Veritas; In the realm of the philosopher kings

Please bear with me re; this particular blog entry. It is an experimental model for future design parameters of both clinical and op-ed pieces on the winds of change in dentistry. As well, it is hoped that it can in time, be used to denote transitional change as product, technique and philosophy iterate temporally as our knowledge base expands.

Philosopher kings are the rulers, or Guardians,
Plato‘s Utopian Kallipolis. If
his ideal 
city-state is to ever come into being,
“philosophers [must] become kings…or those now called kings [must]…genuinely and adequately
philosophize” (
The Republic, 5.473d).*


Predictable clinical success in endodontics
is a multifactorial biologic and technologic wave equation wherein each
procedural component is woven into the framework and fabric of the final
result. Debridement, disinfection and root filling have been given an abundance
of marketing terminology. Unfortunately, insurance codes have reduced an
anastomotic arboretum of rivulets and tributaries into a codified linear array.
In this author’s opinion, bureaucratic categorization has diminished the wonder
of the science of endodontics immeasurably. Worst of all, evidence based
science has not resulted in a more mature approach to preservation of natural
teeth using decades of evolutionary advances in material and technique.  Rather,a “simpler is better”
mentality has been fostered which may prove catastrophic in this implant driven
treatment planning era. Endodontics must reassert the pre-eminence of the
diagnostician rather than the technician. The discipline must look to a new
generation of philosopher kings,not self-styled gurus and experts with suspect
agendas, to sustain its relevancy and transcendence.

This conundrum can be answered by revisiting
the fundamentals and rudiments of the therapeutic protocols for
endodontics.  Their validation in the
context of the organic, biologic and pathologic vectors that constitute the
raison d’etre of endodontic therapy will ensure that science drives the
technologic engine with an evidence-based governor.  This article will reference equipment and
product that afford sophistication of the procedural components of non-surgical
endodontic therapy based on critical assessment.  It will speak of addendums to the
armamentarium responsible for enhanced technologic competency and accentuation
of the biologic mandates that engender functional success by distilling the
multivariate requirements into a logical and substantiated thought and
therapeutic process.


There is no magic
to access preparation; it is archaeologic. The clinician uncovers the pathologic
and temporally altered morpho-metrics of the chamber and the root canal space using
the spatial diagnostic data on hand; ideally a combination of 2 and 3
dimensional radiography where indicated. Archaeologists refer to this as
stratigraphic excavation or stratification whereby the context of the removal
is related to the dystrophic impact of decay, trauma, mastication, restoration
et al on the pathways of the pulp and the concomitant volumetric reduction. The
road map to orifices lies in our ability to think and act in three dimensions
of both space and time regression.

The conceptual flaw in endodontic therapy
is that the root canal space is treated independent of the
morphologic/functional rehabilitative phase of therapy rather than seamlessly
integrating the bio- and morpho-physiology of the continuum. This discounts two
crucial factors; the impact force generated by an arthrodial joint (TMJ) and
the variability and direction of force vectors throughout the dentition
resulting from the occlusal scheme, be it intact, equilibrated, debilitated or
prosthetically restructured and by what means (RPDs, crowns, bridges and/or
implants – all of which have different torque values).

The fallacy of the endodontic monobloc has
been exposed. Resin sealers do not reinforce the root canal system, nor do the
bonded posts and composite cores create inter and intra-radicular/coronal
reinforcement.  The sine qua non of
restorative stability, predictability and longevity is a ferrule. It is
imperative to the understanding of the role of access in ferrule creation that
the clinician create a 3D ferrule through sustaining vertical and horizontal
bulk by ensuring that the access creation protects the peri-cervical dentin and
enamel where possible.

The era of NiTi instrumentation encouraged
“pre-enlargement” of the cervico-coronal aspect of the RCS (roots canal space) as
the modus operandi to minimize taper lock and breakage of the rotary files. The
use of Gates Glidden drills and “access bur kits (that included troublesome
Peezo style drills)” became pandemic in spite of significance evidence of the
iatrogenic potential they engendered. The self-centering capability of the “bud”
has a place in access, but only if the drill is used at the level of the
orifice, not for penetration beyond the rim. Their use should be curtailed
dramatically as their abuse causes removal of excessive amounts of cervical
dentin and the potential for weakening or strip perforation in furcal areas.

There is an endless profusion of access bur
kits, however, the armamentarium incorporated traditionally designed
restorative burs.  With the advent of
improved illumination, enhanced magnification, super-elastic metallurgy, and
negative pressure irrigation devices, there was a need for transactional
reconfiguration of the access opening to optimize these iterations and minimize
coronal tooth removal. The use of ultrasonics was one innovation; the use of
burs designed specifically for endodontic access another.

Additionally, there was a device available
that while specific to restorative procedures, needed to be rethought in the
context of “archaeology” and used extensively in endodontic access preparation.

The Danville micro-etcher, a staple in
operative dentistry, is claimed to enhance bonding strength up to 400% for
adhesion-based procedures. It is this facility to clear the pulpal floor and
satinize the surface that makes its use an imperative in endodontics. The
fissures, grooves, residual pieces of stones and outlines of even almost
obliterated calcified orifices are exposed and visually enhanced in contrast to
the adjunct matte surface. The use of ultrasonics to “jackhammer”
pulp stones is simply too risky as one approaches the floor of the chamber,
particularly if there are no water ports on the tips. However, clearing the
debris, like an archaeologist uses a brush to expose the topography of the
find, obviates much of that risk.

The detection of the MB2 canal in maxillary
molars and the existence of middle mesial canals in mandibular molars have
reached mythical status.  With respect to
the microscope moguls, their existence was demonstrated by the work of Hess
almost a century ago. Was it the lack of enhanced vision or lack of acceptance
of their existence or the perception of pervasive confluence that engendered
the failure to identify them?  As pointed
out by Buhrley et al. among others, in some instances, the most important
factor in locating the MB2 canal or any unusual canal configuration is not
magnification, but the persistence of the operator. With the advent of small
FOV cbCT and the ability to axially and coronally slice the “images”, we have
gone back to the future.

and disinfection; Historical context

The defining seminal principle of rotary
instrumentation, the envelope of motion, as described by Dr. Schilder
facilitates enhanced diametral shaping mid-root enabling deeper penetration of
irrigants. The prepared canal shape is influenced by the motion of the
instrument in the canal, not the type of instrument used. The traditional
push-pull or circumferential filing motion posed problems with ledging in
curved canals, elliptical reshaping of the apex and strip perforation in furcal
regions; the envelope of motion obviated these iatrogenic effects. Apical
control during obturation was achieved by retaining the terminus diameter as
small “as reasonably possible”, rather than creating artificial stop

Roane’s “Balanced Force” method
has gained acceptance since its introduction in 1981. Again, instruments are
used in a rotary rather than push-pull motion. When file engages, with apical
pressure, 1/4 turn then again, with apical pressure, 3/4 turn counterclockwise.
The sequence is repeated two or three time; the last time, a 360-degree turn
clockwise (no apical pressure) will load the file with all the dentinal debris
collected. On removal, dentin will be evident on the most apical portion of the
file.  Mechanized reciprocation is based
on this concept; there are both stainless steel and NiTi systems available
based upon the method. /

The new era of
endodontic instrumentation was green-lighted once it was understood that the
file bound in the coronal half not the apical third of the canal space and the
crown down approach began to replace the historic crown-down technique.
By removing the cervical constriction,
the coronal dentin is passively removed with larger files or reamers; in turn,
a smaller file proceeds unhindered into the apical third of the canal,
resulting in increased tactile awareness in the apical third of the canal.
Hence, a file that does not bind in the coronal half, only in the apical
one-third, possesses exquisite proprioceptive properties

The most recent
inclusion to the endodontic armamentarium incorporates all these features,
however, it moves beyond the procedural accidents incorporates irrigation and
is capable of addressing the morpho-metrics of the root canal space in a way
that no previous file system, stainless steel or nickel-titanium can.
The SAF instrument
is attached to a specially designed handpiece that oscillates the instrument
up-and-down within the canal 5,000 times per minute with an amplitude of .40mm;
it is this movement that cleans and shapes the canal as it “sandpapers” the
walls of the canal. There is no rotational movement used to shape the canal.
Because of the metal memory inherent with the nickel titanium lattice of the
instrument, the SAF instrument has the natural ability to radially expand
within the canal, adapting to the shape of the original canal morphology. The
canal space and inner dentin are subsequently cleaned and shaped conservatively
in three dimensions, thus preserving the natural cross-sectional shape of the

A single ?le is
used throughout the procedure. It is inserted into a path initially prepared by
a # 20 K-?le and operated with a transline- (in-and-out) vibration. The
resulting circumferential pressure allows the ?le’s abrasive surface to gradually
remove a thin uniform hard-tissue layer from the entire root canal surface,
resulting in a canal with a similar cross-section but of larger dimensions.
This holds also for canals with an oval or ?at cross-section, which will be
enlarged to a ?at or oval cross-section of larger dimensions. The straightening
of curved canals is also reduced because of the high pliability of the ?le and
the absence of a rigid metal core. Thus, the original shape of the root canal
is respected both longitudinally and in cross-section. The hollow SAF ?le is
operated with a constant ?ow of irrigant that enters the full length of the
canal and that is activated by the vibration and is replaced continuously
throughout the procedure. This results in effective cleaning even at the cul de
sac apical part of the canal. The SAF has high mechanical endurance; ?le
separation does not occur; and mechanical failure, if it occurs, is limited to
small tears in the latticework.

considerations – Bioburden

The bioburden that
remains subsequent to debridement, disinfection and sculpting the contours of
the root canal space is the determining variant in endodontic success. Computational
fluid dynamics (CFD) is a new approach in endodontic research to improve our
understanding of the special anatomic environment of the root canal. Fluid flow
is commonly studied in 1 of 3 ways: experimental fluid dynamics; theoretic
fluid dynamics and computational fluid dynamics. CFD is the science that
focuses on predicting fluid flow and related phenomena by solving the
mathematical equations that govern these processes. Numerical and experimental
approaches play complementary roles in the investigation of fluid flow. The
focus of endodontic irrigation studies will also shift with the awareness that presence
of an apical vapor lock effect adversely affects debridement ef?cacy and only
evaluation of open apical systems will truly reflect irrigation effectiveness.

This should come as no surprise to the
majority of endodontists as apical patency is a prime treatment objective. Apical
patency is intended exclusively to prevent that dentin chips are compacted into
the apical region forming a plug that can interfere with the working length. In
canals with necrotic pulp tissues, apical patency is ensured with instruments
that do not bind to the foramen to prevent the displacement of necrotic
material from the canal into the periapical space. In canals with vital pulps
apical patency should always be established with extremely thin instruments to
minimize the trauma induced to the apical tissues.

Of all the various devices and systems currently
in the marketplace, the one with the greatest number of pure science papers is
the EndoVac.  With the EndoVac, irrigant
is pulled into the canal and removed by negative pressure at working length. Patency
is key to this device as the irrigant due to the negative pressure dynamics can
be delivered to working length with no risk of procedural misadventure. This is
unprecedented in terms of what is available in the market.

Replication / Obturation

Treatment Outcome in Endodontics; The Toronto Study demonstrated that the
classic Schilder technique of vertical compaction of warm gutta-percha was a
positive predictor of treatment success in contrast to lateral condensation.…from-Bojidar-Kafelov/347.html

There are a wealth of devices, corded and cordless that have iterated this
technique, and yet, carrier based obturation is the preeminent global
obturation modality in terms of sales. Numerous investigations have compared it
to lateral condensation and demonstrated superior root filling based on two
dimensional radiographic assessment and in-vitro dye studies, both of which
have no real scientific validity.  Others
noted that in most preparations, the carrier abutted the canal wall in the
cervical and middle sections but was usually surrounded by gutta-percha in the apical
one third.  The adaptation of components
showed the most variability at the most apical extent of the preparation;
complete encasement of the carrier did not occur in any specimen particularly
in canals with significant apical curvature. 
Sealer distribution was variable throughout, usually being absent in the
apical section of the canal space. The latest iteration of carrier based
obturation carries the imprimatur of a number of well known endodontic product
developers and educators –

same “clinicians” were the developers and advocates of thermoplastic injection
molded devices that iterated the seminal ‘Obtura’ delivery system. The
marketing concept of mated systems is business 101, lacks in unaffiliated science
and the claimed evolution of perspective and mindset change can readlily be
viewed as disingenuous. Confronted with the following perjorative

  • ·       They fail more
    often than conventional filling techniques
  • ·      
    The carrier will be wiped of gutta percha and sealer so the
    carrier will get to the end of devoid of gutta percha
  • ·      
    They are difficult or impossible to control  
  • ·      
    Carrier-based filling is not as accurate as conefit
  • ·      
    They are difficult or impossible to remove when retreatment
    is needed

………the ‘evidence based advocacy commentary’

“If you are an
endodontist and you just do not want to use this filling method, that’s fine –
the rest of us will be drinking coffee while you are still working away – but
remember what Thumper’s mother said: ‘If you don’t have anything good to say,
don’t say anything at all’. If you badmouth it, and a general dentist learns
how to use it successfully, you will look like an insecure, disingenuous
clinician – not a go-to specialist. Even worse, if you badmouth a general
dentist when their carrier-filled case fails, the next time he or she is in
that situation the patient will be sent to an implant surgeon who will say that
endodontic treatment is a space maintainer for an implant – thus giving the general
dentist a ‘get-out-ofjail-card’ for free.On the positive side of this issue,
can you imagine what it would be like in difficult cases to finish the case in
one visit because you used the less time-consuming carrier method? Can you
imagine what it would be like to never see another backfilling void? Can you
imagine how effectively a carrier -moving to within 1mm of the terminus – can
plastically deform gutta percha and sealer in the apical third of a really
narrow, really long and really curved canal? Rather than calling it by its
pejorative description, ‘gutta percha on a stick’, clinicians who are
open-minded are finding carrier-based obturation to be a simple, yet
exceptional method of obturation.”

Similarly, another well-known lecturer and
author in the endodontic field responded to a commentary by Dr. Gord
Christensen as follows;

With all due
respect to Dr. Christensen, I disagree with his claim that Thermafil provides a
“better service.” Based on the number of specialists who use the material, I
believe they would disagree with him as well. If it were a “better service,”
the vast majority of endodontists – myself included – would be using it. In my
opinion, it is expensive relative to the alternatives, is consistent with
extrusion from a patent foramen, can be challenging to remove, and cannot be
bonded into canals as Resilon (Pentron, Wallingford, Conn.) and RealSeal
(SybronEndo, Orange, Calif.). With current options available, I believe
carrier-based methods are not – despite their validity – the best choice for
endodontic obturation. For the reasons given, I think Thermafil most likely has
made few inroads into specialty practice.

In my years as a
specialist, I have had to re-treat this product too often to want to use it
clinically. My greatest reservation has been the necessity to leave a carrier.
In more than a few cases, I have observed an under-prepared canal with a
carrier that is tightly wedged and occupies almost the entire canal (especially

Despite the
recommended methods of removal, when this happens, it becomes necessary to
literally grind into the plastic of the carrier to create a pathway alongside
it. In my view, this is not a valid exchange in placing carriers to length
considering the time needed to remove them if a difficulty arises. I think that
many of the clinicians who place Thermafil might never have attempted removal.
This might account for the differences in clinical viewpoint between the
general dentist and the specialist on this subject. SystemB obturation of a master
cone and the aforementioned bonded obturation with a unit like the Elements
obturation unit (SybronEndo), can go a long way toward avoiding the issues that
arise from warm carrier-based products.

…..Only to write a few short years later on
the release of a carrier based obturation system using a material without
long-term evidence based science……

As mentioned above,
in vitro and in vivo, there is abundant evidence in the endodontic literature
that bonding the obturation with RealSeal provides a better seal and resistance
to coronal leakage relative to gutta-percha across the totality of the canal
space. Having used bonded obturation exclusively since January 2004, I would
never go back to using gutta-percha. In addition, one of the cool features of
bonded obturation is that the clinician has the choice of using RealSeal master
cones and/or RealSeal One Bonded Obturators, ie, a carrier-based form of bonded
obturation product that can be easily adopted by clinicians who are now using
warm carrier-based gutta-percha systems.

It should be noted as per the preceeding
commentary, that sealers based on restorative fundamentals were to be the sine
qua non of monoblock creation in the root canal space. Unfortunately, one of
the most exhaustive studies done to evaluate evidence-based support on the
merits of their clinical use concluded that “on the basis of the in vitro
and in vivo data available to date, there appears to be no clear benefit with
the use of methacrylate resin-based sealers in conjunction with adhesive root
filling materials at this point in their development”

FOV Cone Beam Tomography

Cone beam computed tomography (cbCT) technology
aids in diagnosis of endodontic pathosis and canal morphology, the assessment
of root and alveolar fractures, analysis of resorptive lesions, identification
of pathosis of non-endodontic origin, and pre-surgical assessment prior to root-end
surgery. When compared with medical CT, cbCT has increased accuracy, higher
resolution, reduced scan time, a reduction in radiation dose, and reduced cost
for the patient. As compared with conventional periapical radiography, cbCT
eliminates superimposition of surrounding structures, providing additional clinically
relevant information. Clinicians need to adopt 3-D imaging into their
diagnostic repertoire because accurate diagnostic information leads to better
clinical outcomes.  While cbCT is
invaluable tool in the modern endodontic practice, it is imperative that the
clinician truly understand the mechanism by which images are created. Endodontically
involved cases are more likely to be edgy and contrasty…the exact kind of
imagery that is prone to artifact. 
Explicit mental discipline must be employed to subtract out physics
based, math based and cognition based artifact. 
The reader is directed to the following URL

https// to download files listed as Carr_Part1.flv,
Carr_Part2.flv and Khademi_Video.flv. The material presented therein is among
the most cogent and well thought out assessment of the value of small FOV cbCT
to the endodontic discipline.

After reading this publication, I urge the
reader to review the commentary on the link above. It is a reflection of the
reality of our times.  Experiential
empiricism associated with increments of knowledge and training are driving a
discipline that is becoming increasingly complicated to deliver and
increasingly expensive to receive. A Google search for “the future of
endodontics” is not surprisingly replete with commentary on a “bright future”
from advocates providing the operator use products they are paid to promote
rather than educators who see reframing the endodontic discipline into a true
partner of the critical thinking process in treatment planning.

Far too often, the other partners to that
process, periodontists & oral maxillofacial surgeons, are convinced that
endodontic retreatment creates a more difficult milieu in which to deliver an
implant and invariably recommend extractions for teeth that have experienced
endodontic failure rather than consider retreatment. The corollary to this
observation is to wonder why a highly predictable clinical procedure is not
succeeding.  Treatment outcome success
rates comparing endodontics to implants are at best specious. The cohorts in
both are radically different in their selection criteria and their size.

What is lacking is not the weekend course,
or the mastership course, or the pseuo-residency, but the need to work and
train and share our collective and collaborative knowledge in whatever platform
and framework, ideally online through the aegis of such platforms as Oral
Health.  The interactive potential of
colleagues from academic centres will provide less prejudiced advocacy and
greater interpretive assessment that those supported purely by industry.

Mark Twain wrote ‘We are discreet sheep; we wait to see how
the drove is going, and then go with the drove. We have two opinions: one
private, which we are afraid to express; and another one – the one we use –
which we force ourselves to wear to please Mrs. Grundy, until habit makes us
comfortable in it, and the custom of defending it presently makes us love it,
adore it, and forget how pitifully we came by it. Look at it in politics.’ I
fear that the day has arrived, when the addendum is “Look at it in dentistry”.

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