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BDS2 CLINICAL Dental Materials > Introduction to DMS > Flashcards

Introduction to DMS Flashcards

1
Q

what does the behavior of dental materials affect

A 
selection
preparation
placement
performance
patient expectations
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2
Q

what indicates that a material is safe

A

CE mark

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3
Q

what are the different types of restorative materials

A 
amalgam 
composites
glass ionomer cements
composers
porcelain
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4
Q

what are the different impression materials

A

impression compound
impression paste
hydrocolloids
elastomers

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5
Q

what is the hydrocolloid impression material

A

alginate

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6
Q

what are the elastomers

A

polysulphides
polyethers
silicones

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7
Q

what are the different metals/alloys

A 
amalgam
cobalt chromium
titanium
gold 
stainless steel
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8
Q

what is composite like initially and finally

A

initially flows out of a cartilage - low to high viscosities available
finally sets with margins and hardens

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9
Q

what is impression material (polyether) like initially

A

initially flows into a tray and low viscosity

finally undergoes a setting reaction to become firm and stable

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10
Q

where is stainless steel used

A

denture base

orthodontic appliances

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11
Q

when is cobalt chromium used

A

partial dentures

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12
Q

what are the different properties of materials

A

mechanical, chemical, physical

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13
Q

what may forces applied to materials cause it to do

A

stretch/compress
deform (temp or permanent)
fracture

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14
Q

what is the equation for force

A

F = mass (kg) x gravitational acceleration

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15
Q

what are the types of forces

A

compressive
tensile
shear

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16
Q

what is the equation for stress

A

force/unit area

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17
Q

what is the equation for strain

A

change in length/original length

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18
Q

what is the definition of stress

A

force per unit cross sectional area that is acting on a material

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19
Q

what is the definition of strain

A

fractional change in the dimension caused by the force

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20
Q

what happens if the stress and strain exceed the maximum value that the material can withstand

A

fracture is most likely

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21
Q

what is the proportional limit

A

it is up until the proportional limit that stress and strain are linearly related

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22
Q

what is youngs modulus

A

measure of stiffness/rigidness of a material

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23
Q

what are the different mechanical properties

A

hard/soft
brittle/ductile
strong/weak
rigid/flexible

24
Q

what are the mechanical properties of enamel

A

brittle
rigid
strong
hard

25
Q

what are materials subjected to

A

biting
grinding/chewing
removal

26
Q

how does biting affect materials

A

compressive force applied to upper tooth when biting. Can the tooth withstand the force or will it fracture?

27
Q

how does grinding/chewing affect materials

A

tooth slides along the surface of the other. Frictional forces are experienced. Will tooth surface be abraded resulting in the loss of layers of enamel?

28
Q

what is the typical biting force

A

500 to 700N (50-70kg)

29
Q

how can materials be subject to removal

A

the material needs to adhere to enamel or it will be removed by masticatory forces – the forces will overcome the bond between material and tooth structure. This is through shear force

30
Q

how do the mechanical properties of enamel and dentine compare

A

Enamel is more rigid than dentine as it has a higher EM. The fracture stress of enamel is greater than dentine.

31
Q

how does amalgam stay in the tooth

A

through mechanical retention

32
Q

what kind of cavity design does amalgam require

A

undercut

33
Q

what kind of cavity design does composite require

A

minimal design

34
Q

how does composite stay in the tooth

A

adhesive retention

35
Q

what is the purpose of the undercut design

A

keeps the material in place as without it the material would just fall out as there is no bonding between the amalgam

36
Q

what are the different material failure mechanisms

A 
fracture
hardness
abrasion
abrasion resistance
creep
deformation 
debond
impact
37
Q

how does fracture occur

A

large force causes catastrophic destruction of material’s structure
the biting forces are gradually increased

38
Q

what is hardness

A

ability of surface to resist indentation (KHN)

39
Q

what is abrasion

A

material surface removal due to grinding

40
Q

what is abrasion resistance

A

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

41
Q

what is fatigue

A

repetitive ‘small’ stresses causing material fracture

42
Q

what is creep

A

gradual dimensional change due to repetitive small forces

43
Q

what is deformation

A

an applied force may cause a permanent change in material’s dimensions (but not fracture it!)

44
Q

what is impact

A

large sudden forces causes fracture

45
Q

what is a hardness test

A

The hardness is determined by measuring the depth of the indenter penetration or by measuring the size of the impression left by an indenter.

46
Q

what happens in abrasion

A

In abrasion the tooth grinds and slides along the opposing tooth surface and the tooth surface is abraded which can result in the loss of material in surface layers or a roughened surface

47
Q

what happens in fatigue

A

Most failures are not due to the application of a single load (force) but instead when repeated loads are applied, small flaws (cracks) in a material grow (propagate) allowing fracture when only a relatively small force is applied.

48
Q

how does creep occur

A

low level forces continually applied
amalgam protrudes around the margins
exposed amalgam vulnerable to fracture

49
Q

how does permanent deformation occur

A

Applying stress to a material that results in a releasing stress that is greater than the elastic limit results in permanent deformation, dL

50
Q

how are orthodontic appliances removed

A

shear force is applied to separate the bracket/bonding material from tooth surface

51
Q

how can impact effect dentures

A

the impact can cause them to either split down the middle or for surface cracks to form

52
Q

what are the other mechanical properties

A

ductility/brittleness

tear strength

53
Q

what are the chemical properties

A
  • setting mechanism
  • setting time
  • corrosive potential
54
Q

what are the physical properties

A
  • viscosity
  • thermal conductivity
  • thermal expansion
  • density
  • radiodensity
55
Q

what are the ideal properties

A

Each dental material has its own properties, when evaluating a material, compare its performance with the ideal properties

56
Q

how does the oral environment effect materials

A

saliva
temperature variations
pH variations
oral bacteria

BDS2 CLINICAL Dental Materials (15 decks)

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