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2 - Operative Dentistry > Clinical Composite > Flashcards

Clinical Composite Flashcards

1
Q

What material is most likely to fail in a restoration?

A

amalgam

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2
Q

What happens to composite materials when they turn from plastic to solid state?

A

change in volume

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3
Q

Where must caries never be left?

A

at the margins of cavities

caries left at the dentine-enamel junction will result in unsupported enamel and early breakdown of the restoration margin if microleakage occurs (bacteria can also colonise)

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4
Q

What does poor enamel preparation margin cause?

A

Composite dimensional change

Etch/bond is stronger than interstitial enamel strength

Interstitial enamel failure - Microleakage

Unsupported enamel

Dentine fracture

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5
Q

Why does enamel fracture occur?

A

due to placement of restoration in a large sum
causes high stress as the large increment changes dimension

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6
Q

What layer is favorable in restorations?

A

hybrid layer - resin interacts with the demineralised structure of dentine

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7
Q

Where is the hybird layer favorable and unfavourable?

A

favourable in primary dentine - open tubules
unfavourable in tertiary dentine - irregular structure

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8
Q

What must be considered with applying the restoration to dentine?

A

Removal of smear layer
Creation of Hybrid layer
Dentine physiology
Peri/inter tubular
Tubule size
Tubule density
Water content
Water transport

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9
Q

What is the smear layer?

What removes it?

A

a layer of material composed of dentine, remnants of pulp tissue and odontoblastic processes, and sometimes bacteria creating during drilling.

it is removed by etching

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10
Q

What is the characteristics of deeper dentine? (secondary)

A

Wetter
More mineralised
More tubules
(closer to pulp)

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11
Q

What is the characteristics of older dentine? (primary)

A

Fewer tubules
More Mineralised
Occluded tubules

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12
Q

What are the characteristics of reactive dentine?

A

Occluded tubules
More mineralised / contaminated
Irregular tubules

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13
Q

What type of mineralisd is best for bonding?

A

bonding happens best when dentine is demineralised and the collagen fibres are exposed for resin to infiltrate into

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14
Q

Is there water in the hybrid layer?

A

no

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15
Q

What adhesion does poor quality dentine allow?

A

adhesion through ion exchange

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16
Q

What are the most important things to think about in a restoration?

A

Cavity preparation
Bonding
Contacts (opposing/adjacent teeth)
Placement
Countering contraction stresses (material changes from plastic>solid)

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17
Q

What is the configuation factor?

A

ratio of bonded surfaces to unbonded surfaces

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18
Q

What does a high CF factor cause?

A

high polymerisation contraction stress

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19
Q

What does polymerisation contraction shrinkage cause?

A

plastic deformation
in turn increasing the stress

marginal and internal gaps, and decreased bond strength.

20
Q

What can polymerisation contraction shrinkage be caused be?

A

Materials
Polymers
Δ Volume
Conversion
Air inhibition

21
Q

What is plasticity?

A

a property of a material to undergo a non-reversible change of shape in response to an applied force (polymerisation)

22
Q

What is deformation?

A

change in shape due to an applied force (contraction)

23
Q

What is plastic deformation also known as?

A

polymerisation contraction

24
Q

What happens if the cavity is perfect, the enamel bond is ideal, however the dentine bond is imperfect and it has been restored in a single increment?

A

interior of restoration peels away from the cavity, material fills with dentinal fluid

when patient chews on tooth, stresses will be transmitted into fluid, causing pain

25
Q

What is the nature of dentine?

A

Type
1°/2°/3°
Intra/Inter/Peri tubular
Diameter
Density
Contents/Mineralization

26
Q

What type of material is useful for contact point prevention?

A

contoured bands allow positioning better than flat bands

27
Q

In what stage of the clinical procedure do issues with CF occur?

A

placement

28
Q

What acid is used for etching?

A

30% phosphoric acid

29
Q

If the dentine is poor quality/tertiary, what should be created to ensure well bonding?

A

a lining usually resin modified glass (RMG)

30
Q

How long does an enamel etch take and how much does a dentine etch take?

A

10 seconds

31
Q

How is the smear layer produced?

A

whenever a handpice is used on dentine, it creates an orangic material that occludes the tubules

32
Q

How should the etch be applied to dentine?

A

after etching enamel, move etchant to surface of dentine to remove smear layer

33
Q

Why should dentine be moist?

A

overdry dentine causes post-operative sensitivity and tubules can collapse inward

most bonding agents contain a solvent which drives off moisture so no need to worry about wet surfaces

34
Q

Why would a lesser filled composite/ more flowable composite be used as a liner?

A

a lesser filled composite will reduce contracion stresses

35
Q

How is the composite placed?

A

in increments touching as few surfaces as possible (low CF)

36
Q

What should the final increments not join?

A

enamel margins

37
Q

What techniques of curing should be used for different goals?

A
  • High Power for fast,
  • Low Power for close-to-pulp
  • Soft Start for polymerisation with reduced contraction stress
38
Q

What are the methods of countering contraction stresses?

A

Strategic Incremental (Cuspal Build-up, C-Factor considerations)

Flowable composite

Warm composite

Curing regime (Intensity, timing and vector)

39
Q

What is the shrinkage direction determidned by?

A

bonded surfaces and free surfaces

40
Q

When do composities shrink towards the light?

A

when bonding fails

41
Q

What tool can help with placing composite shell?

A

silicone matrix

42
Q

What is placed between inscial teeth to avoid contact?

A

proximal strip

43
Q

What is placed between occlusal teeth to avoid contact?

A

sectional matrix and wedge in place

44
Q

What should be done after each increment is placed?

A

curing

45
Q

What should be removed after the mesio-distal side of the tooth has been restored?

A

matrix removed

2 - Operative Dentistry (10 decks)

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