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CSA > Tooth Coloured Filling Materials > Flashcards

Tooth Coloured Filling Materials Flashcards

1
Q

What is composite?

A

A product with at least two distinct phases, purpose to combine two or more materials to produce one with superior properties. Contains inorganic filler and an organic binder.

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2
Q

Advantages of composite

A 
Aesthetics
Conservation of tooth structure
Adhesion to tooth structure
Low thermal conductivity
Alternative to amalgam
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3
Q

Disadvantages of composite

A 
Technique sensitive
Polymerisation shrinkage
Marginal leakage
Secondary caries
Postoperative sensitivity
Decreased wear resistance
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4
Q

How does composite set?

A 
Free radical addition polymerisation
Activation by chemical organic amine and organic peroxide or light camphorquinone and blue light (450-490nm) breaks into free radicals
Initiation
Propagation
Termination
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5
Q

What are polywave light cures?

A

They have two photo initiators (one at 410nm and 470nm wavelengths)

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6
Q

What is polymerisation shrinkage?

A

Where the polymer occupies a smaller volume than the monomer.

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7
Q

What are the monomers in composite?

A

Bis-GMA
UDMA
TEGMA

All have c=c bonds at either end, which is why they are dimethacrylates

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8
Q

What do monomers do?

A

Bind filler particles together

Provides workability

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9
Q

What are the properties of Bis-GMA?

A 
Extremely viscous (large benzene rings)
Lowered by adding TEGDMA
- freely movable
- increases polymer conversion
- increases cross linking
- increases shrinkage
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10
Q

What does a light cure do?

A

Monomer to polymer
Stresses set up at bonding interface, relieved up to gel point
After gel point = unyielding
Stress transferred to tooth
2mm depth recommended to minimise stress transfer

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11
Q

What are fillers for?

A

Placed to reduce shrinkage upon curing.

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12
Q

Examples of fillers

A

Strontium glass, barium glass, quartz, borosilicate glass, ceramic, silica, prepolymerised resin.

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13
Q

How are fillers classified?

A

Material, shape and size

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14
Q

What shapes can fillers be?

A

Irregular and spherical

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15
Q

What is the preferred shape of filler?

A

Spherical - easier to incorporate into a resin mix and take up more space leaving less resin.
Adding smaller particles fills the space between the larger particles so takes up more space, less shrinkage on curing.

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16
Q

What do inorganic fillers reduce and increase?

A

Reduce - polymerisation shrinkage, water sorption, thermal expansion
Increase - compressive/tensile strength, modulus of elasticity, abrasion resistance

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17
Q

What are the different sizes of filler?

A

Macrofill (old and the biggest)
Microfill (smaller) with prepolymerised filler
Hybrids with 2+ size regime
Nanohybrid 2+ size regime and prepolymerised filler

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18
Q

What is the third phase of composite?

A

Coupling agent - transfers stresses and provides a bond between filler particle and resin matrix.

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19
Q

Example of coupling agent

A

Organosilane
Siloxane end bonds to hydroxyl groups on filler
Methacrylate end polymerises with resin

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20
Q

What do coupling agents do?

A

Improve adherence of filler to resin surfaces

Have chemically coat filler surfaces and increase strength

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21
Q

Disadvantages of coupling agents

A

Age quickly in a bottle
Sensitive to water so silane filler bond breaks down with moisture
Water absorbed results in hydrolysis of silane bond and filler loss

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22
Q

What are the different types of composite?

A

Universal, flowable, packable

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23
Q

What are flowable composites and their indications?

A

Filler content is less than hybrid resins giving them lower viscosity
Class V restorations
Micro preparations
Extended fissure dealings
Adhesive cementation or ceramic restorations
Blocking cavity undercuts
Initial layer

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24
Q

Disadvantages of flowable composites

A

Lower filler volumes so increased shrinkage and wear with decreased strength

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25
Q

What are packable composites?

A

Macrofilled hybrids
They are firm and can be packed
Contain larger filler particles or fibres to improve packing
They are more difficult to sculpt due to high viscosity

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26
Q

What does acid etching do?

A

Preferentially decalcifies portions of enamel rods, exposed interprismatic and prism areas for interlocking tag formation with bonding resin.
Roughens the surface
Purely mechanical bonding, not true adhesion
20mPa

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27
Q

Why is dentine hard to bond to?

A

Contains type 1 collagen and water, is a moist living tissue, bonding to something hydrophobic.

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28
Q

What is the smear layer?

A

Created by any mechanical cutting of dentine, which is dentine debris of variable thickness, smear plugs are formed which block tubules.

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29
Q

Why does the smear layer affect bonding?

A

Protects dentine and pulp from bacteria penetration but impairs bond of composite to dentine, it is only loosely bound and can harbour bacteria.

30
Q

What are the four strategies for optimum bonding?

A

Smear layer left alone
Smear layer removed
Smear layer modified
Smear layer partially removed partially modified

31
Q

What is the mechanism of bonding?

A

Exchange process involving replacement of minerals by resin monomers which upon setting become micro-mechanically interlocked in created porosities.

32
Q

What is the dentine hybrid layer?

A

Mixture of adhesive polymers and dental hard tissues.

33
Q

What is the purpose of acid etching?

A 
Improves retention of restoration
Increases surface area of dentine
Removes smear layer
Allows for penetration of bonding agent into dentine
Protect pulp exposure before using
34
Q

Method for etching

A

Phosphoric acid gel or liquid 35-37%
Isolate teeth, apply etchant wait 5-15 seconds
5 secs for dentine
Rinse but don’t desiccate

35
Q

Second step - priming

A

Resin monomer, improves wettability, penetrates etched tubules, applied in a thin layer thinned with air and light cure maybe.

36
Q

Step 3 - bonding agent

A 
In filled or lightly filled resin
Adhesive bonds to collagen fibres in dentine and locks in - hybrid layer
Applied in thin layer
Light cured
Then apply composite
37
Q

What do primers contain to improve its wetting?

A

Solvents

38
Q

What are the different types of primers?

A

Acetone - one step
Ethanol - optibond solo
Water - scotch bond

39
Q

What is the problem with self etching primers?

A

They don’t etch enamel quite as well

40
Q

Why do we shake self etch primers?

A

Over time components can separate

41
Q

What are self etch adhesives?

A

Self etch primer combined with adhesive resin

42
Q

What is the pathway for successful bonding to dentine?

A

Wetting, infiltration to provide hybrid zone, mechanical interlocking, stress resistance.

43
Q

What are the different types of cements?

A

Glass polyalkenoate, resin modified, poly acid modified resin, composite

44
Q

Are GIC’s hydrophilic or hydrophobic?

A

Hydrophilic

45
Q

What are glass polyalkenoates?

A

Formed as a result of an acid base reaction between fluoride containing glass and a poly acid.

46
Q

What is the composition of GIC?

A

Fluoro-alumino-phospho-silicate glass and poly acid (polyacrylic usually)

47
Q

Disadvantages of GIC

A 
Technique sensitive
Moisture sensitive
Cannot be placed in stress bearing areas
Low tensile and fracture toughness
Poor wear resistance
Average aesthetics
48
Q

What is the setting reaction of GIC

A 
Decomposition 
Migration
Gelation 
Post set hardening
Maturation
49
Q

What does the final GIC contain?

A

Ion depleted layer, glass and poly salt matrix

50
Q

What does the maturation phase of GIC consist of?

A

Precipitation of Al3+ salts continues for 24 hours
Setting process continues at a slow pace for up to a year
Continued formation of poly salts - hydration and expanded gel structure

51
Q

What does the role of water play in the setting reaction of GIC?

A

Hydrates the mature cross linked matrix
Increases strength
Improves translucency - changes colour
Increased resistance to desiccation

52
Q

If too much water is present in the setting reaction of GIC what may happen?

A

Contamination, opacity, reduces strength

53
Q

If too little water is present in the setting reaction of GIC what may happen?

A

Desiccation
Grazing and cracking
Use Vaseline to protect from this

54
Q

How does GIC bind to the tooth structure?

A

Ionic bonding between polyalkenoate chain and ca2+ ions.

55
Q

How does GIC bind to dentine?

A

Hydrogen bonding between ions and collagen

56
Q

What are the two fluoride releases in GIC?

A

Rapid initial process responsible for early burst

Second slower and sustained process responsible for long term release

57
Q

What is the biocompatibility of GIC?

A

Plaque does not thrive on these restorations and strep mutants growth is inhibited. Soft tissue response is favourable as well as pulpal, mild inflammatory response. Is a direct capping material.

58
Q

Implications for GIC

A 
Cementation of rigid restorations 
Restorations of primary teeth
Class 3 and 5 restorations
Crown margin repair
Temporary dressing - carious cavity and fractured tooth
Base under amalgam and composite
59
Q

What are cermets?

A

Silver particles fused to glass, re ground mixture

60
Q

Indications of cermets?

A

Low coefficient of thermal expansion
Good adhesion
Brittle
F releasing temporary restorations

61
Q

What are diamond carve and diamond 90?

A

Co polymer of polyvinylphosphonic acid and polyacrylic acid

Glass polyalkenoate

62
Q

What are viscous glass polyalkenoates?

A 
Higher powder to liquid ratio
Lower water content
Smaller glass particles
Packable greater strength
Used in ART technique
63
Q

What is the survival time of GIC?

A

6 years posteriorly compared to 11 years for amalgam.

64
Q

What are rmgic’s?

A

GIC with addition of small quantities of resin

65
Q

Advantages of rmgic

A 
Tooth coloured better aesthetic 
Release fluoride
Recharges
Shorter setting time longer working
Decreased moisture sensitivity
Improved tensile strength 
Sets on command
Better wear
Higher bond strength to composite
Fewer steps than composite
66
Q

What are modifications to conventional GIC

A

Less water - replaced by water hema mixture

Modifications of poly acid with side chains that can polymerise by light cure (Fuji ii lc)

67
Q

What are the risks of HEMA?

A

Irritating
Allergic response
Use gloves, no touch technique

68
Q

Indications of RMGIC

A

Cervical and root caries
Base
Abfraction lesions

69
Q

What is the composition of composers?

A 
UDMA resin
Tcb resin
Strontium fluorosilicate glass
Initiators 
Stabilisers
70
Q

Setting mechanism of compomers

A

Light curing initiates polymerisation of resins

After water uptake acid base reaction takes place resulting in further cross linking

71
Q

Pros and cons of compomers

A 
Excellent handling
Command set
Good strength
Poor adhesion
Low f release
Needs bonding agent

CSA (18 decks)

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