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Biomaterials > enamic > Flashcards

enamic Flashcards

1
Q

what is enamic
% what by volume?
what is it not

A

INTERCONNECTED NETWORK

  • CERAMIC 75%
  • POLYMER 25%(BY VOLUME)
  • interconnected network of polymer and ceramic

NOT a composite resin
NOT a conventional ceramic

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2
Q

think of what when see inter-connected network?

A

ENAMIC

- this will be a test question

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3
Q

occlusal reduction needed for enamic

A

1

70 - translucency

inlay/onlay / crown / implant restoration

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4
Q

*penetrating phase materials like enamic will resist crack propagation due to?

A

THE INTERCONNECTED CERAMIC AND POLYMER PHASES

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5
Q

occlusal reduction needed for e. max

A

1.5

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6
Q

downfall to zirconia

A

easy to make so might not all be as good

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7
Q

implication of temperature on structure for zirconia

A

different phases / crystal structure at different temperatures

Monolithic - largest at room temp.

Tetragonal - intermediate at 1170 degrees celcius

Cubic - smallest at 2370 degrees celcius

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8
Q

*pure zirconia with no added stabilizers is useful in?

A

for paint pigments and polishing materials

not really good at pure – sand at pure

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9
Q

zirconium? vs zirconia?

A

zirconia is the oxidized version of zirconium (zirconium is metal and now it is not)

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10
Q

when is zironia partially stable at room temp? what form? how?

A

adding yttris by 3-5%

  • tetragonal –PARTIALLY STABLE AT ROOM TEMP
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11
Q

when is zirconia fully stable?

A

cubic zirconia

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12
Q

describe transformation toughening with zirconia

A

basically though stress application
- go from tetragonal (yttria partially stable zirconia )– to monolithic

3% volume increase

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13
Q

warping is a result of?

A

non-uniform density in the zirconia blocks

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14
Q

Zirconia FDA standard?

USA ADA?

A

only FDA 510 K

usa ADA - #131 - machinable zirconia blanks

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15
Q

zirconia must meet which standards?

A
  1. density is equal throughout
  2. shrinkage factor can be accurately measured
  3. furnace – sintering schedule
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16
Q

implication of sintering too long

A

more translucent – BUT BIG crystals – cubic crystals and becomes weaker

17
Q
  • highly stabilized zirconia resists crack propagation by which type of crystal transformation?
A

tetragonal –> monolithic

intermediate size to larger size

18
Q

how to make zirocnia more translucent

A

add yttria – more cubic

3- 5 %
3% is original

19
Q

effects of surface treatments on strenth of various zirconia?

A

the more sand blasted / treated the surface – got higher failure rate (especially in the higher translucent ones)

20
Q

as translucency increases what happens to crystal size?

A

also increases

  • so less resistant
  • yttria increases
21
Q

implication of yttria increasing?

A

weakening

22
Q

occlusal reduction needed gfor zirconia?

high translucency zirconia? ultra translucency zirconia?

A

normal - .8

high - ,8

ultra - 1.0

23
Q

concerns with monlithic full contour zirconia

A
  1. enamel wear
  2. occlusal adjustment
    - weaken zirconia
  3. zirconia degredation
24
Q

after 1 year started seeing degradation why?

A

because the glaze was wearing off

- but if you POLISH it before glaze - this can be avoided more

25
Q

elevation in the surface due to?

A

transformed surface under stress from tetragonal to monoclinic – because monclinic due to its structure being higher

26
Q

why should ALL restorations be polished?

A

because stains and glaze wear off over time

27
Q

glaze applied to ceramics tends to last?

A

about 3 years

28
Q

what to do with full contour zirconia before insert? with lab? what if chairside?

A

lab
- polish the zirconia and then apply the glaze

if chairside
- check restoration and opposing dentition annually

grind into zirconia – ideally polish and re-glaze

grind into the zirconia intra-orally – with ZR wheels, paste, water spraay, LOW SPEED

29
Q

Does zirconia have low thermal conduction? implication?

A

YES – could lead to fracture

30
Q

why do ceramic resotrations fail?

A

INDEQUATE PREPARATION

  • too thin
  • not enough load bearing capacity then

SHARP ANGLES
- concentrates stress
fracture sites

IMPROPER FABRIICATION

  • Not following directions
  • sub standard materials
  • excessive adjustment
  • incorrect polishing (surface was left ground with diamond burs)

POOR BONDING TECHNIQUE

MATERIAL SELECTION

  • inadequate properties for clinical
  • canine- molars - need more high stress

Biomaterials (16 decks)

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