Procedural Accidents in Root Canal Treatment

By: Dr. Ammar Khaled (BDS)International University of Africa - Sudan –General Secretary of (SDSA)Member of Sudanese dental association Dentist intern at KSMC E-mail: drammar905@hotmail.com

Root Canal Treatment

• Like other complex of dentistry, an operator may encounter unwanted or unforeseen circumstances during root canal therapy that can affect the prognosis. These mishaps are collectively termed procedural accidents.

When an accident occurs during root canal treatment, the patient should be informed about:

(1) the incident.(2) procedures necessary for correction,(3)alternative treatment modalities.(4) the effect of this accident on prognosis.

In addition, the practitioner who knows his or her limitations will recognize

potentially difficult cases and will refer the patient to an endodontist.

Classification of Procedural Accidents

Accidents During Access PreparationAccidents During Cleaning and Shaping

Accidents During Obturation

ACCIDENTS DURING POST SPACE PREPARATION

Classification of Procedural Accidents

Accidents During Access Preparation• Perforations During Access Preparation• Causes• Prevention• Recognition and Treatment• PrognosisAccidents During Cleaning and Shaping• Ledge formation• Cervical canal perforations• Midroot perforations• Apical perforations• Separated instruments and foreign objects• Canal blockage

Accidents During Obturation•Underfilling•Overfilling•Vertical Root FractureAccidents During Post Space Preparation•I ndicators•Treatment and Prognosis

Accidents During Access Preparation

Perforations During AccessPreparation

The prime objective of an access cavity is to provide an unobstructed or straight-line pathway to the apical foramen.

Accidents such as excess removal of tooth structure or perforation may occur during attempts to locate canals.

Failure to achieve straight-line access is often the main etiologic factor for other types of intracanal accidents.

Perforations must be recognized early to avoid subsequent damage to the periodontal tissues with intracanal instruments and irrigants.

Perforations

There are two types:

1. Lateral root perforation 2. Furcation perforation

Causes

1. Failure to direct the bur parallel to the long axis of the tooth.

2. Searching for canals through an underprepared access cavity.

3. Access through a small or flattened (disk-like) pulp chamber in a multirooted tooth.

4. Access through a cast crown often is not aligned in the long axis of the tooth.

Disk-like pulp chamber (arrow)

Prevention

Clinical examination1. Thorough knowledge of tooth morphology and outlines of

the access cavities .2. Identification of tooth angulation according to the adjacent

teeth.3. Proper reading of the preoperative (diagnostic) radiograph

to get information about the size and extent of the pulp chamber and internal changes (calcification or resorption).

4. Radiograph from different angles .

Bur held alongside radiograph to estimate the depthof penetration

Operative procedures1. Access without rubber dam or using “split technique” is

preferred in specific cases 2. Use of fiberoptic light and magnifiers3. Removal of restorations when possible

Split dam technique

Recognition

1. Sudden pain2. Sudden hemorrhage 3. Radiograph4. Apex locator 5. Taste of irrigant during irrigation

Treatment

Lateral root perforationA- Perforation at or above the height of crestal bone

Treatment: restorative treatment

Supracrestal perforation repair

B- Perforation below the height of crestal bone in the coronal third of the root

The treatment goal is to position the apical portion of the defect above crestal bone by orthodontic extrusion or crown lengthening . Internal repair by mineral trioxide aggregate (MTA) is also possible .

Furcation perforation A- Direct perforation Treatment: immediate sealing using the suitable restorative material (MTA)

Furcation repair using mineral trioxide aggregate (MTA)

B- Stripping perforation - Usually results from excessive flaring with files or drills

(Gates Glidden)- Treatment: non-surgical treatment by immediate sealing using MTA surgical treatment: hemisection, bicuspidization, and root

amputation

Repair of stripping perforation (arrow)

1. The site of the perforation must be found, 2. the floor of the preparation cleansed, 3. the bleeding stopped, 4. mineral trioxide aggregate (MTA) applied to the

perforation . 5. Because it takes MTA more than 3 hours to set, it

should be covered with a fast-setting cement. 6. The other canal orifices should be protected by

placing paper points or an instrument in the canals to prevent blockage.

Nonsurgical Treatment

In the event MTA cannot be immediately applied,

A. it is best to stop the bleeding,B. place calcium hydroxide over the “wound,”C. place a good temporary filling, D. set an appointment with the patient, the sooner

the better.E. The perforation area will be dry at the next

appointment; F. MTA can be applied G. treatment continued.

Surgery treatment requires:-1. more complex restorative procedures . 2. more demanding oral hygiene from the patient.‘ Surgical alternatives are hemisection, bicuspidization, root amputation, and intentional replantation. Indicated: 3.when the defect is inaccessible.4.when multiple problems exist, such as a perforation combined with a separated instrument.5. when the prognosis with other surgical procedures is poor .

Surgical Treatment

Dentist and patient must recognize that the prognosis for treatment of surgically altered teeth is guarded because of the increased technical difficulty associated with restorative procedures and demanding oral hygiene requirements.

PROGNOSIS

Factors affecting the long-term prognosis of teeth after perforation repair include:-1. the location of the defect in relation to crestal bone.2. the accessibility for repair.3. the size of the defect.4. the presence or absence of a periodontal communication to the

defect.5. the time between perforation and repair.6. the sealing ability of restorative material.7. subjective factors such as:-

I. the technical competence of the dentist.II. The attitude and oral hygiene of the patient

• Treatment of the wrong tooth can be so easily prevented. One should make sure through testing, examining, and radiography that one has confirmed which tooth requires treatment

• Open the access cavity before applying the rubber dam

Treatment of the Wrong Tooth

• Porcelain crowns are the most susceptible to chipping and fracture.

• When one is present, use a water-cooled, smooth diamond point and do not force the bur, let it cut its own way .

• Also, do not place a rubber dam clamp on the gingiva of any porcelain or

porcelain-faced crown

Damage to an Existing Restoration

• Additional canals in the mesial roots of maxillary molars and the distal roots of mandibular molars are the most frequently missed.

• Second canals in lower incisors, and second canals in lower premolars, as well as third canals in upper premolars are also missed.

• One must be prepare adequate occlusal access.

Missed Canals

Accidents During Cleaning and Shapaing

Ledge Formation

Definition a ledge has been created when the working length can

not longer be negotiated and the original patency of the canal is lost.

Causes

1. inadequate straight-line access into the canal.2. inadequate irrigation or lubrication.3. excessive enlargement of a curved canal with

files.4. packing debris in the apical portion of the

canal.

Prevention

Preoperative evaluation1. Curvature2. Length

Technical procedures:

Straight line access. Accurate working length measurement . Frequent recapitulation and irrigation. Use of lubricant like RC-PREP. Use of flexible Ni-Ti files in curved canals . Each file must be used until it is loose before a larger size is

used . Avoid application of severe forces during instrumentation .

Management of ledge

• A ledge is difficult to correct. • An initial attempt should be made to bypass the

ledge with a No. 10 steel file to regain working length.

• The file tip (2 to 3 mm) is sharply bent and worked in the canal in the direction of the canal curvature.

• Lubricants are helpful.• If the original canal is located, the file is then

worked with a reaming motion and occasionally an up-and-down movement to maintain the space and remove debris

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

Prognosis

The failure depends on the amount of debris left in the uninstrumented and unfilled portion of the canal.

The amount depends on when ledge formation occurred during instrumentation.

In general, short and cleaned apical ledges have good prognoses.

Future appearance of clinical symptoms or radiographic evidence of failure may require referral for apical surgery or retreatment.

Root Perforations

Apical perforation Types A. Apical perforation through the apical foramen

(overinstrumentation)

B- Apical perforation through the body of the root in the apical third

Ledge apical perforation

Etiology a. Apical perforation through the apical foramen:- It is caused by instrumentation of the canal beyond the

apical constriction (incorrect working length) b. Apical perforation through the body of the root in the

apical third:- It is caused as a result of operator insistence to manage a

ledge in the apical third (especially in curved canals)

Indicators

1. Hemorrhage in the canal 2. Bleeding at the tip of paper point 3. Sudden pain4. Sudden loss of the apical stop5. Radiograph

Bleeding at the tip of paper point

Prevention

To prevent apical perforation, proper working lengths must be established and maintained throughout the procedure.

Treatment - In case of overinstrumentation, corrective treatment includes

reestablishing tooth length short of the original length and then enlarging the canal, with larger instruments, to that length.

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

- In case of apical perforation through the body of the root in the

apical third, try to negotiate the original canal .

- One is now dealing with two foramina: one natural, the other iatral. Obturation of both of these foramina and of the main body of the canal requires the vertical compacting techniques with heat-softened gutta-percha

Non-surgical repair of apical perforation through the body of the root

Prognosis

• Success of treatment depends primarily on the size and shape of the defect. An open apex or reverse funnel is difficult to seal and also allows extrusion of the filling materials.

Lateral (midroot) perforations

Etiology- There are two types of midroot perforations:a. Direct perforation as a result of pressure and force applied

to a file during negotiation of ledged canals, or through post space preparation using cutting-end bur

b. Stripping perforation is a lateral perforation caused by overinstrumentation using files or drills like Gates-Glidden through a thin wall in the root and is most likely to happen on the inside (inner) wall of a curved canal, such as the distal (inner) wall of the mesial roots in mandibular first molars

Stripping perforation

Danger zone and safety zone

Indicators

- They are similar to those of apical perforation

The area of hemorrhage on the point indicates the area where thestrip has occurred.

Prevention

To avoid these perforations some factors should be considered:

1. degree of canal curvature and size .2. inflexibility of the larger files, especially

stainless steel files.

Treatment - The main goal is to instrument and obturate the entire root

canal system - Perforation repair surgically or non-surgically using suitable

restorative material (MTA)

Repair of stripping perforation using MTA

Prognosis

It depends on several factors:- Remaining amount of undebrided and unobturated canal.- Perforation size.- Surgical accessibility.• Obturation is difficult because of lack of a stop , and gutta-percha tends

to be extruded during condensation. • Teeth with perforations close to the apex after complete or partial

débridement of the canal have a better prognosis than those with perforations that occur earlier.

• In addition to the length of uncleaned and unfilled portions of the canal, size and surgical accessibility of perforations are important.

• In general, small perforations are easier to seal than large ones.

Coronal root perforation

Etiology - Direct perforation happens during access preparation while

the operator attempts to locate the canals- Stripping perforation happens during flaring procedures by

files or Gates-Glidden

Prevention- It is similar to what described earlier in the prevention of

perforation during access preparation - Careful and conservative flaring, especially during using

Gates-Glidden, is also recommended

Treatment & Prognosis

• Repair of a stripping perforation in the coronal third of the root has the poorest long-term prognosis of any type of perforation.

• The defect is usually inaccessible for adequate repair. An attempt should be made to seal the defect internally, even though the prognosis is guarded. Patency of the canal system must be maintained during the repair process.

MTA is a promising material to repair almost all types of perforations

Separated Instruments

Etiology

- Limited flexibility - Over use- Excessive forced applied to files - Improper use

Notice: any instrument may break either steel, NiTi, hand or rotary

Recognition

- Removal of shortened file from the canal- Loss of canal patency - Radiograph is essential for confirmation.

• limitations of files is critical.• Continual lubrication with either irrigating solution or

lubricants is required.• Each instrument is examined before use ( flutes distortion). • Small files must be replaced often. • To minimize binding, each file size is worked in the canal until

it is very loose before the next file size is used.• Nickel-titanium files usually do not show visual signs of fatigue

similar to the “untwisting” of steel files, they should be discarded before visual signs of untwisting are seen .

Prevention

Signs of instrument distortion (arrows)

Treatment

- There are three approaches:1. Attempt to remove the instrument (using small file to

bypass the instrument then retrieve it, using ultrasonic tips, or using especially designed pliers)

Pliers

2- attempt to bypass it.3- prepare and obturate to the segment coronal to the

instrument. The operator should attempt to bypass the separated

instrument. After bypassing the separated instrument, ultrasonic files broaches, or Hedstrom files are used to remove the segment.

If removal of the separated piece is unsuccessful, then the canal is cleaned, shaped, and obturated to its new working length.

If the instrument cannot be bypassed, preparation and obturation should be performed to the coronal level of the fragment.

A, Arrow pointing to a separated instrument in the mesiolingual canal B, Postobturation film with an arrow identifying “tunneling” that was created with an ultrasonic instrument to remove the separated instrument

Removal of broken instrument extended beyond the apex (arrow)

Prognosis

It depends on how much undbrided and unobturated canal remains.

The prognosis is best when separation of a large instrument occurs in the later stages of preparation close to the working length.

Prognosis is poorer for teeth with undébrided canals in which a small instrument is separated short of the apex or beyond the apical foramen early in preparation.

For medical-legal reasons, the patient must be informed of an instrument separation.

If the patient remains symptomatic or there is a subsequent failure, the tooth can be treated surgically.

Instrument Aspiration or IngestionPrevention - Rubber dam

Indicators - Instrument disappearance followed by severe coughing or

gagging by the patient - Radiograph

Treatment - When the lost instrument is readily accessible, high volume

suction, hemostat, or cotton pliers may help to retrieve the instrument. Otherwise, referral to a medical service is required and major surgical intervention may also be required

Swallowed endodontic file ended up in appendix and led to acute appendicitis and appendectomy. Rubber dam would have prevented this tragedy.

Extrusion of Irrigant

• Wedging of a needle in the canal or out of a perforation with forceful expression of irrigant causes penetration of irrigants into the periradicular tissues and inflammation and discomfort for patients.

• Loose placement of irrigation needles and careful irrigation with light pressure or use of a perforated needle precludes forcing the irrigating solution into the periradicular tissues.

• Sudden prolonged and sharp pain during irrigation followed by rapid diffuse swelling (the “sodium hypochlorite accident”) usually indicates penetration of solution into the periradicular tissues.

Severe swelling caused by injecting hydrogen peroxide irrigant into tissues.

A, Hemorrhagic reaction caused by NaOCl accidentB, Healing within few weeks

A B

Treatment

- Because of the potential for spread of infection related to tissue destruction, it is advisable to prescribe antibiotics in addition to analgesics for pain

- Antihistamines can also be helpful- Ice packs applied initially to the area, followed by warm

saline soaks the following day, should be initiated to reduce the swelling

- In more severe cases, hospitalization and surgical intervention with wound débridement, may be necessary

- Patient reassurance

Prognosis

- Generally is favorable - In some cases, the long-term effects of irrigant injection into

the tissues have included paresthesia, scarring, and muscle weakness

Accidents During Obturation

Undefilling

Causes - Natural barrier in the canal.- Ledge.- Insufficient flaring.- Poorly adapted master cone.

Prevention- Confirmatory MAC radiograph .- If displacement of the MAC is suspected, a radiograph is

made before excess gutta-percha removal .

Treatment - Re-treatment

Overfilling

Causes - Overinstrumentation- Open apex- Uncontrolled condensation forces

Prevention - Avoid overinstrumentation.- Prepare apical matrix (seat).- Confirmatory MAC radiograph.- If displacement of the MAC is suspected, a radiograph is

made before excess gutta-percha removal.- In case of wide (open) apex, a solvent customized cone

technique is preferred .

Treatment - In case of endodontic failure, apical surgery may be required

to remove the extruded material

Prognosis - It depends on some factors: quality of the apical seal, amount

and biocompatibility of extruded material, and host response

Usually, slight over extension of GP cone beyond the apex (around 2 mm) doesn’t cause problem and doesn’t need further treatment.

Surgical removal of extended gutta-percha beyond the apex

Gross paste overfilling

Vertical Root Fracture

Causes - Overflaring - Screw post placement- Post cementation - Excessive applied forces during gutta-percha condensation

Prevention- Appropriate (conservative) canal preparation - Balanced applied forces during condensation- Finger spreaders produce less stress than hand fingers during

obturation

Indicators - Sudden sound and pain during obturation - Narrow periodontal pocket or sinus tract stoma - “Halo” radiographic radiolucency - Surgical exploration

Surgical exploration“Halo” radiographic radiolucencyNarrow periodontal pocket

Treatment - Removal of the fractured root in multi-rooted tooth and

extraction of single-rooted tooth

Accidents During Post Space Preparation

Root Perforation

Prevention- Gutta-percha removal using heated pluggers.- Good knowledge of root canal anatomy, location of the root,

and its direction in the alveolus.- Gates-Glidden and Peeso reamer are safe, however, they can

lead to excessive removal of tooth structure and therefore can potentially lead to “stripping” perforation or root fracture.

- High speed burs shouldn’t be used at all in post space preparation

Indicators - Bleeding during preparation- Sinus tract or pocket extended to the post base- Lateral radiographic radiolucency

radiographic radiolucency causedroot perforation during post space preparation

Treatment

- Non-surgical repair if the post can be removed (as stated in management of root perforation)

- Surgical repair if the post cannot be removed and the perforation is accessible

- Otherwise extraction is required

Non-surgical repair using MTA of perforation caused during post space preparation

Prognosis

- It depends on: perforation size, surgical accessibility, and perforation location ( apical perforation has better prognosis than that close to the gingival sulcus)