dental 2

Question 1

3 physical properties of dental material

Answer 1

mechanical
electrical
thermal

Question 2

what are the different mechanical properties?

Answer 2

strength
hardness
elasticity
plasticity

Question 3

what are the different mechanical strengths

Answer 3

tensile
compressive
shear

Question 4

what are the test for hardness

Answer 4

brinell
vicker
knoop
rockwell
share A

Question 5

what does mechanical elasticity test

Answer 5

elastic modules

resiliance

Question 6

what does mechanical placticity test for

Answer 6

ductility
percent elongation
yield strenth

Question 7

what do the electrical and electrochemical physical properties mesure

Answer 7

electrode potential

electrical resistivity

Question 8

what do thermal propoties mesure

Answer 8

thermal expansion 
heat flow ( thermal conductivity and diffusivity )

Question 9

atom

Answer 9

smallest electroneutral part of chemical element which preserves its chemical properties

Question 10

mass number

atomic number

Answer 10

mass- neutrons

atomic- electrons

Question 11

simple substance

Answer 11

atoms of 1 in the same chemical element

Question 12

what are the different states of material

Answer 12

gas
liquid
solid( crystalline and amorphous )

Question 13

7 different crystal lattice

Answer 13

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

Question 14

what is allotropy

Answer 14

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

Question 15

what is amorphous

Answer 15

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

Question 16

e.g of am amorphoges and lattice

Answer 16

wax- 52 degrees amorphous material,

36 degrees -crystal

Question 17

what is the force that holds atoms together

Answer 17

cohesive forces

Question 18

what is cohesion

Answer 18

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

Question 19

classification of interatomic bonds

Answer 19

primary and secondary

Question 20

primary interatomic bonds

Answer 20

ionic
covalent
metalic

Question 21

secondary interatomic bonds

Answer 21

hydrogen

van der waals forces

Question 22

what is an ionic bond

Answer 22

the mutal attraction between and positive and negativly charged element

Question 23

e.g of ionic bonding

Answer 23

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

Question 24

where can you find ioinc bonding in dentistry

Answer 24

some gypsum and phosphate based cement in their crystalline phases

Question 25

what is a covalent bond

Answer 25

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

Question 26

e.g of covalent bonding

Answer 26

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

Question 27

what are metallic bonds

Answer 27

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

Question 28

what are interatomic secondary bonds

Answer 28

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

Question 29

water in hydrogen bonding

Answer 29

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

Question 30

what happens when multiple H2O molcules mix

Answer 30

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

Question 31

what are Van der Waals forces

Answer 31

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.

Question 32

what is water sorption of a material

Answer 32

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

Question 33

e.g of water sorption

Answer 33

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

Question 34

What is crystalline

Answer 34

having molecules arranged in a regular 3 dimensional pattern | e.g metal

Question 35

charecteristics of crystalline

Answer 35

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

Question 36

what is amorphous

Answer 36

Atoms in crystalline solids exhibit an ordered | arrangement, whereas atoms in amorphous solids lack this long-range periodicity.

Question 37

charecteristics of amorphous

Answer 37

lots of structre defects no set shape mechanical hardness isotrope property