monoblock in endodontics

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MONOBLOC CONCEPT
IN ENDODONTICS
Presented By
Dr. Laxmi Murkey
Dr. Vibha Hegde
Dr. Sharad Kokate
Dr. Ushaina Fanibunda
Dr. Ashwin Jain
Guided By
Journal club

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Monoblocks in root canals - a hypothetical
or a tangible goal
J Endod. 2007
 The term monoblock, literally meaning a single unit
 Franklin R. Tay first described the concept of
monoblock in endodontics.
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MONOBLOCK
ONE UNIT- GAP FREE
ROOT FILLING MATERIALS POST AND CORE
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 A primary monoblock has only one interface that
extends circumferentially between the material and
the root canal wall.
HEMA containing root
filling material Hydron
(Hydron Technologies)
was marketed
commercially for en
masse filling of root
canals
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 Disadvantage of Hydron
 Hydron was injected - presence of residual moisture
within the root canals .
 Chirila TV et al stated that HEMA polymerizes in the
presence of water to form soft hydrogels that are highly
permeable and leachable.
 Moduli of elasticity of porous poly(HEMA) hydrogels
such as Hydron ranges from 180–250 MPa
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 Orthograde obturation with mineral trioxide aggregate -primary
monoblock in attempts to strengthen immature tooth roots
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 The compressive elastic moduli of Portland cement increase
after 14 days to 15 GPa (i.e. 15,000 MPa) .
 MTA does not contribute in root strengthening, apart from its
ability to stimulate cementogenesis in apexification and root
end fillings.
 Lack of bonding to dentin, and that although it has high
stiffness in compression, it has little strength in tension
Baek SH, Plenk H Jr, Kim S. Periapical tissue
responses and cementum regeneration with
amalgam, SuperEBA, and MTA as root-end
filling materials. J Endod 2005
Tay and Pashley
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 MTA interacts with dentin by releasing calcium and
hydroxyl ions results in the formation of apatite-like
interfacial deposits .
 orthograde obturations and perforation repair
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Secondary Monoblocks
Secondary monoblocks are those that have
two circumferential interfaces, one between
the cement and dentin, the other between
the cement and the core material.
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 The materials that constitute a monoblock should
have the ability to bond strongly and mutually to one
another, as well as to the substrate with which the
monoblock is intended to reinforce.
 These materials should have moduli of elasticity that
are similar to the substrate.
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 Modulus elasticity of gutta-percha points (ca. 80 Mpa) is
175–230 times lower than that of dentin (ca. 14,000–
18,600 Mpa), making them too plastic (i.e. not stiff
enough) to reinforce roots after endodontic therapy.
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 In 2004 with the advent of bondable root filling
materials that are advocated as alternatives to
conventional gutta-percha were introduced.
 Resilon (Resilon Research LLC, Madison, CT) is a
bondable root filling material that may be used for
either lateral or warm vertical compaction techniques
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Resilon - polycaprolactone -
based, dimethacrylate resin–
contains Bioactive glass
Epiphany Sealer. Primer &
a dual cure sealer
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 Initial studies on Resilon-filled root canals were
highly favorable.
 Resilon Monoblock System (RMS) that produces
ideal root obturations in terms of coronal sealing and
fracture resistance
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 It was studied later that large polymerization
stresses during their setting that may cause
debonding and gap formation along the periphery of
the root filling.
 The extremely high C-factor(above 1000) in root
canals has been cited as a possibility for not
achieving perfect seals in Resilon-filled root canals
Tay FR, Loushine RJ, Lambrechts P, Weller RN, Pashley
DH. Geometric factors affecting dentin bonding in root
canals: a theoretical modeling approach. J Endod
2005;31:584–9
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 Also it lacks a free radical-containing oxygen
inhibition layer - its bondability to resin- based
sealers has further been questioned
Tay FR, Hiraishi N, Pashley DH, Loushine RJ,
Weller RN, Gillespie WT, Doyle MD. Bondability
of Resilon to a methacrylate-based root canal
sealer. J Endod 2006;32:133–7.
Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay
FR, Ferrari M. Interfacial strength of Resilon and
gutta-percha to intraradicular dentin. J Endod
2005;31:809–13.
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 There is no difference between Resilon and gutta-percha in
strengthening and reinforcement of immature roots.
 The modulus of elasticity of Resilon was found to be 86.6 ±
43.2 MPa under dry conditions and 129.2 ± 54.7 MPa after one
month of water sorption .
 Thus, similar to gutta-percha, Resilon is not stiff enough to
achieve a mechanically homogeneous unit with root dentin
Williams C, Loushine RJ, Weller RN, Pashley
DH, Tay FR. A comparison of cohesive strength
and stiffness of Resilon and gutta-percha. J
Endod 2006;32:553–5
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Is Resilon the Solution?
• Studies have shown conclusive evidence of Resilon
being equally effective or even superior to gutta-
percha based systems however long-term studies on
leakage comparing gutta-percha and Resilon-based
systems have shown they showed more fluid
movement when tested at 16 months.
IEJ 2007
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• The question of biocompatibility of periapical
tissues with resin-based systems and leaching of
resin by-products still exists.
• So, due to the nonresorbable nature of resins, the
removal of obturating material in the cases of
overfills is a major concern.
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Tertiary Monoblocks
 An additional circumferential interface is introduced
by coating the non-bondable gutta-percha points
with materials that render them bondable to the root
canal sealers.
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Diisocyanate
isocyanato group - the
hydroxyl group of a
hydroxyl-terminated
polybutadiene -
hydrophobic component-
binds to the gutta-percha
cones
Isocyanato group – binds
to the hydrophilic
methacrylate functional
group producing a gutta-
percha resin coating that
is bondable to a
hydrophilic,
methacrylate-based dual-
cured resin sealer.
In the EndoRez system (Ultradent, South Jordan, UT)
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To-date, leakage and morphologic studies showed
that the seal of system is mediocre.
 polymerization shrinkage of the methacrylate-
based sealer .
 sealer bonds weakly to the pre-polymerized
proprietary coating – absence of oxygen inhibition
layer.
 Since the external proprietary resin coating is
uneven there can be partial detachment
J Adhes Dent 2005
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 In ActiV GP (Brasseler)- used with conventional
gutta-percha cones that are surface-coated with
glass ionomer fillers using a proprietary technique.
 It can be bonded to the root dentin via a glass-
ionomer sealer
Dent Today 2006
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 However, being a single cone technique,
coronal leakage of the ActiV GP system to
fluid filtration was worse than that achieved
with gutta-percha/AH Plus.
Monticelli F, Sword J, Martin RL, Schuster GS, Weller RN,
Ferrari M, Pashley DH, Tay FR. Sealing properties of two
contemporary single-cone obturation systems. Int Endod
J. in press
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• Hydrophilic polymer in the root canal, The
Smart-Seal System (endotechnologies,USA).
• The system consists of premade obturation
points (C-Points) containing a polyamide
core with an outer bonded hydrophilic
polymer coating.
• The polymer coating is a cross-linked
copolymer of acrylonitrile and vinylpyrrolidone
which has been polymerised and cross-
linked using allyl methacrylate and a thermal
initiator
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• The inner core is composed of two proprietary
nylon polymers: Trogamid T and Trogamid CX.
• Smartpaste bio is a resin based sealer designed
to swell through the addition of bioceramic filler
particles.
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 Smartpaste bio produces calcium hydroxide and
hydroxyapatite as by- products of the setting
reaction, rendering the material both anti-bacterial
while setting and very biocompatible once set.
 Also, it is hydrophilic in nature, allowing the C-
point to hydrate and swell to fill any voids.
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• The use of expandable obturating materials to
improve the seal of the root-filled canals
• Hydrophilic obturations of the root canal shows a
better resistance to bacterial leakage as compared
to hydrophobic obturations.
JCD 2015
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Monoblock in post and core
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• A customized polyethylene fibre post-core system
such as Ribbond (Ribbond Inc., Seattle, WA,USA)
can create a primary monoblock in a root
• It has a elastic modulus of 23.6 GPa (Eskitascioglu
et al. 2002) therefore, too high elastic modulus
creates interfacial stresses along the resin dentin
interface.
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35. + POLYETHYLENE FIBRE POST-CORE
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 Microleakage studies comparing different dowel
systems was done using fluild filtration test.
 Glass fibre and ribbond posts should least
microleakage when compared to zirconia and
stainless steel.
 Fracture resistance was better in glass fibre post as
compared to ribbond posts
J Prosthet Dent 2004
Clin oral investig 2012
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37. + Prefabricated post systems bonded to
root canal dentine via resin cements
represent a secondary monoblock
First implied existence of a mechanically homogeneous
monoblock is reported in 1996 with the bonding of
epoxy resin– based, carbon fiber–reinforced posts to
root dentin .
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• Epoxy- resin based matrices – did not bond to
methacrylate cements
• Carbon-fibre posts are black in colour and do
not lend themselves to aesthetic restorations
with all-ceramic units.
• These posts are also called glass-fibre and
quartz-fibre
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In the fibre posts the epoxy resin
matrix are replaced with highly
cross-linked , methacrylate resin
matrices that have the potential to
bond to methacrylate-based resin
cements
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 Since resin cements exhibits less microleakage and bond to
the tooth structure as compared to other cements
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Fiber posts that contain an external silicate coating
(DT Light SL, VDW GmbH, Munich, Germany),
Anatomic Post R(TD, St. Egéve, France) may be
considered as tertiary monoblocks
Tertiary monoblock = Fibre post + external silane
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Coating made of silane and
silicate is applied to the post
DT Light SL
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J.dent mater 2005
The adhesion between prefabricated FRC posts
and composite resin cores with and without post-
silanization was studied.
 For better adhesion , salinization is advisable
Choi et al. found that no additional surface
treatment is needed .
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‘ANATOMIC POST’
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• Theoretically, a reduction of the resin cement thickness should
result in a reduction of volumetric shrinkage.
• Polymerization shrinkage stresses along the cavity walls are
also present in a low compliance environment
• Introduction of a tertiary interface is problematic in that gaps
were found to be present between the fiber post and the relining
composite.
• These gaps may can act as stress raisers and result in eventual
adhesive failure and dislodging of the fiber post from the relining
composite.
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Thus, until non-shrinking composites are available the
pursuit of an ideal monoblock for reinforcing the root canal
may be viewed as an ideal goal.
CONCLUSION
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48. + Monoblocks in root canals: a finite elemental stress
analysis study
Aim
To investigate using finite element stress analysis (FEA)
primary, secondary and tertiary monoblocks created
either by adhesive resin sealers or by different adhesive
posts and to evaluate the effect of interfaces on stress
distribution in incisor models
2011 International Endodontic Journal
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(a) primary monoblock - Mineral Trioxide Aggregate
(b) Secondary monoblock - (MetaSEAL) and Resilon
(c)tertiary monoblock – EndoREZ
(d) primary monoblock - polyethylene fibre post-core (Ribbond)
(e) secondary monoblock - glass-fibre post and resin cement
(f) tertiary monoblock - bondable glass- fibre post
(g) tertiary monoblock - silane-coated ceramic post
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A 300 N load was applied from the
palatal surface of the crown with a 135
angle to the
tooth long axis.
Measured in von Mises stress unit
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RESULT
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 Stresses within roots increased with an increase
in the number of the adhesive interfaces.
 Creation of a primary monoblock within the root
canal reduce the stresses that occur inside the
tooth structure.
DISCUSSION
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• The palatal side of the MTA - decreased stress
accumulation (8.33–13.3 MPa)
• Composite resin in the access cavity has
increased stress at the coronal region.
• The MTA-treated model revealed that the material
kept the stress inside of the material body (1.67–
3.33 MPa) and directed towards the root.
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• The polyethylene fibre post-core system is considered to
create primary monoblocks in the present study.
• Von Mises stress values indicated that the stress
occurring coronally was high in primary monoblock model
• No stress was directed towards the root.
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secondary monoblock model revealed stress accumulation at the
interface between the Resilon and MetaSEAL
(13.3–20 MPa)
 Even the adhesive procedures alone are not
sufficient to strengthen dentine if the material is not
stiff enough (Grande et al. 2007)
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57. + • Debonding of posts because of contraction stress of
(Cagidiaco et al. 2008).
• Shrinkage stresses that occur with polymerization of
methacrylate-based resins specially in deep, narrow
canals
In the present study it was demonstrated that as
the number of interface increases the stresses
also increase but the distribution of stresses
were close to that of natural tooth.
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Fibre posts that contain an extra silicon coating such
as DT Light (VDW) or ceramic posts that require a
silane coating such as Cosmopost (Ivoclar) - tertiary
monoblocks.
• Stress values along the cement glass-fibre or ceramic
interface ranged from 1.67 to 15 Mpa for tertiary
monoblock models
• Furthermore, the stress was directed through the root.
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• Ceramics used for post fabrication present moduli of
elasticity that are above that of dentine
(Dietschi et al. 2007).
• The failure mode is mostly non-restorable (Eskitascioglu
et al. 2002, Maccari et al. 2003).
• Catastrophic fractures
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Concept of monoblock is
hypothetical
Accomplishing these “ideal monoblocks” in the root canal space is easier said than
done.
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o Over-thinning of the adhesive
o Even the entrapment of water droplets between the adhesive
and resin cements/sealer introduces crack tips in fracture
toughness testing .
o They can act as stress raisers that promote crack growth and
propagation during loading along the interface.
J Biomed Mater Res B Appl Biomater 2006
J Endod 1998
Problems associated
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“The goal of being able to bond a canal
from the minor constriction to the canal
orifice to the occlusal surface is a
desirable one”
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