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Biomaterials > values we need to memorize > Flashcards

values we need to memorize Flashcards

1
Q

flexural strength requirement for polymer based type 1 (occlusal, self cure, dual cure) type 2 (occlusal and luted) , type 2 ( other)

A

type 1 – 80

type 1 - class 2 –> 100

type 2 - 50

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2
Q

flexural strength requirement for monolithic ceramic single unit anterior

A

50

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3
Q

flexural strength requirement for monolithic single unit anterior or posterior prosthesis

A

100

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4
Q

flexural strength requirement for three unit NOT involving molar

A

300

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5
Q

flexural strength requirement for three unit involving molar

A

500

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6
Q

flexural strength requirement for monolithic ceramic of FOUR OR MORE UNITS

A

800

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7
Q

which materials are tough? which are low toughness?

A

high – fiber reinforced material, zirconia

low tough – porcelain glass

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8
Q

non-resiliant materials and resiliant

A

non– pure copper

high resiliance - spring steel

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9
Q

units in fracture toughness

A

MPa * m^1/2

not meters squared but square root

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10
Q

K1c?

A

type 1 shear critical stress intensity factor

higher value correlates to better fracture resistance

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11
Q

materials usually test higher with compressive or tensile force?

A

Compressive

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12
Q

tensile and compressive strength of porcelain

A

tensile - 65

compressive - 149

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13
Q

tensile and compressive strength of amalgam

A

tensile - 124

copressive - 318

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14
Q

tensile and compressive strength of composite resin

A

tensile - 140

compressive 237
*high

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15
Q

tensile and compressive strength of dental gypsum

A

tensile - 60

copressive - 81

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16
Q

compressive strength of enamel

A

384

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17
Q

T/F Zirconia has a high mean flexural strength

A

True – it is resistant to crack propagation

- good for uses in the posterior

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18
Q

when doing a PFM if the preparation is too thin will the final product look overcontoured or grey?

A

BOTH – if dont prep enough the restoration will be too bulky and metal will also shine through - looking grey

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19
Q

importance of condensation

A

water removal and then can have more particle packing - better bonding between

20
Q

vacuum sintering?

A

gas bubbles escape via grain boundaries and the vacuum will reduce the bubble size

so the vacuum helps to get the remaining air out of porcelain and make it more dense

improves the translucency and strength

21
Q

strength and translucnency are affected by?

A
  1. firing procedures

2. condensation / powder packing

22
Q

three bonds in PFM crown

A
  1. shrinkage stress
    - as shrinks grabs onto metal
  2. mechanical interlock
    - rough surface to increase adhesion
  3. chemical bonding
    - oxide layer
23
Q

what if there is a thermal coeffiecient mismatch?

A

failure of the bond

24
Q

major way to improve materials

what is result

A

through microstructure

prevent crack growth and fracture

25
Q

problems with porcelain

A
  1. brittle and porous
  2. shrinkage of 10/15% linearly and 30/40% volumetric
    - deformation
  3. weak
    - metal framework is required making translucency harder to obtain
26
Q

devitrification?

A

seen with PFM’s porcelain - can turn green color

27
Q

dispersion is a way to?

A

increase strength

28
Q

dispersion strengthening?

A

adding a crystalline phase to the glass

  • glass ceramics
  • aluminous porcelain

to get

  • crack deflection
  • energy absorption
29
Q

heat treating?

A

can do this with glass

  • increase the compressive strength
  • with heat you will get separaion and then can fill this with crystals
  • helping stop craack propagation
30
Q

three major benefits seen with smaller particle size

A
  1. stronger
  2. low wear to opposing dentition
  3. improved polishing and surface finish
31
Q

factors affecting the ware

A
  1. hardness
  2. crystal size
  3. surface finish
    - polish
    - stain
    - glaze
  4. environment
32
Q

processing of ceramics now (standards)

A

40-80 icrons
powder size
colloidal processing

33
Q

T/F polishing can increase flexural strength of veneering porcelains

A

TRUE – also increases the fracture resistance of the ceramic

34
Q

toughening does what? general

A

improves ceramics

35
Q

how does toughening improve ceramics?

A

Surface compression

  • work hardening
  • glazing
  • ion exchange
36
Q

does staining improve strength?

A

NOT WHEN DONE ALONE

-if you just do this you will be left with a rough surface

37
Q

what is staining?

A

application of a surface colorant and uses metal oxide and some glass

38
Q

polish - general

A

smooth surface - defect elimination

39
Q

self glaze?

A

rely on ‘melting glass’ in the porcelain

40
Q

over glazing?

A

apply a separate glass powder, may further improve strength

41
Q

glaze - general

A

melt glass and can strengthen and can also protect the surface stain

but if do not polish this - it can ware away and then left with defects

42
Q

how long would glass glaze last?

A

2-4 years

43
Q

glazing of the porcelain can improve flexural strength by?

A

creating comopressive stress on the surface

44
Q

staining is designed for? what do you have to make sure?

A

designed to fire on a RANGE OF MATERIALS
- specific cycle dependent on porcelain materials

must make sure to calibrate furnace
- misleading firing temps

45
Q

color staining lasts usually?

A

3 years

46
Q

if you only stain?

if you stain and glaze?

A

only stain - rough

stain and glaze – glaze will ware off and be left with roughness so

MUST ALWAYS POLISH FIRST

47
Q

What can the overglaze accomplish?

A

STRENGHTENING

  • surface compressive stress
  • defects filled
  • lower the CTE
  • protect color stability

Biomaterials (16 decks)

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