RPD DESIGN 1: Saddles + Support Flashcards

(69 cards)

1
Q

List the main denture components (3)

A
  1. Saddle - an edentulous area
  2. Denture base - a connector (connects saddles)
  3. Flange - replacement tissue extending to the vestibular sulcus
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2
Q

What is the function of the Kennedy Classification?

A

Describes the number + distribution of saddle (edentulous) areas

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3
Q

Kennedy Class I

A

Bilateral free-end

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4
Q

Kennedy Class II

A

Unilateral free-end

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5
Q

Kennedy Class III

A

Unilateral bounded

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6
Q

Kennedy Class IV

A

Anterior bounded (crossing the midline)

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7
Q

What are options for resisting movements towards the tissue (2)

A
  1. Utility of hard tissue

2. Spread the load over large surface area

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8
Q

Function of

  1. Tooth support
  2. Mucosa support
A
  1. Tooth Support
    - Resists movement
    - Directs load through PDL of adjacent teeth
  2. Mucosa support
    - Needs large surface area = load distributed over a wide area
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9
Q

Craddock Class I

A

Tooth support

- Teeth provide a HARD tissue resistance to occlusal loading

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10
Q

Craddock Class II

A

Mucosa

- A LARGE coverage provides resistance to occlusal loading

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11
Q

Craddock Class III

A

Tooth + Mucosa

- A combination of HARD tissue and LARGE coverage when there are reduced numbers of teeth and large edentulous saddles

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12
Q

Tooth support/ tooth borne denture advantages (5)

A
  1. Transmits load via the PDL membrane
  2. Feels like the natural dentition
  3. Is more comfortable for the patient
  4. Protects the soft tissue from trauma
  5. Is likely to stay in close contact with its supporting structures over a period of time
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13
Q

Mucosal support disadvantage

A

Allows the denture base to move slightly

  • Possible damage to adjacent gingival margins
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14
Q

What teeth are the best for providing support?

A

MOLARS 2.7

- as they have the largest root area they can carry the greatest load

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15
Q

How much load can a healthy tooth carry?

A

A healthy tooth can carry its own load plus 1 and a half similar teeth

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16
Q

How is tooth support provided on the surface of adjacent abutment teeth?

A

Through metal alloy rests

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17
Q

Define rests

A

Provide support for the denture from vertical opposing forces

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18
Q

Why is incorporating rests into acrylic resin a problem?

A

Due to low base strength, placing a metal component potentially weakens the acrylic surrounding it

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19
Q

What are the 3 types of tooth rests?

A
  1. Occlusal
  2. Cingulum
  3. Incisal
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20
Q

Where are incisal rests most commonly used?

A

Lower anterior teeth due to aesthetic issues

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21
Q

Disadvantage of a small occlusal rest

A

If theres a small rest = small focus on load, which could have an adverse effect on tooth and tip it anteriorly

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22
Q

Advantage of a large occlusal rest

A

Recommended as this can direct the force down the long axis

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23
Q

Where are cingulum rests most commonly used?

A

Used mostly on maxillary and mandibular canines, but can be used on maxillary incisors

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24
Q

Advantages of cingulum rests (3)

A
  1. Aesthetically superior to incisal rests
  2. Apply stress at lower level - less rotation forces
  3. Less likely to break
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25
What are the 2 possible materials for the denture
1. Metal framework base (Co Cr) | 2. PMMA
26
Advantage of Metal framework base
Rigid and strong
27
Properties of PMMA
1. Flexible (not rigid) and poor strength | 2. Can be used when opposing forces are light e.g. complete denture
28
State advantages of rests (3)
1. Prevent movement of an RPD towards the mucosa 2. Assist in distribution of occlusal load 3. Prevent over-eruption of unopposed teeth
29
What is the exception to the rest placement when it comes to a free-end saddle?
A rest is NOT placed immediately adjacent to the saddle | Placed either mesially or distally
30
Rest placement for tooth supported bases?
The support should be on the tooth surface nearest to the base
31
Rest placement for tooth and mucosa supported bases?
The support should be on the tooth surface which is NOT next to the base
32
Why should occlusal rests NOT be placed in an occlusal centric stop?
The denture will be uncomfortable and the rest will interfere with the occlusion
33
Disadvantages of rest seats (3)
1. Loss of occlusal stop when denture is not worn 2. Destruction of tooth surface 3. Exposure of dentine
34
What is mucosal support dependent on?
As large an area possible of mucosa being covered
35
Why should the base not be placed within 3mm of the gingival margins?
As it will place pressure at the gingival margin
36
Function of a wire stop?
To ensure the most distal tooth in an every design does not drift posteriorly
37
What is the less harmful denture design called?
'Every' denture design | Less harmful mucosa borne denture
38
Why are mandibular mucosa supported dentures not recommended?
There is insufficient area to provide support
39
How does a hard tissue provide denture support?
Resists movement
40
How does large tissue coverage provide denture support?
Distributes load over a wide area
41
What Craddock classification is used for a free end saddle?
Class III | Tooth + Mucosa borne
42
What Craddock classification is generally used for bounded saddles?
Tooth borne
43
When would a mucosa borne denture be used
Only if there are insufficient teeth for a tooth borne denture
44
What Craddock classification is generally used for acrylic dentures?
Class II
45
What is used to make a denture tooth borne?
OCCLUSAL RESTS So there isn't loading onto the bone below Root area provides wide distribution of load
46
How does tooth support transmit load in a denture?
Periodontal membrane
47
How does mucosa support transmit load in a denture?
Has to cover as large an area as possible- reduction of the occlusal table
48
Why should slight movement of the denture base in mucosa borne dentures be avoided?
Possible damage to adjacent gingival margins
49
Give the problem with tooth extraction with reference to tooth support?
Periodontal area lost in extraction: Left with mucous membrane which has 4x less coverage than the periodontal area NOT AS GOOD FOR SUPPORT
50
What material is used for rests?
Metal
51
What material is used for acrylic resin rests?
Wrought stainless steel
52
When would a ledge usually be prepared for a rest?
In crown replacement
53
When would a ring rest be recommended? (2)
- Single standing teeth | - If the occlusion prevents occlusal rest
54
Why are ring rests usually avoided? (3)
1. The ring is above the survey line but below the occlusal surface 2. Could impact on occlusal surface 3. Unaesthetic
55
Where do incisal/ occlusal rests extended from?
Denture base framework
56
Disadvantages of incisal rests (3)
1. Poor aesthetics 2. May interfere with incisal occlusion 3. Not recommended on wear facets
57
Disadvantages of a cingulum rest
If theres no prominent cingulum present tooth prep is required
58
Advantages of a CoCr metal base framework (2)
1. Rigid and strong | 2. Single solid piece
59
How is the metal framework base produced?
By casting via a 'lost wax technique'
60
Disadvantages of a PMMA (acrylic resin) denture base? (2)
1. Flexible and poor strength | 2. Any load resisted by rests through the denture base place an internal stress on the base material
61
When could PMMA denture bases be used?
When opposing forces are light e.g. complete denture
62
Why are rests often placed on the occlusal surface of a tooth?
To direct occlusal forces along the long axis of the abutment teeth
63
How is the problem of compressibility of soft tissue with mucosa borne dentures overcome?
Base placed within 3mm of the gingival margins as this will place pressure at the tooth and tissue gingival attachment
64
Disadvantages of every partial design (2)
1. Can produce narrow and weak denture base areas | 2. Metal inserted into acrylic causes an inherent weakness in the denture base
65
Give the vertical displacement of tooth attachment within its socket (periodontium).
0.1mm
66
Give the compression of mucosal covering over alveolar bone (mucoperiosteum).
2mm
67
What is the problem with tooth and mucosa dentures?
Mucosa compresses more than the tooth within its periodontal attachment
68
How is the load on teeth involved in tooth and mucosa support reduced?
1. RPI | 2. Altered cast technique
69
When would bounded saddles not be tooth supported?
If the saddles are longer than 3 teeth