Indirect Retainers, denture Base Considerations

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 movement of:

Answer 2

the distal extension base away from the residual ridge

Question 3

indirect retainer lever conversion

Answer 3

converts from class I lever to class II

Question 4

Indirect Retainer Functions
❑Limit?
❑Reduce leverage?
❑Reduce tissue impingement?
❑Increase RPD?
❑use in relining?

Answer 4

Indirect Retainer Functions
❑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 is usually what?
assists what other component?

Answer 5

❑Usually a rest located on the opposite
side of the fulcrum line that assist the
direct retainer in resisting movement
of the RPD in an occlusal direction-
like when eating sticky food**

Question 6

Requirements of an Indirect Retainer
❑ Usually in the form of?
❑ Ideal position?
❑ Place?

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 depends on?

Answer 7

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

Question 8

The ________ the distance between the fulcrum line and the indirect
retainer, the more effective the direct retainer will be.

Answer 8

The greater the distance between the fulcrum line and the indirect
retainer, the more effective the direct retainer will be.

Question 9

rigidity of indirect retainer:
the ideal component used?
can rugae be used?
what type of major connector alone is not acceptable as an indirect retainer? how can this be fixed?

Answer 9

❑ Rests are excellent
❑ Rugae are not good indirect retainers
❑ Lingual plating alone is not acceptable, must have rests on both ends

Question 10

Forms/Location of Indirect Retainers

Answer 10

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

Question 11

lingual plate major connectors as indirect retainer must have:

Answer 11

ests at each end, otherwise lingual plate
IS NOT an indirect retainer

Question 12

Indirect Retainer Placement

Answer 12

❑Anterior to horizontal fulcrum line
❑Perpendicular to fulcrum line

Question 13

Class I/II indirect retainer numbers

Answer 13

❑Class I RPD: 2 indirect retainers
❑Class II RPD: 1 indirect retainer

Question 14

Denture Base Movement Towards the tissue
❑ Rotation occurs around?
❑ Resisted by?

Answer 14

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

Question 15

Denture Base Movement Away from the tissue
where is rotation?
resisted by?

Answer 15

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

Question 16

Denture Base Functions of
Tooth-supported RPD

Answer 16

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

Question 17

denture base functions with tooth tissue supported RPD

Answer 17

1. same as tooth supported plus the following:
2. Vertical support
3. Secondary retention: interfacial surface tension between base & underlying mucosa

Question 18

Distal Extension RPD
Denture Base stress distribution Considerations

Answer 18

❑Distribute the forces of occlusion over as many teeth & as much soft tissue area as possible
❑Stress = Occlusal Force / Area
❑Increased Area: Decreased stress

Question 19

soft tissue? bone? coverage? accuracy of fit?

Factors Affecting Denture Base Support of Distal Extension RPD

Answer 19

1. Quality of soft tissue over residual
   ridge
   ❑More displaceable tissue, less support
2. Type of bone
   ❑Cortical bone better support than cancellous
3. Amount of denture base tissue
   coverage
4. Accuracy of fit of the denture base
   ❑Importance of accurate impression

Question 20

Requirements of an Ideal Denture
Base Material
1. Accurate & dimensionally?
2. Tissue compatibility?
3. Thermal conductivity?
4. specific gravity?
5. strength?
6. Esthetic?
7. Potential for future what?

Answer 20

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 21

adjustment? estheitc? part of? thermal? thin? indication?

metal as a base material

Answer 21

❑Difficult to adjust
❑Poor esthetics
❑Part of cast framework
❑Good thermal conductivity
❑Can be kept thin:
❑Advantage where inadequate inter-arch space

Question 22

common? reline/adjust? looks? attachment?

PMMA denture base

Answer 22

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

Question 23

distal extensions on both arches? how is this done? what type of connector is this considered?

Acrylic Resin Denture Base Retention

Answer 23

❑Considered a minor connector

❑Mandibular
❑Extend 2/3 distance to retromolar pad
❑Maxillary
❑Extend 2/3 distance to hamular notch

❑Types:
❑Lattice
❑Mesh
❑Retentive beads

Question 24

Lattice Retention

Answer 24

❑Two struts of metal
❑Extend longitudinally along residual ridge
❑Positioned buccal & lingual to ridge crest
❑Avoid longitudinal strut along ridge crest
❑Interferes with tooth placement
❑Cleavage action occurs within denture base
❑Strongest attachment
❑Easiest to reline
❑Preferred retention

Question 25

Mesh Retention

Answer 25

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

❑Incorrect mesh construction: Longitudinal strut across
ridge crest, Interferes with tooth placement, or High stress site: Cleavage of denture base

Question 26

Cast Stop on Mandibular Base
essential for?
Projects from?

Answer 26

A cast stop is essential to prevent displacement or deformation of the metal framework during resin-packing procedures.
Projects from the tissue surface of the minor connector to contact the dental cast.

Question 27

joining of acrylic and metal on the internal surface

Answer 27

A butt joint should be used to join acrylic resin and metal components at the internal surface of a RPD. Each internal finish line should display an angle of 90 degrees.

Question 28

internal line angles of external finish lines where acrylic and metal meet, why?

Answer 28

The internal angles of external finish lines should be slightly less
than 90 degrees. This results in improved mechanical retention for
acrylic resin components.

Question 29

purpose of the finish lines

Answer 29

Question 30

why should the acrylic have more bulk

Answer 30

Question 31

acrylic denture teeth

Answer 31

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

Question 32

porcelin denture teeth cons
❑Fracture?
❑Wear?
❑Difficult to?
❑Retention?

Answer 32

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

Question 33

Tube teeth

Answer 33

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

Question 34

Reinforced acrylic pontics (RAPs)
where and why are these used?

Answer 34

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

Question 35

Metal teeth
used when?
esthetics?
used where in arch?
adjustments?

Answer 35

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