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BDS2 Dental Materials Sciences > Intro to DMS > Flashcards

Flashcards in Intro to DMS Deck (67)
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1
Q

steps in dental procedure

A
  • examination
  • diagnosis
  • treatment plan - need knowledge of DMS to select and explain to patient material used
  • surgical procedure
2
Q

what does the behaviour of dental materials affect? (5)

A
  • choice
  • preparation
  • application
  • performance
  • patient’s expectation
3
Q

how is choice of dental material effected by the dental material’s behaviour?

A

adequate/best type

select the best option for the patient/circumstances based on knowing what available materials offer

4
Q

how is preparation effected by the dental material’s behaviour?

A

cavity design and tooth surface depends on the material

many different procedures depending on the material

5
Q

how is application effected by the dental material’s behaviour?

A

technique of placing (increments/curing)

placement of materials, working time, setting time vary with materials - don’t want to repeat applications due to lack of knowledge

6
Q

how is performance effected by the dental material’s behaviour?

A

quality of fit, longevity

need to know what you can reasonably expect of a material; how well it fits, how long till the material sets fully/ when can patient eat/drink; how smooth the surface is etc.

7
Q

how can patient’s expectations be effected by the dental material’s behaviour?

A

aesthetics, durability

can be very high, need to explain what the material offers in terms of performance e.g. longevity, appearance

8
Q

CE mark

A

mark of safety
- essential requirement

material is safe if used appropriately

9
Q

2 challenges in choosing dental materials

A
  • the number of types of materials

- constant refinements of products and changes in product names

10
Q

examples of restorative materials

A
  • amalgam
  • composites
  • glass ionomer cements
  • compomers
  • porcelain
11
Q

examples of impression materials

A
  • impression compound
  • impression paste (hydrocolloids)
  • alginate
  • elastomers (polysulphides, polyethers, silicones)

alginates, polyethers, silicones are most commonly used

12
Q

examples of metals/alloys

A
  • amalgam
  • cobalt chromium
  • titanium
  • gold
  • stainless steel
13
Q

what do impression materials record?

A

record the dentition

negative replica

14
Q

what does gypsum (dental stone) reocrd?

A

positive replica of dentition

allows to study dentition (survey models) and make appliances e.g. partial denture framework

15
Q

what is PMMA used for?

A

typically full dentures have acrylic teeth and PMMA denture bases

  • aesthetically high quality
  • accurate fit
  • lightweight

stainless steel alloys can also be used

16
Q

what does PMMA stand for?

A

Poly (methyl methacrylate)

17
Q

what is the use of stainless steel orthodontic appliances?

A

complex structure to re-align many teeth
- wire under tension to produce force on teeth and so move them

strong to withstand masticatory forces
adjustable to shape
not aesthetic

18
Q

what is the use of cobalt chromium partial denture?

A

complex framework to hold artificial tooth/teeth in place

  • easy to place and remove
  • lightweight
19
Q

why study DMS?

A
  • will use many different materials with range of characteristics and modes of use
  • must use materials appropriately
  • must be independent (not constantly asking colleagues or dental nurse for help!)
  • communicate with other dental professionals (dentist/nurse/technician)
  • provides a framework for understanding materials
  • be able to address Health & Safety issues of materials used clinically (risks, allergic components)
  • manage patient expectations (aesthetics, longevity of restoration)
20
Q

3 property categories for dental materials

A
  • mechanical
  • chemical
  • physical
21
Q

3 consequences of a force being applied to a material

A
  • stretch/compress (depending on how force applied)
  • deform (temporary or permanent)
  • fracture (failure)
22
Q

force is…..

A

a mass on a tooth

gravity pulls the mass downwards - so exerting a downward force on the tooth

23
Q

3 types of force dental materials can experience

A

compressive

tensile

shear

24
Q

what is compressive force?

A

squeeze

25
Q

what is tensile force?

A

stretch

26
Q

what is shear force?

A

object bounded to another surface and apply a force, apply force along same parallel as object can leave a cavity)

27
Q

stress is…..

A

= force / unit area = F/A
unites Pascal - Pa=N/m2

squeeze cylinder, stress on cross sectional area

28
Q

strain is….

A

When a STRESS is applied to an object/dental material it will change shape slightly.
The material is said to undergo STRAIN
- change in dimensions

29
Q

proportional limit on a stress-strain diagram

A

up until this point stress and strain are linearly related

i.e. double stress = double strain

30
Q

Elastic (Young’s) Modulus measures

A

rigidity (stiffness)

YM = stress/strain
unites: MPa

higher YM means more rigid

31
Q

opposite of hard

A

soft

32
Q

opposite of strong

A

weak

33
Q

opposite of rigid

A

flexble

34
Q

opposite of brittle

A

ductile

35
Q

3 distinct properties of enamel

A
  • hard surface
  • strong
  • rigid
  • brittle
36
Q

what is the ideal behaviour of a dental material?

A

same as enamel or dentine

37
Q

action of biting

A

compressive force applied to upper tooth when biting

typical biting force= 500 to 700N

38
Q

action of grinding/chewing

A

tooth slides along the surface of the other

  • frictional forces experiences
  • everyday repeated episodes

can loose enamel surface integrity
- abrasion

39
Q

action of removal

A

material needs to adhere to enamel or it will be removed by masticatory forces

40
Q

enamel properties V dentine properties

A

enamel is stronger (higher fracture stress)

enamel is more rigid (higher YM and proportional limit)

41
Q

what type of cavity design is needed for amalgam?

A

undercut

  • splays outwards as carry downwards towards base of cavity
  • helps keep material in place
42
Q

what type of cavity design is needed for composite?

A

minimal

- no unsupported enamel

43
Q

what type of retention is used for amalgam?

A

mechanical

44
Q

what type of retention is used for composite?

A

adhesive

45
Q

what are the stages in material transformation for filling a cavity?

A

must be pliable, to fit shape of interest;

must set to form hard, strong material

46
Q

fracture failure mechanism

A

large force causes catastrophic destruction of material’s structure

47
Q

hardness failure mechanism

A

ability of surface to resist indentation (KHN)

48
Q

abrasion failure mechanism

A

material surface removal due to grinding

49
Q

abrasion resistance failure mechanism

A

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

50
Q

fatigue failure mechanism

A

repetitive ‘small’ stresses causes material failure

small flaws (cracks) in a material grow (propagate), allowing fracture when only a relatively small force is applied

51
Q

creep failure mechanism

A

gradual dimensional change due to repetitive small forces

52
Q

deformation failure mechanism

A

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

53
Q

de-bond failure mechanism

A

applied forces sufficient to break material-tooth bond

54
Q

impact failure mechanism

A

large, sudden force causes fracture

55
Q

hardness test

A

a weight pushes an indenter
- which has a distinctively shaped end into the material surface, causing a notch to form. The bigger the dimensions of the notch the softer the material

hardness different to other mechanical properties involving stress - to do with surface

56
Q

abrasion

A

tooth grinds/slides along the opposing tooth surface (or restorative material)

loss of material surface layers causing a roughened surface

57
Q

how is a surface roughness colour map made?

A

profilometer

- stylus running along the material surface

58
Q

permanent deformation

A

stress exerted is greater than the Elastic Limit

  • Material cannot return to normal shape
  • bigger
  • permanently deformed
59
Q

elasticity example - impression material

A

tooth surrounded by impression material and then impression tray
to remove impression tray from mouth the material needs to overcome the bulbosity of the teeth
- needs to change shape and splay outwards

ideally return to original shape when removed

60
Q

when is de- bonding needed in a material?

A

to remove orthodontic appliance,
shear force is applied to separate bracket/bonding material from tooth surface

  • Interested in how well the bracket adheres to the tooth - will it crack
61
Q

3 chemical characteristics of dental materials

A
  • setting mechanisms
  • setting time
  • corrosive potential
62
Q

5 physical characteristics of dental materials

A
  • viscosity
  • thermal conductivity
  • thermal expansion
  • density
  • radiodensity
63
Q

what do we need to know about each dental material?

A

it’s ‘ideal’ properties

so we can try and predict how it will behave and manage patient expectations

64
Q

conditions to consider in the oral environment

A

variable environment

  • saliva
  • temperature
  • pH
  • oral bacteria
65
Q

retrospective clinical evidence

A

uses real clinical data from range of GDPs, but with no control over the exact method used

66
Q

prospective clinical evidence

A

uses defined protocol, motivated clinicians, unrealistic for actual practice use

67
Q

issues with gathering clinical evidence

A
  • time-consuming
  • costly
  • limited in scope: retrospective/prospective

Means there is less robust evidence for the performance of dental materials in vivo than we’d like