Glass ionomer cements and resin modified GICs

Question 1

Compressive strength of GICs

Answer 1

> 50MPa

Question 2

Advantageous properties of GICs

Answer 2

Relatively durable
Insoluble
Fluoride releasing and associated protection against caries
Aesthetic
Adhesion to mineralised tooth tissues
Antibacterial?
Biocompatible
Set without exotherm, no shrinkage

Question 3

Disadvantagous properties of GICs

Answer 3

Relatively brittle
Poorer aesthetics than composite
Susceptible to wear

Question 4

What are GICs composed of?

Answer 4

Composed of a basic fluoroaluminosilicate glass, a polymeric acid, water and tartaric acid

Question 5

How are GICs formed?

Answer 5

After mixing by acid-base reaction where metal cations for salt bridges with ionised carboxylic acid groups on high molecular weight polyacids

Question 6

Presentation of the GIC

Answer 6

Powder:
-fluoroaluminosilicate glass
-freeze dried polyacrylic acid
-pigments
Liquid:
-poly(acrylic)
-tartaric acid
-distilled water

Question 7

Phases of acid-base reaction to form GIC

Answer 7

Dissolution (acidic attack of glass surface)
Gelation (early cross-linking by CA2+)
Hardening (substitution of Ca2+ by Al3+)

Question 8

End result of acid-base reaction to form GIC

Answer 8

Composite biomaterial of acid-degraded glass particles in a cross-linked hydrogel matrix

Question 9

Factors predicted to influence biocompatibility

Answer 9

Bulk composition
Surface chemistry
Ion release

Question 10

Clinical uses for GICs

Answer 10

Restoration of deciduous teeth
Class V restorations in permanent teeth
Erosion/ abrasion lesions
Have been used as fissure sealants
Atraumatic restorative treatment (ART)
Luting cements
Cavity bases

Question 11

When are GICs contra-indicated

Answer 11

For highly loaded sites e.g. cuspal or incisal edge, or where aesthetics are important

Question 12

What kind of px favours use of GICs

Answer 12

High risk px - fluoride release factors

Question 13

Antibacterial properties of F-

Answer 13

Mechanisms include effects on metabolism (via enolase inhibition and/ or metabolic toxicity)
BUT F- probably not toxic to biofilms

Question 14

How does F- work?

Answer 14

Mechanism via interaction with HAP of enamel and dentine
F- able to substitute of OH- gps in crystal structure to generate fluoapatite
Fluoapatite very resistant to demineralisation

Question 15

What is a RMGIC

Answer 15

Like glass-ionomer but with addition of water miscible monomer hydroxyethylmethacrylate (HEMA) and a photoinitiator
Shares GIC chemical bond to untreated dentine

Question 16

How does a RMGIC set

Answer 16

Sets with both an acid-base reaction and photo-polymerisation

Question 17

Vitremer (3M)

Answer 17

GIC plus HEMA with photoinitiators
Setting reaction
-dissolution
-gelation
-hardening
-light cure
-polymerisation

Question 18

Dyract AP

Answer 18

Compomer
Polyacid modified resin composite
Does not stick to tooth tissue
Fluoride releasing glass (but less than GIC)
-UDMA
-photoinitiator
-resin monomer modified with carboxylic side chains
These material systems need to absorb water before they can release fluoride