direct retainers part 2

Question 1

retentive arm approaches undercut from below the survey line

Answer 1

infrabulge
-bar clasps

Question 2

retentive arm approaches undercut from ABOVE survey line

Answer 2

suprabuldge
-circumferential, akers, circlet

Question 3

circumferential

Answer 3

suprabulge

Question 4

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

Answer 4

infrabulge

Question 5

bar clasps indicated:

Answer 5

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

Question 6

most common bar clasps

Answer 6

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

Question 7

advantages and disadvantages to bar clasps

Answer 7

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

Question 8

bar clasp rules for approach arm

Answer 8

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

Question 9

selection of RPD classes.

1. tooth-supported RPDs:
2. Tooth-tissue supported RPDs:

Answer 9

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)

Question 10

tooth supported RPD clasps:

Answer 10

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

Question 11

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

Answer 11

hairpin

Question 12

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

Answer 12

fulcrum line

Question 13

tooth-tissue supported RPD class selection:

Answer 13

-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

Question 14

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

Answer 14

-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)

Question 15

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

Answer 15

NOT

Question 16

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

Answer 16

class I lever
-torquing force on abutment

Question 17

mesial rest/distal guide plane

Answer 17

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???)

Question 18

anterior placement of the rest helps direct the forces:

Answer 18

more vertically onto tissues of residual ridge

Question 19

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

Answer 19

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

Question 20

RPI class assembly made of

Answer 20

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

reciprocation:
-ML minor connector
-distal proximal plate

Question 21

RPI clasp assembly prepared guiding planes:
distal
ML minor connector

Answer 21

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

Question 22

RPI class assembly structural details:

Answer 22

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

Question 23

RPI class assembly stress release:

Answer 23

-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

Question 24

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

Answer 24

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

ML minor connector not contact adjacent tooth to allow rotation

Question 25

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

Answer 25

5mm

Question 26

contraindications for RPI clasp

Answer 26

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

Question 27

RPC clasp assembly

Answer 27

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

Question 28

RPC clasp assembly structural details:

Answer 28

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

Question 29

RPC clasp assembly stress release:

Answer 29

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

Question 30

RPC clasp assembly stress release designed to have relief below:

Answer 30

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

Question 31

combination clasp

Answer 31

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

Question 32

indications of combination clasp

Answer 32

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

Question 33

combination clasp stress release

Answer 33

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

Question 34

modified 1/2 T clasp: indications: reciprocations: stress relief:

Answer 34

1. mesial rest 2. distal proximal plate 3. 1/2 T bar clasp indications: 1. distofacial retentive undercut reciprocations: ML minor connector, distal plate

Question 35

contraindications for modified 1/2 T clasp

Answer 35

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

Question 36

reverse circumferential clasp: indications: reciprocation:

Answer 36

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

Question 37

overview tooth-supported RPD selection

Answer 37

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**)

Question 38

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

Answer 38

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

Question 39

look at last few slides with table and recreate!!