Indirect Retainers

Question 1

Indirect Retainer

Answer 1

The component of a RPD that assists the direct retainer
in preventing displacement of the distal extension
denture base by functioning through lever action on
the opposite side of the fulcrum line when the denture
base moves away from the tissues in pure rotation
around the fulcrum line.

Question 2

Indirect Retainer
❑Prevents

Answer 2

movement of the distal
extension base away from the residual
ridge

Question 3

Indirect Retainer
❑Converts

Answer 3

Class I lever to Class II lever

Question 4

Indirect Retainer Functions
(5)

Answer 4

❑Limit RPD vertical dislodgement
❑Reduce leverage on abutments
❑Reduce tissue impingement by
mandibular major connectors
❑Increase RPD stability & support
❑Stabilize the framework during relining

Question 5

INDIRECT RETAINER
❑ Usually a rest located on the

Answer 5

opposite
side of the fulcrum line that assist the
direct retainer in resisting movement
of the RPD in an occlusal directionlike when eating sticky food

Question 6

Requirements of an Indirect
Retainer
(3)

Answer 6

❑ Usually in the
form of an
auxiliary rest
❑ Ideal position
is
perpendicular
to fulcrum line
❑ Place as far
forward of
fulcrum line as
possible

Question 7

Effectiveness of an Indirect Retainer
(3)

Answer 7

❑ Properly prepared rest seats
❑ Distance from the fulcrum line
❑ Rigidity of the indirect retainer

Question 8

Distance from the fulcrum line
The greater the distance between the fulcrum line and the indirect
retainer, the

Answer 8

more effective the direct retainer will be.

Question 9

Rigidity of the indirect retainer
(3)

Answer 9

❑ Rests are excellent
❑ Rugae are not good indirect retainers
❑ Lingual plating alone is not acceptable

Question 10

Forms/Location of Indirect Retainers
(4)

Answer 10

❑Occlusal rest/premolar
❑Lingual rest/Canine
❑Incisal rest/Incisor or Canine (less common)
❑Lingual plate major connector

Question 11

Lingual plate major connector
❑ MUST have rests at each end, otherwise

Answer 11

lingual plate
IS NOT an indirect retainer

Question 12

Indirect Retainer Placement
(2)
❑Class I RPD: – indirect retainers
❑Class II RPD: – indirect retainer

Answer 12

❑Anterior to horizontal fulcrum line
❑Perpendicular to fulcrum line

2
1

Question 13

Denture Base
Movement
❑ Towards the tissue
(2)

Answer 13

❑ Rotation occurs around
most distal rests
❑ Resisted by rests and
denture base

Question 14

Denture Base
Movement
❑ Away from the
tissue
(2)

Answer 14

❑ Rotation occurs
around distal
most retentive
tips
❑ Resisted by
retentive clasp
when there is an
indirect retainer

Question 15

Denture Base Functions
Tooth-supported RPD
(3)

Answer 15

1. Support prosthetic teeth
2. Esthetics: replace missing tissue
3. Horizontal stability

Question 16

Denture Base Functions
Tooth-tissue supported RPD
(3)

Answer 16

1. All of the above plus the following:
2. Vertical support
3. Secondary retention: interfacial surface
   tension between base & underlying mucosa

Question 17

Broad-stress distribution

Answer 17

❑ Distribute the forces of occlusion over as
many teeth & as much soft tissue area as
possible

Question 18

❑ Stress =

Answer 18

Occlusal Force / Area

Question 19

❑ — Area: — stress

Answer 19

Increased
Decreased

Question 20

Factors Affecting Denture Base
Support of Distal Extension RPD
(4)

Answer 20

1. Quality of soft tissue over residual
   ridge
2. Type of bone
3. Amount of denture base tissue
   coverage
4. Accuracy of fit of the denture base

Question 21

1. Quality of soft tissue over residual
   ridge

Answer 21

❑ More displaceable tissue, less support

Question 22

2. Type of bone

Answer 22

❑ Cortical bone better support than cancellous

Question 23

4. Accuracy of fit of the denture base

Answer 23

❑ Importance of accurate impression

Question 24

Requirements of an Ideal Denture
Base Material
(7)

Answer 24

1. Accurate & dimensionally stable
2. Tissue compatibility
3. Thermal conductivity
4. Low specific gravity: light weight
5. Sufficient strength: resist fracture
6. Esthetic
7. Potential for future reline

Question 25

Denture Base Materials
Metal
(5)

Answer 25

❑Difficult to adjust
❑Poor esthetics
❑Part of cast framework
❑Good thermal conductivity
❑Can be kept thin:

Question 26

❑Can be kept thin:
Advantage where

Answer 26

inadequate inter-arch
space

Question 27

Denture Base Materials
❑Polymethyl methacrylate (PMMA)
(5)

Answer 27

❑Acrylic resin
❑Most common
❑Easily adjusted & relined
❑Good esthetics
❑Attachment to framework by lattice or
mesh

Question 28

Acrylic Resin Denture Base Retention
❑Considered a — connector

Answer 28

minor

Question 29

Acrylic Resin Denture Base Retention
❑Mandibular

Answer 29

❑ Extend 2/3 distance to
retromolar pad

Question 30

Acrylic Resin Denture Base Retention
❑Maxillary

Answer 30

❑ Extend 2/3 distance to hamular notch

Question 31

Acrylic Resin Denture Base Retention
❑Types: (3)

Answer 31

❑ Lattice
❑ Mesh
❑ Retentive beads

Question 32

Lattice Retention
(4)

Answer 32

❑Two struts of metal
❑Strongest attachment
❑Easiest to reline
❑Preferred retention

Question 33

Two struts of metal
(3)

Answer 33

❑ Extend longitudinally along residual ridge
❑ Positioned buccal & lingual to ridge crest
❑ Avoid longitudinal strut along ridge crest

Question 34

❑ Avoid longitudinal strut along ridge crest
(2)

Answer 34

• Interferes with tooth placement
• Cleavage action occurs within denture base

Question 35

Mesh Retention
(3)

Answer 35

❑Thin sheet of metal with multiple
holes
❑Extension over ridge similar to lattice
❑Inferior attachment strength

Question 36

❑Incorrect mesh construction
(3)

Answer 36

❑ Longitudinal strut across
ridge crest
❑ Interferes with tooth placement
❑ High stress site: Cleavage of denture base

Question 37

Cast Stop on Mandibular Base
❑ A cast stop is essential to

Answer 37

prevent displacement or
deformation of the metal framework during resinpacking procedures

Question 38

Cast Stop on Mandibular Base
Projects from the tissue surface of the minor
connector to

Answer 38

contact the dental cast.

Question 39

A butt joint should be used to join acrylic resin and metal
components at the — surface of a RPD. Each internal finish
line should display an angle of – degrees.

Answer 39

internal
90

Question 40

❑ The internal angles of external finish lines should be

Answer 40

slightly less
than 90 degrees. This results in improved mechanical retention for
acrylic resin components.

Question 41

purpose of finish lines

Answer 41

to create a distinct resin-metal interface and to prevent the acrylic resin from becoming too thin

Question 42

because acrylic resin gains its strength with increasing bulk, it should not be

Answer 42

finished to a thin edge

Question 43

if this is attempted, the material may

Answer 43

chip or fracture

Question 44

this can create…

Answer 44

unhygenic and potentially irritating conditions

Question 45

Tooth Replacement
❑ Acrylic
(4)

Answer 45

❑ Most common
❑ Easily adjusted
❑ Not wear opposing natural dentition
❑ Chemical bond with denture base

Question 46

Tooth Replacement
❑ Porcelain
(4)

Answer 46

❑ Fracture easily
❑ Wear opposing dentition
❑ Difficult to adjust
❑ Mechanical retention only to denture base

Question 47

Tooth Replacement
❑ Tube teeth
(3)

Answer 47

❑ Denture tooth with drilled channel
❑ Secured to metal post
❑ Used with metal base: inadequate interarch space

Question 48

Tooth Replacement
❑ Reinforced acrylic pontics (RAPs)
(3)

Answer 48

❑ Composite resin polymerized around projections of
metal from denture base
❑ Anterior teeth only
❑ Inadequate interarch space

Question 49

Tooth Replacement
❑ Metal teeth
(4)

Answer 49

❑ Used with severely inadequate interarch space
❑ Poor esthetics
❑ Used only in posterior
❑ Difficult to adjust