Resin part 1

Question 1

What is the stages of Free Radical Addition Polymerisation of methyl methacrylate?

occurs in Acrylics

Answer 1

• Activation
• Initiation
• Propagation
• Termination - can occur when chain attaches to impurity/free radical or further growing chain.

occurs in Acrylics

Question 2

What does Free radical chain reactions mean for the clinician?

Answer 2

• Material contracts on polymerisation
• Reaction is exothermic
• Tertiary amine is not all used up

–Poor colour stability (clear – brown)

•Must use correct mixing ratio

Question 3

what are the properties of Acrylics on its own?

Answer 3

• Match tooth shade (but not in long term if have amine)
• Are exothermic when setting
• Irritant to pulp due to residual mma
• Interact with Eugenol
• Contract (6% by volume)
• Have low hardness
• Poor abrasion resistance

Question 4

What is a Resin Compostie and who made it?

Answer 4

Resin composite

–“A combination of two chemically different materials with a distinct interface separating the components and having properties which could not be achieved by any of the components acting alone.”

–Bowen et al., 1972.

Question 5

What are the resin composite fillers?

Answer 5

– Quartz

– Silica

– Glasses

• Aluminsilicates • Boro silicate • Barium Oxide

Question 6

What is the resin composite Coupling agent?

Answer 6

coupling agent:

– δ – methacryloxypropyltrimethoxysilane

Question 7

Answer 7

Question 8

How do you activate a resin composite?

Answer 8

– Chemical

• Powder Liquid
• Paste Liquid
• Encapsulated

– Light

• Early ones U V (health risks)
• Today Camphorquinone

Question 9

What does Camphorquinone do?

Answer 9

• Yields the necessary free radicals to start the polymerisation
• This is visible blue light
• Most readily generated by quartz halogen lights

-curing dental composites

Question 10

What does all resin composites contain?

and what are they useless without?

Answer 10

• Resin and Filler alone useless without effective coupling

Question 11

What does a couping agent do?

Answer 11

“The coupling agent transfers the stresses generated under loading from the rigid and brittle filler to the more flexible and ductile polymer matrix”

Question 12

What are the 2 types of classifications for resin composites?

What must the conform with to be on the market?

Answer 12

• ISO 4049

– Type 1 – restoration of cavities involving occlusal surfaces

– Type 2 – All other polymer based filling and restorative materials

• To be on market must conform with ISO 4049.

Question 13

What is the C-factor?

and why does it matter?

Answer 13

C-factor = Number of bonded surfaces / Number of un-bonded surfaces

it matters because composites shrink.