Composite Resins

Question 1

What are the constituents of composite resin?

Answer 1

1. Filler particles (glass)
2. Resin (monomer = Bis-GMA)
3. Camphorquinone (blue light activates –> free radicals –> polymerises bis-GMA)
4. Low weight dimethacrylates
5. Silane coupling agent

Question 2

What are the advantages of composite?

Answer 2

• Aesthetics
• Conservation of tooth tissue
• Bonds to tooth tissue
• Low thermal conductivity
• No galvanism

Question 3

What are the disadvantages of composite?

Answer 3

• Polymerisation shrinkage
• Low fracture resistance
• High elastic deformation
• Post operative sensitivity
• Technique sensitive

Question 4

Define ‘configuration factor’

Answer 4

Ratio of bonded to unbonded surfaces

e.g. class I preparation there would be 5 bonded surfaces and only 1 un-bonded surface; the net result would be a c-factor of 5

Question 5

What is the implication of a high configuration factor?

Answer 5

Increased polymerisation contraction stress –> debond/ microleakage