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Dental Materials > Metals in dentistry (Ch 10) > Flashcards

Metals in dentistry (Ch 10) Flashcards

1
Q

what is a metal

A
  • is any substance that is good conductor of electricity and heat
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2
Q

what is an alloy

A
  • any mixture of two or more metals
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3
Q

what is mercury

A
  • is a metallic element that is liquid at ordinary temperatures
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4
Q

what is amalgamation

A
  • is the reaction that occurs when a silver-based alloy is mixed with mercury
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5
Q

what is dental amalgam

A
  • a mixture of alloy and mercury

- safe, affordable and durable material used predominantly to restore premolars and molars

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6
Q

what are indications for using amalgam

A
  • in individuals of all ages
  • in stress-bearing areas of the mouth
  • when there is severe destruction of tooth structure
  • as a foundation for a crown
  • when oral hygiene is poor
  • when moisture control is problematic
  • when cost is an overriding factor
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7
Q

what are indications for not using amalgam

A
  • aesthetics is important
  • a history of allergy to mercury or other amalgam components
  • the cost of other restorative materials or treatment options is not a factor
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8
Q

what is the composition of amalgam

A
  • mercury (43% to 54%)
  • alloy powder (57% to 46%)
  • silver - strength
  • tin - workability
  • copper - strength and corrosion resistance
  • zinc - suppresses oxidation
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9
Q

what are the 3 types/shapes of alloy particles

A
  • lathe-cut alloy
  • spherical alloy
  • admix alloy: lathe cut and spherical
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10
Q

what are some advantages of spherical alloys

A
  1. less mercury to wet the particles

2. less time to set

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11
Q

what is the setting transformation process

A
  1. chemical reaction
  2. working time
  3. initial set
  4. final set
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12
Q

what are the 3 phases of chemical reactions in the setting transformation

A
  1. gamma phase
  2. gamma-1 phase
  3. gamma-2 phase
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13
Q

why does tarnish occur

A
  1. oxidation: oxygen, chlorides, sulfides in the oral cavity
  2. rough surfaces

other facts

  1. dark dull appearance
  2. not destructive to amalgam
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14
Q

what can cause a reduction for tarnish

A
  1. palladium
  2. finishing
  3. high copper
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15
Q

what causes corrosion

A

chemical reaction: oxidation, galvanism

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16
Q

where does corrosion takes place

A
  • between the metals within the amalgam
17
Q

what is creep

A
  • the gradual change in shape of the restoration
  • compression
  • pressure
18
Q

what is dimensional change (excessive contraction and excessive expansion)

A
  • excessive contraction: opens gaps at the margins and contributes to leakage of fluids bacteria
  • excessive expansion: pressure on the cusps, pain with biting pressure, could result in the fracture of cusps
19
Q

what are some issues concerning amalgam

A
  • harm to patients: essentially harmless, the exception is with patients who have many amalgam restorations or a high sensitivity to metals
  • harm to dental personnel: health concerns with high exposure to mercury, not amalgam
20
Q

what are some signs of high mercury exposure

A
  • tremors
  • kidney disfunction
  • depression
  • nervous system disorders
21
Q

what are some guidelines for hygienists using mercury

A
  • do not contact mercury with your skin
  • protect against spillage during trituration
  • do not discard scrap amalgam into waste containers
  • collect all scrap and store in a closed containers
  • suction scrap amalgam
22
Q

what is involved in preparation of amalgam

A
  • capsules: 600 mg of alloy for small or single-surface restorations; 800 mg of alloy for larger restorations
  • activator: used to break the separating membrane in the capsule
  • trituration: the process by which the mercury and alloy are mixed together to form the mass of amalgam
23
Q

what is the process of direct application of amalgam

A
  1. mixed amalgam placed
  2. amalgam carried to the prepared tooth
  3. amalgam placed in increments in the prepared tooth
  4. each increment is condensed immediately
  5. carvers are used to carve anatomy into the amalgam
  6. a burnisher is used to smooth the amalgam
  7. the new restoration’s occlusion is checked
24
Q

look over images in ppt

A

look over images in ppt

Dental Materials (18 decks)

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