Chp 2 Physical and mechanical properties

  1. Atomic bonds
    • —defined as how the atoms relate to each other
    • —determine the strength of a material
  2. Describe the properties of gases
    • 1.very weak atomic bonds between the molecules
    • 2.disorganized molecules – no molecular organization
  3. Describe the properties of liquid
    • —have stronger attraction between molecules than gas
    • —short range order between molecules – a consistent arrangement among molecules 5 to 10 neighbors apart
  4. Describe the properties of solids
    —Strongest attraction between atoms and molecules
  5. What are the two types of solids
    • Crystalline Solids
    • Amorphous Solids
  6. What are the properties of crystalline solids
    • —strongest attraction between atoms and molecules
    • —have both long range and short range order
    • —includes diamonds, table salt, metal, hydroxyapatite of bone, and hydroxyapatite of teeth
  7. What are the properties of amorphous solids
    • —same strong atomic bonds as crystalline solids, however….—only exhibit short range order
    • —examples – glass in a window, dental mirror
  8. What are primary bonds
    are the strong bonds between atoms involving the transfer or sharing of electrons between atoms
  9. What are the three types of primary bonds
    • Ionic Bonds
    • Covalent
    • Metallic
  10. What kind of bonds make up bone and teeth
    Ionic bonds
  11. Define ionic bonds
    • the result of an electron being given up by one atom and accepted by another.
    • Positive and negative ions attract each other
  12. Define covalent bonds
    • a pair of electrons are shared between 2 atoms
    • bond of choice in fats, proteins, and carbohydrates
  13. Define metallic bonds
    • specialized covalent bond where electron is shared by ALL atoms of the object
    • a solid crystalline mass
  14. What is a secondary bond
    • —also known as van der Waals forces. The result of partial charges from an uneven distribution of electrons around an atom or a molecule
    • Ex. Hydrogen Bond
  15. What are the properties of metals
    • A great example of a crystalline solid
    • —Properties are due to the metallic bond
    • Long range spatial arrangement with the electron being shared by all the atoms allows molecules to slide past each other
    • —Electrical charge distributed throughout the entire mass of the metalhen metal is bent-
  16. What are the features of metals
    • —Thermal and electrical conductivity
    • —Ductility—
    • Opacity
    • —Luster
  17. What are the properties of ceramics
    • —Composed of ionic bonds—
    • When flexed, the ions break apart
    • Strong attraction over the short order
  18. What are the features of ceramics
    • —Highly esthetic—
    • Very strong when compressed but
    • —Brittle (opposite of ductile) when bent or pulled
    • Good insulators
  19. What are the properties of polymers
    • Long chains built out of covalently bonded  repeating units called monomers
    • Man made materials. Acrylics
    • Used as denture bases, impression materials, restoratives
    • Insulators, variable physical properties depending on monomers used
  20. What are composites
    • a mixture of 2 or more materials (each material is called a phases) where mix is better than any individual component
    • —use as restorative, sealant, cements, bases
    • —composite fillings are an example of a composite mixture—
    • so are amalgam (silver) fillings
  21. Suspension
    Large particles mixed in a liquid, sand in water or dust in the air. Particles are visible and can be filtered out. Will settle out if left undisturbed
  22. What are colloids
    are a mixture like a suspension except the particles cannot be filtered out. alginate, shaving cream, mayonnaise are examples
  23. Emulsion
    a type of colloid that is a mixture of 2 liquids that don’t blend together to form one liquid such as oil and vinegar salad dressing. When shaken, a new liquid seemingly results (temporarily)
  24. What is Thermal Conductivity
    —is the rate that heat flows through a material —measured as heat flow over time
  25. Conductors have ____
    a high thermal conductivity
  26. Insulators have _______
    a low thermal conductivity
  27. Galvanic shock can be caused by
    dissimilar metals such as touching a new silver amalgam filling with a fork
  28. The coefficient of thermal expansion is
    a measure of the amount a material will change in volume in relation to changes in temperature
  29. Dissimilar CTEs (coefficient if thermal expansion) can lead to
    —percolation causing microleakage, sensitivity, recurrent decay and fracture
  30. Viscosity of a material is
    • it’s ability to flow.
    • Ex. Water is less vicious than honey
  31. Wetting is the ability
    to wet a surface and bring it into intimate contact with that surface
  32. High contact angle = ______ wetting
  33. Low Contact Angle = ______ wetting
  34. High surface energy will give high ______
  35. _______—is the hardest biologic tissue in the human body.
  36. Hardness is measured by
    —Brinell hardness test, Knoop hardness test, or the Vickers and Rockwell Hardness test
  37. Abrasion resistance
    is the resistance to wear of a material
  38. Porcelain is _____ than enamel
  39. Solubility
    The tendency of a material to dissolve in liquid
  40. Sorption
    tendency of material to absorb a liquid (opposite of solubility)
  41. Munsell System
    a system used to measure color.
  42. Munsell color wheel shows a combination of the following
    • Hue
    • Value
    • Chroma
  43. What is the Hue
    the fundamental color of an object, i.e. what color is it? (outer part of the wheel)
  44. What is the value of a color
    Lightness or darkness of the color from black to white. (left to right on the wheel)
  45. What is the Chroma of a color
    Saturation or strength of a certain color as in pink vs. red(up or down on the wheel)
  46. Transparent
    – no light absorbed, it passes completely through
  47. Translucent
    —part of light passes through, part is absorbed, part goes in and gets scattered. Critical for ideal esthetics for a maxillary incisor
  48. Opaque
    All light is absorbed. Opaque crowns are not esthetic
  49. Metamerism
    Object can appear to be different color in different lights
  50. Radiolucent material
    —Does not absorb radiation very well
  51. Radiopaque material
    —absorbs radiation well
  52. Tensile force
    is a pulling stress
  53. Compressive force
    is a pushing or a crushing stress.
  54. Shear
    also known as “slip” stress, occurs when parts of an object slide by one another
  55. Torsion
    stress is a twisting force like when opening a door knob
  56. Bending
    • a common stress that is actually a combination of different forces
    • when an object is bent, one side is compressed, and the other is under tension
  57. Strain
    the deformation of the material as a result of the forces (stresses) applied to it.
  58. Stress
    a measure of the forces applied to teeth
  59. Plastic
    —when force is applied, the material changes shape, and when force is removed, the material remains in it’s altered form
  60. Young’s Modulus: a.k.a. the modulus of elasticity
    is a measure of an object or substance's resistance to being deformed elastically (i.e., non-permanently) and then ultimately failing (breaking) when a force is applied to it
  61. Yield Point
    also known as the elastic limit or the proportional limit, is the point where any stress beyond this results in a strain that causes plastic (permanent) deformation).
  62. Ultimate Strength
    The point on the graph where any additional stress results in a strain that causes failure (breakage) of the material
  63. Toughness
    Ability to absorb energy up to breaking point
  64. Fatigue
    failure after being stressed repetitively many times (cycles).
  65. Creep
    Changes in shape of a solid due to continuous compressive force
Card Set
Chp 2 Physical and mechanical properties
Chp 2 Physical and mechanical properties