This document discusses factors that affect the success and failure of endodontic (root canal) treatments. It defines what constitutes success, failure, healing and disease. The main factors discussed are incomplete removal of infected tissues from the root canal, ledge formation, separated instruments, overfilling, and anatomic variations. Clinical signs of success are absence of symptoms, while radiographic signs include lack of periapical radiolucency. Retreatment may be needed if the initial treatment is deemed incomplete or unsuccessful.

1. Presented by : Dr. Arpit Viradiya
Guided by : Dr. Ashutosh Paliwal

2. Introduction
• Since long, many studies are being conducted
to determine success and failure of
endodontic treatments.
• Different studies have shown that the success
rate for a root canal treatment ranges from 54
to 95 percent.
• Success is defined by goals established to be
achieved.

3. • The usual goal of endodontic therapy is to
prevent or heal the disease.
• Accordingly, endodontic treatment outcomes
should be defined in reference to healing and
disease.

4. Definitions related to endodontic
treatment outcome
• Healed : In which both clinical and
radiographic presentations are normal.
• Healing : It is a dynamic process, reduced
radiolucency combined with normal clinical
presentation.
• Disease : Means no change or increase in
radiolucency, clinical signs may or may not be
present or vice versa.

5. • A clear definition of what constitute a failure
following endodontic therapy is not yet clear.
• Failures cannot be subscribed to any particular
criteria of evaluation.
• Instead success or failures after endodontic
therapy could be evaluated from combination
of various criteria like clinical,
histopathological and radiographical criteria.

6. Clinical criteria of success of
endodontic treatment
• No tenderness on percussion/palpation.
• Normal tooth mobility.
• No evidence of subjective discomfort.
• No sign of infection/swelling.
• No sinus tract or integrated periodontal
disease.
• Tooth having normal form, function and
esthetics.

7. Radiographic evaluation
• The radiographic criteria for failures are
development of radiographic periapical areas
of rarefaction after endodontic treatment, in
cases where they were not present before the
treatment.
• Or increase in size of
radiolucency after endodontic
treatment.

8. Histological criteria of success of
endodontic treatment
• Absence of inflammation.
• Regeneration of PDL fibers.
• Presence of osseous repair.
• Repair of cementum.
• Repair of previously resorbed areas.
• Absence of resorption.

9. Factors affecting success or failure
• Diagnosis and treatment planning.
• Radiographic interpretation.
• Anatomy of tooth and root canal system.
• Debridement of the root canal space.
• Asepsis of treatment regimen.
• Quality and extent of apical seal.
• Systemic health of the patient.
• Skill of the operator.

11. Infection
• Presence of infected and necrotic pulp tissue
in root canal acts as the main irritant to the
periapical tissues.
• For success of endodontic therapy, thorough
cleaning of root canal system is required for
removal of these irritants.

12. Incomplete debridement of the root
canal system.
• It is a principle factor contributing to
endodontic failures.
• The main objective of root canal therapy is the
complete elimination of the microorganisms
and their byproducts from the root canal
system.

13. • The poor debridement can lead to residual
microorganisms, their byproducts and tissue
debris which further recolonize and contribute
to endodontic failure.

14. Excessive hemorrhage
• Small haemorrhages during endodontic
procedure are repaired without incident.
• Extirpation of pulp and instrumentation
beyond periapical tissues lead to excessive
hemorrhage.

15. • Mild inflammation is produced because of
local accumulation of blood.
• The extravasated blood cells and fluids must
be resorbed otherwise they act as foreign
body.
• Also the extravasated blood acts as nidus for
bacterial growth especially in presence of
infection.

16. Overinstrumentation
• Instrumentation beyond
apical foramen causes
decrease in the prognosis of
endodontic treatment
because of trauma to
periodontal ligament and
alveolar bone.

17. • When instrumentation of the root canal
system remains within the confines of root
canals, the chances of success of endodontic
therapy are more. (Strindberg et al 1956)

18. Chemical irritants
• During endodontic
treatment, various
medications are used as
dressing in root canal.
• Their functions are to
eliminate or reduce
microbial flora, prevent or
lessen pain, reduce
inflammation or stimulate
repair.

19. • They decrease the prognosis of endodontic
therapy if get extruded in the periapical
tissues.
Int J Periodont Restorative Dent 17:75, 1997

20. Instrument separation
• Schilder et al reported that
– If instrument separation occurred in tooth with
presence of vital pulp before treatment, prognosis
was not much affected.
– but if instrument separation occurred in teeth
with pulpal necrosis, prognosis was found to be
poor after treatment.
J Endod 24:38, 1998

21. • Basically separated instruments impair the
mechanical instrumentation of infected root
canals apical to instrument, which contribute
to endodontic failure.

22. Canal blockage and ledge formation
• Canal blockage can occur due to accumulation
of dentin chips or tissue debris which prevents
the instrument to reach its full working length.

23. • Ledge formation usually occurs
by using straight instruments in
curved canals.
• All these lead to working short
of the canal terminus and thus
bacteria and tissue debris may
remain in non-instrumented
area contributing to endodontic
failure.

24. Perforations
• It is a mechanical communication between
root canal system and the periodontium.
• It occurs by
– Lack of knowledge of internal anatomy of tooth
– Lack of attention while operating
– Misdirection of instruments
• Prognosis of endodontically treated tooth with
perforations depend on many factors
J Am Dent Assoc 131:196, 2000

25. • Location : Depends on its closeness to gingival
sulcus.
• Time : which has elapsed before defect is
repaired
• Adequacy of perforation seal
• Size of perforation

26. Incompletely filled teeth
• It occurs due to
– Incomplete instrumentation
– Ledge formation
– Blockage
– Improper measurements of WL
• Several studies have shown poorer prognosis
of teeth with underfillings, especially those
with necrotic pulps.
J Endod 28:454, 2002.

27. • Remaining infected necrotic tissue,
microorganism and their byproducts in
inadequately instrumented and filled teeth
cause continuous irritation to the periradicular
tissues leading to endodontic failure.

28. Overfilling of root canals
• It occurs because of
– Apical root resorption
– Incompletely formed roots (open
apex)
– Over instrumentation of root
canal system
• Overfilling causes continuous
irritation of the peri-apical
tissues.

29. • The filling material acts as a foreign body
which may generate immunological response.
• Several studies have shown biofilms formation
on extruded material which contains
treatment resistant bacteria.
J Endod 30:54, 2004

30. Corrosion of root canal fillings
• Corrosion is the
tendency of most of the
metals to revert to their
lower form by oxidation.
• Silver cones have shown
to produce corrosion.

31. • The main area of corrosion of silver cones is
coronal and the apical portions, the areas
which contact tissue fluids via periapical
exudation or saliva.
• The corrosion products are cytotoxic and may
act as tissue irritants causing persistent
periapical inflammation.

32. Anatomic factors
• Presence of overly curved
canals, calcifications, numerous
lateral and accessory canals,
bifurcations, aberrant canal
anatomy like C or S shaped
canals may pose problems in
adequate cleaning and shaping.
• These can lead to endodontic
failure.

33. Root fractures
• Endodontic failures can occur by partial or
complete fractures of the roots.
• Prognosis of teeth with vertical root fracture is
poorer than horizontal fractures.

34. Traumatic occlusion
• Traumatic occlusion has also been reported to
cause endodontic failures because of its effect
on periodontium.

35. Periodontal consideration
• An endodontic failure may occur because of
communication between the periodontal
ligament and the root canal system.

36. • Also the recession of attachment apparatus
may cause exposure of lateral canals to the
oral fluids which can lead to reinfection of the
root canal system because of percolation of
fluids.

37. Systemic factors
• The systemic disease may
influence the local tissue
resistance and thus interfering
with the normal healing process.
• When systemic disease is present,
the response of the periapical
tissues may get intensified if there
is increase in concentration of
irritants during endodontic
therapy.

38. • Thus severe reaction may occur following
cleaning and shaping.
• Healing is also impaired in patients with
systemic disease.

39. • Various systemic factors can interfere with
success of endodontic therapy are
– Nutritional factors
– Diabetes mellitus
– Renal failure
– Blood dyscrasias
– Hormonal imbalance
– Autoimmune disorders
– Opportunistic infections
– Aging
– Patients on long term steroid therapy
• Thus before starting endodontic therapy, a
complete medical history is essential to predict
the prognosis of the tooth.

40. Before going for endodontic
retreatment following factors should
be considered
• If patient is asymptomatic even if treatment is
not proper, the retreatment should be
postponed.
• Patient’s needs and expectations.
• Strategic importance of the tooth.
• Periodontal evaluation of the tooth.
• Other interdisciplinary evaluation.
• Chair time and cost.

41. Before performing retreatment
following points should be considered
• Retreatment may be performed to prevent the
potential disease.
• To gain access into root canal extensive
coronal restoration has to be removed.
• Technical problems may result from previous
treatment or aberrant canal anatomy.
• Even after retreatment sometimes better
results may not be achieved.

42. • Root canal filling materials have to be
removed during retreatment.
• Prognosis of retreatment could be poorer than
the initial endodontic therapy.
• Patient might be more apprehensive than with
initial treatment.

43. • 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.
Int Endod J 37:272, 2004

44. Steps in retreatment technique
• Access to root canal
– Through crown
– By removal or crown
• Access to apical area
– By removal of root canal filling material
– By removal of separated instruments.
• Reshaping
• Antimicrobial treatment.

45. CORONAL DISASSEMBLY
• Clinicians generally access the pulp chamber
through the existing restoration if it is
functionally well designed, well fitting and
esthetically pleasing.
• If the restoration is inadequate or if additional
access is required, the restoration should be
sacrificed.

46. Factors influencing restoration
removal
• PREPARATION TYPE
• RESTORATION DESIGN & STRENGTH
• RESTORATIVE MATERIAL
• CEMENTING AGENT
• REMOVAL DEVICES

47. There are several important removal
devices which may be divided into
three categories:
1. Grasping instruments : K.Y. Pliers and
Wynman Crown Gripper
K. Y. Plier

48. • Percussive instruments : Crown-a-Matic and
the Coronaflex
Coronaflex

49. • Passive-active instruments : Metalift and the
Higa Bridge Remover.
Metalift

50. • Clinicians must clearly define the risk versus
benefit with patients before removal of an
existing restoration.

51. • Gaining access through existing restoration
helps in :
– Facilitating rubber dam placement
– Maintaining form, function and esthetics
– Reducing cost of replacement
• Disadvantages of retaining a restoration include:
– Reduced visibility and accessibility
– Risks of irreparable errors
– Risks of microbial infection if crown margins are
poorly adapted

52. Establish access to root canal system
• In some cases post and core needs to be
removed for gaining access to the root canal
system.
• Factors affecting post removal :
– Post type
– Cementing medium
– In occlusal space
– Existing restoration
– Position of coronal most aspect

53. TECHNIQUES FOR POST REMOVAL:
• Successful post removal requires removing all
circumferential restorative material from pulp
chamber.
• commonly used methods and techniques for
removal of post are
– Ultrasonic technique
– Masserann technique
– PRS option

54. ULTRASONIC METHOD:
• Piezo electric ultrasonic systems offers the
clinician certain advantages in endodontic
disassembly and retreatment.
• Generally, the CPR -2 ultrasonic instrument is
used on full intensity to remove the remaining
core materials periphery to the post.

55. • CPR - 3,4, & 5 instruments are
designed to work in small, restricted
and confined spaces.
• If space is severely restricted, CPR - 6,
7 & 8 titanium ultrasonic instrument
can be used on low intensity.

56. • Once the post has been fully exposed,
rotosonics can be used to loosen and
remove the post.
• The regular ROTOTIP (Ell man
international Hewlett N.Y.) is a high
speed Friction grip 6 sided
instrument.
• When rotated, it produces vibration
to loosen and remove the post.
• If efforts are unsuccessful, the
clinician should select CPR - 1 because
of its superb energy transfer.

57. • CPR-1 has a ball at its working end which is
kept in contact with post to maximize energy
transfer.
• This is used with full intensity and is moved
around the post circumferentially with up &
down motion.

58. Removing canal obstructions and
establishing patency
• Patency of canal can be regained by removing
obstructions in the canal which can be in the
form of silver points, gutta-percha, pastes,
sealers, separated instruments and posts.

59. Silver point removal
• Silver points can be retrieved from
canal by following methods:
– Using microsurgical forceps – Its use is
ideal especially when cone heads are
sticking up in the chamber.
– Using ultrasonic – In this ultrasonic file
is worked around the periphery of silver
point to loosen it with vibration.

60. • Using hedstroem files : In this headstroem
files are placed in the canal.
• These files are twisted around each other by
making clockwise rotation.
• This will make grip around silver point which
then can be removed.

61. • Using hypodermic needle which
is made to fit tightly over the
silver point over which
cyanoacrylate is placed as an
adhesive.
• When it sets, needle is removed
with pliers.
• By tap and thread option using
microtubular taps from post
removal system kit.
• By using instrument removal
system.

62. Gutta-percha removal
• The relative difficulty in removing GP varies
according to the
– Canal length
– Canal c/s dimensions
– Canal curvature.
• Regardless of the technique, its best removed
in a progressive manner to prevent
displacement of irritants periapically.

63. • Dividing the root into three parts G.P. is
initially removed from canal in coronal 1/3,
then middle 1/3 & finally eliminated from
apical 1/3 of the canal.
• In canals that are relatively large & straight,
single cones can be removed in one motion.

64. • Single cone:
• They can be removed by using
– A headstroem file
– Tweezers
– Steiglitz forceps
– Endosonics.

65. • H file method : largest H-files that will fit the
cone should be used to reduce the risk of
fracture.
• The file is gently screwed into the canal
(obturated) until resistance is met.
• At this point the instrument is withdrawn from
canal along with G.P. cone.

66. • Endosonics can also be used.
• It loosen the cement around the single cone,
there by aiding removal.
• If cones are accessible they can be gripped
with Tweezers / Steiglitz forceps for removal.

67. • CONDENSED GUTTA PERCHA
• Condensed G.P. can be removed using a
combination of
– Heat
– G.G drills
– Niti rotary instruments
– Hand instruments such as H files
– Solvents
– Ultrasonic
– Paper points

68. Heat
• Traditionally power source in conjunction with
specific heat carrier instrument such as Touch
- N - Heat / system B has been used to thermo
soften & remove fragments of G.P from root
canal systems.

69. • Disadvantage: It limits its ability to place into
under-prepared systems and around pathways
of curvature.
• Technique: Activate the instrument until it is
red hot, then place it into the coronal most
aspect of G.P.

70. • The heat carrier is
then deactivated.
• And as it cools,
withdrawal will result
in removal of attached
fragment of G.P.
• The process is
repeated as long as it
continues.

71. Heat & Instrument removal
• In this method a hot instrument is placed into
G.P. & immediately with drawn to heat soften
the material .
• A size 35, 40/45 H-file is then selected gently
screwed into the thermo softened mass.

72. • When GP cools, it will freeze on flutes of file.
• In poorly obturated canals, removing the file
can, at times, eliminate the engaged G.P in
one motion.
• This technique is good in those cases where
G.P. extends beyond the foramen.

73. Solvents:
• Solvents include chloroform, xylene,
rectified turpentine, chloroform &
eucalyptus oil.
• There has been some concern expressed
in literature about carcinogenic potential
of the chloroform.
• Rectified turpentine is a useful
alternative.
• Eucalyptus is heated and used in order
to be as effective as chloroform.

74. • Solvents should be used only in small amounts
and must be contained with in R.C. system.
• Using solvent too early in treatment leaves a
messy layer of dissolved G.P. coating the root
canals & pulp floor, which can be difficult to
remove.
• If most of G.P. has been removed
mechanically, then a minimal amount of
solvent is required to dissolve the remaining.

75. FILE & CHEMICAL REMOVAL
• It is the best option to remove G.P from small
& curved canals.
• The technique involves filling the pulp
chamber with chloroform, selecting a
appropriate size file & gently picking into
chemical softened G.P.
• Initially, a size 10 or 15 SS file is used to pick
into G.P. occupying the coronal 3rd.

76. • Frequent irrigation creates a pilot hole and
sufficient space for the serial use of larger file
to remove G.P.
• This method is continued until G.P is no longer
evident on cutting flutes when the files are
with drawn from solvent filled canal.
• After G.P. has been removal from coronal 3rd,
repeat the technique in middle 1/3 & finally
apical 1/3.
• This progressive removal technique helps
prevent extrusion of chemically softened
material apically.

77. Paper point & chemical removal
• G.P. & most sealers are miscible in chloroform
& once in solution can be absorbed and
removed with appropriately sized paper
points.
• Drying solvent filled canals with paper point is
known is “Wicking” & is always the final step
of G.P. removal.
• This wicking action is essential in removing
residual G.P. & sealer out of fins, cul de sacs &
aberrations of R.C. systems.

78. • In this technique, the canal is
1st flushed with chloroform &
solution is then absorbed &
removed with appropriately
sized paper points.
• Paper points “wick” by
pulling dissolved material
from periphery to central.

79. • Process is repeated as long as it continues to
be visibly productive.
• After chloroform wicking procedures, canal is
flushed with 70% isopropyl alcohol, & wicked
for further elimination of chemically softened
G.P. residues.

80. Rotary Removal
• Active Niti rotary files (dentsply) are the most
effective & efficient instruments for G.P.
removal.
• Disadvantages: Should be used with caution
in under-prepared canals & are generally not
selected for removing G.P in canals that do
not accept them passively.

81. • When attempting for removal, the R.C. should
be divided to 3 parts.
• Select appropriately sized rotary instrument
that will fit passively in these canals.
• To soften & engage G.P. mechanically rotary
instrument must turn at speeds between
1200-1500 RPM.
• Rotational speed is based on friction required
to mechanically soften G.P.

82. ULTRASONIC
• Piezoelectric ultrasonic system represents a
useful technique to rapidly remove G.P.
• Ultrasonic instrument produces heat and
thermosoftens G.P.

83. • Specially designed ultrasonic instrument are
carried into canals, that have sufficient shape
to receive them.
• This method will float G.P coronally into pulp
chamber where it can be sub subsequently
removed.

84. G.G.Drills / Burs:
• G.G. drills are extremely efficient for removing
G.P. from coronal parts of well compacted root
canals.
• They need to be rotated in a slow speed hand
piece generating frictional heat that will aid
G.P. removal.

85. Carrier Based Gutta Percha Removal
• Techniques are same as for G.P & silver point.
• Initially it used to be metal & file like
• Yet over the past several years they have been
manufacturing easier to remove plastic
materials.
• After careful access and complete
circumferential exposure of the carrier, suitable
grasping pliers are selected and a purchase is
obtained on the carrier.

86. • Carrier is grasped with the pliers and removal is
attempted using fulcrum mechanics rather than
a straight pull out of the tooth.
• Ultrasonic tip can be used to produce heat and
thermosoften the G.P.
• The activated ultrasonic instrument is gently
moved apically and carrier is often times
displaced and floated out coronally.
• Once the carrier is removed, the remaining G.P.
can be removed using solvents.

87. Paste removal
• When evaluating a paste case for retreatment,
it is useful to chemically understand that
pastes can generally be divided into
• a) Soft, Penetrable & Removable
• b) Hard, impenetrable, unremovable

88. • However, it is important to understand that
because of the method of placement, the
coronal portion of paste in the canal is most
dense.
• Abrasive coated ultrasonic instruments can be
used for the safe removal of hard &
impenetrable paste.
• Heat, end-cutting rotary NiTi instruments and
small sized hand files with solvents such as
Endosolv R and Endosolv E are used to remove
soft & penetrable paste.

89. Broken Instrument Removal
• During R.C. preparation procedures, the
potential for instrument breakage is
always present.
• Many clinicians associate “Broken
instrument” with separated files, but
the term could also apply to a silver
point, a lentulospiral, a G.G. drill, or any
obstruction left behind in the canal.

90. • Historically, the consequences of leaving / by
passing broken instruments have been
discussed and varieties of approaches for
removing these obstructions have been
presented.
• Because of technologic advancements in
vision, ultrasonic instrumentation and
microtube delivery methods, separated
instruments can usually be removed.

91. Factors influencing broken instrument
removal
• Cross sectional diameter, length & curvature of
R.C.
– If 1/3 of overall length of obstruction can be exposed
 can be removed.
– If its just in straight portion of canal - can be removed
– When the separated instrument lies partially in the
canal curvature still possible to remove.
– If entire segment is apical to curvature - safe access
cannot be accomplished and removal is not possible.

92. • Type of material comprising the obstruction
– S.S. files - easier to remove as they do not #
during removal process.
– NiTi files - may explode and break again due to
heat build up caused by ultrasonic devices.

93. Steps
• 1st step  Coronal access 
• High speed friction grip surgical length burs
are selected to create straight line access to
canal orifice
• 2nd step  Radicular Access 
• If radicular access is limited - hand files are
used serially (small to large) to create
sufficient space to safely introduce G.G. drill’s.

94. • These G.G drills are then used like “brushes”
to create additional space and maximize
visibility coronal to obstruction.
• If greater access required, then bud shaped tip
of GG can be modified and used to create a
circumferential “staging platform”.

95. Staging Platform
– This is done by selecting a G.G. with maximum c/s
diameter that is slightly larger than the visualized
instrument.
– The bud of G.G. is altered by cutting it perpendicular to
long axis at its maximum C/S diameter.
– The “modified” G.G. is rotated at 300 rpm, gently
carried to canal and directed apically, until it lightly
contacts the coronal aspect of obstruction.

96. • This clinical action creates a small
“Staging Platform” that facilitates the
insertion of zirconium nitride coated
ultrasonic tips
• 3rd Step  Removal
• Before performing any removal
especially when treating a multi-rooted
teeth the potential problem is that the
#ed segment floating out of one canal
and finding its way into one of the other
orifice.

97. • So, to prevent this it is wise to place cotton
into the other orifice.
• Once the ultrasonic instrument is selected,
based on depth of broken file and space
availability, the instrument should be
activated at the lowest power setting.
• Dry field is preferred, so that clinician has
constant vision between tip and broken
instrument.

98. • Then the selected tip is moved
lightly in counter clockwise direction
around the obstruction and
trephines around the coronal few
mm of obstruction.
• Typically during ultrasonic use 
the obstruction begins to unwind,
loosen and spin.
• On occasion where this ultrasonic
technique doesn’t work the
microtube device can be selected to
engage and remove the obstruction
mechanically.

99. Apical Obstructions / Blockage
• When canals have been under filled,
obstructive calcification might be found apical
to unfilled portion.
• After coronal pre-enlargement and relocation
of the canal orifice with G.G. drills, the coronal
part of the canal is copiously irrigated with
NaOCl and then thoroughly dried with paper
points.

100. • At this stage if possible the intracanal anatomy
should be inspected carefully under
microscope.
• Then a small size precurved K file in
association with a lubricating gel is inserted
with a slight pecking motion to try to find a
catch.
• As long as catch is felt at tip of K file, apical
progression should be continued and checked
periodically with radiograph until the canal
terminus is launched.

101. Ledges:
• Often a ledge has been formed at the end of
the previous obturation of the canal.
• Most of the time ledge is the result of an
inadequate angle of access to the R.C.
• Preflaring the coronal portion of the canal
with K files and relocating the canal with G.G.
are preliminary steps to by pass.

102. • Flood the canal with irrigating solution.
• Select a no. 10 S.S. K file place a sharp 1mm
curvature at the tip and orient the rubber
stopper toward the file tip.
• Insert the file in the canal with the tip directed
toward the canal curvature.

103. • Pick gently with very short strokes, searching
for a catch.
• This procedure will remove the irrigant and
help to disintegrate the dentine mud.
• If Unsuccessful, rebend the file tip and repeat
the same procedure while slightly reorienting
the tip.
• When a catch is felt, it is moved in and out of
the canal utilizing ultra-short push-pull
movements.

104. • When the file moves freely, it may be turned
clockwise on withdrawal to smoothen or
eliminate the ledge.

105. Conclusion
• Training proctol and technology allow
clinicians to greatly expand their abilities in
non surgical retreatment. Clinicians need to
weigh risk versus benefit and recognize that at
times surgery / extraction might be in
patient’s best interest.
• When choosing non surgical retreatment
careful assessment and treatment planning
with each case is the corner store of success.

106. References