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Removable Partial Prosthodontics > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What are the 3 types of RPDs? Which will we mainly deal with?

A
  1. Cast Metal Frame (90% of course)
  2. Acrylic
  3. Flexible
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2
Q

What are the two common metals used in a cast metal frame? Which is better?

A

CoCr (used more)
NiCr (used less because of nickel sensitivity)

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3
Q

Brief explanation of Kennedy Classifications (I-IV)

A

Class I - Bilateral distal extension (posterior to natural teeth)
Class II - Unilateral distal extension
Class III - Unilateral tooth bound extension
Class IV - Anterior extension area crossing midline

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4
Q

What are the indications for RPDs

A
  1. Edentulous area(s) too large
  2. Anterior region has lost alveolar tissue
  3. Reduced periodontal support
  4. Cross-arch stabilization
  5. No posterior abutment tooth
  6. Immediate tooth replacement
    7.Economic considerations of patient
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5
Q

(True/False) Height of contour/survey line will change if the axial inclination is changed

A

True

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6
Q

Areas of tooth contour

A

Suprabulge - About HOC
Infrabulge - Below HOC (“undercut”)

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7
Q

Which number determines the classification if multiple are present?

A

The lowest number determines the classification

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8
Q

What is a modification space?

A

An edentulous area other than that determining the classification

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9
Q

(True/False) Classification should PRECEDE any extractions that might alter the original classification

A

False, it should follow

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10
Q

What are the rules governing the application of the Kennedy Classification System? How many are there?

A

Applegate’s Rules (8)

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11
Q

Do we include 3rd molars in classification? 2nd?

A

Not if it is missing or to not be replaced. Only if it is to be used as an abutment. If 2nd molars are missing and not replaced, they do not count either - typically do not replace 2nd or 3rd molars

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12
Q

The most ________(anterior OR posterior) edentulous areas always determine the classification

A

Posterior

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13
Q

Is there ever an instance of mod areas in class IV arches?

A

No, they would be posterior, thus take charge determining the classification

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14
Q

What are the 3 types of classification in the Craddock Classification?

A

Type 1: Mucosa-borne
Type 2: Tooth-borne
Type 3: Mucosa and tooth-borne

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15
Q

What should the width of the guiding planes be?

A
  • As wide as widest portion of occlusal rest
  • 1/3 bucco-lingual width
    1/2 distance between cusp tips
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16
Q

What should the length of the guiding planes be?

A

Tooth supported abutments: 3-4 mm
Tooth-tissue supported abutments: 1.5-2 mm

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17
Q

What is the order of the survey procedure for a diagnostic cast?

A

1) Path of insertion is determined
- Guiding plane (parallel, flattened planes at prox/axial surfaces
- Retentive undercuts (between survey line and gingival margin, engaged by clasp - only retentive goes below)
- Interference
- Esthetics
2) Mark HOC
3) Measure/mark retentive undercut
4) Tripod cast

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18
Q

When establishing parallelism in a cast for the guiding planes, where is selective grinding done?

A

On the occlusal 1/3 - 1/2

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19
Q

What are typical interference areas that interrupt the path of insertion

A

Lingually inclined mandibular teeth
Buccally inclined maxillary teeth
Exotoses, tori
HOC too high - clasp too high
Tissue undercut area of bar clasp

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20
Q

Where is the survey line ideally located on a tooth? Where are the clasps located on the tooth in relation to this line?

A

HOC located at junction of middle and gingival 1/3
2/3 retentive clasp (rigid) above HOC, terminal 1/3 below (in gingival 1/3) (flexible) tapered
Reciprocal clasp is rigid component in middle 1/3, above HOC not tapered

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21
Q

What do you do if for a chosen path of insertion, the survey line?HOC is too near the occlusal surface? If it is too low with no undercuts?

A

Too high - Recontoured tooth to lower survey line
Too low - Surveyed crown

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22
Q

What is the amount of undercut for a CrCo/NiCr cast clasp?
What about for wrought wire clasp?

A

0.01” for CrCo/NiCr (least flexible)
0.015” for Cast Gold alloy
0.02” or 0.03” for wrought wire (most flexible)

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23
Q

What can you do if there is inadequate retentive undercut?

A

Enameloplasty to create “dimple”
Add composite
Surveyed crown

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24
Q

Which cast is the RPD design drawn on? What do the colors represent?

A

Diagnostic cast
Blue = metal framework and wrought wire clasp
Red = retentive undercut, tooth mod areas
Black = HOC, tripod marks and soft tissue undercuts

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25
Q

When do you make the master cast?

A

After mouth preparation, then resurvey (guiding planes, HOC, retentive undercuts, tripod, framework made)

26
Q

Rest vs Rest Seat

A

Rest is the RIGID extension of the RPD that transmits force to teeth (down the long axis of the teeth) and prevents movement toward the mucosa (cervical movement)
Rest seat is the portion of the tooth prepared to receive the rest

27
Q

What are the 5 types of rests?

A

Occlusal
Embrasure
Cingulum (Lingual)
Hooded
Incisal

28
Q

Occlusal Rest Seats: describe the location, shape, width, depth

A

Location: mesial/distal pits, centered over marginal ridges
Shape: concave (“spoon”), triangular in shape, base being over marginal ridge
Width: 1/3 buccolingual width of tooth
1/2 width between the cusp tips
Depth: 1-1.5 mm over marginal ridge
1.5-2 mm at deepest portion in pit area
- Should be inclined forming an angle less than 90 degrees

29
Q

What should the angle formed between the occlusal rest and the vertical minor connector be?

A

Less than 90 degrees

30
Q

Describe the location and form of an Embrasure Rest Seat

A

Location: between two adjacent posterior teeth, used when no posterior modification space is present
Form: Occlusal rests placed adjacent without removing contact point, but allowing for adequate tooth reduction (~1 mm)
Sluiceway should be ~2 mm evaluated using two 18-gauge wire (width of adjacent rest seats) (U-shaped trough to accommodate clasp assembly)

31
Q

How do we prepare a cingulum rest seat on mandibular vs maxillary teeth?

A

Maxillary - cut into enamel (primary)
Mandibular - composite resin (since canine does not exhibit sufficient enamel thickness lingually (still clinical long-term success)

32
Q

Form of lingual cingulum rest

A

Chevron “V” shaped
Slope slightly downward (<90 degrees with path of insertion)
Width of floor: 0.75-2 mm (1 IDEAL)
Inciso-apical depth: 1.0-1.5 mm

33
Q

Where are hooded rests indicated? Form?

A

Mandibular first premolars ONLY, cannot be on distal abutments of distal extensions
1.0-1.5 mm reduction, marginal ridge to marginal ridge

34
Q

What is the least desirable of all the rests? Why? Primarily used where?

A

Incisal Rests due to poor esthetics and occlusal interference
Mandibular canines as indirect retainers
Small, V-shaped notch

35
Q

Intracoronal vs Extracoronal Direct Retainers

A

Intra: key/keyway (most esthetic)
high maintenance and complex

Extra: Clasp assembly, more common

36
Q

Suprabulge vs infrabulge

A

Supra: approach undercut from ABOVE HOC (circumferential, akers, circlet)
Infra: Approached undercut from BELOW HOC (bar clasps)

37
Q

Are minor connectors flexible or rigid? What is an exception to the rule?

A

Rigid, an exception is the approach arm (bar clasps) which connects the clasp to the framework

38
Q

What are requirements of clasp assembly?

A

Encirclement of more than 180 degrees
Minimum of 3 points
Prevent tooth from moving away from clasp

39
Q

(True/False?) Components of direct retainers should exert no force when fully seated

A

True, retentive clasps should only become active when forces are applied to them

40
Q

Relationship between flexibility and length? How is this done? Diameter and Flexibility?

A

Flex=length^3 (double length = 8x more flex), this is done by curving the clasp
Flex=1/diameter^3 (double diameter, 8x less flexible)

41
Q

How doe the dimensions of the terminal portion of the retentive clasp compare to the origin?

A

1/2 as thick (1 –> 0.5 mm)
1/2 as wide (2 –> 1 mm)

42
Q

Which is more flexible… round clasp (wrought wire) or half-round (circumferential)? Why?

A

Round, flexes in all spatial planes, half-round flexes in one plane

43
Q

What is the most logical clasp for tooth-supported RPD (Class III) Name the types of circumferential clasps (7)

A

Circumferential Clasps
1.) Circlet
- Class III RPD clasp of choice
2.) Embrasure Clasp (2 circlet joined at body)
- Class II and III with no modification space
- Class IV
3.) Reverse Circlet (hairpin) clasp
- Last choice for Mesially-tipped mandibular molar
4.) Ring Clasp (avoid if possible)
- Mesiolingually-tipped mandibular molar (no recip.)
5.) Reverse Circlet Clasp
- Class I, II or III (avoid if possible)
6.) Combination Clasp (Class I and II)
- Wrought retentive
Cast reciprocal
7. RPC Clasp
Class I and II

44
Q

Which circumferential clasps can be used for Class I RPDs

A

Combination
RPC

45
Q

Which circumferential clasps can be used for Class I RPDs

A

Combination
RPC

46
Q

Which circumferential clasps can be used for Class II RPDs

A

Embrasure (if no mod space)
Combination
RPC

47
Q

Which circumferential clasps can be used for Class III RPDs

A

CIRCLET (BEST)
Embrasure (if no mod space)
_______________________
Reverse Circlet
Ring
Hairpin (WORST)

48
Q

Which circumferential clasps can be used for Class IV RPDs

A

Embrasure

49
Q

What should be used to prepare an undercut?

A

Round-end tapered diamond

50
Q

Where is the occlusal pressure concentrated in a tooth-tissue supported RPD? What causes this?

A

Due to the lever effect of the distal extension base, pressure is concentrated on the distal end of the base

51
Q

(True/False?) There is significant advantage of altered cast impression material when compared with one-piece cast method?

A

False, there is not significant advantage. One-step is less prone to error

52
Q

How does one mark an undercut on the master cast?

A

Red line NOT red dot at the approximate inferior edge of the clasp

53
Q

In terms of rigidity, flexibility = _____________

A

Force concentration

54
Q

How far away should the borders of the major connector be from the gingival margin for maxillary arch? Mandibular?

A

6 mm
3 mm
Needs to cross at right angles to the gingival margins

55
Q

Name the 4 kinds of maxillary major connectors

A
  1. Palatal Strap (8-10 mm)
  2. Palatal Plate (thicker, more stable, worse phonetics, uncomfy etc.)
  3. Anterior-Posterior Strap - 6-8 mm, space should be 15 mm (circumvent a torus)
  4. Horseshoe or “U” - least rigid, used in HIGH VAULT PALATE
56
Q

Beading of the maxillary cast FORM

A

1/2 round
1 mm deep, 1.5 mm wide
Feathers out to nothing 6 mm from free gingiva margin
Shallower over mid-palatal suture

57
Q

Mandibular Major Connectors (3)

A

Lingual Bar (need 7 mm from ging. margin to floor of mouth) (4-5 mm tall), located 3-4 mm below free gingival margin
Lingual Plate (if can’t use bar, more rigid)
Labial Bar

58
Q

What are the 3 types of Bar Clasps?

A
  1. T Clasp
  2. 1/2-T (DF)
  3. I-Bar (MF, mid-F)
59
Q

Tooth-supported RPD Clasps

A

1.) Circlet (circumferential) most common
- Reciprocal clasp
2.) I-Bar
- MF, mid-F undercut
3.) 1/2 T-Bar
- DF undercut
- Reciprocal clasp
4.) Reverse Circlet (hairpin)
- Tissue undercut, last resort
5.) Embrasure Clasp
- Class III, IV (no mod space)
- Also class II with tooth-tissue, no mod space

60
Q

Tooth-tissue supported RPD Clasps

A
  • RPI Clasp (rest mesial, prox plate, I bar)
  • RPC (A) Clasp
  • Combination Clasp
  • 1/2 T Clasp
  • Reverse Circumferential
61
Q

How far apart fo the vertical minor connectors in a RPI Clasp Assembly need to be? If not, what should be used?

A

5 mm, Lingual Plate if not

Removable Partial Prosthodontics (2 decks)

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