Dental Materials - Bonding systems

Question 1

What is dental bonding?

Answer 1

process of attaching a resin composite based material to the underlying tooth tissue using some form of intermediate material

Question 2

What is sealing?

Answer 2

achievement of an impermeable barrier between the cavity wall and the restorative material to prevent the passage of bacteria

Question 3

What is the difference between bonding and healing?

Answer 3

although a material may appear to be stuck to another material every part of the 2 surfaces may not be in intimate contact with each other

Question 4

What is wetting?

Answer 4

the ability of a material to achieve an intimate microscopic contact with another

Question 5

How is adhesive usually applied as?

Answer 5

a liquid

allows surfaces to be bonded

Question 6

What needs to occur for good binding to occur?

Answer 6

wetting (adhesive)

Question 7

what is high viscosity?

Answer 7

thick liquid

Question 8

What is surface tension?

Answer 8

the ability of the surface of a liquid to resist an external force

Question 9

What are the 3 types of adhesion?

Answer 9

mechanical
physical
chemical

Question 10

What types of surface does mechanical adhesion rely on?

Answer 10

rough microscopically

Question 11

How does mechanical adhesion work?

Answer 11

if both surfaces are uncontaminated, the irregularities may connect with one another

depending on their respective roughness, the two surface may become intimately related

any attempt to slide one against the other is resisted by friction.

Question 12

How does physical adhesion work?

Answer 12

between 2 surfaces

the molecular charges (opposite charges of substrates attract)

substrates orientate so the oppositely charged molecules are adjacent to each other

Question 13

Is the physical adhesion bon weak or strong?

Answer 13

relatively weak, readily breaks down

Question 14

What factor gives the physical adhesion more chance for the forces to attract?

Answer 14

greater surface area

Question 15

cohesive vs adhesive failure

Answer 15

cohesive = chemical adhesion… one of the substrates dissociates

adhesive = at the interface

Question 16

What is the aim of dental bonding?

Answer 16

1. surface of the tooth is rough
2. intervening layer of resin fills these micro- and macroscopic irregularities
3. the restorative material is rough (bonding agent)

Question 17

what is the bonding agent?

Answer 17

liquid resin

Question 18

How would you describe the bond between the restorative material and tooth?

Answer 18

micro-mechanical bond

Question 19

What are the essential prerequisites for a substrate surface?

Answer 19

rough
high surface area
good wetting properties
high surface energy
free from debris an organic material
dry

Question 20

What is prophylaxis?

Answer 20

treatment given or action taken to prevent disease

Question 21

What is the first step (removing the pellicle)?

Answer 21

use a pumice slurry

(volcanic stone and water)

Question 22

Is enamel mainly organic or inorganic?

Answer 22

inorganic

Question 23

Why is bonding to enamel complicated?

Answer 23

the outer 5um of the enamel surface is amorphous

provides very limited means of retention for restoration

no form and limited means for restoration

Question 24

The outer layer of enamel is amorphous, how do you overcome this? (prepare the substrate)

Answer 24

acid etch technique

Question 25

What is the acid etch technique?

Answer 25

acid partly demineralises the crystalline structure of enamel

Question 26

What does the acid etch technique remove?

Answer 26

removal of the crystallites (interprismatic enamel)

Question 27

Is this image before or after the acid etch technique?

Answer 27

after clefts has formed

Question 28

Why use the acid etch technique?

Answer 28

create a tight micro-mechanical lock wetting can flow between prisms

Question 29

What bond is formed with acid etch technique?

Answer 29

micromechanical bond

Question 30

What is achieved with etching with an acid? (learn)

Answer 30

Question 31

Wat appearance does etched enamel formed?

Answer 31

frosted appearance

Question 32

What is bevelling enamel?

Answer 32

quality of etching pattern is improved by bevelling the enamel (margins prepared at an angle of c120 degrees using a diamond bur)

Question 33

What does bevelling enamel cause?

Answer 33

removes the outer amorphous enamel exposing fresh enamel of boding and roughening its surface Alters the angulation of the enamel prisms ad ensures that no unsupported prisms remain

Question 34

What need longer etch time?

Answer 34

older enamel

Question 35

Why does older enamel need a longer etch time?

Answer 35

exposed to fluoride

Question 36

What considerations should you take with primary enamel?

Answer 36

more prismless enamel at the surface acid takes longer to penetrate the enamel layer and create the etch pattern increase etch time

Question 37

Are bond strengths higher or lower in children and why?

Answer 37

lower teeth are less calcified than permanent enamel

Question 38

What is the problem of over-etching?

Answer 38

the porosities produced are not so numerous decalcifies the substrate to too great a depth so losing the etch pattern decrease ability of the resin to form tags to penetrate into the etched pattern lower bond strength results

Question 39

Can you determine clinically if the enamel is over-etched?

Answer 39

no

Question 40

What side is the ideal-eched and the over-etched side?

Answer 40

left is ideal right is over-etched

Question 41

Describe the over-etched enamel on the right

Answer 41

lost the inter-prismatic layer clefts are a lot deeper not a great surface area, not good for resin infiltration

Question 42

Can you repeat the etching step on the same surface?

Answer 42

no

Question 43

When will etching need to be repeated?

Answer 43

if the area becomes contaminated by blood or saliva during the bonding process

Question 44

Are bonding agents hydrophilic or hydrophobic?

Answer 44

hydrophobic

Question 45

What acid is used with etching?

Answer 45

ortho-phosphoric acid

Question 46

What is the optimum concentration of ortho-phosphoric acid?

Answer 46

30-50%

Question 47

What is the problem of the ortho-phosphoric acid being too concentrated?

Answer 47

small amount of water present does not get saturated with reaction by-products quickly as this would slow the dissolution rate

Question 48

What is the most common concentration of ortho-phosphoric acid and applied for how long?

Answer 48

35-37% for 15-30 seconds