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BDS3 BMS - Dental Materials > 9. Dental composites: Aesthetic restorative materials > Flashcards

9. Dental composites: Aesthetic restorative materials Flashcards

1
Q

LOs

A
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2
Q

COMPOSITE RESTORATIVE MATERIALS

A
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3
Q

EGs of where composite restorative materials are used?

A
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4
Q
A
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5
Q

1
what are dental composites made from/ how many materials

2
what happens to the characteristics of the constituent materials on combining them

A

1
- 2 or more constituent materials
- that are not miscible and have
significantly different physical
or chemical properties

2
- On combining the two, the
resultant material has
characteristics different from
the individual components
- usu have better properties than individual components

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6
Q

COMPOSITE RESTORATIVE MATERIALS

Indications + contraindications?

A
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7
Q

1
reasons why composite is so widely used in restorative dent?

2 - EXTRA INFO
recommended types of resin composite for:
- Class 1&2
- Class 3&4
- cervical lesions

A
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8
Q

DENTAL COMPOSITES

Major + minor constituents

A
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9
Q

resin phase of dental composites

1
what do they consist of?

2
commonly used monomers in dental composites
- structure
- consistency (hard to mix with filler particles?)

A
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10
Q

DILUENTS

1
EG of diluent monomers

2
why may they be added to resin monomers (EG Bis GMA)

3
function of diluent monomers

A
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11
Q

Viscosity modifiers (diluent molecules)

1
function

2
What is the effect of cross linking

A
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12
Q

MINOR COMPONENTS

1
EGs

2
What does an inhibitor do?

3
EG of common inhibitors

A
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13
Q

FILLER PARTICLES IN DENTAL COMPOSITES

1
Usu made from?

2
How do the filler particles influence the properties of the composite

3
What size filler particles are usu used in composites

4
Advantages/ benefit of using filler particles in composites (IMAGE)

A
  • major constituent of dental composites

1
- quartz
- fusillica
- other glasses such as aluminosilicates or borosilicates

2
- type, conc + size of filler + particle size distribution all help determine the properties of the composite

3
- usu use smaller filler particles in dent composites to improve properties of composite

  • modern composites are all hybrid composites - blend of diff sized filler particles
  • can range from 5-10 microns and are blended with sub-micron particles
  • this blending allows improvement in efficiency of filler loading

4
(She said more info in lecture about why for each point but did not add)

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14
Q

SILANE COUPLING AGENTS

1
Why do we use silane coupling agents

2
How do they help this?

A

EXTRA INFO FOR UNDERSTANDING

  • dental composites comprise of an inorganic filler + organic polymer matrix
  • so there is no inherent affinity between these two distinct phases
  • it is v important to improve ashesion of the filler with polymer matrix to avoid debonding in service
  • to do so, molecules that are bifnucional such as silane coupling agents is used to treat the filler particles

IN RH image
- filler particles have been treated with this molecule - one end of molecule has a carbon carbon double bond
- other end has 3 hydroxyl groups attached to silicone
(This is commonly used silane coupling agent)

  • when you interact this molecule or condense it with inorganic particles , the hydrophilic end condenses with the inorganic particles
  • when polymerisation occurs, this group undergoes polymerisation

Overall
- have enhanced adhesion between the ceramic phase (inorganic phase) and organic phase

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15
Q

PHOTOINITIATORS

1
Most common one used? (Colour)

2
What colour and range of light does it absorb?

3
How does it work?

4
Does the colour of the photo-initiator effect the colour/ shade of the composite?

5
EXTRA

A
  • minor but important constituent in dental composites

4
No

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16
Q

Dental composites: SETTING REACTION

1
Type of reaction?

2
How may the free radicals be generated?

3
2 types of curing reactions

A

1
- free radical addition polymerisation reaction
- Methacrylates undergo addition polymerisation

2
- heat
- light
- chemical activation

3
A - CHEMICAL REACTION

B - PHOTOINITATORS

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17
Q

Dental composites: SETTING REACTION

1
What do chemically activated reactions comprise of

2
How do chemically activated reactions work?

A

1
- Two paste systems
- PASTE 1 = initiators such as benzoyl peroxide BPO
- PASTE 2 = Amine

2
- reaction starts as soon as 2 are mixed + produce free radicals + polymerisation commences
- limited working time (ISO standards = recommended of at least 90 seconds)
- rate of set is uniform throughout the bulk of the material causing a gradual rise in viscosity @ room temp

EXTRA
- ISO recommends that these materials should form a hard solid within 5 minutes at 37 degrees (as being set in mouth

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18
Q

Dental composites: SETTING REACTION

1
What do photo-initiated reactions comprise of

2
Disadvantage of camphorquinone

3
Alternatives to camphoriquinone

4
What is the matrix phase?

A

1
- One paste system
- photoinitiators such as camphorquinone
- amine activator in the same paste

2
- is a bright yellow solid present
- hard to obtain different shades

3
trimethylbenzoyl-diphenyl-phosphine oxide (TPO) is being currently tested as an alternative and some composites are using a combination of the two

4
- ‘Matrix’ is the phase formed on polymerisation of the methacrylate monomers
- weakest + least wear resistant phase
- can absorb fluids
- is responsible for shrinkage and thermal properties are of importance to suit dental applications

EXTRA
- don’t halve a limited working time
- viscosity does not increase until exposed to photoinitation
- so plenty of placing and manipulation time
- once composite exposed to photoinitation source, material sets V rapidly

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19
Q

CURING

1
Disadvantages of chemical activation
(HINT - when mixing)

2
Photoinitiation / light activation - what does the degree of the cure depend on?

A

(Other writing on page, not underlined = extra)

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20
Q

PHOTOPOLYMERISATION

1
When does the polymerisation reaction begin?

2
What causes the free radicals to form?

3
What happens after free radical formation?

4a
Free radical addition polymerisation can terminate by what 2 methods?

4b
And in this case what termination reaction occurs?

A

4a
- 2 free radicals combining
- by disproportionation of free radical

4b
- disproportionation of free radicals

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21
Q

PHOTOPOLYMERISATION

1
How can the extent/ degree of polymerisation be determined?

2
- what is this termed as?

3
- what is the usu % range of degree of polymerisation/ conversion (NEED TO KNOW STAT OR DELETE Q??)

A
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22
Q

PHOTOPOLYMERISATION

1
What usu forms on polymerisation of dental composites?

2a
What causes linear polymers to occur?
2b
And what causes cross linking to occur?

3
How does cross linking affect/influence dental composites?

4
What is Autoacceleration or Trommsdorrf-Norrish effect/Gel effect?

5
During Autoacceleration/ Trommsdorrf-Norrish effect/Gel effect there is a rapid increase in rate of polymerisation. How does this affect the temp?

A

5
can cause temp to rise if heat dissipation is not possible

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23
Q

PROPERTIES OF DENTAL COMPOSITES

A
  • affected by different factors
24
Q

EFFECT OF MONOMERS & FILLERS ON DC

1
How do monomers affect DC
(EG bISGMA, TEGDMA)

2
How do filler affect DC

A

1
- viscosity of the resin monomers: plays a significant role in degree of conversion

  • bISGMA
  • high molecular weight monomer
  • high viscosity
  • relatively low degree of conversion
  • diluents such as TEGDMA (low molecular weight)
  • greater rate of conversion
  • higher shrinkage
  • inferior mechanical properties (compared to bISGMA on polymerisation)

2
- amount of filler, geometry of filler particles + particle size also impact on polymerisation efficiency

25
Q

DC

1
How does DC effect properties of dental composites

2
What can you use to determine DC?

3
How does DC effect micro hardness?

4
Does higher DC mean better or worse mechanical properties?

5
How does increasing DC affect water uptake + monomer diffusion?

A
26
Q

DEGREE OF POLYMERISATION/ CONVERSION

What happens if DC is not adequate?

A

-

27
Q
A
  • type + amount of filler influences the mechanical properties
  • study from 2011
  • ## take home message = even with slight difference in filler content, there is a big difference in mechanical properties
28
Q

CROSSLINKING

1
Does cross linking affect physical properties of dental composites?

2
What does increasing the crosslinking lead to?

3
Do cross linked networks dissolve in solvents? What happens?

A
  • can affect aesthetics as will reduce interaction with surrounding fluids thus decreasing bacterial ingress or staining

EXTRA (Also mentioned in previous FCs)
- most dental composites contain viscosity modifiers or diluent molecules
= low molecular weight dimethacrylate monomers
- which can undergo polymerisation + cross link the network

29
Q

POLYMERISATION SHRINKAGE

1
What does the 2nd polymerisation shrinkage (contraction depend on)

2
Given that the resin is the same in a composite, will highly filled dental composites or lower filler content composites exhibit lower shrinkage? EG

A

1
- type of resin monomers used
- amount of filler particles used in a dental composite

2
- highly filled dental composites exhibit lower shrinkage than composites with low filler content

-EG. VISGMA (high molec weight monomer) will have relatively low shrinkage compared to low molec weigh monomers (eg. TEGDMA)

30
Q

POLYMERISATION SHRINKAGE

  • plays a significant role in restoration failure

1
How may it cause failure?

2
Why can marginal leakage / micro leakage cause restoration failure?

A

1
- shrinkage can compromise the marginal seal + rupture adhesive bonds made between the 2 restorative intervals

  • THIS CAUSES GAP FORMATION which can cause:
    * secondary caries formation
    * Marginal leakage
    * post op sensitivity

2
- oral fluids contain bacteria
- hence slow ingress of oral fluids can lead to ingress of bacteria
- bacteria form within these interfaces
- can cause post op pain OR marginal staining due to ingress of oral fluids (aesthetic failure of restoration)

31
Q

POLYMERISATION SHRINKAGE

How can we counteract the effects of polymerisation shrinkage?

A
  1. Dev of lower shrinkage composites
  2. Incremental placement

EXTRA
- manufactures have developed resins (eg??) that undergo ring opening addition polymerisation that shrink less
- phased out currently due to the net shrinkage is not much lower +
- mechanical properties are inferior to hybrid composites

32
Q

Random

A
  • hard to measure direct volumetric shrinkage during shrinkage hence no standards found to measure this
  • measuring shrinkage stresses allows us to obtain info on the stresses that are set up on post polymerisation
  • when composite is in unset phase it can flow in cavity hence no stress, but post setting stresses can form
  • depending on a cavity configuartaion, the flow of composite can compensate Shrinkage BUT if there is little free surface area of a material, flow is restricted thus resulting in larger stresses being generated
33
Q

SHRINKAGE + SHRINKAGE STRESS

1
What is C factor / configuration factor?

2

A

1
- ratio of bonded to free area can give an indication of the interfacial stresses that will be set up

2

34
Q

DEPTH OF CURE

1
What is depth of cure?

2
What should we do to avoid undercurring?

3
What does curing depth depend on?

A
  • TIME
  • if you cure over a few more seconds it will not harm but you don’t need to do it for more than the recommended time
35
Q

COMPOSITE INTERACTION WITH FLUIDS

What can it cause?

A
  • can cause loss of ionic specials - that is from the filler phase (not so common)
36
Q

CLINCAL CONSIDERATIONS
Summary

A
37
Q

CLINCAL CONSIDERATIONS
Summary

A
38
Q

COMPOMERS

A
  • essentially are like composites
  • additional component is the intro of aluminofluorosilicate glass or basic glasses
  • so that a secondary reaction can be effected such as an acid base reaction
  • if a composite could adhere to tooth tissue like Glass ionomers do then the compomer would have a superior property compared to composite
  • were not adhesive to tooth structure so still required a bonding agent

Currently phased out from clinical use Because there are no particulate advantages over other existing type of restorative materials

39
Q

COMPOMERS

Advantages and disadvantages

A
  • were widely used when they were launched
  • especially in children
40
Q

In PPT BUT not in lecture video

A
41
Q

In PPT BUT not in lecture video

A
42
Q

RECENT DEVELOPMENT IN DENT

A
43
Q

EGs of classes of materials not in current clinical use

A
  • Siluranes, obseranes =not in current clinical use
44
Q

NANOCOMPOSITES

1
Size of nano particles?

2
EG of nano particle

3
Properties of nanocomposites

A
45
Q

DATA ON DIFF TYPES OF COMPOSITES

  • Flexural Strength
  • Polish Retention
A

FLEXURAL STRENGTH

  • nano composite similar to hybrid composite
  • microfine is much lower
46
Q

DIFF COMPOSITES AFTER BRUSHING

A
47
Q

Benefits of high polish retention

A
48
Q

FLOWABLE COMPOSITES

MAKE Q

A
  • 1 of the principles of MI dent is to retain tooth struc as much as possible hence come across lots of smaller cavities
  • if you use dental composites, it may not be able to flow as well in a small cavity, hence may not be able to flow very well in a small cavity therefore adaptation to walls of cavity may be compromised

HENCE
- flowable composites were developed so that you could overcome the flow problems of hybrid composites

HOWEVER FLOWBALE COMPOSITES GIVE RISE TO (IMAGE)

49
Q

FLOWABLE COMPOSITES

1
why were they developed?

2
How was this achieved?

3
what does doing this result in?

4
how’re these problems being overcome/ recommendations

A
  • so that you could overcome the flow problems of hybrid composites
  • to have a greater flow + lower viscosity

2
- by reducing the amount of filler in a hybrid composite
- approx 20-25%lower filler content than a hybrid composite

3
IMAGE

4
- recommended more as liners and fissure sealants due to the problems and small restoration
- not really for big restorations

50
Q

FLOWABLE COMPOSITE vs HYBRID COMPOSITES

1
Do flowable or hybrid composites have better mechanical properties?
Why?

A
  • hybrid composites have better mechanical properties
    BECAUSE
  • less filler in flowable composites hence rigidity is lower
51
Q
A
52
Q

PRE-WARMING OF COMPOSITES

1
Why may we prewarm hybrid composites?

2
Why would heating hem cause this change?

A
53
Q

How do we pre-warm composites?
What temp do they heat to?

A
  • using calset heating device
  • can heat to 3 diff temp: 27, 54, 68 degrees

EXTRA
- usu when heat don’t reach high temp of 68 degrees
(EG when heat to 60, the temp in composite was us around 45 or so)

54
Q

PREWARMING COMPOSITES STUDIES

Make Q’s

A
55
Q

Pre-warmed composite resin and the fit of ceramic restorations STUDY

MAKE Q’s

A
56
Q

BULK FILLED COMPOSITES

More recent development

Make Q

A
57
Q
A

BDS3 BMS - Dental Materials (12 decks)

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