atoms, molecules, bonding properties
explains why materials behave the way they do based on ..., ... and ...
microscopic
looking at the material through the arrangement of its atoms and their bonding schemes
macroscopic
looking at a material as a solid, liquid or gas that either has its own shape, or takes on shape of its container
covelent, ionic, metallic
3 types of primary bonds
primary bonds
provide the force that holds solids together, strength and stability
covalent bond
strong and stable, results from the sharing of electrons between 2 atoms, forms a stable molecule
denture polymer, composite resins
2 examples of covalent bonds
ionic bond
interaction of a + and - charge, one atoms donates its electron to another for linkage, not used often in dentistry since it is unstable in water
polycarboxylate dental cemen, gypsum stone
2 examples of ionic bonds
metallic bond
many atoms sharing all their outer electrons, very strong and stable, electrons free to move around (ability to conduct heat and electricity), strength increases as the number of outermost electrons increase
secondary bonds
atoms that do not share electrons, weaker attraction, important for adhesion between a liquid and a solid that are not chemically attracted
polymer
chemical compound consisting of a large molecules formed by many smaller repeating molecules
polymers
secondary bonds are important in determining the properties of ...
physical, mechanical
structure of a material is important because it determines ... and ... characteristics
metals, ceramics, polymers, composites
4 materials used in dentistry
metals
high thermal and electrical conductivity, ductility, luster, dissolved to some extend in h2o producing positively charged atoms
ductility of metal
bends without breaking, easily molded
luster of metal
strongly reflects light and appears bright and shiny
metals
solidify in a crystalline arrangement often in a cube form
melting temperatures
the high strength metallic bond that holds the atoms together cause metals to have a high ...
amalgam
combination of one metal (mercury) that is liquid at room temperature, very hard restoration
ceramics
compounds formed by union of metallic and non metallic elements
glass fillers, porcelain
2 examples of ceramics used in dentistry
high, low, insulators
ceramics have a ... melting points and ... thermal and electrical conductivity, and are good ...
translucent
some light passes through like natural teeth (ceramic)
oxide powders
ceramics are manufactured by fusing ... together in ovens at high temperatures enabling them to produce wide range colors
polymers
man made material, long chain organic molecules, made up of carbon atoms linked together
poor, primary, secondary
polymers are ... conductors of heat and electricity and are made up of .. and .. bonds
polymers
limited structural stability, minimal stability and strength, used as a temp restoration or sealants
glass particles
when polymers are mixed with ... they as used as anterior or posterior esthetic restorations
composites
materials made of two or more different materials, mixture of polymer and ceramic, strong and lightweight
physical, mechanical, biologic, chemicals
properties of materials divided into these 4 categories
density
amount of mass in a given volume, depends of type of atoms present, atomic number increases equals a more dense material
vapor pressure
measure of liquids tendency to evaporate
vapor pressure increase
temperature increase = ...
solvents
materials with high vapor pressure used as ...
thermal conductivity
the rate at which heat flows through a material
heat capacity
the amount of heat required to raise the temperature of material
faster
if the amalgam is deep, the temperature below the amalgam will reach an unacceptable level ... than if the amalgam is shallow
dentin
..., which has a higher heat capacity will absorb the heat instead of transmitting it to the pulp
coefficient of thermal expansion
measure of change of volume at a material in relation to a change in temperature of the material, contraction or expansion
solubility
ability of a substance to dissolve in another substance
sorption
uptake of fluids by a material
viscosity
the measure of a liquids resistance to forces that tend to cause it to flow
hardness
ability of a material to resist forces of indentation
enamel
hardest biologic tissue in the human body
hue
the dominant color of the object
value
refers to the lightness of a color on a scale of 1 to 10, teeth generally 6-8
chroma
intensity of the color on a scale of one to ten, teeth generally 1-3
elasticity, strain, stress
3 types of mechanical properties
elasticity
force and change in shape, the ability of an object to be deformed and then return to its original shape
elastic strain
amount of deformation that is recovered instantly when an outside force is removed
stress
force of load placed on an object that strains or deforms an object
strain
change in dimension of an object measured through compression or elongation
moldulus of elasticity
the stiffness of a material that is calculated by the ratio of stress to strain, formula = stress/ strain
proportional limit
yield point or elastic limit - point where the line starts to curve on the stress strain model
plastic deformation
point where material does not return to original shape after removal of load
ultimate strength
the highest stress point measures
stiffer
higher the MOE, the ... the material
compression
pushing or crushing
tension or tensile
pulling stress
shear
stress the occurs when parts of an object slide by one another
torsion
twisting force
bending
combination of compression and stretching
ductility
ability of material to elongate under stress
fatigue
repeated application of stress to an object causing tiny crack within its structure which eventually lead to larger crack
creep
gradual but permanent change in dimension due to a constant load
adhesion
force of attraction between the molecules or atoms on two different surfaces as they are brought into contact
cohesion
the force of attraction between the molecules or atoms within a given material
wetting
the ability of a liquid to maintain contact with a solid surface
contact angle
the angle made between the adhesive and the surface can be measures to give it a value for wetting
no wetting, complete wetting
180 degrees = ...
0 degrees = ...