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same atomic composition and structure, same bonding
ex: graphite & diamonds
must be enclosed or thermal energy disperses, very low density and very weak bonding; easy to compress
needs a continer, much denser than gases and hard to compress, medium bonding
self-supporting, dense materials with strong bonding
a dispersion of one phase in another, clusters or clums of atoms or molecules, not much bigger than macromolecules, a lot of surface area
the amount of mass of a material in given volume
Define vapor pressure.
a measure of a liquid's tendency to evaporate and become a gas
the junction of 2 phases, may or may not have the same atomic bonding
Explain the following way to classify a material:
1. type of phase or phases
- gas, liquid, solid
- --weakest to strongest molecular attraction
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
Explain the following ways to classify a material:
3.type of material based on atomic bonding
ceramic, polymer, metal, composite
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
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.
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
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
Describe secondary bonds.
Dipoles, partial charges, weak, in order of increasing strength: fluctuating dipole, permanent, and hydrogem bond
Understand the predominant bonding in metals, ceramics, and polymers.
Ionic; covalent and secondary; metallic
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
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
Relate the following terms to a representative force distance diagram for two oppositely charged ions:
-electronic repulsive force
columbic force= attractive force
electronic repulsive force= repulsive force
equilibrium distance= forces are equal and opposite and balance one another
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
Define mechanical bonding.
interlocking of two objects, as with a nut and bolt
molecular bonding at the atomic level of to dissimilar materials, must get the adhesive in intimate contact with the surface to get molecular bonding
molecular bonding of a material or two like materials
a material that can stick to a flat surface or bond 2 flat surfaces together (bonding material)
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
Define contact angle.
low good wetting; high poor wetting
Define surface energy.
high surface energy of the solid= good wetting
Define type of failure.
failure can also be adhesive (at the interface) or cohesive (in the material)
Describe the effect of the following on "Wetability" of a surface:
surface energy= high- good wetting
surface roughness= rough- poor wetting
surface cleanliness= clean- good wetting
Define melting temperature.
temperature at which melting occurs
Define fusion temperature.
amount of energy needed to melt a material
Define thermal conductivity.
the rate of heat flow through a material
Define thermal diffusivity.
a combination of raising the temp and heat transferred
Define glass transition temperature.
temp where material goes from glassy to rubbery material
Define linear coefficient of thermal expansion.
nearly all things expad when heated
Define heat of fusion.
amount of energy needed to melt a material
Define heat capacity.
measure of the amount of thermal energy that a material can hoard
Define specific heat.
the amount of energy needed to raise the temp of one unit of mass of that material by 1 C
Define fusion range.
mixtures do not have a specific melting temp, but have a range
Define temperature dependence.
change in temp may change energy
Define activation energy.
the amount of energy needed to iniate a reaction
Define reaction rate.
reaction products per time
Define diffusion coefficient.
greatly affected by temp
Define reaction rate constant.
greatly affected by temp
weight or load applied to object
the accompanying change in shape or deformation; change in length
Define elastic strain.
atoms return to their original positions when the stress is removed, no permanent deformation, no change in shape or atomic position
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
Define permanent deformation.
change in shape, bend in a metal coat hanger
Define stress-strain diagram.
tells how stress and strain are related; stress and strain are proportional when there is only one elastic strain
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
Define proportional limit.
same as the yield point
Define elastic limit.
same as the proportional limit * the difference of these is in the testing methods**
Define ultimate strength.
max strength a materical can withstand, the highest point on stress/strain curve, not necessarily the breaking, fracture, or failure point
the plastic strain when fractured in tension
Define Hooke's Law.
Define modulus of elasticity.
the proportionality constant between stress and strain or the slope of the linear portion of the stress strain curve
Define Young's modulus.
same as the modulus of elasticity, the stiffness of material
Define modulus of resilience.
amount of energy absorbed up to the elastic limit
the ability of a material to resist fracture, energy to fracture
the ability of a material to resist fracture, energy to fracture
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
a pushing or crushing or stress
a pulling stress
(slip) stress occurs when parts of an object slide by one another
stress is a twisting force
a common stres and is actually a combination of several types of stress
Define diametrical tension.
a test to determine tensile stress which is directly proportional to the compressive load applied
Define tear strength/impact strength.
resistance to ripping or tearing/ energy absorbed from a sudden single blow
many things do not fail (break) immediately but after a period of time
Define fatigue limit (endurance limit)
the max stress a material can endure without breaking for an infinite lifetime
withstand permanent deformaton under tension
withstand permanent deformation under compression
ability of a material to resist indentation by a point
Define abrasion resistance.
how thick a liquid is, how much is resists flow
study of viscosity.
Define newtonian fluid.
viscosity is not dependent on the flow rate
shear thickening, gets thicker as flow rate increases, slurries
shear thinning, gets thinner as flow rate increases
at constant flow rate, viscosity DECREASES with time
at constant flow rate, viscosity INCREASES with time
flow and elastic together
the small change in shape that results when an object is under continous compression
Define stress relaxation.
decay of stress
Define fracture toughness.
measure of the energy it takes to fracture a material when a crack is present
Define index of refraction.
related to the speed of light in that materal
a psychological response to electromagnetic radiation
Define hue, value, chroma.
general color; vividness/strength, brightness
the energy that a tooth absorbs is converted into light with longer wavelengths, in which case the tooth actually becomes a light source
affects the appearance of an object; can be seen through
also affects the appearance, cannot allow light to pass through
Define Munshell system.
shade matching system of three dimensions
objects that appear to be color matched under one type of light may appear different under another light source
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
Define incident light.
usually a mixture of the various wavelengths; it is selectively absorbed or scattered (or both) at certain wavelengths
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
Define physiologic response.
light is focused on the retina and is converted into nerve impulses that are transmitted to the brain
Define psycological response.
personal perception of color, varis in humans
Define electrical conductivitiy.
metals conduct electricity
Define electrical resistance.
resistance to electrical current
Define water sorption.
some materials absorb water
some materials dissolve in various aqueous fluids
Define shelf life.
things degrade and separate after a period of time
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.
Relate the following to their shelf life of a material:
time: the older a material is, the less effective it will be
temperatue: temp and humidity will also effect the material
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
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.
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).
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.
Know the chemical formula for gypsum, plaster, and stone.
They are all the same euqation they only differ in physical characteristics!
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
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.
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.
Give reason setting expansion occurs.
Setting expansion is due to crystal thrust.
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.
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.
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.
Describe the polymers used in dentistry.
Restorations, cements, denture bases and teeth, ortho appliance retainers, impression material, and others.
one unit, one link
long chains of repeating units usually identical, at least chemically similar, can be brached or crosslinked, mol wt of thousands to millions
2 kinds of units that are joined together that functon as a large monomer
Define chain lengthening.
addition of monomers to make a polymer
Define cross linking.
side groups bond to other chain
polymers that do not melt, flow, and be molded
can withstand a large amount of plastic deformation
glassy polymer, plexiglass, little deformation, brittle, these are usually called the "plastics"
can undergo a large amount of elastic deformation, stretch and return to original shape
Define addition reaction.
free radical polymerization
first step in the induction reaction, usually a chemical, heat or radiation
what activates the initiator
Define free radical.
a compound with an unpaired electron that is used to initiate polymerization
something that prohibits a reaction from occurring or completing
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
Define polymerization shrinkage.
polymeric materials shrink when they react
Define bifunctional monomer.
used during step growth polmerization; type of monument that is used which are all simultaneously activated
one kind of unit, branched or straight
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
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
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
Define branched polymer.
a nonlinear polymer
several units that are joined together that function as a large monomer
Define funtional group
a group on a monomer/polymer that can be used to react with another
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.
Explain the advantageous physical and mechanical properties of polymers.
- -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
Explain the disadvantages of the physical and mechanical properties of polymers present.
- -large coeffficent of thermal expansion
- -not as strong as ceramics or metals
- -poor abrasion resistane
- -high creep and flow
- -some soluable inorganic liquids
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
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.
Define a monomer according to acrylic system.
the monomer determines chain flexability, cahin to chain interaction, and crosslinking
Define plasticizers in the acrylic system.
increases toughness and impact strength
Define pigments in the acrylic system.
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.
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.
Describe at least three uses of dental materials.
preventative materials, restorative/replacement materials, and auxillary materials
Explain chareacteristics of an ideal restorative material.
Nontoxic, biocompatible, esthetic, comparable physical and mechanical properties, usable, bond to tooth structure, stable properties over years
Describe the importance of adhesion to dentin and enamel.
Dental materials need to bond well with dentin and enamel in order to prevent leakage.
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.
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.
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.
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.
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.
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.
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.
Understand the relationship between materials structure, handling, and function.
Processing effects structure at all levels, and thus mixing and handling are important.
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
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
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
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