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REMOVABLE > direct retainers part 2 > Flashcards

direct retainers part 2 Flashcards

1
Q

retentive arm approaches undercut from below the survey line

A

infrabulge
-bar clasps

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2
Q

retentive arm approaches undercut from ABOVE survey line

A

suprabuldge
-circumferential, akers, circlet

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3
Q

circumferential

A

suprabulge

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4
Q

bar clasps
t clasp
1/2 T clasp
I-bar

A

infrabulge

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5
Q

bar clasps indicated:

A
  1. distal extension RPD
  2. tooth-supported RPD, esthetics factor
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6
Q

most common bar clasps

A

I-bar
1/2(modified) T bar clasp

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7
Q

advantages and disadvantages to bar clasps

A

adv:
1. more esthetic
2. more flexible
3. less conducive to caries (less tooth coverage)
4. wider range of undercut adaptability
- MF, mid-F (I-bar)
-DF (1/2 T bar)

disadv:
1. less bracing
2. possible tissue impingement
3. food impaction

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8
Q

bar clasp rules for approach arm

A
  1. must not impinge on soft tissue
  2. tapered
  3. cross gingival margin at 90 degrees
  4. extend onto abutment tooth to HOC
    • not positioned over soft tissues undercut: food trap, tissue irritation
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9
Q

selection of RPD classes.

  1. tooth-supported RPDs:
  2. Tooth-tissue supported RPDs:
A
  1. tooth-supported RPD:
    - class III, short span class IV
  2. tooth-tissue supported RPD:
    -class I and II, long-span class IV(missing all anterior teeth)
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10
Q

tooth supported RPD clasps:

A
  1. circumferential
    -most common
    retentive undercut remote from endentulous area
    -reciprocal clasp
  2. I-bar
    -mesiofacial, midfacial undercut
    -reciprocal clasp
    -tissue undercut prevents use
  3. 1/2 T bar
    -retentive undercut adjacent to endentulous area
    -distal-facial undercut
    -reciprocal clasp
    -tissue undercut prevents use
  4. reverse circlet (hairpin)
    -retentive undercut adjacent to edentulous area
    -*used when tissue undercut present and T bar cant be used
    -excess tooth coverage, disadvantage
  5. embrasure clasp
    -used when retainer is necessary in a dentate area
    -class III and IV arch with no mod spaces
    -also class II tooth-tissue supported with no mod
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11
Q

use this tooth-supported clasp when tissue undercut present and cant use T bar or I bar

A

hairpin

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12
Q

imaginary line connecting occlusal rests around which a partial removable dental prosthesis tends to rotate under masticatory forces.

determinants for this line are usually the cross arch occlusal rests located adjacent to the tissue borne components

A

fulcrum line

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13
Q

tooth-tissue supported RPD class selection:

A

-rotation of the RPD toward residual ridge around the horizontal fulcrum line
1. factor in class I and II extensions
2. RPD potentially functions as lever
3. can result in detrimental clasp forces on the abutment teeth

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14
Q

why rotation of RPD toward the residual ridge around the horizontal fulcrum line?

A

-difference in potential movement of abutment and mucoperiosteum over residual ridge
-0.25,, periodontal ligament, 2mm mucoperiosteum
-0.25mm=0.01” (related to retentive clasp)

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15
Q

distal abutment retentive clasp (should/should not) be anterior to terminal rest fulcrum line

A

NOT

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16
Q

distal rest/distal guide plane:
(for distal extension RPD clasp selection)

A

class I lever
-torquing force on abutment

17
Q

mesial rest/distal guide plane

A

class II lever
-retentive tip disengages abutment
-*stress-release clasp design

(what we want since dont want retentive clasp to be anterior to termina rest fulcrum line???)

18
Q

anterior placement of the rest helps direct the forces:

A

more vertically onto tissues of residual ridge

19
Q

tooth-tissue supported (distal extension) RPD clasp selection:
stress-release clasps used on=
what clasps=

A

class I and II RPD distal abutments
-RPI clasp assembly (rest, proximal plate, I-bar)
-RPC (A) clasp assembly (rest, proximal plate, Circumferential clasp)
-combination clasp
-1/2 T clasp
-revere circumferential clasp

20
Q

RPI class assembly made of

A

rest
proximal plate
I-bar
-mesiofacial or Mid-facial retentive undercut

reciprocation:
-ML minor connector
-distal proximal plate

21
Q

RPI clasp assembly prepared guiding planes:
distal
ML minor connector

A

distal guiding plane:
occlusal 1/3 to 1/2
2-3mm
guide plate contacts ~1-1.5mm of plane
undercut is necessary below the guide plane

ML minor connector GP:
occlusal 1/3
1-2mm

22
Q

RPI class assembly structural details:

A
  1. I-bar 2mm contact at retentive undercut
  2. approach arm
    -3mm from gingival margin
    -crosses gingival margin 90 degrees
  3. distal proximal plate width
    -line angle to line angle
  4. major connector
    -3mm from gingival mand
    -6mm from gingival max
23
Q

RPI class assembly stress release:

A

-rotation around mesial rest/fulcrum
-distal guide plate and I-bar move mesiogingivally
(I-bar disengages from tooth=stress release)
-ML minor conenctors rotates mesio-occlusally

24
Q

with RPI clasp assembly, stress release design to have relief below:

A

distal plate: undercut below guide plane
-allow proximal plate to move

ML minor connector not contact adjacent tooth to allow rotation

25
Q

with RPI clasp assembly, need ___mm separation between vertical minor connector and if cant, then should use lingual plate

A

5mm

26
Q

contraindications for RPI clasp

A

-excess tissue undercut
-shallow vestibule
-abutment excess facial inclination(high survey line, retentive undercut too high and not in gingival 1/3)

27
Q

RPC clasp assembly

A
  1. rest(mesial)
  2. proximal plate
  3. circumferential clasp
  4. mesiofacial retentive undercut
  5. circumferential retentive clasp
    -*cast round for class I w/o mod and periodontally compromised teeth

reciprocation:
1. ML minor connector
2. distal proximal plate wrap to lingual

28
Q

RPC clasp assembly structural details:

A
  1. hybrid clasp: RPI and circumferential concepts
  2. similar to circumferential retentive clasp
    -proximal 2/3: middle 1/3 of tooth ON survey line
    -terminal retentive 1/3: gingival 1/3, below survey line

guide planes same as RPI

29
Q

RPC clasp assembly stress release:

A
  1. rotation around mesial rest/fulcrum
  2. circumferential clasp and distal guide plate move mesiogingivally
    -clasp disengages from toth
    -ML minor connector rotates mesio-occlusally
30
Q

RPC clasp assembly stress release designed to have relief below:

A

distal guide plate, undercut below plane
1. proximal 2/3 of retentive clasp exactly on survey line
2. failure to follow=fulcrum moves to proximal area of clasp

31
Q

combination clasp

A

distal rest
wrought wire
retentive clasp
cast reciprocal clasp
-mesiofacial undercut

32
Q

indications of combination clasp

A
  1. mesial-inclination of abutment distal surface
    -no undercut below guide plane
    -RPC, RPI no stress release
  2. mesial rest cannot be used
    -RPC, RPI no stress release
33
Q

combination clasp stress release

A
  1. rotation occurs at DISTAL REST minor connector
  2. clasp moves occlusally
    -class I level occurs
    -distal torquing force occurs
    -*flexability of wrought wire limits torque
34
Q

modified 1/2 T clasp:

indications:
reciprocations:
stress relief:

A
  1. mesial rest
  2. distal proximal plate
  3. 1/2 T bar clasp

indications:
1. distofacial retentive undercut

reciprocations:
ML minor connector, distal plate

35
Q

contraindications for modified 1/2 T clasp

A

-tissue undercut
-shallow vestibule
-abutment excess facial inclination (high survey line, and retentive undercut too high not in gingival 1/3)

36
Q

reverse circumferential clasp:
indications:
reciprocation:

A

mesial rest
distal guide plate
reverse cast circumferential retentive clasp

indications:
-distofacial retentive undercuts
-1/2 T clasp contraindicated

reciprocation:
-ML minor connector, distal plate

37
Q

overview tooth-supported RPD selection

A
  1. rests adjacent to endentulous areas
  2. clasps by convience
    -no fulcrum lines, no rotation
    -determined by site of retentive undercut
    -tissue undercut
  3. reciprocation rules still aplly
    -**often cast circumferential clasp

(class III has no fulcrum line**)

38
Q

overview tooth-tissue supported (distal extension) RPD class selection

A
  1. mesial rests
  2. stress-release clasps used
  3. reciprocation still needed (ML minor connector and distal plate rather than circumferential reciprocal clasp)
39
Q

look at last few slides with table and recreate!!

A

REMOVABLE (12 decks)

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