RETREATMENT

Endodontic retreatment has traditionally been referred to as an attempt to rectify

unsatisfactory completed treatment.

The current American Association of Endodontics Glossary of Contemporary

Terminology for Endodontics defines retreatment as:

“A procedure to remove root canal filling materials from the tooth and again clean,

shape, and obturate the canal; usually accomplished because the original treatment

appears inadequate or has failed or because the root canal has been contaminated by

prolonged exposure to the intraoral environment”.

The limitation of this definition is that it describes only one kind of retreatment (i.e.

the kind that requires removal of filling materials) and ignores many other kinds of

retreatment such as a tooth referred to an endodontist to locate the canal the referring

doctor fail to locate. This is certainly retreatment, although it has nothing to do with

removing canal-filling materials.

The retreatment of failed apicectomy on calcified canals consisted of non-surgical

cleaning, shaping and obturating of the canals. This too is retreatment, although,

again, no filling materials were removed from the canals.

A completed case with a missed MB-2 canal needs non-surgical retreatment, but no

filling materials were removed in the process.

New Definition

“Endodontic retreatment is a procedure performed on a tooth that has received prior

attempted definitive treatment resulting in a condition requiring further endodontic

treatment to achieve a successful result”.

Many specialists note that 30 to 50% of their practice is retreatment.

Objective of Retreatment

Is to perform endodontic therapy in order to return the treated tooth to function and

comfort and to allow the supporting structures to repair completely.

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Classification of Retreatment

Teeth requiring retreatment may be classified as follows:

1- Discontinued treatment by prior dentist.

2- Incomplete retreatment

3- Complete, but inadequate treatment.

4- Complete and apparently adequate treatment but with questionable long-term prognosis.

- The success/failure ratio is not affected by age, sex, tooth type, size of lesion, location of

lesion, or number of treatment sessions, but is affected greatly by the operator’s skill.

- What is the success rate of endodontic therapy if the root canal system is completely

cleaned, shaped, and obturated? The answer to this question is that the success rate is

very close to 100%.

- Endodontic disease is a bacterial infection originating in the pulp and progressing

apically to the periapical tissue. In the absence of bacteria, periapical lesions donot form.

However, there are also examples of apparently completely debrided canal system that

doesn’t respond successfully to the treatment, hence must either undergo a surgical

procedure or extraction.

- Before retreatment pain of nonodontogenic origin should be ruled out (TMD,neurogenic

pain, vascular headache syndrome.etc.). odontogenic pain of nonendodontic origin eg.

Endodontically treated teeth subjected to occlusal trauma may remain persistently tender;

retreatment does not address the cause of this tenderness.

- Also periodontally involved teeth may remain sensitive after successful endodontic

therapy, especially to percussion and palpation. Therefore, careful periodontal probing

and recording are absolutely imperative before initiating any endodontic therapy.

- A decision to retreat must be based on having confidence regarding the cause of failure

and belief that retreatment can successfully correct the deficiency.

- Non-surgical retreatment is one alternative among several options. If the patient is

asymptomatic but a pathologic condition is present, a judgment must be made to simply

observe or treat.

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- The decision to observe although attractive to the asymptomatic patient must be tempered

by the consideration that failing, asymptomatic endodontics has a high incidence of

inopportune flare-up; delayed treatment frequently makes the eventual retreatment more

problematic.

- If treatment is chosen, the options are non-surgical retreatment, surgical retreatment, a

combination of both, or extraction.

- Factors such as oral hygiene, age, remaining dentition, patient motivation, probability of

success, and cost must be weighed in making a decision.

- The decision, which option to choose, must be made by the patient and clinician.

- It is wise to retreat non-surgically before any attempted surgical correction, unless there

are extenuating circumstances.

- Questionable cases, where there is inadequate endodontic therapy that is not failing with

no evident pathology, have to be retreated because of potential complications in the

future.

- Observing questionable endodontic therapy that appears to be successful is considered

acceptable treatment, but is not advised if the treated tooth is to receive a new restoration

or is to be included as a critical abutment in a comprehensive reconstruction.

- Among the iatral objects that block root canals; paper points, burs files, glass beads,

amalgam, gold fillings, plugger and spreader tips, gutta-percha, cements and sealers,

broaches, silver points, and posts.

- Among the object placed by patients in teeth left open to drain; nails, pencil lead,

toothpicks, tomato seeds, hatpins, needles, and pins.

Endodontic Retreatment

1. Gutta-percha removal

2. Silver point removal

3. Post and core removal

4. Separated instrument removal

5. Restorative filling material removal

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Gutta-Percha and Sealer Removal

Reasons for failure to obturate to the apex are as follows:

1. Anatomic complexity

2. Apical blockage caused by pulpal or dentinal debris.

3. Ledge formation coronal to apex.

4. Inadequate shape preventing apical seating of gutta-percha cone.

5. Blockage by instrument.

Retreatment of Gutta-Percha

After the canal orifice of the defective filling is uncovered, the adhesion of the gutta-

percha is tested with H-file.

If the gutta-percha filling is defective (poorly condensed), it may be removed by means

Of rotary instrument or pulled out in one piece by hand instrument.

Hedstrom files are engaged between the canal wall and the gutta-percha filling and then

the GP is retrieved in one piece by pulling back the instrument.

The same technique is useful in retrieving overextended gutta-percha through the root

canal. At times it may become necessary to bypass the gutta-percha with the file beyond

the apical foramen to assure that the overextended gutta-percha does not separate at the

apex.

If the filling is solid then the coronal portion of Gp should be removed preferably by

means of endodontic drills (such as the Gates-Glidden or pesos-reamer) and the apical

portion with solvents. This step has the following advantage:

1. Most condensed coronal portion is removed quickly

2. Reservoir is provided for the solvents

3. Improved convenience form is obtained for negotiating that root canal.

Hot plugger was also suggested to remove the coronal portion of gutta-percha. Although

some gutta-percha may be removed, creating a limited space for further negotiation and

for solvents, no more convenience is provided by this technique.

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Techniques for dissolving gutta-percha

Dissolving avoids the use of excessive force in negotiating of gutta-percha

Extrusion of solvent into periapical tissues should be prevented.

Solvents commonly used are chloroform, eucalyptol, turpentine, xylene, and halothane.

Chloroform

- The most effective and widely used.

- It evaporates rapidly and is therefore a useful chairside material.

- It’s a potential carcinogen.

- It’s toxic and harmful to the periapical tissues.

Xylene

- Highly toxic

- Evaporate too slowly to be used at chairside.

- Its dissolving effect is poorer than that of chloroform.

Eucalyptol

- Less irritant than chloroform and its antibacterial

- It is toxic when ingested

- It is the least effective gutta-percha solvent only when heated its effectiveness

comparable to that of chloroform.

Both chloroform and halothane can be effectively used in removing thermafil gutta-

percha filling with plastic cone carriers.

Technique

- Time consuming and occasionally yields limited results.

- Following the introduction of solvent, the canal is negotiated with files or reamers to the

desired length.

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- The working length is estimated from the preoperative radiograph and must be

confirmed radiographically during instrumentation of the canal.

- Large files are used high in the canal, decreasing markedly in size toward the apex.

- After the bulk of the old filling removed, circumferential filling is done to remove all

the gutta-percha and sealer form the walls.

- Evaluation of the coronal access and coronal enlargement of the canal with GG

Automated Instrumentation

- By passing gutta-percha with canal finder in automated handpiece and chloroform.

This technique is fast and safe, and short filled curved canals may be negotiated

beyond the obturation. Thus, a length radiograph may be obtained at an early stage.

- The canal finder system also has a built-in apex locator that may be used as an aid in

preventing over instrumentation with this technique.

- A GPX gutta-percha instrument can be used in slow speed handpiece. This instrument

is essentially a reverse of Mc Spadden compactor, which melts the gutta-percha and

directed coronally without contacting the dentin walls.

Ultrasonic Instrumentation

- Specialized ultrasonic tip can be used. These tips are heated when an activated by

ultrasonic energy and are fine enough to work around curvatures.

- Ultrasonic instrumentation following softening with chloroform does not facilitate the

removal of gutta-percha from the root canal, even when continuous irrigation with the

solvent is used.

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Retreatment of Solid Objects

Solid objects could be silver point, broken instrument or post

Causes of Fracture

1. Over-use of the Instrument

The small diameter instruments are most at risk and should be used once or twice only

and then discarded. Sizes 8 - 25 should be used once or twice and the larger sizes should

be inspected after use for signs of bluntness or distortion.

2. Sterilization

Repeated sterilizations increased brittleness in the fine diameter reamers and files.

3. Mishandling the Instrument in the Canal

- No endodontic instrument should be forced into a narrow canal.

- No barbed broach or spiral filler should be used unless it can be inserted freely to the

end of the canal.

- Reamers and files, especially small sizes, should never be rotated more than one-

quarter turn in the first application.

- Never miss out the next larger size.

4. Faulty Access Cavity

The access cavity must be prepared in direct line with the root canal.

In multi-rooted tooth, extension of the cavity for each canal alignment is mandatory.

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5. Faults in Manufacture

Although rare, it is possible to have a flaw in a file or reamer, which can lead to its

fracture. It is difficult to assess whether such is the case when an instrument fractures in

use. However, misuse is more likely to stress the defect, resulting in fracture.

- A readily accessible solid objects may be withdrawn from the canal by variety of

instruments including Stieglitz or perry pliers, a hemostat, a modified Castroviejos

needle holder, or a Caulfield silver point-extractor.

- Ultrasonic vibration facilitates this technique particularly if the object is cemented in

the canal.

- Whenever the object cannot be grasped, attempts should be made to bypass it to

possibly facilitate its removal or allow completion of canal therapy without its

removal.

Removal of Broken Instruments Bypassing with Hand Instruments

- When the fractured part extends coronally into a flared portion of the canal its

removal is easier. It can be grasped with Steiglitz forceps or tease it out with a fine

sharp excavator or by wedging a Hedstrom file against it and pulling. Masserann kit

can also be used.

- When the fractured part in the mid of the root bypass it clean the canal, shaped and

obturated to its proper working length.

- Reamers or files may be used to bypass an obstructing object in the root canal and

solvents may be used to soften its cementation.

- Multiple Hedstrom files may be inserted alongside the bypassed instrument and

twisted around it so as to provide sufficient grip for its retrieval.

- Intermittent irrigation, alternating sodium hypochlorite with hydrogen peroxide or RC

prep may float the object coronally through the effervescence they create.

- If the instrument can’t be bypassed, the canal should be cleaned, shaped, and

obturated to the coronal level of the instrument fragment.

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- The use of softened gutta-percha may extrude filling materials beyond the fragment

and may improve the prognosis, but only if the apical portion of the canal was well

debrided prior to the separation.

- When an instrument has been fractured near to the apex of the root, the ability to

remove it is related to how closely it fits the canal and how tightly it has been forced

against the walls especially when the canal is curved.

Investigators have shown that provided there is no rarefaction periapically, filling the

canal as far as the obstruction will lead to a successful result in the majority of cases.

- If the separated instrument is beyond the apex and there is subsequent failure, it may

be removed surgically.

Removal of Silver Points

It is postulated that the pathogenesis of silver cone failure occurs when serum

enzymes react with the silver ions to form silver salts, which are non-specific cellular

toxins. Although macrophages and lymphocytes mount an attack against these

toxins, the infinite supply of silver ions precludes their elimination.

Retreatment became necessary when endodontically treated teeth are failing, either

with symptoms or as determined by radiograph. In some cases, retreatment is needed

for prosthetic reasons, generally to accommodate a post-core type restoration.

Using Cyanoacrylate glue (Permabond or Superglue #3) and different gauge

hypodermic needles may be helpful in removing the silver point. One is selected

suitable needle that fits snugly, like a sleeve, over the protruding silver point. Adding

a drop of Cyanoacrylate cement may improve the grip.

A variation of this method employs a large gauge needle and a small Hedstrom file or

Unifile to be wedged tightly into the space between the needle and silver point.

Another unique approach uses orthodontic ligature wire and plastic tubing following

cutting a groove around the protruding butt end of the silver point with a round bur.

The ligature wire is then doubled over, and the two free ends are passed through the

tubing to form a loop at the end. This may loosen the silver point and bring it out.

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The Canal Finder System – vertical stroke handpiece can be used effectively to

remove silver points and fractured instruments.

Furthermore, a readily accessible silver point may be withdrawn from the canal by a

variety of instruments; including Stieglitz, a hemostat, or Masserann kit.

Recently introduced Endo Extractor, which differs from the Masserann kit only by

using a cyanoacrylate adhesive to lock the object into the extractor.

The microscopic approach to silver point removal has simplified this sometimes-

frustrating procedure.

- The case can readily be retreated as long as enough of the silver point is left

Protruding into the pulp chamber to allow it to be grasped and manipulated.

- The basic goal of any silver point removal technique is to break up any sealing

materials surrounding the point using solvents (chloroform, xylene or eucalyptol).

- The chamber is folded with solvent and an endodontic explorer is used in rocking

fashion to disrupt the cement’s seal.

- Only after the silver point is moving in the canal, should removal be attempted.

- If it still tightly fit, vibratory energy delivered by an ultrasonic unit is used to break

the seal.

Some silver points are sectioned at or slightly below the canal orifice, making it

impossible to be grasped by silver point pliers. Several methods have been suggested.

Three of the most popular approaches are the use of Steiglitz forceps or a fine hemostat,

“braiding” files around the silver point, or the Masserann kit.

The use of the Steiglitz or hemostat requires very generous coronal access and a significant

amount of silver point protruding into the chamber.

Trenching will usually give enough room for a thin-nosed pliers to be placed around the

point. A pure end-cutting bur of the tapered fissure series with a half-circle round cutting

end. Such bur works around the periphery of the silver point to be removed until a sufficient

trench is prepared without nicking, goaging, or reducing the silver point.

Then the thin-necked plier is placed firmly around the silver point to gain removal.

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The braiding approach, popularized by Glick, utilizes:

- Three small Hedstrom files that placed lateral to the silver point in the canal space.

- These files are twisted to engage the silver point and allow the point to be withdrawn.

- This seems best suited to rather large diameter points wedged in large root canals.

Masserann kit is especially useful for the removal of fractured post, instruments and

metal point that ledged in the coronal part of the canal.

- It consists of 14 different diameters of trepan (hollow, end-cutting burs), color-coded

for ease identification, that cut a trench around the silver point into tooth structure

- There are two trepans of each diameter one short and one long.

- The trepans may be screwed into the milled handle or mounted in a speed-reducing

handpiece.

- The smallest trepan that will fit around the fragment is selected by using one of the

gauges provided.

- The trepan is pressed over the end of the fragment and turned in an anticlockwise

direction. Irrigation will facilitate this procedure. This trench allows space for the

introduction of an extractor

- After few turns the trepan should be withdrawn from the canal and the accumulated

debris removed.

- The extractor consists of a rod which is screwed into a tube close to the end of the

tube is a ridge against which the rod engage. The extractor is pushed over the

partially freed fragment and the rod is screwed, thus gripping the end of the fragment

against the ridge and permitting its removal.

- Frequent radiographic monitoring is mandatory and ample convenience form must be

established so that the desired direction can be maintained toward the target object.

- This technique also requires considerable sacrifice of radicular dentin.

- This technique is more successful in anterior teeth than in posterior teeth.

- Its time consuming and believed to be inferior to ultrasonic technique.

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Removal of Post

Designing a strategy for post and core removal requires a knowledge and

understanding of the cementing medium, the composition and characteristics of the

post, and the composition of the core material.

Several methods are available:

1. Many posts can be loosened and then removed by sonic or ultrasonic (more

effective) vibration transmitted to the post or core material by tips specifically

designed for this purpose. This technique requires intimate contact of the

vibrator tip to the metal of the post. The cement bond may break at the metal-

cement interface or at the dentin-cement interface. Precautions include using

coolant water to avoid heat buildup during vibration and taking care to avoid

fracturing delicate roots.

2. If the post cannot be loosened with the variation technique use an ultrasonic

tip to trough around the post. This removes the cement at the base of the post

and essentially undermines its support and increases the available reciprocal

range of vibration. This procedure is performed without water thus enabling

the clinician to maintain complete visibility throughout the procedure. This

troughing procedure must be performed under high magnification, using the

operating microscope, because the fine tips are easily damaged if they contact

metal. After the post has been undermined, the vibrator tip is used again to

loosen the post.

3. A traumatic removal of the post and core can be performed using the Gonon

post remover. This device contains:

a. A series of incrementally sized hard trephine burs, which cut into

and shape most posts.

b. Tubular tap (cannula) to engage the post.

c. Extractor device that pulls the post out gradually.

After choosing a trephine closest in size to the post, the trephine bur engages the post and

prepares like a tap and die. After threading the post with the trephine, a female-threaded

cannula, called a tubular tap, engages the post and screwed onto the post tightly. This

cannula is also made of hardened drill-rod steel and has a fitting at its extremity that

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allows it to be attached to an extractor device that incrementally expands its jaws and

pulls the post out gradually.

This device can remove even deeply seated posts placed with resin cements. It is

especially useful in removing posts from teeth with ceramic restorations, as the extractor

forces are cushioned and dissipated by a silicone washer.

4- Post fractured deep within the canal can be removed with the ultrasonic method.

Channels can be created down the facial and lingual sides of the post, where the dentin

thickness is greatest. These channels are capable of reducing the retention sufficiently to

loosen the post.

5- A post remover, such as Eggler, may be used provided there is sufficient length of post

or core protruding from the root.

The Eggler consists of a knurled wheel which when turned tightens the jaws on to the

coronal extension of the post.

The flattened knob at the end of the instrument should make simultaneous contact with

the root face on either side of the post (two feet, which are lowered onto the shoulders of

the root face on either side of the post).

- Because of the length of the instrument it is only suitable for use in the anterior part

of the mouth.

The core must be reduced so that the mesial and distal aspects are parallel and don’t

overhang the shoulders of the preparation. Moreover, the buccal and lingual surfaces of

the core must be adjusted so that the jaws can be aligned over them.

- A threaded post is usually simply to remove by gripping the coronal end with pliers and

rotating it in anticlockwise direction.

- When it is not possible to use both methods, the Masserann kit may be employed.

- When access is poor or other methods ineffectual, it is necessary to drill out the post

using a tugsten carbide bur.

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Removal of Canal Obstruction

Obstruction of the canal can be occurred by restorative materials such as amalgam,

composite resin, and glass ionomer.

Some clinician advocates placing and condensing the restorative material on the

furcal floor, at the entry of the canal orifice, or down into the canal. This may be due

to both aids in the retention of the material and to enhance the quality of the coronal

seal.

This complicates retreatment if it should be necessary.

Removal of the restoration material by bur is not recommended. This may cause

several complications such as furcal perforation, lateral root perforation, and

hollowing out and weakening of the root.

Use of the microscope for removing restoration material obstructions from the canal

orifices has eliminated and reduced the procedural risk.

Use specialized ultrasonic tips and high magnification to distinguish the restorative

material from dentin.

Activate the ultrasonic unit with the appropriate tip using a very light touch and

continually brushing away debris, all restorative material can be removed.

Place the tooth access under high magnification to distinguish the restorative material

from dentin.

After identifying the restorative material, activate the ultrasonic unit with the

appropriate tip (with the assistant continually brushing away debris).

Move the tip back and forth or circumferentially around the restorative material,

using a very high touch and keeping the tip continuously moving.

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