Composite Resins

Question 1

uses of a filling material

Answer 1

• new/failed restoration for caries
• replace abraded/eroded tissue
• trauma

Question 2

ideal properties of a filling material

Answer 2

• mechanical (strong, rigid, hard)
• bond to tooth/bonding systems
• thermal properties
• aesthetics
• handling/viscosity
• polishable
• radiopaque
• biocompatible
• anti-carcinogenic

Question 3

5 components that make up composite

Answer 3

1. glass filler particles = dif. sizes and volumes (many types i.e. quartz or microfine silica)
2. soft resin = difunctional molecules, C=C allows for cross linking of monomers called free radical polymerisation (i.e. Bis-GMA or urethane dimethacrylates)
3. camphorquinone = photoinitiator activated by blue light to cause polymerisation of Bis-GMA
4. low weight dimethacrylates = adjusts viscosity and reactivity
5. siliane coupling agent = binds to filler particles, stopping moisture from doing so, allowing for good bonding between filler and resin

Question 4

4 ways to classify composites

Answer 4

1. filler type
2. curing method = self or light cured
3. area of use = anterior (microfilled), posterior (heavily filled)
4. handling characteristics
   
   • flowable (less filler)
   • condensible (greater porosity)
   • syringable (less porosity)

Question 5

what is hybrid composite?

Answer 5

More than one size of filler particle used

Question 6

benefits of hybrid composite?

Answer 6

• improved mechanical properties (strength, rigidity, hardness, abrasion resistance)
• lower thermal expansion and polymerisation shrinkage
• less exothermic in polymerising
• more options for aesthetics
• can make resin radiopaque

Question 7

types of curing composite

Answer 7

• self curing = aromatic tertiary amine reacts with another molecule to cause breaking of C=C causing polymerisation
• light curing = camphorquinone and blue light causes the breaking of C=C

Question 8

advantages of light curing

Answer 8

• more working time
• less finishing required (shaped before)
• higher filler levels and less porosity (as not two pastes)

Question 9

name the two depth curing tests for materials in DMS

Answer 9

1. ISO4049 = cylander of. composite light cured, soft removed and hard depth divided by two
2. hardness value = better, hardness at surface measured and ratioed to dif depths, value = depth at 80% of surface hardness

Question 10

depth of composite cure

Answer 10

• 2mm, if not then soggy bottom and poor bonding

Question 11

issues with light curing

Answer 11

• polymerisation shrinkage = microleakage/cusp fracture (caused by dimethacrylate monomer)
• overexpose material
• underexpose material
  - both due to poor material instructions
• premature setting via dental light

Question 12

properties of dental materials and how to improve them (6)

Answer 12

1. translucency (smaller filler)
2. polishability (smaller filler & better filler-matrix bonding)
3. strength (>%filler to matrix & better filler-matrix bonding)
4. radiopacity (glass containing oxides cause)
5. handling characteristics (small and large filler particles)
6. low polymerisation shrinkage (>filler content)