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BDS2 DMS > Dental Materials > Flashcards

Dental Materials Flashcards

1
Q

Intro to DMS

What indicates the material is safe for its designated purpose?

A

CE mark

Essential requirement

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2
Q

Intro to DMS

Examples of Resorative Materials

A
  • Amalgam
  • Composites
  • Glass ionomer cements
  • Compomers
  • Porclein
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3
Q

Intro to DMS

Examples of Impression Materials

A
  • Impression Compound
  • Impression Paste
  • Hydrocolloids (alginate)
  • Elastomers (Polysulphides, Polyethers, Silicones)
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4
Q

Intro to DMS

Examples of Metals/Alloys

A
  • Amalgam
  • Cobalt chronium
  • Titanium
  • Gold
  • Stainless Steel
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5
Q

Intro to DMS

What are the 3 types of forces?

A
  1. Compressive
  2. Tensile
  3. Shear
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6
Q

Intro to DMS

How to calculate stress?

A

Stress = Force/Unit Area

Units: Pascal (Pa)

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7
Q

Intro to DMS

Define Strain

Calculation

A

Strain
= change in length/original length

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8
Q

Intro to DMS

Define Elastic (Young’s) Modulus (YM)

Calculation

A

YM = Stress/Strain

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9
Q

Into to DMS

What are the mechanical properties of enamel?

A
  • brittle
  • hard
  • strong
  • rigid
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10
Q

Intro to DMS

Which forces will dental materials need to be able to withstand?

A
  1. Compressive (biting)
  2. Friction (Grinding/chewing)
  3. Mastiscatory: Shear (Removal)
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11
Q

Intro to DMS

What would the cavity desgin and retention be for an amalgam restoration?

A

Cavity Design: Undercut
Retention: Mechanical

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12
Q

Intro to DMS

What would the cavity desgin and retention be for an composite restoration?

A

Cavity Design: Minimal
Retention: adhesion

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13
Q

Intro to DMS

What requirements must a material have for filling a cavity?

A
  • must be pliable
  • fit shape of interest
  • set to form hard, strong material
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14
Q

Intro to DMS

What are the several failure mechanisms of materials?

A
  1. Fracture
  2. Hardness
  3. Abrasion
  4. Abrasion Resistance
  5. Fatigue
  6. Creep
  7. Deformation
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15
Q

Intro to DMS

Define fracture

A

Large force causes destuction of material’s structure

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16
Q

Intro DMS

Define hardness

A

ability of surface to resist indentation (KHN)

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17
Q

Intro to DMS

Define abrasion

A

material surface removal due to grinding

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18
Q

Intro to DMS

Define abrasion resistance

A

ability to withstand surface layers being removed, so comprimising surface integrity

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19
Q

Intro to DMS

Define fatigue

A

repetitive “small” stresses causes material fracture

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20
Q

Intro to DMS

Define Creep

A

Gradual dimensional change due to repeptitive small forces

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21
Q

Intro to DMS

Define deformation

A

applied stress causes permanent change in material’s dimensions

DOES NOT FRACTURE IT

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22
Q

Intro to DMS

Define De-bond

A

applied forces sufficient to break material-tooth bond

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23
Q

Intro to DMS

Define impact

A

large, sudden force causes fracture

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24
Q

Intro to DMS

What causes permanent deformation of materials

A

when the stress released is more than the elastic limit

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25
Q

Intro to DMS

What are the chemical properties of materials

A
  • setting mechanism
  • setting time
  • corrosive potential
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26
Q

Intro to DMS

What are the physical properties of materials

A
  • viscosity
  • thermal conductivity
  • thermal expansion
  • density
  • radiodensity
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27
Q

Intro to DMS

Standard conditions of the oral environment

A
  • saliva
  • temp variations
  • pH variations
  • oral bacteria
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28
Q

Bonding to Teeth

Properties of dental adhesive

A
  • provide high bond strength to tooth tissues
  • immediate high strength bond
  • durable bond
  • impermeable bond
  • easy to use
  • safe
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29
Q

Bonding to Teeth

In practice what is normally used for enamel etching?

A

30-50% aqueous solution of phosphoric acid

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30
Q

Bonding to teeth

Which resin is generally applied to the etched enamel?

A

Low viscosity Bis-GMA resin

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31
Q

Bonding to teeth

What is the composition of dentine?

A
  • 20% organic (mostly collagen)
  • 70% inorganic (mostly HA)
  • 10% water
32
Q

Bonding to teeth

What are the 4 requirements of a dentine bonding agent (DBA)?

A
  1. Abilty to flow
  2. Potential for strong contact with dentine surface
  3. Low viscosity
  4. Adhesion to substrate
33
Q

Bonding to Teeth

What are the 3 types of adhesion to substrates within in DBA?

A
  1. Mechanical
  2. Chemical
  3. Van Der Waals
34
Q

Bonding to Teeth

Define critical surface energy

A

the surface tension of a liquid that will just spread on the surface of a solid

35
Q

Bonding to Teeth

How does bonding to dentine via adhesion though molecular entanglement work?

A
  1. adhesive absorded onto the surface of dentine can penetrate the surface due to good wetting of dentine by adhesive and the appropiate srface energies of the two
  2. the absorbed component can form a long chain polymer
  3. polymer meshes with the substrate which results in molecular entanglement forming high bond strength
36
Q

Bonding to teeth

What is the smear layer?

A

Adherent layer of organic debris that remais on the dentine surface afte preparation of the dentine during the restoration of the tooth

37
Q

Bonding to Teeth

How can you overcome the smear layer?

A
  1. Remove it and bond to ‘clean’ dentine beneath
  2. Incorporate it by penetrating it, infiltrate with DBA and stick to dentine below
38
Q

Bonding to teeth

Why is Phosphorylated Bis-GMA and NPG-GMA no longer used for bonding to dentine?

A
  1. Bond was to only the top of the smear layer which is not firmly attached to dentine therefore weak
  2. Phosphate and calcium ionic bond was not strogn and affected by moisture
  3. Saliva or dentinal fluid caused hydrolysis of the bond therefore breaks down resulting in leakage of the restoration
  4. Overall low bond strength
39
Q

Bonding to teeth

Give examples of total etch materials

3

A
  • Scotchbond multipurpose
  • Clearfil photo band
  • Optibond FL
40
Q

Bonding to teeth

What are the components of a Total Etch DBA

A
  • Dentine conditioner: an acid, usually 35% phosphoric
  • Primer: Adhesive part, with a hydro- philic/phobic part
  • Adhesive: A resin, penetrares surface of dentine attaching the primers hydrophobic part
41
Q

Bonding to teeth

How does the dentine conditioner work in a total etch DBA?

5 steps

A
  1. Removes smear layer
  2. Opens dentinal tubules by removing smear plugs
  3. Decalcifies uppermost layer of dentine
  4. Etchant washed off with water
  5. Collagen network in top 10um of dentine is exposed and penetrated by next 2 components of a total etch DBA
41
Q

Bonding to teeth

What is the most common coupling agent found in primers of a total etch DBA?

A

Hydro ethyl methacrylate (HEMA)

42
Q

Bonding to teeth

  1. Which end of the primer bonds to dentine?
  2. Which end bonds to resin?
A
  1. hydrophilic (hydroxy ethyl group)
  2. hydrophobic (methacrylate)
42
Q

Name some examples of adhesives

A
  • HEMA
  • NTG-GMA
  • 4-META
  • MDP
  • GPDM
42
Q

Bonding to teeth

What are 3 characteristics of an adhesive in total etch?

A
  1. mainly hydrophobic
  2. may contain filter particles to make it stronger
  3. contains camphorquinone - allows it to light cure
42
Q

Bonding to teeth

Give examples of total etch two-stage bonding agents

A
  • Scotchbond One
  • Prime and Bond
  • Optibond Solo
  • i-Bond TE
  • XP Bond
42
Q

Bonding to teeth

Why is moist dentine better for bonding?

A

The expanded dentine surface is porous and will absorb primer therefore a good bond

43
Q

Bonding to teeth

What are the additional components in a combined bottle of self etching primer and sealer?

Chemicals are same as in primer bottles

A
  • Resin Bis-GMA
  • solvent eg. alcohol or acetone + camphorquinone (allows light curing)
44
Q

Bonding to teeth

What is the fundamental mechanism of all bonding material?

A

Mineral exchange - minerals removed from dental hard tissue are replaced by resin, which once mineralised mechanically interlock in these porosities
= Molecular Entanglement

45
Q

Bonding to teeth

What are the characteristics of a strong self etch?

A
  • soluble and weaken integrity of bond
  • can dissolve too much HA which will expose collagen = bond will fail
  • bonds well to enamel but not dentine
46
Q

Bondin to teeth

what are the characteristics of a mild
self etch?

A
  • HA crystals remain around collagen -> protective against breakdwon and remain Ca ions allow ionic bonding
  • partially demineralises dentine
47
Q

Bonding to teeth

What is an example of a mild etch?

A

Scotchbond universal

48
Q

Bonding to teeth

Why are MDP and 4-META agents better in a mild self etch than HEMA containing materials?

A

HEMA containing materials are more acidic and absorb more H2O therefore less durable bond

49
Q

Bonding to teeth

What challenge is there with regards to the smear layer and adhesives in bonding materials?

A

adhesives in materials need to be able to penetrate smear layer without decalcifying tooth surface too much, which removes HA

50
Q

Bonding to teeth

Why is it important to not remove HA from tooth surface whilst bonding materials penetrate smear layer?

A
  1. HA is required for strong durable bonding
  2. HA protects dentine from hydrolytic breakdown
51
Q

Bonding to teeth

What are the advantages of self etching materials?

A
  • Less technique sensitive
  • simultaneous deminerlisation and resin inflitration
52
Q

Bonding to teeth

What are the disadvantages of self etching materials?

A
  • variability between products with regard to initial pH of solution
  • difference in pH results in dfferent etch and different penetration of resin
  • materials with lower pH may not etch enamel efficiently
53
Q

Cavity Lining Materials

What materials are placed in tooth cavities?

A
  • Composite resin
  • glass ionomer
  • amalgam
  • preious metal
  • ceramic
54
Q

Cavity Lining Materials

what are some disadvantages of restoratives?

A
  • May not make intimate contact with the tooth surface (especially dentine) -> any gap may allow ingress of fluids and bacteria
  • Heat released during setting/curing
  • Release of chemicals (may be pulp irritants and cause pain or pulpal damage)
55
Q

Cavity Lining Materials

What are lining materials?

A

Its an intermediate restorative material
- prevents gaps
- act as a protective barrier

56
Q

Cavity Lining Materials

What is the difference between Cavity Base and Cavity Lining?

A

Cavity Base
- thick mix placed in bulk to replace dentine
- used to minimise bulk of materials or block out undercuts
Cavity Lining
- thin coating (<0.55mm) placed over exposed dentine

57
Q

Cavity Lining Materials

What are the general purposes of a liner?

A
  • Pulpal protection from chemical stimuli, thermal stimuli, bacteria and endotoxins
  • Therapeutic
  • Pallitave
58
Q

Cavity Lining Materials

What are the properties of lining materials?

A
  • Ease of use
  • thermal
  • mechanical
  • radiopaque
  • marginal seal
  • solubility
  • cariostatic
  • biocompatible
  • compatible with restorative materials
59
Q

Caviity Lining Materials

What is thermal conductivity?

A

How well heat energy is transferred through a material

W/m-1/degrees C-1

60
Q

Cavity Lining Materials

What is thermal expansion coefficent?

A

Change in length per unit length fo a temp rise of 1 degrees celcius

Units: ppm degrees C-1

61
Q

Cavity Lining Materials

What are the ideal thermal properties of liners?

A

Thermal Conductivity: low
Thermal expansion coefficient: match coefficient of tooth
Thermal diffusivity: at least as low as tooth enamel

62
Q

Cavity Lining Materials

What are two examples of a Setting Calcium Hydroxide Liner paste?

A
  1. Life
  2. Dycal
63
Q

Cavity Lining Materials

What reaction takes place between the Base and Catalyst of a Setting CaOH Liner?

A

Chelation Reaction (Setting Reaction) between ZnO (base) and Butylene Glycol Disalicylate (Catalyst)

64
Q

Cavity Lining Materials

What are the advantages and disadvanatges of a Setting CaOH Liner?

A

Adv.
- quick setting time
- radiopaque
- easy to use

Dis.
- Low compressive strength
- unstable
- soluble

65
Q

Caivity Lining Materials

Give examples of ZnO Based Cements

A
  • Zn Phosphate
  • Zn Polycarboxylate
  • ZnO Eugenol (ZOE)
  • Resin Modified ZOE
  • Ethoxybenzoic Acid (EBA) ZOE
66
Q

Cavity Lining Materials

What are the adv. of using Zn Polycarboxylate Cement as a base?

A
  • Bonds to tooth in a similar way to glass ionomer cements
  • less heat of reaction
  • pH low initially but returns to neutral pH quicker and longer chain acids dont penetrate dentine easily
  • Cheap
67
Q

Cavity Lining Materials

What are the dis. of using Zn Polycarboxylate Cement as a base?

A
  • difficult to mix
  • difficult to manipulate
  • soluable in oral environment at lower ph
  • Opaque
  • Lower modulus and compressive strength than Zn Phosphate Cement
68
Q

Cavity Lining Materials

What are the properties of ZOE cement?

A
  • adequate working time
  • rapid setting time (sets quicker in mouth due to moisture)
  • Low thermal conductivity
  • Low strength (weak H bonds between eugenolate molecules)
  • Radiopaque
  • High solubility
  • Cannot be used under composite resin
69
Q

Cavity Lining Materials

What properties does Resin Modified ZOE have in comparison to ZOE?

A
  • increased compressive strength
  • Low solubility
70
Q

Cavity Lining Materials

What are the properties of EBA cement?

A
  • Stronger than ZOE/Resin Modified ZOE
  • Less Soluble
71
Q

Cavity Lining Materials

What are the properties of Glass ionomer lining materials?

A
  • Easy to use
  • Long wokring time
  • Thermal conductivity and diffusivity lower than denitine (GIC and RMGIC)
  • Thermal expansion similar to dentine (GIC)
  • Greater compressive strength
  • Marginal seal better
  • GIC solubility > RMGIC solubility
  • GIC solubility < other lining materials (except Zn Phosphate Cement)
  • RMGIC solubility < any other cement
  • GIC release fluoride (cariostatic)
  • RMGIC polymerisation release cytotoxic molecules (help against cavity residual bacteria)
  • GIC bonds to rest. materials
  • RMGIC no surface treatment
  • Could bond AM to tooth using RMGIC
72
Q
A

BDS2 DMS (1 decks)

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