Cover / Editorial / Content / Restoration of endodontic teeth: An engineering perspective / Microendodontics? Finding the sweet spot between effective instrumentation and maximal tooth strength / PIPS and retreatment / Industry / Imprint
Cover
01 - 01 viewEditorial
03 - 03 viewContent
04 - 04 viewRestoration of endodontic teeth: An engineering perspective
06 - 12 viewMicroendodontics? Finding the sweet spot between effective instrumentation and maximal tooth strength
13 - 16 viewPIPS and retreatment
18 - 19 viewIndustry
20 - 24 viewImprint
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[1] =>
roots
issn 2161-6558
the international C.E. magazine of
3
2014
_C.E. article
Restoration of endodontic
teeth: An engineering
perspective
_technique
Microendodontics?
_trends
Laser therapy
North America Edition • Vol. 5 • Issue 3/2014
endodontics
[2] =>
[3] =>
editorial _ roots
Fall is here, and
it’s time to go
back to school
I
Fred Weinstein, DMD, MRCD(C),
FICD, FACD
For me, autumn always brings memories of going back to school. It’s always exciting to learn new
things — which is why the magazine you are holding is so valuable.
In this issue of roots, you can find many helpful articles.
Dr. Gregory Kurtzman offers his opinion on restoration from an engineering perspective. Dr. Eric
Herbranson presents an article on what he calls finding the “sweet spot” between effective instrumentation and maximal tooth strength. Dr. Reid Pullen describes using laser technology in a retreatment
case. There’s also an article about a three-day course available at the Las Vegas Institute for Advanced
Dental Studies.
By reading the article by Dr. Kurtzman, and then taking a short online quiz about his article at www.
DTStudyClub.com, you will gain one ADA CERP-certified C.E. credit. Keep in mind that because 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. You need only register at the Dental Tribune Study Club website to access these C.E. materials free of
charge. You may take the C.E. quiz after registering on the DT Study Club website.
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 will enjoy this issue
and that you will take advantage of the C.E. opportunity.
For those of you attending the ADA meeting this fall in San Antonio, be sure to say hello in person. I’ll
also be at the upcoming Greater New York Dental Meeting this November.
As always, I welcome your comments and feedback.
Sincerely,
Fred Weinstein, DMD, MRCD(C), FICD, FACD
Editor in Chief
roots
3
I 03
_ 2014
[4] =>
I content_ roots
page 13
page 06
I C.E. article
06
estoration of endodontic teeth:
R
An engineering perspective
page 18
I about the publisher
26
_imprint
_Gregori M. Kurtzman, DDS, MAGD, FAAIP, FPFA,
FACD, FADI, DICOI, DADIA
I technique
13 Microendodontics?
_Eric Herbranson, DDS, MS, FDIC
roots
North America Edition • Vol. 5 • Issue 3/2014
issn 2161-6558
I trends
18 PIPS and retreatment
the international C.E. magazine of
endodontics
_Reid Pullen, DDS, FAGD
I education
3
20 LVI Core I three-day course is designed for
doctors and their teams to learn together
_Mark Duncan, DDS, FAGD, LVIF, DICOI, FICCMO
I industry
22
Seiler microscopes
24
What is the first thing that comes to mind?
page 20
04 I roots
3_ 2014
2014
_C.E. article
Restoration of endodontic
teeth: An engineering
perspective
_technique
Microendodontics?
_industry education
LVI Core I three-day course
is designed for doctors and
their teams to learn together
I on the cover
A cleared tip of the mesial root of a lower left first molar.
Specimen provided by Dr. Taylor Gehring, processing and
photography by Dr. Craig Barrington.
page 22
page 24
[5] =>
[6] =>
I C.E. article_ restoration
Restoration of
endodontic teeth: An
engineering perspective
Author_Gregori M. Kurtzman, DDS, MAGD, FAAIP, FPFA, FACD, FADI, DICOI, DADIA
_c.e. credit
_Introduction
This article qualifies for C.E.
credit. To take the C.E. quiz, log
on to www.dtstudyclub.com.
Click on ‘C.E. articles’ and
search for this edition (Roots
C.E. Magazine — 3/2014). If
you are not registered with the
site, you will be asked to do so
before taking the quiz. You may
also access the quiz by using
the QR code below.
Identifying the canals and negotiating them
to be able to instrument and obturate the tooth is
necessary to clinical success. But restoration of the
endodontically treated tooth is critical to long-term
success. It does not matter if we can complete the
endodontic portion of treatment if the tooth cannot
be restored. With this in mind, we need to look at the
restoration phase from an engineering perspective.
What is needed to reinforce the remaining tooth so
that it can manage the repetitive loading that occurs during mastication? This article will discuss the
importance of ferrule in adhesive dentistry as well as
when to use posts and what materials are best.
_Ferrule: How important is it today?
Ferrule has long been an important concept in
dentistry but has been de-emphasized with the
Fig. 1_Strain analysis of a posterior
tooth demonstrating concentration
of strain on loading at the cervical.
(Image/Provided by Dr. Gene McCoy)
06 I roots
3_ 2014
Fig. 1
bonding evolution. Yet this concept is as important
today as it was prior to dental bonding. But what
is a ferrule? A ferrule is a band that encircles the
external dimension of residual tooth structure, not
unlike the metal bands that exist around a barrel to
hold the slats together.
Sufficient vertical height of tooth structure
that will be grasped by the future crown is necessary to allow for a ferrule effect of the future prosthetic crown; it has been shown to significantly
reduce the incidence of fracture in the endodontically treated tooth.1,2
Important to this concept is the margin design
of the crown preparation, which may include a
chamfer or a shoulder preparation. Because a
chamfer margin has a beveled area that is not
parallel to the vertical axis of the tooth, it does not
properly contribute to ferrule height. Therefore,
when a chamfer is utilized it would require an additional 1 mm of height between the edge of the
margin and the top aspect of the coronal portion
of remaining tooth structure.
Thus, use of a chamfer may not be the best margin
design when restoring endodontically treated teeth
or those teeth with significant portions of missing
tooth structure. With today’s movement toward
scanning and milling for fixed prosthetics, whether
done in the practitioner’s office or at the laboratory,
it should be noted that it is difficult to scan the internal aspect of a shoulder preparation, and it has been
uniformly recommended that a rounded shoulder
be used. The rounded shoulder preparation provides
the maximum vertical wall at the margin, with the
internal aspect being slightly rounded versus at a
90-degree angle. This ensures better replication of
the margins when scanned and milled.
[7] =>
C.E. article_ restoration
I
Fig. 2_As a maxillary anterior tooth
is loaded during mastication, tension
and compression occur at the
crown’s margins. (Images/Provided
by Dr. Gregori M. Kurtzman)
Fig. 3_Opening of the margin on
the tension side may lead in time to
recurrent decay or restoration and
endodontic failure.
Fig. 3
Fig. 4_Difference of intensity of
strain and location related to ferrule
height during occlusal loading
(Libman).
Fig. 2
Some studies suggest that while ferrule is certainly desirable, it should not be provided at the
expense of the remaining tooth/root structure.3
Alternatively, it has also been shown that the difference between an effective, long-term restoration
and restorative failure can be as small as 1.0 mm of
additional tooth structure that, when encased by a
ferrule, provides greater protection.
When such a long-lasting, functional restoration cannot be predictably created, osseous crown
lengthening should be considered to increase what
tooth structure is available to achieve a ferrule, but
this is also dependent on the periodontal status
of the tooth, and when ferrule cannot be achieved
then extraction should be considered.4 Ichim, et al,
stated succinctly, “The study confirms that a ferrule
increases the mechanical resistance of a post/core/
crown restoration.”5
_How much ferrule is required?
When rebuilding an endodontically treated tooth,
it is best to maintain all dentin that is available, even
thin slivers. These thin slivers of dentin provide a
strong connecting link between the core and tooth’s
root and between the crown and root.6
It is important to attempt to retain as much
tooth structure as possible, and this aids in achieving ferrule as well as maintaining cervical strength
of the tooth where loading concentrates. Under
masticatory loading, strain concentrates at the cervical portion of teeth; thus it is important to avoid
over-preparation of this portion of the tooth during
endodontic treatment and preserve this area during
restoration of the tooth (Fig. 1).
Fig. 4
Multiple studies discussing how much ferrule
is required have found that teeth with at least
2.0 mm of ferrule have significantly greater
long-term prognosis from a restorative standpoint than those with less or no ferrule. Libman,
et al, reported, “Fatigue loading of cast post and
cores with complete crowns of different ferrule
designs provide evidence to support the need
for at least a 1.5- to 2.0-mm ferrule length of
a crown preparation. Crown preparation with a
0.5-mm and 1.0-mm ferrule failed at a significantly lower number of cycles than the 1.5-mm
and 2.0-mm ferrules and control teeth.”7
Libman further demonstrated when loading at
an off-axis direction, which occurs in the maxillary anterior, at the restoration’s margin, the side
where the load is originating is under tension,
whereas the opposing side is under compression
(Fig. 2). This repetitive loading and micro strain due
to tension at the lingual margin leads to the margin
opening, which may lead to recurrent decay and/
or failure of the endodontic seal or restoration
(Fig. 3).
Additionally, if we look at strain studies by
Libman and others comparing ferrule of different
heights, we observe that in a ferrule of 0.5 mm
there is greater strain at the margin under tension
and concentrates at mid tooth where the core
or post is situated. Teeth with 2.0 mm of ferrule
demonstrated significantly less strain loading
at the margins or center of the cervical aspect
of the tooth. The lower the strain at the cervical
roots
3
I 07
_ 2014
[8] =>
I C.E. article_ restoration
Fig. 5
Fig. 5_Comparison of load
distribution of fiber post, cast metal
post and prefabricated metal post.
midpoint, the less chance of overload and failure
restoratively (Fig. 4).
_Detecting failure at the coronal seal
It is not unusual to have a patient present for
a routine recall appointment and the clinician or
hygienist note recurrent decay at a crown margin
with the patient unaware of the issue. This becomes
more complicated with teeth that have previously
undergone endodontic treatment, as there is no
pulp present that could warn the patient an issue
is present until often extensive decay occurs or the
crown dislodges from the remaining tooth.
Freeman, et al, in their published study, stated,
“Fatigue loading of three different post and core
designs with the presence of a full cast crown leads
to preliminary failure of leakage between the restoration and tooth that is clinically undetectable.”8
The literature supports that coronal leakage may
be a major factor in failure of endodontic treatment.9–11 As previously discussed, when loaded
during mastication, margins with inadequate ferrule
may demonstrate micro opening on the tension side,
leading to leakage over time.
This initially may be observed as recurrent decay, but
as it deepens and exposure of the obturation material
results, failure of the endodontics may result due to apical migration of oral bacteria. This is minimized when a
bonded core or post/core is present, but given sufficient
time when a ferrule of sufficient height is not present
the endodontics or the restoration will fail.
_Do all posts function the same?
Teeth function differently, depending on the
material that the post is fabricated from, with loads
08 I roots
3_ 2014
distributed within the root relative to the modulus of
elasticity of the post compared to the dentin of the
root (Fig. 5).
When a tooth restored with a fiber post does
fail due to overload, the mode of failure is coronal,
protecting remaining root and tooth structure.12 This
mode of failure with fiber-post-restored teeth typically allows the tooth to be restored, as vertical root
fracture is a rare occurrence.
Bitter reported, “Compared to metal posts, FRC
posts revealed reduced fracture resistance in vitro,
along with a usually restorable failure mode”13
(Fig. 6). Whereas, with metal posts either prefabricated
or cast, failure was at a higher value for cast post and
core: 91 percent of the specimens had fractured roots
(none of the specimens with a fiber post demonstrated
root fracture); and the post and core usually fractured
at the tooth composite core interface.14
As stress concentrates at the apical tip of the
metal post due to its higher modulus of elasticity
than the surrounding root, vertical root fracture is a
frequent occurrence (Fig. 7). This may result also from
breakdown of the cement luting the post to the root,
allowing slippage microscopically of the post in the
tooth under load, leading to torque at the cervical
area and the resulting vertical root fracture.
Because metal posts are stiffer (higher modulus
of elasticity) than the dentin of the root, stress concentrates at the post’s apical tip, leading to vertical
root fracture and catastrophic loss of the tooth.
Ansari reported, “The risk of failure was greater with
metal-cast posts (nine out of 98 metal posts failed)
than with carbon fiber posts (using which, none out
of 97 failed) risk ratio.”15 But with fiber posts having
a flexibility equal to or greater than the root (lower
modulus of elasticity), stress concentrated at the cervical region, leading to horizontal fracture of the post
and core; and typically the tooth can be salvaged.
The elastic modulus refers to the relative rigidity
of the material. The stiffer the material, the higher its
relative modulus. When two different materials are
placed together, such as when a post is placed into
a tooth’s root, the elastic modulus is influenced by
whichever of the materials is stiffest. Dentin averages
a modulus of elasticity of 17.5 (+/- 3.8) GPa, with
glass fiber posts at 24.4 (+/- 3.4) GPa, titanium prefabricated posts at 66.1 (+/- 9.6) GPa, prefabricated
stainless steel at 108.6 (+/- 10.7) GPa and cast high
noble gold posts at 53.4 (+/- 4.5) GPa.
Cast posts fabricated from noble or base metals
have higher modulus then high noble alloys and
approach stainless-steel prefabricated posts in their
relative stiffness. Fiber posts have an elastic modulus
that more closely approaches that of dentin (Fig. 8).
The flexural strength of fiber and metal posts was
respectively four and seven times higher than root
dentin, and there is still debate on whether a post
[9] =>
C.E. article_ restoration
Fig. 6_Tooth restored with a
fiber post demonstrating coronal
horizontal fracture supracrestally,
typically seen with teeth restored
with fiber posts when overloaded.
Fig. 7_Vertical root fracture of a tooth
restored with a metal post.
Fig. 8_Comparative modulus of
elasticity of different post materials.
Fig. 7
Fig. 6
strengthens the tooth.16,17 The basic purpose of a post
is to aid in retention of the core.
The absence of a cervical ferrule has been found to
be a determining negative factor, giving rise to considerably higher stress levels within the root. When
no ferrule was present, the prefabricated metal post/
composite combination generated greater cervical stress than cast post and cores. Yet, the ferrule
seemed to cancel the mechanical effect of the reconstruction material on the intensity of the stresses.
With a ferrule, the choice of reconstruction material had no impact on the level of cervical stress. The
root canal post, the purpose of which is to protect
the cervical region, was also shown to be beneficial
even with sufficient residual coronal dentin. In the
presence of a root canal post, cervical stress levels
were lower than when no root canal post was present.
Pierrisnard concluded that the higher the elasticity
modulus, the lower the stress levels.18
The material the post is fabricated from should
have the same modulus of elasticity as the root dentin to distribute the applied forces along the length
of the post and the root and not concentrate them
at the apical tip of the post. Studies have shown that
when components of different rigidity are loaded, the
more rigid component is capable of resisting forces
without distortion. This stress is concentrated when
the post is the stiffer material at the post’s apical tip.
The less-rigid component fails invariably when a post
is used that is stiffer than the root’s dentin.19
Posts with modulus of elasticity significantly
greater than that of dentin create stresses at the
tooth/cement/post interface, with the possibility of
post separation and failure. As repetitive loading
occurs on the endodontically restored tooth, the
Fig. 8
cement eventually fails at the interface between the
metal post and root dentin, allowing microslippage
of the post. This allows higher stresses to be exerted
on the root, leading to vertical root fracture and catastrophic loss of the tooth. The higher modulus (rigidity) of the metallic posts makes it stiff and unable to
absorb stresses. In addition, transmission of occlusal
and lateral forces through a metallic core and post
can concentrate stresses, resulting in the possibility of unfavorable fracture of the root.20 Dentin’s
modulus of elasticity is approximately 14 to 18 GPa.
Fiber posts have modulus that is approximately 9 to
50 GPa, depending on the manufacturer of the post.
This provides a similarity in elasticity between
the fiber post and dentin of the root, allowing post
flexion to mimic tooth flexion. The fiber post absorbs
and distributes the stresses and thus shows reduced
stress transmission to the root.21 The longitudinal arrangement of fibers in the fiber post and the modulus
of elasticity of a post that is less than or equal to
that of the dentin may redistribute the stress into
the tooth and away from the chamfered shoulder to
increase the likelihood of failure of the post core\root
interface instead of root fractures.
When failure does occur due to overloading,
failure typically is in the coronal portion, frequently
demonstrating fracture of the core at the tooth in-
roots
3
I 09
_ 2014
[10] =>
I C.E. article_ restoration
Fig. 9
Fig. 10
Fig. 9_Minimal tooth missing
or previously restored following
endodontic treatment.
Fig. 10_Moderate tooth missing
or previously restored following
endodontic treatment.
terface and leaving the possibility of re-restoring the
tooth and not catastrophic loss.22
The flexural properties of fiber posts were higher
than the metal post and similar to dentin.23
Whereas prefabricated, stainless-steel post exhibited
a significantly higher fracture resistance at failure when
compared with the fiber posts., the mode of failure of the
carbon fiber post was more favorable to the remaining
tooth structure when compared with the prefabricated,
stainless-steel post and the ceramic post.24
Ceramic posts were introduced prior to fiber posts as
a more esthetic alternative to prefabricated metal posts,
and, although not widely used today, they are still available. Modulus of elasticity of ceramic posts is 170-213
GPa, which is approximately 15 times that of dentin.
Because these ceramic posts are too rigid and transmit
more stress to the root canal than the fiber posts, which
lead to irreversible root damage via vertical root fracture
seen with metal posts, their use is not recommended in
restoring endodontically treated teeth today.25
tooth structure and has not been restored. Teeth
that have undergone endodontic treatment —
when either occlusal decay was present in the pits
and fissures leading to pulpal involvement, or a
small- to moderate-sized previously placed amalgam or composite restoration is present — require
conservative restoration (Fig. 9).
These teeth can be restored with removal of the
existing restorative material and cleaning the pulp
chamber of obturation material, including 2.0 to
3.0 mm of the canal.
Placement of a conventional composite bonded
within the tooth provides a good long-term restorative solution to these teeth, and a crown typically is
not needed. The access or existing restoration should
leave most of the cuspal width present. When the
preparation following removal of decay and existing
restorative materials invades the width of the cusp
leaving half of this tooth structure missing, more
extensive restoration is indicated.
_Decision making for restoration of teeth _Moderate tooth structure missing or
treated endodontically
previously restored
Restoration of endodontically treated teeth needs
to take an engineering view of how best to reconstruct
the remaining tooth for the best long-term survival.
With this in mind, the practitioner needs to categorize
the tooth based on how much native tooth structure is
present following endodontic treatment and how much
existing restorative material is currently present in the
tooth.
_Minimal tooth missing or previously
restored
Posterior teeth gain strength when the marginal ridge area and proximal surface is natural
10 I roots
3_ 2014
When the tooth to be restored is missing one
or both marginal ridges and these areas have been
previously restored or will be restored, placement of a
bonded composite will not suffice as the final restoration (Fig. 10). The marginal ridges provide resistance
to cuspal flexure of the tooth, improving its strength.
When these are missing, functional loading of
the tooth will allow greater cuspal flexure and
consequentially a higher chance of fracture under
masticatory function. Restoration of these teeth will
require a core buildup with optional pins or other
retentive elements for the core followed by a full
coverage crown. Posts are often not needed, as the
remaining tooth structure at the cusps after crown
[11] =>
C.E. article_ restoration
Fig. 11
preparation is sufficient to retain the core, and a ferrule can be achieved.
A post may be considered in those patients who
are bruxers or clenchers or whose occlusion may
place higher forces on the restored tooth due to the
tooth’s position relative to the occlusal plane. When
a ferrule cannot be achieved, the practitioner should
consider osseous crown lengthening or forced eruption to improve the ferrule.
Inlay restorations should be avoided in endodontically treated teeth because the access created to
perform the endodontic treatment weakens the tooth
from a cuspal flexure standpoint and the inlay even
when bonded may act as a wedge forcing the cusps
apart and leading to fracture of the tooth. An onlay restoration may be utilized, and its design should include
shoeing of the cusps to limit cuspal flexure.
I
Fig. 12
place and assists in preventing fracture of the post or
dislodgement under function that is observed when
only a single post is placed.
Use of pins may also be considered to assist in
retaining the core portion when cusps are missing
and as an augment to posts being placed. These teeth
require a full coverage crown to limit cuspal flexure
under load. As with teeth with moderate missing
tooth structure, use of inlays should be avoided
because they do not restrict cuspal flexure. An onlay
may be used if desired in some cases but should
include shoeing the cusps as part of the preparation
design to limit cuspal flexure. Again, when ferrule is
not achievable, consider osseous crown lengthening
or forced eruption to improve the ferrule.
Fig. 11_Significant tooth missing
or previously restored following
endodontic treatment.
Fig. 12_Multiple fiber posts placed
into a molar to lock the core to the
remaining tooth structure.
_Conclusion
_Significant tooth structure missing or
For restoration of endodontically treated teeth,
previously restored
an engineering view is needed to ensure long-term
These teeth are a challenge to restore when
removal of the old restorative material and decay
leaves significant portions of the tooth needing
replacement (Fig. 11). These teeth will require placement of posts to retain the core of the remaining
tooth structure.
Because the purpose of posts is to retain the core,
it is recommended that in multi-canal teeth a post
be placed into each canal to cross-pin the core to
the remaining tooth structure (Fig. 12). Projection of
the posts in posterior teeth due to the angulation of
the canals leads to convergence of the posts in the
coronal portion of the tooth. This locks the core in
survival. Ferrule is often overlooked in today’s age of
adhesive dentistry, but it is as critical today as it was
in the past. Lack of ferrule has been shown to affect
survival of the tooth, and the literature supports use
of 2.0 mm of ferrule, which is more critical in maxillary anterior teeth due to the direction of loading
during mastication.
Additionally, how we restore the remaining tooth
plays a role in potential issues in the long term. Metal
posts are being used less frequently due to vertical root
fractures that can occur when the tooth is overloaded,
and the direction has increasingly moved to the use of
fiber posts, which mimic the roots modulus of elasticity.
When teeth restored with a fiber post are overloaded,
‘Teeth rarely fail when they are
over-engineered, but many fail due to
under-engineering.’
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[12] =>
I C.E. article_ restoration
fracture typically occurs in the coronal (supragingival)
portion, leaving sufficient tooth remaining to re-restore the tooth. Teeth rarely fail when they are overengineered, but many fail due to under-engineering._
_References
1.
Barkhodar RA, Radke R, Abbasi J: Effect of metal collars on
resistance of endodontically treated teeth to root fracture. J
Prosthet Dent 61:676, 1989.
2. Galen WW, Muella K.: Restoration of the Endodontically
Treated Tooth. In Cohen, S. Burns, RC., editors: Pathways
of the Pulp, 10th Edition.
3. Stankiewicz NR, Wilson PR. The ferrule effect: a literature
review. Int Endod J, 35:575–581, 2002.
4. Galen WW, Mueller KI: Restoration of the Endodontically
Treated Tooth. In Cohen, S. Burns, RC, editors: Pathways of
the Pulp, 8th Edition. St. Louis: Mosby, Inc. 2002. page 771.
5. Ichim I, Kuzmanovic DV, Love RM.: A finite element analysis
of ferrule design on restoration resistance and distribution of
stress within a root. Int Endod J. 2006 Jun;39(6):443-452.
6. Nicholls JI. An engineering approach to the rebuilding of
endodontically treated teeth, J Clin Dent, 1:41-44, 1995.
7. Libman WJ, Nicholls JI: Load fatigue of teeth restored
with cast posts and cores and complete crowns. Int J
Prosthodontics 8:155-161, 1995.
8. Freeman MA, Nicholls JI, Kydd WL, Harrington GW:
Leakage associated with load fatigue-induced preliminary
failure of full crowns placed over three different post and
core systems. J Endod 24:26-32, 1998.
9. Ricucci D, Siqueira JF Jr.: Recurrent apical periodontitis and
late endodontic treatment failure related to coronal leakage:
a case report. J Endod. 2011 Aug;37(8):1171-1175. doi:
10.1016/j.joen.2011.05.025.
10. De Moor R1, Hommez G.: [The importance of apical and
coronal leakage in the success or failure of endodontic
treatment]. Rev Belge Med Dent (1984). 2000;55(4):334344.
11. Sritharan A.: Discuss that the coronal seal is more important
than the apical seal for endodontic success. Aust Endod J.
2002 Dec;28(3):112-115.
12. Jimenez MP, et al. Fracture resistance of endodontically
treated teeth with fiber composite posts. IADR abstract no.
323, March, 2002.
13. Bitter K Kielbassa AM: Post-endodontic restorations with
adhesively luted fiber-reinforced composite post systems:
a review. Am J Dent. 2007 Dec;20(6):353-360.
14. Martinez-Insua A, et al. Comparison of the fracture
resistances of pulpless teeth restored with a cast post and
core or fiber post with a composite core. J Prosthet Dent
80(5), 1998.
15. Al-Ansari A.: Which type of post and core system should you
use? Evid Based Dent. 2007;8(2):42.
16. Plotino G, Grande NM, Bedini R, Pameijer CH, Somma F.:
Flexural properties of endodontic posts and human root
dentin. Dent Mater. 2007 Sep;23(9):1129-1135. Epub 2006
Nov 20.
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17. Stewardson DA1, Shortall AC, Marquis PM, Lumley PJ.:
The flexural properties of endodontic post materials.
Dent Mater. 2010 Aug;26(8):730-736. doi: 10.1016/j.
dental.2010.03.017. Epub 2010 Apr 21.
18. Pierrisnard L, Bohin F, Renault P, Barquins M.: Coronoradicular reconstruction of pulpless teeth: a mechanical
study using finite element analysis. J Prosthet Dent. 2002
Oct;88(4):442-448.
19. King PA, Setchell DJ. An in vitro evaluation of a prototype
Carbon fiber reinforced prefabricated post developed for the
restoration of pulpless teeth. J Oral Rehabil 1990;17:599609.
20. Purton DG, Chandler NP. Rigidity and retention of root canal
posts. Br Dent J 1998;184:294-296.
21. Cormier CJ, Burns DR, Moon P. In vitro comparison of the
fracture resistance and failure mode of fiber, ceramic and
conventional post system at various stages of restoration. J
Prosthodont 2001;10:26-36.
22. Martínez-Insua A, da Silva L, Rilo B, Santana U. Comparison
of the fracture strength of pulpless teeth restored with a cast
post and core or carbon fiber post with a composite core. J
Prosthet Dent 1998;80:527-532.
23. Chieruzzi M, Pagano S, Pennacchi M, Lombardo G,
D’Errico P, Kenny JM.: Compressive and flexural behaviour
of fibre reinforced endodontic posts. J Dent. 2012
Nov;40(11):968-978. doi: 10.1016/j.jdent.2012.08.003.
Epub 2012 Aug 21.
24. Padmanabhan P. A comparative evaluation of the fracture
resistance of three different pre-fabricated posts in
endodontically treated teeth: An in vitro study. J conserve
Dent 2010;13:124-128.
25. Maccari PC, Conceição EN, Nunes MF. Fracture resistance
of endodontically treated teeth restored with three
different prefabricated esthetic posts. J Esthet Restor Dent
2003;15;25-31.
_about the author
roots
Dr. Gregori M. Kurtzman is
in private general practice
in Silver Spring, Md., and
is 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 has more than 365 published articles. He has earned
fellowship in the AGD, AAIP, ACD, ICOI, Pierre Fauchard and
ADI, mastership in the AGD and ICOI and diplomat status in
the ICOI and American Dental Implant Association (ADIA).
Kurtzman has been honored to be included in the “Top Leaders in Continuing Education” by Dentistry Today annually
since 2006 and was featured on its June 2012 cover. He
can be reached at dr_kurtzman@maryland-implants.com.
[13] =>
technique_ instrumentation
I
Microendodontics?
Finding the sweet spot between effective
instrumentation and maximal tooth strength
Author_Eric Herbranson, DDS, MS, FDIC
_I don’t like the term “microendodontics.” I like
the term “minimally invasive endodontics” better, but
they both imply an objective that is not the reality of
the changing concepts of what access and shaping
results should ideally look like. It’s not about how small
you can make an access but about designing treatment
protocols that maximize dentin conservation while
balancing the need for meeting treatment objectives.
It’s about dentin conservation and root form appropriate shaping, not the smallest possible accesses.
There is a growing awareness that the legacy
access concepts and principles have resulted in
unnecessary removal of critical dentin that is structurally compromising teeth. Dr. David Clark and
Dr. John Khademi deserve the credit for identifying
and defining the critical importance of percervical
dentin. Pericervical dentin is the dentin from the top
of the pulp chamber to the upper canal area (Fig 2).
This is considered to be the dentin critical for
tooth strength and should be conserved as much
as possible. Strength equates to longer lasting restorations — our ultimate goal. Two features of the
legacy designs are a problem for dentin conservation. The first is the recommendation to completely
de-roof the pulp chamber. The second is developing
“convince form” in the coronal part of the canal by
removing the internal triangle of dentin. Both are
unnecessary and remove dentin that should be
retained for strength.
Defenders of these legacy concepts point to the
five mechanical objectives for shaping presented in
1974 by Dr. Herbert Schilder. Even though he was a giant in endodonitics who dramatically influenced the
specialty, the almost religious defense of his ideas gets
in the way of conceptual progress. His objectives need
a fresh look in the light of our better understanding of
dental anatomy and newer file designs and materials.
found understanding of tooth anatomy. In addition
to the obvious canal complexity shown by these
scans, the presences of concavities were shown to
_Dental anatomy
Fig.1_This case by Dr. Jeff Pafford has all the features of a well-designed conservation approach, including
respect for the natural dimensions of the pulp chamber, an orifice-directed occlusal outline and root-formappropriate canal shaping with adequate deep shape and conservative upper shape. It shows the typical
hourglass profile of this style prep. (Images/Provided by Dr. Eric Herbranson)
Work with high-resolution micro-CT scanners
starting in the 1990s provides us a much more pro-
Fig. 1
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[14] =>
I technique_ instrumentation
Fig. 2
Fig. 3
Fig. 2_Pericervical dentin extends
from the top of the pulp chamber
to the upper third of the canals.
Conservation of this dentin is critical
to maintaining tooth strength and
fracture resistance.
Fig. 3_A significant concavity on the
furcal side of a lower molar mesial
root. These hidden concavities are
ubiquitous and reduce the amount
of effective dentin available to us.
A good understanding of tooth
anatomy is essential to prevent
procedural errors and minimize tooth
fracture.
be ubiquitous, and they reduce the amount of dentin
we have to work with. An example is the lower molar
mesial root. Virtually all of them have significant
concavities in the furcation side of the root that starts
at the furcation (Fig 3).
There is simply much less dentin than most clinicians realize at this point, and over-enlargement
of the canal must be guarded against to maintain
strength and prevent strip perforations.
_Pulp chamber outline
The legacy recommendation for pulp chamber
outline is to un-roof the pulp chamber and, once
identified, flare the opening from the canal orifice to
the occlusal. This excessively large access is justified
by the need for irrigation, visualization and canal access. All can be accomplished through a smaller, more
conservative access design that does not destroy
tooth strength.
_Convenience form — triangle removal
The recommendation to remove the dentin triangle from the upper canal is based on the need for
straight-line access to the coronal part of the canal
system. This feature was dictated by the historical
use of stiff stainless-steel instruments and later by
the excess stiffness of overly large NiTi instruments.
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3_ 2014
Today’s newest generation heat-treated NiTi instruments are much more flexible, have a smaller upper
flute diameter and do not require this feature.
_Instrument design
Multitaper instruments were introduced to solve
some inherent problems of straight taper instruments. They automatically created more deep shape
for better irrigation and steeper apical tapers for
better obturation control. Good ideas — however,
the first-generation multitaper instruments and
their newer derivative all have a design defect, in my
estimation.
‘The greater the
amount of
dentin conserved,
the greater the
increase in
strength.’
[15] =>
[16] =>
I technique_ instrumentation
Fig. 4
Fig. 5
Fig. 4_Both of these files have a
0.25 mm tip diameter and
essentially the same profile in the
apical third, but note the difference
in the diameter at the D16. The
latest generation SS White vTaper
instrument is significantly smaller
and creates a more appropriate root
form shape than the ProTaper F2.
Fig. 5_Legacy access concept
on the left; modern conservative
access concept on the right with
its orifice-directed occlusal outline
form, minimal chamber enlargement
and root form appropriate shaping.
Note the significant difference in the
amount of critical cervical dentin
saved with this approach. More
dentin — more strength and fracture
resistance.
The mean flute diameter (MFD) at the upper end
of these instruments is too large for most teeth. It
is certainly too large for most molar canal systems
and results in unnecessary removal of critical
dentin, especially in teeth with longer roots. The
newest instrument designs have profiles that
better match the actual root anatomy and thus
conserve valuable pericervical dentin — all while
creating shapes that allow us to meet quality treatment objectives.
They have significantly smaller MFD at D16 than
the older designs while creating similar deep shape
for irrigation and obturation (Fig 4). This smaller MFD
combined with newer heat-treating protocols has
created a much more flexible instrument that eliminates the need for the “convenience form” design.
_The new paradigm
Dentin conservation needs to be designed into
our access and shaping. It involves reducing the
excessive widening of the pulp chamber, eliminating
the convenience form and using instruments with a
smaller MFD at the upper end. The occlusal opening
is outlined by projecting the canal center line to the
occlusal surface to avoid impinging the file into an “S”
bend (Fig 5). The result is, each tooth has a different
geometry, depending on its specific needs (Fig 1).
_Does it matter?
Yes, it does. A recent project conducted at the
University of Toronto and published by Dr. Rajesh
Krishan, et al, specifically set out to answer this question. It showed that the greater the amount of dentin
conserved, the greater the increase in strength.
The more-conservative access prepped molars
had strengths that approached the un-accessed
control group and were 2.5 times stronger than the
traditional access design. Coronal fracture is responsible for a significant percentage of endodontic failures and a more conservative approach to access and
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shaping has the potential to lower that percentage. It
is time we integrate these concepts and instruments
into our clinical practice.
Let’s just not call it “microendodontics.” Let’s
call it “conservative endodontics,” with respect for
the anatomy. “Root form appropriate shaping,” if
you will!_
A complete list of references is avaialble on request.
_about the author
roots
Eric Herbranson, DDS, MS,
FICD, is a co-founder and
chairman of the board of
Brown & Herbranson Imaging, a company that develops
dental and human anatomy
education software under the
eHuman moniker. He is also
the developer of the Xmount
series of microscope camera
mounts. With close to 40
years in practice, Herbranson
is a dedicated clinical endodontist. His study of physics and
40 years of experience in film and digital imaging provide
him with an educated understanding of macro and microphotography and affords him a unique vision of endodontic
education and image production. With his innovative approach and advanced imaging skills, Herbranson developed
the unique processes and methodology for capturing images
of human and dental anatomy now used as the basis for
eHuman’s 3DTooth Atlas, TMJ Occlusion Atlas and other
products. Herbranson was the co-author of the chapter on
tooth anatomy in “Pathways of the Pulp,” editions 7 and 8. He
is a frequent speaker and educator at universities and conferences on the subjects of integration of new technology into
dentistry, the use of software and computers in presentations,
surgical microscope photography and endodontic technique.
Herbranson earned a bachelor of science from La Sierra College, a doctoral of dental surgery from Loma Linda University
and a master’s of science in endodontics from Loma Linda
University. He was awarded Distinguished Alumnus from
Loma Linda University in 2007 and Master of Innovation from
the Academy of Microscope Enhanced Dentistry in 2008. He
can be contacted at eherbranson@yahoo.com.
[17] =>
[18] =>
I trends_ laser therapy
PIPS and retreatment
Author_Reid Pullen, DDS, FAGD
_Retreatment can be difficult and time-consuming.
The first order of business is to figure out why the
primary root canal treatment is failing. Sometimes the
answer will be evident after the patient interview, clinical exam and radiographic analysis, but other times the
root canal failure is a mystery. Some of the questions
I recommend thinking about are: Was a rubber dam
used? Is there a root fracture? Is there a missed canal?
Did the practitioner use sodium hypochlorite and use
proper irrigation methods? Is the root canal underfilled
and/or undercondensed?
Is there periodontal involvement? If the supporting periodontum appears healthy and the root
does not appear to be fractured, than typically the
root canal failure is originating from inside the canal
system. With all of these factors in play, it is not surprising that the retreatment success in endodontics
is lower than primary root canal success by 10 to 20
percent. While retreatment success can vary from
70 to 90 percent, non-surgical root canal treatment
success hovers around 90 percent. This article will
review the Photon Induced Photoacoustic Streaming
(PIPS) (Lightwalker Laser from Fotona) literature and
discuss a retreatment case where the PIPS irrigation
technique was instituted in hopes of increasing the
success rate.
Fig. 1_Pre-op #18 (Photos/Provided
by Technology4Medicine)
Fig. 2_Intact gutta-percha cone
removal.
Fig. 3_Intact gutta-percaha cone
removal with Hedstrom file.
Fig. 1
_PIPS introduction
PIPS is a technique that uses Erbium:YAG laser
energy to agitate the irrigation solution inside a root
canal system and cause a strong shockwave effect
that can lyse bacteria cells and remove biofilm. By
placing the tapered PIPS tip into the access and ir-
Fig. 2
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3_ 2014
rigation solution, subablative laser is used to push
a tsunami of irrigation solution into the main root
canal, the lateral, secondary and accessory canals,
isthmuses and the deep complex apical anatomy of
the treated tooth. PIPS creates an irrigant shockwave
of bacterial destruction.
_PIPS and research
An article in 2011 showed that the PIPS technique
was superior in removing bacteria when compared
with standard needle aspiration and passive ultrasonic irrigation when using 6 percent sodium
hypochlorite in an extracted premolar tooth prepped
to a size 20 foramen with an 07 taper.1 Another
article shows 100 percent inhibition of regrowth of
Enterrococcus faecalis after using the PIPS irrigation
technique for 20 seconds with 6 percent sodium
hypochlorite in a single rooted tooth. These teeth
had soaked in an Enterococcus faecalis broth for four
weeks.2 PIPS also effectively removed biofilm from
within the root canal system. In a bovine study model,
PIPS outperformed standard needle irrigation, the
EndoActivator and passive ultrasonic irrigation in
removing biofilm from infected bovine dentin.3 In an
article published this year, PIPS was shown to remove
debris and increase canal space 2.6 times more than
standard needle irrigation in the isthmuses of lower
molars.4
_PIPS and retreatment
A 62-year-old female patient presents with a
chronic, persisting pain in the mandibular left second
Fig. 3
[19] =>
trends_ laser therapy
molar (#18) with a duration of two weeks. The tooth
had been endodontically treated approximately two
years prior. The patient was unable to bite on #18
without significant discomfort.
Clinical testing revealed that #18 was percussion- and bite-stick-sensitive, while #19 and #20
tested normal to all tests. Radiographic analysis revealed that #18 had an adequate root canal without
a periapical lesion (Fig. 1). Because of the positive
clinical tests, it was determined that #18 needed a
non-surgical root canal retreatment.
The patient was anesthetized and a rubber dam
was placed. The composite core access was removed
with a 701 carbide and 557 surgical length carbide
bur. Upon inspection of the gutta-percha it appeared an uncontaminated “healthy” pink and did
not contain any odor. It did not look or smell like the
majority of retreatments where the gutta-percha
appeared to be a mixture of black and pink color with
a nefarious odor.
Before using chloroform, the ProTaper Retreatment #2 and #3 rotary files (DENTSPLY Tulsa) were
used at 500 rpm to carefully remove the majority of
the coronal and middle gutta-percha. In two of the
three canals the #2 or the #3 retreatment rotary file
removed the entire cone from the canal, making it an
extremely efficient retreatment and allowing extra
treatment time for 6 percent NaOCL to soak inside
the canal system.
The technique was as follows: Carefully drill
into the gutta-percha with the retreatment rotary
file and after a 5- to 10-mm bite stop rotation. Let
it cool for a few seconds and then with one hand
pull up on the rotary handpiece head while the
other hand is protecting the maxillary teeth from
any blunt trauma in case the handpiece head pulls
out of the canal with high velocity. In some cases
if a single cone has been used and/or if the sealer
did not set or was inadequately placed, the entire
cone will come out in one piece.
In this case, two of the three cones were
extracted fully intact while using the rotary
technique mentioned above. The third cone was
removed intact with a #35 Hedstrom file (Figs. 2,
3). The canals were then “PIPSed” for 30 seconds
with 6 percent NaOCL as the irrigation solution
and then patency and working length were established using hand files and an electronic apex
locator (EAL). The canals were then reshaped
with a reciprocating WaveOne Primary file
(DENTSPLY Tulsa) and a final PIPS protocol was
followed using 6 percent NaOCL, distilled water,
17 percent EDTA and then distilled water (Fig. 4).
Because it appeared that a single cone technique was used and that the resin sealer did not
fully set, or was not adequately placed into the
canal, the case was completed in one visit. The
Fig. 4
I
Fig. 5
canals were obturated with bioceramic guttapercha coated cones and bioceramic sealer
(Brasseler USA). A modified warm vertical condensation technique was used to help condense
and pack the gutta-percha and sealer. The canals
were backfilled with warm gutta-percha (Fig. 5).
Fig. 4_PIPS in action.
Fig. 5_Post-op #18.
_Conclusion
PIPS is a ER:YAG laser-enhanced irrigation technique where laser energy is used to strongly agitate
canal irrigant. Studies have shown that it is more
effective in killing bacteria, removing biofilm, removing canal debris and increasing canal space
than standard needle irrigation, sonic irrigation and
passive ultrasonic irrigation.
In my experience of “PIPSing” over 2,000 cases,
I see an increase in the obturation of lateral canals
and deep complex apical anatomy. PIPS also aids in
removing pulp stones, retreatment canal debris and
separated files that have been loosened by ultrasonics. Photon induced photoacoustic streaming gives
clinicians confidence that they are doing everything
in their power to clean the entire root canal system._
A list of references is available from the publisher.
_about the author
roots
Reid Pullen, DDS, FAGD,
graduated from USC dental
school in 1999 and served
three years in the U.S. Army
as a dentist in Landstuhl,
Germany. While in the Army,
he completed a one-year advanced education in general
dentistry residency. After the
military, Pullen practiced as a
general dentist for two years
in southern California, prior
to attending the endodontic residency at the Long Beach
Veterans Hospital in 2004. He graduated from the endodontic
residency in 2006 and has maintained a private practice limited to endodontics in Brea, Calif., since 2007. Pullen obtained
his endodontic board certification in 2012.
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[20] =>
I industry education_ LVI
LVI Core I three-day course
is designed for doctors and
their teams to learn together
Author_Mark Duncan, DDS, FAGD, LVIF, DICOI, FICCMO, Clinical Director, LVI
Las Vegas Institute for Advanced
Dental Studies offers Core I, a threeday course for doctors and their
teams. (Photo/Provided by Las Vegas
Institute for Advanced Dental Studies)
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_As a patient, I expect the best care I can find. As
a doctor, I want to deliver the best care possible. That
takes us to the power of continuing education, and as
doctors we are faced with many choices in continuing education.
As a way to introduce you to the Las Vegas Institute for Advanced Dental Studies, or LVI, I want
to outline what LVI is about and what void it fills
in your practice. The alumni who have completed
programs at LVI were given an independent survey,
and unlike the typical surveys, 99.7 percent said they
love practicing dentistry, and of those surveyed, 92
percent said they enjoy their profession more since
they started their training at LVI. That alone is reason
enough to go to LVI and find out more.
While the programs at LVI cover the full breadth
of dentistry, the most powerful and life-changing
program is generally reported as being Core I, or
“Advanced Functional Dentistry — The Power of
Physiologic-Based Occlusion.” This program is a
three-day course that is designed for doctors and
their teams to learn together about the power of
getting their patients’ physiology on their side. In
this program, doctors can learn how to start the
process of taking control of their practice and start
to enjoy the full benefits of owning their practice
and providing high-quality dentistry.
Whether he or she works in a solo practice or in a
group setting, every doctor can start the process of
creating comprehensive care experiences for his or
her patients.
We will discuss why some cases that doctors are
asked by their patients to do are actually dangerous
cases to restore cosmetically. We will discover the
developmental science behind how unattractive
smiles evolve and what cases may need the help of
auxiliary health care professionals to get the patient
feeling better. The impact of musculoskeletal signs
and symptoms will be explored and how the supporting soft tissue is the most important diagnostic
tool you have. Not simply the gingiva, but the entire
soft-tissue support of the structures not just in the
mouth but also in the rest of the body.
A successful restorative practice should not be
built on insurance reimbursement schedules. An
independent business should stand not on the whims
and distractions of a fee schedule but rather on the
ideal benefits of comprehensive care balanced by the
patients’ needs and desires.
Dentistry is a challenging and thankless business, but it doesn’t have to be. Through complete
and comprehensive diagnosis, there is an amazing
world of thank-yous and hugs and tears that our
patients bring to us, but only when we can change
their lives. The Core I program at LVI is the first step
on that journey.
That’s why when you call, we will answer the
phone, “LVI, where lives are changing daily!”_
[21] =>
[22] =>
I industry_ Seiler
Seiler microscopes
Geared to meet the technological
demands of specialists
Author_Seiler Staff
The Dental XR6. (Photo/Provided by
Seiler)
_Seiler’s Microscope Division offers an array of
products geared to meet the technological demands
of the dental, surgical and medical markets. As a
worldwide leader in the field of microscopy, Seiler
prides itself on the use of high-quality optics and
precision machining to provide the market with the
latest in magnification for a varied range of applications.
All Seiler microscopes come equipped with
apochromatic lenses for what the company says is
superior clarity, the brightest light source on the market and a smooth, fluid movement for the ultimate
in mobility. Seiler continues to stay at the forefront
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of fine optics and stands behind its products with a
lifetime warranty on the optics and mechanics.
By tailoring the product lines to meet specific applications in the health-care industry, Seiler Instrument has built a vast distribution network covering
the entire United States as well as the rest of the
world. Growing year by year, the Microscope Division
continues to seek new markets, diversify the product
line and improve service to the many disciplines in
science and medicine.
To experience what the company calls the
“Seiler Advantage,” call (800) 489-2282 or visit
www.seilermicro.com to learn more._
[23] =>
[24] =>
I industry_ Zendo Direct AG
What is the first thing
that comes to mind?
Author_Dr. Barry H. Korzen
(Images/Provided by Zendo Direct AG)
_We are living in the “Information Age,” where
Professor Google is more accessible than many, if not
all, of the teachers we had in dental school. However,
we have been programmed to think “inside the box”
— not the way our children and grandchildren will be
— and therefore more often than not we tend to focus
on the first thing that comes to our mind, especially
when there is a subliminal thought that we either
follow to see where it leads us or, not being familiar
with the name or phrase, we just shut the door on it
and move back into our comfort zone.
Here are a few well-known places with what Professor Google feels most people associate with that
location. You may have different associations with
these places, especially if you have personally visited
any or all of them, but what is important is that you
really can’t argue with the connection that certain
places have with the first thought that goes through
our mind when we hear that name.
Canada — Mounties
Paris — Eiffel Tower
Rome — Coliseum
Egypt — Pyramids
New York — Broadway
Switzerland — precision and quality
When an endodontist such as myself sets out
to create a company dedicated to bringing to the
profession quality and European precision with each
product that we deliver, there was only one place to
headquarter that company — Switzerland.
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But having the best products must also mean
having an added attraction to start practitioners
thinking about moving outside their “comfort
zone,” outside “the box” — and in these economic
times the greatest motivator is value. So by
selling direct to you, over the Internet, we have
been able to bring the price for European-quality
products down to a level where you don’t need to
be a volume buyer to get a volume discount. For
example, nickel titanium files are value priced at
$5.99 per file.
You should still associate Canada with the
Mounties and Paris with the Eiffel Tower. But
when thinking quality endodontic products at the
right price, leave those other brand names inside
the box; step outside to Zendo Direct, where you
will get substantial savings at www.ZendoDirect.
com every time._
_about the author
roots
A graduate of the University of Toronto Faculty of
Dentistry and the Harvard
University graduate endodontic program, Dr. Barry
H. Korzen is the founder of
The Endo Academy (www.
TheEndoAcademy.com)
and Zendo Direct (www.
ZendoDirect.com). He was
an associate professor, assistant dean and former
head of the Discipline of Endodontics at the University
of Toronto Faculty of Dentistry. Besides authoring numerous papers, Korzen has spoken to dental societies
and organizations around the world and has delivered
lectures at more than 20 universities. He has received
fellowships from the American College of Stomatologic
Surgeons, the International College of Dentists and the
Pierre Fauchard Academy. Korzen is a past president of
both the Canadian Academy of Endodontics and the Ontario Society of Endodontists and has been a longstanding member of the American Association of Endodontists
and the Alpha Omega International Dental Fraternity.
[25] =>
[26] =>
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26 I roots
3_ 2014
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