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Dental Laboratory
Materials
Impression Materials
• Impression materials are substances that are
used to take and record the shape, size, or
position of teeth, appliances, and oral
anatomy. These materials may be rigid, plastic,
or elastic.
Types of Impression Materials
1- Rigid Impression Materials:
Rigid impression materials are used where no
teeth are present, and material flexibility is
unnecessary.
Types of Impression Materials
2- Plastic Impression Materials
Plastic impression materials are used with or
without the presence of teeth. This movable
material is employed where some material
flexibility is needed for the impression.
Types of Impression Materials
3- Elastic Impression Materials
Elastic impression materials are used where
teeth are present and material must be
flexible for removal from the oral cavity or
teeth.
Types of Impression Materials
4- Elastomeric Impression Materials
Elastomeric impression materials are used to
make impressions of preparations and for
demanding or accurate reproductions. These
substances are composed of a base and an
accelerator, or catalyst (substance that speeds up
the chemical reaction) and can be measured,
mixed, and placed in a tray or syringe for use in
the mouth.
Dental Polymer Materials
• Dental polymers, known
acrylics, are the result
monomer and polymer
union of these chains is
known as curing.
as a synthetic resins or
of a chemical union of
substances. The chemical
called polymerization, also
Dental Polymer Materials
• Among the substances included in the polymerization process
are the following:
• filler: inert substance added to the polymer to alter or modify
the polymer properties.
• Initiator (agent capable of starting polymerization process):
• may be light, heat, radiation, or chemicals.
• activator: reacts with initiator to start polymerization.
Dental Polymer Materials
• Inhibitor
(substance
that
prevents
polymerization): maintains storage life.
• Plasticizer (substance that causes a softening
effect): changes hard, brittle resin into a
flexible, tough material.
• composite: polymer matrix bonded to glass
particles; used for dental restorations.
Dental Polymer Materials
• self-curing resins: autopolymerization
materials that perform the uniting process by
means of a chemical union; the activator is
present in the polymer powder or base and
does not have to be added.
• heat-cured resins: acrylic materials are united
but need outside heat to set up;
Precious and Base Metals
• Many different metals are used in dental
procedures. Some are used in their pure state,
and others are used in combination with other
metals. A combination of two or more metals
is called an alloy
Precious and Base Metals
• Metals are classified as precious metals or
base metals. Precious or “noble” metals—
gold, platinum, palladium, and silver—are
used for crowns, bridges, and dental
appliances.
Precious and Base Metals
• Base metal alloys contain less than 25% of
noble metals and usually consist of chromium,
nickel, and cobalt. They are used in partial
denture frameworks or as substitutes for gold
alloy.
Characteristics of Dental
Laboratory Materials
• Bonding: force of the union of one substance
with another substance.
• Creep: tendency of amalgam to deform under
constant applied pressure.
Characteristics of Dental
Laboratory Materials
• Cure process: hardening of the material
through auto- (chemical) or light-activated
response.
• Ductility: ability of the material to withstand
permanent deformation without fracturing
under elongation stress.
Characteristics of Dental
Laboratory Materials
• Elasticity: ability of a material to return to its
original form when stress is removed.
• Exothermic : chemical release of heat, as in
zinc phosphate cement.
• Trituration: mixing of mercury with other alloy
material to form an amalgam.
Characteristics of Dental
Laboratory Materials
• Flow: slow bending or movement of material
under its own weight.
• Galvanization: tendency of certain metals to
produce an electrical charge when in contact
with each other.
• Toughness: ability of the material to resist
fracture.
Characteristics of Dental
Laboratory Materials
• hardness: maximum amount of resistance before
penetration or scratching can occur.
• Hydrophilic (ability to attract and hold water):
absorption of water.
• Hydrophobia (fear of water): giving off or
shedding of water.
Characteristics of Dental
Laboratory Materials
• Initial set: period of time when material
assumes shape but remains pliable.
• Imbibition (absorption of fluid): taking on of
water.
• Malleability: ability to withstand deformation
without fracture while undergoing maximum
compression stress.
Characteristics of Dental
Laboratory Materials
• Setting time: amount of time required for the
material to become as hard as it will be.
• Tensile strength: maximum amount of pulling
stress required to rupture the material.
• Thermal conductivity: capability of the
material to transmit heat.
Characteristics of Dental
Laboratory Materials
• Working time: period during which a material
can be molded, shaped, or manipulated
without any adverse effect upon the material.
• Yield strength: maximum amount of stress a
material can withstand without deformation.