principle of adhesion

Question 1

what are the 3 principles of adhesion

Answer 1

1. 2 materials must be sufficiently close and intimate relation
2. debris on surface will prevent direct contact between adhesive and adherent which would decrease adhesion strength

3.adequate wetting of adhesive is when contact angle is less than 90degrees

Question 2

a __ in surface energy and ___ in surface tension will increase adhesion strength

Answer 2

increase, decrease

Question 3

what are some factors that increases strength of adhesive junction

Answer 3

1. lower viscosity of adhesive, easy flow on adhesive surface
2. thiner adhesive layer which decreases air voids
3. irregularity of substrate, which increases bonding surface and increase adhesion strength

Question 4

what is the purpose of etching enamel, and what is used to do it?

Answer 4

to remove smear layer, produce pores in enamel surface so adhesive can penetrate to form tag-like extension.

increases surface energy of enamel which increase wetting

increases surface area of enamel

37% phosphoric acid used

Question 5

what is primer comprised of

Answer 5

• HEMA dissolved in organic solvents

Question 6

what does HEMA in primer do

Answer 6

it is hydrophillic, it improves wettability and promote re-expansion of collagen network

Question 7

what is the classification of the bond between composite and adhesive

Answer 7

bonds chemically