Dental Materials NBDHE Graded A+ - Adhesion: Refers to the attraction between molecules of different substances. - Cohesion: Describes the attraction between molecules of the same substance. - Coefficient of thermal expansion: Indicates how a material responds to temperature changes relative
to a...
Dental Materials NBDHE Graded A+
- Adhesion: Refers to the attraction between molecules of different substances.
- Cohesion: Describes the attraction between molecules of the same substance.
- Coefficient of thermal expansion: Indicates how a material responds to temperature changes relative
to another material.
- Compressive Strength: Measures the maximum force a material can withstand under compression
before breaking.
- Creep: Describes the gradual deformation of a material under constant load or stress.
- Ductility: Refers to a material's ability to deform under stress without fracturing.
- Elasticity: Indicates a material's ability to return to its original shape after deformation.
- Galvanism: Occurs when an electrical current is generated by the interaction of dissimilar metals in an
acidic environment.
- Gelation: Refers to the process by which a substance changes from a liquid to a gel state.
- Imbibition: Describes the absorption of a solvent by a gel or solid material.
- Malleability: Refers to a material's ability to be hammered or rolled into thin sheets without breaking.
- Microleakage (percolation): Describes the passage of fluids or bacteria into and out of tooth structure
due to gaps or failures in the seal of a dental restoration.
- Polymerization: Refers to the process of forming larger molecules by linking smaller ones through
chemical reactions.
- Proportional limit: Indicates the maximum stress a material can withstand while still remaining elastic
and able to return to its original shape.
Syneresis ✔️Contraction of a gel due to the loss of a solvent
Tensile strength ✔️The force needed to stretch a material to the point of fracture
Viscocity ✔️Resistance to flow
Amalgam ✔️By definition: an alloy of mercury
In dentistry: an alloy of mercury with silver, copper, tin, and zinc
Silver, a base metal, susceptible to corrosion
, Copper added to minimize the corrosion (gamma II phase eliminated)
Amalgam desirable features ✔️Durable
Similar compressive strength to enamel
Relatively inexpensive
Amalgam undesirable features ✔️Unattractive
High thermal conductivity
Dimensionally unstable (creep)
Delayed expansion if contaminated by saliva
Requires tooth support
Fracturable by excessive occlusion
Susceptible to galvanism when new
Polishing Amalgam ✔️Move from coarse to fine agents to remove surface tarnish, stains, flash and
roughness
Polishing can reduce rate of corrosion (less surface area)
Final polish in mouth is tin oxide
Use light touch with water and short bursts to avoid odontoblast damaging heat
Ways to avoid amalgam overhang formation ✔️Using properly placed band and wedge(s)
Detect overhang with explorer
Bonding agents; Dental Resins (BIS-GMA* or urethane dimethacrylate) ✔️Establishes micro mechanical
retention with enamel and dentin by adapting to relief areas created by conditioning with phosphoric
acid
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