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bds 2 > principles of cavity preparation > Flashcards

principles of cavity preparation Flashcards

1
Q

What determines cavity design? (3 points)

A
  • Structure and properties of the dental tissues
  • The diseases (caries, Periodontal disease, tooth surface loss)
  • Properties of restorative materials
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2
Q

What was the problem with Black’s classification of cavities?

A

Healthy tooth tissue was also removed

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3
Q

There are 4 factors that must be reviewed and reassessed continually when preparing a tooth to receive a restoration. What are these factors?

A
  • The position of caries
  • The extend of caries
  • The shape of the prepared cavity
  • The final restorative material

(there is a strong relationship between these factors)

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4
Q

Where can the position of caries in the tooth be? (4 points)

A
  • Pit and fissure
  • Approximal (posterior or anterior)
  • Smooth surface (typically around gingival margin)
  • Root
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5
Q

What is the general guidance for when to intervene and do a restoration? (2 points)

A

When the lesion is cavitated
When the patient can’t access the lesion for prevention

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6
Q

What is the guidance for when to consider if a restoration is needed? (3 points)

A
  • The lesion is into dentine radiographically
  • The lesion is causing a pulpitis
  • The lesion is unaesthetic
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7
Q

What are ‘dead tracts’?

A
  • When dentine is damaged, odontoblastic processes die or retract leaving empty dentinal tubules.
  • Areqas with empty dentinal tubules are called dead tracts and appear as dark areas in ground sections of a tooth
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8
Q

With time, dead tracts can become completely filled in mineral. This region appears white in sections of ground tooth. What are these sections called?

A

Blind tracts

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9
Q

What is the dentine in blind tracts called?

A

sclerotic dentine

sclerosis - calcification of the dentinal tubules as a result of injury or normal aging

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10
Q

What is the adaptive advantage of blind tracts?

A

The sealing off of the dentinal tubules to prevent bacteria from entering the pulp cavity

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11
Q

When is primary dentine formed?

A

When tooth begins to form

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12
Q

When is secondary dentine formed?

A

Once the tooth is fully formed

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13
Q

When is tertiary dentine formed?

A

After damage has been done to the tooth

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14
Q

What are the principles of cavity preparation driven by? (5 points)

A
  • Caries removal (consider cavity shape and material that should be used)

Necessary finishing required for:

  • Maximising adhesion
  • Occlusal relationships
  • Ease of patient cleaning
  • Properties of the material used
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15
Q

No attempt should be made to remove healthy tooth tissue. What are the exceptions to this? (3 points)

A
  • The material used for the restoration requires it
  • The margins of the cavity are in contact with another tooth surface
  • The margins of the cavity cross an occlusal contact
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16
Q

What are the principles of cavity design and preparation? (6 points)

A
  • Identify and remove carious enamel
  • Remove enamel to identify the maximal extent of the lesion at the ADJ + 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 lone and point angles

= Requirements of the restorative material

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17
Q

When looking at the principles of cavity preparation, what are the considerations for outline form modification? (3 points)

A
  • Enamel finishing
  • Occlusion
  • Requirements of the restorative material
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18
Q

When looking at the principles of cavity preparation, what are the considerations for internal design modification? ( 2 points)

A

Internal line and point angles
Requirements for the restorative material

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19
Q

What is a pint angle?

A

The junction of three surfaces of the crown of a tooth or the walls of a cavity

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20
Q

What is stress concentration?

A

The accumulation of stress in a body due to a sudden change in its geometry. When there is a sudden change in the geometry of the body due to cracks, sharp corners, holes and decrease in the cross section area, then there is an increase in the localised stress near these areas.

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21
Q

What considerations do you need to make in relation to final cavo-surface margins of a cavity? (4 points)

A
  • Remove enamel that will not be supported by the etch technique
  • Smooth CSMA and line angles
  • Ensure there are no excessively acute line angles transitions and that the outline form is smooth and rounded
  • Check for stress concentrators
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22
Q

What considerations do you need to make in relation to the final cavity design? (5 points)

A
  • where an existing restoration has been removed, ensure that no traces of restorative material remain
  • smooth external enamel sharp line or point angles
  • remove internal design sharp line or point angles
  • check for stress concentrators
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23
Q

Should you clean the cavity prior to placing a restoration?

A

yes, ensure it is free from debris generated during the preparation

24
Q

What is the first principle of cavity preparations and what is the process?

A

First principle: Accessing the caries

Process

  • Apply dental dam
  • Remove the overlying enamel with a high speed burr to gain access to the carious dentine
  • To do this you need to use a high speed handpiece to remove the enamel and access the carious dentine
  • Follow the caries from the ADJ
  • Do not extend into non-carious dentine
25
Q

What is the second principle of cavity preparation and what is this process? (8 points)

A

Second principle: Extent

Process:

  • Caries spread at ADJ determines outline form
  • Encloses extent of caries
  • Clear all caries at ADJ
  • Check staining at ADJ
  • Smooth enamel cavo-surface margins
  • Examine adjacent contat for caries
  • Avoid trauma to adjacent tooth
26
Q

What percentage of direct plastic restorations are replacement restorations?

A

80%

27
Q

Should you remove a previous restoration by cutting around the edges?

A
  • NEVER, you will increase the size of the cavity excessively
  • Start from the centre of the restoration and cut towards the edge of the cavity
28
Q

What is the process of accessing caries where there is a previous restoration? (3 points)

A
  • Use the high-speed bur to cut the restoration into pieces
  • Try to ‘chip out’ chunks of the restoration where possible
  • Remove all the restoration and any underlying base material
29
Q

What is the third principle of cavity preparation and what is the process for this? (5 points)

A

Third principle: remove dentinal caries

Process

  • Detected as brown stain or softened tissue when using a SHARP PROBE
  • Sound dentine should not yield under probing
  • Any sticking of the probe indicates residual cari ous dentine which should be removed
    • Do not probe uncavitated carious enamel
30
Q

When should stains be kept/removed from a cavity?

A

Should only be left if they are hard to probe

Stains must be removed from the ADJ

31
Q

Residual carious dentine must be removed first from the ADJ and last from the pulpal floor. How should caries be removed from here to reduce the risk of exposure of the pulp? (4 points)

A
  • Hand-held excavator
  • Round bur
  • Chemo-mechanical caries removal
  • Caries detector dyes may be helpful
32
Q

What is chemo-mechanical caries removal?

A

The removal of demineralised dentin from a tooth by applying a chemical gel or solution to soften it and then scraping away the diseased tissue manually.

33
Q

Where should caries be removed last and what should be used to remove these?

A
  • Should be removed last from the pulpal floor
  • Use the larges instrument which will conveniently work in the cavity:
  • Large round bur
  • Large hand-held excavator
  • Chemo-mechanical caries removal
  • Small burs and excavators will cut deeply more quickly - risk of pulp exposure
34
Q

What is a direct pulp cap?

A

Cap applied if some of the pulp has been exposed

35
Q

What is an indirect pulp cap?

A

Pulp cap applied if people have advanced tooth decay but where the tooth’s pulp has not yet been exposed tot he decay

36
Q

What is the fourth principle of cavity preparation and what is the process? (8 points)

A

Fourth principle: modifications

Once caries removal or removal of an existing restoration is complete:

  • Decide what restorative material to use
  • Modify the cavity preparation as appropriate:
  • Enamel margins
  • CSMA
  • Occlusion
  • Internal anatomy (stress concentrators)
  • Dentine quality
37
Q

What are the most commonly used restorative materials for direct restorations? (3 points)

A
  • Amalgam
  • Composite
  • RMGI
38
Q

What is the material of choice for direct restorations?

A

Composite

39
Q

What are the advantages of using composite? (7 points)

A
  • Aesthetic
  • Conservation of tooth tissue
  • Support of remaining tooth tissue
  • Adhesion/bonding
  • Command cure
  • Low thermal conductivity
  • Elimination of galvanism
40
Q

What is dental galvanism?

A

The production of galvanic current in the oral cavity due to the presence of 2 or more dissimilar metals in dental restorations that are bathed in saliva, or a single metal and 2 electrolytes (such as saliva and pulp tissue fluid); sometimes the current may be high enough to irritate the dental pulp and cause pain

41
Q

Does amalgam bond to dentine and enamel?

A

No, it is held into the cavity by retention and resistance form

42
Q

Does amalgam support the teeth?

A

No

43
Q

Why do you have to have good moisture control when using amalgam?

A

It does not like to be wet

44
Q

How do you prevent amalgam from fracturing?

A

Make sure it is an adequate bulk - at least 2mm deep

45
Q

Do you need to remove healthy tooth tissue when using amalgam?

A

Yes, for retention and resistance

46
Q

Which is more moisture and technique sensitive: amalgam or composite?

A

Composite

47
Q

What are features of a cavity prep for amalgam that prevent the restoration from being dislodged that are not needed for adhesive restorations? (4 points)

A
  • Undercuts
  • Dovetail
  • Key
  • Isthmus
48
Q

What is an undercut?

A

The portion of the surface of the tooth which is below the height of contour in relation to the path of insertion

49
Q

What is the height of contour of a tooth?

A

A line encircling the tooth and designating its greatest circumference at a selected position as determined by a dental surveyor

50
Q

What is a dovetail?

A

A widened portion of a cavity preparation usually established to increase the retention and resistance form

51
Q

What is the anatomical cavity design feature ‘isthmus’?

A

A narrow connection between 2 larger bodies or parts

52
Q

What is a bevel?

A

A bevel is described as an OBLIQUE CUT OF ENAMEL RODS WITHOUT INTERRUPTION OF ADJ

The angulation which is made by 2 surfaces of a prepared tooth which is other than 90 degrees. Bevels are given at various angles depending on the type of material used for restoration and the purpose the material serves

53
Q

What is a line angle?

A

The junction between 2 surfaces

54
Q

What is a point angle?

A

The junction between 3 surfaces of the crown of a tooth or the walls of a cavity

55
Q

What are the requirements of cavity margins for an amalgam restoration? (3 points)

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 cleansing
56
Q

What should the cavo-surface angle be for amalgam restorations?

A

Between 90-120 degrees

57
Q

What is configuration factor?

A

The number of bonded to unbonded surfaces in a tooth preparation

bds 2 (38 decks)

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