Endo Tribune Asia Pacific No. 2, 2015
Irrigation dynamics in root canal therapy / Use of mineral trioxide aggregate in endodontic retro-filling / The One Shape Procedure Pack
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Untitled
ENDO TRIBUNE
The World’s Endodontic Newspaper · Asia Pacific Edition
www.dental-tribune.asia
Published in Hong Kong
Vol. 13, No. 12
Irrigation dynamics in root canal therapy
By Prof. Anil Kishen, Canada
Irrigation dynamics deals with the
pattern of irrigant flow, penetration,
exchange and the forces produced
within the root canal space. Current
modes of endodontic irrigation include the traditional syringe needle
irrigation or physical methods, such
as apical negative-pressure irrigation or sonic/ultrasonically assisted
irrigation. Since the nature of irrigation influences the flow of irrigant
up to the working length (WL) and
interaction of irrigant with the canal
wall, it is mandatory to understand
the irrigation dynamics associated
with various irrigation techniques.
Endodontic irrigants are liquid
antimicrobials used to disinfect
microbial biofilms within the root
canal. The process of delivery of endodontic irrigants within the root
canal is called irrigation. The overall
objectives of root canal irrigation
are to inactivate bacterial biofilms,
inactivate endotoxins, and dissolve
tissue remnants and the smear
layer (chemical effects) in the root
canals, as well as to allow the flow of
irrigant entirely through the root
canal system, in order to detach the
biofilm structures and loosen and
flush out the debris from the root
canals (physical effects). While the
chemical effectiveness will be influenced by the concentration of
the antimicrobial and the duration
of action, the physical effectiveness
will depend upon the ability of
irrigation to generate optimum
streaming forces within the entire
root canal system.
The final efficiency of endodontic disinfection will depend upon
both chemical and physical effectiveness.1–3 It is important to realise
that even the most powerful irrigant will be of no use if it cannot penetrate the apical portion of the root
canal, interact with the root canal
wall and exchange frequently
within the root canal system.1
as closed-ended and open-ended
needles. In the case of open-ended
needles (flat, bevelled, notched),
the irrigant stream is very intense
and extends apically along the
root canal. Depending upon the
root canal geometry and the depth
of needle insertion, reverse flow of
irrigant occurs near the canal wall
towards the canal orifice.
1a
1b
1c
1d
Figs. 1a–d: Velocity magnitude of irrigation showing the extent of dead zone. With the open-ended needle tip (a), the velocity
progressively decreased 1.5 mm apical from the tip. With the side-vented needle tip (b), there was a much lower velocity than with
the open-ended tip, and it extended only 0.5 mm. With the apical negative-pressure irrigation (c), there was a constant velocity
slightly higher than the side-vented needle irrigation that was constant as the irrigant moved coronally. The ultrasonically
assisted irrigation (d) showed the highest magnitude of velocity, constant to at least 3 mm coronal to the tip placement.35
where it is evacuated. A detailed
understanding of the irrigation
dynamics associated with syringebased irrigation would aid in improving its effectiveness in clinical
practice.
Irrigant flow during
syringe irrigation
The flow of irrigants is influenced by its physical characteristics, such as density and viscosity.5
These properties for the commonly used endodontic irrigants
are very similar to those of distilled
water.6, 7 The surface tension of endodontic irrigants and its decrease
by surfactants have also been studied extensively. The rationale of
this combination is that it may
significantly affect (a) the irrigant
penetration into dentinal tubules
and accessory root canals8, 9 and
(b) the dissolution of pulp tissue.10
However, it is important to note
that surface tension would only influence the interface between two
immiscible fluids, and not between
the irrigant and dentinal fluid.5, 11
Experiments have confirmed that
surfactants do not enhance the
ability of sodium hypochlorite to
dissolve pulp tissue12, 13 or the ability of chelating agents to remove
the smear layer.14, 15
The type of needle used has a significant effect on the flow pattern
formed within the root canal, while
parameters such as depth of needle
insertion and size or taper of the
prepared root canal have only a limited influence.16–19 Generally, the
available needles can be classified
In the case of closed-ended needles (side-vented), the stream of irrigant is formed near the apical side
of the outlet and is directed apically. The irrigant tends to follow
a curved route around the needle
tip, towards the coronal orifice. The
flow of irrigant apical to the exit of
the needle is generally observed
to be a passive fluid flowing zone
(dead zone), while the flow of irrigant in the remaining aspect of the
root canal is observed to be an active fluid flowing zone (active zone;
Figs. 1a–d & 2a–d). A series of vortices of flowing irrigant are generated apical to the tip. The velocity
of irrigant inside each vortex decreases towards the apex.
Large needles when used within
the root canal hardly penetrate beyond the coronal half of the root
canal. Currently, smaller-diameter
needles (28- or 30-gauge) have been
recommended for root canal irrigation.20, 21 This is mainly because of
their ability to advance further up
to the WL. This facilitates better irrigant exchange and debridement.22–24
In addition, the use of a larger needle would result in decreased space
being available for the reverse
flow of irrigant between the needle
and the canal wall. This scenario
has been associated with (a) an
increased apical pressure for openended needles and (b) decreased
irrigant refreshment apical to the
tip for closed-ended needles.17, 19
The influence of tooth location
(mandibular, maxillary) on irrigant flow has been observed to be
minor.16, 25
Irrigant refreshment
Syringe irrigation
Irrigation methods are categorised as positive-pressure or
negative-pressure, according to
the mode of delivery employed.4
In positive-pressure techniques,
the pressure difference necessary
for irrigant flow is created between
a pressurised container (e.g. a syringe) and the root canal. In negative-pressure techniques, the irrigant is delivered passively near the
canal orifice and a suction tip (negative-pressure) placed deep inside
the root canal creates a pressure
difference. The irrigant then flows
from the orifice towards the apex,
2a
2b
2c
2d
Figs. 2a–d: Time-averaged distribution of shear stress on the root canal wall showing a more uniform distribution on the canal
wall with the open-ended needle tip (a). The side-vented needle tip (b) showed a localised region with a high amount of shear
stress, while there was not an observable level with the EndoVac irrigation (Kerr; c). The ultrasonically assisted irrigation (d)
displayed the highest levels of shear stress over the greatest area of the canal wall.35
Irrigant exchange in the root
canal system is a key prerequisite
for achieving optimum chemical
effect, because the chemical efficacy of the irrigants are known to
be rapidly inactivated by dentine,
tissue remnants or microbes.24, 26, 27
Investigations have explained the
limitations in the irrigant refreshment apical to needles.21, 28–30 Enlarging the root canal to place the
needle to a few millimetres from
the WL and ensuring adequate
space around the needle for reverse
flow of the irrigant towards the
canal orifice allow effective irrigant
refreshment coronal to the needle
tip.17, 19 Furthermore, increasing the
[2] =>
Untitled
ENDO NEWS
18
Endo Tribune Asia Pacific Edition | 12/2015
volume of irrigant delivered could
help to improve refreshment in
such cases.20, 31, 32
expected even in severely curved
canals.
Wall shear stress
The effect of curvature on irrigant exchange has been studied indirectly by Nguy and Sedgley.33
They report that only severe curvatures in the order of 24–28°
hampered the flow of irrigants. If
the canal is enlarged to at least size
30 or 35 and a 30-gauge flexible
needle placed near the WL is used,
then irrigant refreshment can be
The frictional stress that occurs
between the flowing irrigant and
the canal wall is termed “wall shear
stress”. This force is of relevance in
root canal irrigation because it
tends to detach microbial biofilm
from the root canal wall. Currently,
there is no quantitative data on the
minimum shear stress required for
the removal of microbial biofilm
from the canal wall. Yet, the nature
of wall shear stresses produced
within the root canals during irrigation provides an indication of the
mechanical debridement efficacy.
In open-ended needles, an area of
increased shear wall stresses develops apical to the needle tips, while
in closed-ended needles, a higher
maximum shear stress is generated
near their tips, on the wall facing the
needle outlet.34 Thus, in open- and
closed-ended needles, optimum debridement is expected near the tip
of the needle.16, 34 Consequently, it is
necessary to move the needle inside
the root canal, so that the limited
area of high wall shear stress involves as much of the root canal wall
as possible. The maximum shear
stress decreases with an increase in
canal size or taper. Thus, overzealous root canal enlargement above a
certain size or taper could diminish
the debridement efficacy of irrigation (Figs. 1a–d & 2a–d).
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Enhancing
irrigation dynamics
using physical
irrigation methods
Fluid dynamics studies on apical
negative-pressure irrigation have
demonstrated maximum apical
penetration of the irrigant, without
any irrigant extrusion. This finding
highlights the ability of apical negative-pressure irrigation to be safely
used at the WL, circumventing the
issues of vapour lock effect.35 Nonetheless, the apical negative-pressure
irrigation produced the lowest wall
shear stress. This decrease in the wall
shear stress could be attributed in
part to the reduction in the flow rate
with this irrigation system.
Passive ultrasonically assisted irrigation, when compared with other
irrigation methods, showed the
highest wall shear stress along the
root canal wall, with the highest turbulence intensity travelling coronal
from the ultrasonic tip position. The
lateral movement of the irrigant
displayed by this method has important implications with respect to
its ability to permit better interaction between the irrigant and the
root canal wall, and to potentially
enhance the interaction of irrigants with intra-canal biofilms2, 3, 35
(Figs. 1a–d & 2a–d).
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In the case of a closed-ended needle, placement should be within
1 mm short of the WL, so that optimum irrigant exchange can be ensured. The apical negative-pressure
irrigation did not generate marked
wall shear stress values, but allowed
the flow of irrigant consistently up to
the WL. It was the safest mode of irrigation when used close to the WL. The
passive ultrasonically assisted irrigation generated the highest wall shear
stress. The use of combined methods
to obtain optimum disinfection and
to circumvent the limitations of one
method is recommended.
Editorial note: A list of references is available from the publisher.
Credit Card
Credit Card Number
The requirements of adequate irrigant penetration, irrigant exchange,
mechanical effect and minimum risk
of apical extrusion oppose each other
and a subtle equilibrium is required
during irrigation. Ideally, in a canal
enlarged to size 30 or 35 and taper
0.04 or 0.06, an open-ended needle
should be placed 2 or 3 mm short of
the WL to ensure adequate irrigant
exchange and high wall shear stress,
while reducing the risk of extrusion.
Expiration Date
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fax: +49 341 48474 173 | e-mail: subscriptions@dental-tribune.com
Anil Kishen obtained his dental education in
India and is Professor of Endodontics at the
University of
Toronto’s Faculty of Dentistry
in Canada. He can be contacted at
anil.kishen@dentistry.utoronto.ca.
[3] =>
Untitled
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[4] =>
Untitled
TRENDS & APPLICATIONS
20
Endo Tribune Asia Pacific Edition | 12/2015
Use of mineral trioxide aggregate in
endodontic retro-filling
By Fernanda Maria Klimpel, Brazil
Mineral trioxide aggregate (MTA) is
an endodontic sealer that emerged
on the market in 1998. Through
proven scientific results it has became
the true miracle of endodontics. An
excellent sealing material, it provides
setting expansion and integrity of the
seal owing to low solubility, tissue
biocompatibility and high biological
regeneration. The release of calcium
ions provides antibacterial activity. Its
radiopacity is excellent, and it can be
used for thermal condensation owing
to its melting point of 150 °C.
MTA also has good capacity for
adhesion to dentine, making it resistant to the forces of displacement, and greater sealing power
than other cements when tested to
assess the quantity of bacterial infiltration. It is indicated for treatment
of perforations in the furcation region, of internal resorption, and of
root perforations via surgery when
it is impossible to treat the perforation via the canal or treatment has
been unsuccessful; for use in paraendodontic surgery as a retro-filling
material; and for direct pulpal protection, pulpotomy, apexogenesis
and apexification.
Literature review
MTA is a biocompatible material
with numerous clinical applica-
4
7
10
1
2
3
Fig. 1: Panoramic radiograph.—Fig. 2: Periapical radiograph of the apex showing the presence of a fistula.—Fig. 3: Periapical
radiograph of the endodontic retreatment.
tions in endodontics. It was first
used experimentally by Lee and
Monsef.1 However, approval of its
use in humans by the American
Dental Federation was not granted
until 1998.2
responsible for the material’s radiopacity. The principal molecules
present in MTA are calcium and
phosphorus ions, which are also
the main components of dental
tissue, giving MTA excellent bio-
of root canals. Although the retrofilling material is very important,
good sealing of the suitable apex is
made for this purpose. According
to Assis et al., many techniques and
instruments have been recom-
“Both brands of MTA have been significantly
evaluated and no other material has shown
more progressive results.”
It is composed primarily of tricalcium silicate, tricalcium aluminate, tricalcium oxide and silicate
oxide, as well as a small quantity of
other mineral oxides and the addition of bismuth oxide, which is
5
8
11
compatibility when in contact with
cells and tissue.3
mended for carrying out apical
preparations.4
MTA has been investigated as an
alternative material in endodontics and can be used in retro-filling
Both brands of MTA have been
significantly evaluated and no
other material has shown more
6
9
12
Figs. 4 & 5: Instruments for endodontic retro-filling.—Fig. 6: Supra-periosteal anaesthesia.—Figs. 7 & 8: Detachment of the flap.—Fig. 9: Cutting of the root apex with
a high-rotation drill.—Fig. 10: Mini-handpiece for preparation of the apex.—Fig. 11: MTA restorative material (liquid and powder).—Fig. 12: Compounded MTA.
progressive results.5 According to
Pozza et al., the use of MTA in cavity walls, unlike other materials,
achieves the best seal against infiltrations.6 Different materials have
been used to seal the paths connecting the root canal and the paraendodontic tissue. However, none
of them have achieved results as
promising as those of MTA, and various studies have proven that MTA
is the best on the market today.7
According to Leal, MTA cement has
effective sealing capacity.8
According to Bernabé et al., conventional endodontic treatment
is not able to resolve some cases
and para-endodontic surgery is
required to obtain a good result.9
The filling material used must not
be toxic or mutagenic, and has to
be biocompatible and insoluble.
The material used in retro-filling
distinguishes a good para-endodontic surgery from a bad one. MTA
achieves the best result specifically
for sealing between the tooth and
external surface.
Endodontic treatment has become more practical owing to the
new methods and techniques, with
the emergence of materials with
excellent physical and biological
properties. The literature deals
with various materials used in
retro-filling, but generally speaking these materials do not have all
the requisite properties to be able
to remain in the cavity, such as
biocompatibility, radiopacity, insolubility in periapical fluids, easy
compounding, non-staining of the
periradicular tissue, good adaptation and sealing capacity.10 An
ideal material to replace amalgam
should offer adhesion, promote
hermetic sealing, be biocompatible, be radiopaque, be easy to
compound and provide for an environment favourable for tissue
regeneration.11
According to Hellwig et al., paraendodontic surgeries expose and
remove dental apices, promote
retro-cavitations along the axis of
the root canals, and retro-fill them
with materials that promote their
sealing.11 Para-endodontic surgery
is an excellent option for conservative treatment of teeth with
chronic periapical lesions, and
treatment by the conventional
method is impractical in some
cases.12
According to Jacobovitz et al.,
treatment of inflammatory resorption must be directed at combating
endodontic infection.13 In certain
cases, clinical resolution using conventional endodontic treatment
can become unfeasible owing to
the difficulties of performing instrumentation and adequate fill-
[5] =>
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TRENDS & APPLICATIONS
21
Endo Tribune Asia Pacific Edition | 12/2015
ing of the apical region. In these
situations, alternative techniques
for preparation of the root canal
and filling may be necessary, in addition to the use of supplementary
surgical treatment. Some cases
may be treated with the use of
a laser, but this does not change
the pattern of microfiltration of
retro-fillings with MTA.14
13
Para-endodontic surgeries have
various procedural methods that
aim to resolve failures or accidents
that occur in conventional endodontic treatment.15 According
to Girardi et al., apicectomy is a
method of para-endodontic surgery that entails the separation of
the apical portion from the root.16
It is performed when there is no
regression of the apical lesion after
the alternatives of conventional
endodontic therapy have been exhausted in an attempt to eliminate
the apical micro-organisms and
their toxic products.
The use of a high-quality retrofilling material is indispensable; if
an inferior quality material is used,
an increase in apical infiltration
may occur, since the dentinal
tubules are more exposed by certain cutting angles and permeability is hence increased, and this is
important at the time of applying
the filling material.17
According to Oliveira et al., in an
apicectomy with retro-filling using
MTA and monitoring after five
years, it was observed that teeth
with a persistent periapical fistula,
after having undergone a suitable
endodontic treatment, the surgical
retreatment with retro-filling may
be an efficient option in the resolution of the infection and repair of
the periapical tissue.18
The literature confirms that MTA
presents excellent physical, chemical and biological properties, which
justify it as the material of choice in
the treatment of radicular resorption. It is a material that, compared
with other restorative materials,
has less microleakage and is capable of inducing the formation of
mineralised tissue, such as bone,
dentine and cementum, owing to
it reaching a pH plateau of around
12.5 in 3 hours. According to Costa
et al., who analysed the clinical
application of MTA in relation to
radicular resorption, in cases in
which radicular resorption is minimal, the canal is filled with calcium
hydroxide to stimulate the repair,
closing the access cavity with zinc
oxide and eugenol.19
Among the various advantages
of MTA is minimal radiopacity,
which has proven to be an important criterion and contributes to
it being considered the best choice
by the dental surgeon in relation
to biomaterials to be used in paraendodontic surgery.20
According to Barros and Araújo
Filho, MTA has been used successfully in filling the apical space
of the root canal. In addition to
its excellent sealing capacity, it
is biocompatible with the peri-
15
14
the region, proving the success of
the case. At the end of the surgical
treatment, the patient was referred
for prosthetic treatment.
radicular tissue, and induces the
formation of cementoblasts and
osteoblasts.21
Clinical case
This case illustrates the use of
MTA for sealing the root perforation and the effectiveness of the
retro-filling material after apicectomy (additional surgery; Figs. 1–17).
A 51-year-old patient presented to
the Universidade Tuiuti do Paraná
dental clinic (Brazil) complaining
about a gap in the gingiva above
tooth #11, from which a large quantity of purulent discharge was draining. In the radiographic examination,
an extensive radiolucent area was
found, indicating a fistula (periapical lesion) involving the periapical
region of the tooth in question.
During the endodontic treatment, the secretion into the tooth
could not be controlled. Even 23 days
after treatment, with changes to
the intra-canal medication, the
fistula returned and the exudate
drainage via the canal persisted.
Definitive sealing of the root perforation was then opted for, utilising
MTA and continuing with changes
of calcium hydroxide in the root
canal. Owing to the persistence of
the exudate via the canal, it was decided to perform endodontic filling, followed by supplementary
surgical treatment (apicectomy)
with retro-filling with MTA, conserving the tooth structure as
much as possible.
The surgery was performed under local anaesthetic with an infraorbital nerve block and supplementary infiltrative anaesthesia
at the apex of the tooth, as well as
a nasopalatine nerve block. The
anaesthesia used was 3 % mepivacaine with 1:1,000,000 adrenaline.
The incision was made with a #15
scalpel blade and a flap was raised.
The osteotomy was performed
with a high-rotation drill of the
700 series in order to gain access to
the periapical region. The lesion
was curetted with a short curette.
An apicectomy was performed
with the drill and 2 mm of the apex
was removed. The cavity for retrofilling was prepared with a spherical drill under constant irrigation
with saline solution, and then the
retro-filling with MTA was performed. After condensation of the
material in the cavity, the excess
was removed with a periodontal
curette. Finally, the flap was repositioned and then sutured.
One 750 mg pill of acetaminophen every 6 hours for two days
Conclusion
17
16
Fig. 13: Removal of the extra pre-existing cones.—Fig. 14: Placement of the MTA
material.—Fig. 15: Condensation of the MTA in the canal.—Fig. 16: Suturing with
4-0 silk thread.—Fig. 17: Final radiograph of the apicectomy.
was prescribed. In the seven-day
postoperative control period, the
patient had no symptoms incompatible with the surgery performed
and the healing appeared normal.
These circumstances held for the
full monitoring period, over the
course of a year, as the radiograph
one year after treatment established new bone formation in
According to the methodology
used in this case and considering its
results, it can be concluded that the
MTA material used was efficient in
the formation of a new mineralised
tissue barrier, completely sealing
the apical portion of the canal.
Fernanda Maria Klimpel is working as
a dentist in Brazil.
AD
The South African Society of
Endodontics & Aesthetic Dentistry
3-6 June 2016
Cape Town
South Africa
www.ifea2016.com
Abstract &
Poster
Submissions
now open
Endodontic Excellence at the Apex of Africa
SPONSORS
[6] =>
Untitled
TRENDS & APPLICATIONS
22
Endo Tribune Asia Pacific Edition | 12/2015
The One Shape Procedure Pack
A unique solution for root canal shaping
Dr Tara Mc Mahon, Belgium
1
2
3
4
5
6
7
8
Fig. 1: One Shape Procedure Pack.—Fig. 2: Pre-op radiograph of tooth #17.—Fig. 3: Opening of the pulp chamber (P: palatal canal; DB: distobuccal canal; MB: mesiobuccal canal).—Fig. 4: Elimination of overhangs
with ENDOFLARE (P: palatal canal; DB: distobuccal canal; MB: mesiobuccal canal).—Fig. 5: After the passage of ENDOFLARE, access to the distobuccal canal is straightened (P: palatal canal; DB: distobuccal canal;
MB1: first mesiobuccal canal; MB1: second mesiobuccal canal).—Fig. 6: Exploration file, #10 MMC, in the distobuccal canal.—Fig. 7: One G.—Fig. 8: Radiograph of One G in the second mesiobuccal canal.
The objective of endodontic treatment is the elimination of pulp
debris or the bacterial biofilm and
its toxins from the root canal system in order to prevent or eliminate any periapical lesion.1 For this
purpose, root canal shaping is an
essential, necessary and complex
step. Essential because it allows
indispensable irrigation, necessary
to achieve 3-D obturation of the
endodontic root canal system2 and
complex because of the infinite
complexity of the root canal anatomy.3
Over the past several years, the
definition of an endodontically
successful root canal treatment
has changed considerably. In 1986,
success was based on the complete
disappearance of the periapical lesion.4 In 2004, the concept evolved
and the terms “recovered tooth”,
“tooth on the way to recovery”
and “diseased tooth”5 were used.
In 2011, the terminology of
“functional tooth” versus “nonfunctional tooth” was finally in-
troduced.6 Despite this, the concepts for root canal shaping established by Schilder in 1974 remain
unchanged,7 namely with respect
to the initial root canal anatomy
and position of the apical foramen, as well as conservation of
root canal patency and obtainment
of a sufficient taper to guarantee
the penetration of the irrigating
solutions to the apex.
Practitioners are familiar with
these concepts and try to implement them in the best possible
way. However, endodontic treatment remains an area that poses
great difficulties for dental surgeons, and time constraints can
often lead to inadequate treatments. Thus, general practitioners
desire a simple, efficient and rapid
solution that allows reproducible
treatments. The introduction of
rotary nickel-titanium (NiTi) instruments in endodontics in the
late 1980s has revolutionised the
discipline. The material’s extreme
elasticity imparts great flexibility
to instruments with greater diameters and tapers than those of
hand files. Stainless-steel hand
files are more rigid and can lead
to the creation of an apical ledge,
canal transportation, a crack in
the apical foramen or even instrument fracture.8, 9
Although NiTi instruments allow reliable and reproducible
results, they present a higher risk
of fracture than do stainless-steel
files, particularly those used in
continuous rotation, which is due
to cyclic fatigue or higher torsional stress. Instrument fractures
caused by cyclic fatigue occur
without prior deformation visible
to the naked eye. They are therefore impossible to foresee with
certainty.10
Too often does this elevated risk
of instrument fracture result in
general practitioners abandoning
endodontics altogether. However,
respecting several simple principles, such as using the speed
and torque recommended by the
instrument manufacturer, preenlarging the root canal, using
vertical up-and-down movements,
as well as cleaning and performing
visual control of the instrument
after each passage, makes the
practitioner’s work less stressful
and more relaxed.
The introduction of single-use
instruments not only eliminates
the risk of cross-contamination,
but also considerably reduces the
risk of instrument fracture due
to cyclic fatigue and simplifies
the operating procedure. MICROMEGA has designed the One Shape
Procedure Pack, which contains
an ENDOFLARE file, a #10 MMC
file, a One G file, a #15 MMC file and
a One Shape file (Fig. 1). It simplifies
the operating procedure, removes
the need for instrument maintenance and makes stock management easier. All of the necessary
instruments for the endodontic
treatment are single-use files supplied in sterile packaging.
9
10
11
12
13
14
15
16
Operating procedure
Each endodontic treatment requires a preoperative radiograph
taken with a radiograph film
holder (Fig. 2). Once a dental dam
has been placed and the access
cavity has been prepared, the
root canal entrances are localised
and the pulp chamber is irrigated with sodium hypochlorite
(Fig. 3).
The first step of the root canal
preparation is the enlargement
of the canal entrances. As the
first instrument in the One Shape
Procedure Pack, ENDOFLARE (with
a diameter of 0.25 and a 0.12 taper)
is used with up-and-down movements and pressure on the canal
walls in the first 3–4 mm of the
root canal to enlarge the canal
orifices. In this case, ENDOFLARE
eliminates the dentinal overhang at the entrance to the distal
root canal (Fig. 4) and lays open
the second mesiobuccal canal
(Fig. 5).
Fig. 9: Photograph of One G in the second mesiobuccal canal (P: palatal canal; DB: distobuccal canal; MB1: first mesiobuccal canal; MB1: second mesiobuccal canal).—Fig. 10: One Shape.—Fig. 11: Passage of
One Shape in the canal: two-thirds of the WL, 3 mm short of the WL, and WL.—Fig. 12: Radiograph of One Shape in the second mesiobuccal canal.—Fig. 13: Photograph of One Shape in the second mesiobuccal canal.—
Fig. 14: Radiograph with the master cone.—Fig. 15: Post-op radiograph.—Fig. 16: Post-op radiograph of tooth #17.
[7] =>
Untitled
TRENDS & APPLICATIONS
23
Endo Tribune Asia Pacific Edition | 12/2015
17a
17b
torque of 2.5 Ncm. Root canal
shaping is performed in three
steps with progression of One
Shape to two-thirds of the WL,
3 mm short of the WL, and the
WL (Fig. 11). Between each passage,
the root canal is abundantly irrigated with sodium hypochlorite
and patency is checked with a #10
file. The instrument’s spires must
be systematically cleaned and
visually inspected.
17c
Figs. 17a–e: Pre-op photograph (a). Radiograph of One G in the second mesiobuccal
canal (b). Radiograph of One Shape in the
second mesiobuccal canal (c). Radiograph
with the master cone (d). Post-op radiograph (e).”
17d
The exploration file (#10 MMC)
serves to evaluate the root canal’s
complexity. It is introduced into
the root canal without axial constraints in the coronal zone, owing
to the previous action of ENDOFLARE. Any coronal interference
that might hinder the file’s passage must be eliminated to make
the treatment as safe as possible
(Fig. 6).
The second step of the root canal
preparation is the exploration of
the root canal and the creation
of a glide path. This step entails the
pre-enlargement of the root canal
and facilitates the passage of the
following rotary shaping instrument. Root canal exploration and
glide path development are performed with stainless-steel hand
files or rotary NiTi files.8 It has
been shown that the use of a
highly flexible instrument with an
asymmetrical cross-section reduces the risk of canal transportation.9 In addition, this kind of
cross-section combined with a
variable helical pitch diminishes
screwing effects.11
The second rotary instrument
in the One Shape Procedure Pack is
One G (Fig. 7). This NiTi instrument
with a diameter of 0.14 and a
Stress-free, relaxed working: Since
the instruments are single-use only,
the risk of instrument fracture due
to cyclic fatigue is considerably reduced and there is no risk of crosscontamination.
Short learning curve: All of the rotary
instruments are used in continuous
rotation.
Rapidity of the root canal preparation:
The gain in time during root canal
shaping allows for a more thorough
final irrigation.
Simplification of the operating procedure: A single instrument is used for
glide path creation, and one instrument for root canal shaping.
Gain in time for the dental assistant:
Simpler and quicker preparation of
the working materials, since no
cleaning and no sterilization of the
instruments are required after the
treatment. Thus, there is more time
to assist the practitioner during
treatment.
Optimised organisation in the dental
office: Stock management is easier
and less storage space is required.
better upward transport of the
debris and limit screwing effects.
Owing to its characteristics, One
Shape causes less extrusion of debris and irrigating solution in the
apical zone than other single-file
systems available on the market.14
17e
0.03 taper has an asymmetrical
cross-section. Its three cutting
edges are situated on three different radiuses to the root canal axis.
One G also has a variable helical
pitch and thus variable helical
angles. The narrower the angle,
the more active the rotating instrument, and the wider the angle,
the greater the efficiency of the
instrument’s traction.8 All of these
features provide One G with a high
flexibility and great efficiency.
Clinically, if the root canal is
patent, One G is taken to the working length (WL) previously determined with the #10 MMC file and
an apex locator. However, if the root
canal is not patent, One G penetrates
with vertical up-and-down movements on the canal axis down to the
length attained by the #10 MMC
file. This allows the elimination
of constraints in the cervical and
middle thirds of the root canal. The
#10 file is then pre-curved in order
to check the canal patency. The
WL is determined and transferred
to One G, which is then taken to
the WL at a speed of 250–400 rpm
and a maximum torque of 1.2 Ncm
(Figs. 8 & 9). After the creation of the
glide path with One G, the #15 MMC
file must penetrate down to the WL
without constraints. The root canal
is now ready for shaping.
The third rotary instrument
is One Shape (Fig. 10). This NiTi
instrument with a diameter of
0.25 and a 0.06 taper has a variable
cross-section. The apical 2 mm of
its active blade with a global length
of 16 mm has a triple-helix crosssection with three cutting edges
situated on three different radiuses to the canal axis. The following 7.5 mm constitutes a transitional zone that terminates in a
double-helix section of 6.5 mm in
the coronal part of the file.12
The cutting effect of the two cutting angles in the coronal zone is
more important and allows more
efficient elimination of the debris,
whereas the three cutting angles
in the apical zone provide the
instrument with a better centring
ability, a higher resistance totorsional constraints and a better
capacity to negotiate curves.13 The
instrument’s tip is inactive and
allows for a smooth progression
in the root canal. The helical pitch
and angle are variable along the
instrument and thus guarantee
The instrument progresses with
an up-and-down movement of
low amplitude and without excessive pressure. One Shape is used in
continuous rotation with a speed
of 350–450 rpm and a maximum
One Shape performs the root
canal preparation quicker than
other single-file system.15 This
gain in time must be used for the
indispensable final irrigation.
Editorial note: A list of references is
available from the publisher.
Dr Tara Mc Mahon
is a working as
a dentist in an
endodontic practice in Brussels,
Belgium.
AD
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