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COPY BDS3 University of Adelaide Dentistry > Materials Science > Flashcards

Materials Science Flashcards

1
Q

Aprismatic enamel can be found where?

A

25 micron layer on the surface of the tooth

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2
Q

What type of etch pattern is poor for retention?

A

Type 3 - irregular

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3
Q

What is the bond strength between enamel and resin?

A

20-25 MPa

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4
Q

What are the organic components of dentine?

A

Collagen
Proteins
Chondroitin Sulphate
Mucopolysaccharide

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5
Q

As you get deeper into dentine, what do you expect to see?

A

Denser Tubules: therefore more moisture

Secondary and Tertiary dentine

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6
Q

What are the 3 sources of moisture on dentine?

A

Triplex
Oral Humidity
Dentinal Tubules

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7
Q

What is in smear layer?

A 
Tooth fragments
Organic matter
Bacteria
Blood
Crevicular Fluid 
Saliva
Collapsed Collagen
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8
Q

How large is the ion-exchange layer in GIC?

A

0.5-1 microns

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9
Q

What is the main ingredient for wet bonding primers?

A

Acetone- used to chase water

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10
Q

Why is acetone based primers less effective?

A

Overwet dentine causes water blisters
Water is trapped between dentine and resin
Poorer physical properties
Very technique sensitive

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11
Q

HEMA creates a bond between dentine and adhesive resin. Which functional group of the primer bond with the dentine surface?

A

-OH Group

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12
Q

T/F: 1st generation adhesives had bonding to both enamel and dentine

A

False: enamel only

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13
Q

T/F: 5th Generation Adhesives is a 2-step resin with Self Etch/Prime + Adhesive

A

False, 5th generation is Total Etch with combined Primer/Adhesive

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14
Q

Which generation is 3 step Etch-and-Rinse adhesive?

A

4th Generation: Etch > Primer > Adhesive

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15
Q

What is an example of a 8th Generation universal adhesive?

A

G-Premio

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16
Q

G-Bond is an example of what generation adhesive?

A

7th Generation: combined self etch/primer/adhesive

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17
Q

T/F: Monomers (BIS-GMA, UDMA, TEGDMA) all have double carbon bonds at both ends

A

True

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18
Q

T/F: HEMA is exclusively hydrophilic

A

False - HEMA has both hydrophobic and hydrophilic ends but is overall hydrophilic

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19
Q

Why is self etch less effective than total etch?

A

pH is higher (1-2) vs total etch (pH 1), so smaller resin tags are created

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20
Q

What is considered a gold standard adhesive?

A

4th Generation 3 step.

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21
Q

What are the 3 components of a self-etch primer?

A

Adhesive Group that creates bond to dentine and enamel

Spacer Group: influences flexibility, solubility, wetting behaviour

Polymerizable Group

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22
Q

Microscopically what would a mild pH self-etch (pH 2) result in

A

Remaining resin impregnated smear layer

Shallow resin tag formation

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23
Q

Why might phase separation of adhesion occurs

A

Ingredients in all-in-one adhesives are inherently unstable

Excessive water content causes separation of bis-GMA and HEMA

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24
Q

What factor could affect permeability of the hybrid layer?

A

Trapped air bubbles

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25
Q

What is a main difference in ingredients of a 7th generation adhesive

A

No HEMA: 4-MET monomer used instead (G-Bond)

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26
Q

What monomers are used in G-Premio and what sort of bonding is it?

A

4-MET, MDP, MDTP

Chemical Bonding

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27
Q

What are the steps to apply G-Premio?

A

Total etch: Etch with 37% H3PO4 for 15s; Self-etch: no etching
Apply G-Premio to all surfaces and leave for 10 sec
Dry for 5 sec at MAX air pressure
Light cure for 10 sec
Apply resin composite

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28
Q

What operator aspects would make G-premio preferential for treating hypersensitivity?

A
  1. One Step
  2. No wash steps required
  3. Better Patient Comfort
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29
Q

What is the main difference between 5th and 6th generation Adhesives?

A

5th Generation: Total Etch + Primer/Adhesive combination

6th Generation: Self Etch/Primer combination + Adhesive

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30
Q

What are problems with etch-and-rinse adhesives (4-5th Generation)?

A
  1. Incomplete infiltration of primer into demineralized collagen
  2. Long-term water sorption into the hybrid layer with HEMA based adhesives
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31
Q

What are problems with self-etch adhesives (6-7th Generation)?

A
  1. Formation of water blisters at the resin/ dentine interface
  2. Semi-permeable membranes
  3. Greater failure rates and poorer bonding strengths than etch-and-rinse adhesives
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32
Q

What is an example of an adherent?

A

Resin Composite, Acrylic, Ceramic

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33
Q

What is an example of an adhesive?

A

Adhesive Resin, Silane Primer

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34
Q

What is an example of an adherend?

A

Enamel, Dentine, Ceramic

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35
Q

Define Macromechanical bonding

A

Visible interlocking between dissimilar materials

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36
Q

Define Micromechanical bonding

A

Microscopic mechanical interlocking between dissimilar materials

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37
Q

How would you repair a fractured ceramic crown with CR?

A

Roughen porcelain surface - 24% hydrofluoric acid . Use silane bonding agent to bond porcelain to CR (as silane can bond resin cements to ceramic)

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38
Q

What are the 4 types of adhesion in dentistry?

A

Macromechanical
Micromechanical
Interfacial
Chemical

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39
Q

How would you repair exposed metal on a fractured PFM (Porcelain Fused to Metal) crown?

A

Sandblasting then Metal Primer

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40
Q

What is interfacial adhesion?

A

A broad term describing adhesion between two very dissimilar materials, and is a combination of mechanical and chemical adhesion

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41
Q

What are the 4 layers in a metallic crown?

A
  1. Gold Alloy + Underlying Metal Primer
  2. Resin Cement
  3. Dentine Primer/Adhesive
  4. Enamel / Dentine
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42
Q

What are the 4 layers when doing a Ceram-Metal Bridge?

A
  1. Ceramic Crown + underlying silane layer
  2. Resin Cement
  3. Primer / Adhesive
  4. Enamel
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43
Q

What is a metal primer and why is it needed?

A

Bi-directional bonding to both:

  1. Resin Bond via carbon double bonds to vinyl/methacrylate groups
  2. Metal Bond via a carbonyl (double oxygen bond) group
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44
Q

What is adhesive failure?

A

Breakage of bond between the materials

45
Q

What is cohesion failure?

A

Breakage within the material themselves

46
Q

What are the 6 conditions for optimal adhesion?

A
  1. Large surface area
  2. Clean bonding surfaces
  3. Close contact between surfaces
  4. Good wetting of adhesive - needs low viscosity to flow
  5. Dimensionally stable adhesive
  6. Correct protocols for bonding
47
Q

What stimuli can cause dentinal hypersensitivity?

A 
Thermal
Evaporative
Tactile
Osmotic 
Chemical
48
Q

What is the most common area for dentinal hypersensitivity?

A

Buccal aspects at the cervical regions of permanent teeth

49
Q

What are 4 clinical causes of dentinal sensitivity?

A
  1. Tooth Wear
  2. Recession
  3. Periodontal Disease
  4. Periodontal Therapy
50
Q

Which occupation in Australia is at high risk for dentinal hypersensitivity?

A

Wine Tasters (79%) #firstworldproblems

51
Q

What are the 2 categories of treatment options for dentinal hypersensitivity?

A
  1. Tubule occlusion by adhesion of exogenous materials

2. Modification of nerve excitability

52
Q

How does Potassium Nitrate (Sensodyne) modify nerve excitability to reduce dentinal sensitivity?

A

High K+ ions outside nerve membranes blocks repolarisation phase of AP, thereby blocking pain impulse

53
Q

Which exogenous materials aid in remineralising exposed dentinal tubules in the treatment of dentinal hypersensitivity?

A
  1. High concentration Fluoride dentifrices
  2. Bioglass (Si gel > CaPO4 > Hydroxyapatite)
  3. RMGIC/GIC restorations
  4. Tooth Mousse Plus
54
Q

Which exogenous materials aid in physically occluding exposed dentinal tubules in the treatment of dentinal hypersensitivity?

A
  1. Stannous Fluoride
  2. Resin Sealants
  3. CR/RMGIC/GIC Restorations
  4. Arginine
55
Q

What are 2 high risk groups for Dentinal Hypersensitivity via Tooth Wear?

A

Patients with GORD

Wine Tasters

56
Q

Dentine is porous biomaterial that contains numerous tubules filled with fluid. How do tubule diameter and density change from superficial to deeper dentine?

A

Tubules increase in diameter and increase in density.

57
Q

What are the 3 dentinal hypersensitivity theories?

A
  1. Dentinal Receptor Theory (debunked)
  2. Odontoblast Transducer Theory (debunked)
  3. Hydrodynamic Theory
58
Q

Dentinal hypersensitivity is a common conditions that can present management dilemma to clinicians. What type of treatment is considered most common and conservative but effective in its management?

A

Frequent home application of toothpaste (Sensodyne, Stannous Fluoride)

59
Q

What are 3 prevention measures for minimising dentinal hypersensitivity?

A
  1. Remove causal factors (Tooth Wear, Erosion, Gingival Recession)
  2. Analysis of Dietary / Lifestyle factors / Medications
  3. Salivary Protection
60
Q

How does Duraphat work in the mouth?

A

Deposition of CaF2 globules on the tooth surface within a resin layer at neutral pH.

When pH lowers and becomes acidic Hydroxyapatite is formed

61
Q

What is an example of a nanofil composite resin?

A

Filtek Supreme

62
Q

What are 4 factors associated with the cavity prep that can affect adhesion to tooth structure

A
  1. Smear Layer
  2. Cavity Size
  3. Moisture
  4. Foundation of bonding substrate
63
Q

What are desirable properties for a resin composite?

A
  1. Aesthetics
  2. Durability
  3. Ease of Handling
  4. Low Shrinkage
  5. Wear Resistance
  6. Radiopacity
  7. Anticariogenic (Fluoride Release)
  8. Biocompatibility
64
Q

What were the key properties of first generation posterior CRs in the 1960-80s?

A

Macrofils - to give strength and durability

  • Poor Aesthetics
  • Hard to Polish
65
Q

What are the features of current generation of “universal” resin composites?

A
  • Nanohybrid/Nanofil resins

- Low shrinkage formulations

66
Q

What do monomers become when light cured?

A

Polymers

67
Q

What is an example of an interfacial phase in a Resin Composite?

A

Silane Coupling Agent

68
Q

What are the components of a nanofil resin composite such as Filtek Supreme?

A
  1. Larger Nanocluster Particles: agglomerates of Zr/Si nanoparticles fused together
  2. Nanomers: SiO2 particles
  3. Resin: BisGMA, UDMA, TEGDMA, PEGDMA (low shrinkage)
  4. Silane: coupling agent fills up porous areas
69
Q

What are indications for Flowable resin composite?

A
  1. Suitable in non-load bearing areas
  2. Repairing old resin composites
  3. Fissure Sealant
  4. Filling voids
70
Q

What are indications for Packable resin composites?

A

Adaptation to tight proximal tooth contacts

71
Q

What are the properties of packable resin composites?

A
  1. Higher average filler content (80%)
  2. Larger filler particle size
  3. High Compressive Strength
  4. High Wear Resistance
  5. Prone to surface roughening
  6. Poor Polish Retention
72
Q

What is required for a polymer to be formed?

A
  1. Monomer

2. Free radical: that is produced either by light, heat or a chemical reaction

73
Q

What are the 4 stages of a polymer reaction

A
  1. Initiation Stage
  2. Propagation Stage
  3. Transfer Stage
  4. Termination Stage
74
Q

What is there less polymerisation shrinkage in bulk fills?

A

The monomer chains are far larger, since there are less monomer molecules overall, the % of polymerisation is less

75
Q

What is elastic modulus?

A

Defines a material’s rigidity.

Elastic Modulus = Stress / Strain

76
Q

What is the elastic limit?

A

The point where the material loses its elastic capacity to bear stress.

(The point on the True Stress-Strain Curve when parabolic curve becomes linear)

77
Q

When does Post-Gel Shrinkage Strain occur?

A

Occurs after the material has lost its ability to flow. It typically occurs up to 24 hours after light curing

78
Q

Which direction does Polymerisation shrinkage occur?

A

Shrinkage occurs towards the light source

79
Q

How do you clinically prevent problems with polymerisation shrinkage?

A

Opposite layering of CR and incremental light curing

80
Q

What is Compressive Strength?

A

Ability of materials to resist a load that tend to shorten/compression it

81
Q

What is Tensile Strength?

A

Ability of material to resist load to elongate/stretch it

82
Q

When is diametral tensile strength tested?

A

When the material is brittle and can’t be gripped by normal tensile strength tests

83
Q

What is flexural strength?

A

Ability of material to withstand bending/flexural stress without it breaking

84
Q

What is the difference between 2 and 3 body tooth wear

A

Presence of a 3rd body at the interface: food, toothpaste, tooth chips, F, CPP-ACP particles

85
Q

What are examples of extrinsic erosive substances?

A

1) Carbonated Drinks (Carbonic/Phosphoric acids)
2) Citric Acid
3) Sour Candies (Citric/Malic Acid)

86
Q

What are examples of intrinsic erosive substances?

A

Stomach acid via GORD or induced vomiting

87
Q

What are the classic symptoms of GORD?

A

Acid Regurgitation

Heartburn

88
Q

What is GORD?

A

Gastroesophageal Reflux Disease (GORD): Condition where the reflux of stomach contents causes troublesome symptoms and complications

89
Q

Why is sleep reflux worse than normal reflux?

A

Far more extensive damage due to high duration of contact of acids and lowered Defense Mechanisms during sleep

1) Decreased Salivary Flow during sleep
2) Decreased heartburn: conscious trigger to deal with the reflux
3) Decreased Swallowing
4) Decreased Esophageal Peristalsis response

90
Q

What are 3 manifestations of prolonged GORD?

A

Reflux Esophagitis (Mucosal Erosion)
Barrett’s Oesophagus
Oesophageal Adenocarcinoma

91
Q

How does Barrett’s Oesophagus manifest?

A

Constant insult causes metaplasia of respiratory epithelium to transition to intestinal mucosa - with the presence of infolding and goblet cells

92
Q

Oesophageal Adenocarcinoma is a progression of what?

A

Barrett’s Oesophagus: ongoing metaplasia causes neoplastic differentiation. This has a poor prognosis neoplasm with high risk factors for males over 60 and patients that are obese.

93
Q

Would CPP-ACP or Fluoride dentifrices be effective for sleep GORD?

A

Unlikely, sleep reflux often results in pH drops below 1. CPP-ACP / Fluoride are effective defenses when acid attacks are with the caries range of pH 4-5, with some limited defense at pH 3.

94
Q

What are the main ways to treat oral aspects of GORD

A

1) Remove the Cause
2) Medical Management
3) Control adjunct Tooth Wear aspects - construct a nightguard
4) Reinforce Oral Defenses: retain biofilm overnight, increase saliva, remineralisation agents
5) Defer restorative treatment until erosion is resolved

95
Q

Which tooth material is easiest to bond to?

A

Prismatic Enamel that is not affected by quantitative defects such as fluorosis/hypoplasia

96
Q

What is cementum hard to bond to?

A

High organic component formed by extrinsic and intrinsic fibres

97
Q

Is it harder or easier to bond to dentine the deeper you go?

A

More difficult: high density of dentinal tubule meaning increased dentinal fluid and moisture

98
Q

What 4 factors of cavity preparation will influence the success of bonding?

A

1) Presence of moisture
2) Resistance and retention
3) Removal of smear layer + pellicle
4) Poor foundation of the bonding substrate (eg retained infected dentine)

99
Q

Why is Aprismatic enamel harder to gain retention to restorative materials

A

Surface is more resistant to etching - erodes whole layer rather than creating porosities for resin tags

100
Q

How much enamel is removed by 37% orthophosphoric acid etching?

A

10-20 microns of enamel

101
Q

What is the bond strength between enamel and GIC?

A

10-12 MPa

102
Q

What is the bond strength between enamel and RMGIC?

A

15-20 Mpa

103
Q

What is the difference between dry and wet bonding with primers

A

Wet Bonding: dentine is not desiccated and primer displaces water to support collagen

Dry Bonding: fibres are rehydrated and stiffened by the hydrophilic primer

104
Q

Why is wet bonding no longer preferential for primers?

A

1) Technique Sensitive
2) Acetone content evaporates from containers if not used regularly
3) Overwet dentine increases risk of water blisters
4) Poorer physical properties, leading to weaker bonds

105
Q

What is the long term disadvantage of dry bonding primer?

A

Moisture sorption from HEMA over the long term breaks down the hybrid layer

106
Q

What are the 3 main reasons for microleakage?

A

Moisture Contamination
Insufficient Dentine Etch
Polymerisation Shrinkage

107
Q

What is nanoleakage?

A

Submicron channels that allow passage of fluids - this can happen in both wet and dry bonding techniques

108
Q

What is the difference between adhesive and cohesive failure?

A

Adhesive: failure in bond between materials
Cohesive: failure in material themselves

COPY BDS3 University of Adelaide Dentistry (28 decks)

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