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DS1102 > Week 5 - Dental Materials > Flashcards

Week 5 - Dental Materials Flashcards

1
Q

What are the properties of enamel

A

translucent, brittle, hardest material in the body 300-500 KHN, permeable

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2
Q

What is the composition of dentine

A

70% mineral

10% water

20% organic matrix

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3
Q

What are the characteristics of dentine

A
  • more suspectable to demineralisation
  • More opaque and resilient that enamel
  • hardness is 50-70 KHN
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4
Q

What scale analyses colour

A

Munsell scale

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5
Q

What are the 3 independent parameters of the munsell scale

A
  • Wave length (hue)
  • Intensity (chroma)
  • Brightness
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6
Q

Out of hue, chroma and brightness which ones are inherent properties and which ones can be altered

A

Hue and chroma are inherent properties meaning that they cannot be change
Brightness can be altered by surface polishing

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7
Q

How could hue and chroma be changed

A

Change can occur intrinsically be degradation or transformation in the molecules or extrinsically absorption of stains

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8
Q

The chroma of a tooth comes from what

A

dentine - and the thickness and opacity of the overlying enamel determines how much chromatic influence the dentin has

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9
Q

What is value

A

the total amount of light returned from an illuminated object and is influenced by enamel thickness and quality

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10
Q

What is fluorescence

A

the property of a material to absorb light of a particular wavelength and then to emit light of a different wavelength and therefore colour

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11
Q

does dentin or enamel have greater fluorescent properties

A

dentine due to organic particles

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12
Q

What is metamerism

A

objects which match each other under one set of light conditions but mismatch under another as the light has different spectral properties. Metamerism can have an effect on the appearance of a tooth o restoration.

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13
Q

What are the components of composite resin

A
  • organic resin matrix
  • inorganic filler
  • coupling agent
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14
Q

What is the organic resin matrix comprised of

A
  • monomer
  • viscosity controllers (MMA, EDGMA, TEGMA)
  • Inhibitor (hydroquinone)
  • Activator and initiator
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15
Q

What are the monomers of the organic resin matrix

A
  • Bis-GMA
  • UDMA
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16
Q

What length chain monomers does the organic resin matrix have

A

*longer chain monomers are used over shorter ones because longer chain monomers shrink less

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17
Q

What is the inhibitor used in the organic resin matrix

A

hydroquinone

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18
Q

What are the activators and initiators in the organic resin matrix

A
  • chemical cure (aromatic tertiary amine + BPO)
  • Light cure (e.g. camphorquinone + Aliphatic amine)
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19
Q

What are inorganic filler particles used for

A
  • reduces polymerisation shrinkage
  • reduce coefficient of thermal expansion (you want it close to the one of enamel 11ppm/oC)
  • improve mechanical properties (strength, elastic moduls, harness, wear resistance)
  • Provide radiopacity
  • Control aesthetics
20
Q

What are coupling agents

A

Spacer group which acts as a strong and durable link between 2 materials which have no natural affinity for each other
e.g. filler particles and the resin particles

21
Q

What is an example of a coupling agent

A

silane coupling agent
y - methacryloxyypropyltrimethoxysilane
y-MPTS

22
Q

What are factors which affect the mechanical properties of resin composites

A
  • porosity
  • Filler content
  • Type of filler
  • Efficiency of filler resin coupling
23
Q

What are the 2 types/methods of resin composites

A
  • chemical cure composite - 2 paste composite technique
  • Visible light cured composite technique
24
Q

What are the 2 components of the 2 paste composite technique

A
  • catalyst tertiary amine paste
  • Base benzoyl peroxide base
25
Q

What are the problems with the 2 paste composite technique

A
  • limited mixing and working time
  • mixing introduces air into the mixture forming porosities which will reduce the mechanical strength and alter properties of the material
  • Porosities reduce compressive strength and fatigue limit
26
Q

What wavelength is the effective initiation of VLA composite

A

450-500nm
with maximum output of the machine at 460-480nm which is harmful to the eyes

27
Q

What is the recommended depth of cure2

A

2mm
max 3-4mm but not recommended

28
Q

What is the relationship between intensity of light and increasing distance

A

exponentially decreases

29
Q

does increasing exposure time increase curing depth

A

no

30
Q

What are the different light curing units

A
  • Halogen light (quartz tungsten halogen)
  • Blue LED (460-480nm): energy efficient, less heat emitting, portable, rechargeable, easy cross infection controlled, long service life but narrow spectrum
  • Argon laser (high intensity): greater depth and degree of cure in a shorter time but may compromise integrity of tooth composite interface and is very expensive, but narrow spectrum
  • Plasma (xenon) arc light: intensity and compromised marginal integrity = argon laser, but low cost
31
Q

How long do you cure each VLC resin composites

A

> 40 sec

32
Q

What light source do you used to set VLC resin composites

A

High blue light intensity light source (470-480nm)

33
Q

What are the conventions of VLC resin composites

A
  • Place the light tip as close as possible
  • Ensure that the light tip does not contaminate
  • use transparent matrices and wedges when possible
  • apply curing light on the bonding side not the free surface as much as possible
  • Bonding via oxygen inhibited surface layer
34
Q

What are recommendations to deal with polymerisation shrinkage

A
  • Composite ideally should be used when all the margins are in enamel
  • herringbone effect
  • Incremental placement and through the tooth curing can eliminate gap formation under light cure resin
35
Q

What does incremental packing do

A
  • minimise effects of polymerisation shrinkage
  • reduce stress at the interface
  • ensure complete cure of each increment
36
Q

What is the composition of filler particles

A
  1. Quartz (hardest particle)
  2. Fused Silica
  3. Silica-based glass particle
37
Q

What are the different types of filler methods

A
  • microfilled resins (submicron fillers)
  • traditional composites (macrofilled)
  • Hybrid composite resins
38
Q

What are the different types of composite

A
  • conventional resin composites
  • packable composites
  • flowable composites
  • bulk fill composite
39
Q

What is absorption

A

water sorption by resin matrix

40
Q

What is adsorption

A

water sorption onto the particle resin interface as a result of poor bonding in between

41
Q

What will absorption and adsorption cause

A

discolouration or the restoration at its margin weakening its structure

42
Q

What is the biocompatibility of Bis GMA

A

can induce change in oestrogen sensitive organs

43
Q

What is the biocompatibility of MMA and TEGGMA - what can it cause

A

cytotoxicity and hypersensitivity

44
Q

What are the concerns with nanoparticles

A

the particles can accumulate in the lungs, pass through skin/mucosa enter systemic circulation and accumulate in different organs passing through cell membrane

45
Q

What can cause the following type of restoration discolouration especially at the margins

A

adsorption and absorption

46
Q

Which type of resin causes less polymerisation shrinkage due to the higher surface area of the filler

A

microfilled resins
smaller filler particles means larger surface area

DS1102 (30 decks)

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