieve the

smooth tapering canal shape.

- A side to side action or lateral morcement activates the irrigant solution,

which improves its disinfecting and cleaning qualities.

For Endosonic system the manufacturer recommends that 2.5% Sodium

hypochlorite solution be used to derive the maximum benefit of ultrasonics.

The continuous, high volume, flow-through irrigation and aspiration,

within the root canal, create the equivalent of an “ultrasonic bath”. This allows

three – dimensional debridement of the complex root canal marphology by the

hydrodynamic action and enhanced physical chemistry of the activated irrigant.

- The combination of continuously activated irrigation and the energized files

produces a multidimensional synergistic system that results in a biologically

cleaner root canal systems.

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- The combination of ultrasonic waves and a microbiocide results is an

extremely efficient system. The improved effect is due to the

1. Agitation

2. Acoustic streaming

3. Cavitation

Created by the ultrasonic waves emitted from the energized file.

However, extreme care must be exercised in areas of the canal system

where the canal is close to the external root wall – for e.g., Mesial roots of

mandibular molars. Because of the efficiency of ultrasonic cutting, rapid

perforations may occur.

SONIC SYSTEMS:

The development of the Endostar 5 and the endo sonic air 3000

introduced sonic vibratory canal cleaning and shaping to endodontics.

- The sonic cutting that accurs, coupled with the sonic irrigating solutions

reduces fatigue and stress during canal preparations.

- For canal cleanliness, ultrasonic activation with a No. 15 file for 3 full

minutes in the presence of 5% NaOCl produced “smooth, clean canals, free

of the smear layer and superficial debris.

Laser Canal Preparation

Still to be approved by the U.S. Food and drug administration

committee on devices, is the use of lasers to prepare root canals, nonetheless

the method appears promising.

Weichman was probably the first to suggest laser canal preparation.

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Levy has seriously pursued the use of the Nd-YAG laser mounted with a

fiber optic, to clean and shape the root canal.

“The attached fiber optic has a silicon base and a diameter of 200

microns, the diameter of a No. 20 file.

- The laser used in this study was a 35 watt pulsed Nd-YAG which produces

a beam with a wavelength of 1.06 microns.

The beam is carried through a silica fiber accompanied by a cleaning

system that delivers a spray of air and water.

Levy compared the results of cleaning and shaping by conventional

step-back procedures to laser beam, using SEM evaluation, Levy claimed “that

preparation with a laser beam is possible, with an improvement in the

cleanliness of the canal walls when compared to the conventional technique”.

Technique :

- For a full minute, the apical region of the canal is hand instrumented to the

constriction with a No.15 K-file and abundant irrigation.

- Preparation begins with the laser energy level set at 150 millijoules.

- The spray was reduced or increased so that the plasma effect could be

observed at the end of the fiber when contact was made with the dentin. It

appears as a Bright spark.

- The plasma effect is actually a laser “transformation of the dentin into an

ionized gas levaing no debris in the canal walls.

- The fiber optic was inserted to working length and enlargement was

performed circumferentially starting in the apical third, then the middle and

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finally the cervical third to the size No.60 instrument. The average time to

accomplish this preparation was one minute.

- The laser preparation, showed remarkable cleanliness of all canals, the

dentin revealed a crusty, waxy aspect with open tubules and no apparent

smear layer.

- Wilder Smith feels that the eximer laser may have a bright futures in

endodontics. A wavelength of 193nm the ArF eximer “is well suited to slow

selective removal of necrotic debris from the root canal.

- The laser appears to have a future in endodontics and only time will tell

how long lasting and efficacious it is.

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