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Properties of Dental Materials
Contributed by:
Andrea
SDH PRCC, MS.
- Who establishes
acceptable minimum standards for dental materials? American National
Standards Institute, ADA, FDA
- Dimensional Change:
shrinkage or expansion of material. Important in accuracy of materials
- Heat = expand
- Cold= Shrink
- Percolation: forcing
in & out of fluids
- Microleakage:
restoration does not expand or contract at the same rate, leakage will
occur. Result is percolation
- Ideally the tooth and
restoration should expand shrink at what rate? Same rate
- Coefficient of thermal
expansion: # assigned to materials
- Thermal conductivity:
rate at which heat / cold is transferred through a material. Higher values
are good conductors.
- A base is a poor
thermal conductor
- Galvanism: electric
current generated between 2 different metals in the presence of an
electrolyte (saliva)
- Corrosion:
electrolytic or chemical attack of metal surface (warm moist environment)
- Tarnish: chemical
attack, surface discoloration
- Galvanic shock does
not cause: gingival inflammation or redness
- Very important
concepts for cements: solubility & sorption
- Solubility: capable of
being dissolved
- Sorption: takes up
liquid & holds it
- Wettability: measure
of the affinity of a liquid for a solid
- Hydrophilic: water
loving
- Hydrophobic: water
fearing
- Contact angle: measure
of wettability
- Low contact angle:
solid is hydrophilic
- High contact angle:
solid is hydrophobic
- Biting forces:
pressure increases as we move back in the mouth
- Stress= force/area
- If you increase the
area you decrease the stress
- If you decrease the
area you increase the stress
- Compressive: squeezing
together
- Tensile: pulling apart
- Shear: twisting. One
side forced against another.
- Strain: deformation
caused by stress.
- Elastic Modulus,
elasticity: ability of a body that’s deformed under stress to go back to its
original shape.
- Proportional limit:
bounces back
- Yield strength:
permanent
- Materials are elastic:
below the proportional limit.
- Materials are plastic:
above the yield strength.
- Ultimate strength:
stress at which fracture occurs.
- Elongation &
compression, ducility: can be shaped under tension.
- Elongation &
compression, Malleability: can be shaped under compression.
- Resilience: springs
back, capable of returning to its original shape after being stressed.
- Toughness: Resistance
to fracture is a measure of toughness.
- Hardness: ability of
material to resist an indenting load. Enamel Porcelain
- Strain time curve:
faster stress is applied the more likely the material is to store energy
elastically & not plastically
- Knoop Hardness Test:
common hardening test commonly used in dentistry.
- Softest: acrylic
- Whenever the is stress
there is strain
Disclaimer: These notes
were copied and pasted from files sent to me by Andrea. They have not been
reviewed for errors. You are responsible for checking out the information to
verify the accuracy. This site, Amy Nieves and Andrea are not responsible for
typographical errors.
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