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BDS2.5 Dental Materials - operative dentistry > Dental Materials - Bonding systems > Flashcards

Dental Materials - Bonding systems Flashcards

1
Q

What is dental bonding?

A

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

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2
Q

What is sealing?

A

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

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3
Q

What is the difference between bonding and healing?

A

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

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4
Q

What is wetting?

A

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

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5
Q

How is adhesive usually applied as?

A

a liquid

allows surfaces to be bonded

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6
Q

What needs to occur for good binding to occur?

A

wetting (adhesive)

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7
Q

what is high viscosity?

A

thick liquid

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8
Q

What is surface tension?

A

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

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9
Q

What are the 3 types of adhesion?

A

mechanical
physical
chemical

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10
Q

What types of surface does mechanical adhesion rely on?

A

rough microscopically

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11
Q

How does mechanical adhesion work?

A

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.

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12
Q

How does physical adhesion work?

A

between 2 surfaces

the molecular charges (opposite charges of substrates attract)

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

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13
Q

Is the physical adhesion bon weak or strong?

A

relatively weak, readily breaks down

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14
Q

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

A

greater surface area

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15
Q

cohesive vs adhesive failure

A

cohesive = chemical adhesion… one of the substrates dissociates

adhesive = at the interface

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16
Q

What is the aim of dental bonding?

A
  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)
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17
Q

what is the bonding agent?

A

liquid resin

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18
Q

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

A

micro-mechanical bond

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19
Q

What are the essential prerequisites for a substrate surface?

A

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

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20
Q

What is prophylaxis?

A

treatment given or action taken to prevent disease

21
Q

What is the first step (removing the pellicle)?

A

use a pumice slurry

(volcanic stone and water)

22
Q

Is enamel mainly organic or inorganic?

A

inorganic

23
Q

Why is bonding to enamel complicated?

A

the outer 5um of the enamel surface is amorphous

provides very limited means of retention for restoration

no form and limited means for restoration

24
Q

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

A

acid etch technique

25
Q

What is the acid etch technique?

A

acid partly demineralises the crystalline structure of enamel

26
Q

What does the acid etch technique remove?

A

removal of the crystallites (interprismatic enamel)

27
Q

Is this image before or after the acid etch technique?

A

after

clefts has formed

28
Q

Why use the acid etch technique?

A

create a tight micro-mechanical lock

wetting can flow between prisms

29
Q

What bond is formed with acid etch technique?

A

micromechanical bond

30
Q

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

A
31
Q

Wat appearance does etched enamel formed?

A

frosted appearance

32
Q

What is bevelling enamel?

A

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

33
Q

What does bevelling enamel cause?

A

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

34
Q

What need longer etch time?

A

older enamel

35
Q

Why does older enamel need a longer etch time?

A

exposed to fluoride

36
Q

What considerations should you take with primary enamel?

A

more prismless enamel at the surface

acid takes longer to penetrate the enamel layer and create the etch pattern

increase etch time

37
Q

Are bond strengths higher or lower in children and why?

A

lower

teeth are less calcified than permanent enamel

38
Q

What is the problem of over-etching?

A

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

39
Q

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

A

no

40
Q

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

A

left is ideal

right is over-etched

41
Q

Describe the over-etched enamel on the right

A

lost the inter-prismatic layer

clefts are a lot deeper

not a great surface area, not good for resin infiltration

42
Q

Can you repeat the etching step on the same surface?

A

no

43
Q

When will etching need to be repeated?

A

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

44
Q

Are bonding agents hydrophilic or hydrophobic?

A

hydrophobic

45
Q

What acid is used with etching?

A

ortho-phosphoric acid

46
Q

What is the optimum concentration of ortho-phosphoric acid?

A

30-50%

47
Q

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

A

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

48
Q

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

A

35-37% for 15-30 seconds

BDS2.5 Dental Materials - operative dentistry (22 decks)

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