Department of Conservative Dentistry

Retrograde Filling Materials

Submitted by;

Usha Muraleedharan

Roll No: 60

Batch 2003-04

Retrograde Root Canal Filling Materials

Introduction

A retrograde root canal filling is

done when the canal is poorly sealed from

the surrounding tissues.The purpose of a

root-end filling is to establish, as well as

possible, a hermetic seal of all apical

avenues in the tooth from the oral

environment to the periradicular tissues.The

following literature is a discussion of the

various materials that have been used for

retrograde filling. The main consideration

regarding the materials being used as

retrograde fillings is the fact that these

materials come in very close contact with

the periapical tissues.

A plethora of materials have

been evaluated, with leakage,

histocompatibility, and toxicity studies, in an

attempt to identify the "perfect" rootend

filling material. To date none exists, and

recommendations can only be made on

what appears to be the best tolerated,

clinically successful material. Therefore, the

endodontic surgeon must be cognizant that

the success of the procedure does not lie in

the essence of the 'apical filling material

used, and that this material will not

compensate for lack of proper nonsurgical

management of the root canal system. In

addition, it must also be understood that

lack of understanding of the materials to be

used, coupled with their improper use, could

contribute to ultimate failure on either a

short- or longterm basis.

Ideal requirements of a root end filling material According to Gartner and Dorn, a

suitable root-end filling material should be

(l) Able to prevent leakage of bacteria and their by-products into the periradicular tissues(2) Nontoxic (3) Biocompatible with the host tissues(4) Non carcinogenic(5) Insoluble in tissue fluids(6) Dimensionally stable(7) Unaffected by moisture during setting(8) Easy to use(9) Radiopaque(10) One might add it should not stain tissue (tattoo).

Materials used – properties and manipulation

The following list of materials

have been identified as root-end filling

materials in either scientific evaluation or

clinical usage. The parameters of each

material are discussed as to their

acceptability and technique. A brief outlook

on the manipulation of these materials is

also given.

1) Gutta-percha.

2) Silver cones.

3) Amalgam.

4) Zinc oxide-eugenol.

5) Cavit.

6) Polycarboxylates.

7) Composites.

8) Zinc phosphate.

9) Gold foil.

10) Glass ionomers.

11) Miscellaneous materials.

Before going into the details of

the various materials used for retro-grade

filing, a small review of the root canal

sealers that are used along with these

materials inorder to provide an impervious

seal at the apex is needed.

Root canal sealers

Root canal sealers, used in

conjunction with a solid core obturating

material, are intended to cooperatively

effect a fluid-tight or hermetic seal

throughout the root canal system. To

achieve this goal, and promote

periradicular healing, the sealer must

possess certain characteristics:

1. It is non-irritating,

2. It has a hermetic sealing ability with

dimensional stability,

3. It is bacteriocidal or static,

4. It is insoluble in tissue fluids, and

adheres to the dentinal surface.

These factors will have a direct

bearing on the seal of the canal system

subsequent to root-end resection and on the

periradicular healing at the resected root

face, with or without a root-end filling.

Commercial sealers are generally grouped

as

Zinc oxide-eugenol based,

Noneugenol based, and

Therapeutic based.

Of importance in the first group is

that residual eugenol that remains after

sealer set can affect the sealer's properties

or the periradicular tissue response.

Noneugenol based sealers use

solvents, such as chloroform or eucalyptol,

which have demonstrated toxicity in the

initial stages of sealer set.

Therapeutic sealers contain

materials such as iodoform,

paraformaldehyde, or trioxymethylene,

which are claimed to have therapeutic

properties. However, this issue is highly

controversial and clinical reports of adverse

periradicular tissue response would tend to

question the efficacy of these sealers. This is

especially true when these sealers are used

as the sole root canal filling material.

Subsequent to resection in roots filled with

these sealers, there is significant contact of

these sealers with the periradicular tissues,

which may resuJt in extensive tissue

destruction, with or without a root-end

filling.

Recently, calcium hydroxide

based sealers have been developed. Thus

far, evaluations of these materials have

shown mixed results regarding both physical

properties and tissue compatibility.

Initially, all sealers can cause

tissue inflammation and cellular damage.

The severity of the damage and its

continuation appears to be related to the

nature of the material, its physical

properties, its setting time, and quantity or

surface area of the material in contact with

the tissues.

Gutta-Percha

Since gutta-percha is considered to

be relatively nonresorbable and impervious

to tissue fluid dissolution, its

biocompatibility and physical adaptability to

the root canal wall must be considered. The

more effective an obturating material is in

sealing the root canal system, and

maintaining that seal, the more compatible

it is likely to be.

Composition of the gutta-percha

Chemical analysis of currently

available dental gutta-percha has revealed

the following composition:

Gutta-percha from 18.9 to 21.8%,

Zinc oxide from 56.1 to 75.3%,

Heavy metal sulfates from 1.5 to 17.3%,

Waxes and resins from 1 to 4.1%.

Properties

Semi-solid filling materials such as

gutta-percha should have high rigidity,

flexibility, and yield strength. Because of the

need to have a material which can be

readily condensed and adapted to the

irregularities of the canal system, gutta-

percha should also have a high percentage

elongation and low resilience.

Mechanically, polymers such as

gutta-percha are not perfectly elastic, but

have both elastic properties and properties

of viscous liquids. Therefore, these polymers

are referred to as viscoelastic. Clinically, the

importance of this viscoelastic property

manifests itself during use in the root canal.

Guttapercha requires a large, sustained

force of condensation over an adequate

period of time to deform plastically. The

more it deforms, the more it will flow and

adapt to the dentin wall, decreasing gaps in

the gutta-percha-dentin interface.

The quality of the root canal

treatment has a definite effect on the

marginal adaptation of gutta-percha

subsequent to resection only. However, this

result appears to also be dependent on the

type of gutta-percha, nature of the sealer

used, the condensation technique, type of

bur used for resection and operator skill.

Placement and condensation of gutta-

percha

As early as 1916 , the pulling of

the gutta-percha through the resected root-

end had been advocated to ensure

maximum adaptation to the dentin walls.

However, this technique has been shown to

result in voids in the gutta-percha – dentin

interface, as the gutta-percha tends to

retract from the walls creating significant

gaps at the interface. Most authors have

recommended coronal condensation of the

gutta-percha into the apical third of the

canal and through the foramen, prior to

removal of the excess material. This

approach would tend to ensure a better

gutta-percha-sealer adaptation to the dentin

walls.

Use of solvents

Various solvent techniques have

been advocated to enhance the adaptation

of the gutta-percha to the apical portion of

the canal prior to resection, to the root apex

if no resection is anticipated, or to the

resected root surface. Included in these

approach has been the use of eucalyptol or

chloroform and rosin to soften the gutta-

percha cone prior to placement into the

apical third of the canal or through the

resected root end, or chloroform to soften

and adapt the gutta-percha to the foraminal

margins at either the natural apex or the

resected root end. However, it has been

shown that the material loses its

dimensional stability as the solvent is

evaporated from the mixture.

Type of instrument used for adaptation of

gutta-percha

This includes burs, scalpels, spoon

excavators, plastic instruments, and

burnishers. No studies unequivocally

substantiate the best instrument for gutta-

percha removal at the apex and the quality

of the adaptation appears to be operator

dependent.

Temperature of instrument used to remove

gutta-percha

This has been a topic of

controversy for several years. For years the

use of an arm to hot instrument was

advocated to smooth or burnish the gutta-

percha filling material.

In 1980 this technique was

criticized by Tanzilli and coworkers in an

SEM study by. They compared the use of a

warm plastic instrument in a cutting or

searing motion and a cold ball burnisher to

adapt the gutta-percha at the resected root

end. Discrepancies in the adaptation of the

gutta-percha were identified under SEM

evaluation. These findings and their

subsequent interpretation, especially when

compared to cold burnished gutta-percha,

created consternation among endodontic

surgeons. This was especially true because

the cold-burnished gutta-percha appeared

to have superior adaptation to both

amalgam and gutta percha fills subsequent

to root-end resection only. The concept of

good marginal adaptation with heated

sealed gutta-percha had been challenged

and this study was cited as the bench mark

for future considerations in the management

of apically resected gutta-percha.

SILVER CONES

Silver cones have been used to

obturate root canals since the early 1930s.

However, their ability to seal the root canal

system three-dimensionally has been

justifiably challenged, as the circular,

tapered natured of the cone provides only a

central core material which is surrounded by

a sea of root canal sealer. This anatomic

problem is accelerated subsequent to

angled root-end resection, as large areas of

sealer are visible between the cone and

dentin wall. These gaps can be especially

wide in teeth with wide buccal-lingual canals

or which exhibit extensive fins or cul-de-

sacs along the facial or lingual anatomy of

the canal.

Placement of silver cone

Few reports exist in the dental

literature which address the use of a silver

cone as the apical filling material at the time

of periradicular surgery.

Contemporary studies using silver

cones at the time of root-end resection have

identified a low level of long-term success

and recommend a more bio-compatible

material.

In addition to the strong

potential for voids and leakage to exist

between a resected silver cone and dentin

wall, corrosion of the metal-worked cone

looms as a major factor for continued

periradicular tissue irritation and ultimate

failure of resected silver cone cases.

The silver content of the silver

cones range from 99.8 to 99.9%, silver salts

and sulfur sulfides formed by the contact of

the metal-worked or contaminated silver

cones have been demonstrated due to

extensive corrosion, with pitting and

cratering of the cones. However, the tissue

cytotoxicity of these corrosive silver salts

(silver chloride, silver carbonate, and silver

oxide) and sulfur sulfides has been

questioned.

The endodontic surgeon should

consider the following guidelines concerning

silver cones, root-end resection, and root-

end fills.

1) Silver cones cannot three-dimensionally

obdurate the root canal space,

especially in areas coronal to the apex

which are likely to be exposed during

resection.

2) Resection of a root end containing a

silver cone will open voids between the

cone and dentin wall.

3) Resection of a silver cone will cause the

material to be metal-worked,

accentuating its corrosive potential.

Over long periods of time, the corrosive

products that form may be highly

cytotoxic.

4) Silver cones cannot be burnished to

"perfect" the apical seal.

5) Ideally, teeth containing silver cones

and requiring surgery should be

nonsurgically retreated, if possible prior

to surgery, removing any silver

corrosion products from the root canal

system and replacing the silver cone

with a well condensed gutta-percha and

root canal sealer fill.

6) A root-end fill is indicated in all cases of

root-end resection when a silver cone is

present. When cutting a root-end

preparation into the resected root

containing a silver cone, establish a

good finger rest, use high-speed burs,

and frequently irrigate the surgical

area. Careful cutting is recommended to

prevent slipping off the silver cone and

gouging or perforating the root surface.

AMALGAM ALLOYS

One of the first reports of

placing a root-end amalgam filling

subsequent to resection is attributed to

Farrar.

Controversies and concerns

The main controversies and

concerns regarding the use of amalgam:

1) Type of amalgam (high copper versus

conventional; zinc versus nonzinc) and its

properties.

2) Leakage of amalgam root-end fills and

the use of cavity varnish, including setting

expansion and contraction;

3) Tissue compatibility;

4) Preparation and manipulation of the

amalgam;

5) Electric potentials - galvanic currents,

corrosion and degradation; and

6) Pigmentation or agyria of the

surrounding tissues.

It is essential that the endodontic

surgeon have a working knowledge of the

properties of amalgam alloys to enhance the

potential for successful treatment.

T ype of amalgam

Many of the early reports on the use

of amalgam for root-end fills did not specify

the nature of amalgam used, while some

authors specified the use of copper or silver

amalgam. At that time copper (>40% Cu)

amalgam was

identified as a tissue irritant and, as the

popularity of silver (<6% Cu) amalgam

increased, it was rapidly identified as the

root-end filling material of choice. Recently,

there has been a trend to use high copper-

content (>6% Cu) amalgams among mixed

reports of varied cellular and tissue

responses , and advanced mechanical

properties.

Root-end amalgams leak.

Key factors which interact with the

discrepancies cited include

The mean leakage observed and its

alteration with time ;

The standard deviation from the mean

leakage observed ;

The depth of the amalgam ,

The amount of amalgam corrosion and

Expansion anticipated (conventional

amalgam versus high copper amalgam;

zinc versus nonzinc);

Manipulation of the alloy during

preparation and placement ;

The placement of the alloy in the canal

prior to resection versus its use as a root-

end fill only ;

The cleanliness and seal of the root canal

system coronal to the root-end fill ; and

The use of cavity varnish

Endodontic research has identified a

significant improvement in the initial seal of

root-end amalgams when a cavity varnish is

used .The use of two coats of varnish to seal

not only the walls of the root-end

preparation but also the cut dentinal tubules

at the root surface has received substantial

support.

Material preparation and manipulation

The preparation and

manipulation of the amalgam alloy at the

time of placement is crucial in determining

amalgam strength, marginal adaptation,

degree of porosity, surface smoothness, and

the nature of surface constituents.

However, the ultimate

mechanical characteristics will be

dependent on the type of alloy chosen and

operator management. Some key points to

consider relative to alloys placed intraorally

are as follows:

1) Amalgams squeezed of their excess

mercury have a decrease in their final

strength. The Eames 1: 1 ratio technique

or that described by Jorgensen and Saito

are preferable.

2) Instructions supplied by the

manufacturer for trituration should be

closely followed. In addition,

amalgamators vary considerably in

function and performance due to warm-up

time, age, changes in line voltage, and

changes in capsule weight. Therefore, in

an attempt to minimize variations, mixes

of amalgam heavier than two spills should

be avoided, and single-speed

amalgamators or variable-speed

amalgamators of a newer design should

be used . Also, it has been noted that the

setting rate of high copper dispersed

phase alloys is more sensitive to varied

mixing speeds than spherical alloys.

3) Amalgams are more closely adapted to

the confines of the cavity during

mechanical rather than hand

condensation; however, the use of

mechanical condensers may be limited. In

addition, the condensation method has a

direct bearing on the ultimate leakage

demonstrated for both tin-mercury

containing and non tin-mercury-containing

alloys.

4) Alloys consisting of spherical, or mostly

spherical, particles are more fluid under

condensation ressures; and the use of a

large condenser in a lateral fashion may

be desirable because a small head

condenser tends to force the amalgam

mass away from the areas of

condensation. Also, less pressure is

required to properly condense these

alloys .

5) The high copper-content alloys have

been reported to be less susceptible to

the variances in operator manipulation .

6) The optimal structure for the amalgam

margins can be obtained by overfilling

and burnishing of the margins, and

removal of the excess by carving.

Burnishing of the alloy margins decreases

microporosity, improves the marginal

adaptation and seal, especially with

admixed alloys.

Carving is necessary after

burnishing, followed by burnishing to

render the surface smoother, thereby

discouraging formulation of small

corrosion cells on the surface.

The time frame for clinical

management of the alloy, including

marginal finish, may be reduced or

impaired when pressures; and the use of a

large condenser in a lateral fashion may

be desirable because a small head

condenser tends to force the amalgam

mass away from the areas of

condensation. Also, less pressure is

required to properly condense these

alloys. The high copper-content alloys

have been reported to be less susceptible

to the variances in operator manipulation .

Electric potentials - galvanic currents

The placement of a root-end amalgam

in a tooth which has a metallic post or crown

restoration could create a galvanic couple,

which has the potential to generate

significant amounts of electrical currents.

Tissue staining – argyria

The possibility of argyria

subsequent to root-end resection and/or

root-end amalgam fillings stems from

multiple sources .

1) Amalgam scattered in the surgical site.

During placement of the root-end filling.

2) Amalgam scattered in the surgical site

due to removal of a failing root-end

amalgam.

3) Fractured or loosened amalgam root-end

fills.

4) Chemical corrosion of the root-end

amalgam or silver cones at the resected

root surface.

5) Electrochemical corrosion - galvanism.

6) Silver scattered in the surgical site

during resection of roots containing silver

cones.

7) Deterioration of silver containing root

canal sealers.

During removal of previously

placed amalgams (surgical retreatrnent),

efficient irrigation and aspiration of the

surgical area are essential. Often, however,

small amounts of amalgam "dust" are

unavoidable. Fractured amalgams are often

due to lack of bulk in the thickness of the

root-end fill. Corrosion may also play a role,

as would the type of alloy and its clinical

manipulation. Loosened amalgams are due

to significant marginal corrosion, poor

placement with lack of thickness and/or

mechanical retention in the root-end, apical

resorption due to continued chronic

infIammation, and tooth fractures.

Guidelines for amalgam usage as a root-end

filling

The previous discussion on

amalgam alloys as rootend filling materials

has provided a cursory clinical and scientific

rationale for considering the use of this

material. Although amalgam is not the ideal

material, the endodontic surgeon should

be cognizant of the following concepts

when choosing amalgam as the root-end

filling material.

1. Control of moisture in the surgical site is

essential.

2. High copper alloys are the material of

choice at present.

3. Varnish must be used prior to alloy

placement. Dentin bonding agents can also

be considered in place of varnish.

4. Zinc alloys are the material of choice

when moisture is controlled.

5. When moisture cannot be controlled,

nonzinc alloys should be considered.

6. Carefully condense, burnish, carve, and

burnish the alloy using a minimal number

of firm strokes directed to the alloy dentin

interface

7. Create a smooth surface on the finished

alloy.

8. Prevent the dispersion of alloy particles

in the surgical site.

9. Keep the alloy as small as possible in

perimeter or diameter, although the bulk

of the alloy must be thick enough to resist

fracture and to obturate the entire canal

system at the resected root surface.

10. Radiographically, the amalgam will often

resemble the shape of both the canal

system and the external root anatomy.

ZINC OXIDE-EUGENOL

The mixture of clove oil, which is

eugenol in its unrefined state, and zinc

oxide to form a plastic mass was first

described by Chisolm during the Tennessee

State Dental Meeting (in 1873). Its use in

dentistry expanded rapidly to many areas,

including endodontics, periodontics, and

restorative dentistry.

Zinc oxide-eugenol (ZOE) has been

shown to prevent bacterial ingress along

cavity margins. It has also been shown to be

an irritant, primarily due to the eugenol

component. However, even the tissue

response to eugenol is varied and is

dependent on the short-term saturation of

the local environment with eugenol , at a

concentration level and time sufficient to

harm mammalian cells. The level of toxicity

incurred is due to the concentration of

eugenol released from the material and is

not always proportional to the content of the

source, or consistent within specific

preparations. Ultimately the extent of cell

death which occurs depends principally on

the efficiency of local clearance of eugenol.

At the root apex, local blood

flow and clearance are usually sufficient to

allow for healing. If the contact area at the

root apex of ZOE is minimal, then cell death

may-be minimal and, with the rate of

eugenol release declining over 1 to 2 weeks,

healing should occur. However, there is

ample evidence to show osseous tissue

toxicity to ZOE. The use of ZOE as a root-

end sealing agent in periradicular surgery

has had limited documention.

When ZOE is in contact with

water, it is hydrolyzed, breaking the CH3-O-

Zn coordinate bond to produce zinc

hydroxide and eugenol. The eugenol will

continue to be removed by the leaching of

water until all the original zinc eugenolate is

converted into zinc hydroxide. This

hydrolysis forms the basis for the

bioavailability of free eugenol and ultimately

determines whether the agent is therapeutic

or toxic. Depending on its concentration,

eugenol can:

- Competitively inhibit prostaglandin

synthetase by preventing the

biosynthesis of cyclo-oxygenase,

- Inhibit senory nerve activity,

- Reversibly inhibit repair in mammalian

cells,

- Kill cells with prolonged exposure,

- Kill a range of oral microorganisms

- be an allergen.

Also in this process of dissolution,

zinc has been identified leaching into the

dentinal tubules. Since it has been shown

that zinc, in low concentrations, may act as

a regulator ion in the process of

mineralization and wound healing, there

may be a beneficial effect to placement of a

ZOE root-end fill. However, extensive and

controlled evaluations of these concepts

within the parameters of periradicular

surgery are warranted.

Newer modifications of ZOE

compounds, such as IRM (LD Caulk Co.),

have also been evaluated as to their sealing

ability. Studies reveal that IRM sealed better

than nonzinc amalgam using

electrochemical longitudinal analysis (60

days) and dyes, and zinc amalgam using

pulp tissue response. At the same time, it

has been shown to allow leakage to a

bacterial species. Therefore,

additional evaluative parameters and

studies

are indicated.

In an attempt to alter the

setting time and increase the strength of

ZOE cements, the EBA (o-ethoxybenzoic

acid) cements were developed. EBA

cements have been shown to have much

better physica! properties than ZOE, with

compressive, tensile, and shear strengths

approaching those of zinc phosphate

cements, especially with the addition of

reinforcing fillers such as aluminum oxide,

silica, hydrogenated resin, and acrylic

resins. However, cement solubility was

increased with the addition of these

modifiers.

Further advances in the

formulation of EBA cements led to the

development of Stailine Super EBA cement

(Staines, UK) which consists of 60% zinc

oxide, 34% silicone dioxide, and 6% natural

resin

in powder form, which is mixed with eugenol

in a 62.5% : 37.5% ratio respectively. This

product has high compressive strength, high

tensional strength, neutral pH, and low

solubility. Even in moist conditions, this EBA

adheres to tooth structure. The use of EBA

cements to enhance root canal filling

materials has thus been recommended.

Studies conducted to evaluate the

biological aspect of this new modification

showed a good healing response to Super

EBA with minimal chronic inflammation at

the root apex. Scanning electron microscope

evaluation showed excellent material

adaptation to the dentin margins at the

resected root surface. Collagen fibers were

deposited on top of the Super EBA with

possible fiber ingrowth into the material.

Additional tissue compatibility

studies of EBA cements have confirmed

their low level of irritation, especially in the

set state. Leakage studies with EBA cements

have shown good adaptation and marginal

sealing.

Based on the various studies, the

prospects for future routine use of EBA

cements are promising.

CAVIT Cavit is a temporary filling

material which contains

zinc oxide,

calcium sulfate,

zinc sulfate,

Glycol acetate,

polyvinyl acetate,

polyvinyl chloride acetate,

triethanolamine, and

red pigment.

It is also available in forms without

the red pigment, such as Cavit-G and

Cavit-W. Cavit is soft when placed in the

tooth and subsequently undergoes a

hygroscopic set after permeation with

water, giving it a high linear expansion

(18%). This property has been cited as a

rationale for its use as a root-end filling

material.

The ability of Cavit to seal

cavities is controversial. Biocompatibility

studies with Cavit are in conflict, showing it

to be both toxic and nontoxic, which

emphasizes potential problems with

comparing diverse experimental conditions.

Tissue toxicity studies have shown that

Cavit is toxic to subcutaneous tissue and

bone. Longterm

radiographic and clinical evaluations of the

use of Cavit as a root-end filling material are

varied. Further studies or alteration in the

compound to enhance its tissue

biocompatibility and sealability are

warranted, if Cavit is to be considered as a

viable material to seal the root system.

POLYCARBOXYLATE CEMENTS

This group of dental cements

was introduced by Smith in the late

1960s.The zinc polycarboxylate cements

consist of

a powder - modified zinc oxide with fillers

such as magnesium oxide and stannous

fluoride) and

a liquid (aqueous solution of polyacrylic

acid)

When mixed this mass hardened,

and forms a cement of zinc oxide particles

dispersed in a crosslinked structureless

matrix of zinc polycarboxylate. This reaction

occurs between the zinc ions and the

carboxyl groups on the polyacrylic acid, with

the free carboxyl groups having the capacity

to chelate calcium. Therefore, adhesion to

tooth structure is a significant physical

property of the polycarboxylate.

Their solubility is similar to

that of zinc phosphate, provided the proper

powder-liquid ratio is used. Reducing the

powder content by a third has been shown

to amount to a threefold increase in cement

disintegration.

The pH of the cement is

approximately 1.7. However, the liquid is

rapidly neutralized by the powder during

material set. Despite the initial acidic nature

of the polycarboxylates, minimal irritation

has been reported to the dental pulp when

placed on adjacent dentin or used as a

direct pulp cap.

However, the osseous tissue

adjacent to the polycarboxylate implants

showed decalcification, which is probably

due to the chelating property of the cement.

If this were to occur to the dentin walls in a

root-end preparation filled with a

polycarboxylate, the possibility for leakage

might be enhanced at the cement-dentin

interface. This aspect of the cement requires

further evaluation. Polycarboxylates placed

in root canal systems or beyond the

confines of the root apex show a varied

periradicular tissue response.

Studies conducted when used as

root-end fillings, leak at levels significantly

greater than amalgam or gutta-percha.

Therefore, based on their poor sealing

ability and uncertain periradicular tissue

response,

the use of polycarboxylates as root-end

filling materials is highly questionable.

Further evaluation may be warranted.

COMPOSITE RESINS Composite resins have received

minimal attention as root-end filling

materials. This is due to their cytotoxic or

irritating effects on pulp tissue. To reduce

their irritation in the tooth, bases or liners

are recommended. As a root-end filling this

would be impossible with composites. In

addition, the release of formaldehydes from

composites has been identified and long-

term tissue irritation may be a factor when

placed in the rootend.

Recent evaluations have

challenged the cytotoxicity of composites

claiming the need for better material

adherence to dentin to eliminate marginal

leakage and the primary cause of their

claimed cytotoxicity, bacteria and their

products.

Good marginal adaptation was

observed with composite, while amalgam,

whether carved or burnished, consistently

exhibited marginal gaps.

Cell attachment to the surface of the

composite was remarkably less than that of

amalgam. In addition, cell attachment to the

root dentin was highly variable. Overall

composites exhibited a poorer

biocompatibility than amalgams.

Initial leakage studies with

composite resins as a root-end filling

materials have been favorable, with leakage

patterns less and marginal adaptation better

than amalgam, Cavit, polycarboxylate,

gutta-percha, and zinc phosphate. However,

when placed against clinically moist dentin,

composite materials do not produce seals

immediately after insertion and the final

adaptation is a function of polymerization

shrinkage and water sorption.

Due to the possibility for initial

leakage with all restorative materials,

various approaches to enhance marginal

adaptation and sealability have been

recommended.

Acid etchants and dentin bonding agents

have now improved levels of material

adaptation, prevention of bacterial

penetration, and decreased marginal

leakage with amalgam and composite.

ZINC PHOSPHATE CEMENTS Rhein, in 1897, used zinc

phosphate cement along with gutta-percha

to seal the root canal system prior to root-

end resection. In 1916 Provan

recommended the use of oxyphosphate of

copper to seal the canals of molar teeth

which had been resected.

Presently, few, if any, references

are

made in the current literature to the use of

zinc phosphate cements for root-end filling

materials for the following reasons:

1) They are soluble, especially in dilute

organic acids. This would be a significant

problem in rootend fills, particularly with the

presence of chronic inflammation in the

periradicular tissues.

2) They are irritating to tissues, especially in

the

presence of bacteria. However, many

studies

have provided varied and opposing findings

in this regard.

3) The cements are prone to leakage and

are affected by moisture during placement.

GOLD FOILFor years gold foil was acknowledged as the

premier restorative material. Some of the

first reports on its use as a root-end filling

material are attributed to Schuster in 1913

and Lyons in 1920. Reports in the 1960s,

1970S, and 1980s continued to recommend

its use because of ease of direct

manipulation, marginal adaptation, surface

smoothness, and tissue biocompatibility.

Cytotoxicity studies have indicated

variations in the inhibition of cell growth

based on the formulation of the gold. Fine

pellet gold did not inhibit cell growth,

whereas newer formulations (New Biofil and

Karat) inhibited up to 80% of the cellular

growth. Tissue biocompatibility studies have

indicated a mild response to

undercondensed, irregular pieces of gold

foil.

Marginal adaptation and

leakage studies in root-end preparations

have indicated minimal or no leakage. Key

to the claimed success in the use of gold foil

was the close adaptation to the dentinal

walls and the ability to highly polish the

metal filling.

Although it possesses favorable

material properties, the routine use of gold

foil as a root-end filling material does not

appear practical because of the need to

establish a moisture free environment, the

need for careful placement and finishing,

the possibility

of root fracture under excessive

condensation

pressures, and the need for surgeon

expertise in material management.

However, its use in isolated cases may be

justified, especially when a long cast gold

metal post is present in the root, or access

to the surgical site can be carefully

controlled.

GLASS IONOMERS Glass ionomers are a hybrid of

the silicate and polycarboxylate cements,

which bond physicochemically to dentin and

enamel, and possess anticariogenic activity.

They are formed by the reaction of calcium-

alumino silicate glass particles with aqueous

solutions of polyacrylic acid. The acid

extracts calcium and aluminum ions from

the glass

particles, initiating a prolonged two-phase

setting reaction. Calcium ions bind. to the

polyacrylic acid producing a firm gel that

provides initial adhesion to tooth structure.

The final set material consists of

unreacted glass particles coated with silica

gel embedded in a matrix of calcium

aluminum polysalts. During the initial

setting period the surface of glass ionomers

is highly sensitive to acidic environments

(4.8 pH) with the elution of AI, F, Si, and Ca

ionic species. With longer aging, less

dissolution of ions is observed. However, in

the periradicular environment the glass

ionomer would be immediately exposed to

inflammatory products during its primary

setting reaction, which may result in

significant ionic release.

Glass ionomers have been shown

to have antibacterial properties, due to their

acidity and fluoride release. Marginal

adaptation and adhesion of glass ionomer

cements to dentin have been shown to be

improved with the use of acid conditioners

and varnishes.

Although these properties would

enhance the use of glass ionomers as root-

end filling materials, their sensitivity to

moisture contamination would tend to

restrict their

use to cases in which thorough root-end

isolation is achieved.

MISCELLANEOUS ROOT-END FILLING MATERIALS

The following list of materials has

received brief mention in the dental

literature for use as root-end filling materials

in periradicular surgery. Little substantiation

exists for the use of some of these

materials,

while others require further evaluation to

determine the long-term efficacy of their

use. The endodontic surgeon should

consider using materials which have been

biologically and clinically evaluated and

which give evidence for favorable longterm

success.

1) Lead points, cited by Lyons, to seal the

canal followed by burnishing to seal the root

apex after resection.

2) Gold screws .

3) Ward's Wonderpack cement.

4) Poly-Hema, which was shown to leak to

bacterial products over short-term

evaluation.

5) Tin foil

6) Ivory and plastics.

7) Powdered dentin mixed with sulfathiazole

8) Rickert's root canal sealer

9) Titanium posts; titanium screws

10) Silver posts

11) Tin posts

12) Aluminum-oxide ceramic posts for both

apical seal and increased root length

subsequent to resection.

13) Resorcine-formalin resin (Foredent).

14) Diaket, a polyvinyl resin, used as a root

canal sealer, has been empirically

mentioned by clinicians for use as a root-

end filling. However, this material has been

shown to produce long-term chronic

inflammation in osseous tissue and

subcutaneous tissue ,and to be cytotoxic in

cell culture. On the other hand, it has been

that it was tolerated by tissues, was

impervious to methylene blue

penetration, and did not dissolve or absorb

in the presence of periradicular tissues and

fluids.

The Diaket is mixed to a thicker consistency

than when normally used as a sealer, and is

condensed into small voids identified in the

root canal fill at the resected root surface.

Leakage studies comparing Diaket with

nonzinc alloy and glass ionomers have

shown Diaket to display superior sealing

qualities.

15) Biobond, and EDH-adhesive, originally

used for the prevention of intracranial

aneurysm and reinforcement of vessel walls,

has been evaluated by Nordenram for use

as a root-end filling material. Clinical and

radiographic evaluation showed results

comparable to root-end resection only, and

only slightly better than teeth with root-end

gutta-percha fills.

16) Root-end capping with a metallic

retentive pin (Remanit G - metallic

properties of vitallium) - A thin metal cap

with a vertical loop (similar to an umbrella)

is cemented into the prepared apex.

Chloropercha NO is applied between the cap

and the cut surface. The perimeter of the

cap would encompass the entire resected

root face and be flush with the cemental

wall. Not only would the root canal system

be sealed with this technique, but also the

cut dentin tubules.

17) Cyano acrylate - Because of bonding

properties and soft tissue compatibility,

cyanoacrylate was evaluated as a root-end

filling material. Studies on extractedteeth

indicated that cyanoacrylate leaked less

than amalgam with or without varnish and

hot or cold-burnished gutta-percha foot-end

fills. Adverse tissue response to

cyanoacrylatehas been demonstrated as

compared to amalgam and composites with

bonding agents. However controversies over

the ultimate biocompatibility of

cyanoacrylates have minimized its extensive

and aggressive use in dental procedures.

18) Radiopaque bone cements, which are

polymethacrylate based and contain an

antibiotic (gentamicin sulphate) have been

recommended for rootend filling.Evaluation

has shown the cements to have distinct

bacteriocidal properties and to exhibit

favorable compatibility in tissue cultures,

compared to amalgam. However, when

placed in the root end, the sealability of

these cements was less than that of

amalgam.

Bibliography

1) Endodontics – Ingle, Drakeland

2) Endodontic Surgery - Gutman

3) Textbook of Endodontic - Weine

Contents

1) Introduction

2) Ideal requirements of retrograde

filling materials

3) Materials – Properties and

Manipulation