Physical properties of dental materials Flashcards

1
Q

3 basic physical structures (forms) of dental materials (and all matter)

A
  1. solids: shape and volume
  2. liquids: volume and no shape
  3. gases: no shape and no volume
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2
Q

measuring solids

A
  • density
  • hardness
  • elasticity
  • stiffness
  • ductility (tensile strength)
  • malleability
  • brittleness
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3
Q

what is density

A
  • the compactness of a material
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4
Q

what is hardness

A
  • used to define a material’s resistance to wear and abrasion
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5
Q

what is elasticity

A
  • ability of a material to deform and then return to its original shape
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6
Q

what is stiffness

A
  • the resistance to deformation
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7
Q

what is ductility

A
  • tensile strength, the ability of a material to be pulled or stretched under tension
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8
Q

what is malleability

A
  • the ability to be compressed easily into a thin sheet
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9
Q

what is brittleness

A
  • materials with poor ductility
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10
Q

in general

A
  • metals = ductile and malleable

- ceramic = brittle

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11
Q

what is viscosity in liquids

A
  • the resistance of a liquid to flow (viscous material = decreased flow)
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12
Q

what is thixotropic materials (liquid)

A
  • liquids that flow more easily under mechanical forces
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13
Q

classifying materials by application as:

A
  • preventive
  • therapeutic
  • restorative
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14
Q

what is direct fabrication

A
  • fabricated directly in the mouth

- ie. amalgam, composite

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15
Q

what is indirect fabrication

A
  • fabricated outside of the mouth, then placed into the oral cavity
  • ie. crown and bridge, onlays, inlays, dentures
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16
Q

composition of materials can be:

A
  • water and powder
  • liquid and powder
  • paste and paste
  • paste and initiator
17
Q

reactions can be:

A
  • physical (evaporation or cooling of liquids)

- chemical (creating new primary bonds

18
Q

what is mixing time

A
  • the amount of time needed to bring the components together to form a homogeneous mix
19
Q

what is working time

A
  • the amount of time permitted to manipulate the material in the oral cavity
20
Q

what is the initial set time

A
  • begins when the material no longer can be manipulated
21
Q

what is the final set time

A
  • when the material has reached its ultimate state
22
Q

3 different types of setting:

A
  1. chemical-set materials: chemical reactions of a catalyst and a base
  2. light-activated materials: light initiates the reaction stage
  3. dual-set materials: begin with the initiation of a blue light source, then continue the set with a chemical reaction
23
Q

manipulation can be done:

A
  • quickly/slowly
  • on a paper pad/glass slab
  • handmixing/automix dispenser
24
Q

what is shelf life

A
  • the deterioration and change of quality of the material over time
25
Q

attention to date of expiry

A
  • important for consistency in the optimum characteristics of the product
26
Q

in summary

A
  • physical structure

- important to refer to the manufacturer’s directions for instructions in storage, proportioning, mixing