4. RPD bases

Question 1

What is the base of the denture?

Answer 1

Portion that supports artifical teeth, rests on foundation tissues and replaces alveolar structures

Question 2

What do the bases of RPDs face?

Answer 2

• foundation tissues on one side

- artifical teeth on the other side

Question 3

What parts of the RPD replace lost structures due to edentulism? (2)

Answer 3

• Denture teeth

- Bases

Question 4

Functions of RPD bases? (4)

Answer 4

• Attach the prosthetic teeth to RPD
• Be a supporting structure of the RPD: transfer occlusal forces to abutment teeth and tooth-tissue supported RPDs, to denture foundation area
• Replace missing alveolar tissue in volume and appearance
• Provide bracing, retention and in tooth-tissue supported RPDs direct-indirect retention

Question 5

Base functions: attach the prosthetic teeth - Denture teeth are…

Answer 5

Individual units that should be attached to the bases to carry out their function

Question 6

Base functions: attach the prosthetic teeth - Types of configuration of artificial teeth and RPD bases? (3)

Answer 6

• Teeth attached to acrylic resin in an extended base (with or without underlying meshwork)
• teeth attached to acrylic resin that is attached directly to a metal base (Shortened base)
• Metal occlusal surfaces

Question 7

Base functions: attach the prosthetic teeth - which type of artificial tooth configuration is the most common?

Answer 7

Teeth attached to acrylic resin in an extended base (with or without underlying meshwork)

Question 8

Base functions: attaching prosthetic teeth is useful because? (2)

Answer 8

• That way the bases help indirectly in mastication, deglutition, phonation and aesthetics
• Prevents horizontal and vertical tooth migration

Question 9

Bases: support function for the RPD? (4)

Answer 9

• Resistancce of denture to vertical intrusive forces
• must be transferred homogeneously
• transferred to teeth and/or soft tissues
• if support is correct = less bone resorption

Question 10

Bases function: Replace missing tissues? (3)

Answer 10

• Alveolar tissue - both bone and mucosa
• Restore non-tooth esthetics
• Lip and cheek support: restore face esthetics

Question 11

Bases function: Provide additional retention? (3)

Answer 11

• Because of adhesion and cohesion
• in tissue supported and tooth-tissue supported
• Important at the mandible: no major connector provides retention

Question 12

More contact surfaces with bases means

Answer 12

more retention

Question 13

Bases function: How do they provide stability?

Answer 13

Also thanks to teeth

Question 14

Bases need to be strong enough to resist … (5)

Answer 14

• Stresses which will be applied to it with the use of a thin base
• Have to bear forces and have adequate thickness
• fracture (toughness)
• deformation (Deformation)
• abrasion

Question 15

Bases should be asethetic… (3)

Answer 15

• Specially at the anterior region
• smooth and polished surface
• non absorbent

Question 16

Bases and hygiene? (2)

Answer 16

• Should not harbor microorganisms

- metal bases are the most hygenic

Question 17

Why should bases be capable of adapting to supporting tissues ?

Answer 17

Improves retention by adhesion and cohesion

Question 18

Bases and thermal conductivity?

Answer 18

Should be good thermal conductors

Question 19

What should the weight for the bases be? (2)

Answer 19

• Low weight for the upper denture

- High weight for the lower one

Question 20

Bases should be able to chemically …

Answer 20

bond to prosthetic tooth materials and RPD allows

Question 21

length (extension) of base is determined by? (2)

Answer 21

• Number of missing teeth

- Retention, support and stability

Question 22

Volume of the base will be determined by? (3)

Answer 22

• prosthetic space available
• amount of supporting tissue lost
• relationship between edentulous ridge and opposing arch

Question 23

What are the types of base extensions? (3)

Answer 23

• Extended bases
• Reduced bases
• Shortened bases

Question 24

What is an extended base?

Answer 24

• extension similar to complete dentures

Question 25

Where is the extended bases border?

Answer 25

up to the functional boundary

Question 26

Extended bases seek to achieve...

Answer 26

border seal

Question 27

Extended bases materials? (2)

Answer 27

- Acrylic resin | - with or without underlying framework

Question 28

Advantages of extended bases? (4)

Answer 28

- Provide great support - Spread the forces over more syrface - Improve rention - Easy reline

Question 29

Disadvantages of extended bases? (2)

Answer 29

Very bulky: less comfortable and physiologic rejection Less masticatory proprioception: b/c large extension & low thermal conductivity

Question 30

Extended bases can join the rest of the denture by...

Answer 30

Metal frameworks

Question 31

Extended bases: framework doesn't extend up to ...

Answer 31

The border of the base?

Question 32

What are the types of designs for extended bases? (3)

Answer 32

- Fishbone - Ladder - Mesh

Question 33

What type of extended base design is less bulky than ladder base?

Answer 33

Mesh

Question 34

Extended bases indications? (2)

Answer 34

- Great support and retention needed | - Great amount of lost tissue to restore

Question 35

What kennedy classes use extended bases? (3)

Answer 35

- Class I and II esp with long free-ended edentulous areas - Class III at the mandible with long span space and weak abutment teeth - Class IV with great bone loss - Tissue supported RPDs

Question 36

How many flaps do reduced bases?

Answer 36

2

Question 37

What is a buccal flap? (3)

Answer 37

- On the reduced base - Acrylic resin - Up to functional limit but shorter than in extended bases

Question 38

What is a lingual flap? (3)

Answer 38

- On the reduced base - Metal - Continues with major connector

Question 39

Reduced bases are the junction between framework and acrylic resin by...

Answer 39

retentive devices

Question 40

Reduced bases: There is still acrylic resin covering the...

Answer 40

Residual ridge at buccal aspect and top of ridge

Question 41

Reduced base: Why is the lingual flap made of metal?

Answer 41

Generally has less resorption

Question 42

Reduced bases: What type of surface is at the junction of material?

Answer 42

Even surface at the junction of materials

Question 43

Reduced bases: framework is usually part of the _______ & ______ together

Answer 43

Major connector and cast

Question 44

Reduced base advantage? (4)

Answer 44

- Structural strength - More comfortable - Generally produce fewer ulcers - Provide good support, retention and stability

Question 45

Reduced bases disadvantages? (3)

Answer 45

- Transmit more load to the remaining teeth - Press mucosa more - More difficult retouches (due to metal part)

Question 46

Reduced base indications?

Answer 46

Need for support and stability of denture but good anatomical situation

Question 47

What kennedys classes do we use for a reduced base?

Answer 47

All

Question 48

When do we use a reduced base for kennedy class I?

Answer 48

Esp at maxilla with short span edentulous areas

Question 49

When do we use a reduced base for kennedy class II ?

Answer 49

Esp at maxilla with short span edentulous areas

Question 50

When do we use a reduced base for kennedy class III?

Answer 50

- alveolar ridge loss | - unsuitable abutment teeth

Question 51

When do we use a reduced base for kennedy class IV?

Answer 51

- alveolar ridge loss | - unsuitable abutment teeth

Question 52

Why cant we use a reduced base with unsuitable abutment teeth?

Answer 52

They need more support and stability

Question 53

Shortened bases characteristics? (4)

Answer 53

- Only cover the top of the ridge - Saddle shape - With retention pins for denture teeth - Fully metallic to comply with mechanical requirements

Question 54

Advantages of shortened bases? (4)

Answer 54

- Comfortable b/c reduced volume - Good esthetics b/c no acrylic to mimic gingiva - Hygienic - Good health preservation of attached gingiva because of low coverage

Question 55

Shortened bases disadvantages? (3)

Answer 55

- Dont provide support to the denture: Need strong abutment teeth - Dont provide additional retention or stability

Question 56

Shortened bases indications?

Answer 56

- Typical of tooth supported RPDs (but not always) | - For every edentulous area of only 1 tooth that implies a modification of any kennedys class

Question 57

What kennedys classes do we use for shortened bases? (2)

Answer 57

Class III and class IV

Question 58

When do we use a shortened bases for a kennedy class IV?

Answer 58

Class IV with little bone loss

Question 59

When do we use a shortened bases for a kennedy class III?

Answer 59

Class III with short edentulous areas (1-2 teeth)