roots C.E. No. 1, 2012

Cover / Editorial / Content / The antibacterial effects of lasers in endodontics / Positive versus negative pressure irrigation / Negotiating and shaping around anatomic root canal impediments / The rules of engagement / Lasers in endodontics / 9000 3D extraoral imaging system / Submissions / Imprint

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roots
issn 2161-6558

the international C.E. magazine of

1

2012

_C.E. article

The antibacterial effects
of lasers in endodontics

_technique

Positive versus negative
pressure irrigation

_technique

Negotiating and shaping
around impediments

North America Edition • Vol. 2 • Issue 1/2012

endodontics

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editorial _ roots

A new year brings
new opportunities
_The amount of information available in the dental field about new products, techniques
and research data is astounding. Running a practice and seeing patients leaves little time for
catching up on the latest clinical news and product information. Thus, I hope roots will not only be
a welcome respite for those rare chunks of time you can devote to leisurely reading, but one that
provides a practical return on your investment by giving you information that you can actually put
to immediate use.
This issue of roots features a collection of articles from some of the most respected names in
endodontics. These expert clinicians are sharing their knowledge and expertise with you.
Within this issue, Dr. Gregori M. Kurtzman describes positive versus negative pressure irrigation; Dr. L. Stephen Buchanan writes about negotiating and shaping around anatomic impediments; and Dr. Barry Lee Musikant shares his perspective on “the rules of engagement.” In
addition, Dr. Enrico DiVito, Prof. Rolando Crippa, Prof. Giuseppe Iaria, Prof. Vasilios Kaitsas, Prof.
Stefano Benedicenti and Prof. Giovanni Olivi share the latest information on the use of lasers in
endodontics.
But there’s more.
Every issue of roots also contains a C.E. component. By reading the article on the antibacterial
effects of lasers in endodontics by Dr. Selma Cristina Cury Camargo, then taking a short online quiz
about this article at www.DTStudyClub.com, you will gain one ADA CERP-certified C.E. credit. Keep
in mind that since roots is a quarterly magazine, you can actually chisel four C.E. credits per year out
of your already busy life without the lost revenue and time away from your practice.
To learn more about how you can take advantage of this C.E. opportunity, visit www.DTStudyClub.
com. Annual subscribers to the magazine ($50) need only register at the Dental Tribune Study Club
website to access these C.E. materials free of charge. Non-subscribers may take the C.E. quiz after
registering on the DT Study Club website and paying a nominal fee.
I know that taking time away from your practice to pursue C.E. credits is costly in terms of lost
revenue and time, and that is another reason roots is such a valuable publication.
I hope you enjoy this issue and that you get the most out of it.
And, for those who will be attending the AAE Annual Session in Boston this spring, please say
hello to me there.

Fred Weinstein, DMD, MRCD(C), FICD

Sincerely,
Fred Weinstein, DMD, MRCD(C), FICD
Editor in Chief

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I content _ roots

page 16

page 08

page 24

I C.E. article
08	The antibacterial effects of lasers in endodontics
_Selma Cristina Cury Camargo, DDS, PhD

I technique
16	Positive versus negative pressure irrigation
_Gregori M. Kurtzman, DDS

24	Negotiating and shaping around anatomic
root canal impediments
_L. Stephen Buchanan, DDS, FICD, FACD

I trends
32	The rules of engagement
_Barry Lee Musikant, DMD

38	Lasers in endodontics

roots

North America Edition • Vol. 2 • Issue 1/2012

issn 2161-6558

the international C.E. magazine of

1

endodontology

2012

_Enrico DiVito, DDS, Prof. Rolando Crippa,
Prof. Giuseppe Iaria, Prof. Vasilios Kaitsas,
Prof. Stefano Benedicenti & Prof. Giovanni Olivi

I industry

_C.E. article

46	9000 3D extraoral imaging system

Positive versus negative
pressure irrigation

The antibacterial effects
of lasers in endodontics

I on the cover

_submissions
_imprint

Image courtesy of Dr. Eric Hebranson,
eHuman.com.

page 32

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_technique

Negotiating and shaping
around impediments

I about the publisher
49
50

_technique

page 38

page 46

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I C.E. article_lasers in endodontics

The antibacterial
effects of lasers
in endodontics
Author_Selma Cristina Cury Camargo, DDS, PhD

_c.e. credit

_Endodontic infection

This article qualifies for
C.E. credit. To take the
C.E. quiz, log on to www.
dtstudyclub.com. The
quiz will be available on
April 6.

The success of endodontic treatment reaches
values between 85 to 97 percent.1 Adequate treatment protocols, knowledge and infection control
are the basic components to achieve such values2
(Fig. 1). It is well known that apical periodontitis
is caused by the communication of root-canal
microorganisms and their byproducts with the
surrounding periodontal structures. Exposure of
dental pulp directly to the oral cavity, or via acces-

Fig. 1_Success in
endodontic treatment: apical
radiolucency repair.

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sory canals, open dentinal tubules or periodontal
pockets, are the most probable routes of the endodontic infection.2,3
Clinically, apical periodontitis is not evident
as long as the necrotic tissue is not infected with
microorganisms.4–6 There are up to 40 isolated
species of bacteria present in the root canal.
Cocci, rods, filaments, spirochetes, anaerobic
and facultative anaerobic are frequently identified in primary infection, fungus can also be
isolated. 2,7

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C.E. article_lasers in endodontics

Endodontic microbiota can be found suspended
in the main root canal, adhered to the canal walls
and deep in the dentinal tubules at a depth of up to
300 µm (Fig. 2). The absence of cementun dramatically increases bacteria penetration into dentinal
tubules.8–11
It has been shown that bacteria can also be
found outside the root-canal system, located at the
apical cementum and as an external biofilm on the
apex.12–15 Following conventional endodontic treatment, 15 to 20 percent of non-vital teeth with apical
periodontitis fail.16–18
The presence of bacteria after the decontamination phase or the inability to seal root canal after
treatment are reasons for failure.2 The remaining
contamination in endodontically treated teeth is
able to maintain the infectious disease process in
the periapical tissue.
Retreatments are the first choice in failed root
canals. The microbiota found in persistent infections differs from that in primary infection (Fig.
3). Facultative anaerobic gram positive (G+) and
negative (G-) microorganisms and fungus are easily
found.19–21 Special attention is given to Enterococus
faecalis, a resistant facultative anaerobic G+ cocci,
identified in a much higher incidence in failed root
canals.22–25
The importance of bacterial control plays a significant role in endodontic success. Adequate and
effective disinfection of the root-canal system is
necessary. Based on that, all efforts must be done in
order to achieve this result.

Fig. 2

_Endodontic therapy
The bacterial flora of the root canal must be actively eliminated by a combination of debridement
and antimicrobial chemical treatment. Mechanical
instrumentation eliminates more than 90 percent
of the microbial amount.26
An important point of note is the adequate
shaping of the root canal. Evaluating the antibacterial efficacy of mechanical preparation
itself, Dalton et al.27 concluded that instrumentation to an apical size of #25 resulted in
20 percent of canals free of cultivable bacteria,
when a #35 size was made, 60 percent showed
negative results.
Irrigant solution has been associated with
mechanical instrumentation to facilitate an instrument’s cutting efficiency, remove debris and
the smear layer, dissolute organic matter, clean
inaccessible areas and act against microorganisms. Sodium hypochlorite is the most common
irrigant used in endodontics.28 It has an excellent
cleansing ability, dissolves necrotic tissue, has a
potential antibacterial effect and, depending on

Fig. 3

the concentration, is well tolerated by biological
tissues. When added to mechanical instrumentation, it reduces the number of infected canals by
40 to 50 percent.
Other irrigant solutions are also used during endodontic preparation. EDTA, a chelating agent used
primarily to remove the smear layer and facilitate the
removal of debris from the canal has no antibacterial
effect.29 Chlorhexidine gluconate has a strong antibacterial activity to an extensive number of bacteria
species, even the resistant Enterococus faecalis, but
it does not break down proteins and necrotic tissue
as sodium hypochlorite does.30

Fig. 2_Primary infection of black
pigmented strains and G-rods.
Fig. 3_Persistent infection.

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I C.E. article_lasers in endodontics
The principal goal of dressing the root canal
between appointments is to ensure safe antibacterial action with a long-lasting effect. 31 A
great number of medicaments have been used
as dressing material, such as formocresol, camphorated parachlorophenol, eugenol, iodinepotassium iodide, antibiotics, calcium hydroxide
and chlorhexidine.
Calcium hydroxide has been used in endodontic
therapy since 1920.31 With a high pH at saturation
over pH 11, it induces mineralization, reduces bacteria and dissolves tissue. For extended antibacterial
effectiveness, the pH must be kept high in the canal
and in the dentin as well. This ability depends on the
diffusion through dentin tubules.32
Although most microorganisms are destroyed at
pH 9.5, a few can survive over pH 11 or higher, such as
E. faecalis and candida.21 Because of the resistance
of some microorganisms to conventional treatment protocols — and the direct relation between
the presence of viable bacteria in the canal system
and the reduced percentage of treatment success
— additional effort has to be made to control canal
system infection.

Fig. 4a, 4b_The Nd:YAG laser
intra-canal irradiation.

_Lasers in endodontics

Fig. 4a

Lasers were introduced in endodontics as a complementary step to increase antibacterial efforts in
conventional treatments. The antibacterial action
of Nd:YAG, diodes, Er:YAG and photo activated
disinfection (PAD) have been explored by a number
of investigators. In the following section, each laser
is evaluated with the aim of selecting an adequate
protocol that will result in a high probability of success in teeth with apical periodontitis.

_Nd:YAG laser

Fig. 4b

Because the association of mechanical instrumentation and irrigant solutions are not
able to totally eliminate bacteria from the canal
system — a status that is required for root-canal
filling — additional substances and medicaments have been tested in order to suppress
the gap that occurs in standard endodontic
protocols.

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The Nd:YAG laser was one of the first lasers tested
in endodontics. It is a solid-state laser. The active
medium is usually YAG- yitrum aluminin grenade
(Y2AL5O12) where some Y3+ are substituted for
Nd3+. It is a four-level energy system operating in
a continuous or pulsed mode. It emits a 1064 nm
infrared wavelength. Thus, this laser needs a guide
light for clinical application. Flexible fibers with a
diameter between 200 mm and 400 µm are used as
delivery systems. It can be used intra canal, in contact
mode (Fig. 4).
The typical morphology of root-canal walls
treated with the Nd:YAG laser show melted dentin
with a globular and glassy appearance and few
areas are covered by a smear layer. Some areas
show dentinal tubules sealed by fusion of the
dentin and deposits of mineral components.33,34
This morphologic modification reduces dentin

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C.E. article_lasers in endodontics

permeability significantly.35,36 However, because
the emission of the laser beam from the optical
fiber is directed along the root canal, not laterally,
not all root canal walls are irradiated, which gives
more effective action at the apical areas of the
root.37 Undesirable morphologic changes such
as carbonization and cracks are seen only if high
parameters of energy are used.
One of the major problems for intra-canal laser
irradiation is the increase of temperature at the external surface of the root. When laser light reaches a
tissue, a thermal effect occurs. The heat is directly associated to energy used, time and irradiation mode.
An increase in temperature levels more than 10
degrees Celsius per one minute can cause damage to
periodontal tissues, such as necrosis and anquilose.
Lan (1999)38 evaluated in vitro, the temperature
increase on the external surface of the root after
irradiation with a Nd:YAG laser under the following
parameters of energy: 50 mJ, 80 mJ and 100 mJ at
10, 20 and 30 pulses per second. The increase of temperature was less than 10 degrees. The same results
were obtained from Bachman et al. (2000)39, Kimura
et al. (1999)40, Gutknecht et al. (2008).41
In contrast to the external surface, intra-canal
temperature rises dramatically at the apical area,
promoting an effective action against bacteria contamination. For the Nd:YAG laser, 1.5 watts and 15
Hz are safe parameters of energy for temperature
and morphological changes.33,41
The primary use of the Nd:YAG laser in endodontics is focused on elimination of microorganisms
in the root canal system. Rooney et al. (1994)42
evaluated the antibacterial effect of Nd:YAG lasers in
vitro. Bacterial reduction was obtained considering
energy parameters.
Researchers developed different in vitro models
simulating the organisms expected in non-vital,
contaminated teeth. Nd:YAG irradiation was effective for Baccilus stearothermophilus43,44, Streptococcus faecalis, Escherichia coli45, Streptococcus
mutans46, Streptococcus sanguis, Prevotella intermedia47 and a specific microorganism resistant to
conventional endodontic treatment, Enterococcus
faecalis.48–50 Nd:YAG has an antibacterial effect in
dentin at a depth of 1000 µm50 (Fig. 5).
Histological models were also developed in order
to evaluate periapical tissue response after intracanal Nd:YAG laser irradiation. Suda et al. (1996)51
proved in dog models that Nd:YAG irradiation that
100 mJ/30 pps (pulses per second) during 30 seconds
was safe to surrounding root tissues. Maresca et al.
(1996)52, using human teeth indicated for apical
surgery, confirmed Suda et al.51 and Ianamoto et al.
(1998)53 results. Koba et al. (1999)54 analyzed histopathological inflammatory response after Nd:YAG
irradiation in dogs using 1 watt and 2 watts. Results

Fig. 5

showed significant inflammatory reduction in four
and eight weeks compared to the non-irradiated
group.
Clinical reports published in the literature confirm the benefits of intra-canal Nd:YAG irradiation.
In 1993, Eduardo et al.55 published a successfully
clinical case that associated conventional endodontic treatment with Nd:YAG irradiation for retreatment, apical periodontitis, acute abscess and perforation. Clinical and radiographic follow up showed
complete healing after six months.
Similar results were shown by Camargo et al.
(1998).56 Gutknecht et al. (1996)57 reported a significant improvement in healing of laser-treated
infected canals, when compared to non-irradiated
cases.
Camargo et al. (2002)58 compared in vivo the
antibacterial effects of conventional endodontic
treatment and conventional protocol associated to
the Nd:YAG laser. Teeth with apical radiolucency,
no symptoms and necrotic pulps were selected and
divided into two groups: conventional treatment
and laser irradiated.
Microbiological samples were taken before canal
instrumentation, after canal preparation and/or laser irradiation and one week after treatment. Results
showed a significant antibacterial effect in the laser
group compared to the standard protocol. When no
other bactericidal agent was used, it is assumed that
the Nd:YAG laser played a specific role in bacterial
reduction for endodontic treatment in patients.

Fig. 5_Nd:YAG laser irradiation,
deep penetration.

_Diodes
The diode laser is a solid-state semiconductor
laser that uses a combination of galium, arsenide,

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I C.E. article_lasers in endodontics
Figs. 6a, 6b_Diode 980
nm intra-canal irradiation.
Fig. 7_Er:YAG laser.

Fig. 6a

Fig. 6b

aluminum and/or indium as the active medium. The
available wavelength for dental use ranges between
800 and 1064 nm that emits in continuous and gated
pulsed mode using an optical fiber as the delivery
system (Fig. 6).
Diode lasers have gained increasing importance
in dentistry due to their compactness and affordable cost. A combination of smear layer removal,
bacterial reduction and less apical leakage brings
importance to this system and makes it viable for
endodontic treatment. The principal laser action is
photothermal.
The thermal effect on tissue depends on the irradiation mode and settings. Wang et al. (2005)59
irradiated root canals in vitro and demonstrated a
maximum temperature increase of 8.1 degrees Celsius using 5 watt for seven seconds. Similar results
were obtained by da Costa Ribeiro.60
Gutknecht et al. (2005) 61 evaluated intracanal diode irradiation with an output set of 1.5
watts observed a temperature increase in the
external surface of the root of 7 degrees Celsius
with 980 nm of diode irradiation at a power setting of 2.5 watts at a continuous and chopped
mode and demonstrated that the temperature
increase never exceeded 47 degrees Celsius,
which is considered safe for periodontal structures.41
Clean intra-canal dentin surfaces with closed
dentinal tubules, indicating melting and recrystallization, were morphological changes observed at
the apical portion of the root after intra-canal diode
irradiation.62 In general, near infrared wavelengths,
such as 1064 nm and 980 nm, promote fusion and
recrystallization on the dentin surface, closing dentinal tubules.
The apparent consensus is that diode laser irradiation has a potential antibacterial effect. In most
cases, the effect is directly related to the amount of
energy delivered.
In a comparative study designed by Gutknecht
et al. (1997)63, an 810 nm diode was able to reduce
bacteria contamination up to 88.38 percent with a
distal output of 0.6 watts in CW mode.
A 980 nm diode laser has an efficient antibacterial effect in root canals contaminated with
Enterocous faecalis at an average between 77
to 97 percent. Energy outputs of 1.7 watts, 2.3
watts and 2.8 watts were tested. Efficiency was
directly related to the amount of energy and
dentin thickness.64

_Er:YAG laser

Fig. 7

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Er:YAG lasers are solid-state lasers whose lasing medium is erbium-doped yttrium aluminium
garnet (Er:Y3Al5O12). Er:YAG lasers typically

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C.E. article_lasers in endodontics

emit light with a wavelength of 2940 nm, which
is infrared light. Unlike Nd:YAG lasers, the output
of an Er:YAG laser is strongly absorbed by water
because of atomic resonances. The Er:YAG wavelength is well absorbed by hard dental tissue.
This laser was approved for dental procedures
in 1997. Smear layer removal, canal preparation
and apicoectomy are the indications for endodontics (Fig. 7).
The morphology of dentinal surface irradiated
with an Er:YAG laser is characterized by clean
areas showing opened dentinal tubules free of
smear layer in a globular surface. The effects
on bacterial reduction by Er:YAG was observed
by Moritz et al. (1999).65 Stabholz et al. (2003)37
described a new endodontic tip that can be used
with an Er:YAG laser system.
The tip allows lateral emission of the radiation rather than direct emission through a single
opening at the far end. It emits through a spiral
tip located along the length of the tip. In order to
examine the efficacy of the spiral tip in removing smear layer, Stabhols et al. (2003)66 showed
cleaned intra-canal dentin walls free of smear
layer and debris under SEM evaluation.

Fig. 8

_Photo activated disinfection (PAD)
Another method of disinfection in endodontics is also available. Photo activated disinfection (PAD) is based on the principle that
photo-activatable substances that bind to the
target cells and are activated by light of suitable
wavelength. Free radicals are formed, producing a toxic effect to bacteria. Toluidine blue and
methylene blue are examples of photo-activatable substances.
Tolonium chloride is able to kill most of the
existing bacteria. In vitro studies, PAD has an
effective action against photosensitive bacteria
such as E. faecalis, Fusobacterium nucleatum,
Prevotella intermedia, Peptostreptococcus micros and Actinomycetemcomitans.67,68
On the other hand, Souza et al. (2010) 69,
evaluating PAD antibacterial effects as a supplement to instrumentation / irrigation in infected
canals with E faecalis, did not prove significant effect regards to intra-canal disinfection.
Further adjustments in the PAD protocols and
comparative research models may be required to
before clinical usage recommendations.

Discussion and conclusion
There are good reasons to focus the treatment
of non-vital contaminated teeth upon the destruction of bacteria in the root canal. The chances for a

Fig. 9

favorable outcome of the treatment are significantly
higher if the canal is free from bacteria when it is
obturated.
If, on the other hand, bacteria persist at the
time of root filling, there is a higher risk of
failure treatment. Therefore, the prime objective of treatment is to achieve the complete
elimination of all bacteria from the root canal
system. 2,31
Today, the potential antibacterial effect of laser
irradiation associated with the bio-stimulation action and accelerated healing process is well known.
Research has supported the improvement of endodontic protocol.

Fig. 8_Endodontic laser
therapeutic plan.
Fig. 9_Intra-canal laser
irradiation, molars.

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I C.E. article_lasers in endodontics
Fig. 10_Intra-canal laser
irradiation technique.

Fig. 10

An endodontic laser therapeutic plan brings
benefits to conventional treatment, such as minimal
apical leakage, effective action against resistant
microorganisms and on external apical biofilm,
and an increase in periapical tissue repair. Based
on that, laser procedures have been incorporated
into conventional therapeutic concepts to improve
endodontic therapy (Fig. 8).
Clinical studies have shown the benefits of
an endo-laser protocol in apical periodontitis
treatment. For endodontic treatment, laser protocol is a combination of standard treatment
strategies associating cleaning and shaping
the root canal with a minimal adequate shape
up to #35, irrigant solutions with antibacterial
properties and intra-canal laser irradiation
using controlled parameters of energy. Ideal
sealing of the root canal and adequate coronal
restoration are needed for an optimal result.
In practice, little additional time is required for
laser treatment. Irradiation technique is simple
once flexible optical fibers of 200 µm in diameter
are used. The fiber can easily reach the apical third
of the root canal, even in curved molars (Fig. 9).
The released laser energy has an effect in dentin
layers and beyond the apex in the periapical
region. The laser’s effect is applicable in inaccessible areas, such as external biofilm adhered at
the root apex.
Irradiation technique must follow basic principles. A humid root canal is required and rotary
movements from the coronal portion to the apex
should be carried out, as well as scanning the root
canal walls in contact mode (Fig. 10). The power set-

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tings and irradiation mode depend on one’s choice
of a specific wavelength.
Nd:YAG, diodes in different wavelength emissions, Er:YAG, Er:CrYSGG and low-power lasers can
be used for different procedures with acceptable
results. Laser technology in dentistry is a reality. The
development of specific delivery systems and the
evolution of lasers combined with a better understanding of laser-tissue interaction increase the opportunities and indications in the endodontic field._
Editorial note: This article was first published in
the international edition of laser, issue 2/2011. A list
of references is available from the publisher.

_about the author

roots

Selma Camargo, DDS, Phd,
received a doctorate in
endodontics, a specialist
and master’s degree and a
laser in dentistry unit from
the University of Cidade de
São Paulo, Brazil. She is a
professor of endodontics
and general dentistry at
the University of Cidade
de São Paulo, Brazil. She
conducted research in endodontics (master’s) at the
University of British Columbia, Vancouver, Canada;
and research in endodontics (PhD) at University of
Oslo, Norway. She may be contacted at University of
Cidade de São Paulo, Brazil, Rua Pinto Gonçalves,
85/54 Perdizes, São Paulo, SP Brazil 05005-010,
selmacris@me.com.

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I technique_disinfection

Positive versus negative
pressure irrigation
Author_Gregori M. Kurtzman, DDS, MAGD, FACD, FPFA, FADI, DICOI, DADIA

_The endodontic triad
Long-term endodontic success is not due to
a single factor but is dependent upon three critical
aspects of treatment called the “endodontic triad”
— instrumentation, disinfection and obturation.
These three components of the triad are interwoven,
and success requires careful attention to all three to
provide long term-clinical success.
Teeth have very complex pulpal anatomy, and

instrumentation alone cannot adequately prepare
the canal system for obturation. The intricacies of the
canal anatomy with its fins, lateral canals and apical
deltas make it impossible for endodontic instruments
to reach all aspects of the anatomy (Fig. 1). Thus irrigation is critical for removal of residual tissue and
microbiota that cannot be reached by instrumentation of the main canals.
Regardless of the file system used for instrumentation, files cannot reach all of the pulpal anatomy,
and therefore disinfection is key to augmenting
the cleaning process prior to obturation. But what
is referred to when we mention disinfection of the
canal system? Disinfection comprises removal of the
residual tissue in the canal system and the associated
bacteria through flushing the canal system with irrigating solution. The key being to remove as much
residual tissue as possible and the more thorough the
irrigation process the lower the remaining bacterial
level. The less residual tissue remaining the less bacteria and the more successful the clinical outcome of
the endodontic treatment.

_Cleaning the canal

Fig. 1_Cleared molar
with dye within the
canal system illustrating
the complex anatomy
normally found in teeth.
(Photos/Provided by
Dr. Gregori M. Kurtzman)

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Fig. 1

No matter what obturation material is used, how
well the sealer adheres to the canal walls is important.
Smear layer can play a factor that may prevent sealer
penetration into the dentinal tubules. The frequency
of bacterial penetration through teeth obturated
with intact smear layer (70 percent) was significantly
greater than that of teeth from which the smear
layer had been removed (30 percent). Removal of
the smear layer enhanced sealability as evidenced by
increased resistance to bacterial penetration.1 The incidence of apical leakage was reduced in the absence
of the smear, and the adaptation of gutta-percha
was improved no matter what obturation method
was used later.2-4
What is used to obturate the canals is important; however, the manner in which the canal was

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I technique_disinfection
further action of the irrigant improving the efficacy
of the process.

Fig. 2_Result of NaOCL being
extruded periapically into the facial
spaces from forceful irrigation with
positive pressure during endodontic
treatment.

_Positive vs. negative pressure

Fig. 2

prepared prior to obturation also determines how
well the canal is sealed. Rotary instrumentation with
NiTi files has shown less microleakage than handinstrumented canals irrespective of what was used
to obturate the canal.5 The machining of the canal
walls with NiTi rotary instruments provides smoother
canal walls and shapes that are easier to obturate
when compared to stainless steel hand filing. The
better the adaptation of the obturation material to
the instrumented dentinal walls, the less leakage is to
be expected along the entire root length. The better
the canal walls are prepared and cleaned, the more
smear layer and organic debris is removed which is
beneficial to root canal sealing.
Smear layer removal is best achieved by irrigating
the canals with NaOCL (sodium hypochlorite) followed
by 17 percent EDTA solution.6 NaOCL dissolves the
organic component of the smear layer exposing the
dentinal tubules lining the canal walls, whereas EDTA,
a chelating agent, dissolves the inorganic portion of
the dentin opening the dentinal tubules. Alternating
between the two irrigants as the instrumentation is
being performed will permit removal of more organic
debris further into the tubules, increasing resistance
to bacterial penetration once the canal is obturated.7,8
Studies suggest that regular exchange and the use
of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, compensating for the effects of concentration.9 Volume
is more critical to canal disinfection during treatment
than the concentration of the irrigant.10 Flushing of
the irrigant also serves to remove the debris exposing
the dentin around the anatomy in the canal system to

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Irrigation as it relates to endodontic treatment
involves placement of an irrigating solution into
the canal system and its evacuation from the tooth.
Traditionally, this involved placement of the irrigant
with an end-port or side-port needle into the apical
canal and expressing solution out of the needle to be
suctioned coronally. This creates a positive pressure
system with force created at the end of the needle,
which may lead to solution being forced into the
periapical tissues. Positive pressure irrigation has
its risks as some irrigating solutions, such as sodium
hypochlorite, have the potential to cause tissue
injury that may be extensive when encountering the
periapical tissue and its communication with tissue
spaces (Fig. 2). These NaOCL accidents can lead to
permanent physical injury or disability with facial
deformation and neurological complications.11,12
Chow was able to show as early as 1983, that positive pressure irrigation has little or no effect apical to
the needles orifice.13 This is highlighted in his paradigm on endodontic irrigation, “For the solution to be
mechanically effective in removing all the particles,
it has to: (a) reach the apex, (b) create a current force
and (c) carry the particles away.” We increase the risk
of clinical failure due to the inability to eliminate intraradicular microorganisms from the canal system,
especially in the apical portion of the root.14
A negative pressure irrigation system on the other
hand does not create positive pressure force at the
needle’s tip, so potential accidents are essentially
eliminated. In a negative pressure irrigation system,
the irrigation solution is expressed coronally, and
suction at the tip of the irrigation needle at the apex
creates a current flow down the canal towards the
apex and is drawn up the needle. But true apical negative pressure only occurs when the needle (cannula) is
utilized to aspirate irrigants from the apical termination of the root canal. The apical suction pulls irrigating solution down the canal walls toward the apex,
creating a rapid turbulent current force towards
the terminus of the needle (Fig. 3). Haas and Edson
found, “The teeth irrigated with negative apical pressure had no apical leakage. While the teeth irrigated
with positive pressure leaked an average of 2.41 mL
out of 3 mL.”15 A study by Fukumoto found using
negative pressure there was less extrusion of irrigant
than when using needle irrigation (positive pressure)
when both were placed 2 mm from working length.16
But what other sequela can occur with minute
amounts of NaOCL leaking from the apex during the
irrigation process? Gondim et al, in a study of postoperative pain when comparing positive a negative

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technique_disinfection

pressure irrigation systems reported, “The outcome of
this investigation indicates that the use of a negative
pressure irrigation device can result in a significant reduction in postoperative pain levels in comparison to
conventional needle irrigation.”17 So although we may
not see NaOCL accidents frequently, it is possible to
see the effects of positive pressure irrigation allowing
some minute extrusion apically in our normal, dayto-day endodontic treatment. They further stated
that “the use of the EndoVac system did not result in
apical extrusion of irrigant, hence chemical irritation
of the periapical tissues leading to postoperative pain
may not be likely.” And they concluded, “It is safe to
use a negative pressure irrigation protocol for antimicrobial debridement up to the full working length.”

_EndoVac endodontic irrigation system
Designed by Dr. G. John Schoeffel with more than
a decade of research, the EndoVac irrigation system
(SybronEndo, Orange, Calif.) was developed as a
means to irrigate and remove debris to the apical
constricture without forcing solution out the apex
into the periapical tissue. The system utilizes negative
pressure through the office’s high volume evacuation system permitting thorough irrigation with high
volumes of irrigation solution.
The EndoVac system consists of Multi-Port Adapter
(MPA) assembly that connects to the high volume
evacuation hose in the dental operatory (Figs. 4, 5) To
this, connects the Master Delivery Tip (irrigation and
suction together) with a disposable syringe filled with

Fig. 3_Comparison of positive (left)
and negative (right) pressure with
regard to endodontic irrigation.
Fig. 4_EndoVac Multi-Port Adapter
MPA (left) on HVE connector and line.

Fig. 3

irrigation solution (Figs. 6, 7). Either a MacroCannula
(Fig. 8) or MicroCannula (Fig. 9) is attached and used
simultaneously with the Master Delivery Tip during
treatment. The plastic MacroCannula is placed on a
handpiece that is attached to tubing that connects to
the MPA via a separate line. This is used for coarse debris
removal. The MicroCannula is a metal suction tip available in either 21, 25 or 31 mm lengths with 12 micro
holes in the terminal 0.7mm of the tip, permitting removal of particles that are 100 microns or smaller to the
apical constricture. This tip fits into a metal fingerpiece
and is connected to the Multi-Port Adapter (Fig. 5) in the
HVE via tubing. The turbulent current forces developed
by the MicroCannula rapidly flows to the micro holes
at the terminus, which can reach within 0.2 mm of full
working length. Quite simply, the vacuum formed at
the tip of the MicroCannula is able to achieve each of
Chow’s objectives in his irrigation paradigm.

Fig. 5_EndoVac Multi-Port Adapter
(blue) connected to HVE suction
line and to the Master Delivery Tip
syringe. A separate line connects to
the MacroCannula or MicroCannula
suction tip.
Fig. 6_EndoVac Master Delivery Tip
syringe with suction line connected
to Multi-Port Adapter.
Fig. 7_EndoVac Master Delivery Tip
(irrigation-suction) on a disposable
syringe.
Fig. 8_EndoVac MacroCannula on
the handpiece.
Fig. 9_EndoVac MicroCannula in the
fingerpiece and close up showing
the rounded end with multiple lateral
micro holes.

Fig. 5

Fig. 4

Fig. 7

Fig. 6

Fig. 8

Fig. 9

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I 19

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I technique_disinfection
Fig. 10_Obturation of apical anatomy
following irrigation with the EndoVac
system demonstrating apical deltas.
(Courtesy of Dr. Richard Rubinstein,
Farmington Hills, Mich.)
Fig. 11_Obturation of apical anatomy
following irrigation with the EndoVac
system demonstrating lateral
anatomy. (Courtesy of Dr. Richard
Rubinstein, Farmington Hills, Mich.)
Fig. 12_Negative pressure irrigation
using the EndoVac system allowing
thorough debridement of the canal
system as well as the apical lesion
demonstrating significant healing
apically as well as sealer in lateral
canal at mid root. Initial (A), following
completion of endodontic treatment
(B) and six months post treatment (C).

Fig. 10

Fig. 11

Fig. 12

Nielsen and Baumgartner found the volume of
irrigant delivered with the EndoVac system was
significantly more than the volume delivered with
needle irrigation over the same amount of time.18
Furthermore, they reported significantly better debridement 1mm from working length for the EndoVac
system compared with needle irrigation.
Since one of the laws of the physics states, “only
one object can occupy a space at a time,” if the tissue
remnants can be removed from the lateral canals,
apical deltas and fins within the canal system, these
areas can be filled with obturation material providing a
better seal and inhibiting bacteria in or out of the canal
system. The EndoVac irrigation system, as Nielsen and
Baumgartner demonstrated, is able to better clean at
the apex where other irrigation methods and systems
have not been able to do as thorough a job (Figs. 10–12).

_EndoVac technique
Following removal of the chamber roof and exposure of the pulp, the Master Delivery Tip is used

20 I roots
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to provide frequent and abundant irrigation as the
orifices are identified and explored. The Master
Delivery Tip may be used to deliver irrigant into the
pulp chamber while also suctioning debris brought
coronally during the instrumentation process. Be
careful to deliver the irrigant passively into the pulp
chamber; avoid delivering irrigant directly into the
orifice as this will create positive apical pressure
(Fig. 13). The benefit of the Master Delivery Tip is
that with a single tip at the tooth’s access, visibility is not blocked and large volumes of irrigation
solution can be utilized. As the canals are being
instrumented to a size 30 with a 0.04 taper, the
MacroCannula is introduced between changes in
file size as the canal is shaped. The MacroCannula is
utilized to remove coarse debris during instrumentation and is used in combination with the Master
Delivery Tip, which delivers the irrigating solution.
Negative pressure is created as irrigating solution
is drawn down the canal towards the apex as it is
expressed from the Master Delivery Tip and then
is drawn up the MacroCannula (Fig. 14). It is sug-

[21] =>

[22] =>

I technique_disinfection

Fig. 13

Fig. 14

Fig. 13_Master Delivery Tip being
used to provide constant irrigation
as the canal is instrumented.
Fig. 14_Use of the EndoVac
MacroCannula and Master
Delivery Tip.
Fig. 15_Use of the MicroCannula
of the EndoVac system showing
placement of the tip in the
apical root end.

Fig. 15

gested that the MacroCannula be used with a slight
pumping motion as each canal is flushed. Irrigation
should continue with the MacroCannula until clear
fluid is observed being withdrawn through the tubing connected to the handpiece before proceeding
to the next file.
When the canal has been enlarged to the desired size, the MacroCannula is again used until
clear solution is observed in the tubing. This will
ensure that all coarse debris has been removed
from the canal. Next, the metal MicroCannula
is placed on the Fingerpiece and attached to the
MPA connector line (white connection) and used
at the completion of canal instrumentation to remove fine debris to the apical constricture under
negative pressure when the canal has been instrumented to a size 35 with a 0.04 taper or greater
(Fig. 15). To prevent plugging of the fine holes in
the apical terminus do not use the MicroCannula
until thorough irrigation has been accomplished
with the MacroCannula and all instrumentation
has been completed.

_Conclusion
Instrumentation, disinfection and obturation are
important aspects of rendering quality endodontic
care. Yet, the instruments we use to prepare the canal,

22 I roots
1_ 2012

whether hand or mechanized are unable to reach
all aspects of the canal system. Irrigation is key to
cleaning and disinfecting those areas that cannot be
reached by instrumentation alone.
The EndoVac irrigation system with its negative
pressure is able to more much larger volumes of irrigant through the canal system, safely, resulting in
more thorough removal of the micro debris at the
apical constricture, thereby providing a better environment for sealing. Accordingly, negative pressure
irrigation not only greatly improves both the flow
and safety of irrigation with NaOCL but has also
been shown to minimize postoperative sensitivity
following treatment compared to traditional positive pressure irrigation protocols._
A complete list of references is available from the
publisher, feedback@dental-tribune.com.

_about the author

roots

Gregori M. Kurtzman is in
private general practice in Silver Spring,
Md., and a former
assistant clinical professor at University
of Maryland. He has
lectured internationally on the topics of
restorative dentistry,
endodontics and implant surgery and prosthetics, removable and
fixed prosthetics and periodontics, and he has
over 240 published articles. He has earned
fellowship in the AGD, AAIP, ACD, ICOI, Pierre
Fauchard, ADI, mastership in the AGD and ICOI
and diplomat status in the ICOI and American
Dental Implant Association (ADIA). He has been
honored to be included in the “Top Leaders
in Continuing Education” by Dentistry Today
annually since 2006. He can be contacted at
drimplants@aol.com.

[23] =>

[24] =>

I technique_canal preparation

Negotiating and shaping
around anatomic root
canal impediments
Tactile clues, bypass techniques,
shaping procedural flow
Author_L. Stephen Buchanan, DDS, FICD, FACD

Impediment [im-ped-uh-muh’nt]
1. Obstruction; hindrance; obstacle.
Perform endodontic therapy on 10 molars and
chances are you ran into at least one anatomic Impediment. Despite the significant occurrence rate,
few of us have been taught how to identify and manage apical impediments, let alone those that occur in
the coronal third.
Without a clever technique for these cases, the
right instruments and an accurate mental image
of the canal space you are in, you have virtually no
chance of reaching the end of the root canal space,
significantly increasing the chances of persistent
apical infection. With the right stuff, managing
these endodontic challenges can be a fascinating
procedural experience requiring little extra time and
delivering remarkably predictable outcomes.
Let’s begin with a look at the different types of
impediments (Figs. 1–6):

_Anatomic impediments
1. Apical irregularity at the terminus of a relatively
straight canal.
2. Irregularity on the outside wall of a curved canal.
3. Abruptly curved canal.

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1_ 2012

_Iatrogenic impediments
4. Apical blockage
5. Apical ledging
6. Remnant of instrument
How do you know you have met an impediment?
That’s easy — by the tactile sensation felt as loose
resistance to file advancement. Tight resistance to file
advancement is the sensation felt when a file moving
apically binds and then exhibits tug-back upon removal.
Tight resistance means the file is binding on two opposite
sides. Usually in this case, working the file (push-pull, balanced force, rotary, etc.) will allow it to progress apically.
Loose resistance to file advancement means
that the file tip is caught either in some type of an
irregularity (lateral canal, isthmus, fin) or the file tip
is bumping into the outside wall of an acutely curved
canal. All that remains in the diagnosis of apical impediment is to apply an apex locator (Fig. 7) lead to
the file and confirm a short reading (and obviously an
apex locator is the best method of determining when
you have actually reached the Holy Grail — length).
OK, so how do we deal with the aforementioned
impedimento?*
First off, we do not ever attack or even firmly
engage an impediment with the tip of any instru-

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technique_canal preparation

Fig. 1

Fig. 2

Fig. 4

ment. That’s how ledges happen, and a ledged
canal is waaaay more difficult to manage successfully than just a severely curved canal. Aspire to
the maxim, “If you can’t fix it, don’t fix it so nobody
else can fix it.”
Managing impediments is all about file bending,
mental visualization and patient, skilled technique.
So let’s discuss file bending.

_When and how to bend negotiating files
You might be surprised to read that I find it unnecessary to slightly curve all negotiating files before
use — a method most of us were taught. Due to their
exceptional flexibility, unbent K-files sizes smaller
than #15 will easily traverse impediment-free canals
with greater than 90-degree curvatures (Fig. 8).
Try using only straight negotiating files for a
time — assuming you negotiate through a lubricant
and start with an 08 K-file in small canals. You will
be amazed at how often you get to length without
bending them. At the end of the day, using cotton pliers with that ribbon-curling motion on your smallish
files is a waste of time, so my advice is to stop yourself.

Fig. 3

Fig. 5

You don’t have to do that anymore. Not doing that
could save weeks of your life over a career.

_Mental imaging
To understand this important concept better, try
this thought experiment:
Be the file.
Imagine that you are the negotiating file moving into a canal. You have a subtle curve along your
whole length and because you are being used in a
watch-winding motion you’re tip is waving back
and forth “scouting” loosely through the canal,
and, just as estimated length nears, “dink, dink” —
loose resistance to apical advancement (Figs. 9,10)
— shoot! We pull back, re-approach, and get the
same result regardless of how we manipulate the
instrument.
To better understand why this has occurred,
ribbon-curl a #10 K-file with cotton pliers along its
full length and then clamp the file with a hemostat
about 4 mm back from the tip. Look at the tip portion
with magnification and you will see an essentially
straight instrument tip. And this is the part of the file

Fig. 6

Fig. 1_Apical irregularity
at the terminus of a relatively straight
canal. (Photos/Provided by
Dr. L. Stephen Buchanan)
Fig. 2_Irregularity on the outside wall
of a curved canal.
Fig. 3_Abruptly curved canal.
Fig. 4_Apical blockage.
Fig. 5_Apical ledging.
Fig. 6_Remnant of instrument.

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I technique_canal preparation
that is supposed to make its way around a canal path
that is radically more bent.
Another way to say it is that the file tip was not
bent acutely enough to keep the file tip centered as
it moved into the tightly breaking canal curvature.
When a file is curved 25 degrees along its whole
length, it will never make it around a canal curvature
that is 90 degrees along its last 1-2 mm.
Fig. 7_Mini-Apex Locator with cord
caddy (J. Morita).
Fig. 8_Unbent #15 negotiating file
to length around 120-degree
curvature in the ML canal.
Fig. 9_File against an apical
impediment in the distal canal of
this lower molar.
Fig. 10_Illustration showing file tip
engaging lateral canal acting
as an impediment.

_Clever technique
Mentally imaging the canals you are treating,
coupled with the use of appropriately curved files,
just needs a bit of clever technique to conquer the
apical impediment. The first clever technique trick
is to pre-bend the last 1-2 mm of the file with an
EndoBender (SybronEndo) (Fig. 11), look down the
length of the file and carefully adjust the indicator
on the stop (notch, line or point) to be in line with the
bend of the file.
Now, as you scritch-scratch into the canal, hunting for the path of least resistance, you feel and see

Fig. 7

Fig. 8

Fig. 9

Fig. 10

26 I roots
1_ 2012

the file passively drop deeper into the canal as you
advanced in a new direction. Now, after you have successfully snaked the file around this one-of-a-kind,
difficult anatomy, the next question is, “How will I get
back here with my next instrument?”
All you have to do is to look at the indicator on the
stop, note the direction and after bending the next file
and aligning the stop to the bend you simply move
the file to length with its bent tip pointing in the same
direction as the previous file to length.

_Final impedimento negotiating advice
• Remember that there is little forgiveness
in a tightly curved canal, so for goodness sake
do anything to avoid blocking the end of the
canal. Most often, compacted blockage at a
canal curvature will never allow re-entry along
the original canal path so despite a lot of effort
spent attempting to regain patency, the most
likely outcome will be apical perforation with
these small instruments.

[27] =>

[28] =>

I technique_canal preparation
• Use an apex locator or you are working waaay
too hard without a clue as to where you are. Is that acceptable to you when you could spend less time and
definitively nail length with an apex locator.
• Never initially thread the apical half of a
small canal with larger than a #08 K-file. Never
negotiate any canals without a lubricant in the
access cavity.
• Once you battle your way to length with that
tiny first instrument, don’t just get patent a mm
out the end of the canal — in this case I suggest
you go 3-4 mm long and do 30-40 push-pull filing
strokes to loosen the file and slightly enlarge the
canal. This act will greatly improve your chances of
avoiding blockage with the next largest file. There
are few experiences more frustrating than to have
cleverly and heroically battled your way to length
through a hideously tortuous root canal, never to
return again.
• Distal canals of lower molars and DB canals in upper molars commonly have severely,
abruptly curving canals enclosed inside remarkably straight external root structure. Look for
loose resistance to apical advancement, when you
feel it whip that instrument out, bend the very tip
just short of 90 degrees, adjust the stop indicator,
and go hunting!
So now, if you have managed to sneak to length
and establish a file path around the impediment,
it is left to shape to and beyond the impediment in
preparation for cleaning and obturation.

_Shaping around impediments
Fig. 11_EndoBender (SybronEndo)
and correct bend at the very tip
of the file.

Let’s begin with a discussion about shaping
objectives. The objective of every known endodontic preparation method is to enlarge the canal

(by some amount) short of the end of the primary
root canal terminus. First, to debride the canal of
inflamed, infectious goop, and second, to create
resistance form near the very end of the canal to
allow obturating materials to be more densely
packed and tightly sealed.
The narrowest part of a prepared canal should be
at its end.
Unless we are able to successfully shape around
an impediment, there will be a discontinuity of taper
at that point — so the narrow part next to the impediment has gotta go.
Let’s start by doing the #10 file test. Measure a
brand-new #10 SS K-file to the negotiated length
and insert it, unbent, into the canal. See if it will go
to and through the end of the canal. If it does, the
impediment has been reduced just by the canalsmoothing action of the small negotiating files. In
this case, carry on as if the impediment never happened and finish the shape. If the #10 file meets loose
resistance to apical file placement, simply shorten the
stop to the reference point, measure the file, and you
now know the length to impediment.
Measure the first rotary shaping file 1 mm short of
the length to impediment — this will ensure that the
impediment is not engaged and dinged inadvertently
— and cut to that length.

_Coronal shape
In small canals, I begin shaping with a 20-.06 GTX
file and in larger canals I begin with a 30-.08 GTX. As
impediments are located some distance short of terminal length, in a wider part of the canal, these initial
instruments usually cut to the prescribed length 1
mm short of the impediment. If the canal will accept
it, I then cut the next tip size up — in small canals to a
30-.06 and in larger canals a 40-.08 — 1-2 mm shy of
impedimento-town.

_Apical shape
With this larger coronal shape developed
(but limited to 1mm by GTX files), it will be much
easier to skate pre-bent SS K-files beyond the
impediment and to their intended final position.
The strategy for this next piece is basically to cut
an apical taper using a serial step-back method
with SS K-file sizes #10, 15, 20, 25, 30, 35, 40 in
multiple recapitulations:
10, 15, 20, 25, 30, then;
15, 20, 25, 30, 35, then;
20, 25, 30, 35, 40 in small canals, or;
25, 30, 35, 40 in larger canals.
The trick here is to keep it loose, avoid engaging the
impediment and move every file in the series to their

Fig. 11

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1_ 2012

[29] =>

[30] =>

I technique_canal preparation

Fig. 12

Fig. 13

binding points beyond the impediment, do a short
amplitude watch-winding motion to cut a bit, and then
place the next file in the series. Any time you wonder to
yourself whether you should irrigate, you should irrigate.
Fig. 13_Post-operative X-ray If this question never occurs to you, you need to review
showing three portals of exit in the your clinical RCT objectives and think about it more often.

Fig. 12_Prebent file to length beyond
the impediment and around 160
degrees of curvature.

distal root.

_Shaping past the impediment
So we have shape coronal to the impediment and a
nice apical preparation just beyond the impediment, so
in this case the discontinuity of taper we must resolve is
at the impediment, rather than at the end of the canal.
To finish the preparation, there is no faster nor surer
way to get this done than to bend the tip of a rotary
file, sneak it by hand around the impediment, click the
SS handpiece onto the latch-grip handle, and spin it to
length or beyond. I know, it gave me the willies the first
time I did it, but it works like a champ. Obviously use a
new file and remember that bending a shape memory
rotary file requires a bending plier as used above, and
after grasping the instrument tip, over-bend it to about
180 degrees. When released, the file tip will retain a 35to 45-degree bend — enough to bypass the impediment
after coronal and apical shaping.
Irrigation with 6 percent NaOCl and 17 percent
EDTA must follow. If you can apply irrigants for a long
enough time frame (vital-40 minutes, necrotic-20
minutes) at that appointment, fill it at that appointment. If not, place CaOH in the shaped canals for two
weeks, irrigate half the above time, and fill.

_Conclusions
Blocking, ledging or just never getting to the
terminus because of a mishandled impediment is

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1_ 2012

not the end of the world, but it’s not the end of
the canal either.
Gone are those halcyon days when we could
get away with telling curious patients that
blocked canals were calcified apically. Never
mind, apply these principles (Figs. 12,13) and I’ll
see you at the apex!_
* Italian for impediment

_about the author

roots

L. Stephen Buchanan, DDS,
FICD, FACD, was valedictorian of his class at the
University of the Pacific
School of Dentistry, and he
completed the endodontic
graduate program at Temple
University in Philadelphia in
1980. He began pursuing
3-D anatomy research early
in his career, and in 1986
he became the first person in dentistry to use micro
CT technology to show the intricacies of root structure.
In 1989 he established Dental Education Laboratories, through which he has lectured and conducted
participation courses around the world. Buchanan
holds a number of patents for dental instruments
and techniques, including variably tapered shaping
instruments for use in endodontics. He pioneered a
system-based approach to treating root canals. He is
a diplomate of the American Board of Endodontics.
He maintains a private practice limited to endodontics
and implant surgery in Santa Barbara, Calif. Contact
him at 1515 State St., Suite 16, Santa Barbara, Calif.
93101, (800) 528-1590 or (805) 899-4529, info@
endobuchanan.com, www.endobuchanan.com.

[31] =>

[32] =>

I trends_instrumentation

The rules of engagement
Author_Barry Lee Musikant, DMD

Fig. 1_Images of the approximately
7 mm apical to the cusp tip both in
a radiograph and highlighting that
same 7 mm length on the burs.
(Photos/Provided by
Dr. Barry Lee Musikant)
Fig. 2_Images illustrating the
marking of a #4 round bur 7 mm
from the tip.

Fig. 1

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1_ 2012

_We have heard the term “rules of engagement”
used in the military to categorize a line of behavior
that best fits the various situations that may arise.
These rules are a product of experience, war college
exercises and think tanks. They are critical because war
is not a game and what starts off as an orderly process
can rapidly degenerate in the fog of war.
While not as all-consuming as war, we need rules
of engagement in endodontics. The American Association of Endodontists has established guidelines
for determining degrees of case difficulty, implying
beyond a certain degree of complexity, the cases
should be referred to a specialist. While case assessment is a worthy goal, it is unrealistic to determine
when a case should actually be sent to a specialist
because of the wide range of endodontic skills that
individual dentists bring to the tasks.
Rather than impose generalized rules, I think it
is more productive to apply rules of engagement on
the basis of sound mechanical principles, principles
that apply to both the design and implementation of
the instruments designated for endodontic procedures. Once dentists understand basic mechanical
principles, it will become readily apparent what anatomical situations will impose greater burdens on the
instruments and the dentists employing them. I don’t
completely agree with an opinion that I have read in
various venues stating that it is not the instrument,

Fig. 2

but the dentist employing it that matters. In fact,
there is a continuous interaction between any instrument and the dentist using it and a well-designed
instrument used in the most efficacious manner can
reduce the challenges when encountering complex
anatomy.
The best way to utilize the rules of engagement is
to apply the logic that support these rules, one rule
at a time and then observe how they interact with
other rules having a neutral, positive or negative effect on the overall procedure. Let’s start with initial
canal access. The goal is to gain access to the entire
canal system while minimizing the amount of tooth
structure that we must remove.
The more calcified the case, the greater the
amount of overlying secondary dentin obscuring our
access to the canal orifices. To discover these canals,
we are most likely going to have to go deeper and
wider since canals diverge from the chamber as they
travel apically. Calcified chambers represent a line of
division for some dentists who may then decide to
refer out. For them, they have confronted the first
rule of engagement, namely encountering a situation
where they are uncomfortable in proceeding, and
have correctly decided to withdraw. I say correctly
because deferring to those with greater skills and
experience is never a bad decision, although this is
not what this article is about.

[33] =>

trends_instrumentation

Fig. 3_Photograph of a pulp stone
whose presence is shown by a
groove between the walls and the
centrally placed stone.
Fig. 4_Photograph of pulp stones.
Notice it is easier to find any tissue
inclusions when they represent
interruptions in an otherwise
smooth floor.

Fig. 3

Typically, dentists will use either a No. 4 or 6 round
bur to gain access into the pulp chamber and then
straighten the walls with either barrel-type diamonds
or carbide burs. Whether or not the canals are calcified the pulp chamber is approximately 7 mm apical
to the cusp tip unless the cusp tip has been severely
worn down (Fig. 1).1 Having a clearly defined 7 mm
mark along the length of a surgical length high-speed
bur makes aligning the appropriate depth easier
(Fig. 2). With the roof completely removed either by
pulling up with the round bur or the use of the barrel
diamonds or stainless-steel carbide burs, we may be
staring at a floor that gives little hint that it was once
occupied by a soft gelatinous pulp tissue. What takes
its place are pulp stones that grow from the floor
coronally, are often somewhat translucent and take
on a yellowish tint. At times these stones may actually cleave off the floor and walls of the canal while at
other times they hold on quite tenaciously and must
be removed with drills or ultrasonics.
Because these stones grow coronally from the
floor, their presence is often denoted by a groove
between the walls and the centrally placed stone
(Fig. 3). The best place to concentrate on removing
the stones while searching for canal orifices is along
these grooves. I prefer the use of drills to explore the
depth of these grooves rather than ultrasonics. Drills
leave a smooth floor, while ultrasonics leave the
floors scoured. It is easier to find any tissue inclusions
when they represent interruptions in an otherwise
smooth floor (Fig. 4). For the past several years I have
been using Munce burs (CJM Engineering) that are a
series of round burs from 0.25 to 4 on 34 mm shafts
(Fig 5). Recently, I have been experimenting with
EndoGuide burs (SS White) (Figs. 6a, 6b) that for the
most part are triangular in shape with rounded tips
sizes that are smaller than Munce burs. Both readily
cut the dentin in a very controlled fashion. I believe
the EndoGuide burs are able to trough the grooves

Fig. 4

somewhat easier because of their triangular design.
Working under a microscope using either one of
these micro-bur systems gives the dentist the ability
to find not only the main canals, but also mb2s, middle mesials and any other aberrant canals that may
be present. The depth of the groove represents the
limit on how deep you explore. Once a smooth floor
is encountered, we now will only go deeper where
tissue inclusion bodies appear.
We could say that the rules for further engagement when encountering highly calcified canals
would include the need of a microscope or at least
fairly powerful loupes with illumination as well as
some form of Munce bur or EndoGuide bur. Without
these extra tools, referring out becomes a time honored and wise decision.
Once the canals are recognized, we want to
confirm their presence by being able to negotiate
an instrument through them to the apex. It is quite
logical that some of the calcifications encountered
in the chamber will also have affected the patency
of the canal. When first negotiating through a canal
orifice, it is helpful to make sure the chamber is well
lubricated with either NaOCl or aqueous EDTA. If vital
tissue is present I prefer the use of aqueous EDTA first,
because unlike NaOCl it will not congeal the tissue
prior to digesting it, making it easier to negotiate
through the length of the canal. When resistance is
encountered with the first instrument attempting to
negotiate into the canal orifice, there are those who
suggest the use of stiffer files that can press heavily
into what is believed to be the canal opening. I would
suggest an opposite approach only using the most
flexible reamers that have minimal engagement
along length to first attempt to enter into a tight
canal. I am against stiff instruments because if you
are wrong in your estimate of where patency resides,
a stiff instrument is far more likely to produce an
indentation into the dentin making it more difficult

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I trends_instrumentation
to find the canal. It’s far better to use an instrument
with minimal engagement that will find the smallest
patent entry into the canal. If such an instrument
does not find a patent pathway, it is likely one is still
not present at the depth so far attained, and deeper
probing with either the Munce burs or the EndoGuide
burs is required.
Eventually, the dentist will reach a point where
patency exists and he will find it earlier with an 06
reamer than he will with a K-file of the same tip size.
By staying within the grooves that were troughed
particularly at the apices of what may be a triangular,
square or rhomboid floor of the chamber, the dentist
is unlikely to perforate through the floor. There are
ample landmarks available, and as long as we remain
closely attached to them we are unlikely to perforate
either though the floor or laterally.
An additional rule of engagement is to use reamers as well as relieved reamers, as I will soon show.
Reamers both unrelieved and relieved are compatible
in design and utilization with attaining the results
you want. First you want to negotiate through the
length of the canal as efficiently as possible.2 K-files,
like every true file, have a high number of horizontally
oriented flutes on a shaft that is watch-wound into
the canal. In the process of applying a horizontal motion (that is what watch winding is) to horizontally
oriented flutes, the flutes will engage and disengage
without shaving dentin away from the length of the
canal walls until the pull stroke is employed. Because
watch winding is the predominant motion, it is all
wasted energy that does not make for efficient shaping. The pull stroke will shave dentin away from the

canal walls, but an instrument designed to shave
dentin from the canal walls only on the pull stroke will
distort curved canals to the outer wall as the tip size
of the instruments increase. On the in-stroke, these
same instruments will tend to impact debris apically
with a resultant loss of length and further distortions
when an attempt is made to regain that length.
Using reamers (SafeSiders, Essential Dental Systems), both unrelieved and relieved, eliminates the
problems of K-files, even though they are used in the
same exact manner. Reamers, unlike K-files, have
flutes that are vertically oriented, immediately shaving dentin away rather than unproductively engaging it (Figs. 7, 8). The best analogy I can think of is a
comparison to shaving one’s face with a razor. Please
note that effectiveness of the blades on a razor is a
result of their orientation being at right angles to the
plane of motion. That is why it is on a T. Relieved reamers are more flexible, less engaging and more efficient
at shaving dentin away from the canal walls, giving
the dentist a superior tactile perception of what the
tip of the instrument is encountering.
Superior tactile perception gives the dentist the
ability to differentiate between the tip of the instrument hitting a wall or being in a tight canal. The
former situation produces no tugback, while the latter produces immediate tugback. If no tugback exists,
the dentist removes the instrument, pre-bends it at
the tip and manually attempts to negotiate around
the impediment. If tugback exists, the dentist uses
a twist and pull motion to negotiate to the apex.
It is far more difficult to achieve these efficiencies
with K-files. Their design is not consistent with the

Fig. 5_Photograph of a
Munce Bur.
Figs. 6a, 6b_Photograph of
SS White EG5 and EG7 burs.

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Fig. 5

Fig. 6a

Fig. 6b

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trends_instrumentation

Fig. 7

function demanded of them while the reamers both
unrelieved and relieved are. All it takes is to try them
to confirm these differences.
Let’s expand our rules of engagement. Now let us
include the use of reamers as our initial instruments
particularly when the canals are most calcified and
tortuous in their pathway. Of course, if they are so much
more effective in the most difficult situations, why
would they not be used in all situations? They should be.
Today’s paradigm is to create a glide path using Kfiles to a 20 and then switch to some rotary NiTi system.3 We have just discussed a much more productive
alternative to K-files. Rotary instruments may now be
used, but I believe we are all aware that the introduction of rotary NiTi does not come without a burden,
acceptable to many and not to others. As you may
have already surmised, I am referring to the potential
for instrument separation, a result of the torsional
stress and cyclic fatigue that is intimately associated
with rotary NiTi.4 The NiTi instruments are shaped just
like reamers with the exclusion of the flat.5
They are correctly designed in that regard, but
rotation is not the way they should be used. Far better
to use reamer designed instruments in a reciprocating handpiece, producing a small arc of motion that
severely limits the amount of torsional stress and
cyclic fatigue generated. In fact, that is precisely the
way we use the relieved reamers, in a reciprocating
handpiece (when not used manually with a tight
watch-winding stroke) confined to a 30-degree arc
of motion. Because the arc of motion is confined, we
are not limited in its oscillating speed. Unlike rotary
NiTi that is generally used at 150-300 rpm, the reciprocating handpiece operates between 3,000 and
4,000 cycles per minute (Fig. 8).
What the dentist experiences at this frequency is an
instrument that literally negotiates through the length
of the canal often like a hot knife through butter. While
this is certainly a welcome condition, perhaps it is more
important for the dentist to know immediately when
the canal hits an obstruction. This capability tells the
dentist exactly when he should stop using the reamer
(either manually or engine-driven) remove it from the
canal, pre-bend the tip of the instrument, negotiate

manually around the obstacle and, once around, reattach the head to the reciprocating handpiece at the
newly negotiated length followed by rapid negotiation
to the apex. The reamers, both relieved and unrelieved,
are the same instruments used both manually and
engine-driven, providing a flexibility that neither Kfiles nor rotary NiTi can duplicate.
The rules of engagement are now expanded to the
use of a reciprocating handpiece over a rotary engine.
It is safer and more adaptable to complex anatomy.
In fact, there must be much truth to the benefits of
reciprocation over rotary NiTi when you see major
rotary NiTi companies introducing reciprocating systems. Belatedly, they are recognizing the vulnerabilities of rotary NiTi6 and substituting a safer approach
even though they are likely to cannibalize their own
sales of rotary NiTi. While they are making progress
in the reduction of instrument separation, they are
reducing the cost of these instruments by coming up
with techniques that shape canals far less adequately
than recommended in the literature. A good deal of
research has gone into establishing minimum apical
preparations of 35.
The manufacturers of these new oscillating systems are essentially telling dentists that an apical
preparation of 25 is sufficient and, where major
resistance is encountered, an even smaller apical
preparation is acceptable. This is technique divorced
from research and the increasingly detailed concept
of what we know pulpal anatomy to be. How does
a preparation to 25 conical throughout its length
comport with anatomy that we know is often highly
oval7 at times in the configuration of sheaths of tissue
that are quite thin mesio-distally, but often four to
eight times wider bucco-lingually?
Taking this one step further, in those cases where
a 25/08 instrument goes to length fairly easily, is it
not likely that the ease of negotiation results from
a good deal of lateral space within the length of the
canal that is not engaging the instrument? If this is
the case, is it also not likely that those walls that were
not engaged are also not well cleansed? Reciprocating NiTi instruments as they are presently being sold
is a solution to a marketing problem that does not

Fig. 8

Fig. 7_Photograph of both a relieved
reamer and a K-file. Note the relieved
reamer has a flat side and less flutes
which are vertically oriented. Note
the K-reamer has more flutes that are
horizontally oriented.
Fig. 8_Photograph of a relieved
reamer in a reciprocating handpiece.

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I trends_instrumentation

Fig. 9

Fig. 10

Figs. 9–11_Radiographs of cases
completed using relieved reamers
in a reciprocating handpiece.

address the requirements for sound biological principles. The rules of engagement tell us that we cannot
compromise on canal preparations. They have an
immediate impact on irrigation and the obturation
that is shortly to follow.
We can round out this discussion by mentioning some recent research that makes all the sense
in the world even though we may not have heard
about it until recently. Recent research now tells
us that the use of rotary NiTi instruments in curved
canals results in micro-fractures in the apical
third.8 Micro-fractures in the canals are the mirror
image of the micro-fractures in the NiTi instruments that have been reported over the years.
The only difference is that while the evolution of
NiTi can make it less vulnerable to such microfractures, the tooth structure remains the same.9
Yet another reason for using NiTi in whatever form
it is in the most conservative ways, safer for the
instruments, but compromised biologic results
for the patient.
One last point: Rotary NiTi is noted for the
retention of the smear layer10 particularly in the
apical third. This is counterproductive for a wellsealed canal. Reciprocation, on the other hand,
has been shown to completely remove the smear
layer throughout the length of the canal.
Pictured are some recent routine results we
attain using the relieved reamers in conjunction
with the 30-degree reciprocating handpiece
(Figs. 9–11)._

_References
1.

36 I roots
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A.S. Deutsch & B.L. Musikant. Morphological
Measurements of Anatomic Landmarks in Human Maxillary
and Mandibular Molar Pulp Chambers. J of Endodon June
2004;30(6).
Wan J, Rasimick BJ, Musikant BL, Deutsch AS. Cutting
efficiency of 3 different instrument designs used in
reciprocation. Oral Surg Oral Med Oral Pathol Oral Radiol
Endod. 2010 May;109(5):e82–85.
Patiño PV, Biedma BM, Liébana CR, Cantatore G,
Bahillo JG. The influence of a manual glide path on the
separation rate of NiTi rotary instruments. J Endod.
2005 Feb;31(2):114–116.

Fig. 11

Rasimick BJ, Shah RP, Musikant BL, Deutsch AS. Cyclic
Fatigue Resistance of Rotary and Reciprocating Endodontic
Files. J Dent Res 2009;88(Spec Iss A):1087.
5. Musikant BL, Cohen BI, Deutsch AS. Comparison
instrumentation reamers and files versus a flat-sided
design of conventional noninterrupted, flat-sided design. J
Endod. 2004;30(2):107–109.
6. Sattapan B, Nervo GJ, Palamara JE, Messer HH. Defects in
rotary nickel-titanium files after clinical use. J Endod. 2000
Mar;26(3):161–165.
7. Wu M-K, Roris A, Barkis D, Wesselink Prevalence
and extent of long oval canals in the apical third. Oral
Surgery, Oral Medicine, Oral Pathology, Oral Radiology and
Endodontics 89, 739–742.
8. Yoldas O, Yilmaz S, Atakan G, Kuden C, Kasan Z. Dentinal
Microcrack Formation during Root Canal Preparations by
Different NiTi Rotary Instruments and the Self-Adjusting
File. J Endod. 2012 Feb;38(2):232–235.
9. Paranjpe A, de Gregorio C, Gonzalez AM, Gomez A, Silva
Herzog D, Piña AA, Cohenca N. Efficacy of the selfadjusting file system on cleaning and shaping oval canals: a
microbiological and microscopic evaluation. J Endod. 2012
Feb;38(2):226–231
10. Scherman L, Sultan, P. Comparaison des états de surfaces
canalaires entre un système mécanisé* et divers systèmes
NiTi. Le Chirurgien Dentiste de France no 1411 du 5
novembre 2009.

_about the author

roots

Barry Lee Musikant, DMD, is
a member of the American
Dental Association, American Association of Endodontists, Academy of General
Dentistry, the Dental Society
of New York, First District
Dental Society, Academy of
Oral Medicine, Alpha Omega
Dental Fraternity and the
American Society of Dental
Aesthetics. He is also a fellow of the American College of
Dentistry (FACD). As a partner in the largest endodontic
practice in Manhattan, Musikant’s 35-plus years of practice experience have established him as one of the top
authorities in endodontics. To find more information from
Dr. Musikant, please visit www.essentialseminars.org,
email info@essentialseminars.org or call (888) 542-6376.

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I trends_lasers

Lasers in endodontics
Authors_Enrico DiVito, DDS; Prof. Rolando Crippa, MD, DDS; Prof. Giuseppe Iaria, MD, DDS;
Prof. Vasilios Kaitsas,DDS; Prof. Stefano Benedicenti, DDS & Prof. Giovanni Olivi, MD, DDS

pulp tissue. Access to the canal orifices can be accomplished effectively after the number of bacteria has
been minimized, thereby avoiding the transposition
of bacteria, toxins and debris in the apical direction
during the procedure. Chen et al. demonstrated that
bacteria are killed during cavity preparation up to a
depth of 300 to 400 µm below the radiated surface.20
Moreover, Erbium lasers are useful in the removal
of pulp stones and in the search for calcified canals.
Preparation and shaping of canals

Fig. 1

The preparation of the access cavity can be performed directly with Erbium lasers, which can ablate
enamel and dentine. In this case, the use of a short
tip is recommended (from 4 to 6 mm), with diameters
between 600 and 800 µm, made of quartz to allow the
use of higher energy and power. The importance of
this technique should not be underestimated.
Owing to its affinity to tissues richest in water
(pulp and carious tissue), the laser allows for a minimally invasive access (because it is selective) into the
pulp chamber and, at the same time, allows for the
decontamination and removal of bacterial debris and

The preparation of the canals with NiTi instruments is still the gold standard in endodontics today.
In fact, despite the recognized ablative effect of Erbium lasers (2,780 and 2,940 nm) on hard tissue, their
effectiveness in the preparation of root canals appears to be limited at the moment and does not correspond to the endodontic standards reached with NiTi
technology.21–23 However, the Erbium,Chromium:
YSGG (Er,Cr:YSGG) and the Erbium:YAG (Er:YAG)
lasers have received FDA approval for cleaning, shaping and enlarging canals. A few studies have reported
positive results for the efficacy of these systems in
shaping and enlarging radicular canals.
Shoji et al. used an Er:YAG laser system with a
conical tip with 80 percent lateral emission and 20
percent emission at the tip to enlarge and clean the
canals using 10 to 40 mJ energy at 10 Hz, obtaining
cleaner dentinal surfaces compared with traditional
rotary techniques.24
In a preliminary study on the effects of the Er:YAG
laser equipped with a microprobe with radial emission of 200 to 400 µm, Kesler et al. found the laser to

Fig. 2

Fig. 3

_This article will analyze some of the most important research in the international literature today
and the new guidelines for the use of the laser as a
source of activation of chemical irrigants.

_Laser-assisted endodontics
Preparation of the access cavity

Fig. 1_Localization to 1 mm from
the apex of the near infrared laser
fiber and different penetration of the
dentinal wall with Nd:YAG laser and
diode 810 nm (on the right).
Fig. 2_Radial firing tips for
Er,Cr:YSGG laser.
Fig. 3_Undesirable thermal effects:
during the retraction movement of
the fibre of an Nd:YAG laser in a dry
canal, contact with the dentinal wall
can cause burns.
Fig. 4_Undesirable thermal effects:
during the retracting movement
of an Er,Cr:YSGG laser tip used
according to a traditional method,
the tip contacting the dry dentinal
wall causes burns, ledging and
transportation of canals.

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Fig. 4

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trends_lasers

Figs. 5,6_SEM images of radiated
dentine with Nd:YAG laser (dry, 1.5
W, 15 Hz). Note the extensive areas
of dentinal melting and bubbles.
(Figures 5–12 courtesy of Prof.
Vasilios Kaitsas, Aristotle University
of Thessaloniki, Greece.)

Fig. 5

Fig. 6

Fig. 7

Fig. 8

have good capability for enlarging and shaping in
a faster and improved manner compared with the
traditional method. The SEM observations demonstrated a uniformly cleaned dentinal surface at the
apex of the coronal portion, with an absence of pulp
residue and well-cleaned dentinal tubules.25
Chen presented clinical studies prepared entirely
with the Er,Cr:YSGG laser, the first laser to obtain
the FDA patent for the entire endodontic procedure
(enlarging, clearing and decontaminating), using tips
of 400, 320 and 200 µm in succession and the crowndown technique at 1.5 W and 20 Hz (with air/water
spray 35/25 percent).26,27
Stabholz et al. presented positive results of treatment performed entirely using a Er:YAG laser and endodontic lateral emission microprobes.28,29 Ali et al.,
Matsuoka et al. and Jahan et al. used the Er,Cr:YSGG
laser to prepare straight and curved canals, but in
these cases, the results of the experimental group
were worse than those of the control group. Using the
Er,Cr:YSGG laser with 200 to 320 µm tips at 2 W and
20 Hz on straight and curved canals, they concluded
that the laser radiation is able to prepare straight and
curved (less than 10 degree) canals, while more severely curved canals demonstrated side effects, such
as perforations, burns and canal transportation.21–23
Inamoto et al. investigated the cutting ability and
the morphological effects of radiation of the Er:YAG
laser in vitro, using 30 mJ at 10 and 25 Hz with a velocity of extraction of the fibre at 1 and 2 mm/seconds,
again with positive results.30 Minas et al. reported
positive results using the Er,Cr:YSGG laser at 1.5, 1.75
and 2.0 W and 20 Hz, with water spray.31
The surfaces prepared with the Erbium laser are
well cleaned and without smear layer, but often con-

tain ledges, irregularities and charring with the risk of
perforations or apical transportation. In effect, canal
shaping performed by Erbium laser is still a complicated
procedure today that can be performed only in large
and straight canals, without any particular advantages.

Figs. 7,8_SEM images of radiated
dentine with diode 810nm laser (dry,
1.5W, 15 Hz) with 50 percent ton-toff
and 200 µm fiber, showing evidence
of thermal effects, with detachment
and smear layer.

Decontamination of the endodontic system
Studies on canal decontamination refer to the
action of chemical irrigants (NaClO) commonly used
in endodontics, in combination with chelating substances for better cleaning of the dentinal tubules
(citric acid and EDTA). One such study is that of Berutti
et al., who reported the decontaminating power of
NaClO up to a depth of 130 µm on the radicular wall.32
Lasers were initially introduced in endodontics in
an attempt to increase the decontamination of the
endodontic system.2–7
All the wavelengths have a high bactericidal
power because of their thermal effect, which, at different powers and with differing ability to penetrate
the dentinal walls, generates important structural
modifications in bacteria cells. The initial damage
takes place in the cell wall, causing an alteration of
the osmotic gradient, leading to swelling and cellular
death.16,34
Decontamination with near infrared laser
Laser-assisted canal decontamination performed
with the near infrared laser requires the canals to be
prepared in the traditional way (apical preparation
with ISO 25/30), as this wavelength has no affinity
and therefore no ablative effect on hard tissue. The
radiation is performed at the end of the traditional

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I trends_lasers
Figs. 9,10_SEM images of irradiated
dentine with Er,Cr:YSGG laser (1.0 W,
20 Hz, 1 mm to the apex), spray off
and canal irrigated with physiological
solution, showing evidence of smear
layer and thermal damage.
Figs. 11,12_SEM images of
irradiated dentine with Er,Cr:YSGG
laser (1.5 W, 20 Hz) with air/water
spray of 45/35 percent, showing
open dentinal tubules without
evidence of a smear layer. Note the
typical pattern of laser ablation, both
on the organic and inorganic dentine.

40 I roots
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Fig. 9

Fig. 10

Fig. 11

Fig. 12

endodontic preparation as a final means of decontaminating the endodontic system before obturation. An optical fibre of 200 µm diameter is placed
1 mm from the apex and retracted with a helical
movement, moving coronally (in five to 10 seconds
according to the different procedures). Today, it is
advisable to perform this procedure in a canal filled
with endodontic irrigant (preferably, EDTA or citric
acid; alternatively, NaClO) to reduce the undesirable
thermal morphological effects.9,35–38
Using an experimental model, Schoop et al. demonstrated the manner in which lasers spread their
energy and penetrate into the dentinal wall, showing
them to be physically more efficient than traditional
chemical irrigating systems in decontaminating
the dentinal walls.8 The Neodymium:YAG (Nd:YAG;
1,064nm) laser demonstrated a bacterial reduction
of 85 percent at 1 mm, compared with the diode
laser (810nm) with 63 percent at 750 µm or less. This
marked difference in penetration is due to the low
and varying affinity of these wavelengths for hard
tissue. The diffusion capacity, which is not uniform,
allows the light to reach and destroy bacteria by penetration via the thermal effects (Fig. 1).
Many other microbiological studies have confirmed the strong bactericidal action of the diode and
Nd:YAG lasers, with up to 100 percent decontamination of the bacterial load in the principal canal.39–43 An
in vitro study by Benedicenti et al. reported that the
use of the diode 810 nm laser in combination with
chemical chelating irrigants, such as citric acid and
EDTA, brought about a more or less absolute reduc-

tion of the bacterial load (99.9 percent) of E. faecalis
in the endodontic system.9
Decontamination with medium infrared laser
Considering its low efficacy in canal preparation and
shaping, using the Erbium laser for decontamination in
endodontics requires the use of traditional techniques
in canal preparation, with the canals prepared at the
apex with ISO 25/30 instruments. The final passage
with the laser is possible thanks to the use of long, thin
tips (200 and 320 µm), available with various Erbium
instruments, allowing for easier reach to the working
length (1 mm from apex). In this methodology, the traditional technique is to use a helical movement when
retracting the tip (over a five- to 10-second interval),
repeating three to four times depending on the procedure and alternating radiation with irrigation using
common chemical irrigants, keeping the canal wet,
while performing the procedure (NaClO and/or EDTA)
with the integrated spray closed.
The 3-D decontamination of the endodontic system with Erbium lasers is not yet comparable to that
of near infrared lasers. The thermal energy created
by these lasers is in fact absorbed primarily on the
surface (high affinity to dentinal tissue rich in water),
where they have the highest bactericidal effect on E.
coli (Gram-negative bacteria), and E. faecalis (Grampositive bacteria). At 1.5 W, Moritz et al. obtained
an almost total eradication (99.64 percent) of these
bacteria.44 However, these systems do not have a
bactericidal effect at depth in the lateral canals, as

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trends_lasers

they only reach 300 µm in depth when tested in the
width of the radicular wall.8
Further studies have investigated the ability
of the Er,Cr:YSGG laser in the decontamination of
traditionally prepared canals. Using low power (0.5
W, 10 Hz, 50 mJ with 20 percent air/water spray),
complete eradication of bacteria was not obtained.
However, better results for the Er,Cr:YSGG laser were
obtained with a 77 percent reduction at 1 W and of
96 percent at 1.5 W.42
A new area of research has investigated the
Erbium laser’s ability to remove bacterial biofilm
from the apical third,46 and a recent in vitro study
has further validated the ability of the Er:YAG laser
to remove endodontic biofilm of numerous bacterial species (e.g. A. naeslundii, E. faecalis, L. casei, P.
acnes, F. nucleatum, P. gingivalis or P. nigrescens),
with considerable reduction of bacterial cells and
disintegration of biofilm. The exception to this is the
biofilm formed by L. casei.47
Ongoing studies are evaluating the efficacy of a
new laser technique that uses a newly designed both
radial and tapered stripped tip for removal of not
only the smear layer, but also bacterial biofilm.13 The
results are very promising.
The Erbium lasers with “end firing” tips — frontal
emission at the end of the tip — have little lateral
penetration of the dentinal wall. The radial tip was
proposed in 2007 for the Er,Cr:YSGG, and Gordon et
al. and Schoop et al. have studied the morphological
and decontaminating effects of this laser system
(Fig. 2).48–50
The first study used a tip of 200 µm with radial
emission at 20Hz with air/water spray (34 and 28 percent) and dry at 10 and 20 mJ and 20 Hz (0.2 and 0.4
W, respectively). The radiation times varied from 15
seconds to two minutes. The maximum bactericidal
power was reached at maximum power (0.4 W), with
a longer exposure time, without water in dry mode
and with a 99.71 percent bacterial eradication.
The minimum time of radiation (15 seconds) with
minimum power (0.2 W) and water obtained 94.7
percent bacterial reduction.48

Fig. 14

Fig. 13

The second study used a tip of 300 µm diameter
with two different parameters of emission (1 and 1.5
W, 20 Hz), radiating five times for five seconds, with a
cooling time of 20 seconds for each passage. The level
of decontamination obtained was significantly high,
with important differences between 1 and 1.5 W,
with a thermal increase contained between 2.7 and
3.2 degrees C.49 The same group from Vienna studied
other parameters (0.6 and 0.9 W) that produced a
very contained thermal rise of 1.3 and 1.6 degrees C,
respectively, showing a high bactericidal effect on E.
coli and E. faecalis.50
The need to take advantage of the thermal effect
to destroy bacterial cells, however, results in changes
at the dentinal and periodontal level. It is important to
evaluate the best parameters and explore new techniques that reduce the undesirable thermal effects
that lasers have on hard- and soft-tissue structures
to a minimum.
Morphological effects on the dentinal surface

Fig. 13_Localization 1 mm from
the apex of the fiber and tips of the
near and medium infrared lasers.
According to the LAI technique, the
tip must be localized in the middle
third of the canal, approximately
5 mm from the apex (on the right).

Numerous studies have investigated the morphological effects of laser radiation on the radicular
walls as collateral effects of root-canal decontamination and cleaning performed with different lasers.
When they are used dry, both the near and medium

Figs. 14–16_PIPS tip, radial firing,
in quartz, 400 µ. The 3 mm terminals
were deprived of their outer coating
to increase the lateral dispersion
of energy.

Fig. 15

Fig. 16

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I 41

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I trends_lasers

Fig. 17

Fig. 18

Fig. 19

Fig. 20

Fig. 21

Fig. 22

Figs. 17–19_ SEM images of
radiated dentine with radial firing
tip, at 20 and 50 mJ, 10 Hz for
20 and 40 seconds, respectively,
in a canal irrigated with EDTA,
showing noticeable cleaning
of debris and smear layer from
the dentine and exposure of
the collagen structure. (Figures
courtesy of
Dr. Enrico DiVito)
Fig. 20_SEM images of radicular
dentine covered with bacterial
biofilm of E. faecalis before laser
radiation.
Figs. 21,22_SEM images of
radicular dentine covered with
bacterial biofilm of E. faecalis
after radiation with Er:YAG
laser (20 mJ, 15 Hz, PIPS tip)
with irrigation (EDTA), showing
destruction and detachment
of bacterial biofilm and its
complete vaporisation from the
principal root canal and from
lateral tubules. (Figures 21–25d
courtesy of Dr. Enrico DiVito and
Dr. David Jaramillo)

42 I roots
1_ 2012

infrared lasers produce characteristic thermal effects
(Figs. 3,4).51 Near infrared lasers cause characteristic
morphological changes to the dentinal wall: the
smear layer is only partially removed and the dentinal
tubules are primarily closed as a result of melting of
the inorganic dentinal structures. Re-crystallisation
bubbles and cracks are evident (Figs. 5–8).52–55
Water present in the irrigation solutions limits the
thermal interaction of the laser beam on the dentinal
wall and, at the same time, works thermally activated
by a near infrared laser or directly vaporized by a
medium infrared laser (target chromophore) with its
specific action (disinfecting or chelating). The radiation with the near infrared laser — diode (2.5 W, 15
Hz) and Nd:YAG (1.5 W, 100 mJ, 15 Hz) — performed
after using an irrigating solution, produces a better
dentinal pattern, similar to that obtained with only
an irrigant.
Radiation with NaClO or chlorhexidine produces
a morphology with closed dentinal tubules and
presence of a smear layer, but with a reduced area of
melting, compared with the carbonization seen with
dry radiation. The best results were obtained when
radiation followed irrigation with EDTA, with surfaces cleaned of the smear layer, with open dentinal
tubules and less evidence of thermal damage.35–38 In
the conclusion of their studies on the Erbium laser,
Yamazaki et al. and Kimura et al. affirmed that water
is necessary to avoid the undesirable morphological
aspects markedly present when radiation with the
Erbium lasers is performed dry.56,57 The Erbium lasers
used in this way result in signs of ablation and thermal damage as a result of the power used. There is
evidence of ledge cracks, areas of superficial melting
and vaporisation of the smear layer.

A typical pattern arises when dentine is irradiated
with the Erbium laser in the presence of water. The
thermal damage is reduced and the dentinal tubules
are open at the top of the peri-tubular more calcified
and less ablated areas. The inter-tubular dentine,
which is richer in water however, is more ablated. The
smear layer is vaporized by radiation with Erbium
lasers and is mostly absent.58–64 Shoop et al., investigating the variations of temperature on the radicular
surface in vitro, found that the standardised energies
(100 mJ, 15 Hz, 1.5 W) produced a measured thermal
increase of only 3.5 degrees C on the periodontal
surface. Moritz proposed these parameters as the
international standard of use for the Erbium laser
in endodontics, claiming it as an efficient means of
canal cleaning and decontamination (Figs. 9–12).14,16
Even with Erbium lasers, it is advisable to use
irrigating solutions. Alternatively, NaClO and EDTA
can be utilized during the terminal phase of laserassisted endodontic therapy with a resulting dentinal
pattern, with fewer thermal effects. This represents
a new area of research in laser-assisted endodontics.
Various techniques have been proposed, such as
laser-activated irrigation (LAI) and photon-initiated
photoacoustic streaming (PIPS).
Photo-thermal and photomechanical phenomena
for the removal of smear layer
George et al. published the first study that examined the ability of lasers to activate the irrigating
liquid inside the root canal to increase its action. In
this study, the tips of two laser systems — Er:YAG and
Er,Cr:YSGG (400 µm diameter, both flat and conical
tips) with the external coating chemically removed —

[43] =>

trends_lasers

were used to increase the lateral diffusion of energy.
The study was designed to irradiate the root canals
that were prepared internally with a dense smear
layer grown experimentally. Comparing the results of
the groups that were laser radiated with the groups
that were not, the study concluded that the laser
activation of irrigants (EDTAC, in particular) brought
about better cleaning and removal of the smear layer
from the dentinal surfaces.65 In a later study, the
authors reported that this procedure, using power of
1 and 0.75 W, produces an increase in temperature
of only 2.5 degrees C without causing damage to the
periodontal structures.66
Blanken and De Moor also studied the effects of laser
activation of irrigants comparing it with conventional
irrigation (CI) and passive ultrasound irrigation (PUI). In
this study, 2.5 percent NaClO and the Er,Cr:YSGG laser
were used four times for five seconds at 75 mJ, 20 Hz,
1.5 W, with an endodontic tip (200 µm diameter, with
flat tip) held steady 5 mm from the apex.
The removal of the smear layer with this procedure led to significantly better results with respect
to the other two methods.67 The photomicrographic
study of the experiment suggests that the laser generates a movement of fluids at high speed through
a cavitation effect. The expansion and successive
implosion of irrigants (by thermal effect) generates
a secondary cavitation effect on the intra-canal
fluids. It was not necessary to move the fiber up and
down in the canal, but sufficient to keep it steady in
the middle third, 5 mm from the apex.68 This concept
greatly simplifies the laser technique, without the
need to reach the apex and negotiate radicular
curves (Fig. 13).
De Moor et al. compared the LAI technique with
PUI and they concluded that the laser technique, using lower irrigation times (four times for five seconds),
gives results comparable to the ultrasound technique
that uses longer irrigation times (three times for 20
seconds).69 De Groot et al. also confirmed the efficacy
of the LAI technique and the improved results obtained
in comparison with the PUI. The authors underlined
the concept of streaming due to the collapse of the
molecules of water in the irrigating solutions used.70
Hmud et al. investigated the possibility of using near
infrared lasers (940 and 980 nm) with 200 µm fibre to
activate the irrigants at powers of 4 W and 10 Hz, and
2.5 W and 25 Hz, respectively. Considering the lack of
affinity between these wavelengths and water, higher
powers were needed which, via thermal effect and cavitation, produced movement of fluids in the root canal,
leading to an increased ability to remove debris and the
smear layer.71 In a later study, the authors also verified
the safety of using these higher powers, which caused
a rise in temperature of 30 degrees C in the intra-canal
irrigant solution but of only 4 degrees C on the external
radicular surface. The study concluded that irrigation

Figs. 23a–d_Clockwose from lower
left: Confocal microscope images of
the dentine of the root canal covered
with biofilm (a). View in fluorescent
light of bacterial biofilm (in green; b).
Dentine autofluorescence (in red; c).
3-D view superimposed (d).
Fig. 23b

Fig. 23c

Fig. 23a

Fig. 23d

activated by near infrared lasers is highly effective in
minimizing the thermal effects on the dentine and the
radicular cement.72
In a recent study, Macedo et al. referred to the main
role of activation as a strong modulator of the reaction rate of NaOCl. During a rest interval of three minutes, the consumption of available chlorine increased
significantly after LAI compared with PUI or CI.73
Photon initiated photoacoustic streaming (PIPS)
The PIPS technique uses the Erbium laser (Powerlase AT/HT and LightWalker AT, both Fotona) and
its interaction with irrigating solutions (EDTA ,
NaOCL or distilled water).13 The technique uses a
different mechanism from the preceding LAI. It exploits exclusively the photoacoustic and photomechanical phenomena, which result from the use of
subablative energy of 20 mJ at 15 Hz, with impulses
of only 50 microseconds. With an average power of
only 0.3 W, each impulse interacts with the water
molecules with a peak power of 400 W creating
expansion and successive “shock waves” leading to
the formation of a powerful streaming of fluids in-

Fig. 24b

Fig. 24c

Fig. 24a

Fig. 24d

Figs. 24a–d_Clockwise from lower
left: Confocal microscope images of
the dentine of lateral tubules covered
in biofilm (a). View in fluorescent
light of bacterial biofilm (in green; b).
Dentine autofluorescence (in red; c).
3-D view superimposed (d).

roots
1
_ 2012

I 43

[44] =>

I trends_lasers
Figs. 25a–d_Clockwise from lower
left: Confocal microscope image of
dentine (a). Autofluorescence with no
sign of bacteria (b & c).
3-D view superimposed (d).

Fig. 25b

Fig. 25c

of Genoa and the University of Loma Linda School of
Dentistry, University of Tennessee, Boston University,
Louisiana State University and the Arizona School of
Dentistry and Oral Health, are currently investigating
the effects of this technique of root-canal decontamination and the removal of bacterial biofilm in
the radicular canal. The results, which are about to be
published, are very promising (Figs. 20–25).

_Discussion and conclusion

Fig. 25a

Fig. 25d

side the canal, without generating the undesirable
thermal effects seen with other methodologies.
The study with thermocouples applied to the
radicular apical third revealed only 1.2 degrees C of
thermal rise after 20 seconds and 1.5 degrees C after
40 seconds of continuous radiation. Another considerable advantage is derived from the insertion of the
tip in the pulp chamber at the entrance to the root
canal only without the problematic insertion of the
tip into the canal or at 1 mm from the apex required
by the other techniques (LAI and CI). Newly designed
tips — 9 mm in length, 600 μm in diameter and with
“radial and stripped” tip — are used. The final 3 mm are
without coating to allow a greater lateral emission
of energy compared to the frontal tip. This mode of
energy emission makes better use of the laser energy
when, at subablative levels, delivery with very high
peak power for each single pulse of 50 microseconds
(400 W) produces powerful “shock waves” in the
irrigants, leading to a demonstrable and significant
mechanical effect on the dentinal wall (Figs. 14–16).
The resultant acoustic streaming allows for a three
dimensional movement throughout the root canal
system allowing the clinician to easier access the
complex anatomy often seen in the apical one third.
The studies show the removal of the smear layer
to be superior to the control groups with only EDTA
or distilled water. The samples treated with laser and
EDTA for 20 and 40 seconds show a complete removal
of the smear layer with open dentinal tubules (score 1
according to Hulsmann) and the absence of undesirable thermal phenomena, which is characteristic in the
dentinal walls treated with traditional laser techniques.
With high magnification, the collagen structure is
maintained intact, suggesting the ability for minimally
invasive endodontic treatment (Figs. 17–19).
The Medical Dental Advanced Technologies
Group, in affiliation with the University of the Pacific
Arthur A. Dugoni School of Dentistry, the University

44 I roots
1_ 2012

Laser technology used in endodontics in the past
20 years has undergone an important evolution. The
improved technology has introduced endodontic fibers
and tips of a caliber and flexibility that permit insertion
up to 1 mm from the apex. Research in recent years has
been directed toward producing technologies (impulses
of reduced length, “radial firing and stripped” tips) and
techniques (LAI and PIPS) that are able to simplify its use
in endodontics and minimize the undesirable thermal
effects on the dentinal walls, using lower energies in
the presence of chemical irrigants. EDTA has proved
to be the best solution for LAI technique that activates
the liquid and increments its chelating capacity and
cleaning of the smear layer. The use of NaClO increases
its decontamination activity. Finally, the PIPS technique
reduces the thermal effects and exerts a potent cleaning
and bactericidal action thanks to its three dimensional
streaming of fluids initiated by the photonic energy of
the laser. Further studies are currently under way to
validate these techniques (LAI and PIPS) as innovative
technologies available to endodontics._
Editorial note: An earlier version of this article was
published in the international edition of roots, issue
2/2011. A complete list of references is available from
the publisher.

_about the author

roots

Enrico DiVito, DDS, the
lead author of this article,
founded his dental practice in Scottsdale, Ariz.,
in 1980. He is also the
founder and director of the
state-accredited Arizona
School of Dental Assisting.
In addition to teaching at the
school, DiVito is also a clinical instructor at the Arizona
School of Dentistry and Oral Health and is responsible
for helping create the Department of Laser Dentistry.
He earned his undergraduate degree from Arizona State
University and graduated with honors from the Dental
School at the University of the Pacific in San Francisco,
receiving several Clinical Excellence Awards. He can be
contacted at edivito@azcld.com.

[45] =>

[46] =>

I industry_Carestream Dental

9000 3D extraoral
imaging system
_Carestream Dental’s focused field cone beam
CT (CBCT), the 9000 3D extraoral imaging system, is adding dimension to endodontic treatment
planning. This CBCT imaging solution is consistently
chosen by endodontists, as it provides the advantages of high resolution and relatively low dose focused field of view 3-D imaging at an affordable price.
Found in more than one-third of the graduate endodontic residency programs throughout the United
States and Canada, the 9000 3D has been featured in
numerous endodontic studies showing the efficacy
of CBCT in endodontics. Most importantly, the 9000
3D system’s localized field of view limits irradiation
to the patient, while providing highly detailed images
of the region of interest.
The all-in-one 9000 3D is a versatile multi-modality imaging system designed to meet today’s needs.
The unit comes with a focused-field of view (approximately 4 x 5 cm), but can be expanded through the
“extended field of view” upgrade option that allows
for capturing a full jaw in a single scan. In addition
to its exceptional 3-D imaging capabilities, it also
offers 2-D digital panoramic imaging with variable
focal trough technology that’s crystal clear, every
time. It even has a one-shot cephalometric imaging
modality upgrade option. For practitioners who have
been waiting to integrate cone beam computed tomography into their practice, this is the perfect option.
The growth of CBCT and ensuing adoption rates in
endodontics is even more apparent at this year’s AAE
educational sessions, where more than 10 percent
include coverage on CBCT. “So many customers have
shared with me the positive impact their practices
have seen since the addition of the 9000 3D,” says
Jordan Reiss, Carestream Dental’s U.S. sales director
of endodontics. “We are excited to have our custom-

_contact

roots

For more information, contact Carestream Dental at
(800) 944-6365 or visit www.
carestreamdental.com/aae.

46 I roots
1_ 2012

ers presenting cases at our AAE booth that exemplify
not just how much our software sets us apart from
other systems, but how high-resolution 3-D imaging
is aiding in patient care.”
Carestream Dental proudly supports education
throughout the year with webinars, seminars and
hands-on workshops. The 2012 AAE Annual Session
in Boston is a great example of the culmination of the
company’s efforts to help endodontists understand
this imaging modality even better. As a Diamond
sponsor, Carestream Dental is delivering on AAE’s
session goal of “Forging the Future” by sponsoring
both the “Evidence-Based Endodontics” and “Exploring the Future” educational tracks.
The CS 3D imaging intuitive sharable software
makes case collaboration easy. Carestream Dental’s
imaging software is available free to share with referring doctors. With one click of a button, the full software and 3-D data can be placed on a flash drive or CD.
“One of the unique features of the 9000 3D system
is the ease with which you can realign the viewing
plane with the long access of the tooth,” says Dr.
Randolph Todd, a diplomate of the ABE and a practicing endodontist in New York City. “The traditional
‘hunting’ to find the opening of the canal is no longer
a problem. Canals not previously observable on 2–D
radiographs are easily discernible and treated.”
Carestream Dental has a long history of manufacturing and selling dental imaging solutions under the
PracticeWorks and Kodak Dental Systems brands. The
9000 3D system from Carestream Dental has been
dominating the endodontic market since its release.
Well known for its product line that includes digital
intraoral sensors, intraoral cameras, and complete imaging software solutions, more than 1 million dentists
in 120 countries use Carestream products._

[47] =>

[48] =>

[49] =>

about the publisher _ submissions

I

submissions

formatting requirements
Please note that all the textual elements
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Managing Editor Sierra Rendon
s.rendon@dental-tribune.com

		

roots
I 49
1
_ 2012

[50] =>

I about the publisher _ imprint

roots

the international C.E. magazine of endodontics
U.S. Headquarters
Dental Tribune America
116 West 23rd Street, Ste. 500
New York, NY 10011
Tel.: (212) 244-7181
Fax: (212) 244-7185
feedback@dental-tribune.com
www.dental-tribune.com
Publisher
Torsten R. Oemus
t.oemus@dental-tribune.com
Chief Operating Officer
Eric Seid
e.seid@dental-tribune.com

Managing Editor
Fred Michmershuizen
f.michmershuizen@dentaltribune.com
Managing Editor
Sierra Rendon
s.rendon@dental-tribune.com
Designer
Kristine Colker
k.colker@dental-tribune.com
C.E. Director
Christiane Ferret
c.ferret@dtstudyclub.com

Marketing Manager
Group Editor
Anna Wlodarczyk-Kataoka
Robin Goodman
r.goodman@dental-tribune.com a.wlodarczyk@dental-tribune.com
Editor in Chief
Fred Weinstein,

DMD, MRCD(C), FICD

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Accounting
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Product/Account Manager
& Interactive
Gina Davison
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dr.fred@telus.net

Editorial Board

Marcia Martins Marques, Leonardo
Silberman, Emina Ibrahimi, Igor Cernavin,
Daniel Heysselaer, Roeland de Moor, Julia
Kamenova, T. Dostalova, Christliebe Pasini,
Peter Steen Hansen, Aisha Sultan, Ahmed
A Hassan, Marita Luomanen, Patrick Maher,
Marie France Bertrand, Frederic Gaultier,
Antonis Kallis, Dimitris Strakas, Kenneth Luk,
Mukul Jain, Reza Fekrazad, Sharonit
Sahar-Helft, Lajos Gaspar, Paolo Vescovi,
Marina Vitale, Carlo Fornaini, Kenji Yoshida,
Hideaki Suda, Ki-Suk Kim, Liang Ling Seow,
Shaymant Singh Makhan, Enrique Trevino,
Ahmed Kabir, Blanca de Grande, José Correia
de Campos, Carmen Todea, Saleh Ghabban
Stephen Hsu, Antoni Espana Tost, Josep
Arnabat, Ahmed Abdullah, Boris Gaspirc,
Peter Fahlstedt, Claes Larsson, Michel Vock,
Hsin-Cheng Liu, Sajee Sattayut, Ferda Tasar,
Sevil Gurgan, Cem Sener, Christopher Mercer,
Valentin Preve, Ali Obeidi, Anna-Maria
Yannikou, Suchetan Pradhan, Ryan Seto, Joyce
Fong, Ingmar Ingenegeren, Peter Kleemann,
Iris Brader, Masoud Mojahedi, Gerd Volland,
Gabriele Schindler, Ralf Borchers, Stefan
Grümer, Joachim Schiffer, Detlef Klotz,
Herbert Deppe, Friedrich Lampert, Jörg
Meister, Rene Franzen, Andreas Braun, Sabine
Sennhenn-Kirchner, Siegfried Jänicke, Olaf
Oberhofer and Thorsten Kleinert

International Account Manager
Jan Agostaro
j.agostaro@dental-tribune.com
Dental Tribune America is the official media partner of:

roots_Copyright Regulations
_the international C.E. magazine of roots published by Dental Tribune America is printed quarterly. The magazine’s articles and illustrations are protected by copyright. Reprints of any kind, including digital mediums, without the prior consent of the publisher are inadmissible
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Dental Tribune strives to maintain the utmost accuracy in its clinical articles. If you find a factual error or content that requires clarification, please contact Group Editor Robin Goodman at r.goodman@dental-tribune.com. Opinions expressed by authors are their own and
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Dental Tribune cannot assume responsibility for the validity of product claims or for typographical errors. The publisher also does not
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50 I roots
1_ 2012

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