Biomaterials Exam - Composite, Glass Ionomers, Sealants, and Adhesives

Question 1

What makes up a composite?

Answer 1

hybrid material of an organic phase (resin) and an inorganic (filler) phase

Question 2

What is the role of resin in a composite?

Answer 2

helps processing and handling

Question 3

What is the role of filler in a composite?

Answer 3

helps modulus and wear resistance

Question 4

What are the characteristics of organic polymers?

Answer 4

tougher, but not as strong or wear resistant

Question 5

What are the characteristics of inorganic materials?

Answer 5

strong and wear resistant, but brittle

Question 6

What type of reaction occurs in order to cure composite?

Answer 6

cross-linking reaction

Question 7

What triggers the cross-linking of polymers when composite is cured?

Answer 7

visible light

Question 8

What are 2 ways to change the density of cross-linking?

Answer 8

• number of cross-linking groups

- degree of cross-linking or degree of curing

Question 9

What are the 4 components of composite resin?

Answer 9

• resin system
• filler
• bonding agent
• visible light initiator

Question 10

What are the 3 types of fillers?

Answer 10

• micron (fine)
• nano (microfine)
• nano (microfine) in polymer matrix

Question 11

What are the benefits of having a smaller filler size?

Answer 11

• teeth are nanocomposites
• smaller fillers should have better wear properties
• allows for better polishing and finish
• expectation of better mechanical properties

Question 12

What is the difference between a nano (microfine) filler and a nano (microfine) filler in a polymer matrix? In other words, which has a tendency to aggregate? Which has poorer filler to matrix bonding?

Answer 12

• nano (microfine) filler has a tendency to aggregate

- nano (microfine) filler in a polymer matrix has poorer filler to matrix bonding because there is no coupling agent

Question 13

What is a coupling agent?

Answer 13

a chemical substance that can react with the resin and the filler and enhance filler-to-matrix bonding

Question 14

When a composite polymerizes, does it swell or shrink? Why?

Answer 14

shrink because there is a density change when it goes from monomer to polymer

Question 15

What are the clinical consequences of polymerization shrinkage?

Answer 15

• causes stress on the tooth structure

- can cause microleaks and lead to secondary caries

Question 16

What are the components of glass-ionomer cement?

Answer 16

• acidic polymer in aqueous solution
• basic glass
• water
• modifiers (+) tartaric acid (*don’t need to know?)

Question 17

What type of reaction cures glass-ionomer cement?

Answer 17

acid/base reaction

Question 18

What type of bond is formed between polyacids and basic glass in the setting of glass-ionomer cement?

Answer 18

salt bridges

Question 19

Explain the steps of the setting process of glass-ionomer cement.

Answer 19

• glass-ionomer mix is applied
• acid matrix dissolves periphery glass
• glass releases ions: Ca, Al, and F
• divalent Ca ions quickly chelate with acid polymer chains
• in the next 24-72 hours, Al replaces Ca which increases the strength and F is released
• acid side groups can also chelate with glass and hydroxyapatite

Question 20

Why does the glass-ionomer cement become stronger when Al replaces Ca in the salt bridges?

Answer 20

because Ca has a +2 charge so it can bind 2 of the acid or base together, but Al has a charge of +3 so it can bind 3

Question 21

Is a coupling agent required in the setting reaction of glass-ionomer cement?

Answer 21

No, but it is required in the composite setting reaction

Question 22

What is released during the setting of glass-ionomer cement?

Answer 22

fluoride and sodium which continue to be released over time

Question 23

True or false: Glass-ionomer cement is a water-based restorative material.

Answer 23

true

Question 24

What are some similarities or differences between adhesives and composites?

Answer 24

Similarities:
- light cured
- made of dimethacrylates (?)
Differences:
- composite is hydrophobic while adhesives are hydrophobic and hydrophilic
- adhesives may be unfilled (or lightly filled)

Question 25

What is the difference between a macrotag and microtag of an adhesive?

Answer 25

• macrotag - interprism (between prisms) resin penetration

- microtag - intraprism (within prism) resin penetration

Question 26

Which side of the adhesive (hydrophilic or hydrophobic) binds to the enamel of the tooth? Which side binds to the composite?

Answer 26

• hydrophilic binds to the tooth

- hydrophobic binds to the composite

Question 27

What are some similarities and differences between sealants and composites?

Answer 27

Similarities:
- has a BisGMA/TEGDMA system
Differences:
- no filler in sealants

Question 28

What is the oxygen inhibition layer? With what type of material is this more of a problem?

Answer 28

When a material is being cured with radical polymerization, free radicals are generated in order to form cross-links. But oxygen can terminate the free radicals so the top layer that is exposed to the atmosphere may not be cured. This is a problem with thin layers like sealants.