Properties of Dental Materials

  1. Four major properties of dental materials
    • chemical
    • physical
    • mechanical
    • optical
  2. forces of metal (ferrous and non ferrous)
    "electron sea" that glues the ions together
  3. uses of metals (ferrous and non ferrous)
    usually strong, conduct electricity and heat well and are opaque to light
  4. forces of ceramics
    positive or negative ions, coulomb forces
  5. composition of ceramics
    combinations of metals or semiconductors with oxygen, nitrogen, or carbon

    examples: glass, porcelain, minerals, diamonds
  6. forces of polymers
    covalent, van der waals, H-C bonds
  7. Weight of polymers

    examples of polymers (4)
    light weight

    plastics, rubber, polyester, elastomers
  8. the mixture of a metal, ceramic and polymer is a
    composite
  9. Stress equation

    Example: 

      According to the Centers for Disease Control, the average weight of an American man and woman in 2010 was 195.5 and 166.2 pounds, respectively. Imagine a typical American man wearing shoes with a heel area of 10 square inches and a woman wearing high heels with an area of .25 square inches (1/4 inch per side). When walking, a man’s foot exerts a force of 19.5 pounds per square inch on the surface he is walking on while a woman’s heel would exert a force of 2,659 pounds per square inch.
    Stress= Force/ Area

    Stress = Force / Area  195.5/10  =  19 

      166.2/.0625  =  2659
  10. Image Upload 1
    A and B?
    P
    • A= compression
    • B= tension 

    P= pressure or force?
  11. the measure of heat transfer or heat flow
    thermal conductivity
  12. True/False: metals have lower values of conducting heat than plastics and ceramics
    FALSE; they have higher values
  13. Enamel and dentin are ___ conductors of heat and cold
    poor
  14. ____ ____ and their components have the largest coefficient of thermal expansion of any material used in restorative dentistry
    dental waxes
  15. the generation of electrical currents that the patient can feel
    Galavinism
  16. a surface reaction of metals in the mouth from components in saliva or food
    tarnish
  17. the dissolution of metals in the mouth
    corrosion
  18. True/False: computerized systems are the best way to color match for restorative dentistry
    FALSE; they offer great hope for the future but visual shade selection with the human eye is still the most predictable method available
  19. the visible spectrum ranges from ___ to ___ nm
    400 to 700
  20. what are the 4 wavelengths shorter than the visible light
    ultraviolet, x-rays, gamma, and cosmic rays
  21. what the 5 waves above the visible spectrum
    • infrared
    • microwaves
    • television
    • radio
    • electrical waves
  22. degree of saturation of a shade; light yellow to dark yellow
    chroma
  23. sensation induced from light of varying wavelengths reaching the eye
    color
  24. the property of light source to influence color of objects
    color rendition
  25. dominant color of an object; dominant color: red, yellow, green, blue, etc
    Hue
  26. phenomenon in which the color of an object under one type of light appears to change when illumination by different light source
    metamerism
  27. relative lightness or darkness of a color; white to dark
    value
  28. Guidelines for evidence based shade selection

    Proper:
    lighting:
    distance: 
    time:
    environment:
    preoperative:
    • lighting: 5550* K
    • distance: 6-8 inches
    • time: 3-5 seconds
    • environment: neutral environment 
    • preoperative: dehydrated teeth are lighter
  29. increasing translucency decreases____
    value

    amount, location, and quality varies w person and age
  30. determines the amount and direction of light reflected off the facial surface; wears with age; develop texture from adjacent natural teeth
    surface texture
  31. the property of materials that prevents the passage of light
    opacity
  32. A property that allows the passage of light so little distortion takes place and objects may be seen clearly through them.
    transparency
  33. Is a property of substances that permits passage of light but disperses the light so objects cannot be seen through the materials
    translucency
  34. The same object, without changing color may appear different in color under different lighting conditions
    metamerism
  35. strain equation
    strain= deformation (change in length)/ original length
  36. the ratio of stress to strain in the linear or elastic portion of the stress-strain curve
    elastic modulus
  37. the stiffness of a material and is a constant
    elastic moduli of dental materials
  38. elastic moduli of:

    human enamel:
    gold alloy:
    • 83,000
    • 96,600
  39. the stress at which the material no longer functions as an elastic solid and is higher than the elastic modulus
    proportional limit
  40. used to designate a certain permanent deformation or offset, usually 0.2% (slightly higher than proportional limit)

    used because proportional limit is difficult to determine
    yield strength
  41. indicates that stress and strain are no longer proportional
    plastic deformation 

    higher than plastic deformation on graph
  42. the strength at which fracture occurs
    ultimate strength
  43. higher forces applied to a material will cause fracture or rupture
    ultimate tensile strength
  44. indicates the energy absorbed up to the proportional limit
    resilience
  45. indicates the energy absorbed up to the ultimate tensile strength
    toughness
  46. on graph under the elastic modulus until proportional limit
    resillence
  47. on graph between proportional limit to ultimate tensile strength along plastic deformation curve
    toughness
  48. the resistance of a material to indentation
    hardness
  49. knoop hardness scale goes from what to what?

    hardest material
    softest material
    0-600 

    • softest: acrylic resin
    • hardest: dental porcelain
  50. a measure of the consistency of a fluid and its inability to flow. it is a function of time that can be used to measure the working time of a material that undergoes a liquid-to-solid transformation
    viscosity
  51. the percentage of shrinkages or expansion of a material
    dimensional change
Author
arikell
ID
338415
Card Set
Properties of Dental Materials
Description
Midterm Material 2/7
Updated