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PRD 131 > PRD 131: zirconium, amalgam > Flashcards

PRD 131: zirconium, amalgam Flashcards

1
Q

what are the biologic considerations for treatment planning single crown restoration

A
  • remaining tooth structure
  • vitality of pulp
  • periodontium and surrounding structures
  • occlusion & function
  • prognosis
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2
Q

what are properties of restorative materials to consider

A

thermal conductivity

  • strength
  • expansion or shrunk
  • resistance to wear: attrition, abrasion, chemical erosion
  • good bonding to tooth
  • radiopacity or radiolucent
  • esthetics
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3
Q

how does lost wax technique work

A

restoration is waxedm a mold is formed from the wax.
-then casting is when restorative material (gold) is liquified using high heat and poured into a mold. mold contains a hollow cavity of the desired shape. after pouring material allowed to solidify. the solidified part is termed casting, which is taken out of the mold to complete the process .

-cd

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4
Q

what is milling fabrication type

A

chairside or lab processed - dental mills are designed to fabricate restorations from materials such as ceramics- including zirconia and porcelain . milling can be in lab or in office.

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5
Q

what are the 3 ceramic classifications and wha they mean

A
  • glass : highly esthetic
  • particle-filled glass: filter added to glass matrix , thisimproved mechanical properties
  • polycrystalline: contains NO glass

-evolved from glass to polycrystalline in history

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6
Q

what are the properties of glass ceramics

A
  • low thermal conductivity
  • low tensile strength, poor mechanability
  • high transperancy, high brittleness,
  • poor impact strength
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7
Q

how do esthetics and strength change with glass

A

more glass - more aesthetic

more glass - less strong !

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8
Q

what is feldspathic

A

glass ceramic type

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9
Q

what are examples of glass ceramics with fillers?

A

-leucite reinforced lithium disilicate

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10
Q

wha tare examples of glass free ceramics and what are these called

A

POLYCHRYSTALLLINE:

  • alumina
  • zirconia
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11
Q

when would you use lithium disilicate vs zirconia and hwy

A

zirconia is stronger, would use on posterior teeth. lithium disilicate is more aesthetic so would use for when esthetics are a concern-anterior/premolar area. (160 mpa vs 900 mpa)

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12
Q

what is the usual material of choice for single unit crowns?

A

zirconia
could be monolithic and solid or biolithic and layered
-used to be ugly but now they made them better with color/translucency

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13
Q

what to consider regarding monolithic zirconia

A
  • wear
  • surface roughness
  • fracture strength
  • oprtical properties
  • marginal fit
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14
Q

what are the pros/cons of monolithic zirconia

A
  • good chemical properties and dimensional stability
  • high mehcanical strength and toughness- high flexural strength
  • enhanced translucency (starting to look better) but not as good as lithium disilicate
  • can be abrasive - need proper finish and polish
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15
Q

what are the 7 principals of tooth prep for all restorations

A
  • conservation of tooth
  • retention form
  • resistance form
  • structural durability
  • marginal integrity
  • preservation of periodontium
  • aesthetics
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16
Q

what are other names for monolithic zirconia

A

-monolithic zirconia crown, full zirconia crown, full crown zirconia, monolithic zirconia restoration, full veneer zirconia

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17
Q

when would you use a zirconia crown?

A
  • ideal if patient wants a conservative prep but doesn’t want gold /metal crown.
  • if patient doesnt have adequate preparation space for a PFM and require conservatio nof tooth, dont want metal basically.
18
Q

what are the criteria for a zirconia crown: occlusal reduction, axial reduction, margin, margin location, and taper (ideal)

A 
occlusal reduction: 1.5
axial reduction: 1 mm
margin: .8mm heavy chamfer
margin location: .5mm above gum
taper: 6 degrees
19
Q

what is the composition of amalgam %s

A

silver: 40-70% by weight
tin: 12-30% by weight
- copper: 12-30% by weight

zinc is also in there to reduce oxidation
palladium reduces tarnish, builds early strength
indium strengthens

mix with metal of 41-50% by weight of mercury

20
Q

what is lathe cut alloys properties? whats it used for

A

alloy (powder)
– lathe cut was formerly used- irregular pieces, stiff material, resists condensation (packing of material), good contacts-> resists deformation

21
Q

what is spherical alloy?

A

used to use this powder (alloy)- heat up hot, solidified from there

  • droplets
  • fast setting
  • good adaptation
  • slippery, not as good contact w other tooth
22
Q

what is admixed powder?

A

combination of lathe cut and spherical! now its used- only thing on market now:
-good all around properties

23
Q

what is mixed to make low copper alloys? when are they used

A

previously used!! combining agsn (silver and tin) with mercury

24
Q

what are the intermetallic compounds formed/ chem reaction of mixing low copper alloy

A

Ag2Hg3 and Sn8Hg are formed ..

Hg dissolves Ag and Sn from the alloy (dissolution and precipitation)

25
Q

what is the initial powder that gets mixed with mercury for low copper alloy called ? what % of set amalgam does it make up ? and what is an important feature?

A

Gamma = Ag3Sn

  • forms 30% of set amalgam
  • strongest phase and corrodes the least!

(also initial powder in admixed high copper alloys)

26
Q

WHAT IS gamma 1?

A

intermetallic compound formed in low copper alloy reaction.

  • precipitates on unreacted alloy
  • second strongest phase
  • 10 micron grains binding gamma
  • 60% of the volume

(also formed in admixed high copper)

27
Q

what is gamma 2?

A

intermetallic compound formed in low copper alloy,

  • weakest and softest phase
  • corrodes fast, voids form
  • corrosion yields Hg which reacts with more gamma
  • 10% of volume
  • volume decreases with time due to corrosion
  • becomes HgCl2
28
Q

what are the reactants and products of admixed high copper alloy mixture amalgam

A

Ag-Cu alloy (spherical) and Ag-sn alloys are reacted with mercury
-both Ag and Sn enter Hg from Ag3sn particles when all mixed.

reaction results in agcu, ag3sn, ag2hg, cu6sn5

(NO GAMMA 2!)

29
Q

how does Cu6sn5 get formed when admixed high copper alloys mix

A

Sn diffuses to surface of Ag-Cu particles and reacts with Cu to form Cu6Sn5 around unconsumed Ag-Cu particles (surface)

30
Q

why is admixed high copper better than low copper?

A

because no gamma 2 is formed in that reaction (instead of tin and mercury, we get copper and tin combining)
-this is good bc gamma 2 corrodes and is soft etc

31
Q

what type of amalgam do we use at pacific

A

admixed- palladium enriched, high copper

32
Q

what would happen if you over triturated the amalgam

A
  • rapid hardening and shortened working time!
  • also setting contraction less than 1%, but thats not clinically relevant
  • also has higher compressive strength
33
Q

what happens if youo under triturate the amalgam

A

it will be crumbly, grainy

  • excessive free Hg will be present
  • decreased compressive strength
  • increased setting expansion
  • increased corrosion
34
Q

what does condensation of amalgam do

A

packing aka

  • drives out trapped air
  • presses out excess mercury
  • creates tooth form
35
Q

how long after amalgam rest is it fragile

A

10 hours!!

durable after 1 day

36
Q

what are pos/negs of amalgam restorations

A

positive:

  • super durable after day 1
  • resistent to recurrent caries/corrosion

neg:

  • doesnt bond to tooth; no macromechanical retention
  • requires bulk
  • chips at margin (flash and deformation)
37
Q

what was used in the 1960s for amalgam

A
  • convnetional low copper lathe cut alloys! smaller particles. and
  • first generation high copper alloys : dispersalloy, admixture of spherical ag-cu eutectic particles (n) with conventional lathe cut. (eliminates gamma 2 phase)
38
Q

whta are the local/environmental controversies around amalgam

A
  • local; dental providers and amalgam bearers (patients)

- environmenta; mercury entering environment from dental sources

39
Q

what is the risk with health efffects of mercury on amalgam bearers

A
  • initial placemet: vapor, swallowed

- chronic: vapor, tattoos!

40
Q

what are the health risks for mercury on dental providers

A

vapor from stored hg, mercury hygiene taking care, aerosols (during removal)

41
Q

what are the mercury facts we need to know regarding accumulation, excretion, half life, neural defects in dental providers, margin of safety

A
  • mercury accumulates in specific tissues like kidneys
  • mercury excretion is NOT indicative of mercury load (urinary or blood)
  • half life in neural tissues is many years
  • subclinical neural defects in dental providers
  • margin of safety is debatable
  • there have been no clinically measurable/relevant effects of mercury levels in amalgam bearers
  • its very beneficial and superior to affordable alternatives in many situations
42
Q

how does mercury get harmful in the environment from dental amalgam

A

dental amalgam -> waste water, urine and feces also to waste water , cremation and waste incineration
-> atmospheric deposition and storm water runiff (from cremation and waste incineration)

-> methyl mercury formaton (from wastewater anda atmospheric deposition and storm water runoff)

–> methyl mercury bioaccumulation in food web leads to human and wildlife exposures

PRD 131 (25 decks)

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