Adhesion

Question 1

dental bonding

Answer 1

enamel and dentine bonding

Question 2

etching

Answer 2

act or process of making designs/imprints on a surface (metal/glass) by the corrosive action of acid based solutions (surface treatment/removal)

Question 3

adhesion

Answer 3

force that binds 2 dissimilar materials together when they are brought into intimate contact

Question 4

criteara for adhesion

Answer 4

intimate contact at a molecular level
formation of attractive bonds
wettability

Question 5

what affects the intimate contact at a molecular level

Answer 5

viscosity of the adhesive

surface roughness of the substrate

Question 6

solid to liquid adhesion

Answer 6

complete intimate contact (liquid flows on the grooves of the solid)
secondary bonds (van Der wals) - see pic for lec

Question 7

solid to solid adhesion

Answer 7

If both solids are rough
- won’t fit together
- only specific places of intimate contact due to surface roughness
not easy to achieve contact at the microscopic level

Question 8

distance needed for adhesion to occur

Answer 8

less than 0.0007um for adhesion to occur

Question 9

Uses for fluid/semi fluid intermediaries

Answer 9

solid -liquid- solid adhesion

clean surface is key to intimate contact

Question 10

wettabiltiy

Answer 10

ability of an adhesive to contact a substrate depends on the wet ability of the adhesive on that particular substrate
see lec for pic demonstration

Question 11

Surface energy - surface

Answer 11

imbalance that gives raise to the surface energy of the material (surface tension in liquids)

Question 12

surface energy - bulk

Answer 12

attractive forces in all directions

all molecules in the surface have an imbalance of energy

Question 13

what is surface tension in liquids

Answer 13

where all liquids have an imbalance of energy

-attractive forces in all diresctions

Question 14

what is required for perfect wetting

Answer 14

critical surface energy of the solid has to be greater than the surface tension of the liquid
- solid needs energy (higher surface energy ) to spread the liquid by pulling the molecules

Question 15

surface tension measured in

Answer 15

Mj/m2( squared)

Question 16

how do you measure wettability

Answer 16

contact angles

Question 17

contact angle

Answer 17

smaller the contact angle

• more hydrophilic
  i. e. more wetable

Question 18

mechanisms of adhesion

Answer 18

physical
chemical
micromechnical
molecular entanglement

Question 19

Physical adhesion

Answer 19

van der Waals and hydrogen binding and dipole interaction

• rapid but reversible and weak bonding
• not sutible for permanent bonding but can be a precursor for chemical

Question 20

Permanent dipole ovement

Answer 20

molecules are pilar

- hydrogen bonds due to electromagnetic attraction between polar molecules

Question 21

temporary induced dipole movemnt

Answer 21

non polar molecules do not normally have a dipole moment but can have a temporary dipole

Question 22

temporary dipole cuase

Answer 22

distortion of electron cloud

• induced electrical interactions between 2 or more atoms or molecules that are close to each other
• atoms have a positive charge in the nucleus, electrons around the outside

Question 23

chemical adhesion

Answer 23

covalent and ionic bonding

and metallic

Question 24

metallic

Answer 24

share electrons

Question 25

what are dental adhesives

Answer 25

generally solution of resin monomers with hydrophilic and hydrophobic

Question 26

Examples of dental adhesive

Answer 26

curing initiators
inhibitors
solvents
inorganic fillers

Question 27

micro mechanical adhesion

Answer 27

microscopic undercuts (rough surface)
clean surface
wetability is key

Question 28

how can you remove micromechanical bonding

Answer 28

fracture it

- uncle to disengade from undercut

Question 29

what is needed for molecular entanglement

Answer 29

need a highly porous surface
add a monomer
- there is no clear border between materials

Question 30

steps for molecular entangle metn

Answer 30

etch one of the components

• monomer is infiltrated, part of the adhesive is able to penetrate the surface and adsorb into it
• cure it
• leaves a locking effect/hybrid zone

Question 31

why is adhesion important

Answer 31

• allows us to do previously impossible procedures (eg solid solid)
• conserve/reinforce tooth structure
• prevent micro infiltrations