ACCIDENTS
1. Inadequately cleaned and shaped root canal system. a. Loss of working length
b. Canal blockage c. Ledging of canal d. Missed canals 2. Instrument separation
3. Deviation from normal canal anatomy a. Zipping
b. Stripping or lateral wall perforation c. Canal transportation
4. Inadequate canal preparation a. Over instrumentation b. Over preparation c. Under preparation 5. Perforations a. Coronal perforations b. Root perforations
i. Cervical canal perforations ii. Mid root perforations iii. Apical perforations c. Post space perforations 6. Obturation related
a. Over obturation b. Under obturation 7. Vertical root fracture 8. Instrument aspiration
Ledging
• Ledge is an internal transportation of the canal which prevents positioning of an instrument to the apex in an otherwise patent canal.
• Caused by forcing uncurved instruments apically short of working length in a curved canal (Fig. 17.1). • Ledges occur on the outer wall of the canal curvature. • Suspected when there is loss of tactile sensation at the tip of the instrument, loose feeling instead of binding at the apex.
• When in doubt a radiograph of the tooth with the instrument in place is taken to provide additional information.
Treatment
• To negotiate a ledge, choose a smaller number file, usually No. 10 or 15.
• Penetrate the file carefully into the canal.
• Once the tip of the file is apical to the ledge, it is moved in and out of the canal utilizing ultra short push-pull movements with emphasis on staying apical to the defect.
• When the file moves freely, it may be turned clock- wise upon withdrawal to rasp, reduce, smooth or eliminate the ledge.
Figs 17.1A and B: (A) Formation of ledge by use of stiff
instrument in curved canal, (B) Correction of ledge; Ledge is bypassed by making a small bend at tip of instrument. Bent instrument is passed along canal wall to locate original canal
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When the ledge can be predictably bypassed, same procedure is repeated with larger instruments.
HOW CAN YOU AVOID INSTRUMENT SEPARATION?
Any time during the cleaning and shaping of root canal file, reamer, broach or Gates Glidden may break espe- cially while working in curved, narrow or tortuous canals.
Certain factors affect the instrument separation and their removal, for example, cross-sectional diameter, curvature and length of the canal, location of the separated instrument and type of the broken material, i.e. whether stainless steel or NiTi.
Prevention
1. Instead of using carbon steel, use stainless steel files. 2. Use smaller number of instruments only once. 3. Examine each instrument before placing it into the
canal.
4. Always use the instruments in sequential order. 5. Never force the instrument into the canal.
6. Canals should be copiously irrigated during cleaning and shaping procedure.
7. Never use instruments in dry canals.
8. Always clean the instrument before placing it into the canal. Debris collected between the flutes retard the cutting efficiency and increase the frictional torque between the instrument and canal wall.
9. Don’t give excessive rotation to instrument while working with it.
WHAT IS CANAL TRANSPORTATION?
“Apical canal transportation is moving the position of canal’s normal anatomic foramen to a new location on external root surface” (Figs 17.2A to C).
Canal transportations can be classified into three types, viz. Type I, II and III.
Type I: It is minor movement of physiologic foramen. Type II: Apical transportations of Type II show moderate
movement of the physiologic foramen to a new location. Such cases compromise the prognosis and are difficult to treat.
Type III: Apical transportation of Type III shows severe
movement of physiological foramen. In such type prognosis is poorest when compared to Type I and Type II.
WHAT IS INADEQUATE CANAL PREPARATION?
Over Instrumentation
Excessive instrumentation beyond the apical constriction violates the periodontal ligament and alveolar bone. Loss of apical constriction creates an open apex with an increased risk of overfilling, lack of an adequate apical seal and pain and discomfort for the patient.
Prevention
Over instrumentation beyond apical constriction can be prevented by:
1. Using good radiographic techniques.
2. Accurately determining the apical constriction of the root canal.
3. Maintaining all instruments within the confines of the canal system.
4. Occlusal alterations before determination of the working length.
5. Intermittent radiographic confirmation of the working length.
Overpreparation
Overpreparation is excessive removal of tooth structure in mesiodistal and buccolingual direction. During biomechanical preparation of the canal, size of apical
Figs 17.2A to C: Type I, II and III canal transportation (A) Minor
movement of apical foramen (Type I), (B) Moderate movement of apical foramen (Type II), (C) Severe movement of apical foramen (Type III)
preparation should correspond to size, shape and curvature of the root.
Adherence to the guidelines for the recommended range of size termination for each type of root is mandatory, with modification made as necessary.
Underpreparation
Underpreparation is the failure to remove pulp tissue, dentinal debris and microorganisms from the root canal system.
Inadequate preparation of the canal system can be prevented in the following ways:
1. Copious use of irrigants to dissolve tissues and debris. 2. Thorough cleaning and shaping of the canal system. 3. Establishing the working length up to apical
constriction.
4. Recapitulation during instrumentation.
PERFORATIONS
Perforation is defined as “the mechanical or pathological communication between the root canal system and the external tooth surface”.
1. Access cavity perforation can occur during access cavity preparation (Fig. 17.3).
2. Root canal perforations can occur at three levels: a. Cervical canal perforations: They commonly
occur while locating the canal orifices and flaring of the coronal third of the root canals.
b. Mid root perforations: Usually, it is caused by
over-instrumentation and over-preparation of the thin wall of root or concave side of the curved canals.
c. Apical root perforations: Apical root perforations
occur when instrument goes into periradicular tissue, i.e. beyond the confines of the root canal.
Occurrence of a perforation can be recognized by:
1. Placing an instrument into the opening and taking a radiograph.
2. Using paper point.
3. Sudden appearance of bleeding.
Repair of the Perforation
Treatment of the endodontics perforation depends on recognition of the condition, location, size, level of the perforation, timing of therapeutic intervention and clinician’s skill and experience.
Material Used for Perforation Repair
An Ideal Material for Perforation Repair should • Be nontoxic
• Be easy to handle • Be radiopaque
• Be dimensionally stable
• Be well tolerated by periradicular tissue • Not to be affected by moisture.
Some of the most investigated materials for perforation repair include amalgam, calcium hydroxide, IRM, Super EBA, gutta-percha, MTA, other materials tried for repair include dentin chips, hydroxyapatite, glass ionomer cements and plaster of paris.
Management of the Coronal Third Perforations
Here the materials used for perforation repair could be composites, amalgam, glass ionomer cements and white MTA.
Management of Perforations in Mid Root Level
If the defect is small and hemostasis can be achieved, perforation can be sealed and repaired during three dimensional obturation of the root canal. But in case the perforation defect is large and moisture control is difficult, then one should prepare the canal before going for perforation repair.
Fig. 17.3: Perforation caused during access
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Management of Perforations in Apical Third of the Root Canal
These types of perforations can be repaired both surgically as well as non-surgically.
Though various materials have been tried for perforation repair but nowadays MTA has shown to provide promising results.
Technique
• Dry the canal system with paper points and isolate the perforation site.
• Prepare the MTA material according to manu- facturer’s instructions.
• Using the carrier provided, dispense the material into perforation site. Condense the material using pluggers or paper points.
• While placing MTA, instrument is placed into the canal to maintain its patency and moved up and down in short strokes till the MTA sets.
• In next appointment, one sees the hard set MTA against which obturation can be done (Fig. 17.4).
Fig. 17.4: Use of MTA for repair of perforation
Perforations can be avoided by:
1. Evaluation of the anatomy of the tooth before starting the endodontic therapy.
2. Using the smaller, flexible files for curved canals. 3. Not skipping the filling sizes.
4. Recapitulation with smaller files between sizes. 5. Confirming the working length and maintaining the
instruments with in the confines of working length.
VERTICAL ROOT FRACTURE
Vertical root fracture can occur at any phase of root canal treatment that is during biochemical preparation, obturation or during post-placement.
Clinical Features
• Sudden crunching sound accompanied by pain is the pathognomic of the root fracture.
• The fracture begins along the canal wall and grows outwards to the root surface.
• The susceptibility of root fracture increases by excessive dentin removal during canal preparation or post space preparation. Also the excessive condensation forces during compaction of gutta- percha while obturation increases the frequency of root fractures.
• Radiographically vertical root fracture may vary from no significant changes to extensive resorption patterns.
Treatment of vertical root fracture involves extraction in
most of the cases. In multirooted teeth root resection or hemi-section can be tried.
Prevention
• Avoid over preparation of the canal.
• Use less tapered and more flexible compacting instruments to control condensation forces while obturation.