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BDS2 RPD > RPD - Saddles and Supports > Flashcards

RPD - Saddles and Supports Flashcards

1
Q

What is meant by the term ‘saddle’?

A
  • An edentulous area
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2
Q

What is meant by the word ‘flange’?

A
  • Replacement tissue extending to the vestibular sulcus
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3
Q

What is Kennedy Classification?

A
  • An anatomical classification that describes the number and distribution of saddle (edentulous) areas
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4
Q

What defines the Kennedy classification of a mouth?

A
  • The most posterior saddle in the mouth
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5
Q

What is Kennedy class 1?

A
  • Bilateral free-end saddle
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6
Q

What is Kennedy class 2?

A
  • Unilateral free-end saddle
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7
Q

What is Kennedy class 3?

A
  • Unilateral bounded saddle
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8
Q

What is Kennedy class IV?

A
  • Anterior bounded saddle (crossing the midline)
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9
Q

What is each additional saddle area referred to as in Kennedy classification?

A
  • A modification
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10
Q

Which Kennedy class cannot be modified?

A

Kennedy Class 4

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11
Q

What is meant by ‘support’ in relation to RPD’s?

A
  • A term used to describe the RESISTANCE of a denture to OCCLSALY DIRECTED load
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12
Q

What are the options for resisting movement towards the tissues in the support of RPD’s? (2 points)

A
  • Utility of hard tissues

- Spread the load over a large surface area

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13
Q

Which classification is based on the support for a RPD?

A
  • Craddock’s classification
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14
Q

What is Craddock’s class 1?

A

Tooth - Teeth provide a HARD tissue resistance to occlusal loading

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15
Q

What is Craddock’s class 2?

A

Mucosa - A LARGE coverage provides resistance to occlusal loading

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16
Q

What is Craddock’s class 3?

A

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

  • You cannot avoid mucosal loading when you have a free end saddle
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17
Q

How do tooth supported RPD’s transmit load?

A
  • Via the periodontal membrane
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18
Q

What does tooth support of an RPD allow?

A
  • Allows the supported denture base to feel like the natural dentition
  • It is more comfortable to the patient
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19
Q

What do tooth supported RPD’s support the soft tissue from?

A
  • Protects the soft tissue from trauma
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20
Q

What must mucosal supported RPD’s cover?

A
  • As large an area as possible

- Reduction of the occlusal table

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21
Q

What does mucosal supported RPD’s allow which may cause possible damage to adjacent gingival margins?

A
  • Allows the denture base to move slightly
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22
Q

Which teeth are the best for providing support for a RPD?

A
  • Those with the largest root area depending on the health of the periodontal attachment
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23
Q

How many times more is the periodontal membrane for support compared to the mucosal coverage for a lost tooth?

A

4 times

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24
Q

How much of a load can a healthy tooth carry?

A
  • Potentially carry its own load plus one and a half similar teeth
25
Q

What should you think about when thinking about whether a tooth is suitable for support?

A
  • Think of the root to crown ratio
26
Q

What should the rest on the teeth supporting RPD’s transfer the load through?

A
  • The long axis of the tooth
27
Q

What are ‘rests’ in tooth support of RPD’s?

A
  • The components which provide SUPPORT for the denture from vertical opposing forces
28
Q

Rests are describes by that part of the tooth they contact. What are the 3 types of rest?

A
  • Cingulum, incisal, occlusal
29
Q

What are ‘rests’ made of?

A
  • Cast or wrought metal

- Rests are best used as part of a CAST METAL denture framework

30
Q

Can rests be incorporated into acrylic bases?

A
  • Yes, but this is very rare
  • Incorporating rests into acrylic resin presents a problem due to low base strength. Placing a metal component potentially weakens the acrylic surrounding it
31
Q

Theoretically all rests should be on a rest seat. Why does this not always happen?

A
  • Doesn’t usually happen due to the ethics of removing healthy tooth tissue
32
Q

Why are small occlusal rests not recommended?

A
  • As they apply large forces per unit area
33
Q

Why are large occlusal rests recommended?

A
  • As this can direct forces down the long axis
  • Need to be big enough to ensure the loading goes onto the long axis of the tooth
  • Think about size of rest coming to at least the midline of the tooth - this is ideal
34
Q

Where are incisal rests mostly used?

A
  • On lower anterior teeth

- This is due to a poor aesthetic appearance

35
Q

What may incisal rests interfere with?

A
  • May interfere with incisal occlusion
36
Q

Where are incisal rests not recommended?

A
  • On wear facets
37
Q

Where are cingulum rests mostly used?

A
  • On maxillary and mandibular canines, can be used on maxillary incisors and laterals
38
Q

What are 2 properties of metal framework bases (CoCr)?

A
  • Rigid and strong
39
Q

What are rests like on a metal framework base?

A
  • ALL rests are integral to the base connected to the major connect directly or by miner connects
40
Q

How are metal framework bases produced?

A
  • By casting using a ‘lost wax technique’ - more extensive technique
41
Q

What are 2 properties of acrylic resin dentures?

A
  • Flexible and poor strength
42
Q

How are rests incorporated into acrylic resin dentures?

A
  • Incorporated mechanically into the base
43
Q

What does any load resisted by rests on an acrylic denture cause?

A
  • They place an external stress on the base material

- Rests for support within an acrylic base are the exception rather than the rule

44
Q

What are the 6 main things rests on RPD’s do?

A
  1. Prevent movement of an RPD towards the mucosa
  2. Assist in distribution of occlusal load
  3. Direct retentive elements to work in a planned manner
  4. Prevent over-eruption of unopposed teeth
  5. Provide bracing on anterior teeth
  6. Determine the axis of rotation for free-end saddle RPD’s
45
Q

What is the purpose of a rest?

A
  • To support the denture against VERTICAL load - that is directed towards the tissue
46
Q

Why are rests often pla c ed on the occlusal surface of a tooth?

A
  • Since this will direct occlusal forced down the long axis (root) of the abutment teeth
47
Q

Where is the default position to place a rest for a bounded saddle?

A
  • IMMEDIATLY adjacent to the saddle
  • Additional rests may be incorporated
  • The default position may have to be changed depending on the opposing dentition
48
Q

Where is a rest places for a free end saddle?

A
  • NOT immediately adjacent to the saddle
49
Q

Where should rests be places for tooth supported bases?

A
  • The support should be on the tooth surface nearest to the base
50
Q

For tooth and mucosa supported bases, where should the rests be positioned?

A
  • The support should be on the tooth surface which is not next to the base
51
Q

Why should you avoid placing a rest in an occlusal centric stop?

A
  • The denture will be uncomfortable and the rest will interfere with the occlusion
52
Q

What are centric stops?

A
  • The stable points of contact between occluded maxillary and mandibular teeth
53
Q

Rest seat can be prepared but there are downsides to this. What are 3 of the consequences?

A
  • Loss of occlusal stop when denture is not worn
  • Destruction of tooth surface
  • Exposure of dentine
54
Q

What is mucosal support (Craddock’s class 2&3) dependent on?

A
  • Dependent upon as large an area as possible of mucosa being covered
  • However since soft tissue is compressible it is inadvisable to place the base within 3mm of where the gingival margins are, this will place pressure at the gingival margin
55
Q

What is the ‘every’ partial denture design?

A

A mucosa borne denture which restores the dental arch; with contact points between the denture and the abutment teeth

  • To ensure the most distal tooth does not drift posteriorly a wire stop is incorporated
56
Q

In an ‘every’ partial denture are the gingival margins covered by the denture design?

A
  • No
57
Q

Bounded saddle cases are tooth supported unless the saddles are what?

A
  • Longer than 3 teeth
58
Q

What are ‘every’ design dentures?

A
  • They are less harmful mucosa-borne dentures
59
Q

Why are mandibular mucosa supported dentures generally not recommended?

A
  • As there is insufficient area to provide support unless this denture is being used as a training appliance in preparation for a complete denture or overdenture

BDS2 RPD (13 decks)

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