CSA tooth coloured materials 2 GIC Flashcards
What are the types of cements?
• Light cured GIC Resin modified glass polyalkenoate (hydrophilic)
• Compomer
- Polyacid modified resin cement (hydrophobic)
• Composite
- Composite (Hydrophobic)
What is GIC?
formed by acid-base reaction between fluoride (F) containing glass & polyacid
What can GIC be formed by?
o Liquid acid + powdered glass
o Freeze dried acid, powdered glass & water
What is the composition of acid and base
- Fluoro-aluminio-phospho-silicate (base)
* Polyacid e.g. Polyacrylic acid or polymaelic acid
How to change setting of GIC?
o Change molecular weight of polyacid
o Change conc. of acid
o Control activity of glass
What are the advantages of GIC?
- Very adhesive & sticks to tooth surface easily
- Cariostatic – releases fluoride
What are the disadvantages of GIC?
- Technique sensitive
- Moisture sensitive
- not placed in stress bearing areas
- Low tensile & fracture toughness
- Poor wear resistance (Not for posterior fillings)
- can pick up stain
- Not command set so need to work quickly
- appearance/strength change over time
What is the setting reaction ?
polyacid and base gives polysalt and water
What are the stages of setting reaction ?
Stage 1 – Decomposition Stage 2 – Migration Stage 3 – Gelation Stage 4 – post set hardening Stage 5 – Maturation
What is decomposition in setting reaction?
- Acid dissolves in water – forms viscos solution with glass spread
- H+ ions dissociate from COOH groups on polyacid + displace cations on surface of glass
What is Migration in setting reaction?
• (Ca2+ / Al3+) migrate to neg charged ions in dissolved polyacid
What is Gelation in setting reaction?
• Cations form cross links in polymer chains > longer polysalts form, modified glass surface becomes a silica gel
What is post set hardening
• continues as more cations diffuse from gel to polymer chains
What is maturation in setting reaction?
- Al3+ ions bound in cement matrix + precipitate
- Ca2+ ions precipitate over 24 hours as well
- setting is very slow
- Formation of polysalts keeps occurring:
What happesn when Formation of polysalts keeps occurring:
o Hydration of polysalts
o Expanded gel structure
What does fluoride do in matrix?
• free to move & released from matrix w/o affecting structure of cement
What does GIC reduce at margins?
risk of secondary caries
What is the role of GIC?
• Slowly hydrates polysalts in mature cross linked matrix
o Increases strength
o Improves translucency
o Increases resistance to desiccation
What does excess water do ?
Contamination >Increases opacity, decreases strength + harness
What does loss of water do ?
Desiccation >Increases crazing/cracking
How is bonding to tooth structure via GIC ?
- Ca2+ ions present in HAP, form cross links with PA chain
* chemical bond to enamel structure – seals against bacterial ingress
How does GIC bond to dentine?
polyacid chains bond to collagen in dentine via carboxyl/amine groups via Hydrogen bond
What does GIC release?
- Fluoride released from glass by acid attack (polyacrylic)
o Ions =free to move
o Ions contribute to biocompatibility of material + capacity to inhibit recurrent caries
What does biocompatibility describe?
materials property of being compatible with living tissue
o Plaque can’t thrive on GIC surface
o S. Mutans growth is inhibited by restorations
What can the freshly mixed cement of pH 0.9-1.6 lead to ?
lead to a mild inflammatory pulpal response
What promotes dentine bridge formation ?
o Direct pulp capping material
Indications of GIC?
- Cementation of rigid restorations e.g. bridges/veneers
- Restorations of primary teeth
- Class III/V carious lesions
- Crown margin repair
- Forms a base under amalgam/composite
- Temporary restorations – carious cavities/ fractured tooth
What are cemerts?
- Silver particles fused with glass
- poor aesthetics
- Mechanical properties are worse
What are indications of cemerts ?
•Core build up
o Low C of TE
o Good adhesion
o Brittle
What is alternative cements?
• DiamondCarve + Diamond 90-(sets in 90 seconds)
o Based on glass & co polymer of
- Polyvinylphosphoric acid
- Polyacrylic acid
Viscous GICs like Fuji IX, ketc?
- increased powder: liquid ratio
• Decreased water content
• Smaller glass particles
• increased strength
What is the survival time of GIC?
6 years
What is Kic?
measures fracture toughness
What is RMGIC?
•GIC with addition of a small quantity of resin components
What mods. are done to RMGIC?
- Water replaced by water/HEMA mix. (vitremer)
2. Mod. of polyacid side chains that polymerise by light curing mechanism (fuji II + Photac-fil)
What is hydroxy ethyl methacrylate
- Polymerises when exposed to light
* irritating and can be allergic to acrylate resins
How are side chains modified in RMGIC?
• C=C bonds added to part of polymer chain >polymerisable functional groups
What are the advantages of RMGIC?
- Tooth coloured
- Shorter setting
- Sets on command
- Less moisture sensitive
- Increased tensile strength
- Better wear characteristics
- Easier to use
- F release is moderate and can recharge – Acts as fluoride reservoir
- Easier USE
- Increased bond strength to composite
- no bonding system
What are indications of RMGIC?
- Cervical + root caries
- Base for composite/amalgam
- Abfraction lesions >TSL occurs along gingival margin
What is compounds of RMGIC?
- BisGMA/UDMA are monomer, TEGMA/EDGMA are diluent monomers
- Silane coupling agent
- Inorganic fillers present
- UV Stabilisers
- Inhibitors
What is compomer ?
Polyacid modified resin cement):
What is compomer
• Acid-base functionality added to resin monomers
What is composition of compomer ?
- UDMA resin
- TCB resin – contains C=C + COOH groups
- Strontium fluorosilicate glass
- Initiators & stabilisers
What is setting mechanism of compomer?
1) light curing – induces polymerisation of resins
2) – Water uptake (from saliva/drinks etc.) = causes acid base reaction to take place & results in cross linking of matrix
What are advantages of compomers ?
- Good handling properties
- Good strength
- Command set
What are disadvantages of compomers?
- Poor adhesion
- Requires bonding agent?
- Less fluoride release –
- not used as much
What is chemfil rock-advanced GIC?
- Added zinc makes stronger/tougher –
- No conditioning cavity (less steps)
- No varnish/Vaseline (like regular GIC’s)
- used for temp restorations
