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3rd yr- CSB- Partial dentures > A system of design for cobalt chrome dentures > Flashcards

A system of design for cobalt chrome dentures Flashcards

1
Q

State the 4 principles for cobalt chrome dentures

A
  1. Avoid gingival coverage
  2. Provide a denture that has good support
  3. Make sure the connector is rigid to distribute evenly the loads the denture will endure
  4. Keep it simple
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2
Q

Why is it important that we avoid gingival coverage when designing a cobalt chrome denture

A

As it will promote plaque accumulation and can encourage periodontal disease

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3
Q

Why do we need to make sure the denture has good support?

A

To ensure it does not sink and lead to gum stripping

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4
Q

List the 8 steps to design cobalt chrome dentures

A
  1. Saddles
  2. Support
  3. Retention
  4. Bracing/reciprocation
  5. Indirect retention
  6. Guide planes
  7. Connectors
  8. Review principles of design
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5
Q

What are saddles?

A

Edentulous areas in the mouth

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6
Q

When designing our saddle what do we need to consider?

A

Do we need to replace every tooth?

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7
Q

Do we need to replace every tooth?

A

No we need a reason for each tooth we put on the denture

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8
Q

What might be a reason to replace a tooth

A
  1. Aesthetics
  2. Masticatory efficiency
  3. Prevent drifting/ tilting/ over eruption
  4. Phonetics
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9
Q

What might a reason we avoid replacing a tooth

A
  1. Plaque trap
  2. Trauma
  3. Patient tolerance
  4. Cost
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10
Q

According to kaisers research when can masticatory efficiency be reduced?

A

Below ten occluding units (10 teeth in each arch)

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11
Q

Are dentures as good at chewing as natural teeth?

A

No

Implants are a lot better but more expensive

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12
Q

Ultimately what/ who decides if the masticatory efficiency of a patient has been reduced?

A

The patient

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13
Q

What is phonetics referring to?

A

Speech

ie patient asking for dentures to improve their speech

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14
Q

What is the major disadvantage for replacing teeth

A

Plaque retention which can lead to:

  1. Periodontal disease
  2. Caries
  3. Fungal infections
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15
Q

Which structures in the mouth can be traumatised due to dentures?

A
  1. Soft tissues

2. Pulp (fixed bridge work can lead to plural necrosis)

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16
Q

How can patient tolerance become a disadvantage for replacing teeth?

A
  1. Gag reflex

2. Psychology and patient expectations

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17
Q

Where do saddles usually extend to?

A

Saddles usually extend to the full extent of the denture bearing area

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18
Q

Describe the position of the saddle in the lower arch

A

Saddles extend to the functional depth of the sulcus and as far back as the pear shaped pad in the lower arch

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19
Q

Describe the position of the saddle in the upper arch

A

Saddles extend to the functional depth of the sulcus and as far back as the hamualar notch in the upper arch

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20
Q

Why do saddles usually extend to the full extend of the denture bearing area?

A

To distribute the vertical and lateral load over as greater area as possible and so decrease the pressure on the underlying mucosa

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21
Q

What is support on a denture usually provided by?

A

Rest seats

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22
Q

Where can rest seats be placed?

A
  1. Occlusal

2. Cingulum

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23
Q

For a bounded saddle where do we usually place the support?

A

On the nearest surface of each abutment tooth

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24
Q

For a free end saddle where do we usually place the support?

A

On the medial side of the abutment tooth

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25
Q

Why do we look for support on the medial side of the abutment tooth for a free end saddle?

A

As this reduces the torque on the abutment tooth

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26
Q

When placing a rest what do we NEED to check?

A

Need to check occlusion to make sure the position of the rest seats are possible and don’t interfere with the patients bite

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27
Q

What might we need to do if the patients occlusion is tight?

A

May need to provide a deep rest seat preparation
OR
May move the occlusal rest to a convenient nearby position which is
free of the occlusion.

28
Q

How do we asses each rest seat position?

A

By using an articulated study cast

29
Q

Do we always need a rest seat?

A

NO remember keep your design simple

30
Q

How do clasps work?

A

They engage the undercut to gain retention

31
Q

What is the undercut

A

It is the area below the survey line

32
Q

What is the survey line

A

The line of maximum bulbosity on the tooth

33
Q

What determines the size of the retentive force on a tooth?

A

The horizontal depth of the undercut

34
Q

How can clasps approach the tooth?

A

Occlusally
OR
Gingivally

35
Q

Name the two types of occlusal approaching clasps

A
  1. Simple 3 arm clasp

2. Ring clasp

36
Q

Name the 3 types of gingival approaching clasps

A
  1. I bar
  2. T bar
  3. L bar
37
Q

What should each saddle ideally have on a bounded saddles

A

Should ideally have a clasp on at least one abutment tooth unless aesthetics dictate

38
Q

What do we need to look at when thinking about retention on a bounded saddles

A

For each saddle, look, initially for retention on both abutment teeth

39
Q

What do we need to look at when thinking about retention on a free ended saddles

A

Usually look for retention on the abutment tooth of the saddle

40
Q

What can we do if we haven’t got an undercut where we want it

A

We can ad composite on natural teeth to gain undercut

41
Q

What can we do if we have too mcc undercut on a tooth?

A

We can re shape the tooth by cutting a guide plane or adding composure then re shaping

42
Q

When thinking about bracing/ reciprocation clasps what should we check for?

A

Check for resistance to lateral and anterior/posteriro movement

43
Q

How do we check for resistance to lateral and posterior/anterior movement

A

Engage flanges to the functional depth of each sulcus

44
Q

Where do we need to add reciprocative clasps

A

Opposite to each retentive clasp arm

45
Q

What is indirect retention

A

It is resistance to rotational displacement in a tooth and mucosa borne denture

46
Q

What happens when sticky food pulls a free end saddle away from the mucosa

A

The denture can rotate around the clasp

47
Q

How is indirect retention is usually achieved?

A

By placing an occlusal rest on a tooth anterior to the clasp

48
Q

Where is the best place t put indirect retention clasps

A

As far from the clasp axis as possible

49
Q

Why are guide planes important

A
  1. For a single path of insertion
  2. For reciprocation
  3. For indirect retention
  4. To create a path of insertion radically different from the path of displacement
  5. To use with the RPI clasp system
50
Q

What does the horizontal depth of an undercut determine?

A

The size of the retentive force

51
Q

What do we achieve if we place guide planes across the teeth in an arch that are parallel to each other

A

We effectively create one path of insertion for the denture

52
Q

What is the benefit of creating one path of insertion for the denture

A

Increases retention as the denture can only be removed if it is taken out in a certain direction

53
Q

Describe connectors

A

They are rigid

54
Q

Describe connectors we can use in the upper arch

A

Need to Clear the gingival margin by 3mm

55
Q

Give examples of where we can place connectors in the upper arch

A
  1. Anterior palatal bar
  2. Mid palatal bar
  3. Posterior palatal bar
56
Q

Name some connectors we can use in the upper arch

A
  1. Horse shoe
  2. Palatal plate
  3. Ring
57
Q

Give examples connectors we can place in the lower arch

A
  1. Lingual bar
  2. Sublingual bar
  3. Lingual plate
  4. Dental bar
  5. Buccal bar
58
Q

Name the most common connector for the lower arch

A

Lingual bar

59
Q

How much depth do we in the lingual sulcus need to be able to place a lingual bar

A

6mm

60
Q

Where does the sublingual bar sit?

A

At the bottom of the lingual sulcus

61
Q

What does a sublingual bar need

A

Requires a special accurate impression of the lingual sulcus as the depth of the lingual sulcus changes as we move our mouth

62
Q

How much depth do we in the lingual sulcus need to be able to place a sublingual bar

A

5mm

63
Q

What is different about a lingual plate from the other lower arch connectors

A

You don’t need 3mm clearance

64
Q

Where does a dental bar connector sit?

A

Entirely on the teeth

65
Q

What do we need to be able to place a dental bar

A

Long clinical crown needed

3rd yr- CSB- Partial dentures (5 decks)

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