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3rd Yr- CSB- Extra-coronal restorations > Principles of Tooth Preparation > Flashcards

Principles of Tooth Preparation Flashcards

1
Q

What do we mean by indirect restoration

A

A restoration is a restoration which is not placed directly into the patients mouth

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2
Q

Are amalgam and composites a direct or indirect restoration?

A

Direct as they are placed directing into the mouth

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3
Q

Are crowns direct or indirect restorations?

A

Indirect

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4
Q

Why are crowns considered as indirect restoration

A

As their are multiple steps to make the restoration OUTSIDE the patients mouth before the restoration is finished and fitted for the patient

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5
Q

Give some examples of indirect restorations

A
  1. Crown
  2. Porcelain veneer
  3. Onlay
  4. Gold inlay
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6
Q

Why are indirect restorations important?

A
  1. Improve aesthetics
  2. Comfort
  3. Improved function
  4. Increased stability
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7
Q

What are some of the disadvantages of an indirect restorations

A
  1. Tooth needs more prep
  2. Takes more
  3. Patient needs to come in for more appointment
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8
Q

Why do we need to prepare teeth before placing an indirect restoration?

A

To create space
If there was no preparation then there would be inadequate room to place the materials needed to create an pathetic result

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9
Q

What do we NOT want to create when preparing a tooth

A

An undercut

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10
Q

What is an undercut

A

When the top of the tooth is wider than the bottom

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11
Q

Why do we not want to create an undercut?

A

As to results in over preparation and weakeaning of the tooth
This puts th teeth at higher risk of fracture and also increases risk of locking impression materials

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12
Q

What do we aim to create when preparing teeth?

A

A slight taper ensuring that the widest portion of the tooth is at the bottom and the narrowest at the top
This allows the restoration to slide on and off the tooth

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13
Q

As well as the tooth you are preparing what else do you need to keep in mind and why

A

The adjacent teeth and the proximal contacts for the tooth you are preparing
This is t ensure you have an easy path of entry

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14
Q

What are we aiming for when considering the proximal contacts of the tooth we are preparing?

A

Ideally the proximal contacts should we parallel to the path of insertion

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15
Q

List the 7 principles of preparation

A
  1. Preservation of tooth tissue
  2. Retention and resistance
  3. Structural durability of the restoration
  4. Material choice
  5. Marginal integrity and position
  6. Biological considerations
  7. Aesthetics
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16
Q

What balance do we need to maintain when preparing a tooth

A

Need to balance taking enough tooth tissue to allow space for the restoration while also relating as much as possible to protect the pulp and periodontium to reduce fracture risk

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17
Q

What can happen if a tooth is underprepared?

A
  1. Inadequate space for the restoration
  2. Need to use thinner restorative material increasing risk of fracture and perforation
  3. If thicker material is used conforming with the occlusal scheme may be difficult resulting gin a high spot on the restoration
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18
Q

What will happen if there is under preparing of the shoulder/ chamfer near the cervical margin of a tooth?

A

Material may chip or fracture exposing tooth tissue

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19
Q

what are the problems associated with over preparation

A
  1. Working closer to the pulp which can lead to loss of vitality
  2. Increased risk of tooth fracture
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20
Q

State the 2 Rs of preparation

A

Resistance

Retention

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21
Q

What is retention?

A

Preventing the removal of an extra corona restoration alone the path of insertion

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22
Q

What is resistance

A

Preventing dislodgment by lateral or apical forces under occlusal load

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23
Q

What are the properties of retention and resistance influenced by

A
  1. Taper
  2. Surface area
  3. Height
  4. Preparation design
  5. Cement selection
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24
Q

What is the relationship between taper and retention and resistance

A

The greater the taper the less retention and resistance

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25
Q

How can internal surfaces be used to offer retention

A

Opposing surfaces contribute and the parallel sided they are the greater the retention

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26
Q

What do we need to keep in mind when creating a taper

A

We need to be able to get the restoration in and out of the cavity

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27
Q

What is the acceptable degree of taper on clinic?

A

6-12 degrees

28
Q

What does a taper of 6-12 degrees mean?

A

It means there is a reduction of between 3 and 6 on the circumference of the tooth

29
Q

List the characteristics of an optimal taper

A
  1. Preserve tooth tissue
  2. Provide good resistance and retention
  3. Allow visible finish line
  4. Allow adequate seating of indirect restoration
  5. Aim for between 6-12 degrees
30
Q

On top of taper what else do we need to consider with retention and resistance

A

Surface area

height

31
Q

What is the relationship between surface area and resistance and retention

A

The greater the surface area the greater the retention and resistance

32
Q

What is the relationship between height, retention and resistance

A

The greater the height the greater the retention and resistance

33
Q

What preparation designs can we add to aid retention and resistance

A

Grooves

Boxes

34
Q

Where are grooves placed?

A

They are placed along the path of insertion and may change the arc of displacement

35
Q

Do grooves aid retention of resistance?

A

Resistance

36
Q

Name the 2 categories of cements we can choose from

A

Passive and aggressive

37
Q

What does the structure of the restoration need to be able to withstand?

A

Needs to be able to withstand:

  1. occlusal forces
  2. the oral environment and changes in temperature, pH
  3. Mastication of caretity of foods
38
Q

What are the problems associated with using thin porcelain?

A

It is prone to cracks and fracture

39
Q

What are the problems associated with using thin metal?

A

May perforate

40
Q

List some materials we can use to make an indirect restoration

A
  1. Metal ceramic
  2. Gold
  3. Non precious metal
  4. All ceramic
41
Q

Why does the marginal integrity and portion need to be accurate before you place an indirect restoration?

A

The more accurate a margin is the less exposed cement there is and this is good to avoid washing the cement away

42
Q

What can happen if a reduced to excessive dimension for the margin is used?

A

Can lead to failure in the materials such as cracks or fracture

43
Q

Name the 3 types of margin designs we can make

A
  1. Chamfer
  2. Shoulder
  3. Knife edge
44
Q

When is a shoulder used?

A

Often used for metal ceramic crowns

45
Q

What thickness do shoulders need?

A

At least 1.2mm

46
Q

When is a chamfer used?

A

For cold crowns

47
Q

What thickness do chamfers require?

A

Only require a reduction of 0.5mm

48
Q

What is a knife edged margin and when is it used?

A

It is a very fine edge which fades away and is sally made of metal

49
Q

When preparing palatal chamfer what isn’t a concern?

A

Aesthetics aren’t a concern as you cannot see the margin and so you can finish the margin sub gingival

50
Q

Where is the margin placed on the labial side of a tooth?

A

As aesthetics are key often placed level with the gingiva or slightly into the gingival sulcus

51
Q

What is the problem with placing a margin level with the gingiva and how do we overcome this problem?

A

Makes maintenance difficult and so impression may require a retraction cord

52
Q

Where is the ideal position to finish a margin?

A

On sound tooth tissue if feasible

53
Q

What are the problems with taking a margin sub gingival?

A

Can compromise gingival health

54
Q

What are the problems with the margin being inline with the gingiva

A

Can compromise aesthetics

55
Q

What are the problems with the margin being supra gingival

A

Can compromise aesthetics

56
Q

What do we NEED to preserve when preparing a tooth for an indirect restoration?

A

NEED to persevere the periodontium

57
Q

What can we do to persevere the periodontium ?

A
  1. Make sure the patient has good oral hygiene
  2. Make a supra gingival margin
  3. Make sure there’s sufficient marginal reduction (no overhangs or PRF)
58
Q

On top of the periodontium what else do we need to take of when placing an indirect restoration?

A

Need to protect the soft tissues and look at the biological width

59
Q

What is the biological width

A

The distance from the depth of the sulcus to the crest of alveolar bone

60
Q

What does the biological width include

A

The junctional epithelium and the connective tissue attachment

61
Q

What effect can impressions and indirect restoration placement have on the soft tissues

A

Can lead to persistent gingival inflammation

62
Q

How can we increase the height of the crown

A

With crown lengthening surgery

63
Q

What biological considerations must be make when preparing an indirect restoration?

A
  1. Preserve the periodontium
  2. Preserve the pulp
  3. Protect soft tissues
  4. Consider crown length
64
Q

How many teeth become non vital after crown prep

A

1 in 5

65
Q

How can we protect the pulp when carrying out preparations

A

Retain as much mineralised tissue as possible and avoid excessive reduction which approaches the pulp tissue

66
Q

List the 7 principles of preparation

A
  1. Preservation of tooth tissue
  2. Retention and resistance
  3. Structural durability of the restoration
  4. Material choice
  5. Marginal integrity and position
  6. Biological considerations
  7. Aesthetics

3rd Yr- CSB- Extra-coronal restorations (11 decks)

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