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The most common procedure accidents during cleaning and shaping of root canal system are:

Ledge formation. Artificial canal creation. Root perforation. Instrument separation. Extrusion of irrigating solution periapically.A. Ledge formation

A ledge has been created when the working length can no longer be negotiated and the original

patency of the canal is lost.

The causes of ledge formation:

1. Inadequate straightline access into the canal.2. Inadequate irrigation or lubrication.3. Excessive enlargement of curved canal with files4. Packing debris in the apical portion of the canal.

Prevention of ledge:

Prevention of ledge begins with examination of the preoperative radiograph for curvatures, length,

and initial size

Sever coronal curvature predisposes the apical canal to ledging. Straight line access to the orifice of

the canal and coronal flaring can be achieved for accessibility to the apical third of the canal. Sever

apical curvatures require a proper sequence of cleaning and shaping procedures to maintain

patency. The canals most prone to ledging are small, curved and long.

An accurate working length measurement is a requirement because cleaning and shaping short of

the ideal length cause ledge formation.

Frequent recapitulation, irrigation and the use of lubricants are mandatory. Flexible files reduce the

chances for ledge formation. A one- eighth to one-fourth reaming motion with the files should be

used in the apical third. Each file must be worked until it is loose before a large size is used.

Management of a ledge

bypass the ledge with a No. 10 steel file to regain working length. The file tip (2 to 3 mm) is sharply

curved and the file tip (2 to 3 mm) is sharply curved and worked in the canal in the direction of the

canal curvature.If the original canal cannot be located by this method, then cleaning and shaping ofthe existing canal space is completed at the new working length.

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B. Artificial canal creationDeviation from the original pathway of the root canal system and creation of an artificial canal

cause ledge. It is initiated by the factors that cause ledge formation.

Management

Negotiating the original canal and prepared. If there is no perforation the canal obturated with a

warm or softened GP. If there is a perforation, the defect should be repaired internally or surgically.

C. Root perforationPerforation is the iatrogenic damage to the root canal wall that results in a connection

With periodontal ligament. Perforation may occur at different levels during cleaning and

shaping. Location of the perforation and the stage of treatment affected prognosis.

a. Apical perforation:Apical perforation occurs through the apical foramen (overinstrumentation) or through the

body of the root (perforated new canal).

The causes of apical perforation

o Instrumentation of the canal beyond the apical constriction.o Incorrect working length or inability to maintain proper working length causes

zipping of the apical foramen.

Prevention

o Proper working lengths must be maintained throughout the procedure.o In curved canals the flexibility of files must be considered.o The working length should be verified with an apex locator after completion of

cleaning and shaping steps to prevent apical perforation because the working

length decrease by 1 to2mm after canal preparation.

Treatment

Establishing a new working length and obturating the canal to its new length.

Placement of MTA as an apical barrier can prevent extrusion of obturation

materials.

b. Lateral (Midroot ) perforationsCauses of lateral perforation

Inability to maintain canal curvature is the major cause of ledge formation.

Negotiation of ledged canal and misdirected pressure and force applied to a file

result in formation of perforation.

Treatment

if attempts to negotiate the apical portion of the apical canal are not achieved thenew working length confined to the root is established the canal is then cleaned

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,shaped, and obturated to the new WL. Low concentration (0.5) of sodium

hypochlorite or saline should be used for irrigation in a perforated canal.

c. Coronal root perforationsCoronal root perforations occur during access preparation as the operator attempt

to locate canal orifices or during flaring procedures with files, Gates-Glidden drills.

The location and size of the perforation during access are important factors in

perforation if the defect is located at or above the height of crestal bone, the

prognosis for perforation repair is favourable (Lemon, 1992). This perforation can

be repaired with amalgam, GIC or composite. Perforation below the crestal bone in

the coronal third of the root have the poorest prognosis. Periodontal pocket forms

with attachment loss extending apically to the depth of the defect.

Repair of stripping perforation in the coronal third of the root has the poorest long-

term prognosis of any type of perforation (Lemon,1992). The defect is usually

inaccessible for adequate repair. Seal the defect internally with MTAPerforation can be avoided by:

1. Using the pulp floor map to locate root canal orifices

2. Gradually working up the series from small files to larger sizes, always

recapitulating with a smaller file between sizes

3. Using an apex locator and radiograph to confirm root canal length

4. Minimizing overuse of Gates-Glidden burs, either too deep or too large, in curved

canals where a strip perforation may occur.

Try and direct the cutting action into the bulkiest wall of dentine; this also helps

straighten the first curvature of the root canal and improves straight-line

access.

5. Using an anticurvature filing technique.

6. Never forcing instruments or jumping sizes

7. Irrigating copiously.

D.Separated instrumentsThe main causes of separation are overuse or excessive force applied to file.

Prevention1. Always progressing through the sizes of files in sequence, and not jumping sizes.

Forcing an instrument will lead to fracture.

2. Irrigation or lubrication is required.3. Each instrument is examined before use. Discarding all damaged files.4. Nickel-titanium files should be used for only a limited number of times and then

discarded.

5. Preflaring of preparations using passive step-back before the use of rotaryinstruments reduces the rate of separation.

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Treatment

There are three approaches:

1. Attempt to remove the instrument.2. Attempt to bypass it.3. Prepare and obturate to the segment.

Extrusion of irrigant

Extrusion of NaOCl into the periapical tissue causes inflammation and discomfort for patients.

Prevention

Loose placement of irrigation needle. Careful irrigation with light pressure. Use of a perforated needle.

Treatment

Treatment is palliative. Analgesic is prescribed and patient is reassured.

References

Torabinejad M. & Walton RE. Endodontics: Principles and Practice.4th

ed. Saunder, 2009.

Gutmann J.L, Dumsha t.C. & Lovdahi P. E. Problem Solving in Endodontics, 4 th ed. Mosby, 2006.