Chapter 4 J: Composite Resins

Question 1

Why was there an initial rejection of the usage of composite resin in the posterior sectors?

Answer 1

• the effectiveness of the previous materials
• the already known problems of cr

Question 2

What are the 5 components of CR?

Answer 2

1. Organic matrix
2. Inorganic particles
3. Binding agents
4. Polymerisation initiator
5. Other: des, radio-opaquers

Question 3

Bis-GMA polymer is a?

Answer 3

Organic matrix

Question 4

Silicon dioxide is a?

Answer 4

Inorganic particle that improves physio-chemical properties

Question 5

Silanes are?

Answer 5

Binding agents

Question 6

Camphorquinone and lucirin are?

Answer 6

Polymerisation initiators

Question 7

How do camphorquinone and lucirin work and what’s their disadvantage?

Answer 7

• camphorquinone has a yellow color, activated by the light in the dental chair
• lucirin is transparent and is activated by a different wavelength
• when mixed together they produce a white color but the properties become worse

Question 8

Problems with CR could be due to the ___ or the ___?

Answer 8

Material or technique

Question 9

What causes the fatigue of CR?

Answer 9

Due to the repeated impact of the antagonist cusp and thermal changes (expansion and contraction)

Question 10

What causes wear of the CR? And how is it being improved?

Answer 10

• due to occlusion, brushing, and food (acidic)
• diminished due to improvement of inorganic fillers (hybrids)

Question 11

What is the most serious problem of CR?

Answer 11

Polymerisation shrinkage

Question 12

How much of the mass volume shrinks during polymerisation?

Answer 12

2.7-7.1%

Question 13

Where is most of the shrinkage?

Answer 13

On the surface

Question 14

Consequences of polymerisation shrinkage are?

Answer 14

• micro-filtration
• gap formation
• cuspal deflection
• enamel cracks and fractures

Question 15

Gap formation causes?

Answer 15

Hypersensitivity

Question 16

Pulp necrosis is due to __ not CR?

Answer 16

Bacterial contamination

Question 17

Degree of conversion is?

Answer 17

The percentage of polymerised resin
Degree of polymerisation
There’s always unpolymerised monomer

Question 18

3 factors that affect degree of conversion:

Answer 18

1. Oxygen (CR touching oxygen can’t polymerise)
2. Fillers (microfillers should be polymerised into thinner layers)
3. Dyes (the darker —> the harder to polymerise, less light passes through)
   OFD

Question 19

Microfillers improve:
A. Color change
B. Resistance
C. Surface roughness
D. Biocompatibility

Answer 19

C

Question 20

Self-cured resins tend to?

Answer 20

Darken

Question 21

Light cured resins tend to?

Answer 21

Clarify

Question 22

Filling defects are most common in?

Answer 22

Class II

Question 23

Defects of polymerisation/curing depend on: (3 factors)

Answer 23

1. State and quality of light (470nm)
2. Obstacles in light’s path (Enamel is more translucent than dentin)
3. Application technique: it’s convenient to apply the focus as close as possible and in a perpendicular position (lambert’s law)

Question 24

Possible reasons for fracture of material

Answer 24

1. Insufficient thickness
2. Excessive occlusion (bruxists)
3. Inadequate support
   EII

Question 25

T or F: CR have a similar thermal conductivity compared to dentin and enamel

Answer 25

T

Question 26

What causes hypersensitivity with CR?

Answer 26

Movement of fluids within the dentinal tubules

Question 27

How to avoid bacterial contamination

Answer 27

Removing all carious lesions
Achieving a perfect seal

Question 28

Composite was used in the anterior sector since the?

Answer 28

60’s