Answer the Following Dental Materials Midterms of 2020 Flashcards

20 cards   |   Total Attempts: 188
  

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Cards In This Set

Front Back
Ingredients of Alginate (Aqueous elastomeric impression material like Agar)
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Advantages & disadvantages of Alginate
Pros:
  • easily "wets" tooth structure due to H2O (hydrophilic)
  • easy to "pour" in gypsum material
Cons:
  • irreversible hydrocolloid
  • H2O evaporates fast
  • impression shrinks - loss of accuracy (pour soon after disinfection)
  • Syneresis - H2O loss
  • Imbibition - H2o absorption
Classification of Caries & GV Black
  • I - Posterior occlusal
  • II - Posterior interproximal
  • III - Anterior interproximal
  • IV - Anterior incisal angle
  • V - Gingival third
  • VI - Posterior or anterior worn cusp tips
Answer 3
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Electron bond types - Primary
​Ionic bonds
  • simple chemical bonds resulting from mutual attraction between + and - charges
  • an atom gives up one of its E- which is accepted by another atom in short supply (ex. NaCl)
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Covalent bonds
  • 2 valence electrons are shared
  • tend to be strong (ex. H20)
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Metallic bonds
  • forces of attraction between free-floating valence e- and positively charged metal cat-ions
  • easily identifiable
  • similar to covalent bonds in that they also share valence e- between atoms
SECONDARY BONDS
  • aka van der Waals forces
  • tend to be weaker than primary bonds
  • considered to be more physical than chemical (DO NOT share e-)
  • Van der Waals forces are due to the formation of a dipole, can be fluctuating or permanent
Note:
  1. Ceramics - ionic bond
  2. Metals - metallic bond
  3. Molecular solids (polymers) - covalent & secondary bonds
Cross-linking
The linking of one coil (or polymer chain) across to another with wire (or a covalent bond)
  • ex. rubber band: more cross-linking = stiffer
Polymerization
Free radicals, that add together (double bond)
Linear coefficient
Coefficient of thermal expansion?
  • Measure of the change in volume in relation to the change in temperature
Modulus of elasticity = stress/strain
  • Characteristics of a material and its atomic bonds
  • High modulus of elasticity = stiff material
Question 13
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Answer 13
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Yield strength
  • "elastic limit" or "proportional limit"
  • the point on the stress-strain plot at which the line starts to curve and plastic deformation (not returning to original shape) begins
Plastic deformation limit
Point where it is permanently stretched out