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Dental Materials > Requirements of Filling Materials > Flashcards

Requirements of Filling Materials Flashcards

1
Q

Conditions which need restoring

A
  • fracture
  • caries
  • erosion/abrasion
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2
Q

Fracture is caused by…

A

trauma

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3
Q

Caries is caused by…

A

bacteria

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4
Q

Erosion/abrasion is caused by …

A
  • acids
  • wear
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5
Q

Properties of enamel

A
  • outer shell
  • ceramic (apatite) which is hard but brittle
  • relatively translucent
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6
Q

Properties of dentine

A
  • inner layer
  • made of composite (apatite and collagen polymer)
  • softer and tougher than enamel
  • more opaque too
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7
Q

Requirements of direct filling materials

A
  • done chairside
  • mouldable to cavity (initially fluid and plastic)
  • harden and stregthen during setting (resist mechanical forces)
  • bond to tooth
  • tooth colour
  • protect pulp how enamel and dentine would (temp and electrical changes)
  • biocompatible
  • mechanically stable (fatigue, stiffness etc)
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8
Q

What aesthetics are needed from fillings initially?

A
  • patients want white appearance but enamel rarely white
  • match shade with possible materials (not with amalgam, gold etc)
  • enamel is translucent so opaque materials don’t look lifelife
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9
Q

What is needed long term from filling materials aesthetically?

A
  • needs to be stable over time
  • look the same if not much different from when it was placed
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10
Q

List factors that affect aesthetics of fillings over time

A
  • roughness/gloss
  • location
  • stains
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11
Q

How does roughness affect aesthetics of fillings?

A
  • scratches can lead to gloss loss
  • micro-organisms colonise rough surfaces
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12
Q

How does location affect aesthetics of fillings?

A
  • forces different anterior and posterior
  • aesthetics more essential anteriorly
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13
Q

How do stains affect aesthetics of fillings?

A
  • depends on material
  • composites stained by food/drink
  • amalgams may tarnish
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14
Q

Regarding thermal protection, what do materials need to be?

A
  • insulators
  • low conductivity and diffusivity in enamel and dentine to protect pulp from hot and cold
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15
Q

Are amalgam and gold insulators?
Solution?

A
  • no - conductors
  • in deep fillings, may need insulator cement
  • acts as a barrier to pulp
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16
Q

Are composites insulators?

A
  • yes
  • cement may not be needed
  • some dentists will use it though
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17
Q

List protective properties of filling materials

A
  • non-toxic and non-irritant
  • cariostatic
  • adhere to tooth tissue
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18
Q

What kind of reactions can be had to filling materials?

A
  • setting reactions - avoided if toxic components kept to safe levels
  • individual allergies - common so need a full history
19
Q

What does it mean for a filling material to be cariostatic?

A
  • prevents caries
  • some release fluoride
  • antibacterial agents incorporated in filling
20
Q

Why is it good for materials to adhere to tooth tissue?

A
  • allows conservative preparation
  • only remove carious tissue and retain sound tooth
  • reduces microleakage - bond acts as a barrier
21
Q

Explain dimensional changes when material sets

A
  • shrinkage can cause stress on adhesive bond and effect retention and microleakage
  • expansion causes stress development in tooth - filling extruding beyond margins or fracture of tooth
22
Q

The mouth is an aqeous environment so filling materials ideally shouldn’t do what?

A

absorb water

23
Q

Water diffusion and absorption can lead to…

A
  • hydrolysis
  • softening
  • leaching
  • staining
24
Q

How does hydrolysis occur?

A
  • filling components react with water
  • weakening filling
25
Q

How does softening occur?

A

water can act as a plasticiser

26
Q

How does leaching occur?

A
  • components can diffuse from filling into oral cavity
27
Q

Filling materials need to withstand temp variations.
2 ways you’re exposed to this

A
  • hot and cold food/drinks
  • thermal cycling (5-60 degrees)
28
Q

Filling materials need to withstand pH variations. How are they exposed to this?

A
  • acidic with plaque (4 ish) and drinks (1-3)
  • alkaline (medicine and toothpaste pH 12)
  • solvent exposure (foods like peppermint oil, alcohol)
  • corrosion (galvanic effects/medals)
29
Q

Thermal expansion and contraction can cause large dimensional changes. Explain issues

A
  • contributes to stress at interface
  • can lead to the interface failing
  • may have a ‘pump’ effect
  • can force stains and bacteria around margins
  • secondary caries may initiate away from surface
30
Q

Larger cavities experience … changes

A

greater

31
Q

Fillings must withstand mechanical stress. Explain

A
  • high stress leads to fracture
  • low stress over time - fatigue
  • sudden, rapidly applied stress - impact
32
Q

How do differences in rate of strength development occur?

A
  • setting time (can be hours/days for strength)
  • setting mechanisms (can speed it up with light curing etc)
33
Q

Abrasive factors on teeth

A
  • hardness
  • two body - opposing teeth
  • three body - food and/or toothpaste
  • solvents causing softening
34
Q

How does bacteria affect fillings?

A
  • breakdown of resins
  • leads to weakening
35
Q

Should fillings be radio-opaque?

A
  • yes
  • caries is radiolucent
  • radiolucent fillings will confuse diagnosis
36
Q

Polymer-based materials e.g composites - radio-opaque?

A
  • made from low atomic number elements
  • not radio-opaque
  • need a radio-opacifier (more opaque but lowers strength)
  • compromise needed
37
Q

What is taken into consideration with working and setting time?

A
  • sufficient time to mix and place
  • long ST is uncomfortable for patient
38
Q

Mixing and setting with 2 components in material

A
  • setting starts by mixing
  • technique sensitivity possible
  • mix by hand - spatula on pad
  • mechanical mixing - capsules in a machine
39
Q

Mixing and setting with one component materials

A
  • lower technique sensitivity
  • setting starts by external source like light
40
Q

The ideal filling material should be …

A
  • easy to mix and place
  • should be low waste
  • safe to mix in clinic
41
Q

The ideal application procedure should be …

A
  • easy to sculpt
  • transferred by spatula and syringe
  • single-dose packets or as easy
42
Q

Ideal technique sensitivity for materials

A
  • moisture control - does moisture stop setting
  • less stages the better - more stages requires more time
43
Q

Can 1 material do everything for cavities?

A
  • ideally
  • class 1 to 5 cavities
  • small and large

Dental Materials (17 decks)

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