Surface and Interfaces

Question 1

Adhesive principles are used in which dental specialties?

Answer 1

ALMOST ALL
Operative 
prosth
peds
ortho
endo

Question 2

adhesion

Answer 2

when 2 unlike substances join together on being brought into contact because of forces of attraction between them

Question 3

cohesion

Answer 3

attraction between like molecules

Question 4

adhesive

Answer 4

material used to produce adhesion

Question 5

adherend

Answer 5

subtance to which an adhesive is applied

Question 6

application of adhesive technology is very critically dependent on…

Answer 6

practical technique

Question 7

knowledge of physics and chemistry of surfaces is ___

Answer 7

essential

Question 8

surfaces have ______ from the bulk of the material

Answer 8

different properties

Question 9

Adhesion critically depends on _____

Answer 9

surface properties

Question 10

What are the requirements of adhesion?

Answer 10

• fluid adhesive
• reactive adherend/solid surface
• interaction bc adhesive and adherend
• creation of a stable interface

Question 11

surface tension

Answer 11

force of attraction exterted on surface mols of a LIQUID by the mols beneath the surface

Question 12

Surface free energy

Answer 12

atoms on SOLID surfaces may have higher energy than the atoms in the bulk of the material
The atoms on the surface are not surrounded by atoms of its own nature, so:
- surface atoms interact more strongly with eachother
- May attract atoms/mols = more reactive

Question 13

Adsorption

Answer 13

adhesion of atoms/ions/biomolecules/molecules of gas/liquid/dissolved solids on a SURFACE

Question 14

Absorption

Answer 14

absorbed substance is incorporated into the BULK of material

Question 15

what are they types of adsorption

Answer 15

cemisorption

physical adsorption

Question 16

chemisorption

Answer 16

type of adsorption
chemical rxn (usually irreversible) has taken place
DESIRED FOR ADHESIVES

Question 17

physical adsorption

Answer 17

establishment of Van der Walls forces
Weak/secondary bonds
More readily reversible

Question 18

contact angle

Answer 18

angle of contact made by a drop of liquid on a surface
Measures ability of liquid to wet a surface - determines reactivity of surface

The more reactive the surface, more water is going to interact w it = lower contact angle

Question 19

hydrophobic surfaces have ____ contact angles

Answer 19

Large

poor wetting hydrophobic surface

Question 20

hydrophilic surfaces have ____ contact angles

Answer 20

small/0

excellent wetting hydrophilic surface

Question 21

What 2 factors determine the reactivity of a solid surface and adhesion

Answer 21

1. chemical and physical-chemical reactivity between surface and adhesive
2. Physical form
   - roughness - mechanical interaction
   - porosity - hybridization

Question 22

How does contact angle relate to reactivity of a subtance

Answer 22

More reactive surface = more water will interact with it = drop will spread more = LOW CONTACT ANGLE

Question 23

What are the three mechanisms for adhesion? (1 or more can contribute to bond strength)

Answer 23

1. chemical bonding
2. micromechanical adhesion
3. hybridization bonding

Question 24

If a surface is very reactive to an adhesive, adhesion between the two will be ______

Answer 24

IMPROVED

Question 25

How can you increase the reactivity/surface free energy and the interaction with the adhesive w the surface?

Answer 25

chemical and physical chemical changes to surface

physical/morphological changes to surface

Question 26

micromechanical adhesion

Answer 26

liquid flows into irregularities/pores/crevices in surface

Fluid sets = micromechanical interlocking

Question 27

hybridization bonding

Answer 27

1 phase penetrates via diffusion into surface of a 2nd phase = hybrid layer

Question 28

Which dental materials use chemical adhesion?

Answer 28

GI cements + tooth
Adhesive resins + alloys
Silane agents + ceramics
PFM

Question 29

which dental materials use micromechanical adhesion?

Answer 29

Adhesion to etched enamel
Dentin bonding
Abraded alloy surfaces
Etched ceramics

Question 30

how is hybridization bonding used in dentistry?

Answer 30

Bonding to dentin

Question 31

How does chemical adhesion work in GI cements to tooth

Answer 31

GI formed from polyalkenoic acid monomers with carboxylic COOH goups

GI + water = ionized COO- (v reactive)

Ionic attraction bc COO- and Ca2+ in dentin/enamel = neutralize charge

= STRONG IONIC BOND

Question 32

How do you prepare a tooth for micromechanical bonding?

Answer 32

1. etch
2. rinse
3. dry
4. apply adhesive

Question 33

Etching enamel results in:

Answer 33

clean surface
rough surface
chemically ractive = high surface free energy, high critical surface tension

Question 34

Why is drying enamel after etching a critical step in adhesion?

Answer 34

Traditional adhesives are not strongly hydrophilic

Question 35

Which 3 substances must be used to allow hybridization adhesion to dentin?

Answer 35

conditioner (rinsed)
primer
adhesive

Question 36

Conditioner

Answer 36

Substance applied to surface to REMOVE SOME OF SURFACE

Opens dentinal tubules + demineralizes dentin = collagen fibers

Question 37

Primer

Answer 37

Substance applied to conditioned dental to aid adhesion
LEFT IN SITU
Hydrophilic - better rxn w dentin
Adheres to dentin and adhesive
Penetrates tubules and net of un-reacted collagen
Light cured
FORMS HYBRID LAYER = entangled primer + collagen fibers

DIFFUSION BONDING

Question 38

Adhesive used during hybridization bonding to dentin

Answer 38

Resin/adhesive applied to conditioned and primed dentil

Will also adhere to restorative material

Question 39

Bonding to dentin is an example of what kind of bonding?

Answer 39

diffusion bonding