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Module 6 - Dental Materials > Fibre Reinforced Composites (FRC) > Flashcards

Fibre Reinforced Composites (FRC) Flashcards

1
Q

What is a fibre reinforced composite? What is it composed of?

A
  • Synthetic material (polymer & fibres).
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2
Q

What is the function of the fibres in a fiber reinforced composite?

A

Fibres SUPPORT the composite.

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3
Q

4 things that can affect the restoration?

A
  1. Pathogen microbes (S.mutans, Lactobacilli which produce ACID).
  2. Humidity (from saliva).
  3. Mechanical load - direction of biting force (crash, separate, debond).
  4. Appearance.
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4
Q

3 things that can happen when forces are applied to a restoration.

A
  • Separate the restoration/ material itself separates.
  • Crash restoration (and break it).
  • Restoration debonds.
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5
Q

Why were carbon/graphite fibres not used for long?

A
  • Compromise aesthetics as they were black in color.
  • NOT IN USE.
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6
Q

3 different types of fibres which can be/ were used for FRCs?

A
  • Carbon graphite fibres.
  • Aramid fibres.
  • Glass fibres.
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7
Q

What are/ were aramid fibres used for?

A
  • Used for denture reinforcement.
  • Aesthetic concerns (difficult to achieve polished surface) hence NO LONGER IN USE.
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8
Q

How many types of glass fibres are there?

A
  • 7 types: A, C, D, E, E-CR, R, S glasses.
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9
Q

What are the 3 most common types of glass fibres in dentistry?

A

E, R and S glasses

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10
Q

What can be used to enrich the surface of glasses (2 options)

A
  • Boron
  • Calcium
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11
Q

What can be done to improve the properties of E glasses/fibres?

A
  • Add Boron Oxide (B2O3).
  • Reduce CaO

Make it MORE RESISTANT TO ACID ATTACKS.

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12
Q

What is the effect of fillers on fibres?

A

Can compromise fibre strength.

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13
Q

What must fibres be?

A

Radiopaque.

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14
Q

What are the 2 types of polymers?

A
  • Linear/ THERMOPLASTIC.
  • Cross-linked/ THERMOSET.
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15
Q

2 examples of linear polymers?

A
  • Methyl methacrylate (MMA).
  • Poly methyl methacrylate (PMMA).
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16
Q

3 types of cross linked polymers?

A
  • Ethyleneglycol dimethacrylate (EGDMA).
  • Bisphenol-A-glycidil dimethacrylate (bis-GMA).
  • epoxi resins
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17
Q

What polymers are included in dental resin systems?

A
  • bis-GMA.
  • TEGDMA (triethileneglycol dimethacrilate)
  • UDMA (urethane dimethacrilate systems).
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18
Q

What is a semi-interpenetrating polymer network (semi-IPN) made of?

A

Combination of a LINEAR with a CROSS LINKED polymer.

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19
Q

4 advantages of semi-IPN?

A
  • Better clinical handling properties.
  • Better bonding to indirect restorations, posts and veneers.
  • Higher toughness.
  • Helps bond the fibres to the matrix.
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20
Q

What are fibres impregnated with? What are its 3 effects?

A
  • RESIN (PMMA).

Affects:
- Surface wetting properties (of fibres).
- Distance of individual fibres (from each other).
- Viscosity (of resin material).

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21
Q

What is the preimpregnation method?

A
  • PMMA is dissolved in a high evaporative solvent.
  • Solvent evaporates, leaving fibres impregnated with PMMA.
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22
Q

What are fibres coated with (2)?

A
  • Antistatic compounds.
  • Coupling agents - SILANES.
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23
Q

What are silanes?

A

Coupling agents.

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24
Q

What are the 3 effects of silanes?

A
  • Help with ADHESION (create bonds not available in nature).
  • Improve the surface wetting of the fibres.
  • Enable the chemical adhesion between the fibres and polymer matrix.
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25
Q

What are the 4 different directions of fibres? What will this affect?

A

Affects MECHANICAL PROPERTIES of the FRC.

  • Continuous unidirectional.
  • Continuous bidirectional.
  • Continuous random orientated.
  • Discontinuous random orientated (short).
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26
Q

What are unidirectional fibres?

A

All fibres in ONE SINGLE DIRECTION embedded on the resin.

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27
Q

What are the traits of unidirectional fibres (3)?

A
  • Suitable for applications with HIGHER STRENGTH ALONG A SPECIFIC AXIS.
  • Improved strength in the direction of the fibres, reduced strength in all other directions.
  • Reduced strength in all other directions
28
Q

Applications of unidirectional fibres?

A
  • Posts.
  • Fixed prosthodontics (improved tensile strength).
29
Q

What are bidirectional fibres?

A

All fibres in BOTH DIRECTIONS embedded on the resin.

30
Q

What are the traits of bidirectional fibres?

A
  • Improved STRENGTH and STIFFNESS in BOTH directions.
  • Used when both FLEXURAL and TENSILE strength are required.
  • Increase the LOAD BEARING CAPACITY and the RESISTANCE TO FRACTURE.
31
Q

Applications of bidirectional fibres?

A
  • Dental bridge frameworks
  • Splints
  • Removable dentures
32
Q

What are random orientation fibres?

A
  • Fibres randomly dispersed.
33
Q

What are the traits of random orientation fibres?

A
  • Anisotropic properties: different properties in different directions.
  • Cost effective for short term solutions.
34
Q

Applications of random orientation fibres?

A

Provisional restorations

35
Q

What are woven fabric fibres?

A
  • Interlacing fibres in specific pattern (plain/ twill weave).
  • Well controlled and evenly distributed fibre alignment.
36
Q

What are the traits of woven fabric fibres?

A
  • Enhanced mechanical properties
37
Q

Applications of random orientation fibres?

A
  • Orthodontic appliances.
  • Indirect restorations.
38
Q

3 properties of FRC?

A
  • Biocompatible.
  • Radiopaque.
  • High modulus of elasticity (similar to natural tooth structure).
39
Q

3 advantages of having modulus of elasticity similar to natural tooth structure?

A
  1. Reduces stress.
  2. Helps with load distribution.
  3. Minimizes risk of fracture.
40
Q

The more fibres embedded on the composite…

A

the better strength capabilities and stiffness.

41
Q

Too many fibres…

A

Compromise the FLOWABILITY of the composite and affect its placement onto the cavity.

42
Q

Longer fibres…

A

Transfer stress more efficiently yet have DECREASED mechanical properties.

43
Q

Shorter fibres…

A

Help with MATERIAL HANDLING and have LESS RISK of fibre AGGLOMERATION.

44
Q

Factors affecting the success of FRC?

A
  1. Fiber alignment.
  2. Restoration design.
  3. Volume fibre fraction.
  4. Fiber length.
  5. Interfacial bonding.
  6. Curing and polymerization
  7. Clinical application
45
Q

What is interfacial bonding? What is sued to secure this?

A
  • Bind between the fibres and the matrix.
  • SILANES
46
Q

5 types of bonding mechanisms between fibres and matrix?

A
  1. Mechanical interlocking - improved stress distribution and load transfer.
  2. Chemical bonding - improved composite strength and resistance to debonding.
  3. Wetting and capillary action - improved stress distribution and load transfer.
  4. Interdiffusion. - improved resistance to debonding.
  5. Hybrid layer formation. - improved mechanical properties.
47
Q

Why is curing and polymerization important?

A
  • Avoid internal voids or defects within the composite.
48
Q

Advantages or FRC restorations?

A
  1. Easy manipulation.
  2. Improved flexural strength, fatigue strength, elastic modulus and bond strength.
  3. Mechanical strength and elastic modulus close to the dentine.
  4. Metal free, possible to use in cases of allergic reactions.
  5. High aesthetics.
  6. Cost effective.
  7. Minimal lab work required.
  8. Easily repairable.
49
Q

Limitations of FRC.

A
  1. Research required for long term clinical performance.
  2. Humidity of oral cavity may degrade/ weaken the interface between the matrix and fibres leading to FAILURE.
  3. Easy to fracture and delaminate.
50
Q

5 clinical uses of FRC?

A
  • Removable dentures.
  • Fixed dental prostheses (crowns, bridges, inlays, onlays).
  • Root canal posts.
  • Splints (NOT removable ones - perio/ortho/trauma).
  • Direct restorations (fillings).
51
Q

2 ways in which acrylic dentures can be reinforced?

A
  1. Metal.
  2. Fiber reinforced composite.
52
Q

2 techniques of using FRC to reinforce acrylic dentures?

A
  • Total fibre reinforcement: full denture, NOT IN USE ANYMORE.
  • Partial fibre reinforcement: weakest part.
53
Q

5 steps to embedded FRC into acrylic denture?

A
  1. Mark dots on model where holes will be placed on acrylic denture to allow space for FRC.
  2. Cut desired holes into acrylic.
  3. Cut desired size and shape strips of fibres.
  4. Embed fibre into polymer.
  5. Fit embedded fibre onto acrylic and polymerize.
54
Q

Two advantages of FRC for fixed dental pros?

A
  • Minimally invasive technique (more CONSERVATIVE).
  • Be made straight after extractions.
55
Q

Provisional and permanent composition of FRC for fixed dental pros.

A
  • Provisional: resin made with fibre reinforcement.
  • Permanent: framework made with FRC, veneered with composite (direct, semidirect, indirect).
56
Q

5 steps to making an immediate dental bridge chairside.

A
  1. Place a RUBBER DAM.
  2. Use a FIBER REINFORCED COMPOSITE to make a strip connecting the 2 abutment teeth (woven pattern - 0.5/0.75mm composite layer).
  3. Wet composite.
  4. Polymerize fiber.
  5. Add a acrylic fake tooth/ natural tooth cutting the root.
57
Q

Questions:

A
  • Do semi IPN and silanes have the same effect? (help bond fibres to matrix).
  • is the immediate fized bridge method (with FRC used as a strip) provisional or permanent?
  • WHat is delamination of composite/ post? (disadvantages of pre fabricated posts).
58
Q

What is the fibre pattern of FRC used in direct dental bridge?

A

Woven pattern.

59
Q

3 advantages of pre fabricated root canal posts?

A
  1. Suitable elastic modulus (less fractures/ failures).
  2. Good aesthetics (as white).
  3. Direct technique/ faster.
60
Q

5 disadvantages of pre fabricated root canal posts?

A
  1. A lot of dentine might be removed for placement + burs are quite tapered which can weaken the root.
  2. Adhesion issues/ marginal breakdown of bonding.
  3. Interfacial fracture propagation (inadequate support from the post due to the post not being well adapted and requiring a thick layer of cement).
  4. Delamination of composite
  5. Delamination of post (plastic deformation).
61
Q

4 advantages of individually/ custom root canal posts?

A
  1. Greater resistance under loading.
  2. Higher bond strength.
  3. Higher fatigue resistance.
  4. Less amount of cement hence canal filled with FRC/ INCREASED FIBRES.
62
Q

7 steps to making an individual root canal post?

A
  1. Place RUBBER DAM.
  2. Prepare fibre to the correct size for the tooth to be restored.
  3. Place bonding systems into canal (which has been prepared with drills) to create a composite matrix.
  4. Place composite into the root.
  5. Place wetted fibres into the canal.
  6. Polymerize fibres and composite.
  7. Place a composite core and prepare for a crown around this structure.
63
Q

1 advantage and 2 disadvantages of FRC splints?

A
  • Use for ortho/ perio/ trauma.

Advantage: no additional tooth preparation.

Disadvantages: Wear/ debonding.

64
Q

6 advantages to using FRC for direct restorations/ fillings/ core buildups?

A
  • Improved mechanical properties.
  • Reduced polymerization shrinkage.
  • Improved toughness.
  • Improved fatigue resistance.
  • Improved scattered/ conduction of light (better POLYMERIZATION).
  • Improved aesthetics.
65
Q

What type of fibres of FRC should be used for direct restorations/ fillings/ core buildups?

A

Short fiber reinforced composites.

66
Q

2 types of FRCs with fibres already embedded in composite? How thick can they be placed? What are they replacing?

A
  • SDR
  • FeelTech bulk fill.
  • can place layers up to 5mm without suffering typical shrinkage of the composite.
  • Intended to replace the dentine.

Module 6 - Dental Materials (3 decks)

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