GIC and RMGIC

Question 1

What bonding does GIC use?

Answer 1

Chemical

Question 2

What are the applications of GIC?

Answer 2

• Restorations
• Luting
• Bonding/conditioning
• Protection
• Fissure sealing
• Protection of root surfaces against caries

Question 3

What are the two components of GIC?

Answer 3

Acid = poly acylic acid

Glass = calcium fluoroalumosilicate glass

Question 4

What component of GIC acts as the base?

Answer 4

Calcium fluoroaluminosilicate glass

Question 5

What shape does the GIC molecule have?

Answer 5

Tetrahedral shape

Question 6

What additives do we have to enhance the basic properties?

Answer 6

Sodium, calcium and strontium

Question 7

What acids do we use in GIC?

Answer 7

Polyalkenoic acid

such as polyacrylic acid and polyitaconic acid.

Question 8

Why is tartaric acid used in GICs?

Answer 8

• It improves handling, extends the working time and sharpens the setting characteristics

Question 9

What does tartaric acid interact with in the GIC

Answer 9

It interacts with glass particles, liberating the aluminium ions which can then interact with the polymeric acid.

Question 10

How is GIC mixed on the pad?

Answer 10

• Bottle containing powder and the liquid in dispensed in the squeezing bottle. Spoon is what measures out the powder.
• Can see the mixing of the cement here, polymer mixing pad. 1 scoop of powder to 2 drops of liquid in this example. The drops of liquid need to come out as proper drops with no air bubbles.

Then mixing can be carried out by spatulating the liquid with the powder until a smooth mix is achieved.

Question 11

How long does GIC take to set?

Answer 11

2-3mins

Question 12

What are the 3 stages of GIC setting reaction?

Answer 12

1) Dissolution: powder is mixed with liquid and the acid attacks the outer part of the glass particles

2) Initiation gelation and hardening: the polymeric acid molecules upon ionisation adopt a more linear form which makes the carboxylic acid more accessible.
- The ions then released on the interaction of the polymeric acid with the glass then interact with the poly acid molecules to form ionic cross-links which causes gelation

3) Hydration of salts: the aluminium ions become more involved and aluminium polyacrylates are formed - maturation is progressive via hydration of matrix salts

Question 13

How are GICs mixed?

Answer 13

• Usually powder and liquid

- Ratio of powder to liquid is important and manual mixing is susceptible to operator induced variability

Question 14

What are the two forms that GIC is dispensed in?

Answer 14

• Powder and liquid phase

- Powder and aic (freeze died) and water

Question 15

What is the importance of the aqueous systems?

Answer 15

• Provides ion transport
• Acid-base setting reaction
• Fluoride release
• Bound into the set cement
• Affects ultimate stability

Question 16

Why do we water in GIC?

Answer 16

To make it an aqueous system.
Water allows for ion transport, allowing for H+ ions to be released to attack the basic glass to start setting.
Without water, no setting can occur.

Question 17

Why do we need to get the level of water corect in GIC?

Answer 17

Too much moisture = can lead to loss of the polyacrylate chains.
Excess water causes sub-optimal properties of the cement leading to loss of physical properties and translucency.

Too little moisture = the cement will get cracked. The surface will be soft and there is a lot of the matrix forming ion.

Question 18

What are the 2 theories of how GIC adheres to the tooth?

Answer 18

One theory:

• Polymeric acid molecules collate with the calcium in enamel.
• Formation on calcium poly-alkenoic salts then occurs forming the bond

Another theory:

• Adhesion is due to hydrophilic nature of GIC
• Adhesion occurs through hydrogen bonding between the free carboxylic acid group of cement and the bound water on the surface of the tooth

Question 19

Why do we condition the tooth before placing GIC?

Answer 19

• Removal of smear layer
• Partial demineralisation of tooth surface
• Increasing the SA
• Allowing for micro-mechanical bonding (as well as the chemical)

Question 20

What governs the physical properties of GIC?

Answer 20

• The powder to liquid ratio

Question 21

What does GIC appear like in the mouth?

Answer 21

Dense and opaque, tooth coloured.

Question 22

What bioactive property does GIC have?

Answer 22

• It can release fluoride

Question 23

What are the minimum requirements for GIC for:

a) setting time
b) compressive strength
c) opacity

Answer 23

a) 2-6mins
b) 100mPa
c) 0.35-0.9

Question 24

What are the main + and - of GIC?

Answer 24

+ Fluoride release
+ Adheres to tooth via chemical bonding
+ Acceptable aesthetics
+ Low solubility after full maturation

• Low fracture resistance
• Susceptible to early water contamination
• Short working time
• Long setting time

Question 25

What is additionally added into RMGIC?

Answer 25

Hema molecules.

• This is a molecule with a C=C bond that can be polymerised under light cure
• It is a methacrylate molecule

Question 26

What is the main setting reaction in RMGIC?

Answer 26

• Acid-base reaction

- Rapid set is due to polymerisation of 2-HEMA as another reaction

Question 27

What is the suggested main benefit of RMGIC over GIC?

Answer 27

• Compressive, tensile and shear bond strength are higher

Question 28

What are the clinical considerations of RMGIC and GIC?

Answer 28

• Adhesion to tooth so conservative cavity preparation
• Isolation of GIC in early stages is advocated due to water uptake leading to staining
• RMGIC has a low pH so in a deep cavity we need to use a lining material to prevent necrosis to pulp.

Question 29

What are giomers composed of?

Why were they deverlpoed?

Answer 29

Composites with glass ionomer cement filler particles.

To try and give a bioactive element to composites.

Question 30

What is the main advantage that GIC has over composites?

Answer 30

The ability to chemical bond to the tooth (no adhesive needed).