GIC_SEM_ / orthodontic courses by Indian dental academy

GLASS IONOMER CEMENTS**********************************************

INTRODUCTION

HISTORY

CLASSIFICATION

DEFINITION

COMPOSITION

SETTING REACTION

PROPERTIES

CLINICAL PROCEDURES

DISPENSING AND MIXING

FINISHING AND POLISHING

CLINICAL USES

CONCLUSION

Introduction:

“Necessity is the mother of invention”

It was the late 1960’s. History had already witnessed a host of restorative materials

including amalgam, composite, cast alloys etc. but all had fallen short of that certain

perfection that the dental researches and clinician yearned for…..that of a material

that would be esthetic, adhesive, biocompatible, anticariogenic and relatively

economical. It was during this time that a cement came into the picture and created

quite a sensation by not only possessing a majority of the desirable properties but also

providing much scope for modification and improvement. This was the Glass Ionomer

Cement.

HistoryThe study of this versatile material would be incomplete without exploring a little bit

into its past to appreciate the GIC as we know today. The history of tooth coloured

restorative material began with the introduction of silicate cement by T. Fletcher

(1871). Unfortunately, it gradually lost its popularity due to its high degree of acidity

and solubility

It was in 1951 that a certain Swiss chemist, Dr. Oscar Hagger, first demonstrated the

adhesion of a resin to the tooth which was appropriately capitalized on by Buonocare

in 1955 to define the principles of the acid- etch technique to be later utilized by

Bowen in 1958 to develop the composite restoration. Thus, the concept of adhesion

to the tooth was finally a reality.

The first major break through in the concept of dentin adhesive via ion exchange was

made by D.C smith who developed the “ polycarboxylate cement” using polyacrylic

acid and ZnO

In 1969, B. E. Kent discovered a high fluoride containing glass leading to the

invention of the 1st ancestor of GIC - the ASPA I. This was not free from its share of

problems which included

- Sluggish set

- Minimal working time

- Low degree of opacity

In 1972, ASPA II was concocted using tartaric acid in the previous formulation.

This enhanced :

- WT

- Manipulation

- Setting rate

This was the 1st practical GIC.

In 1974 Wilson and Crisp tried to control the gelation of PAA by adding methyl

alcohol and came up with ASPA III but this formulation tended to stain.

So, in 1975, both of them discovered ASPA IV which contained co –polymers of

acrylic and itaconic acid. This formulation did not gel. ASPA IV is the precursorof

the modern GIC.

A fine grained version for luting was developed in 1977 so was a highly translucent

version called ASPA X by Crisp, Abel & Wilson.

In 1984, Prosser developed the first anhydrous GIC called ASPA V. This contained

PAA in a dry powder form blended with glass powder, which was then mixed with

water or tartaric acid. Advantage included:

- Sufficient mixing qualities

- Higher strength

In 1985, Mc Lean and Gasser developed the “Ceremet” ionomer cement by fusing

silver particles to the glass particles for better burnishability

Most of the later developments was done by individual dental material companies. A

whole new spectrum of GIC’s ranging from a conventional GIC at one end to a

modified composite at the other side is now available . Newer and newer varieties are

coming into the market and awaiting clinical trials.

Classification I. According to Philips:

Type I – LutingType II – Restorative Type III – Liner and base

II. According to Davidson and Mjor:

1. Conventional/ Traditional

a. Glass Ionomer for direct restorations b. Metal reinforced GICc. High viscosity GICd. Low viscosity GICe. Base/Linerf. Luting

2. Resin modified GIC

a. Restorativeb. Base/Linerc. Pit & fissure sealantd. Luting e. Orthodontic cementation material

3. Polyacid modified resin Composites/Compomers

III According to GJ Mount:

1. Glass ionomer cements:

a. (i) Glass Polyalkeonates(ii) Glass polyphosphonates

b. Rein modified GICc. Polyacid modified composite resin

2. a. Auto-cure

b. Dual Cure

d. Tri cure

3. a. Type I – Luting

b. Type II – Restorative

Type II.1. Restorative aesthetic

Type II.2. Restorative reinforced

c. Type III – Lining or Base

IV According to Sturdvent:

1. Traditional or conventional

2. Metal modified GIC

a. Ceremets b. Miracle Mix

3. Light cured GIC4. Hybrid (Resin modified GIC)5. Polyacid modified resin composites or Compomer

V. According to Wilson & McLean (1998)

1. Type I Luting2. Type II

a. Aesthetic filling material b. Bis-reinforced filling material (includes ceremets)

3. Type III – Lining, base and fissure sealant

VI: Based on chemical constituents of cement:

1. Conventional 2. Metal reinforced

a. Miracle mixb. Ceremets

3. Resin modified

VII. According to intended applications:

1. Type I - Luting

2. Type II - Restorative

3. Type III - Fast setting lining

4. Type IV - Fissure sealants

5. Type V - Orthodontic cements

6. Type VI - Core build up material

7. Type VII - High fluoride releasing command set GIC

8. Type VIII - GIC for Atraumatic Restorative Treatment (ART)

9. Type IX - Geriatric and Paediatric GIC

VIII. According to McLean, Nicholson & Wilson (1994):

1. Glass Ionomer cement

a. Glass polyalkeonates b. Glass Polyphosphonates

2. Resin modified GIC3. Polyacid modified GIC

Conventional GIC

Definition: Glass ionomer is a combination of ‘Glass’powder and ‘ionomer’-ic acid

GIC can be defined as a water- based material that hardens following an acid-base

reaction between the basic fluoro aluminosilicate glass powder and an acidic solution

of polyacrylic acid.

Composition

Powder = Is basically an acid soluble calcium aluminosilicate glass containing

fluoride. It is formed by fusing silica + alumina + calcium fluorite, metal oxides and

metal phosphates at 11000-15000 C and then pouring the melt onto a metal plate / into

water. The glass formed is crushed, milled and ground to a form powder of 20 – 50

size depending on what it’s going to be used for. They get decomposed by acids due

to the presence Al +3 ions which can easily enter the silica network. It this property

that enables cement formation.

Functions of components:

Alumina (Al2 O3)

- Skeletal structure

- Increase opacity

Silica (SiO2)

- Skeletal structure

- Increase Translucency

Fluoride: Its has 5 functions

- Decrease fusion tO

- Anticariogenecity

- Increase translucency

- Increase working time

- Increase strength

Calcium fluoride (Ca F2)

- Increase opacity

- Acts as flux

Aluminium phosphates

- Decrease melting to

- Increase translucency

Cryolite (Na3 Al F6)

- Increase translucency

- Acts as flux

Na+, K+, Ca+2, Sr+3

- Include high reactivity of glass with polyacid.

Al2 O3 : SiO2 ratio is crucial and should be > 1:2 for cement formation to occur.

Cement formation will occur only when there will there be sufficient replacement of

Si by Al to render the network susceptible to acid attack.

The glass can be modified by several ways to enhance the physical properties of the

cement.

1. Ca can be replaced by Sr, Ba or La to give a R/O glass

2. Washing glasses with organic acids to remove surface concentration of Ca

which will help prolong WT

3. Corundum, Rutile, Baddelyte disperse phases can be added to increase flexural

strength

4. Metals, resins, fibers are added to increase the strength.

Liquid: Originally, the liquid for GIC was an aqueous solution of PAA in a

concentration of about 50%. This was quite viscous and tended to gel over time.

Thus, PAA was co- polymerized with other acids such as itaconic, maleic and

tricarboxylic acids. This polyelectrolytic liquid of GIC is, thus, also called as

polyalkenoic acids. Recently polyvinyl phosphoric acid has also been introduced to

this system.

A typical liquid of GIC contains 40-55% of 2:1 polyacrylic : itaconic acid co-

polymer and water.

The basic functions of these co–polymers include:

- the co- polymeric acids are more irregularly arranged than the homo polymer.

This reduces H- bonding between acid molecules and reduces degree of gelling

- decrease the viscosity

- reduce tendency for gelation,hence, improves storage.

- Increase the reactivity of liquid

The rest of the liquid comprises of water, which is an important constituent of GIC. It

is the reaction medium and helps in hydrating the matrix.

Additives:

1.Tartaric acid

- Increases WT

- Increases translucency

- Improves manipubality

- Increases strength

5-15% of optically active isomer of TA is added.

2.Polyphosphates: extends WT

3.Metal oxides: accelerates ST

The reactivity of the polyacid depends on:

- ingredients= malec acid is a more reactive acid than PAA

- Mol .wt and concentration= increase reactivity

There are some other effects of these co-polymers:

- decrease adhesion. According to Aboush & Jenkins (1986) cements based on

co –polymer bond less strongly than those based on PAA

- decrease resistant to acid attack: Setchell & co(1985)

Note: To extend WT, PAA can be freeze dried/ vacuum dried and incorporated with

the glass powder. The liquid here is either water or an aqueous solution of tartaric

acid. When mixed, the acid dissolves to reconstitute the liquid acid and the reaction

proceeds in the normal manner. These cements have a relatively low density and are

particularly suitable for luting and as liners. These GIC are termed water settable

GIC’s or erroneously as anhydrous GIC’s .

SETTING REACTION:An understanding of the setting reaction is needed to appreciate the scientific

technology of GIC and their correct clinical usage.

The setting reaction can be described in several stages.

1. De-composition:

When the P and L are mixed, the surface of the GI particles are attacked by the

H+ ion of the acid. This results in decomposition of the about 20-30% of the glass and

the leaching of Ca+2, Al+3, Na+, F- ions into the aqueous medium.

2. Migration:

Acid attack occurs preferentially at Ca-rich sites and these metal ions migrate

into the aqueous phase of the cement towards the PAA chains.

3. Gelation:

Polyacrylic acid chain entanglement, ionic bonds and H-bonding are all

involved in matrix formation. Chains get initially cross linked with the more

readily available Ca ions leading to precipitation of calcium polyacrylate and

gelation. A clinically ‘hard’ surface forms within 4-10mins from start of

mixing. This initial clinical set is achieved by Ca +2 ions.

4. Post Set Hardening:

Occurs when the less mobile Al+3 ions become increasingly bound to the

polyacid and precipitate as the more rigid aluminium polyacrylate.

5.Further maturation:

Occurs over the next 24 hrs as the cement develops resistance to desiccation

and acid attack. The cross linked phase gets hydrated in this stage which

causes improved physical properties.

The Na+ ion contributes to the formation of orthosilicic acid on the

surface of the particles. As the pH rises this converts to a silica gel around the

un- reacted glass particles which aids in binding the powder to the matrix.

Na+ and F ions do not participate in the cross-linking. Na+ ion may replace

H+ ion of the carboxylic group while the rest combine with F ion to form Na

F. F ions lie free within the matrix and are able to move in and out of the

cement.

Thus, the cement structure can be described as an agglomeration of un-reacted

powder particles surrounded by a silica gel in an amorphous matrix of hydrated

Ca and Al polysalts

Role of Water: GIC’s are water based cements and water plays an important role in

their setting and structure. Its functions include:

It is the cement forming medium into which cations are leached and get

carried towards the PAA chains.

It serves to hydrate the silica gel and metal salts & causes increase in strength

It is an essential part of the cement structure and if lost while setting, the

cement forming reaction will stop.

Water present in the set cement can be arbitrarily classified as:

- loosely bound water which can get readily removed by dessication. This is

associated with Ca+2 during the initial reaction

- tightly bound water is the one which hydrates the matrix as setting continuous and

cannot be removed by dessication. This is associated with Al+3 and is critical in

yielding a stable gel structure and building the strength of the cement.

Protection: Water is easily gained and lost by the cement. Dessication can cause

crazing and cracks on the surface. Any water contamination at this stage leads to

dissolution of the matrix formers resulting in weak and soluble cement. Early contact

with water causes hygroscopic expansion, disruption of cement surface and surface

roughness.

So, protect GIC from the 2 extremes -dessication and aqueous fluids- using

suitable barriers like vaseline, DBA etc.

Factors effecting setting:

1. Chemical Constituents:

a) Alumina: Silica ratio = If higher the ratio, faster the set

b) F= delays gelation and prolongs WT

c) Tartaric acid= Faster the set.

2. Particle Size= Finer the powder faster the set and shorter the WT

3. P: L = More the P: L -faster the set

4. t0 of mixing = More t0 -faster the set

Properties of GIC

GIC show a variety of properties and are clearly very diverse materials

ADHESION:

GIC have the important property of adhering to untreated E and D. It adheres to the

smear layer on cut D and also to reactive polar substrates like base metals. Bonding

being chemical, bond strength develops in the first 15 mins of placement

Adhesion of GIC helps in:

- Providing a conservative approach to restorations

- Providing a perfect seal

Various speculation have been made on the mechanism of adhesion

1. Smith (1968): Suggested the chelating of calcium ions of the HA with the

carboxyl group of the PAA.

2. Beech (1973): said that interaction between the HA and PAA produced poly

acrylate ions which formed strong ionic bonds with surface Ca+2 ions of E and

D

3. Wilson (1974): Postulated that wetting and initial adhesion is by H-bonding

provided by free carboxyl groups. As the cement ages, the H-bond is replaced

by ionic bonds.

4. Wilson, Prosser and Powis (1983):According to them, PAA enters molecular

surface of the HA and displaces the Ca+2 and PO-3 ions leading to the

formation an intermediate layer of Ca and Al phosphates and polyacrylates at

the interface between the cement and HA.

5. Akinmade and Nicholson (1993) termed the above theory ‘diffusion based

adhesion’ system

While there is general agreement that bonding to enamel results from ionic and polar

forces, opinions differ on bonding with dentin. Beech (1973) and Jackson (1986) said

that bonding to dentin occurred to its HA part with no collagen involvement but a

study by Akinmade (1994) revealed that a degree of adhesion to collagen of dentin via

H-bonding between carboxyl groups and collagen molecule did occur.

Adhesion to enamel is better than to dentin due to the high inorganic content and

greater homogeneous nature of enamel. Bond strength to enamel is 26-96 MPa while

that to dentin is 11-4.5 MPa. If a restoration fails, the failure is usually cohesive

within the cement rather than adhesive at the interface.

Adhesion can be improved by usage of surface conditioners, which helps to

eliminate the wide variation found after cutting. Better wetting and interfacial contact

will occur if a smooth surface is attained. Conditioners help to:

- Remove the smear layer

- Increase surface energy of tooth

- Increase wettability and therefore decrease contact angle.

Different Conditioners used are :

1. PAA : Is the conditioner of choice as it is a part of the cement forming acid. It

alters the surface energy, exposing highly mineralized tooth surface to

diffusion of acid and ion exchange. This enhances adaptation of cement (10%,

10sec)

2. 50% citric acid, 5 sec

3. 25% tannic acid, 30 s

4. 2% Ferric chloride

5. NaF

6. EDTA

7. Mineralising solution –ITS solution, Levine solution

BIOCOMPATIBILITY:

Adverse affect of GIC on living tissues are minimal. Any inflammatory response of

pulp towards GIC due to its high initial pH of 0.9 to 1.6 resolves within 20-30 days.

No ill effects are caused by PAA because:

- PAA is a weak acid, which becomes weaker when partly neutralized

- Its diffusion into the tubular dentin is unlikely due to its high molecular weight

and heavy chain entanglement

- It gets readily precipitated by the calcium ions in the tubules.

- Dissociated H+ ions remain near the chain due to electrostatic attraction

The occasional post insertions sensitivity encountered on luting full crowns is due to

- The high initial pH {2.33 (PAA) liquid and 1.76 (water settable)}which

persists for about 5 mins.

- Lower P: L ratio

- Pre-existing pulpitis

- Minimal D thickness to prevent this, certain precautions should be taken.

- Don’t remove smear layer

- Protect deep areas of cavities with Ca (OH)2

- Apply DBA before crown insertion.

ANTICARIOGENECITY:

GIC has the unique property of being cariostatic due to the sustained release of

fluoride, which confers resistance to caries not only on the restored tooth but also on

the adjacent tooth. The influence of fluoride is found in a zone of resistance to

demineralization, which is at least 3mm thick around a GIC restoration (Kidd, Hicks,

Hotz).

Fluoride contributes to carious inhibition in the oral environment by means of both

- Physicochemical mechanism

- Biologic mechanism

Physiochemical:

The F ions become incorporated in the HA crystals to form “fluorapatite”

which is resistant to acid mediated decalcification.

The ions decrease the surface energy of the apatite making it difficult for

plaque to adhere.

The ionic fluoride shifts the equilibrium towards re-mineralization. F acts as a

catalyst for uptake of Ca and PO4 ions. Carious enamel being more porous,

allows greater penetration of F and thus more uptake of Ca and PO4 occurs

leading to formation of acid resistant crystals and the lesions treated with

fluoride are more acid resistant than intact E

Biologic:

F inhibits carbohydrate metabolism by acidogenic plaque flora leading to

decreased acidogenecity

It alters the production of extra-cellular, insoluble polysaccharide which helps

in forming adhesins of bacteria and thus inhibit adhesion.

It also alters the acid tolerance of S. mutans to produce a less acidogenic

plaque flora.

In higher concentration, F is bactericidal to sensitive bacterial populations

Two principal concerns regarding efficacy of fluoride addition to the restorative

material

- What is the amount and longevity of F release?

- As it gets released, will material properties get degraded?

F release is diffusion limited and affected by concentrations in both matrix and

particles. The initial high burst of F release is due to high concentration of F that

exists in the matrix immediately after setting when the acid dissolves the powder

particle edges. In the next 3 months, decline in the release occur when F from greater

distance in the matrix away from the surface get slowly released. A slow diffusion

follows when F from the particles get released at a much slower rate. This may occur

for many years. A topical F application will increase the release for a short term. A

GIC can thus be regarded a fluoride reservoir.

The second concern was regarding degradation of material properties. Fluoride and its

salt NaF are both not matrix forming species and thus the cement is not weakened by

the loss of F.

AESTHETICS:

A degree of translucency exists for GIC due to the glass fillers. Its

translucency depends on its formation. It is important to note that because of slow

hydration reactions, Glass ionomer takes at least 24hrs to fully mature and develop

translucency. Translucency increases as the cement ages. Resistance to stain is largely

dependent on obtaining a good surface finish. The colour seems to be unaffected by

oral fluids as compared to composites which tend to stain.

DIMENSIONAL STABILITY:A correctly manipulated and protected GIC shows a volumetric setting contraction of

~ 3%. At higher humidities, the cement tends to absorb water and expand so much so

that a net expansion occurs while at lower humidities, a low shrinkage occur.

DISSOLUTION AND DISINTEGRATION:The loss of soluble matrix forming species from the cement can lead to disintegration

of the cement. This can be caused by:

- Early water contamination

- Chemical attack such as plaque acids / APF gel application

- Mechanical wear

It is mandatory to protect the GIC in its first ½ hour of life. A solubility of only 0.4%

(wt) is seen as compared to other cements

DURABILITY AND LONGEVITY:According to one study, the GIC restoration evaluated in erosion-abrasion lesions,

83% showed retention even after 10yrs. Failure rate ranges from 0-70%, which is

more of a measure of the clinicians skill than of the inherent quality of the material

STRENGTH:

One of the major limitations of GIC is their susceptibility to brittle fracture. As

compared to composite and amalgam, GIC’s are weak and lack rigidity. The

weakness appears to be in the matrix, which is prone to crack propagation. A certain

degree of porosity also develops as it is a 2 part material, which needs to be mixed

prior to placement

RADIOPACITY:

GIC are fairly R/O due to inclusion of radio opacifies like BaSO4. Most GIC’s are

slightly more radiopaque than dentin and can be differentiated in radiograph.

Clinical Procedure:To ensure the successful use of GIC, 3 parameters to be controlled include

- Conditioning of tooth surface

- Proper manipulation

- Protection of cement during setting

Procedure:

Select the appropriate shade

Isolate tooth with cotton rolls or rubber dam if there is a chance

of gingival seepage / bleeding

Prepare the cavity

For erosion / abrasion: slight roughning / cleaning with pumice

slurry

Carious lesion excavation via conventional instrumentation

If M.D.T is < 0.5mm, line the cavity with Ca(OH)2 liner

Apply surface conditioner to improve adhesion.

Wash thoroughly with water for 30s

Dispense the cement on a cooled glass slab/ paper pad and

quickly incorporate into liquid and mix by folding technique in

45-60 secs. with agate spatula. In higher humidities the glass

slab should not be cooled as this causes condensation and

incorporation of water into the mix. The proper P:L ratio

should be followed

A glossy mix should be attained as this indicates the presence of poly acid,

which will take part in adhesion

The surface should be dried but not desiccated

The cement is placed and a pre-contoured matrix is placed to provide:

o Contour

o Ensure surface integrity

o Protect setting cement

Allow the cement to set (4mins)

Remove the matrix and immediately apply varnish / BA. This is the most

critical step.

Trim excess external to cavity with scalpel blade. Don’t use rotary instruments

as it causes ditching

Reapply varnish

Final polishing delayed for at least 24 hrs

Dispensing and Mixing:GIC’s are available in 2 forms

- P and L separately in 2 forms

- Encapsulated for mechanical mixing

Advantages of capsule (OHP)

Finishing and polishing:The best surface obtained is when cement sets against a matrix

Clinical uses: Luting cements (TYPE 1)The ideal properties of a luting cement according to Mc Lean and Wilson are :

Low viscosity and film thickness

Long working time and rapid set at mouth temperature

Good resistance to aqueous acid attack

High compression and tensile strength

Resistance to plastic

Adhesion to tooth structure

Cariostatic properties

Biological compatibility with the pulp

Translucency

Radiopacity

The first commercial water hardening cement was Ketac cem. It had many properties

similar to the modern luting GIC’s

All the properties chartered out are good except for the elastic modulus, which is quite

high. GIC has a tendency towards plastic deformation as it is less stiff. In this regard,

it is not preferred to cement all ceramic crowns as greater stresses will develop under

occlusal loading. It is better to use ZnPO4 in this case.

Even the film thickness, solubility is more than Zn PO4.

P:L ratio is 1:25 - 1.5g : 1ml

Some points to be kept in mind:

- No conditioning is required or rather should not be done as acid may get

forced into the dentinal tubules due to the increase hydraulic pressure.

- Excess cement should be removed only after it has set. Varnish should be

applied at the margins.

- It is unnecessary to maintain pressure as the freshly mixed cement has

sufficient thixotropic properties.

- Follow correct P:L ratio as increase in L will cause an increase in sensitivity

and increased solubility and an increase in P will cause a decrease in ability to

achieve complete seating, altering fit and occlusion.

Restorative Cement (Type II) Indications:

o The erosion/abrasion lesion

o Class V lesion

o Restoration of primary teeth

o Class III lesion

o Laminate restoration

o Microcavity preparation = box,slot,tunnel

o ART

o Patients prone to rampant caries

o Small medium sized class I lesion

o Repair of open margins around crowns and inlays.

The P:L = 3:1 As mentioned before, correct surface treatment, manipulation and

protection are essential for a long lasting restoration.

Liner and base:A lining cement is basically used to protect the pulp from temperature change, by

sealing dentinal tubules. It needs to be only 0.5mm thick. They have low physical

properties and are used to fill voids in cavity preparation. The P:L = 1.5 : 1

A base is used as a dentin substitute. According to Mount, the entire cavity should be

filled with GIC and then cut back to make room for amalgam /composite.

Lamination with composite/SANDWICH TECHNIQUE:

The use of GIC for replacement of carious dentin prior to attachment of composite to

acid etched enamel was first descried by McLean and Wilson in 1977. Both the

cement and the enamel are etched for better bonding and decreased microleakage

The procedure involves:

- Placing GIC at base of cavity

- Etching with 37% phosphoric acid for 1min. This results in a rough surface

suitable for mechanical locking

- DBA is applied

- Composite is placed.

Advantages included:

- GIC acts as a dentin substitute

- The high contraction stresses produced (2.8 – 3.9 Mpa) by the polymerization

shrinkage are reduced as the amount of composite is reduced

- Microleakage is reduced

- Minimization of number of composite increments, therefore time is saved

Lamination with amalgam:

There are 2 techniques:

1. GIC is placed and allowed to set. It is then cut back to make space for

amalgam. 45% PAA can be wiped over the set cement just before amalgam

condensation to attain a degree of clinical union

2. GIC is placed and amalgam is condensed when GIC is still in the early set

stage with moderate flow. Amalgam intermingles with the GIC and a

mechanical interlocking occurs. A degree of chemical bonding is also

expected as GIC can bond to metal oxides like SnO and AgO and amalgam

contains Sn and Ag mainly. Bond strength of up to 3-4 Mpa has been

obtained.

Pit and fissure sealant:A cariostatic action is essential for a caries preventive material. GIC is recommended

as a P and F sealant where the orifices of the fissure are patent. The size of the fissure

should allow a sharp explorer tip to enter the crevice which should be > 100 wide.

Otherwise, GIC can get lost through erosion due to its low wear resistance and

solubility.

Orthodontic luting cements:Luting cements are needed to effect a stable attachment of bands and brackets during

tooth movement. A common clinical problem is

o demineralization and caries under brackets and bands

o detachment causing schedule disruption and Rx delay.

Both these problems can be solved by using GIC as F release reduces

demineralization under brackets and bands. Conventional GIC has shown proven

benefit over Zn PO4 for band cementation with regard to retention and decreased

demineralization.

Core build up:The construction of a core is often necessary prior to crown preparation in order to

give the final crown appropriate resistance and retention. Traditional GIC lack the

necessary tensile and flexural strengths for anything other than small core build ups or

blocking out under cuts in preparations.

GIC in endodontics:

They are used for:

o Sealing root canals orthogradely and retrogradely

o Restoring pulps chamber

o Perforation repair

o Sometimes for repairing vertical fracture.

GIC was used because of :

Its capacity to bond which enhances seal and reinforces the

tooth

Its good biocompatibility, which would minimize irritation to

periradicular tissues

Its F release, which imparts an anti- microbial effect to combat

root canal infection

Preventive restorations: ART

A highly viscous GIC was designed as on alternative to amalgam for posterior

preventive restorations to be used mainly under conditions of minimal

instrumentation. The high F release would help in caries stabilization. This is the

atraumatic restorative techniques or ART which use these packable, high F

releasing GIC’s to control caries.

2. High fluoride releasing command set GIC

This type of light-cured GIC is used for surface protection, caries stabilization

and as an intermediate restoration. The fluoride released is higher than the usual

GIC and is pink in colour to serve as a reminder of its temporary nature and

identification of margins. Newly exposed tooth surfaces which are at high risk of

demineralization can be applied with a coat of this cement to make it more

stronger and more acid resistant

Conclusion:In spite of substantial improvement conventional GIC’s have short comings with

regard to moisture sensitivity, wear resistance, flexural strength and final finish. Even

though chemical adhesion and fluoride release are major benefits, conventional GIC’s

are restricted to special indications like class III or class V cavities. Advancements

have occurred to overcome these problems but most are still awaiting clinical trials.

REFERENCESG.J MOUNTKENT AND NICHOLSONMJOR AND DAVIDSONSTRURDVENT