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BDS2 CDS Operative Techniques > Principles of Cavity Preparation > Flashcards

Principles of Cavity Preparation Flashcards

1
Q

definition of a plastic

A

something that is mouldable, flexible till turns hard due to change in chemical compostition

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2
Q

what 3 things determine cavity design?

A
  • structure and properties of the dental tissues
  • the diseases
  • properties of restorative materials
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3
Q

what diseases can cause a cavity?

A
  • dental caries
  • periodontal disease
  • tooth surface loss (largely due to lack of hygiene, care and poor diet)
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4
Q

in cavity design there is a strong relationship between….

A
  • the position of the caries
  • the extent of the caries
  • the shape of the prepared cavity
  • the final restorative material
    each of these properties must be reviewed and reassessed continually when preparing a tooth to receive a restoration
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5
Q

4 different caries positions

A
  • pit & fissure
  • approximal (posterior and anterior)
  • smooth surface (typically around gingival margin)
  • root
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6
Q

when should you operatively intervene?

A
  • lesion has cavitated
  • patient can’t access the lesion for prevention
  • the lesion is into dentine
  • lesion is causing pulpitits
  • lesion is unaesthetic
    decisions can be difficult
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7
Q

qualities of enamel

A
  • brittle
  • along prisms
  • unsupported enamel and/or under occlusal load should be removed before restoration
  • N.B. Dry tissue - need to etch
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8
Q

importance of operative procedures around dentin-pulpal complex

A

operative procedures involving dentine affect pulp

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9
Q

dentine qualities

A
  • porous
  • more elastic
  • N.B wet tissue
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10
Q

what happens to gingival tissues when plaque is present?

A

become inflammed

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11
Q

structure of enamel effect on cavity design

A

prismatic structure

side cut or end cut effects etching

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12
Q

what is the weakest point?

A

where 2 material join
- breaking point
consider where edges of cavity relate to where teeth are

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13
Q

primary dentine structure

A
  • open tubules

- wet as not as many materials can bond unlike enamel

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14
Q

tertiary dentine structure

A

reaction of trauma to tooth

has a different structure - more unorganised

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15
Q

principles of preparation are driven by:

A
  • caries removal
  • necessary finishing required for maximum adhesion, occlusal relationships, ease of patient cleaning, properties of the materials used
  • no attempt should be made to remove any healthy tissue for any reason unless required
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16
Q

only cases when remove healthy tooth tissue

A
  • material used for the restoration requires it
  • margins of the cavity are in contact with another tooth surface
  • margins of the cavity cross an occlusal contact
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17
Q

6 principles of cavity design & preparation

A

• Identify and remove carious enamel
• Remove enamel to identify the maximal extent of the lesion at the amelodentinal junction & smooth the enamel margins
• Progressively remove peripheral caries in dentine – from the ADJ first, then circumferentially deeper.
• Only then remove deep caries over pulp
• Outline form modification
o Enamel finishing
o Occlusion
o Requirements of the restorative material
• Internal design modification
o Internal line and point angles
o Requirements of the restorative material

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18
Q

modification for amalgam

A

undercuts for retention

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19
Q

modification for composite

A

none

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20
Q

cavosurface margin

A

margin between internal enamel/dentine and external enamel

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21
Q

what should the final cavosurface margin be like?

A
  • remove any unsupported enamel by etch technique
  • smooth cavosurafce margins and line angles
  • ensure there are no excessively acute line angle transitions and that the outline form is smooth and rounded (sharp line angles can cause cracks potentially)
  • check for stress concentrators
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22
Q

when removing an existing restoration

A

ensure no traces of restorative material remaining

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23
Q

what should line and point angles be like?

A

smooth

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24
Q

line angle

A

junction between wall and floor

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25
Q

point angle

A

where 3 planes meet

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26
Q

5 points to remember for the final seal of the restoration

A
  • smooth margins
  • appropriate CSMA
  • no unsupported tooth tissue
  • no stress concentrators
  • internal anatomy that allows adaptation of material
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27
Q

after preparation what do you need to do?

A

clean the cavity to ensure free from debris

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28
Q

how to remove an existing restoration?

A

start from the centre of the restoration and cut towards the edge of the cavity
NEVER remove a restoration by cutting around the edges as will increase the size of the cavity
- use high speed to cut into pieces
- chip out chunks where possible
- remove all and any underlying base material

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29
Q

how to detect dentinal caries?

A

brown stain or softened tissue when using a sharp probe

sound dentine doesn’t yield under probing

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30
Q

what does sticking of probe to dentine indicate?

A

residual carious dentine which should be removed

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31
Q

what should you never probe?

A

uncavitated carious enamel as can fracture

32
Q

what do you remove first residual dentinal caries from ADJ or pulpal floor?

A

remove residual dentinal caries from ADJ first and then residual dentinal caries last from pulpal floor

33
Q

how to remove caries from ADJ a?

A

• Hand-held excavator
• Round bur
• Chemo-mechanical caries removal
Caries detector dyes may be helpful

34
Q

what do you need to be cautious about when removing caries from pulpal floor?

A

pulp exposure

- birr more likely to expose pulp so better to use hand tools

35
Q

what instrument should be used to remove caries from pulpal floor?

A

largest instrument which will conveniently work in the cavity
- large round burr
- large hand held excavator
- chemo-mechanical caries removal
too small = too deep too fast = pulp exposure

36
Q

when is carious pulp exposure a necessity?

A 
pulp therapy 
•	Direct and Indirect Pulp Cap (CaOH)
•	Exposing a healthy pulp
•	Importance of symptoms
traumatic exposure should be avoided
37
Q

importance of the ADJ

A

always check for Caries at ADJ!
• If access can remove with slow or high speed
• Enamel brittle - can it be reinforced by restorative material to be stable
• Or remove (sometime if amalgam)

38
Q

modification for enamel margins

A

etch

39
Q

modification for cavosurface margin angle

A

ensure smoothed off

check for stress concentrators

40
Q

modification for occlsuion

A

junction with material and enamel going to be strong enough to withhold the occlusal force

41
Q

modification for internal anatomy

A

check for stress concentrators

42
Q

stress concentraotrs

A

ability of base of material to resist cracking

43
Q

3 most commonly used materials for direct plastic restoration are:

A
  • composite
  • amalgam
  • resin modified glass ionomer
44
Q

what is the material of choice for restorations?

A

composite - no features needed for retention

45
Q

8 advantages of composite

A 
	Aesthetics
	 Conservation of tooth tissue
	 Support for remaining tooth tissue
	 Adhesion/bonding
	Command cure
	 Low thermal conductivity
	 Elimination of galvanism
	 Amalgam alternative?
46
Q

disadvantage of composite

A

operator sensitive - can go greatly wrong

47
Q

3 disadvantages of amalgam

A
  • does not bond to enamel or dentine
  • does not support the tooth
  • not tooth coloured
48
Q

how is amalgam held in?

A

by retention and resistance form

cut dentine may require sealed dentine layer

49
Q

3 reasons why amalgam prevented from fracture

A
  • adequate bulk (at least 2mm deep)
  • retention and resistance - need to remove healthy tissue
  • strong under occlusal load
    less moisture and technique sensitive
50
Q

positives of amalgam

A

less moisture and technique sensitive

- simple, quick and relatively easy

51
Q

what is amalgam retention?

A

features of cavity which prevent the restoration being dislodged in any occlusal direction
- anatomical cavity design features e.g. undercuts, dovetail, key, isthmus

52
Q

when is retention not essential?

A

for adhesive restorations

53
Q

what do non-adhesive restorations require?

A

retention factors
internal dimensions of the cavity greater than access into it

cavosurface angles adjusted to increase bonding area and ensure no unsupported enamel

54
Q

what happens to cavosurface angles in amalgam restorations?

A

cavosurface angles adjusted to increase bonding area and ensure no unsupported enamel
- required for adhesive restoration
undercuts unnecessary

55
Q

bevel

A

corner rounded out

56
Q

line angle

A

2 planes intersect

57
Q

point angle

A

3 planes intersect

58
Q

how should the cavity margin/restoration interface be designed for maximum strength and minimum leakage? (3)

A
  • all cavity margins should be caries free
  • all cavity margins should be free of contact with the adjacent tooth
  • all cavity margins should be accessible for cleaning
59
Q

what is the general cavoisurface angle for amalgam?

A

90-120 degrees

Butt joint

60
Q

what is the most important factor to consider for cavity margins for amalgam?

A

avoid inappropriate CSMA or unsupported enamel

61
Q

what will caries at cavosurface angle result in?

A

caries at the dentine-enamel junction will result in unsupported enamel and early breakdown of the restoration margin if micro-leakage occurs

62
Q

configuraion factor

A

ratio of bonded:unbonded surfaces in the restoration

63
Q

high configuration factor means

A

increased polymerisation contraction stress

e.g. occlusal only one exposed surface, all the others in the tooth

64
Q

low configuration factor means

A

reduced polymerisation contraction stress

65
Q

what is the result of configuration stress?

A
  • composite dimensional change

- etch/bond is stronger than interstitial enamel strength

66
Q

what bond strength is stronger - to enamel or dentine?

A

bond strength to enamel is stronger than to dentine

more likely to have serious bond failure to dentine

67
Q

what does polymerisation stess lead to?

A

enamel failure

- etch/bond is stronger than interstitial enamel strength

68
Q

how to clean up the cavity?

A
  • wash the cavity with a mixture of air and water to remove loose debris
  • rinse with chlohexidine and remove
  • rinse with water and leave surface moist
69
Q

what will be in the cavity after preparation?

A
  • loose enamel and dentine chippings

- organic and inorganic dentine debris smeared into the walls of the cavity

70
Q

what should you do if caries close to the pulp?

A

manipulate over soft remaining caries to see if remineralised or tertiary dentine forms
• Means wait for patient
• And some risks
But can be better than breaching pulp - sometimes done in paeds

71
Q

important points for cavity preparation

A
  • Not always necessary to remove all the caries
  • Protect the airway and the pulp
  • Decide on your choice of material AFTER caries removal
  • Design the cavity considering the remaining tooth tissue, its quality and the choice of material
  • Think conservation of tooth tissue
  • Think about sealing vital dentine
  • Attention to detail avoids problems
72
Q

principles of cavity design and preparation

A
  • Identify and remove carious enamel
  • Remove enamel to identify the maximal extent of the lesion at the amelodentinal junction & smooth the enamel margins
  • Progressively remove peripheral caries in dentine – from the ADJ first, then circumferentially deeper.
  • Only then remove deep caries over pulp
  • Outline form modification
  • Enamel finishing
  • Occlusion
  • Requirements of the restorative material
  • Internal design modification
  • Internal line and point angles
  • Requirements of the restorative material
73
Q

retention

A

the ability of a cavities anatomy to prevent loss of a non-adhesive restorative material

  • undercuts (Shaping the cavity to have a wider base closer to the pulp and a narrower opening)
  • occlusal extension of the cavity is wider on the occlusal surface when compared with access through the marginal ridge, this allows amalgam to interlock with the tooth without bonding
74
Q

resistance

A

the ability of a cavities anatomy to prevent displacement of a non-adhesive restorative material

75
Q

undercuts

A

internal dimensions of the cavity are greater than the access into it
- Shaping the cavity to have a wider base closer to the pulp and a narrower opening

76
Q

why is it essential for the matrix band to adapt and enclose the gingival floor?

A

to avoid overhangs

BDS2 CDS Operative Techniques (5 decks)

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