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LITERATURE REVIEW http://dx.doi.org/10.17159/2519-0105/2019/v74no5a6

Errors in root canal preparation:

a review of the literature and
clinical case reports
SADJ June 2019, Vol. 74 No. 5 p246 - p254
PJ van der Vyver1, M Vorster2, F Paleker3, FA de Wet4

SUMMARY INTRODUCTION
Chemo-mechanical preparation and the removal of The goal of root canal shaping procedures is to treat
infected dentine in order to eliminate microorganisms apical periodontitis through the removal of infected den-
and avoid apical periodontitis remain the main objec- tine from root canal walls. Endodontic treatment focuses
tives in endodontic treatment. on eliminating microorganisms by chemo-mechanical
preparation of the root canal.1,2
Mechanical preparation of the root canal system not
only provides the space for obturation but also facilitates Ideal “chemo-mechanical preparation” refers to an ade-
disinfection of the root canal system through the use of quately shaped canal that is sufficiently accessible by
irrigation solutions. disinfecting solutions. Root canal shaping by means of
mechanical preparation not only provides the space for
Iatrogenic preparation errors affect the root canal ana- obturation but also facilitates disinfection by disrupting
tomy and can result in apical canal transportation, the biofilms that adhere to canal surfaces.3
uncentered preparations, ledge formation, or perforations.
These errors are all associated with inferior outcomes of Correct mechanical instrumentation of the root canal
endodontic treatment. should result in a continuously tapered, funnel-shaped
canal that corresponds to the original canal anatomy.
In this paper, the authors will discuss a review of the This objective is often difficult to achieve when a dentist
literature which considers some of these procedural is faced with the complex internal morphology of curved
errors and, using clinical case studies, will illustrate the root canals.4,5 Iatrogenic preparation errors affecting
appropriate clinical management when errors do occur. the root canal anatomy remain a problem in this type of

canal and can result in apical canal transportation, un-

Author affiliations: centered preparations, ledge formation, or perforation.
1. Peet van der Vyver: BChD, PG Dip Dent (Endo), PG Dip Dent Procedural errors that occur during root canal shaping
(Aesthet Dent), MSc, PhD (Pret), Department of Odontology, are associated with inferior outcomes.4,5
School of Dentistry, University of Pretoria, Pretoria, South Africa
and Private Practice, Sandton, South Africa.
ORCID Number 000- 0003 -1951- 6042 1. Ledge formation
2. Martin Vorster: BChD (Pret), PG Dip Dent (Endo), MSc (Pret),
Department of Odontology, School of Dentistry, University of
A ledge is an iatrogenically created irregularity or platform
Pretoria, Pretoria, South Africa.
ORCID Number 0000-0003-4470-1530 on the inside of the greater curvature of the canal. It may
3. Farzana Paleker: BChD (Stell), Dip Odont (Endo), MSc (Pret), form in the original canal path, create a new false canal,
Department of Odontology, School of Dentistry, University of and/or block the apical part of the root canal.6 A ledge that
Pretoria, Pretoria, South Africa.
ORCID Number 0000-0002-5446-309X cannot be bypassed impedes instruments and, in some
4. Francois A de Wet: BChD, MSc, DSc (Pret), Department of cases, prevents irrigants from entering the apical portion
Odontology, School of Dentistry, University of Pretoria, Pretoria, of the canal.
South Africa.
ORCID Number 0000-0003-4279-3902
Corresponding author: PJ van der Vyver This occurrence results in inadequate instrumentation
Tel: +27 (0)11 781 1020 Email: peetv@iafrica.com and incomplete obturation.4,5 Ledges have been associa-
Author contributions:
1. Peet van der Vyver: Responsible for some of the scientific writing
ted with persistent peri-apical infection after endodontic
and planning of the article. Provided most of the clinical cases treatment.7
reported in the article.
2. Martin Vorster: Responsible for some of the scientific writing,
contributed to the writing of the abstract, literature review as
Typically, ledge formation occurs when stiff files with
well as concluding remarks and was also involved in the editing sharp inflexible cutting tips are used in a rotational motion
and proofreading of the article as well as editing and verifying in curved root canals. This common procedural error
of references. usually occurs on the outer side of the curvature when
3. Farzana Paleker: Responsible for some of the scientific writing,
final layout of the article and collecting cases that were not instruments are used aggressively, with exaggerated cut-
provided by Prof P vd Vyver. ting during root canal instrumentation.6 Ledges are formed
4. Francois A de Wet: Responsible for some of the scientific writing either within the original canal path or through creating a
and for proofreading of the article.
new false canal (Figure 1).
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LITERATURE REVIEW <
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Various factors have been as- •• Creating an apical blockage by inadvertently packing
sociated with ledge formation; debris in the apical portion of the canal during instru-
these include tooth and canal mentation.14
location, canal curvature, instru-
ment design, alloy properties, Lateral perforations might occur when the ledge is
instrumentation techniques, and created during initial instrumentation or as a strip
operator experience. Ledge for- perforation on the concave side of the curvature of the
mation was found to be the most root as the canal is straightened out (a perforation that
frequently encountered error in a occurs along the inner wall of a curved root canal).7
study among patients who had
received root canal treatment
Case report 1
performed by undergraduate stu-
dents who used hand-operated The patient, a 49 year old female presented with
stainless steel files in a step- percussion sensitivity on her mandibular, right second
back technique.8 molar. A peri-apical radiograph revealed that all the
root canals were prepared short of working length, and
Figure 1. Schematic representation of a ledge formed within the original showed evidence of peri-apical pathology around the
canal path as a result of skipping instrument sizes or erroneous working mesial roots (Figure 2).
length estimation.

Another study on ledge formation in maxillary and The tooth was anaesthetised and isolated before the
mandibular first and second molars treated endodontically previous obturation material was removed from the
by undergraduate students showed that canal curvature root canals using Endosolv E (Septodont) and a size 15
influenced ledge formation more than did the other Hedstrom files. A size 10 K-File was introduced into
variables examined.9 As canal curvature increased, so did the distal and mesio-buccal root canals, and it was
the number of ledges. Canal curvature in this study was possible to negotiate them to full working length.
measured by using Schneider’s technique.10 Canals with The same protocol was followed in the mesio-buc-
a curvature of less than 10° were rarely ledged, whereas cal root canal but it was impossible to negotiate the
canals with a curvature of more than 20° were ledged canal further. The tip of the instrument was hitting
over 56% of the time.11 The study also showed that canal against a solid wall of dentin (Figure 3). A ledge for-
location influences the incidence of ledging. The mesio- mation in the canal was confirmed at the beginning of
buccal and the mesiolingual canals were more fre- the root curvature.
quently ledged than were the distal, lingual, or distobuc-
cal canals.9 Similar results were also reported in a study
which demonstrated that the frequency of occurrence
of ledged root canals was significantly greater in molars
compared with that seen in anterior teeth.12

According to Lambrianidis (2009) the most common

causes of ledge formation are: 6
•• Incorrect or insufficient access cavity preparation that
does not allow adequate and unobstructed access to
the apical constriction;
•• An incorrect assessment of the root canal direction;
•• Incorrect length determination of the root canal;
•• Use in a curved canal of stainless steel instruments that
are not pre-curved;
•• Use of over-curved stiff instruments;
Fig. 2 Fig. 3
•• An attempt to retrieve or by-pass a fractured instrument
or a foreign object; Figure 2. Preoperative periapical radiograph of a mandibular right second
•• Removing obturation materials during endodontic molar with a substandard root canal treatment outcome. Note the periapical
pathology around the apical part of the mesial root.
retreatment;
•• An attempt to negotiate a calcified or a very narrow root Figure 3. A size 10 K-File was introduced into the mesio-buccal canal but
it was impossible to negotiate the canal further as the tip of the instrument
canal; and was hitting against a solid wall of dentin. A ledge formation in the canal was
•• During preparation of space for a post after completion confirmed at the start of the root curvature.
of root canal treatment.
A size 08 C+ -File, 21 mm long, with a distinct curve
Several authors have highlighted additional causes: in the apical 2-3 mm of the file was selected in the
•• Forcing and driving the instrument into the canal;7 attempt to bypass the ledge. The directional marker on
•• Using a non-curved stainless steel instrument that is the rubber stop was positioned to indicate the direction
too large for a curved canal;11 of the curve placed on the tip of the file (Figure 4).
•• Failing to use the instruments in sequential order;11
•• Rotating files excessively at working length;13 The canal was filled with 6% sodium hypochlorite
•• Inadequate irrigation and/or lubrication during instru- (Chlor-Xtra, Vista Dental). The file was introduced into
mentation;14 the canal, ensuring that the curved tip was directed
•• Relying too heavily on chelating agents;13 and towards the wall opposite the ledge. A slight rotation
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LITERATURE REVIEW

motion combined with a light “picking motion” was used

to try to discover the original canal entrance. After seve-
ral attempts, re-orientating the file in different posi-
tions, the pre-curved file tip advanced for about 0.5 mm
(Figure 5).

A B

Figure 7. Schematic representation of (A) potential directions for trans-

portation in particular zones (as indicated by arrows) when the elastic
memory of larger files tend to straighten out the root canal system; (B)
the end result of greater removal of dentine (red colour in the illustration) from
the external zone of the curve in the apical one third and from the internal
zone of the curve in the middle one third of the root canal system (Adapted
Fig. 4 Fig. 5 from Berutti and Castellucci19).

Figure 4. A size 08 C+-File (21 mm) with a distinct curve in the apical 2-3 mm
of the file was selected in the attempt to bypass the ledge.

Figure 5. A size 08 C+- File was used in a slight rotation motion combined
with a light “picking motion” to discover the original canal entrance.

Figure 6. Postoperative periapical ra-

diograph immediately after obturation.

The file was slightly retracted,

and advanced again. This
procedure was repeated
and the file progressively
advanced further down the A B
canal for another 2.5 mm.
Figure 8. Schematic representation of (A) cross section of a root canal
The 08 C+-File, with the tip Fig. 6 system at the level of the apical foramen (apical foramen in light blue); (B)
placed apically to the ledge, appearance of a teardrop foramen after canal preparation with a straight,
was used with a filing motion combined with push- non-pre-curved instrument. The original foramen is light blue and the
additional dentine removed by the non-pre-curved instrument is brown in
pull motions, pushing the file against the canal wall in
colour (Adapted from Berutti and Castellucci19).
the endeavour to reduce the internal canal irregularity.

The C+-File was removed and the canal was irrigated

before a pre-curved size 08 K-File was negotiated to
full working length and patency. The working length was
confirmed radiographically after using an electronic apex
locator (ProPex Pixi, Dentsply Sirona).
A B
Figure 6 shows the final result after glide path preparation
with a ProGlider (Dentsply Sirona), canal preparation with
a Primary WaveOne Gold (Dentsply Sirona) instrument Figure 9. A representative Micro Computed Tomography example of a
curved mesio-buccal root canal system, 1mm from the apical foramen.
and canal obturation with gutta-percha and Pulp Canal The canal was prepared with a Primary WaveOne Gold instrument (25/08)
Sealer (SybronEndo, Orange, California) using warm ver- (Dentsply Sirona). No canal transportation at the of the root canal occurred
tical condensation technique. (Red: pre-instrumentation area, Green: effect of canal preparation with shap-
ing instrument).

2. Canal transportation Figure 10. A representative Micro Computed Tomography example of a

curved mesio-buccal root canal system, 1mm from the apical foramen.
The canal was prepared with the OneShape instrument (25/06)
Canal transportation is a sustained deviation from the
(Micro-Mega). Canal transportation of the root canal is shown
original axis of the canal during root canal instrumen- (Red: pre-instrumentation area, Green: effect of canal preparation with
tation (Figures 7a and 7b). shaping instrument).
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Apical canal transportation is described as the removal Depending on the location, a perforation cannot easily
of canal wall structure on the outside curve in the apical be sealed and/or bypassed, which results in an inade-
half of the canal due to the tendency of files to recover quately prepared and sealed root canal.4,5
to their original linear shape during canal preparation.15
A perforation that occurs along the inner wall of a
As a result, the main axis of the root canal is transpor- curved root canal is referred to as a “strip perforation”
ted away from its original axis. Other terms for canal (Figure 15c).
transportation include “canal straightening” and “zipping”.4

Stiff endodontic instruments, particularly large-sized

stainless steel files, tend to exert elevated lateral forces
in curved canals and can result in straightening, espe-
cially in the middle and apical thirds.16

This straightening or transportation can create problems

with canal cleaning, obturation and, ultimately, healing.4,5
Apical canal transportation can cause enlargement of
the apical foramen (Figures 8a and 8b), which compro-
mises the apical seal.17 Lack of an apical stop might
result in extrusion of irrigants and/or obturation materials
and cause irritation to the peri-radicular tissues.4,18 Fig. 11 Fig. 12

Figures 9 and 10 illustrate micro-computed tomographic Figure 11. A peri-apical radiograph of a maxillary left first premolar, with
extensive decay under a previously placed porcelain veneered crown.
images of two curved mesio-buccal root canal systems
of extracted, maxillary first molar teeth at a level 1mm Figure 12. A peri-apical length determination radiograph Note the sharp
apical curvature in the last 3 mm of the root canal system, indicated by
from the apical foramen. The example in Figure 9 shows the bending of the size 10 K-File.
minimal canal transportation after root canal preparation
compared with that in Figure 10 which clearly shows an
excessive amount of canal transportation.

Case report 2
The patient, a 54 year old female, presented with
irreversible pulpitis on her maxillary left first premolar,
caused by extensive decay under a previously placed
porcelain veneered crown (Figure 11). After removal
of the defective crown and decay a core build-up was
done prior to root canal treatment. A size 10 K-File
was negotiated to full working length and confirmed
radiographically (Figure 12). Note the sharp apical Fig. 13 Fig. 14
curvature in the last 3 mm of the root canal system.
Figure 13. Cone-fit peri-apical radiograph. Note the loss of the apical cur-
The root canal system was prepared with the Pro- vature of the root canal system.
Taper Universal (Dentsply Sirona) system. Incorrect Figure 14. A post-operative peri-apical radiograph showing apical root
use of the X3 file (30/09) resulted in apical transpor- canal transportation resulting in loss of the original apical curvature and
tation. This was visible on the peri-apical radiograph lack of an apical stop, resulting in extrusion of the obturation material.

taken to confirm the cone-fit of the gutta-percha point

(Figure 13). After root canal obturation it became more
evident that an excessive amount of the root
canal wall structure on the outside curve in the apical
part of the canal was removed by the rotary file.
This resulted in the loss of the original apical curva-
ture, lack of an apical stop and subsequent extrusion
of the obturation material (Figure 14).

3. Perforation
A direct perforation is a channel or communica-
tion between the root canal space and surrounding
cementum (Figures 15a and 15b). Such a perforation
can result in the destruction of cementum and the A B C
irritation and/or infection of the periodontal ligament in the
surrounding area. As with ledging, perforation of curved Figure 15. (A) Schematic representation of a direct perforation; (B) clinical
example of a direct perforation (arrow) of the two mesial root canals of a
canals is associated with stiff instruments with sharp mandibular right first molar; (C) schematic representation of a strip perfora-
cutting tips used in a rotational motion. tion (arrow).
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LITERATURE REVIEW

This results from over-preparation and straightening After canal irrigation, the perforation was repaired with
along the concavity and is of particular concern in ProRoot MTA (Dentsply Sirona) before conventional canal
the mesiobuccal roots of maxillary molars and mesial obturation (Figure 18).
roots of mandibular first molars.20,21 The root walls
facing the furcal aspect of roots are often extremely The access cavity was restored with composite resin and
thin and are therefore termed “the danger zone”.22 placement of a fibre post. Figure 19 shows a four-year
follow up radiograph with some evidence of resorption of
the extruded ProRoot MTA material.
Case report 3
The patient, a 37 year old female presented with irrevers-
4. Uncentered preparations
ible pulpitis on her maxillary left first second premolar.
The tooth had been previously restored with a large The ability of an instrument to stay centered in the
composite resin restoration and two retention pins. canal can be measured by the mean centering ratio.23
A preoperative peri-apical radiograph (Figure 16) and a The importance of maintaining preparations that are
length determination radiograph (Figure 17) revealed and centered (Figure 20a) and correspond to the original
confirmed a challenging “S” shaped or bayonet-shaped canal anatomy has been pointed out by Berutti et al.24
root canal configuration. A study by Pasqualini et al. examined rotary glide path
files and concluded that files with a high root canal
Due to the lack of proper glide path preparation and centering ability resulted in fewer modifications of the
management in this case, the operator was faced with a canal curvature and therefore fewer canal aberrations.25
rotary file fracture in the apical part of the root canal and Several studies have shown that more flexible instru-
a strip perforation at the point of maximum curvature on ments produce more centered preparations.26,27 Flexibility
the distal aspect of the root. It was impossible to even can be defined as the elastic bending of an endodontic
attempt the retrieval of the fractured instrument and it instrument when subject to a load applied at its extre-
was left in situ. mity in the direction that is perpendicular to its long axis.28

Fig. 16

Figure 16. A preoperative peri-apical radiograph a maxillary left second

Fig. 17
premolar, restored with a large composite resin restoration and two retention
pins. Note the “S” shaped or bayonet-shaped root canal configuration.
Figure 17. A peri-apical length determination radiograph confirmed the “S”
shaped or bayonet-shaped root canal configuration.

Fig. 18

Figure 18. Rotary file fracture in the apical part of the root canal and a strip
perforation at the point of maximum curvature on the distal aspect of the root Fig. 19
that was repaired with ProRoot MTA (Dentsply Sirona) before conventional
canal obturation, placement of a fibre post and composite to close the Figure 19. A four year follow up radiograph with some evidence of resorp-
access cavity. tion of the extruded Proroot MTA material.
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Flexibility may influence an instrument’s ability to properly This type of fracture has been associated with the
shape curved root canals. Inflexible files, on the other hand, application of excessive apical force during instrumenta-
may cause a deviation from the original canal axis, which tion. Fracture resulting from flexural fatigue occurs when
can result in canal straightening, transportation, thinning an instrument that has already been weakened by metal
of the canal wall and perforation (Figure 20A and 20B). fatigue is placed under stress.

The instrument does not bind to the canal wall but

rotates freely until the fracture occurs at the point of
maximum flexure.33 This type of failure is believed to be
an important factor in the fracture of nickel-titanium
(NiTi) rotary instruments in clinical usage, and might
result from their use in curved canals.30 Various factors
have been associated with the fracture of rotary
instruments: rotational speed and angle and radius
of curvature,30 instrument design and instrumentation
technique35, torque36, and operator experience.37
A B

Figure 20. Representative micro-computed tomography examples of mesio-

Case report 4
buccal root canal systems of extracted mandibular first molars at the level of
7 mm from from the apical foramen:
The patient, a 21 year old male presented with a frac-
(A) a centred canal preparation; tured rotary file in his maxillary left upper central incisor.
(B) a non-centred canal preparation that can lead to canal straightening, The fragment (14 mm long) was located approximately
transportation, thinning of the canal wall and perforation (Red: original
canal, Green: canal after preparation with rotary nickel-titanium instrument).
4 mm apically from the cemento-enamel junction at the
coronal aspect extending apically to about 5 mm from
the apical foramen (Figure 22). Under 15x microscope
5. Instrument separation magnification, the fractured instrument was clearly visible
in the canal (Figure 23).
A common problem with the use of rotary files is the po-
tential risk of separation or breakage within the canals.29 It was decided to use the Terauchi File Retrieval Kit
In most clinical situations, the breakage of the instrument (TFRFK) (Dental Cadre) to assist in removal of the fractured
occurs in the apical third of the canal and the remaining instrument. The 12 o’clock Micro-spoon ultrasonic tip
portion is often difficult or impossible to remove.30,31 (Figure 24) was used to penetrate through between
Attempts at removal may even result in other procedural
errors like perforation. The fragment that is left behind
blocks the root canal system and results in inadequate
cleaning, shaping and sealing (Figure 21A and 21B).32

Fracture of rotary instruments can occur because of tor-

sional overload33, or fatigue through flexure.34 The torsio-
nal fracture occurs when the tip or any other part of
the instrument binds to the canal walls while the hand
piece keeps turning. When this binding occurs and the
elastic limit of the metal is exceeded, fracture of the
instrument is inevitable.
Fig. 24

Figure 24.
The 12 o’clock Micro-
spoon ultrasonic tip.
Fig. 22

Figure 22.
Peri-apical radiograph of a maxillary left upper central incisor with a fractured
fragment (14 mm long).

A B Fig. 23

Figure 21. (A) Schematic representation of a fractured instrument in a root Figure 23. Under 15x microscope magnification the fractured instrument
canal system; (B) clinical example of a fractured root canal instrument in the was clearly visible in the canal.
mesio-buccal root canal of a mandibular right second molar.
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LITERATURE REVIEW

the file and the canal wall in circular motion until it was After canal preparation and irrigation with heated 3.5%
noticed that the fractured file was loose in the canal. sodium hypochlorite and 17% EDTA solutions, a size
Considering the length of the fragment it was decided Large WaveOne Gold Gutta Percha Point (Dentsply
to attempt retrieval using the Yoshi Loop (Dental Cadre) Sirona) was fitted and the position verified radiographically.
(Figure 25a and 25b), a stainless steel micro-lasso
that extends from the end of a stainless steel cannula The canal was obturated with the selected gutta percha
attached to a handle with a retraction button for point and Pulp Canal Sealer (SybronEndo), using the con-
tightening the loop around the file segment. tinuous wave condensation technique with the Calamus
Dual Obturation Unit (Dentsply Sirona).
Under magnification, the preformed loop was carefully
placed around the exposed coronal aspect of the file.
6. Apical bacterial extrusion
The loop was tightened around the fractured file by mov-
ing the retraction button on the loop system. The loop All root canal preparation techniques cause apical
device was then used to slowly pull the loosened frag- debris extrusion to some degree, in spite of stringent
ment from the root canal system (Figure 26). Figure 27 control of working length of instruments during debri-
shows a magnified view of the retrieved instrument at- dement. Some amount of debris in the form of dentinal
tached to the micro-lasso from the Yoshi Loop. Note that chips, pulp fragments, necrotic debris, microorgan-
the tip of instrument is missing, indicating that the file isms, and intra-canal irrigants is unavoidably pushed
tip must have been fractured in a previous clinical appli- out from the root canal into the peri-apical tissues.
cation prior to the case presented in this case report.
The volume of materials that are extruded depends on
Having removed the fractured instrument, a size 30 canal/apical foramen size, instrumentation technique,
K-File was fitted loose in the root canal up to working instrument type, instrument size, preparation end-point
length as confirmed radiographically and with an electro- and irrigation solution (Figure 26).39
nic apex locator (ProPex, Dentsply, Sirona). According to
the file selection criteria outlined by Van der Vyver et al.
(2019)38 for WaveOne Gold files, a size large WaveOne
Gold File (45/05) was selected for canal preparation.

A
Figure 26. Retrieved fractured instrument using the Yoshi Loop.

B
Figure 25. (A) The Yoshi Loop (Dental Cadre), a stainless steel micro- Figure 27. Magnified view of the retrieved instrument attached to the
lasso that extends from the end of a stainless steel cannula attached to micro-lasso from the Yoshi Loop. Note that the tip of instrument is mis-
a handle with a retraction button for tightening the loop around a file sing, indicating that the file tip must have been fractured in a previous
segment; (B) Magnified view of the cannula and stainless steel micro-lasso. clinical application.

Fig. 28 Fig. 29 Fig. 30

Figure 28. Size 30 K-File fitted loose in the root canal up to working length Figure 30. Immediate post-operative result after canal obturation.
as confirmed radiographically and with an electronic apex locator (ProPex
Pixi, Dentsply, Sirona).
Figure 29. Cone-fit peri-apical radiograph confirming the correct apical
placement of the size Large WaveOne Gold Gutta Percha Point (Dentsply
Sirona).
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LITERATURE REVIEW <
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The extruded material is referred to as the ‘‘worm of 8. Oikonomou I, Spanaki-Voreadi A, Georgopoulou M. Proce-
necrotic debris’’ and has been linked to peri-apical dural errors during root canal treatment performed by under-
inflammation and postoperative flare-ups that will likely graduate students in Athens: a prospective study. Int Endod
interfere with healing.40 The incidence of flare-ups during J. 2007; 40:982.
9. Greene K, Krell K. Clinical factors associated with ledged
root canal treatment is reported to range between 1.4%
canals in maxillary and mandibular molars. Oral Surg Oral Med
and 16%.41
Oral Pathol. 1990; 70:490-7.
10. Schneider S. A comparison of canal preparations in straight
In asymptomatic chronic peri-radicular lesions a balance and curved root canals. Oral Surg Oral Med Oral Pathol Oral
exists between host defences and microbial aggression Radiol Endodontology. 1971; 32:271-5.
from the root canal microbiota associated with infected 11. Kapalas A, Lambrianidis T. Factors associated with root canal
canals in peri-radicular tissues.42 If bacteria are extruded ledging during instrumentation. Endod Dent Traumatol. 2000;
apically during root canal treatment procedures, there will 16: 220 - 31.
be a transient disruption in this balance and the host will 12. Eleftheriadis G, Lambrianidis T. Technical quality of root canal
mobilise an acute inflammatory response to re-establish treatment and detection of iatrogenic errors in an under-
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the equilibrium. The intensity of this acute inflammatory
13. Weine F. Endodontic therapy. 5th ed. St Louis: Mosby; 1996.
response depends on the number and/or virulence of the
324-30, 545-7. p.
bacteria.41 14. Walton R, Torabinejad M. Principles and practice of
endodontics. 3rd ed. Philadelphia: WB Saunders; 2002. 184,
According to Reddy and Hicks (1994) the variation in 222 - 3, 319 - 20. p.
levels of apical extrusion is primarily due to different root 15. American Association of Endodontists. Glossary of Endodontic
canal preparation techniques and instrument designs.43 Terms [Internet]. 2012. Available from: http://www.aae.org/
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Whitehead M, et al. Changes in root canal morphology in
sort of rotational action.39,44
simulated curved canals over-instrumented with a variety of
stainless steel and nickel titanium files. Aust Dent J. 1999;
Luisi et al. have demonstrated that the direction of in- 44 :12- 9.
strumentation, either in cervico-apical or apico-cervical, 17. Wu M, Fan B, Wesselink P. Leakage along apical root fillings
is also an important factor influencing apical extrusion.44 in curved root canals. Part I: effects of apical transportation
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driven- or engine-driven instruments are used, usually 18. Schäfer E, Dammaschke T. Development and sequelae of
extrude less debris.45,46 canal transportation. Endod Top. 2009; (4):75-90.
19. Berutti E, Castellucci A. Cleaning and shaping of the root canal
system. Endodontics. 2009; 2 (IL Tridente, Florence, Italy).
CONCLUSION 20. Kessler J, Peters D, Lorton L. Comparison of the relative risk
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Procedural errors during endodontic treatment are asso-
tation techniques. J Endod. 1983; 9:439-47.
ciated with a reduction in treatment success and possible 21. Allam C. Treatment of stripping perforations. J Endod. 1996;
non-resolution of apical periodontitis. Correct clinical 22:699 -702.
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Do the CPD questionnaire on page 262

The Continuous Professional Development (CPD) section provides for twenty general questions and five
ethics questions. The section provides members with a valuable source of CPD points whilst also achieving
the objective of CPD, to assure continuing education. The importance of continuing professional development
should not be underestimated, it is a career-long obligation for practicing professionals.

Online CPD in 6 Easy Steps

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4 Select the questionnaire that you wish to complete.

5 Enter your multiple choice answers. Please note that you have two attempts to obtain at least 70%.

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