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2 - Operative Dentistry > Cavity Preparation > Flashcards

Cavity Preparation Flashcards

1
Q

What determines cavity design?

A

Structure and properties of dental tissues
The diseases (caries, periodontal disease, erosion)
Properties of restorative materials

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2
Q

Where can the position of the caries be?

on the tooth

A

Pits and fissures
Approximal (posterior/anterior)
Smooth surface
Root (periodontal disease)

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3
Q

When should intervention occur?

A

When the lesion is cavitated
When the patient cannot access lesion for prevention

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4
Q

When is intervention considered?

(Not yet definite)

A

Lesion is into dentine radiographically
Lesion is causing pulpitis
Lesion is unaesthetic

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5
Q

What should be considered when operating on enamel?

A

Enamel is brittle, it should not be left under occlusal load or unsupported
Cuts should be made across enamel prisms as end cut prisms are more supported during bonding process

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6
Q

What are the factors that cause caries?

A

Bacteria
Tooth surface
Sugar (fermentable carbohydrate)
Time

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7
Q

What are the qualities of dentine that must be assessed?

A

Primary, tertiary or secondary
Intra/inter/peri tubular dentine
Diameter/ dentistry
Contents/ mineralisation

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8
Q

What are the principles of preparation driven by?

A

Caries removed
Necessary finishing required for maximising adhesion, occlusal relationships, ease of patient cleaning and properties of the materials used

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9
Q

When should you remove healthy tissue?

A

The restorative material requires it
Margins of cavity are in contact with another tooth surface
Margins of cavity cross an occlusal contact

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10
Q

How should enamel be removed?

A

Remove to identify the maximal extent of the lesion at the ADJ and smooth the enamel margins

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11
Q

What is the cavo-surface margins?

A

The junction of the cavity and the tooth

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12
Q

After creating the cavity, what should be ensured?

A

Remove enamel that will not be supported by etch technique
Smooth cavo surface margins and line angles
Ensure the outlines of the cavity are smooth and rounded (no line angle transitions)
Check for stress concentrators

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13
Q

What is stress concentration?

A

When the material is subjected to a load, a stress concentration develops around cavity

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14
Q

What should be checked in the final cavity design?

A

Ensure no traces of previous restorative material remain
Smooth eternal enamel sharp line or point angles
Create appropriate cavo-surface margin angle
Remove internal dentinal sharp line or point angles
Check for stress concentrators

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15
Q

Why should the cavity be cleaned?

A

To ensure it is free from debris generated during preparation

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16
Q

How should you access caries? (1st principle)

A

Apply dam
Remove over-lying enamel with high-speed burr
Follow caries at ADJ
Do not extend into non-carious areas

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17
Q

How should you extent the cavity? (2nd principle)

A

Spread of caries at ADJ determine outline form
Clear all caries at ADJ
Check staining at ADJ
Smooth enamel cavo-surface margins
Examine adjacent contact tooth for caries and avoid trauma to adjacent tooth

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18
Q

What % of direct plastic restorations are replacement restorations? (Replacing amalgam)

A

80%

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19
Q

How is a previous restoration removed? (What burr)

A

High speed burr

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20
Q

What should you never do when removing a previous restoration?

A

Never remove a restoration by cutting around the edges - thus increasing the size of the cavity excessively.
Start from the centre of the restoration and cut towards the edge of the cavity.

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21
Q

How should the previous restoration be removed?

A

Cut restorations into pieces with the high speed burr
Try to chip out chunks where possible

22
Q

How should you remove dentinal caries? (3rd principle)

A

Stain should be left if hard to probe
Stain musts be removed from the ADJ
Residual carious dentine must be removed first from the ADJ and last from the pulpal floor
Caries should be removed using a
-hand-held excavator
-round bur
-chemo-mechanical methods

23
Q

What are the qualities of carious dentine?

A

Detected as a brown stain or softened tissue when using a sharp probe
Sound dentine should not yield under probing
Any sticking of the probe indicates residual carious dentine which should be removed

24
Q

What can be helpful in identifying carious dentine?

A

Caries detector dyes

25
Q

Why should large instruments be used when working on the pulpal floor?

A

Small burrs and excavators will cut deeply more quickly - risk of pulp exposure

26
Q

How can a exposed pulp have pulp therapy?

A

Direct and indirect pulp cap

27
Q

How should you modify a cavity? (4th principle)

A

Decide what restorative material to use
Modify the cavity preparation as appropriate relative to material
-enamel margins
-cavo surface margin angles
-occlusion
-internal anatomy
-dentine quality

28
Q

What are the most common materials for restorations?

A

Amalgam
Composite

29
Q

Why can amalgam fail?

A

Due to Micro-leakage

30
Q

What are advantages of composite?

A

Aesthetic
Conservation of tooth tissue
Support for remaining tissue
Adhesive/bonding
Cure on command
Low thermal conductivity
Elimination of galvanism (electrical currents)

31
Q

What are the disadvantages of amalgam?

A

Does not bond to enamel or dentine
Does not support the tooth
Cut dentine may require sealed resin layer
Need to remove healthy tissue
Not tooth coloured

32
Q

What are the advantages of amalgam?

A

Strong under occlusal load
Less moisture and technique sensitive

33
Q

How is amalgam held into the cavity?

A

Retention and resistance form

34
Q

What is the retention and resistance form?

A
  • Retention form stops fillings or crowns from popping out (dislodging in direction opposite to it’s insertion)
  • Resistance form stops them from dislodging from masticatory forces (dislodging in any direction except opposite to it’s insertion)

Design features such as undercuts, dovetail, key, isthmus
Not essential for adhesive restoration (composite)

35
Q

How should the design cut for amalgam be?

A

Internal dimensions of cavity should be greater than access to it
/ \

36
Q

For retention to increase, what is required for adhesive restorations?

A

Cavo-surface angles should be adjusted to increase bonding area and ensure no unsupported enamel
No under-cuts necessary

37
Q

What is a bevel?

A

any abrupt incline between two surfaces of a prepared tooth

38
Q

What is the line angle?

A

junction between two tooth surfaces

39
Q

What is the point angle?

A

The angle formed at the junction between 3 tooth surfaces

40
Q

What should the features of the cavity margins be for amalgam?

A

All cavity margins should be caries free and accessible for cleaning
Free of contact with adjacent tooth
Designed for max strength and mini leakage

41
Q

How should the cavity margin be designed for max strength and what is the best angle figures?

A

Bevel to align orientation with prisms for COMPOSITE (end cut prisms is best approach)

Cavo-surface angle is between 90-120 degrees for AMALGAM

For both avoid inappropriate CSMA or unsupported enamel

42
Q

Define CSMA, AMA, USE

A

CSMA = cavo-surface margin angle
AMA = amalgam margin angle
USE = enamel prisms unsupported by underlying dentine

43
Q

What can USE cause?

A

Fractures leading to plaque traps causing secondary caries

44
Q

What can caries left at the ADJ cause?

A

USE and early breakdown of restoration margin if microleakage occurs

45
Q

What is the configuration factor?

A

Refers to number of bonded surfaces in an adhesive dental restorations

46
Q

What does a high configuration factor mean?

A

Increased polymerisation contraction stress

47
Q

Why does a high configuration occur?

A

Etch/bond is stronger than interstitial enamel strength

48
Q

How to clean a cavity?

A

Wash the cavity with a mixture of air and water to remove loose debris, rinse with chlorhexidine and remoce
Leave surface moist

49
Q

What are important things to remember?

A

Don’t always remove ALL the caries
Protect airway and pulp
Decide on material after caries removal
Remove enamel to discover maximal extent of lesion and smooth enamel margins
Remove dentinal caries from ADJ to pulp

50
Q

Which of the following effects of etching will improve retention of composite restorations?

A

the increase in surface area

2 - Operative Dentistry (10 decks)

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