W9 - Composite Resin Update - Stoll

Question 1

When was composite first patented? By who?

Answer 1

1962 - Bowen R.L.

Question 2

What are the three main components of composite

Answer 2

Matrix (continuous phase)

Filler (dispersed phases)

Coupling agent (“glues” the filler to matrix)

Question 3

What are other things added to enhance composite (4)

Answer 3

Initiator/accelerator system

Stabilisers (for storage)

Bonding system (external interface coupling agent)

Pigments

Question 4

Why are modern nanofillers (smaller fillers) considered to be better

Answer 4

Higher amounts of nanofillers:

1. increases translucency (particles are smaller than the wavelength of light)
2. Reduces polymerisation stress (shrinkage)

Question 5

How does shrinkage occur during light curing?

Answer 5

During light curing, monomers move loser together in order to chemically react

Monomers develop into polymers

Polymer network becomes rigid due to increasing cross-linking of polymer chains

Shrinkage stress towards the centre of the material is produced

If bonding procedure is not strong, marginal gap formation will commence

Question 6

What is marginal gap formation and what problems can it lead to

Answer 6

Gap created due to shrinkage of material

Leads to microleakage, secondary caries, sensitivity and marginal staining

Question 7

If marginal gap formation happens when the bond is too weak, what happens when the bonding system is too strong?

Answer 7

The concentrated stress inside the tooth can lead to micro-cracks, tooth fractures and cuspal deflection

Ideally, we want to control the amount of shrinkage stress to maximize clinical success

Question 8

How do we make sure the composite is stress resistant?

Answer 8

Composite needs some type of internal elasticity

Ex.

Question 9

What is shrinkage stress?

Answer 9

A product of:

External constraint of the free shrinkage imposed by bonding to tooth surface

Size and nature of the monomers

Acquisition of stiffness during polymerization

Rate of the reaction

Question 10

2 ways of adjusting the viscosity of composite

Answer 10

Ultrasonic

Warmer

Question 11

What is ormocer composite? Problem?

Answer 11

Monomers as organic sidegroups connected to an inorganic backbone

Low shrinkage composite

• Higher toxicity than standard composites
• Poor longevity
• Lower wear resistance
• Poor marginal adaptation

Not really used anymore

Question 12

What is siloran composite (2007)? Problem?

Answer 12

Rind opening monomers

• Hydrophobic
• Incompatible with dentine adhesives
• No flowable
• Posterior only (low translucency)

Not commonly used today but still available

Question 13

What do dendritic comonomers do? (4)

Answer 13

Includes the use of dendritic monomer as a crosslinker

• Enhanced copolymerisation
• Increased polymer elasticity
• Modifies viscosity favourably
• Increased degree of conversion

Many new composites use this new monomer technology

Question 14

How do new composites using dendritic comonomer technology achieve low polymerization shrinkage and low polymerization stress? (4)

Answer 14

Large monomers

Low amount of small comonomers

Stress breaking comonomers

High amount of nanofillers

Question 15

What are the clinical properties of dendritic comonomer composites? (5)

Answer 15

1. High mechanical stability
2. Good marginal integrity
3. High translucency
4. Good polishability
5. Viscosity adjustable

Question 16

Problems of general composites (2)

Answer 16

Time consuming (increments of 2-3 mm)

Post op sensitivity possible

Question 17

Two causes of post op sensitivity

Answer 17

Partially cured composite

Bad bonding technique

Question 18

Are bulk fill resins and restos better than conventional?

Answer 18

• Less polymerisation stress, allow up to 4-5 mm increments
• studies have shown improved, but not statistically significant durability compared to 2 mm layering technique

Question 19

Problem of bulk fill materials?

Answer 19

Limited sculpability

Question 20

What are some possible new composite materials for the future?

Answer 20

• prepolymerized fillers (spheretec)
• Nanodiamond particles
• Antibacterial monomers
• Fluoride containing monomers

Question 21

What are Laminates?

Answer 21

Combination of a dentine and an enamel replacement

• Flexible material for dentine as a stress breaker
• Strong wear resistant material for enamel replacement

Question 22

What do polymerization modulators do?

Answer 22

interacts with the photoinitiator for a slower elasticity modulus development, decreasing polymerization stress

Question 23

What do photo initiators do?

Answer 23

Increase the depth of cure and thus you can have larger increments

Question 24

What do Dentritic comonomers do? (4)

Answer 24

• Enhance copolymerization
• Increased degree of conversion
• Increased polymer elasticity
• Modify rheological behaviour (viscosity)