Recent trends in root canal obturation

In recent years, there has been an increasing concern about the poor sealing

properties of the conventional root-filling materials, gutta-percha and the different

sealers . Many studies have demonstrated microleakage in canals filled with these

materials that may allow ingress and propagation of bacteria resulting in

infection . In response to the shortcomings of gutta-percha recent introduction of

an alternative root filling material offers the promise of adhesion to root canal

dentine

The Monoblock Concept

An ideal endodontic filling material should create a“monoblock”. This term refers

to a continuous solid layer that consists of an etched layer of canal dentin

impregnated with resin tags which are attached to a thin layer of resin cement

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that is bonded to a core layer of resilon which makes up the bulk of the filling

material. In other words the monoblock concept means the creation of a solid,

bonded, continuous material from one dentin wall of the canal to the other.

One added benefit of the monoblock is that research has shown that it strengthens

the root by approximately 20 percent.

Classification of Monoblock concept based on number of interfaces present

between corefilling material and bonding substrate:

Primary: In this obturation is completely done with core material, for example, use

of MTA for obturation in cases of apexification.

Secondary: In this bond is there between etched dentin of canal wall impregnated

with resin tags which are attached to resin cement that is bonded to core layer, e.g.

resilon based system.

Tertiary: In this conventional gutta-percha surface is coated with resin which bond

with the sealer, which further bond to canal walls, e.g. Endo Rez and Activ GP

system.

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Resilon

Resilon has been developed to replace gutta-percha and traditional sealers for root

canal obturation.It offers solutions to the problems associated with guttapercha:

1. Shrinkage of gutta-percha after application of heat.

2. since gutta-percha does not bind physically to the sealer, it results in gap

formation between the sealer and the gutta-percha.

This resilon core material bonded to the sealer by polymerization. When it sets, no

gaps are seen due to shrinkage.

Resilon system is comprised of the following components:

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1. Primer: It is a self etch primer, which contains a sulfonic acid terminated

functional monomer, HEMA (hydroxyethyl methacrylate), water and a

polymerization initiator. conditions the dentinal surface of root canals,

demineralizing it,and exposing the collagen matrix

2. Resilon sealer (Epiphany) a dual-cured, resin-based composite sealer. bonds to

both the root dentin and Resilon cones.

The resin matrix is comprised of Bis-GMA ((bisphenylglycidyl dimethacrylate),

ethoxylated Bis-GMA, UDMA (urethane dimethacrylate,) , and hydrophilic

difunctional methacrylates. It contains fillers of calcium hydroxide, barium

sulphate, bioactive glass, bismuth oxychloride and silica. The total filler content is

approximately 70 percent by weight. The preparation of the dentin through these

chemical agents may prevent shrinkage of the resin filling away form the dentin

wall and aid in sealing the roots filled with resilon material.The second generation

of methacrylate sealer replaced the original by the introduction of the Epiphany SE

Self-Etch Sealer a self-etch dual-cure, hydrophilic resin sealer that bonds to both

Resilon and dentin, without a separate priming step

3. Resilon core material: It is a thermoplastic synthetic polymer based (polyester)

root canal core material that contains bioactive glass, bismuth oxychloride and

barium sulphate. The filler content is approximately 65 percent by weight.

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This new material has shown to be biocompatible, noncytotoxic and

nonmutagenic. The excellent sealing ability of the resilon system may be attributed

to the “mono block” which is formed by the adhesion of the resilon cone to the

Epiphany sealer, which adheres and penetrates into the dentin walls of the root

canal system. The material is clinically used exactly like gutta-percha in that it can

be applied with warm and cold obturation techniques

EndoREZEndoREZ (ER) is a hydrophilic, two-component (base and catalysts), dual-

curing self priming sealer. based on the urethane dimethacrylate (UDMA)

molecule.EndoREZ has hydrophilic characteristics providing penetration into

dentinal tubules. The radiopacity is equivalent to gutta-percha, providing

simplified radiographic interpretation. EndoREZ does not compromise the

function of dentin bonding agents or luting resin polymerization.

EndoREZ is designed to be used with EndoREZ Points and/or gutta percha for

the filling of cleaned and shaped root canals. EndoREZ, in conjunction with a

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master cone and accessory cone, provides optimum sealing. Although Endo-

REZ Points are recommended, EndoREZ may be used with all conventional

endodontic obturation techniques.

EndoREZ Points are standard ISO-sized gutta percha points overlayed with a

thin resin coating, which bonds chemically with EndoREZ sealer and other

resin-based sealers. 

The EndoREZ obturation system with single or multiple EndoREZ Points

creates a solid, ideal seal &true monoblock in the canal space

Activ GP

This system is composed of a core material containing gutta-percha which is

impregnated and coated on its external surface with glass ionomer. The

accompanying sealer is a traditional glass ionomer sealer which can adhere

chemically and micromechanically to the Activ GP cones and bond to the

dentin.Glass ionomer–based sealers had been developed based on glass

ionomers’ high affinity for bonding to dentin. Coating Activ GP with

glass ionomer particles is done to overcome the drawback of inadequate

bonding between gutta-percha and glass ionomer sealer.

• Activ GP Sealer has been formulated with an extended 12 minute working

time, giving you the necessary time to place the material.

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• The natural adhesion of Glass Ionomer to dentin (ionic bond) means there’s

no need for a bonding agent (primer) and the associated application technique

challenges.

Chemical and micromechanical adhesion between the canal walls, the Activ GP

sealer and the Activ GP gutta percha points results in a monoblok within the

canal, completely sealing the canal from orifice to apex.

SmartsealSmartseal is a recently introduced root canal obturating system based on polymer

technology. Its principle is based on the hydrophilic nature of the obturating points

which can absorb surrounding moisture and expand resulting in filling of

voids and spaces.

Smartseal is a single point and sealer obturation system & constructed in two parts:

Central Core - this provides the point with the flexibility to allow it to easily pass

around any curves in the prepared canal, while being rigid enough to pass easily to

length in narrower canals .

Outer Polymer Layer - this hydrophilic, hydrogel layer allows the point to swell

in order to adapt to the ramifications of the root canal .

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Advantages of using hydrogels over existing obturation materials are: --Any

geometry of point can be accurately made

-Controlled expansion - Biocompatibility

Smart paste Bio is a hydroxyapatite based sealer that is used with the smartseal

obturation points. The sealer is delivered in a pre-mixed syringe and is simply

injected into the root canal. The sealer will expand slightly on setting and provides

a highly biocompatible alternative to traditional endodontic sealers.

Any Shape is Possible .

a system has been developed which allows the hydrogel coating on the propoints to

be cast to accurately match the shape of the canal prepared with any file system .

Currently the prosmart range includes points in 4 and 6% tapers, and points

engineered to fit the finishing files in the ProTaper™ and Sendoline™ S5 systems .

However the versatility of the product allows us to create points to match every file

system, past, present or future....

Controlled Expansion The smartseal polymer is hydrophilic which allows the minute amount of water

present in the root canal to be absorbed by the points. This water can hydrogen

bond to the polar sites present, enabling expansion within the polymeric chains .

The rate and extent of this expansion is controlled as part of the manufacturing

process. Known as Hydrogels, polymers like smartseal, expand with a miniscule

force that is well below the reported tensile stress of dentine and a fraction of the

force generated when using traditional techniques such as warm vertical

compaction. This gentle expansion occurs within the first 4 hours after placing the

point into the canal and allows the point to gently adapt to any irregularities in the

root canal. This results in the polymer and sealer being expressed into the dentinal

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tubules. The slight positive pressure against the canal wall that is created forms a

seal that is virtually impermeable to bacterial micro-leakage .

The impermeability of the seal is effectively demonstrated in the following images

from dye penetration studies. The dye is able to pass into the dentine but is

completely prevented from passing into the root canal space occupied by the

prosmart point.

MINERAL TRIOXIDE AGGREGATE (MTA)Developed by Dr Torabinejad at Loma Linda University in 1993.

Composition

It is available in two colors White and Gray color

Gray color

–It contains tricalcium silicate,

–Dicalcium silicate,

–Tricalcium aluminate

–Bismuth oxide

–Calcium sulfate

–Tetracalcium aluminoferrite

White color: It has same composition as that of gray color MTA except the lack of

tetracalcium aluminoferrite. Thus, it is white in color

Properties

1 .pH of MTA is 12.5 (When set) so, it has biological and

histological properties similar to calcium hydroxide.

2 .Setting time is 2 hours and 45 minutes.

3 .Compressive strength is 40 MPa immediately after setting and 70 MPa after 21

days

4 .Contrast to Ca(OH)2, it produces hard setting nonresorbable surface

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5 .It sets in a moist environment (hydrophilic in nature).

6 .It has low solubility.

7 .It shows resistance to marginal leakage.

8 .It also reduces bacterial migration.

9 .It exhibits excellent biocompatibility in relation with vital tissues.

10 .The compressive strength of MTA is equal to IRM and

SuperEBA but less than that of amalgam.

11 .MTA is also known as Portland’s cement except for

addition of bismuth oxide which is added for modifying

its setting properties. Its consistency is similar to very hard

cement, which can be compared to concrete.

Commercially it is available under the name ProRoot MTA (Dentsply).

Advantages of MTA

1 .Water based chemistry, so requires moisture for setting

2 .Excellent biocompatibility

3 .Normal healing response without inflammation

4 .Least toxic of all the filling materials

5 .Reasonably radiopaque

6 .Bacteriostatic in nature

7 .Resistance to marginal leakage.

Disadvantages of MTA

1 .Difficult to manipulate

2 .Long setting time (3-4 hours)

3 .Costly.

Indications of use of MTA

1 .As a pulp capping material.

2 .For the repair of root canals as an apical plug during apexification.

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3 .For the repair of root perforations during root canal therapy.

4 .For the repair of root resorptions.

5 .As a root-end filling material.

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