Dental Materials

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Dental Materials
2012-12-04 17:27:49
Dental Materials Lecture

Dental Materials Lecture 2
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  1. Define phase.
    same atomic composition and structure, same bonding

    ex: graphite & diamonds
  2. Define gas.
    must be enclosed or thermal energy disperses, very low density and very weak bonding; easy to compress
  3. Define liquid.
    needs a continer, much denser than gases and hard to compress, medium bonding
  4. Define solid.
    self-supporting, dense materials with strong bonding
  5. Define colloid.
    a dispersion of one phase in another, clusters or clums of atoms or molecules, not much bigger than macromolecules, a lot of surface area
  6. Define density.
    the amount of mass of a material in given volume
  7. Define vapor pressure.
    a measure of a liquid's tendency to evaporate and become a gas
  8. Define interface.
    the junction of 2 phases, may or may not have the same atomic bonding
  9. Explain the following way to classify a material:

    1. type of phase or phases
    • gas, liquid, solid
    • --weakest to strongest molecular attraction
  10. Explain the following way to classify :

    2. atomic order
    crystalline or amorphous

    crystalline- long range order, crystal systems, lattice structure

    amorphous- short range order but no long range order, order much like that of liquid, these materials are sometimes thoight of as supercooled liquids or very disorganized crystals
  11. Explain the following ways to classify a material:

    3.type of material based on atomic bonding
    ceramic, polymer, metal, composite
  12. Explain the following ways to classify a material:

    4. ceramic, polymer, metal, or composite
    ionic; covalent and secondary bonds, metallic bonds; 2 or the above phases
  13. Explain the role of the electromagnetic force in atomic bonding.
    EM force causes positive charges to attract negative charges and negative charges to attract positive charges.
  14. Describe the distribution of valence electrons for the ionic, covalent, and metallic bonds.
    ionic: electrons are given up and received

    covalent: electrons are shared between atoms

    metallic: electrons are shared between atoms
  15. Describe the relative strength and "directionality" of ionic, covalent, and metallic bonds.
    ionic: strong and directional bonds between charged atoms

    covalent: strong and undirectional

    metallic: less strong and nondirectional, but add
  16. Describe secondary bonds.
    Dipoles, partial charges, weak, in order of increasing strength: fluctuating dipole, permanent, and hydrogem bond
  17. Understand the predominant  bonding in metals, ceramics, and polymers.
    Ionic; covalent and secondary; metallic
  18. Explain how optical, thermal, and electrical properties of metals, ceramics,  and polymers are related to the bonding involved.
    • 1. ceramic: ionic-translucent insulators
    • 2. polymer: covalent and 2nd translucent- insulators
    • 3. metal: metallic very opagque-conductors
  19. Relate the mechanical properties of metals, polymers, and ceramics to the type of bonding involved and the effect of atomic slip.
    • 1. ceramic: very strong and brittle
    • 2. polymer:  weak and stetch (some strong)
    • 3. metal: strong and tough
  20. Relate the following terms to a representative force distance diagram for two oppositely charged ions:

    -columbic force
    -electronic repulsive force
    -equilibrium distance
    columbic force= attractive force

    electronic repulsive force= repulsive force

    equilibrium distance= forces are equal and opposite and balance one another
  21. Relate the following properties to a REPRESENTATIVE ENERGY DISTANCE diagram for the same two oppositely charged ions:

    3. melting point and boiling point
    4. thermal expansion
    1. stregth= depth

    2. elasticity= slope

    3. melting point and boiling point= depth

    4. thermal expansion= asymmetry of slope
  22. Define mechanical bonding.
    interlocking of two objects, as with a nut and bolt
  23. Define adhesion.
    molecular bonding at the atomic level of to dissimilar materials, must get the adhesive in intimate contact with the surface to get molecular bonding
  24. Define cohesion.
    molecular bonding of a material or two like materials
  25. Define adhesive.
    a material that can stick to a flat surface or bond 2 flat surfaces together (bonding material)
  26. Define adherent.
    the surface
  27. Define interface.
    tooth/restoration junction
  28. Define wetting.
    a surface with an adhesive material, such as a sealant, brings the material into intimate association with the surface so that chemical and micromechanical bonding can occur
  29. Define contact angle.
    low good wetting; high poor wetting
  30. Define surface energy.
    high surface energy of the solid= good wetting
  31. Define type of failure.
    failure can also be adhesive (at the interface) or cohesive (in the material)
  32. Describe the effect of the following on "Wetability" of a surface:

    surface energy=
    surface roughness=
    surface cleanliness=
    surface energy= high- good wetting

    surface roughness= rough- poor wetting

    surface cleanliness= clean- good wetting
  33. Define melting temperature.
    temperature at which melting occurs
  34. Define fusion temperature.
    amount of energy needed to melt a material
  35. Define thermal conductivity.
    the rate of heat flow through a material
  36. Define thermal diffusivity.
    a combination of raising the temp and heat transferred
  37. Define glass transition temperature.
    temp where material goes from glassy to rubbery material
  38. Define linear coefficient of thermal expansion.
    nearly all things expad when heated
  39. Define heat of fusion.
    amount of energy needed to melt a material
  40. Define heat capacity.
    measure of the amount of thermal energy that a material can hoard
  41. Define specific heat.
    the amount of energy needed to raise the temp of one unit of mass of that material by 1 C
  42. Define fusion range.
    mixtures do not have a specific melting temp, but have a range
  43. Define temperature dependence.
    change in temp may change energy
  44. Define activation energy.
    the amount of energy needed to iniate a reaction
  45. Define flux.
  46. Define reaction rate.
    reaction products per time
  47. Define diffusion coefficient.
    greatly affected by temp
  48. Define reaction rate constant.
    greatly affected by temp
  49. Define load.
    a force
  50. Define force.
    weight or load applied to object
  51. Define strain.
    the accompanying change in shape or deformation; change in length
  52. Define elastic strain.
    atoms return to their original positions when the stress is removed, no permanent deformation, no change in shape or atomic position
  53. Define plastic strain.
    atoms don not return to their original positions but recover only the elastic part of the strain when the stress is removed, change in shape, permanent deformation
  54. Define permanent deformation.
    change in shape, bend in a metal coat hanger
  55. Define stress-strain diagram.
    tells how stress and strain are related; stress and strain are proportional when there is only one elastic strain
  56. Define yield point.
    when the stress exceeds the limit of only elastic strain, then plastic strain begins, the stress/strain plot is no longer linear
  57. Define proportional limit.
    same as the yield point
  58. Define elastic limit.
    same as the proportional limit * the difference of these is in the testing methods**
  59. Define ultimate strength.
    max strength a materical can withstand, the highest point on stress/strain curve, not necessarily the breaking, fracture, or failure point 
  60. Define elongation.
    the plastic strain when fractured in tension
  61. Define Hooke's Law.
  62. Define modulus of elasticity.
    the proportionality constant between stress and strain or the slope of the linear portion of the stress strain curve
  63. Define Young's modulus.
    same as the modulus of elasticity, the stiffness of material
  64. Define modulus of resilience.
    amount of energy absorbed up to the elastic limit
  65. Define toughness.
    the ability of a material to resist fracture, energy to fracture
  66. Define toughness.
    the ability of a material to resist fracture, energy to fracture
  67. Define Poisson's ratio.
    describes a mechanical property that is defined as the ratio of the strain in the direction of the stress to the strain in a direction perpendicular to the stress
  68. Define compression.
    a pushing or crushing or stress
  69. Define tension.
    a pulling stress
  70. Define shear.
    (slip) stress occurs when parts of an object slide by one another
  71. Define torsion.
    stress is a twisting force
  72. Define flexure.
    a common stres and is actually a combination of several types of stress
  73. Define diametrical tension.
    a test to determine tensile stress which is directly proportional to the compressive load applied
  74. Define tear strength/impact strength.
    resistance to ripping or tearing/ energy absorbed from a sudden single blow
  75. Define fatigue.
    many things do not fail (break) immediately but after a period of time
  76. Define fatigue limit (endurance limit)
    the max stress a material can endure without breaking for an infinite lifetime
  77. Define ductile.
    withstand permanent deformaton under tension
  78. Define malleable.
    withstand permanent deformation under compression
  79. Define hardness.
    ability of a material to resist indentation by a point
  80. Define abrasion resistance.
    wear resistance
  81. Define viscosity.
    how thick a liquid is, how much is resists flow
  82. Define rheology.
    study of viscosity.
  83. Define newtonian fluid.
    viscosity is not dependent on the flow rate
  84. Define dilatant.
    shear thickening, gets thicker as flow rate increases, slurries
  85. Define pseudoplastic.
    shear thinning, gets thinner as flow rate increases
  86. Define thixotropic.
    at constant flow rate, viscosity DECREASES with time
  87. Define rheopectic.
    at constant flow rate, viscosity INCREASES with time
  88. Define viscoelasticity.
    flow and elastic together
  89. Define creep.
    the small change in shape that results when an object is under continous compression
  90. Define stress relaxation.
    decay of stress
  91. Define fracture toughness.
    measure of the energy it takes to fracture a material when a crack is present
  92. Define index of refraction.
    related to the speed of light in that materal
  93. Define color
    a psychological response to electromagnetic radiation
  94. Define hue, value, chroma.
    general color; vividness/strength, brightness
  95. Define fluorescence.
    the energy that a tooth absorbs is converted into light with longer wavelengths, in which case the tooth actually becomes a light source
  96. Define transparency.
    affects the appearance of an object; can be seen through
  97. Define opacity.
    also affects the appearance, cannot allow light to pass through
  98. Define Munshell system.
    shade matching system of three dimensions
  99. Define metamerism.
    objects that appear to be color matched under one type of light may appear different under another light source
  100. Define L*a*b* color system.
    color is measured with a spectrophometer, and the data is mathematically manipulated to get 3 numbers on the 3 axes of a "more homogenous" color space
  101. Define incident light.
    usually a mixture of the various wavelengths; it is selectively absorbed or scattered (or both) at certain wavelengths
  102. Define reflection of light.
    reflection of light from an object onto the eye; the eye is most senstivie to light in the green-yellow region and least in the red or blue regions
  103. Define physiologic response.
    light is focused on the retina and is converted into nerve impulses that are transmitted to the brain
  104. Define psycological response.
    personal perception of color, varis in humans
  105. Define electrical conductivitiy.
    metals conduct electricity
  106. Define electrical resistance.
    resistance to electrical current
  107. Define water sorption.
    some materials absorb water
  108. Define solubility.
    some materials dissolve in various aqueous fluids
  109. Define disintegration.
  110. Define shelf life.
    things degrade and separate after a period of time
  111. Compare and contrast mixing, working, and setting times.
    Mixing time is the amount of time you have to mix something, working time is the time between the addition of powder to liquid and the loss of gloss, and the setting time is the time it takes to completely set. 
  112. Relate the following to their shelf life of a material:

    1. time
    time: the older a material is, the less effective it will be

    temperatue: temp and humidity will also effect the material
  113. Describe the effect of electron denisty on x-ray absorption.
    Electons absorb and scatter; some materials are radiolucent and are not seen on radiographs, other materials are radiopaque and are evident on radiographs
  114. Describe the gypsum products, their use in dentistry and their water/poweder ratios.
    Gypsum was originally used for building products. It is mined in various parts of the country, or is a byproduct. It is used as positive casts or models and dies. There are different water to powder ratios depending on the results you are wanting. Mainly, the powder is mixed with water to form a slurry.
  115. Describe the chemical reaction involved in the production of gypsum products and their setting reaction.
    The reaction is a reversal of calcination. Mix to form a slurry or suspension to saturated to supersat to dehydrate precipitates out to heat liberated (exothermic).
  116. Describe the production of plaster and dental stones from gypsum.
    1. Plaster is manufactores in an open kettle, gypsum ground and heated to 110- 120 C.

    2. Stone is manufactrued in an autoclave.

    3. Improved stone is manufactured by boiling CaCl solution.
  117. Know the chemical formula for gypsum, plaster, and stone.
    They are all the same euqation they only differ in physical characteristics!
  118. Describe the differences in particle shape, size, roughness, and porosity between plaster and stone.
    • 1. plaster: white, irregular crystals, porous spongy particles
    • 2. stone: buff colored, regular, prismatic and non-porous particles, clevage fragments and crystals
    • 3. Improved stone: non porous large particles, cuboidal, smooth, lower surface area
  119. Describe the effect of water/powder ratio, mixing variables, temperature, drying, retarders, and accelerators on the strength, setting time, and setting expansion of gypsum products.
    The water/powder ratio affects the setting time, thicker sets faster, thinner is weaker, and thick results in more expansion. A higher temperature usually causes it to set faster. Longer mixing results in a faster set frim more nucleui, more expansion. Accelerators decrease the setting time, while reatders including setting time, both reduce expansion.
  120. Describe the role precipitation, nucleation, and growth have in the setting reaction of gypsu, products and the processes in #6.
    Precipitation occurs from nuclei of precipitation. When the number of nuclei or the rate of their formation increases, it results in a faster set.
  121. Give reason setting expansion occurs.
    Setting expansion is due to crystal thrust.
  122. Know theorectical water/powder ratio; reasons for and effects of the excess water used.
    The theoretical water/powder ratio is 18-19cc. Some produts need more water, but are weaker.
  123. Describe and explain the effects of colloids K2SO4 and borax on the setting of gypsum products.
    Colloidal systems reduce setting at surface. K2So4 accelerates the set rate, and borax retards setting.
  124. Describe hygroscopic expansion.
    Twice the normal expansion, add extra water before initial set; physical not chemical. Replace water used in hydration, get rid of contraction due to surface tension and get more effective and addititonal crystal thrust and crystal growth. 
  125. Describe the polymers used in dentistry.
    Restorations, cements, denture bases and teeth, ortho appliance retainers, impression material, and others.
  126. Define mer.
    one unit, one link
  127. Define dimer
    two units
  128. Define trimer
    three units
  129. Define polymer.
    long chains of repeating units usually identical, at least chemically similar, can be brached or crosslinked, mol wt of thousands to millions
  130. Define copolymer.
    2 kinds of units that are joined together that functon as a large monomer
  131. Define chain lengthening.
    addition of monomers to make a polymer
  132. Define cross linking.
    side groups bond to other chain
  133. Define thermoset.
    polymers that do not melt, flow, and be molded
  134. Define plastic.
    can withstand a large amount of plastic deformation
  135. Define resin.
    glassy polymer, plexiglass, little deformation, brittle, these are usually called the "plastics"
  136. Define rubber.
    can undergo a large amount of elastic deformation, stretch and return to original shape
  137. Define addition reaction.
    free radical polymerization
  138. Define initiator.
    first step in the induction reaction, usually a chemical, heat or radiation
  139. Define activator.
    what activates the initiator
  140. Define free radical.
    a compound with an unpaired electron that is used to initiate polymerization
  141. Define inhibitor.
    something that prohibits a reaction from occurring or completing
  142. Define condensation reaction.
    the reactions that produce step growth polymerization can progress by any of the chemical reaction mechanisms that join two or more molecules in producing a simple, macromolecular strucutre; get a biproduct
  143. Define polymerization shrinkage.
    polymeric materials shrink when they react
  144. Define bifunctional monomer.
    used during step growth polmerization; type of monument that is used which are all simultaneously activated
  145. Define homopolymer.
    one kind of unit, branched or straight
  146. Define random copolymer.
    polymer made up of two or more monomer species but with no sequential order between the mer units along the polymer chain
  147. Define block copolymer.
    a polymer made of two or more monomer species and identical monomer units occurring in relatively long sequences along the main polymer chain
  148. Define grafted copolymer.
    a polymer in which sequences of one type of mer unit are attached as a graft (branched) onto the backbone of a second type of mer unit
  149. Define branched polymer.
    a nonlinear polymer
  150. Define oligometer
    several units that are joined together that function as a large monomer
  151. Define funtional group
    a group on a monomer/polymer that can be used to react with another
  152. Explain three means of activating addition polymerization reaction used in dentistry.
    The three means of activating addition polymerization are by chemicals, heat, or radiation (light). Chemical uses tertiary amine and BPO, and light activated systems use several chemicals and photons.
  153. Explain the advantageous physical and mechanical properties of polymers.
    • advantages:
    • -chemically stable in water, acids, and solvents
    • -color stability
    • -some can exhibit large amounts of elastic deformation
    • -some can absorb large amounts of energy
    • -insouluable in water
  154. Explain the disadvantages of the physical and mechanical properties of polymers present.
    • disadvantages: 
    • -shrinkage
    • -large coeffficent of thermal expansion
    • -not as strong as ceramics or metals
    • -poor abrasion resistane
    • -high creep and flow
    • -some soluable inorganic liquids
  155. Describe the dependance on size of side groups in relation to polymers.
    size of side groups: larger side groups decrease slippage; can also result in less strength and a softer material because the chains are further apart
  156. Describe resins and elastomers and their use in dentistry.
    Resins are glossy polymer tht have little deformation and elastomers can undergo a large amoint of elastic deformation. Dental resins are used for denture bases, denture teeth, temporary crowns, and other things. Filled resins or composites are used for restorations and many other uses.
  157. Define a monomer according to acrylic system.
    the monomer determines chain flexability, cahin to chain interaction, and crosslinking
  158. Define plasticizers in the acrylic system.
    increases toughness and impact strength
  159. Define pigments in the acrylic system.
    adds color
  160. Describe the setting reactions of heat cure and chemical cure acrylic resin
    If it is  a heat cure system: the reaction starts when the mix is heated, so it will have time to work with the mix before it is heated and the reaction starts.

    If it is a cold cure or chemically activated system, the reaction starts when the activators and iniatior react and produce free radicals. The first free radicals react with the inhibitor, destroying them, providing working time, after the inhibitor is used up then polymerization beigins forming chains.
  161. Describe the repair of acrylic material.
    Residual Carbon carbon double bonds can react with new material. As the monomer easily evaporates, residual carbon carbon double bonds are only present for a short time,

    New material can be physically bonded to old materials by dissolving the set polymer in new polymer in new monomer, similar to the usual mixing monomer and polymer.
  162. Describe at least three uses of dental materials.
    preventative materials, restorative/replacement materials, and auxillary materials
  163. Explain chareacteristics of an ideal restorative material.
    Nontoxic, biocompatible, esthetic, comparable physical and mechanical properties, usable, bond to tooth structure, stable properties over years
  164. Describe the importance of adhesion to dentin and enamel.
    Dental materials need to bond well with dentin and enamel in order to prevent leakage.
  165. Understand the reasons for use of the oldest od dental materials, gold, and ZnO.
    • Gold was and is used for crowns, bridges, and partial dentures,
    • Gold is strong and wear resilient so is therefore characteristic of IRM. 
    • ZnO evolved as fillings and cements to "glue" the restoration of the tooth.
  166. Know the development of the more modern materials: amalgam, cast gold, acrylics, and composites.
    • Amalgam was widely accepted and frequently used in the 1800s.
    • -Cast metals were used in the 20th century for crowns, bridges, and partial dentures. 
    • -Acrylic resins started being used in 1940. 
    • -Composites began being used in the 1960s, and are alternatives for many dental materials.
  167. Know the relation of the ADA and NIST.
    In 1919, a detnal research program at the National Bureau of Standards was organized, called NIST. In 1928, the ADA sponsored a Dental Research Fellowship at NIST, and a great deal of coroporation exists today.
  168. Differentiate between ADA Specification, Guideline, Acceptance, and Seal.
    • -ADA Specifications are material standards, they are generally laboratory tests of physical properties. If a product passes the tests in the ADA/ANSI specifications, it is given ADA acceptance. The manufactorer may then use the ADA Seal on packaaging and in advertising, but the advertising must be approved by the ADA. 
    • -Also, for many products and materials, there are no ADA specs. If a products is shown to be safe and effective by meeting Acceptance Guidelines, certain laboratory tests or clinical trials, it is given ADA Acceptable and may use the Seal.
  169. Know the role of ANSI, FDI, and ISO in determining specifications.
    The American National Standards Institute, ANSI, works with the Council on Scientific Affairs, which determin the needed tests to form and review ADA/ANSI Specifications.

    -ISO standards for many dental materials have been developed and continue to be developed under the guidance of the Federation Dentaire Internationale.
  170. Know the role of FDA in regulating dental material and devices.
    In 1976, the Medical Devices Amendments were passed. This legislation got the FDA involved. Dental materials and other products are subject to control by the FDA Center for Devices and Radiological Health. All dental materials are classified as devices.
  171. Explain the regulatory classification of devices used by the FDA.
    class I = products are low risk items and have only general good manufactoring regulations

    class II= products have more regulation including federal performance standards or others (such as ADA Acceptance)

    • class III= products have the most regulation including premarket approval.
    • Manufacturers must provide data demonstrating safety and efficiany before marketing.
  172. Understand the relationship between materials structure, handling, and function.
    Processing effects structure at all levels, and thus mixing and handling are important.
  173. Understand the effects of the oral environment on materials including: forces placed on materials, temperature changes, and chemical attack.
    a. biting forces= average biting forces of a person with teeth is 170 lbs

    b. temperature changes= things expand when heated, cracking can occur when things are rapidly heated or cooled

    c. acidity= adds discolor and corrode metals, mouth is warm place for bacteria to produce acis and other metabolites, acids and salt promote corrosion
  174. Understand the effects of materials on the biological tissues:

    microleakage= the leakage of fluids, bacteria, and other debris can irriate the pilp and lead to recurrent decay

    galvanism= a mini battery can be set up if 2 different metals are present in the mouth, get a small current

    toxicitiy= can be harmful to the pulp and other oral tissues as well as the dental personnell

    stability= properties need to be stable over a lifetime
  175. Classify dental materials in terms of useful lif, use with direct or indirect techniques, and function.
    permanent or temporarily permanent= 10-20 years of more not planning to replace

    temporary or provisional= days to a few weeks or a month, planning to replace

    interim= long term temporary, several months to years, planning to replace after a particular time period or treatment

    direct restorative materials= placed and molded in the mouth

    indirect materials and techniques= constructed outside of the mouth, need auxillary materials such as impression and model (cast) and cement materials

    functions= restorative material, luting agent, impression material, model/cast material and auxillary materials; intermediate base and insulator or lining protective material used to protect the pulp from thermal, chemical , and electrical insult