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dental material 1 > dental 2 > Flashcards

dental 2 Flashcards

1
Q

3 physical properties of dental material

A

mechanical
electrical
thermal

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2
Q

what are the different mechanical properties?

A

strength
hardness
elasticity
plasticity

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3
Q

what are the different mechanical strengths

A

tensile
compressive
shear

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4
Q

what are the test for hardness

A 
brinell
vicker
knoop
rockwell
share A
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5
Q

what does mechanical elasticity test

A

elastic modules

resiliance

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6
Q

what does mechanical placticity test for

A

ductility
percent elongation
yield strenth

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7
Q

what do the electrical and electrochemical physical properties mesure

A

electrode potential

electrical resistivity

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8
Q

what do thermal propoties mesure

A 
thermal expansion 
heat flow ( thermal conductivity and diffusivity )
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9
Q

atom

A

smallest electroneutral part of chemical element which preserves its chemical properties

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10
Q

mass number

atomic number

A

mass- neutrons

atomic- electrons

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11
Q

simple substance

A

atoms of 1 in the same chemical element

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12
Q

what are the different states of material

A

gas
liquid
solid( crystalline and amorphous )

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13
Q

7 different crystal lattice

A

cubic, rhombic, monoclinic, hexagonal, tetragonal, triclinic and rhombohedral

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14
Q

what is allotropy

A

ability to change crystal lattice depending on the temp e.g carbon- graphine and dimond

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15
Q

what is amorphous

A

random molecular formation as fluids with high dentisty and vicocity
thermodynaically unstable
when heated it softens lowering the viscosity

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16
Q

e.g of am amorphoges and lattice

A

wax- 52 degrees amorphous material,

36 degrees -crystal

17
Q

what is the force that holds atoms together

A

cohesive forces

18
Q

what is cohesion

A

force/ molecular attreaction between molecules or atoms of the same substance

19
Q

classification of interatomic bonds

A

primary and secondary

20
Q

primary interatomic bonds

A

ionic
covalent
metalic

21
Q

secondary interatomic bonds

A

hydrogen

van der waals forces

22
Q

what is an ionic bond

A

the mutal attraction between and positive and negativly charged element

23
Q

e.g of ionic bonding

A

sodium chloride (na+ cl-)
Na contains one valence e- in the outer shell
and chlorine has seven electrons in the outer shell .
transfer of Na valence e- to cl results in a dtable compound

24
Q

where can you find ioinc bonding in dentistry

A

some gypsum and phosphate based cement in their crystalline phases

25
Q

what is a covalent bond

A

are the results of electron sharing between 2 valence electrons by adgacent atoms.

26
Q

e.g of covalent bonding

A 
hydrogen molecule (H2)
single valence elctron  is shared with the other combining atom, causeing the valence shells to become stable
27
Q

what are metallic bonds

A

characterized by electron sharing and formation of a “gas” or “cloud” of electrons that bonds the atoms (which become positively charged because of the electron gas formation) together in the lattice

28
Q

what are interatomic secondary bonds

A

dont share electrons, instead the charge variation among molecules induce polar forces that attract the molecule

29
Q

water in hydrogen bonding

A

2 hydrogen atoms bonded to 1 oxgen therfore
the p+ of the hydrogens pointing away from the O arnt shilded by the electrons making the poton side positivly charged
on the opposite side the elctrons that fill the outer orbit of oxygen provide a negative charge. a permanent dipole exits represnting asymmetric molecule

30
Q

what happens when multiple H2O molcules mix

A

positive hydrogen is attrected to the negative oxygen part of its neighboring molecule producing hydrogen bridges

31
Q

what are Van der Waals forces

A

form the basis of all dipole attractions
in symmetric molecules e.g inert gas, the electron feild constantly fluctuates so that it becomes momentarily positive or negative. the fluctuating dipole attracts similar dipoles.

32
Q

what is water sorption of a material

A

represent the amount of water aDsorbed on the surface and aBsorbed into the body of the material during fabrication.

33
Q

e.g of water sorption

A

of denture arcylic- is mesured gravemetrically in μg/mm3 after 7 days in H2O

34
Q

What is crystalline

A

having molecules arranged in a regular 3 dimensional pattern

e.g metal

35
Q

charecteristics of crystalline

A 
microscopic range order 
periodic crystal structure
have definite shape and volume
small no of defects in the structure 
sharp and well-defined melting points
36
Q

what is amorphous

A

Atoms in crystalline solids exhibit an ordered

arrangement, whereas atoms in amorphous solids lack this long-range periodicity.

37
Q

charecteristics of amorphous

A

lots of structre defects
no set shape
mechanical hardness
isotrope property

dental material 1 (11 decks)

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