Resin Based Composites

Question 1

What is C-factor

Answer 1

Configuration factor.
Ratio between bonded surface area of resin based composite restoration to non-bonded or free surface area.

Greater the C-factor, greater will be the stress developed leading to formation of gaps, marginal breakdown and leakage

Question 2

What are resin based composite composed of

Answer 2

Matrix
Filler
Coupling agents.

Question 3

Key advantage of Resin

Answer 3

They can be made into ranges of consistency from highly fluid to rigid pastes which allows them to be easily manipulated and molded to a custom made form

Question 4

Applications of Resin based composite

Answer 4

Cavity and crown restoration
Adhesive bonding agents
Pit fissure sealant
Bonding of ceramic veneers
Cementation of crowns

Question 5

Resin matrix

Answer 5

Based on blend of aromic and/or aliphatic dimethacrylate monomers like bis-GMA and Urethane dimethacrylate

Question 6

What happens because of large molecular volume of monomers in matrix

Answer 6

Polymerization shrinkage is as low as 0.9% when combined with inorganic particulate fillers at levels up to 88% by weight

Question 7

Because of high viscosity of UDMA and bis-GMA what happens

Answer 7

It’s harder to blend and manipulate so it’s necessary to use varying proportion of low molecular weight highly fluid monomers like

Triethylene glycol dimethacrylate

Question 8

What happens when use smaller diluent monomers in matrix

Answer 8

They undergo greater polymerization shrinkage that generates shrinkage stress, causing marginal gaps and increase risk of leakage and partially offsetting advantage of bis-GMA

Question 9

Filler

Answer 9

Added to strengthen as well as to reduce shrinkage snf thermal expansion

Question 10

Fillers which impart radiopacity

Answer 10

Barium, strontium zirconium and zinc

Question 11

Quartz advantage

Answer 11

It’s chemically inert but very hard, making it abrasive to opposing teeth or restorations as well as difficult to grind into very fine particles
Therefore it’s hard to polish

Question 12

Refractive index of bis-GMA and TEGDMA

Answer 12

1.55 and 1.46

Question 13

Function of fillers

Answer 13

1.reduction of polymerization shrinkage
2. Reduction in thermal expansion and contraction
3. Decreased water sorption
4. Reinforcement
5. Control of workability/viscosity
6. Imparting radiopacity
7. Fluoride release