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Removable Partial Dentures 2nd year > Dalhousie RPD Manual > Flashcards

Dalhousie RPD Manual Flashcards

1
Q

What is the definition of a retainer?

A

Component of a rpd that provides both support and retention

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2
Q

4 treatment objectives of an rpd?

A
  1. Preserve remaining teeth and supporting structures
  2. Restore esthetician and phonetics
  3. Restore and or improve mastication
  4. Restore health, comfort, and quality of life
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3
Q

Guiding planes are most effective when? (5 points)

A
  1. Are parallel
  2. Include more than one common axial surface
  3. Are directly opposed by another guiding plane
  4. Are placed on several teeth
  5. Cover large surface area (long and/or broad)
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4
Q

How long should guiding planes be?

A

At least 1/2 to 1/3 of of the axial height (minimum 2mm in height)

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5
Q

What are the 3 effects of guiding planes on retention and stability?

A
  1. Guiding planes maintain retention
  2. Guiding planes minimize the need for retention (frictional retention minimizes need for direct retainers)
  3. Guiding planes stabilize teeth (most effective in class 3)
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6
Q

In what cases would we want longer vs shorter guiding planes? Why?

A

Class 3 longer guiding planes

Class 1 and 2 shorter guiding planes (because loading of denture base causes rotation of rest seat. Shorter guiding planes allow rotation into the gingival relief area and prevent the immediate torquing of the tooth)

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7
Q

2 ways of modifying height of contours and why ?

A
  1. Lowering height of contour
    - eliminates tooth interferences where rigid elements are placed
    - improves esthetics (retentive arms are more gingival)
  2. Raising height of contours
    - only time is when there is no retentive undercut present or when it is too close to fgm
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8
Q

3 ways of raising height of contour?

A
  1. Preparing retentive undercut (inferior border of prep at least 1mm from Gingiva)
  2. Place composite resin
  3. Combination of preparing undercut and placing composite resin
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9
Q

6 functions of rests?

A
  1. Direct forces along long axis of tooth
  2. Prevent denture base from moving cervically and impinging gingival tissues
  3. Maintain planned clasp-tooth relationship
  4. Prevent extrusion of abutment teeth
  5. Provide positive reference seats in rebasing and/or impression procedures
  6. To serve as an indirect retainer by preventing rotation of partial denture (class 1 or 2 only)
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10
Q

What is the shape of an occlusal rest seat?

A

Rounded triangular shape

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11
Q

How wide should an occlusal rest seat be?

A

Approximately 1/3 buccal-lingual width

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12
Q

How much bulk should be present for an occlusal rest?

A

1-1.5 mm minimum to prevent fracture

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13
Q

What should the angle be between the rest and minor connector?

A

Less than 90 degrees which helps direct occlusal forces along long axis of tooth.

SHOULD BE A POSITIVE REST SEAT (less than 90mdegrees). Explorer won’t slide off top of rest seat

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14
Q

What occurs if the rest seat is not positive?

A

Occlusal forces are not directed along long axis of tooth and permits movement of the clasp away from the tooth and orthodontic movement of the tooth

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15
Q

What shape should the floor of the rest seat be? Why?

A

Concave or spoon shaped to prevent horizontal stresses and torque on the abutment tooth

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16
Q

Why should a cingulum rest seat not be prepared too high or low?

A

Too high - much of lingual surface will need to be reduced to obtain sufficient width. May also interfere with occlusion

Too low - much of cingulum will need to be reduced to obtain sufficient width, enamel is also thinner in this area and could result in dentinal exposure

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17
Q

Why is a lingual rest always preferred to an incisal rest?

A

Because a lingual rest is placed near the centre of the tooth and is less likely to tip the tooth

18
Q

What are 3 functions of a major connector?

A
  1. Unification
  2. Stress distribution
  3. Cross-arch stabilization
19
Q

What is a more rigid alloy? (Chrome-cobalt vs. Gold; cast vs. Wrought metal)

A

Chrome-cobalt > gold

Cast>wrought metal

20
Q

4 requirements of a major connector?

A
  1. Rigidity
  2. Non-interfering with soft tissues
  3. Food impaction
  4. Unobtrusive
21
Q

What is the shape, size, and position of a lingual bar?

A

Shape
- flat on tissue side and convex on tongue side (like 1/2 a pair shape)
Size
- occlusal-gingival width (4-6mm)
- thickness (1.5-2mm)
Position
- inferior border should be as low as the lingual Frenum
- superior border should be 1.5-2mm or more below fgm
- in distal extension cases, when alveolar ridge bone loss occurs, lingual bar may impinge on soft tissues, to prevent this a wax spacer (1 thickness of 30 gauge wax) should be placed underneath when it is being waxed for casting

22
Q

What are 3 reasons why a lingual bar could not be used?

A
  1. High floor of the mouth
  2. Large lingual frenum
  3. Lingual Tori
23
Q

In what case would we use a labial bar on the mandible?

A

When there is extreme lingual inclination of remaining teeth and there is no way to use a lingual bar without interfering with tongue movements.

24
Q

What maxillary major connector is best used with torus palatinus?

A

Anterior-posterior palatal strap

25
Q

Give 5 cases where a full palatal plate should be used?

A

Maximum tissue support is required

  1. Long distal extensions
  2. 6 or less anterior teeth remain
  3. Abutments are periodontal involved
  4. Edentulous areas covered with flabby tissue
  5. Shallow palatal vault
26
Q

When would a palatal strap(or bar) not be used? Why?

A

Never be used in distal extensions or for replacement of anterior teeth because it needs to be made bulky for rigidity

27
Q

When should an anterior palatal plate (u shaped or horse shoe palatal connector) be used? What is its major downside?

A

Only used where the torus palatinus prevents use of other connectors.

Huge downside is you must have bulk in the rugae area where the tongue requires freedom. Also in distal extension cases there is lots of movement and may cause irritation to residual ridges

28
Q

Compare and contrast the 2 types of grid work minor connectors that connect denture bases and teeth to the major connector?

A

Mesh grid work

  • flatter
  • more potential rigidity
  • less retention for acrylic if openings are too small

Lattice gridwork

  • better retention
  • can interfere with setting of teeth (if struts are made too thick or poorly positioned)
29
Q

How much relief is required to allow acrylic resin to flow under gridwork minor connectors?

When should relief be provided under gridwork next to the abutment tooth? Why?

A

Usually 1mm of relief

1.5-2mm from abutment. This allows a metal to tissue contact immediately beside the abutment tooth which is preferable over acrylic because it wears less, is less pours, thus allowing better hygiene.

30
Q

What type of junction should there be between gridwork and the major connector? Why?

A

Should be in the form of a butt joint with a slight undercut (angle formed must not be greater than 90mdegrees). This provides max bulk of resin at the junction and prevents creation of weak, thin feather edges which can easily fracture or distort

31
Q

What type of wax blockout would we use for the small space below a proximal plate and it’s respective guiding plane?

A

Zero degree block out with wax

32
Q

How far should gridwork extend dismally in the mandible?

A

2/3 of the way from the distal abutment to the retromolar pad (but not on the ascending portion of the ridge!)

33
Q

How far should the gridwork be extended distally in the maxilla? What about the major connector?

A

2/3 the length to the Hamular notch (but the major connector should extend all the way to the hamular notch to merge with acrylic

34
Q

How far should the junction of the maxillary major connector and gridwork be from the lingual surface of a tooth?

A

Approximately 2mm

35
Q

Why should mandibular distal extensions have a tissue stop at their posterior limit?

A

Without a tissue stop the framework can be bent or displaced during pressure packing of the acrylic. If this occurs, the framework could resume its shape after deflating and the denture would lift off the tissue. Rocking of the denture base and clasp apparatus would result and occlusion would be high.

36
Q

How much should a direct trainer encircle a tooth?

A

Greater than 180 degrees

37
Q

Do we need stress releasing clasps in class 3 and 4 pds?

A

No because there is no rotation as there would be in class 1 and 2

38
Q

Rank the 4 direct retainers for tooth borne rpds (class 3 and 4)

A
  1. Circumferential clasp
  2. Ring clasp
  3. Embrasure clasp
  4. C clasp (hair-pin clasp)
39
Q

Rank the 3 clasps used for class 1 and 2?

A
  1. RPI (proximal plate, medial rest, I bar)
  2. RPA (same thing as rpi but instead of I bar you use wrought wire clasp)
  3. Combination clasp (same thing as a circumferential clasp but retentive arm is wrought wire instead of cast)
40
Q

How far should the approach arm of an I bar be from the fgm?

A

3-4 mm

41
Q

What are 3 forms of indirect retainers for class 1 and 2’s?

A
  1. Auxiliary cingulum rest
  2. Auxiliary occlusal rest
  3. Continuous bar retainers or lingual plates
42
Q

How far should external finish lines be from lingual surface of denture teeth?

A

2mm

Removable Partial Dentures 2nd year (3 decks)

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