Quiz 3 Flashcards
Which of the following is not a dental alloy
Mercury
Set dental amalgam is composed mostly of which phase
Gamma phase 1
Condensation
Increase in condensation pressure reduces voids and expresses Hg increasing strength
How do you minimize creep
Decrease Hg:alloy ratio, increase condensation pressure and carefully set titration time
Type I metal
Two metals that are completely soluble in the liquid state and completely soluble in the solid state
Good for dentistry!
Visoelastic material
In an idealized viscoelastic material, the elastic modulus changes at the rate at which loading is applied is varied.
For viscoelastic materials, stress is proportional to some function of strain and time.
Ex; amalgams, alginate, PDLigament, bone tissue
Type II metal
Two metals that are completely soluble in the liquid state and insoluble in the solid state
TONS OF CORROSION NEVER SINGLE PHASE
Type III metal
Two metals that are completely soluble in the liquid state and partially soluble in the solid state
For example; Aluminum-Silver, Copper-Silver alloy, Copper-Tin alloy (Bronze)
Grain size
Metal grain size is the function of solidification (cooling) process
Wrought metal
Wrought metal is formed when cast metal is subjected to a plastic deformation.
(e.g. wires become wrought metal after cast metal is drawn through a die.)
Cast metal
Most metallic restoration are cast metal, All metals originate from castings, Cast metal has stable grain size and will not be affected by heat treatment.
Most dental instruments are
Wrought metals
Annealing
Process of removing effects of cold work. Involves heating of a metal to a temp approximately 1/2 of its melting point.
3 stages; recovery, re-crystallization, grain growth
Chemical corrosion
Chemical corrosion is due to direct combination of metallic and nonmetallic elements such as: • oxidation • halogenation • sulfurization reactions
Electrochemical corrosion
Anodic and cathodic reactions
Oxidation, halogenation, sulfurization reactions all indicate what
Chemical corrosion
Anodic reaction
Corroding surface (oxidation reaction)
Give up e
Cathodic reaction
Metal forming surface (reduction reactions)
Four types of corrosion
Galvantic corrosion, intergranular corrosion, stress corrosion, pitting (concentration cell corrosion)
Viscosity of a fluid
Internal resistance to flow
Dental amalgam alloys
Copper, tin, zinc, and silver
Why did they make high copper amalgams
Gets rid of gamma 2 phase
Why is corrosion okay in some amalgams
It seals things off
Most important thing about placing amalgam
Condensing
Inadequate condensation pressure leads to what
Amalgam filling that falls out after removal of matrix
Know the Type three metal phase diagram
Grain size of a metal..
Is the function of solidification (cooling) process
Ductile has a _______
Larger plastic region
