Glass Ionomer

Direct Restoration Materials

Gold

Amalgam

GI

Composite

Glass Ionomer Cement

Composed of a mixture of silicate glass powder and an aqueous solution of polyacrylic acid

Powder of GIC

Calcium

Fluoride

Aluminum

In a silicate glass base

Setting Reaction of GIC

Acid soluble glass is attacked by the polyacids

Ca²⁺, Al³⁺, Na⁺, and F^- ions are released

Ca, then Al react with carboxyl group in the liquid acid to form polysalts

Salts then hydrate to form the gel matrix

Set cement consists of unreacted glass particles surronded by silica gel in a matrix of calcium and aluminum polysalts

Fluoride does not form the matrix and is available for release

Ca and Al

Reacts with carboxyl group in the liquid acid and form polysalts

Polysalts

Hydrate to form gel matrix

Set Cement

Consists of unreacted glass particles surrounded by silica gel in a matrix of calcium an aluminum polysalts

Importance of Water in GIC

Provides ion transport necessary for the acid-base reaction and fluoride release to occur

Chemically bound to the set complex and provides stability to the set material

Provides plasticity for better manipulation

Loosely Bound Water

Associated with Ca2+ during the initial reaction

Easily removed by desiccation

Tightly Bound Water

Hydrates the matrix

Not removed by desiccation

Associated with Al3+ and is critical in formation of a stable gel and strength of the cement

Chalky Appearance

Newly set GI are susceptible to moisture loss, which causes surface crazing and development of

Coating of Varnish

Early exposure to water or loss of water can compromise the mechanical properties of the cement

Overcome by this

Glas Ionomer

Bonds chemically to the tooth structure

Bonding

Due to reaction between carboxyl of polyacid & calcium of hydroxyapatite

Enamel is higher than that of dentin due to greater inorganic content

Fluoride

Decreases mineral solubility and enhances remineralization

GIC results in much lower incidence of secondary caries compared with amalgam or composite

Can be recharged from saliva and/or toothpaste

Properties of GI

Low exothermic reaction

Adheres chemically to tooth

Less shrinkage than polymerizing resins

Dimensional stability at high humidity

F release discourages microbial infiltration

Early moisture sensitive - requires protection

Poor abrasion resistance

Average esthetic

Resin-Modified Glass Ionomer (RMGI)

Retains the ion leachable glass powder but replaces about half the water with water compatible monomers, such as HEMA, along with the polyacid

Cures via acid-base reaction of the cement plus a photo-initiated polymerization of the monomers to give a polymer-reinforced cement (dual cure)

RMGI Setting

Traditional GI acid-base reaction

• Proceeds more slowly

• Delayed in abscnece of included water

Free Radical Polymerization

• Fast process

• Light and or chemical activation

• No bond to tooth

Yields cross-linked resin reinforced cement matrix

Resin reduces level of fluoride release

RMGI Bonding

Does not require etch prime bond

Dual cured

RMGI Properties

Strength and toughness improved

Fluoride release (less)

Esthetics improved (more translucent)

Bonding to composite improved

Greater shrinkage

Fast set with water sensitivity reduced considerably

RMGI Advantages

Biocompatible

Improved esthetics

Light cured - speeds up setting time

Packable consistency

Fluoride release

Better radio-opacity

No bonding required

Natural fluorescence

RMGI Uses

Sealants

Temporary restorations

Luting cements - crown placement

Sandwich restorations

Root caries restorations

Implant access openings

Luting Cements (RMGIC)

Fuji plus

FujiCEM

Ketac

Restorative Cements

Vitrebond - liner

Fuji II LC - light cured (RMGI)

Fuji Triage - temporary (band-aid) (GI)

Fuji IX - GIC

Indication of Sandwich Techniques

Class I, II, III, and V lesions

Deep posterior restorations

Extensive bulky posterior restorations

Posterior restorations with subgingival interporximal preparations that are difficult to isolate

When any part of the gingival margin of class II preparation has been extended past the CEJ, and no longer has an enamel cavo-surface

Clinical Benefits of Sandwich Techniques

Reduced post-operative sensitivity

Pulpal protection from irritation

Fluoride release over time

Helps in prevention of demineralization

Rapid placement and curing of a single bulk layer

Placement of moisture tolerant Gi restorative in sub gingival inter-proximal boxes

Open Sandwich

Restoration in a tooth in which two restorative materials are used

Generally chemically bound together - RMGI cervical and composite on coronal

Underlying material forms part of the proximal wall and is exposed to he oral environment

Steps for Open Sandwich

Pre-condition the tooth surface - only if not close to pulp

Place the RMGI material and light cure

Etch the tooth structure and GI filling with 37% phosphoric acid

Use a bonding agent

Place the composite

Finish and polish

Closed Sadwich

Base material is (GIC, RMGIC) is completely covered by the restorative material (amalgam, and composite)

Base material is not exposed to oral cavity - less F release and used for pulpal protection

May or may not be chemically bonded to the restorative material

Sealants

Indicated during initial eruption due to increased susceptibility to caries

Flowable Composites

High durability

Polymerization shrinkage and no fluoride release

GI Sealants

Fluoride release

Chemical bond to tooth

Wear faster

Prone to fracture