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Prof Abbott > Week 1- Cr-Co RPD's > Flashcards

Week 1- Cr-Co RPD's Flashcards

1
Q

What is required before surveying for RPD?

A
  • Check teeth
  • Take radiogrpahs
  • Take good primary impressions in alginate
  • Have model poured in yellow stone
  • Then, survey the denture, design it and fabricate special tray.
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2
Q

Why do you need to survey the cast?

A

Everything below the survey line is an undercut so retention will come from clasp placement in the undercut zone.

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3
Q

What is Kennedy Class II?

A

Unilateral edentulous area located posterior to the remaining teeth.

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4
Q

What is Kennedy Class I?

A

Bilateral edentulous areas

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5
Q

What are the classifications of RPD’s on support?

A
  • Tooth
  • Tissue
  • Tooth and tissue
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6
Q

What is Kennedy Class III?

A

Unilateral edentulous area with natural teeth anterior and posterior to it

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7
Q

What is Kennedy Class IV?

A

Single edentulous area located anterior to remaining teeth

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8
Q

What problems arise from Kennedy Class I?

A

Absence of abutment teeth distally created problems of support and retention.

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9
Q

What is the support for Kennedy Class II?

A

Both tooth and tissue supported

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10
Q

What is the support for Kennedy Class III?

A

Can be entirely tooth supported

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11
Q

What are the following Kennedy classes?

A
  • A. Class I
  • B. Class II
  • C. Class III
  • D. Class IV
  • E. Class II Mod I
  • F. Class II Mod I
  • G. Class II Mod II
  • H. Class III Mod II
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12
Q

What undercut measurement is suitable for Co-Cr clasps?

A

0.25mm

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13
Q

What undercut measurement is suitable for gold alloy clasps?

A

0.56mm

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14
Q

What undercut measurement is suitable for wrought wire clasps?

A

0.75mm

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15
Q

What is a potential issue with the following case?

A

Large undercut indicated by high survey line. Would result in unaesthetic clasp placement. Also cannot be used for Co-Cr partial.

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16
Q

What is the issue for making a Co-Cr denture in the following study model?

A

Lingual tilt of premolar prevents lower frame to be made

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17
Q

What are the clinical steps in making an RPD?

A
  1. Take alginate impressions for study models
  2. Survey and check undercut depths
  3. Design RPD
  4. Give pt estimation of cost
  5. Fabricate special tray
  6. Prepare rest seats etc. Then take secondary impressions
  7. Send to lab and request wax rim attached
  8. Jaw relation and shade selection
  9. Try in wax up then send for processing
  10. Insert RPD and recall in 7 days
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18
Q

What material should be used when taking secondary impressions for co-cr dentures?

A

PVS or Polyether (impregum)

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19
Q

What should be checked when trying in the RPD?

A

Engagement of clasps

Seating of occlusal rests

Check occlusion with articulating paper

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20
Q

What are the components of a co-cr denture?

A
  • Major connector
  • Minor connector
  • Occlusal rest seats
  • Retainers or clasps
  • Reciprocation
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21
Q

What happens if a co-cr clasp engages less than 0.25mm undercut?

A

Retention is unpredictable

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22
Q

What happens if a co-cr clasp engages more than 0.25mm undercut?

A

Likely that its proportional limit will be exceeded when the denture is seated or removed. Clasp would become permanently deformed and non-retentive

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23
Q

Where should the occlusally approaching clasp run?

A

From the side of the tooth with the least undercut to the side with the greatest undercut.

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24
Q

How long should a retentive clasp be in co-cr?

A

At least 15mm

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25
Q

What teeth should co-cr occlusally approaching clasps be used on?

A

Molar teeth

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26
Q

How long can gingivally-approaching clasps be made?

A

Can be made longer than 15mm

27
Q

What is the ADA code for mx metal partial denture?

28
Q

What is the ADA code for retainers?

29
Q

What is the ADA code for occlusal rests?

30
Q

What is the ADA code for teeth?

31
Q

When is a gingivally-approaching clasp contraindicated? Why?

A

If buccal sulcus is <4mm depth.

This does not have sufficient depth to accommodate this clasp type without much of the length of the clasp arm being placed too close to the gingival margin.

32
Q

What is a De Van clasp?

A

Gingivally approaching clasp running along the border of the saddle to engage the disto-buccal undercut of the abutment toot. Doesn’t enter sulcus area buccal to clasped tooth.

33
Q

What happens if a gingivally approaching clasp is placed in a tissue undercut greater than 1mm in depth within 3mm of the gingival margin?

A

Clasp will be relived extensively from the attached mucosa so that the denture can be inserted without traumatising the tissues. Such relief causes the arm of the clasp to be excessively prominent, resulting in possible irritation of buccal mucosa and trapping of food debris.

34
Q

What clasp is required for a distal extension saddle?

A

Retentive I-bar clasp

35
Q

Where should an I-bar clasp contact? Why?

A

Tip should contact most prominent part of buccal surface of abutment tooth mesially-distally.

This way, the tip of the clasp moves mesially and out of contact with the tooth when the distal extension saddle sinks under occlusal load.

36
Q

Where should clasps be located for a Kennedy II denture?

A

One clasp as close to the saddle as possible and the other as far posteriorly as possible on the other side of the arch.

37
Q

What are some supra-bulge clasps

38
Q

How should the bur be positioned when preparing cingulum rests?

A

Parallel to the tooth surface

39
Q

What are the basic parts of a clasp assembly?

A
  • Body of clasp
  • Minor connector
  • Reciprocal arm
  • Retentive arm
  • Retentive terminal
40
Q

What are the dimensions of an occlusal rest seat?

A

1.5mm deep and 2mm wide

41
Q

What needs to be checked in the exam before?

A

Charting teeth: resto status, prognosis, position and angulation of teeth.

Soft tissues: disease, contour, bony profiles (tori, tuberosities).

42
Q

What are the steps for a RPD?

A
  1. Assessment and Tx planning
  2. Primary impressions and interocclusal records. (diagnostic wax up and study models)
  3. Pouring of plaster casts, articulation, surveying, RPD design and construction of special tray.
  4. Tooth preparations and secondary impressions
  5. Pouring of stone casts and articulation
  6. Framework construction
  7. Try in and tooth shade selection
  8. Wax up
  9. Try in
  10. Flasking and investment. Finish and polishing.
  11. Delivery and adjustment of undercuts
  12. Recall
43
Q

What are requirements for major connectors?

A
  • Rigidity and force distribution
  • No interference to tongue
  • No substantial alteration to natural contour of lingual surface of md arch or palatal vault.
  • Cover no more tissue than necessary
  • Does not contribute to food trapping
  • Made from compatible alloy
  • Free from movable tissue
44
Q

What are the most common md major connectors?

A
  • Lingual bar
  • Lingual plate
45
Q

What are mx major connectors?

A
  • Palatal strap
  • A-P palatal strap
  • Palatal plate
  • U-shaped plate
  • Palatal bar
  • A-P bar
46
Q

What is the function of minor connectors?

A
  • Join components such as rests, clasps and saddles to major connector.
  • Contribute to functions of bracing and reciprocation (RPI system)
47
Q

What are some different types of minor connectors?

A
  • Saddle or gridwork
  • Proximal plate
  • Embrasure minor connector
48
Q

What are the characteristics of the 2 types of retentive frameworks?

A

Mesh type: flatter, potentially rigid, less retention of acrylic.

Lattice type: potentially superior retention for acrylic, might interfere with setting teeth if struts are tooth thick.

49
Q

What are the functions of rest seats?

A
  • Provide vertical stop
  • Transferring force to teeth and tissues
50
Q

How big should an occlusal rest be?

A

Should occupy ⅓ to ½ of the M-D diameter of the abutment and about ½ of the B-L width of the tooth measured from cusp to cusp.

51
Q

What are the methods to obtain support from anterior teeth?

A

Cast resto attached to lingual surface

Adding composite to lingual surface

52
Q

What are supra-bulge vs infra-bulge clasps?

A

Supra: occlusal approach e.g. circumferential

Infra: gingival approach e.g. bar type clasps

53
Q

Where is the retentive vs reciprocal arm of clasps positioned?

A

⅔ of retentive arm should be above the surveyed line

Reciprocal arm should never be below the surveyed line.

54
Q

What are features of infra-bulge clasps?

A
  • Approach arm never impinge on soft tissues
  • Approach arm must uniformly taper
  • Usually engage 0.25mm undercut
  • Approach arm should cross gingival margin at 90°
55
Q

What are contraindications for infra-bulge clasps?

A
  • Severe tissue or deep cervical tooth undercut exists
  • Shallow vestibule
  • Survey line close to occlusal surface
56
Q

Why is tooth surface modification sometimes required for dentures?

A

To produce good guiding planes and to alter the height of contour of abutment teeth.

57
Q

Where should indirect retainers be used?

A

Perpendicular to fulcrum line as far as practical

58
Q

What are indications for altered cast denture bases?

A
  • Distal extensions
  • Extensive edentulous spans
  • Any case where peripheries are distorted and need correction
59
Q

What design elements provide stability?

A
  • Reciprocations
  • Major connector
  • Minor connector
  • Indirect retainer
60
Q

What design elements provide support?

A
  • Denture base
  • Rests
61
Q

What design elements provide retention?

A

Direct retainers (clasps)

62
Q

What is the sequence of design for RPD?

A

Support > retention > stability

63
Q

What are issues with tooth colours clasps?

A

Thick, porous, fatigue

64
Q

When should a lingual plate be used instead of a lingual bar?

A
  • If space between free gingival margin and FOM is <7mm
  • Anterior teeth periodontally compromised
  • Few posterior teeth left (plate provides more tissue support)

Prof Abbott (8 decks)

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