Glass ionomer cement Flashcards
When were glass ionomer cements first used?
1971
Why were composite fillings not used much in 1971?
As bonding wasn’t very well understood so composite fillings didn’t last very long
Also patients often suffered from secondary caries
What was he best material for restorations back in the 1970s?
Gold as it was hard wearing
What material was used in the 170s but isn’t used that much anymore?
Silicate cement
What is silicate cement made up o?
Glass powder and polycarboxylic acid
Describe silicate cement
It is kinda sooth coloured
It sets harder than silicate
Releases fluoride
It chemically bonds to enamel and dentine
What components make up glass ionomers?
Ion leachable glass
Long poly acid chains
Both suspended in a solution of water
Name the 3 main stages of th setting reaction that occurs with GICs
- Dissolution
- Gelation/ hardening
- Maturation
When does dissolution start?
When water is added to The acid
What is a poly acid?
A long polymer chain with lots of carboxylic groups on it
What happens when water is added to the poly acid?
The protons (H+ ions) become liberated an mango of into the solution This leads negative carboxylic acid croups on the poly acid chin
What makes up the glass part of GIC?
Silicate Calcium aluminium fluoride This is called: Calcium – Alumino-Fluoro – Silicate glass
How the hydrogen ions react with the Calcium – Alumino-Fluoro – Silicate glass
They erode away at the glass causing the ions that make up mass to move into the solution
What happens to the calcium and aluminium ions in solution?
They come across negatively charged poly acid chains
How many poly acid chains can calcium ions attach to?
2 as they are positively charged by 2
This leads to cross linking
As the calcium binds to poly acid chain what happens?
It releases 2 fluoride ions
How much time does intake for the hardening process to start?
4ish secs
What happens during maturation?
More and more calcium and aluminium ions cross link acid chains
What risk is present during the maturation phase?
Until the aluminium and calcium ions form cross links they may be lost from the material into the saliva f the restoration gets wet
This can make the restorations weak
How can we minimise the loss of calcium an aluminium during the maturation phase?
By coating the GIC once its hardened using a garish to bonding resin
What improves the wear resistance of a glass ionomer?
Using a varnish
Lists the benefits of glass ionomer cement
- it is easier use
- Doesn’t need bond
- Tolerates moisture
- Chemically bonds to enamel and dentine
- Releases fluoride
How does GIC bind to enamel and dentine
Some of the hydrogen ions come into contact with the tooth surface
This releases calcium and phosphate ions from the apatite
Some of these minerals diffuses into the glass ionomer
What do we need to do to improve GIC adhesion to the tooth?
Remove the smear layer
What issued to remove the smear layer?
10% polyacrylic acid