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operative > Adhesion > Flashcards

Adhesion Flashcards

1
Q

What is bonding?

A

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

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2
Q

What is adhesion?

A

surface attachment that involves some types of
intermolecular attraction between adhesive & substrate

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3
Q

What is an adhesive (adherent)?

A

material or film added to produce adhesion
(always liquid)

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4
Q

What is an adherend?

A

substrate to which the material adhered (tooth and restorations)

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5
Q

What is a adhesive joint?

A

the result of interactions of a layer of intermediate material (adhesive) with two surfaces (adherends) producing two adhesive
interfaces

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6
Q

What is the meaning of hydrophilic?

A

having a tendency to mix with, dissolve in, or be wetted by water (water lover)

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7
Q

What is the meaning of hydrophobic?

A

having a tendency to repel or fail to mix with water

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8
Q

What is smear layer?

A

a layer of microcrystalline & organic particle debris that is found spread on surface of tooth structures (enamel & dentin) after
instrumentation

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9
Q

What is etching?

A

selective demineralization of tooth structures by using strong acid (phosphoric acid) for certain period of time (15-30 seconds) to create micro pores (for resin composite)

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10
Q

What is conditioning?

A

cleaning of tooth structures by using weak acid (polycarboxylic acid) for certain period of time (10-20 seconds) for glass ionomer,

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11
Q

What is infiltration/impregnation?

A

flow of adhesive inside the previously created micro pores and in-between the exposed collagen fibrils

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12
Q

What is priming?

A

preparation of dentin surface after etching to facilitate adhesive
infiltration in between collagen fibrils to form a hybrid layer and It is done by a liquid called primer

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13
Q

What is done to prepare dentin surface?

A
  • re-expansion of collapsed collagen fibrils (for infiltration)
  • dry the wet dentin surface
  • copolymerize with the adhesive
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14
Q

What is the hybrid layer?

A

a layer formed in dentin only due to infiltration of adhesive in between exposed collagen fibrils & inside the demineralized inorganic
part of dentin; formed on inter-tubular dentin & responsible of the bond
strength to dentin surface

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15
Q

What are micro-tags?

A

when adhesive is inside micro-pores (infiltrated) and setting is done

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16
Q

What is the different between micro-tags and tags?

A

micro-tags are done on enamel while tags are done on dentin

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17
Q

Micro-pores are also known as…

A

micro-irregularities

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18
Q

What is the clinical significance of adhesion?

A
  • provide stable and long term retention of restoration
  • provide better resistance against fracture of tooth or restoration so the tooth and restoration act as one unit and so reinforce the weakened tooth structure
  • maximise tooth conservation (no removal of sound tooth structure to provide resistance and retention)
  • reduce microleakage at tooth/restoration interface (no post-operative hypersensitivity, marginal staining or caries)
  • expand use of aesthetic restorative dentistry (repair of restorations, aesthetic “invisible” direct restorations, veneers and orthodontics)
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19
Q

Wat are the mechanisms of adhesion?

A
  • physical adhesion: involves electrostatic interactions that are weak
  • chemical adhesion: where there is bonding at the atomic or molecular level across the interface
  • mechanical adhesion: substrate has undercuts or irregularities that produce interlocking of materials
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20
Q

What type of retention do adhesive restorations have?

A

micro-mechanical retention

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21
Q

What is the mono-block concept?

A

restoration and tooth structure act as one unit to avoid wedging of amalgam

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22
Q

Bonding is not material, it is…

A

principle

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23
Q

What are the requirements for adhesion?

A

good wetting

24
Q

What is wetting?

A

degree of spreading of one drop of liquid on a solid surface

25
Q

How is wetting measured?

A

contact angle (angle formed by adhesive with adherend)

26
Q

What are the types of contact angle and their relation to adhesion?

A
  • 0 or 180 degrees = maximum adhesion
  • less than 90 degrees = moderate adhesion
  • more than 90 degrees = poor adhesion
27
Q

What are the requirements for successful wetting of adhesive?

A
  • intimate contact between adhesive and tooth tissues (adherend)
  • cleanliness and dryness of tooth tissues
  • high surface energy of tooth tissue
  • low surface tension of adhesive material (adherent)
  • low viscosity of adhesive to flow and displace air and moisture
28
Q

What is required for sufficient wetting?

A

surface tension of adhesive must be less than surface energy of the adherend

29
Q

What are the types of classifications of contemporary dental adhesion?

A
  • according to smear layer handling mechanism
  • according to adhesion strategy
  • according to clinical application steps
  • chronological classification (not required)
30
Q

According to smear layer handling mechanism, there is…

A
  • smear layer removing adhesives (total removal of smear layer and smear plug)
  • smear layer dissolving adhesives (dissolution)
  • smear layer modifying adhesives (rinsing and adhesive)
31
Q

What are the disadvantages of smear layer removing adhesives?

A
  • hypersensitivity
  • death of pulp
32
Q

What are the advantages of smear layer dissolving adhesives?

A
  • no hypersensitivity
  • no death of pulp
33
Q

According to adhesion strategy (scientific classification), there is…

A
  • etch and rinse adhesives
  • self-etch adhesives
  • glass ionomer adhesives
34
Q

What is the strongest adhesive for bonding of enamel and dentin?

A

etch and rinse adhesives

35
Q

According to clinical application steps, there is…

A

etch and rinse adhesives
- 3 steps (etching + priming + bonding)
- 2 steps (etching + primer and adhesion in one bottle)
self etch system
- 2 steps (self-etch primer + adhesive)
- one step (all in one adhesive)
glass ionomer system
- 2 steps (conditioning + bonding)

36
Q

What are the disadvantages of etch and rinse adhesives?

A
  • post-operative hypersensitivity
  • risk of pulp necrosis
37
Q

When is universal adhesive is used?

A
  • self etching for dentin
  • etch and rinse for dentin
38
Q

What is the gold standard adhesive?

A

etch and rinse adhesives

39
Q

What are the advantages of self-etch adhesives?

A
  • no separate etching
  • good bonding to dentin
40
Q

Is bonding to enamel easier than bonding in dentin?

A

yes

41
Q

Why is enamel easier to bond than dentin?

A
  • enamel is almost homogenous in composition and structure, irrespective of its depth or location
  • composed of 96 wt% in-organic content, mainly hydroxyapatite crystals arranged as enamel rods
  • possesses a high surface-free energy
42
Q

What are the problems in bonding to dentin?

A
  • heterogeneous composition: it contains high percentage of water and organic content, mainly collagen, and only 70 %wt hydroxyapatite
  • complex histological structure: It is composed of numerous dentinal
    tubules surrounded by peri-tubular dentin in addition to inter-tubular
    dentin which is less mineralized
  • inherent intrinsic wetness: the dentinal tubules are filled with dentinal fluid at constant wetness (deep dentin has more intrinsic wetness)
  • dentin is a dynamic tissue with continuous physiologic and pathologic changes
  • presence of smear layer on the cut surface
42
Q

What causes the formation of smear layer?

A

cutting of dentin with hand and rotary instrumentation –> smear layer (2-5 microns) is formed on the surface of dentin

43
Q

Is smear layer found in enamel?

A

yes

44
Q

What are the properties of smear layer?

A
  • this layer is burnished on the cut surface by the effect of heat and
    pressure of cutting –> not removed by rinsing
  • tt is formed of chips, hydroxyapatite crystals, collagen, saliva and blood and microorganisms
  • becomes packed inside the dentinal tubule –> smear plug
  • in enamel, it is composed of larger apatite crystals tightly bound by
    salivary glycoprotiens and microorganisms
45
Q

What is selective etch and rinse adhesive (smear layer removing
adhesives)?

A
  • incorporate etching step (total etching of enamel and dentin) using 30-40% phosphoric acid and etching time of 15-30 seconds
  • acid etchant is supplied in the form of a liquid or colored gel (gel form is preferred because it is easier to control)
  • etchant must be rinsed with water for 5-10 seconds to remove the
    acid and the dissolved calcium phosphates
46
Q

What are the steps of selective acid and etch adhesive?

A
  • selective demineralization (etching)
  • priming
  • bonding (infiltration of adhesive resin)
46
Q

What are the advantages of etch and rinse adhesives?

A
  • effective bonding with enamel and dentin with long-term clinical results
  • 3-steps adhesives are considered the gold standard of adhesives
47
Q

What are the disadvantages of etch and rinse adhesives?

A
  • time consuming due to multi-steps required
  • risk of over-etching (pulp necrosis) due to aggressive phosphoric acid
  • post-operative sensitivity due to dentinal fluid movement
48
Q

What are self-etch adhesives (smear layer dissolving adhesives)?

A
  • self-etch adhesives are without separate etching step
  • they use acidic primers, called self-etching primers, which condition and prime the tooth substrate at the same time
  • dissolved smear layer and the demineralization products are not rinsed away but incorporated in the adhesive resin and into the hybrid layer.
  • the system is either 2-step or 1-step (all in one)
49
Q

What is the procedure glass ionomer adhesives (smear layer modifying adhesives)?

A
  • conditioning dentin with weak concentration (10-20%) polyalkenoic
    (polyacrylic) acid for 10 seconds removes the smear layer but not the smear plugs –> clean dentin surface –> shallow demineralization for hybridization and sufficient residual hydroxyapatite for chemical bonding
  • the acid is then rinsed with water
  • the resin-modified glass ionomer bond is placed
50
Q

What are the advantages of glass ionomer adhesives?

A
  • self-adhesive system
  • cariostatic potential by release of fluorides
51
Q

What is the disadvantage of glass ionomer adhesives?

A

no long term clinical data

52
Q

What is the ideal bonding protocol with cases in which bonding to enamel and dentin will be needed

A

selective etch technique

53
Q

What is the protocol of selective etch technique?

A

enamel etching using phosphoric acid for 30 seconds
- no etching of dentin is required
- application of universal adhesive on enamel & dentin –> with enamel it works as etch & rinse adhesive (it requires etching) –> with dentin it works as self-etch adhesive (no need for etching)
- light curing of the universal adhesive for 20 seconds

54
Q

What are the advantages of selective etch technique?

A
  • provides maximum bond with enamel & dentin
  • etching of enamel guarantee perfect sealing of the restoration margin (no leakage)
  • minimizes post-operative hypersensitivity & risk of pulp injury as dentin etching was excluded
55
Q

What are the indications of selective etch technique?

A
  • Anterior & posterior resin composite restorations
  • cementation of indirect composite and ceramic restorations
  • cementation of ceramic crowns & veneers
  • used in all cases of bonded restorations

operative (6 decks)

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