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Removable Partial Ddenture > RPD > Flashcards

RPD Flashcards

1
Q

Kennedy’s classification - what is class I?

A

Posterior bilateral free ended saddle

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2
Q

Kennedy’s classification - what is class II

A

Posterior unilateral free ended saddle

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3
Q

Kennedy’s classification - what is class III

A

Posterior unilateral bounded saddle

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4
Q

Kennedy’s classification - what is class IV

A

Anterior bounded saddle

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5
Q

What classes have modifications? What are these?

A

I, II, III
Number of extra edentulous area
e.g. missing UL1 and UL8,7,6 = class II mod I

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6
Q

What is an RPD?

A

A removable appliance which replaces 1 or more missing teeth, not the whole arch

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7
Q

Why can metal components be added to mucosa borne RPDs?

A

For strength and clasping

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8
Q

What attaches the metal framework of toothborne dentures to the fake teeth?

A

Acrylic or composite

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9
Q

What makes up mucosa borne dentures?

A

Metal framework

Acrylic forms the fitting surface and provides support in the saddle areas

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10
Q

When are RPDs only purely tooth borne?

A

For bounded saddles

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11
Q

When are toothborne dentures provided?

A

OH is good and stable

Abutment teeth - sound/good condition

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12
Q

What are the requirements of an RPD?

A 
Aesthetics
Comfort
Retention
Distribution of occlusal forces
Mastication
Space maintenance
OVD maintenance
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13
Q

Advantages of RPDs?

A

Non-invasive
Removable - plaque control
Acrylic ones - additions after bone resorption or tooth loss
Reversible - keep tx options open
Maintains OVD
Prevents tooth movement
Function
Aesthetics - replace the whole dento-alveolar complex
Effective permanent or transitional option

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14
Q

Disadvantages of RPD?

A 
Aesthetics - clasps
Pt difficulty adjusting
Intolerance - major connector
Poor distribution of occlusal forces
Tooth tissue loss
Plaque accumulation
Caries, PD, gingivitis, chronic atrophic candidosis 
Direct trauma to structures
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15
Q

Name a temporary denture

A

Spoon denture

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16
Q

Every denture features?

A

Borders 3mm from margins

Posterior wire stops to prevent posterior drift and loss of contact

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17
Q

List the stages of designing a denture

A
  1. Design saddle areas
  2. Support
  3. Retention
  4. Reciprocation
  5. Bracing
  6. Connectors
  7. Indirect retention
  8. Preparatory work
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18
Q

What is support?

A

Resistance to vertical forces down towards the mucosa

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19
Q

Options to gain support?

A

Support = Resistance to vertical forces directed towards the mucosa

Mucosa borne dentures
- Denture footprint being as large as possible to spread the load over a wide area

Tooth borne dentures

  • Occlusal, cingulum and incisal rests
  • With bounded saddles occlusal rests should be as close to the saddle as possible to ensure the load is transmitted to the tooth efficiently

Tooth/mucosa borne dentures

  • Free end saddles mean that the free end of the denture is mucosa borne
  • Free end saddles = rests should be as distant from the saddle as possible (at least the opposite side of the clasp tip). This is to improve support, indirect retention and cross arch bracing as the distant rest seat changes the axis of rotation.
  • Support is increased as when vertical forces are applied down towards the mucosa, the clasp disengages the undercut and moves towards the mucosa, preventing tooth displacement
  • Indirect retention is increased as when forces are applied away from the mucosa, the clasp tip engages the undercut and moves up the tooth bodily rather than causing the denture to rotate and displace
  • Cross arch bracing of free end saddles provided to prevent movement

Occlusal rests require rest seats to not affect the occlusion

Occlusal rests provide support, indirect retention, can improve occlusal contacts, prevent overeruption and direct the load down the long axis of the tooth

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20
Q

What do occlusal rests do?

A

Do not interfere with occlusion due to rest seats

Transmit force down the long axis of the tooth
Improve support, occlusal contacts
Can prevent overeruption

21
Q

How much tooth prep is needed for different occlusal rests?

A

CoCr 0.25mm
Gold 0.5mm
SS 0.75mm

22
Q

Where are occlusal rests located in bonded saddles (tooth borne dentures)?

A

As close to the bonded saddle area as possible

23
Q

Where are occlusal rests located in free ended saddles?

A

Further away from the free end saddle (e.g. mesial of the adjacent tooth) and opposite side of the clasp tip

24
Q

What is retention?

A

Resistance to movement of the RPD away from the mucosa (upwards)

25
Q

How to gain retention?

A

Physical forces - Saliva creating a peripheral seal

Muscular forces - Through occlusal surfaces of the teeth and polished surfaces of the denture

Mechanical retention: MODELS NEED TO BE ON A SURVEYOR:
- Path of insertion that differs to path of displacement:
When POI differs to POD, in bounded saddles 1 undercut is engaged and the other is blocked out
In free end saddles the undercut is engaged.
An undercut is the area under the surveyor line which indicates the maximum bulbosity of a tooth in the plane of the path of displacement.
POD is perpendicular to the occlusal plane and at a right angle to the occlusal plane.

Clasps

  • Provide direct retention by engaging the undercut relative to the path of displacement
  • Ensure the abutment teeth are sound and there is enough undercut for the clasp to engage
  • Clasps need reciprocation
  • Can be gingivally apporaching (I bar - RRPI system for free end saddles) or occlusally approaching
26
Q

Where is the survey line?

A

The most bulbous part of the tooth

27
Q

What is an undercut?

A

Area under the survey line. Undercut is relative to the path of displacement

28
Q

How to make the POI equal to POD?

A

Block out both undercuts adjacent to the bonded saddle

29
Q

Where do you put a clasp arm?

A

At the undercut to gain retention relative to upwards direction

30
Q

What are survey models used for?

A

Find undercuts relative to the POD and for clasping

Find areas of soft tissue that can be retentive

31
Q

Why reciprocate clasping?

A

As the clap arm moves up to the survey line it exerts a sideways load on the tooth that can cause tooth movement. This sideways load can be balanced to prevent tooth movement and make clasp more effective

32
Q

How to reciprocate clasping?

A

Put reciprocating arm on the opposite side of the tooth to maintain forces
- Difficult to do

Reciprocating arm with a guide plane:
- Create a flat surface on side of tooth (using a slow speed) and reciprocating arm at bottom of flat - reciprocating arm moves to the most bulbous part of the tooth to stop movement when the clasp arm is exerting it’s forces

Put reciprocating plate on side of tooth as part of connector
- Reciprocating plate stays in contact with the most bulbous part of the tooth (opposite side of the clasp) to prevent tooth movement

33
Q

What do reciprocating plates contact?

A

The most bulbous part of the tooth

34
Q

Define bracing

A

Resistance to sideways movement of the denture

35
Q

How to achieve bracing?

A

Usually provided by other components - connector, maximum saddle extensions and the reciprocating arms of clasps
In free end saddles = needs crossarch bracing to prevent movement. Achieved by occlusal rests being distal to the free end saddles.

36
Q

What are the types of connectors?

A

Major:

  • Connects saddle areas
  • Provides denture rigidity - Provides denture hygiene (should be 3mm away from the gingival margin where possible or above the survey line)
  • Mx connectors: Ring, skeletal or open design
  • Md connectors: Lingual bar/plate, sublingual bar, dental bar, kennedy bar

Minor:
- Join up components of the major connectors

37
Q

Define indirect retention.

Methods to achieve indirect retention?

A

= Resistance to rotation about the clasp axis by acting on the opposite side to the displacing force - prevents rocking e.g. by position of clasps, rests and type of connector

Gain indirect retention by:

  • Free end saddles, occlusal rests should be distant from the saddles so the clasp tip moves bodily along the long axis of the abutment tooth
  • Altered cast technique for free end saddles
38
Q

How to make POI = POD?

A

Block out both undercuts with PoP after surveying it = denture can be removed

39
Q

When to engage the undercut?

A

When missing molars (free end saddles) or class IV K.C

40
Q

What is the POD a right angle to?

A

The occlusal plane

41
Q

Name the maxillary connectors

A

Ring
Skeletal
Open

42
Q

Name the mandibular connectors

A

Lingual bar or plate
Sublingual bar
Dental bar
Kennedy bar

43
Q

How to write your RPD prescription?

A 
Draw design
Extent of saddles, no and size of teeth 
Position of occlusal rests
Clasp types on which teeth and corresponding reciprocation
Type of connectors and their extension
Colour of acrylic base
44
Q

What is the RPI system?

A

Provides indirect retention for free end saddles

  • Occlusal rests (distant from the saddle/opposite side of clasp)
  • Distal guide plane
  • Gingivally approaching I bar

Minor connector and distal plate provide reciprocation to the I-bar

45
Q

Indications for acrylic RPDs?

A

Remaining teeth have a poor prognosis - can have additions
Young patient/pagets to allow growth
Where bone loss is occuring
When few teeth remain
Temporary denture
Where there is inadequate support from the remaining teeth for a tooth-borne denture (when teeth are not used for support)
Cheaper, made quicker

BUT weak and bulky, can cause soft tissue damage

46
Q

Indications for CoCr RPDs?

A

When sufficient, healthy, tooth support can be obtained

Thinner base so more acceptable to the patient
More secure as retained by clasps
Less extensive soft tissue coverage
Strong and transmit load well

BUT cannot be modified

47
Q

Shortened dental arch?

A

Less than 20 teeth
9-10 pairs of occluding teeth
Adequate function achieved with reduced dentition

48
Q

Disadvantages of a shortened dental arch?

A

Increased risk of anterior tooth wear

RPD provision in future may be more challenging due to fewer teeth, tongue space and controlling a larger denture

49
Q

Define a functional dentition

A

The retention throughout life of a functional aesthetic dentition of no less than 20 teeth and not requiring a prosthesis

Removable Partial Ddenture (4 decks)

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