GLASS IONOMER CEMENT



GLASS IONOMER CEMENT

INTRODUCTION

■ GIC were developed by Wilson and Kent in the lab of the Govt. Chemist, London in 1972.

■ Early versions lacked esthetic appeal and translucency.

■ Subsequent development and research by manufacturers has produced a number of very useful materials that can be used for dentistry variety of functions in restorative. [pic]

■

■ DEFINITION & SYNONYMS

■ An aqueous based material that hardens following an acid-base reaction between flouro alumino silicate glass powder and a polyacrylic acid solution.

■ Polyalkenoate cement

■ ASPA

■ GIC

■ [pic]

■ COMPOSITION

POWDER

• Is an acid soluble calcium flouro alumino silicate glass containing[pic]

•

LIQUID

• A Polyacrylic acid in the form of copolymer with itaconic,maleic or tricarboxylic acids.

MODIFICATIONS

METAL MODIFIED

CERMEt

SILVER ALLOY ADMIXED

RESIN MODIFIED

COMPOMER

MODIFICATIONS

■ Metal reinforced GIC:

-they were introduced to improve the strength,fracture toughness and resistance to wear.

-metal powders or fibers added to the glass powder.

-two types

■ Silver alloy admixed GIC:

this consist of physically blending silver alloy powder with the glass powder in the ratio of 1:7 and mixing with glass ionomer liquid. Eg:miracle mix

■ Cermet cement:

-formed by fusing the glass powder to fine precious metal powders like silver or gold through sintering.

-This sintered glass-silver composite(the ‘cermet’-ceramic metal)which is then ground to fine powder.

-the liquid for cermet cement is regular GIC liquid

Eg: ketac silver,chelon silver

■ RESIN MODIFIED GIC:

-developed to overcome the moisture sensitivity and low early strength of GIC

Powder:

-ion leachable flouroaluminosilicate glass particles with initiators for light curing or chemical curing.

Liquid:

-contains water and poly acrylic acid modified with methacrylate group & HEMA monomers.

■ COMPOMER:

-Also known as poly acid modified composites.

-developed to get the properties of flouride releasing capacity of conventional GIC & durability of composites

Setting reaction

■ Dissolution:

-dissolution of surface of the glass particle releasing calcium aluminium ions leading to formation of cement sol.

■ Precipitation of salts, gelation and hardening:

-Calcium aluminium ions bind to polycarboxylate groups.

-Initial clinical set is due to cross linking of more readily available calcium ions(4-10 mts).

-Later maturation occurs when the aluminium ion get bound within the cement matrix to form a more rigid cross linking between the polyacid chain(within 24 hrs)

■ Hydration of salts:

-during the maturation phase,there is progressive hydration of the matrix salts which leads to sharp improvement in the physical properties of the cement.

Structure of set cement

The set cement consist of an agglomeration of unreacted powder particles surrounded by silica gel in an amorphous matrix of calcium aluminium polysalts.

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PROPERTIES OF GIC

BIOCOMPATABILITY

■ Pulpal response to glass ionomer cements is favourable

1. High buffering capacity of the hydroxyapatite

2. Large molecular weight of the polyacrylic acid does not travel through the narrow dentinal tubules

FLUORIDE RELEASE

■ It is due to fluoride ions donot take part in the setting reaction but remain with in the matrix of the set cement and are continuously released into the oral cavity

■ GIC has ability to absorb fluorides from the mouth when topical fluorides applied & therefore act as a fluoride reservoir

COLOUR AND TRASLUCENCY

• Available in various shades and acceptable colour matching &translucency

• Moisture contamination drying affect colour

• Resin modified GIC has more colour matching&trans than conventional GIC

RADIOPACITY

► Radiopaque due to the presence of Lanthanum,Ba,Strontium in the powder

► Metal modified GIC is more radio opaque than conventional GIC

STRENGTH & FRACTURE RESISTANCE

■ GIC are weak & lack fracture resistance when compared to composite resin & amalgamProperly set GIC exhibit low solubility in the oral environment

■ Resin modified GIC has less than conventional GIC

■ Resin modified GIC are twice as strong as conventional GIC

ABRASION RESISTANCE

■ GIC are less resistant to abrasion than composite

■ Cermet ionomers have more than coventionalGIC due to silver particles

SOLUBILITY & DISINTEGRATION

• Properly set GIC exhibit low solubility in the oral environment

• Resin modified GIC has less than conventional GIC

THERMAL EXPANSION & DIFFUSIVITY

◆ GIC have linear coefficient of thermal expansion & thermal diffusivity similar to that of tooth

ADVANTAGES OF GIC

▪ Adhesion to enamel &dentin

▪ Anticariogenic effect

▪ Acceptable esthetics

▪ Low solubility

▪ Biocompatibility

▪ Less technique sensitivity

DISADVANTAGES OF GIC

1.Low fracture resistance

2.Low wear resistance

3.Colour

4.Sensitivity to moisture soon after setting

INDICATIONS

□ As a Pit and Fissure sealant

□ Class I restorations

□ Tunnel restorations

□ Class III restorations

□ Class V restorations

□ Root caries

□ As a Liner and Base

□ Restoration of deciduous teeth

□ As a Core build up material

□ Luting cement

□ As a Interim restorations

□ As a repair material

□ In Endodontics

CONTRAINDICATIONS

□ In stress bearing areas

□ Labial buildups

□ Cuspal coverage

□ In mouth breathers

DISPENSING AND MANIPULATION

• Mechanical mixing

• Hand mixing [pic]

• [pic]

• CLINICAL STEPS

1)Isolation-Rubber dam, cotton rolls, retraction cords & saliva ejectors.

2)Tooth preparation-To enhance the adhesion of GIC.

A. Cavity preparation-Is required while restoring class III or class V carious lesions. No mechanical retentive features are necessary.

B. Prophylaxis-Using pumice slurry carried in a bristle brush. This will remove any plaque or salivary pellicle from tooth surface.

C. Surface conditioning-Using 10% polyacrylic acid(10-15 sec). This lowers the surface energy of tooth thus increasing the wettability of GIC.

It removes the smear layer while retaining the smear plugs.

3)Proper manipulation of cement-GIC performs best when manipulated acc. To manufacturers instructions.

4)Careful finishing &polishing-Best finish for GIC is essentially the matrix finish.

■ Initial trimming using BP blade or sharp carver.

■ Final finishing and polishing is done after 24 hrs using diamond points &soft lex discs from course to fine.

5)Surface protection- To prevent water contamination & desiccation while setting.

Using low viscosity resin, resin bonding agent, copal ether.

CLINICAL APPLICATIONS OF GIC

PIT & FISSURE SEALANTS

■ Recommendations for fissure sealing using GIC (Mc Lean &Wilson)

1. The pit &fissure should be patent-An explorer tip should be able to enter the orifice of the fissure.

2. Erupting teeth with poor oral hygiene High caries risk where good moisture control is difficult.

CLINICAL PROCEDURE

a) Fissure widening

using a fine tapered diamond, to ensure better flow & retention of GIC

b) Conditioning

using 10% polyacrylic acid for 10-15 sec

c) Cement placement

type III or resin modified is used

[pic]

[pic]

TUNNEL RESTORATION

■ By JINKS in1963 as a conservative alternative for class II cavity preparation in primary molars .

■ Later HUNT & KNIGHT modified the technique for restoring small proximal caries

[pic] [pic]

CLASS III GIC RESTORATIONS

• INDICATED IN

• Patients with high caries incidence

• When the the labial enamel is intact

• Low occlusal stress &margins are not in areas of occlusal contact

CLASS V GIC RESTORATIONS

• INDICATED IN

• Patients with high caries rate

• Several abrasion &erosion lesions

• Where esthetics is not of prime concern

• Root surface lesions as subgingival margins are suitable for GIC

• [pic]

• THE ART TECHNIQUE

• First evaluated in Tanzania in the mid 1980s

• Consists of a simplified approach to caries management. Hand instruments are used to excavate the soft caries followed by restoring the cavities with a highly viscous version of auto cure GIC

• [pic]

• [pic][pic]

• GIC AS LINER & BASE

• Lining cements

• -Type III GIC is used in a low powder-liquid

• ratio(1.5:1)

• -Are employed under any restoration when cavity is deep

•

• Sandwich technique

• -Developed by Mclean to combine the beneficial effects of both GIC& composite

• -Also called laminate/ bilayered tech

• - Indicated in large class III,IV,V,I,II cavities with composite

• CLINICAL STEPS

• -After cavity preparation condition the cavity

• -Type III GIC / resin modified GIC is used to replace the lost dentin(1-2mm)

• -Once set cut back to expose the enamel margins &to allow enough bulk for composite

• -Etch the enamel & GIC with phosphoric acid (15sec)

• -Wash and gently dry

• -Apply a thin coat of enamel bonding agent

• -Composite resin build up

• [pic][pic]

• LONGTERM TEMPORARY RESTORATION

• As apart of a caries control programme in acute carious lesions that are rapidly advancing towards pulp

• While awaiting the outcome of a pulp capping procedure

• [pic]

• CORE BUILD UP

• Cermet cement is used especially where colour match is not so important

• Adequate remaining natural tooth str -

• at least half of the original crown bulk & 3mm of crown height from the gingival margin is required

• [pic]

• LUTNG WITH GIC

• GIC used for luting inlays ,onlays ,crowns, bridges as well as orthodontic appliance

• [pic]

• CONCLUSION

• “ GLASS IONOMER CEMENT HAVE INCREASINGLY BECOME AN ESSENTIAL PART OF DENTISTS ARMAMENTARIUM FOR PROVIDING TRAETMENT THAT CONSERVES TOOTH STRUCTURE AND ASSISTS IN ITS REMINERALISATION WHILE MAINTAINING ESTHETIC APPEAL”

• REFERENCES

• Prevention and restoration of tooth structure –Graham J Mount.

• Philip’s Science of Dental Materials-Anusavice

• Clinical operative dentistry-Remya Raghu

• Operative dentistry-Satheesh Chandra

• Operative dentistry-Vimal Sikri

• Notes on Operative dentistry and Endodontics- Dr.Nareendranatha Reddy

• Dental materials-John J Manappalli

• Notes on Dental materials-Subarao

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