Glass Polyalkenoate

Question 1

What was Glass Polyalkenoate formely known as?

Answer 1

Glass Ionomers

Question 2

What are the Polycarboxylate Cements

Answer 2

ZnO

• Polycarboxylic acid
• Set cement

– Adhesive to tooth substance – Poor appearance – High solubility – Poor mechanical properties

Question 3

What are the 3 forms

Answer 3

• Powder and Liquid

– Powder mixed with water

– Encapsulated form

Question 4

What is the powder liquid materials?

Answer 4

POWDER

• Sodium Aluminosilicate Glass with about 20 % CaF.
• PLUS Vacuum dried polyacid

LIQUID

• Aqueous solution of acrylic/itaconic acid copolymer
• PLUS Tartaric acid to control setting characteristics

Question 5

Do you get more or less porosity when mixing cements with cements instead of mechanically?

Answer 5

Less porosity

Question 6

What can Unreacted glass core confer?

Answer 6

Translucency

Question 7

Is hydrogel moisture sensitive?

Answer 7

Yes

Question 8

What are the 2 phases of a setting reaction?

Answer 8

Involves cross linking of polyacid chains by ions liberated from the glass particles

Initial phase - (first few minutes)

At initial set Ca2+ predominates

Final phase - (about 24 hours to completion)

At final set Al3+ predominates

Question 9

How can clinician avoid moisture until final set is complete?

Answer 9

• protect from moisture with either the application of varnish or unfilled resin
• avoid dessication when polishing - use vaseline as a lubricant

Question 10

What are the properties of Glass Polyalkenoate?

Answer 10

• Adhesion to tooth substance
• Tooth coloured and Translucent – unreacted glass cores reflect colour of surrounding tooth and transmit light
• Fluoride release – from the glass itself
• Brittle and relatively poor abrasion resistance
• Fluoride uptake/sponge mechanism
• – takes up fluoride from oral cavity*
• – releases it again locally at a slow rate*

Question 11

What is the bonding to tooth substance in Glass Polyalkenate due to?

Answer 11

Cross linking with calcium ions

Question 12

Be familiar with this table

Answer 12

Question 13

Cermets is a related material to cements but what is it?

Answer 13

Silver (Ag) pelletized mixture of glass and metal particles

• • Radiopacity*
• •* Poor appearance
• • Some fluoride release*
• • Increased compressive strength*
• • Increased fatigue limit*
• • Same flexural strength and abrasion resistance*