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
What is polyacrylic acid also Called?
Dentine conditioner
How do we use 10% polyacrylic acid?
We apply it onto the tooth before placing the glass ionomer
Leave it on for 20 secs
Then wash it off
What does adding a conditioner increase?
The percentage gap free margins following 100,000 chewing cycles
Describe how much fluoride is released from GIC
Initially a lot of fluoride is released then most of it is lost so overtime less is released
Whats the main reason fo the removal of GICs?
Secondary caries
How many GIC restorations were removed du to secondary caries in 1996?
50% of 790
What are the benefits of the fluoride release process?
- Greater caries inhibition seen than amalgam
- Significantly greater caries preventive effect than composite
- Significantly fewer demineralised restoration margin in class II restorations in deciduous teeth
What are the disadvantages of glass ionomers?
- Weaker compared to other material
- Poor aesthetic compared to composite
- Poorer survival time compared to other materials
What happens t the colour of GIC overtime?
It changes colour overtime becoming more translucent
This can make the restoration look more tooth coloured or make it look worse
Which restoration material has the lowest mean survival time ?
GIC
What happens if we mix amalgam powder to the glass ionomer mix what do we get?
Silver cerment
Does silver carment haven benefits?
It is more resistant to acid but it deteriorates the aesthetics of a GIC
What are he negatives of silver cerment?
- Lower Flexural strength
2. More prone to abrasion
What did chemists do to GIC in 1989?
They added HEMA to the Glass ionomer
What is HEMA
It is a monomer in the composite bonding agent and it can polymerise in he presence of blue light
How can HEMA be added to GIC?
- Can be added as a liquid
2. Can be added chemically to replace some of the carboxylic groups on the poly acid chain
What do we call GIC that has added resin?
Resin modified glass ionomer cement
RMGIC
Give some advantages of RMGIC
- Better aesthetics
- Command set
- More resistant to losing ions during maturation
- Its stronger
What are the disadvantages of RMGIC?
- Doesn’t bond to the tooth surface as he hydrogen ions are all Locked down when the restoration is set
- Doesn’t release as much fluoride
- Polymerisation shrinkage
Which teeth is RMGIC more suitable for?
Anterior teeth
What development occurred to GIC in the mid 1990s?
More filler was adde
What does adding filler to GiC do?
Adds strength and wear resistant
What are some of the problems associated with current GICs?
- They are weak
- They fracture easily
- Wear is high
- It is complicated to use
- Short workable time
- Stops acting like GIC once cured
What is the newest most recent development in GIC?
Zinc reinforcement
How is zinc added to GIC?
Calcium ions are replaced by zinc ions
Name the zinc reinforced GIC we use?
ChemFil
Give some benefits of zinc reinforced GIC
- Best strength
- Bonds directly to enamel and dentine
3 N conditioning or varnish required
State an ideal situation where Zinc reinforced GIC be used ?
In compromised situations like a restless child
Give some examples of whenGIC would be the best restoration materials?
- Cavities extending below the CEJ
- Temporisation
- Stepwise excavation
- Fissure sealants
Which type of GIC would you use to restore a cavity extending below he CEJ/
RMGIC
OR
Traditional GIC
When placing a temporary restoration which restoration material would you use?
Traditional GIC for example Fuji triage
Why would reuse fuji triage when placing a temporary restoration?
As it is a very different clout sound tooth issue so I can be easily removed
Give some indications of traditional GIC
- Sub-gingival restorations
2, Temporary restorations - Stepwise Excavation
Give examples of traditional GIC
- Chemfil
- Fuji Triage
3 .Fuji IX
Give some indications of Resin modified GIC
- Non load-bearing restoration
2. Bonded amalgam
Give examples of resin modified GIC?
Fuji II LC
Give some indications of zinc reinforced GIC
- Long term temporary
- Caries management
3 Fissure sealant
Give some examples of zinc reinforced GIC
Chemfil Rock