Root Canal Obturation: An Update - IneedCE.com

Root Canal Obturation:
An Update
Written by James L. Gutmann, DDS, Sergio Kuttler, DDS and Stephen P. Niemczyk, DMD
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Educational Objectives
The overall goal of this article is to provide the reader with
information on available materials and techniques for the
obturation of root canal systems.
Upon completion of this course, the dental professional
will be able to:
1. List the purposes of root canal obturation
2. List the characteristics of gutta-percha used for obturation
3. List and describe the contemporary materials and
techniques for obturating root canals
4. List the most widely-used techniques for gutta-percha
carrier-based obturation and describe its strengths and
shortcomings.
Abstract
Obturation is a critical component of root canal therapy, and
must both provide a complete seal for the root canal system
and eliminate all avenues of leakage from the oral cavity.
Historically, gutta-percha cones have been the standard
material of choice for root canal obturation, used together
with a sealer/cement. The first gutta-percha carrier-based
obturating techniques were developed more than two decades
ago. More recently, obturating techniques have been
introduced that include resin-based sealers and obturators,
syringe-applied heated gutta-percha, and the use of guttapercha
as an outer coating on obturator carriers composed
of plastic or metal. It is important to select an obturation
technique that offers consistency and is easy to use.
Introduction
Root canal obturation involves the three-dimensional filling
of the entire root canal system and is a critical step in
endodontic therapy. There are two purposes to obturation:
the elimination of all avenues of leakage from the oral cavity
or the periradicular tissues into the root canal system;
and the sealing within the root canal system of any irritants
that remain after appropriate shaping and cleaning of the
canals, thereby isolating these irritants. Pulpal demise and
subsequent periradicular infection result from the presence
of microorganisms, microbial toxins and metabolites, and
the products of pulp tissue degradation. Failure to eliminate
these etiologic factors and to prevent further irritation as a
result of continued contamination of the root canal system
are the prime reasons for failure of nonsurgical and surgical
root canal therapy. 1,2,3,4,5
The importance of three-dimensional obturation of the
root canal system cannot be overstated, with the ability
to achieve this goal primarily dependent on the quality of
canal cleaning and shaping as well as clinical skill. Other
factors that influence the ultimate success or failure of each
case include the materials used and how they are used. The
ultimate coronal restoration of the tooth following canal
obturation may loom as the most important goal, for there
is reasonable evidence that coronal leakage through improperly
placed restorations after root canal treatment and
failure of the restorative treatment or lack of health of the
supporting periodontium are the final determinants of success
or failure in treatment. 6,7,8
Figure 1. Factors influencing complete obturation
Quality of the cleaning and shaping of the canal system
Skill and experience of the clinician
Materials and their usage
Restoration of the tooth
Health of the supporting periodontium
Characteristics of an Ideal Root Canal Filling
An ideal root canal filling three-dimensionally fills the entire
root canal system as close to the cemento-dentinal junction
as possible. Minimal amounts of root canal sealers, most of
which have been shown to be biocompatible or tolerated by
the tissues in their set state, are used in conjunction with the
core filling material to establish an adequate seal. Radiographically,
the root canal filling should have the appearance
of a dense, three-dimensional filling that extends as close as
possible to the cemento-dentinal junction. These standards
should serve as the benchmark for all clinicians performing
root canal therapy, and it is only through a knowledgeable
approach to root canal treatment that quality assurance can
be continually demonstrated in the obturation of root canal
systems. 9,10
The ideal root canal filling
Figure 2a. 3-D filling of the entire root canal space as close as
possible to the cemento-dentinal junction
Figure 2b. Radiographically dense fill with absence of voids
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Figure 2c. Shape reflecting a continuously tapered funnel that is
approximately the same as the external root morphology
While a plethora of materials has been advocated over the last
150 years for root canal obturation, historically, gutta-percha
has proven to be the material of choice for successful filling
of root canals from their coronal to apical extent. Although
it is not the ideal filling material, gutta-percha has satisfied
the majority of criteria for an ideal root filling material. The
disadvantages of gutta-percha – specifically, its adhesiveness,
lack of rigidity, and ease of displacement under pressure – do
not overshadow its advantages. In light of its shortcomings,
a sealer/cement is always used with gutta-percha. However,
regardless of the delivery system or technique used, neither
gutta-percha nor sealer/cement alone enables standard-ofcare
canal obturation. In addition, the available materials and
techniques do not routinely provide for an impervious seal of
the canal system; all canals leak to a greater or lesser extent.
It is recommended that clinicians master multiple obturation
techniques and become competent with various root canal
sealers/cements, to be able to manage the diversity of anatomical
scenarios that may be encountered. 11,12
Contemporary Sealers/Cements
The use of a sealer during root canal obturation is essential
for success. Not only does it enhance the possible attainment
of an impervious seal, it also serves as a filler for canal
irregularities and minor discrepancies between the root canal
wall and core filling material. Sealers are often expressed
through lateral or accessory canals and can assist in microbial
control should there be microorganisms left on the root canal
walls or in the tubules. 13,14,15,16,17,18 Sealers can also serve
as lubricants, enabling thorough seating of the core filling
material during compaction. In canals in which the smear
layer has been removed, many sealers demonstrate increased
adhesive properties to dentin in addition to flowing into the
patent tubules. 19,20,21,22,23,24,25,26,27,28,29 A good sealer should be
biocompatible and well tolerated by the periradicular tissues,
and although all sealers exhibit toxicity when freshly mixed,
their toxicity is greatly reduced on setting and all are absorbable
when exposed to tissues and tissue fluids. Subsequent
tissue healing or repair generally appears unaffected by most
sealers, provided there are no adverse breakdown products of
the sealer over time. In particular, the breakdown products
may have an adverse action on the proliferative capability of
periradicular cell populations. Some clinicians consider that
a small puff of root canal filler extending beyond the working
length is indicative of a fully obturated canal space with
a well-sealed apical constriction. Excessive sealer should not
be routinely placed in the periradicular tissues as part of an
obturation technique. 30,31,32,33,34,35,36,37,38,39,40,41,42
Sealers/cements can be grouped based on their prime constituent
or structure, such as zinc oxide-eugenol, polyketone,
epoxy, calcium hydroxide, silicone, resin, glass ionomer, or
resin-modified glass ionomer. However, many of the sealers/
cements are combinations of components, such as zinc oxideeugenol
and calcium hydroxide, 43 with the addition of calcium
hydroxide claimed to create a therapeutic material that can
be inductive of hard tissue formation. 44,45 Epoxy-based and
methacrylate-based resin sealers that can be bonded to the root
canal dentin (but not to gutta-percha) are also now available. 46
Sealers should be mixed to a creamy consistency, allowing
them to adhere to the master cone and not ball up at the shaft of
the cone, leaving the gutta-percha exposed. The sealer should
adhere to the cone evenly along its length and at the end of the
cone. Clinicians should read the product insert and material
safety data sheet for each product chosen before using it.
Contemporary Core Filling Materials
Gutta-percha is the standard material of choice as a solid
core filling material for canal obturation. It demonstrates
minimal toxicity and minimal tissue irritability, is the least
allergenic material available when retained within the canal
system, 47 and in cases of inadvertent gutta-percha cone
overextension into the periradicular tissues, is well tolerated
provided the canal is clean and sealed.
Chemical solvents have been used for almost 100 years to
soften gutta-percha, with methods ranging from merely dipping
the gutta-percha cones into the solvent for one second for
better canal adaptation, to creating a completely softened paste
of gutta-percha with the solvent. Solvents used have included
chloroform, halothane, rectified white turpentine, and eucalyptol.
Periradicular tissues may be irritated if the solvent is
expressed beyond the canal or significant amounts of softened
gutta-percha are inadvertently placed into the periradicular
tissues. Failure to allow for dissipation of chemical solvents, if
volatile, or the removal of excess solvent with alcohol can result
in significant shrinkage and possible loss of the apical seal. The
use of chemical solvents has been both praised and questioned,
but with the advent of thermoplasticized gutta-percha, the
need to consider the use of solvents at any time must be questioned.
The use of solvents, however, may still be considered
for a number of challenges the clinician may face in daily practice,
such as the custom fitting of master cones in irregular apical
preparations or following apexification. 48,49,50,51,52,53,54,55,56,57
Gutta-percha Cones
The composition of gutta-percha cones is approximately
19% to 22% Balata and 59% to 75% zinc oxide, with the re-
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mainder a combination of various waxes, coloring agents,
antioxidants, and metallic salts. 58 The specific percentages for
components varies by manufacturer, with resulting variations
in the brittleness, stiffness, tensile strength, and radiopacity
of the individual cones attributable primarily to the percentages
of gutta-percha and zinc oxide. The antimicrobial activity
of gutta-percha is also primarily due to the zinc oxide. 59,60
The cones are manufactured in both standardized and nonstandardized
sizes. The standardized sizes coordinate with
the ISO root canal files sizes 15 through 140 and are used
primarily as the main core material for obturation. They generally
have a 2% taper, but can have a 4 or 6% taper or more
(Figure 3). The non-standardized sizes are more tapered from
the tip or point to the top. With some obturation techniques
these cones have been used primarily as accessory or auxiliary
cones during compaction, being matched with the shape of
the prepared canal space or the compaction instrument.
Non-standardized cones began to assume a greater role as the
primary core material in the more contemporary obturation
techniques, and with the development of more predictable
shapes with current nickel titanium (NiTi) rotary and hand
instruments, cones tapered from 4% to 10% have gained use.
Figure 3. Tapered gutta-percha cones
In particular, for techniques that use vertical compaction of
heat-softened gutta-percha, both the non-standardized and
more tapered cones have become quite acceptable. Custom
cones can also be developed for canals with irregular or large
apical anatomy, Over time, numerous methods have been
advocated for obturating the prepared root canal system, each
with their own claims of ease, efficiency, or superiority. Most
contemporary techniques still rely on gutta-percha and sealer
to achieve their goal. Four basic techniques exist for the obturation
of the root canal system with gutta-percha and sealer
(Figure 4): (1) the cold compaction of gutta-percha; (2) the
compaction of heat-softened gutta-percha with cold instruments
until it has cooled; (3) the compaction of gutta-percha
that has been thermoplasticized, injected into the system, and
compacted with cold instruments; and (4) the compaction of
gutta-percha that has been placed in the canal and softened
through the continuous wave technique (Calamus). A multitude
of variations on these four basic themes exists. For
injectable thermoplastic obturation techniques, gutta-percha
may come in either pellet forms or in cannulae.
Figure 4a. Figure 4b. Figure 4c.
Cold compaction carrier Heated compaction Presoftened core
No single technique has proven to have statistically
significant superiority when considering both in vitro and
in vivo studies, as the success of all techniques is highly
dependent on the cleaning and shaping of the canals and the
clinician’s expertise in the use of a particular technique. 61,62
While many have advocated the use of the lateral compaction
technique or a single cone fill (monocone) to achieve a
quality apical seal, the technique in itself does not necessarily
favor the filling of canal irregularities. 63 Recognizing this,
use of a softened gutta-percha technique with heat or chemical
softening is required to achieve a thorough obturation.
In addition, while filling the entire root canal system is the
major goal of canal obturation, a major controversy exists as
to what constitutes the apical termination of the root canal
filling material. Working length determination guidelines
often cite the cemento-dentinal junction or apical constriction
as the ideal position for terminating canal cleaning and
shaping procedures and placing the filling material. However,
the cemento-dentinal junction is a histologic and not
a clinical position in the root canal system 64 (Figure 5) and,
in addition, the cemento-dentinal junction is not always the
most constricted portion of the canal (yellow arrows) in the
apical portion of the root (Figure 6). 65,66,67,68,69,70,71,72,73,74,75
Figure 5. Histologic position of cemento-dentinal junction
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Contemporary practices of obturation favor material softening;
even this does not guarantee that an impervious seal of
the root canal system will be established. Also, with softened
gutta-percha obturation techniques there has been a greater
incidence of material extrusion beyond the confines of the
canal. While softening of gutta-percha may be viewed as
routinely desirable, the selective use of this technique solely
or in combination with a solid core of gutta-percha must be
at the discretion of the competent clinician when anatomy
dictates this approach. 76,77
However, closer examination subsequent to filling showed
voids using the single cone technique throughout the length
of the root filled using this technique (Figure 8). The single
cone technique did not produce a monoblock obturation
(Figure 9). The gutta-percha from the GT obturator flowed
into the canal isthmus and filled it (Figure 10).
Figure 8. Voids using single cone technique
Figure 6. Apical constriction of root canal
Figure 9. Cross-section with ActiV GP and GT Series X obturation
Recent research conducted at Nova Southeast University
using micro CT scanning technology has shown the effectiveness
of scanning for imagery and the greater precision
observed compared to standard radiographs. In one example,
a mesiobuccal canal was filled using GT ® Series X
obturator and the mesiolingual canal was filled using a single
cone technique (ActiV GP). It appeared from one angle that
all canals were equally filled (Figure 7).
Figure 7. Radiograph of filled canals
ActiV GP
GT Series X obturator
Figure 10. Canal isthmus filled with GT obturator gutta-percha
Canal isthmus filled
with GT obturator
gutta-percha
Differences in obturation techniques and results are also
more observable using CT scanning than using traditional
radiographs. 78 Contemporary techniques include the use of
bonded root canal filling materials. Recent developments in
resin-bonding have led to the availability of resin cones and
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pellets similar in shape and size to gutta-percha materials.
Resin-based cones containing methacrylate resin, fillers,
bioactive glass, and polymers are available that can be handled
similarly to gutta-percha and can be used with a lateral
or vertical compaction technique. Resin-based materials can
also be delivered via a heated syringe (Obtura gun, Spartan
Obtura). Since resin-based materials require a slightly moist
environment, it is important to avoid using any dessicating
solutions, such as alcohol, during root canal preparation.
Further, if sodium hypochlorite or peroxide was used during
root canal preparation, this must be thoroughly removed
prior to using a resin-based material as it would reduce the
ability of the resin material to bond. Similarly, the smear
layer must also be thoroughly removed.
Prefabricated Obturators
Gutta-percha can also be formed on a plastic carrier or corecarrier.
Prefabricated obturators were first described in 1978
by William Ben Johnson. 79 The prototype for the obturator
had been prenotched K-files wrapped in gutta-percha (hand
formed) that were then heated over a flame until the surface
glistened and expanded. These prenotched “obturators”
were inserted into the canal and apical pressure applied
while the handle was twisted off (Figure 11).
Figure 11. Prototype obturator
Plus, ProTaper ® Universal and ProSystem GT ® Obturators
(Dentsply, Tulsa Dental), and Soft-Core ® (Soft-Core ®
Texas, Inc.).
Figure 12. Calamus®
Current plastic obturators are available in a nonvented shape
with a taper of around 0.04 (Densfil) and a vented shape
with the same taper (Thermafil Plus). Both are biologically
inert. 80 The carrier is thick with a thinner outer coating of
gutta-percha, which helps to reduce material shrinkage as
the gutta-percha cools in the canal (Figure 13). A vented
prefabricated obturator helps the flow of gutta-percha during
placement and also aids in retrieval of the obturator
should retreatment be necessary.
For sizes 40 and below in the Thermafil series, an insoluble
liquid crystal plastic is used. For size 45 and above soluble
polysulfone polymer is used. All of these use a size verifier to
help select the correct size obturator, as do ProTaper Universal
carriers, which start at a .04 taper. Systems that do not use a
size verifier include the ProSystem GT carriers and GT Series
X carriers, which are made in a variety of tapers between 0.04
and 0.12.
Figure 13. Carrier and gutta-percha coating
Prefabricated obturators were introduced in 1988 (Thermafil)
using first a stainless steel and subsequently a titanium
core, coated with gutta-percha. Plastic obturators were first
offered in 1992. Since then, a number of prefabricated obturator
systems have been introduced, including one that does
not involve thermosoftening of the gutta-percha (SimpliFil,
Discus Dental) but instead is used cold with only the apical
area coated in gutta-percha, and after placement the carrier
itself is removed.
A recently developed prefabricated obturator utilizes a
resin-based system (RealSeal One, Sybron Endo) and is
used with, and bonded to, methacrylate resin-based sealer
material and is first held in its custom oven and thermosoftened.
Other systems use thermosoftened gutta-percha,
including Calamus® (Tulsa Dental, Dentsply) (Figure 12),
Successfil® (Hygienic-Coltene-Whaledent, Inc.), Gutta-
Flow ® , System B Obturation System, Thermafil, Thermafil
Carrier
gutta-percha
venting
The first case below shows a step-by-step procedure using
GT ® Series X obturation, and the second shows use of the
ProTaper ® Universal obturator.
Case 1. GT® Series X obturation
Following complete shaping and cleaning, the canals should
be thoroughly dried. For the obturator, the size matching the
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last instrument taken to working length should be selected
(Figure 14). It is vital that the calibration rings (measuring
marks) on the carrier are used as opposed to actually measuring
the obturator from the tip. There is more gutta-percha
than plastic carrier at the apical end of the obturator and it
is this gutta-percha that is intended to flow and fill the space
ahead of the plastic.
The plastic core delivers the gutta-percha to the full working
length. If necessary, for shorter canals, excess gutta-percha
should be peeled from the coronal end to facilitate setting of the
working length indicator. Additionally, if BioPure ® MTAD ® is
to be used in the canal space, it must be the last liquid irrigant
in the canal space and should therefore be incorporated after
checking the fit of the size verifiers.
A ProPost ® drill with an eccentric tip can be used to cut the
post channel through the obturator (note that most post drills
cannot efficiently cut a solid core obturator).
Figure 16. Placing sealant with a paper point
Figure 14. Working
length calibration
Figure 15. GT® Series X
obturator oven
Figure 17. Obturator at working length
The obturator is then heated in the GT (or GT® Series
X) obturator oven to ensure even heating of the gutta-percha
and consistent flow of the gutta-percha in the canal (Figure
15). During the heating process, sealer is placed in the canal
space. A non-eugenol sealer is recommended for use with
GT ® Series X obturators, with a thin coat applied using a
paper point (Figure 16). After placing the sealer, excess should
be blotted out with a paper point. It is critical that only a tiny
amount of sealer be used since increasing the amount of sealer
will predispose to material overextension beyond the confines
of the canal. The obturator is then placed in the canal with a
smooth motion until the rubber stopper touches the reference
point on the crown of the tooth, indicating it has reached working
length (Figure 17). It is important not to rotate the obturator
or to push it with excessive force into the canal. Prior to
cutting off the handle, the length and quality of the fill can be
confirmed with a radiograph. The handle of the obturator can
be cut off after several seconds of cooling of the gutta-percha
with a Prepi ® bur, a round bur, an ultrasonic tip, or a Touch
’n Heat instrument. If using a Prepi ® bur, water spray should
not be used as this would needlessly soak the pulp chamber
and any other open canals, thereby creating more work in
cleanup. Allow for the gutta-percha to cool back to a hard
consistency prior to making post space so that the obturator is
not dislodged by the post drill; therefore it is recommended to
wait five minutes after placement before cutting the obturator.
Figure 18. Finished case
Case 2. ProTaper® Universal/Thermafil® obturator
technique
The ProTaper ® and Thermafil ® Plus obturators are a solid
core of plastic covered in a layer of gutta-percha. As in the case
above, thorough drying and cleaning of the canals is required.
In this case, the obturator is selected using the size verifier to
ascertain the size required for a passive fit at working length in
the canal (Figures 19,20). For canals shorter than 18 mm, the
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carrier can be stripped back from 18 and the rubber stopper
repositioned, while for canals longer than 24 mm, the length
can be measured on the handle and part of the handle cut back
(taking care to preserve half of the handle length so that the
obturator can rest on the oven hanger arm). The obturator is
heated using the ProTaper ® Universal obturator oven, which
is designed specifically to guarantee full and uniform guttapercha
heating. A light coating of sealer should be placed to
the full working length of the root canal space, then the heated
obturator is placed in the canal with a smooth motion until the
rubber stopper touches the reference point on the crown of the
tooth, indicating it has reached working length. The obturator
should not be rotated or pushed into the canal with excessive
force. There is adequate time after taking the obturator out of
the oven to methodically place the gutta-percha without rushing.
The length and quality of the fill can be confirmed with
a radiograph prior to cutting off the handle using one of the
techniques described above in Case 1. Post space preparation
can occur after five minutes.
Figure 19. Working length indicators
Figure 20. Size verifier
Figure 21. Finished case
Summary
Appropriate cleaning and shaping of canals and obturation
with an apical and coronal seal are essential for successful
clinical outcomes in root canal therapy. While gutta-percha
cones, used together with a sealer/cement, may not meet all
criteria for the ideal root filling material, it has withstood the
test of time and is the standard material used for root canal
obturation. Contemporary techniques include the use of
gutta-percha carrier-based obturators as well as thermosoftened
syringed gutta-percha and mechanically softened guttapercha.
Other materials used include resin-based carriers
and sealers. For successful outcomes, the appropriate use of
the selected materials and techniques, radiographic control
during the different phases of endodontic therapy, and a high
degree of clinical expertise are required.
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36 Schwarze T et al. The cellular compatibility of five endodontic
sealers during the setting period. J Endod. 2002;28:784.
37 Layhausen G et al. Genotoxicity and cytotoxicity of the epoxy
resin-based root canal sealer AH plus. J Endod. 1999;25:109.
38 Hensten A, Jacobsen N. Allergic reactions in endodontic practice.
Endod Topics. 2005;12:44.
39 Dahl JE. Toxicity of endodontic filling materials. Endod Topics.
2005;12:39.
40 Huang TH et al. Root canal sealers induce cytotoxicity and
necrosis. J Mater Sci Mater Med. 2004;15:767.
41 Gluskin A. Mishaps and serious complications in endodontic
obturation. Endod Topics. 2005;12:52.
42 Ørstavik D. Materials used for root canal obturation: technical,
biological and clinical testing. Endod Topics. 2005;12:25.
43 Langeland K. Root canal sealants and pastes. Dent Clin North
Am. 1974;18:309.
44 Holland R, de Souza V. Ability of a new calcium hydroxide root
canal filling material to induce hard tissue formation. J Endod.
1985;11:535.
45 Kontakiotis E, Panopoulos P. pH of root canal sealers containing
calcium hydroxide. Int Endod J. 1996;29:202.
46 Zmener O, Pameijer CH. Clinical and radiographical evaluation
of a resin-based root canal sealer: a 5-year follow-up. J Endod.
2007;33:676-9.
47 Ørstavik D. Materials used for root canal obturation: technical,
biological and clinical testing. Endod Topics. 2005;12:25.
48 Barbosa SV, Burkard DH, Spångberg LSW. Cytotoxic effects of
gutta-percha solvents. J Endod. 1994;20:6.
49 Metzger Z et al. Residual chloroform and plasticity in customized
gutta-percha master cones. J Endod. 1988;14:546.
50 Wong M, Peters DB, Lorton L. Comparison of gutta-percha filling
techniques: three chloroform gutta-percha filling techniques: part
2. J Endod. 1982;8:4.
51 Gutmann JL, Heaton JF. Management of the open (immature)
apex. II. Non-vital teeth. Int Endod J. 1981;14:173.
52 Gutmann JL, Dumsha TC, Lovdahl PE. Problems in root canal
obturation. Problem solving in endodontics. 4th edition, St Louis,
Elsevier-Mosby, 2006.
53 Kaplowitz GJ. Evaluation of gutta-percha solvents. J Endod.
1990;16:539.
54 Haas SB et al. A comparison of four root canal filling techniques.
J Endod. 1989;15:596.
55 Keane K, Harrington GW. The use of a chloroform-softened
gutta-percha master cone and its effect on the apical seal. J
Endod. 1984;10:57.
56 McDonald NM, Vire DE. Chloroform in the endodontic
operatory. J Endod. 1992;18:301.
57 Metzger Z et al. Apical seal by customized versus standardized
master cones: a comparative study in flat and round canals. J
Endod. 1988;14:381.
58 Friedman CE, Sandrik JL, Heuer MA, Rapp GW. Composition
and mechanical properties of gutta-percha endodontic points. J
Dent Res. 1975;54:921.
59 Moorer WR, Genet JM. Antibacterial activity of gutta-percha
cones attributed to the zinc oxide component. Oral Surg Oral
Med Oral Pathol Oral Radiol Endod. 1982;53:508.
60 Moorer WR, Genet JM. Evidence for antibacterial activity of
endodontic gutta-percha cones, Oral Surg Oral Med Oral Pathol
Oral Radiol Endod. 1982;53:503.
61 Whitworth J. Methods of filling root canals: principles and
practices. Endod Topics. 2005;12:2.
62 Gutmann JL, Dumsha TC, Lovdahl PE. Problem solving in
endodontics. 4th edition, St Louis, Elsevier-Mosby, 2006.
63 Ibid.
64 Kuttler Y. Microscopic investigation of root apexes. J Am Dent
Assoc. 1955;50(5):544–52.
65 Grove CJ. Why root canals should be filled to the dentinocemental
junction. J Am Dent Assoc. 1930;17:293.
66 Wu M-K, Wesselink PR, Walton RE. Apical terminus location of
root canal treatment procedures. Oral Surg Oral Med Oral Pathol
Oral Radiol Endod. 2000;89:99.
67 Orban B. Why root canals should be filled to the dentinocemental
junction. J Am Dent Assoc. 1930;7:1086.
68 Seltzer S, Bender IB, Turkenkopf S. Factors affecting successful
repair after root canal therapy. J Am Dent Assoc. 1963;67:651.
69 Hasselgren G. Where shall the root filling end? NY State Dent J.
1994;60(6):34.
70 Grahnén H, Hansson L. The prognosis of pulp and root canal
therapy: a clinical and radiographic follow-up examination,
Odontol Revy. 1961;12:146.
71 Seltzer S, Naidorf I. Flare-ups in endodontics. II. Therapeutic
measures. J Endod. 1985;11:559.
72 Sjögren U, Hägglund B, Sundqvist G, Wing K. Factors affecting
the long-term results of endodontic treatment. J Endod.
1990;16:498.
73 Swartz DB, Skidmore AE, Griffin JA. Twenty years of endodontic
success and failure. J Endod. 1983;9:198.
74 Gutmann JL, Leonard JE. Problem solving in endodontic working
length determination. Comp Contin Educ Dent. 1995;16:288.
75 Seltzer S. Endodontology: biologic considerations in endodontic
procedures. 2nd edition, Philadelphia, Lea & Febiger. 1998.
76 Budd CS, Weller RN, Kulild JC. A comparison of
thermoplasticized injectable gutta-percha obturation techniques.
J Endod. 1991;17:260.
77 Gutmann JL. Adaptation of injected thermoplasticized guttapercha
in the absence of the dentinal smear layer. Int Endod J.
1993;26:87.
78 Wu MK, Shemesh H, Wesselink PR. Limitations of previously
published systematic reviews evaluating the outcome of
endodontic treatment. Int Endod J. 2009;42(8):656-66. Epub
2009 Jun 22.
79 Johnson, WB. A new gutta-percha technique. J Endod.
1978;4(60):184-8.
80 Foong W, Sutow E, Zakariasen K, Hidi P, Jones D. Cytotoxicity
testing of an endodontic obturating device. J Endod. 1993;19
(Abstract 74):202.
Author Profile
The authors of this course, James L. Gutmann, DDS,
Sergio Kuttler, DDS and Stephen P. Niemczyk, DMD,
are all board-certified endodontists.
www.ineedce.com 9

Online Completion
Use this page to review the questions and answers. Return to www.ineedce.com and sign in. If you have not previously purchased the program select it from the “Online Courses” listing and complete the
online purchase. Once purchased the exam will be added to your Archives page where a Take Exam link will be provided. Click on the “Take Exam” link, complete all the program questions and submit your
answers. An immediate grade report will be provided and upon receiving a passing grade your “Verification Form” will be provided immediately for viewing and/or printing. Verification Forms can be viewed
and/or printed anytime in the future by returning to the site, sign in and return to your Archives Page.
Questions
1. The purpose of root canal obturation is
_________.
a. the elimination of all avenues of leakage
b. the introduction of a medicament
c. sealing within the root canal system of any irritants
that remain after appropriate shaping and cleaning
of the canals, thereby isolating these irritants
d. a and c
2. Pulpal demise and subsequent periradicular
infection result from _________.
a. the presence of microorganisms
b. the products of pulp tissue degradation
c. the presence of microbial toxins and metabolites
d. all of the above
3. The ability to achieve three-dimensional
root canal obturation is primarily
dependent on _________.
a. clinical skill
b. the quality of canal cleaning and shaping
c. the material
d. a and b
4. There is reasonable evidence that
_________is a final determinant of success
or failure in treatment.
a. coronal leakage through improperly placed restorations
after root canal treatment
b. failure of the restorative treatment
c. lack of health of the supporting periodontium
d. all of the above
5. _________ should be used in conjunction
with the core filling material to establish
an adequate seal.
a. Maximum amounts of root canal sealers
b. Minimum amounts of root canal sealers
c. Maximum amounts of periodontal sealers
d. none of the above
6. ________ enables standard-of-care canal
obturation.
a. Gutta percha alone
b. Sealer alone
c. Cement alone
d. none of the above
7. A disadvantage of gutta-percha is
_________.
a. its ease of displacement under pressure
b. its lack of rigidity
c. its adhesiveness
d. all of the above
8. To be able to manage the diversity
of anatomical scenarios that may be
encountered, _________.
a. the clinician should completely master one obturation
technique
b. it is recommended that the clinician master several
obturation techniques
c. scans are required
d. all of the above
9. Use of a sealant is _________.
a. rarely required
b. only required if the obturator is not thermoplastic
c. always required
d. none of the above
10. Root canal sealers can _________.
a. enhance the possible attainment of an impervious seal
b. serve as a filler for root canal irregularities
c. assist in microbial control should there be
microorganisms left on the root canal walls or in the
tubules
d. all of the above
11. In canals in which the smear layer has
been removed, _________ to dentin.
a. many sealers demonstrate reduced adhesive
properties
b. many sealers demonstrate increased adhesive
properties
c. no sealers demonstrate adhesive properties
d. none of the above
12. The toxicity of sealers _________.
a. is reduced on setting
b. is increased on setting
c. remains the same on setting
d. none of the above
13. One sealer/cement combination
discussed in the article is _________.
a. zinc oxide eugenol
b. polyketone
c. calcium hydroxide
d. all of the above
14. Epoxy-based and methacrylate-based
resin sealers _________.
a. can be bonded to the root canal dentin
b. can never be bonded to the root canal dentin
c. weaken the root canal dentin
d. none of the above
15. Bonding to gutta-percha can be achieved
using _________.
a. epoxy-based resins
b. methacrylate-based resin sealers
c. glass ionomer-based resin sealers
d. none of the above
16. Gutta-percha as a solid core filling material
for canal obturation _________.
a. demonstrates minimal toxicity
b. demonstrates minimal tissue irritability
c. is the least allergenic material available when
retained within the canal system
d. all of the above
17. _________ is a chemical solvent that has
been used with gutta-percha.
a. Rectified black turpentine
b. Chloroform
c. Water
d. all of the above
18. The use of solvents _________ in daily
practice.
a. may still be considered for a number of challenges
the clinician may face
b. must always be considered
c. should never be considered
d. is no longer a viable treatment
19. The composition of gutta-percha cones is
approximately _________ and _________.
a. 19% to 32% Balata; 59% to 85% zinc oxide
b. 19% to 32% zinc oxide; 59% to 85% Balata
c. 19% to 22% Balata; 59% to 75% zinc oxide
d. none of the above
20. With the development of more predictable
root canal shapes prepared with
current nickel titanium (NiTi) rotary and
hand instruments, cones tapered from
_________ have gained use.
a. 1% – 3%
b. 2% – 4%
c. 4% – 8%
d. 4% – 10%
21. Basic techniques for the obturation of
the root canal system with gutta-percha
and sealer include _________.
a. cold compaction or heat-softened compaction using
cold instruments
b. compaction of gutta-percha that has been
thermoplasticized, injected into the system, and
compacted with cold instruments
c. compaction of gutta-percha that has first been
placed in the canal and then softened
d. all of the above
22. While softening of gutta-percha may be
viewed as _________, the selective use of
this technique solely or in combination
with a solid core of gutta-percha must
be at the discretion of the competent
clinician.
a. rarely desirable
b. routinely desirable
c. never desirable
d. none of the above
23. Resin-based cones are available that can
be used with a _________.
a. lateral compaction technique only
b. vertical compaction technique only
c. diagonally-positioned compaction technique only
d. vertical or lateral compaction technique
24. It is important to avoid using any
dessicating solutions, such as _________,
during root canal preparation if using
resin-based obturating materials.
a. water
b. eugenol
c. alcohol
d. b and c
25. Prefabricated obturators were first
described in 1978 by _________.
a. William Ben Thompson
b. Ben William Thompson
c. William Ben Johnson
d. Ben William Johnson
26. _________ are currently available.
a. Gutta-percha-based and resin-based prefabricated
obturators
b. Gutta-percha-based and cement-based prefabricated
obturators
c. Gutta-percha-based and sealer-based prefabricated
obturators
d. all of the above
27. Current tapered plastic obturators are
available in _________ shapes.
a. nonvented
b. vented
c. helical
d. a and b
28. A vented prefabricated obturator
_________.
a. helps the flow of gutta-percha during placement
b. helps the flow of gutta-percha after placement
c. aids in retrieval of the obturator should retreatment
be necessary
d. a and c
29. With a gutta-percha-based prefabricated
carrier, if BioPure ® MTAD ® is to be
used in the canal space, it should be the
_________ liquid irrigant used in the canal
space prior to checking the fit of the size
verifiers.
a. first
b. intermediate
c. last
d. none of the above
30. _________ control during the different
phases of endodontic therapy is required.
a. Digital
b. Radiographic
c. Ergometric
d. all of the above
10 www.ineedce.com

ANSWER SHEET
Root Canal Obturation: An Update
Name: Title: Specialty:
Address:
E-mail:
City: State: ZIP: Country:
Telephone: Home ( ) ( ) Lic. Renewal Date:
Requirements for successful completion of the course and to obtain dental continuing education credits: 1) Read the entire course. 2) Complete all
information above. 3) Complete answer sheets in either pen or pencil. 4) Mark only one answer for each question. 5) A score of 70% on this test will earn
you 2 CE credits. 6) Complete the Course Evaluation below. For Questions call 216.398.7822
Educational Objectives
1. List the purposes of root canal obturation
2. List the characteristics of gutta-percha used for obturation
3. List and describe the contemporary materials and techniques for obturating root canals
4. List the most widely-used techniques for gutta-percha carrier-based obturation and describe its strengths and
shortcomings.
Course Evaluation
Please evaluate this course by responding to the following statements, using a scale of Excellent = 5 to Poor = 0.
If not taking online, mail completed answer sheet to
Academy of Dental Therapeutics and Stomatology,
A Division of PennWell Corp.
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Answer sheets can be faxed to
(440) 845-3447, (216) 398-7922, or (216) 255-6619.
1. Were the individual course objectives met? Objective #1: Yes No Objective #3: Yes No
Objective #2: Yes No Objective #4: Yes No
2. To what extent were the course objectives accomplished overall? 5 4 3 2 1 0
3. Please rate your personal mastery of the course objectives. 5 4 3 2 1 0
4. How would you rate the objectives and educational methods? 5 4 3 2 1 0
5. How do you rate the author’s grasp of the topic? 5 4 3 2 1 0
5 4 3 2 1 0
5 4 3 2 1 0
8. Do you feel that the references were adequate? Yes No
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No
10. If any of the continuing education questions were unclear or ambiguous, please list them.
___________________________________________________________________
11. Was there any subject matter you found confusing? Please describe.
___________________________________________________________________
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12. What additional continuing dental education topics would you like to see?
___________________________________________________________________
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AGD Code 074
PLEASE PHOTOCOPY ANSWER SHEET FOR ADDITIONAL PARTICIPANTS.
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INSTRUCTIONS
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EDUCATIONAL DISCLAIMER
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2
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