4. RPD bases Flashcards
What is the base of the denture?
Portion that supports artifical teeth, rests on foundation tissues and replaces alveolar structures
What do the bases of RPDs face?
- foundation tissues on one side
- artifical teeth on the other side
What parts of the RPD replace lost structures due to edentulism? (2)
- Denture teeth
- Bases
Functions of RPD bases? (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
Base functions: attach the prosthetic teeth - Denture teeth are…
Individual units that should be attached to the bases to carry out their function
Base functions: attach the prosthetic teeth - Types of configuration of artificial teeth and RPD bases? (3)
- 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
Base functions: attach the prosthetic teeth - which type of artificial tooth configuration is the most common?
Teeth attached to acrylic resin in an extended base (with or without underlying meshwork)
Base functions: attaching prosthetic teeth is useful because? (2)
- That way the bases help indirectly in mastication, deglutition, phonation and aesthetics
- Prevents horizontal and vertical tooth migration
Bases: support function for the RPD? (4)
- 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
Bases function: Replace missing tissues? (3)
- Alveolar tissue - both bone and mucosa
- Restore non-tooth esthetics
- Lip and cheek support: restore face esthetics
Bases function: Provide additional retention? (3)
- Because of adhesion and cohesion
- in tissue supported and tooth-tissue supported
- Important at the mandible: no major connector provides retention
More contact surfaces with bases means
more retention
Bases function: How do they provide stability?
Also thanks to teeth
Bases need to be strong enough to resist … (5)
- 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
Bases should be asethetic… (3)
- Specially at the anterior region
- smooth and polished surface
- non absorbent
Bases and hygiene? (2)
- Should not harbor microorganisms
- metal bases are the most hygenic
Why should bases be capable of adapting to supporting tissues ?
Improves retention by adhesion and cohesion
Bases and thermal conductivity?
Should be good thermal conductors
What should the weight for the bases be? (2)
- Low weight for the upper denture
- High weight for the lower one
Bases should be able to chemically …
bond to prosthetic tooth materials and RPD allows
length (extension) of base is determined by? (2)
- Number of missing teeth
- Retention, support and stability
Volume of the base will be determined by? (3)
- prosthetic space available
- amount of supporting tissue lost
- relationship between edentulous ridge and opposing arch
What are the types of base extensions? (3)
- Extended bases
- Reduced bases
- Shortened bases
What is an extended base?
- extension similar to complete dentures
Where is the extended bases border?
up to the functional boundary
Extended bases seek to achieve…
border seal
Extended bases materials? (2)
- Acrylic resin
- with or without underlying framework
Advantages of extended bases? (4)
- Provide great support
- Spread the forces over more syrface
- Improve rention
- Easy reline
Disadvantages of extended bases? (2)
Very bulky: less comfortable and physiologic rejection
Less masticatory proprioception: b/c large extension & low thermal conductivity
Extended bases can join the rest of the denture by…
Metal frameworks
Extended bases: framework doesn’t extend up to …
The border of the base?
What are the types of designs for extended bases? (3)
- Fishbone
- Ladder
- Mesh
What type of extended base design is less bulky than ladder base?
Mesh
Extended bases indications? (2)
- Great support and retention needed
- Great amount of lost tissue to restore
What kennedy classes use extended bases? (3)
- 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
How many flaps do reduced bases?
2
What is a buccal flap? (3)
- On the reduced base
- Acrylic resin
- Up to functional limit but shorter than in extended bases
What is a lingual flap? (3)
- On the reduced base
- Metal
- Continues with major connector
Reduced bases are the junction between framework and acrylic resin by…
retentive devices
Reduced bases: There is still acrylic resin covering the…
Residual ridge at buccal aspect and top of ridge
Reduced base: Why is the lingual flap made of metal?
Generally has less resorption
Reduced bases: What type of surface is at the junction of material?
Even surface at the junction of materials
Reduced bases: framework is usually part of the _______ & ______ together
Major connector and cast
Reduced base advantage? (4)
- Structural strength
- More comfortable
- Generally produce fewer ulcers
- Provide good support, retention and stability
Reduced bases disadvantages? (3)
- Transmit more load to the remaining teeth
- Press mucosa more
- More difficult retouches (due to metal part)
Reduced base indications?
Need for support and stability of denture but good anatomical situation
What kennedys classes do we use for a reduced base?
All
When do we use a reduced base for kennedy class I?
Esp at maxilla with short span edentulous areas
When do we use a reduced base for kennedy class II ?
Esp at maxilla with short span edentulous areas
When do we use a reduced base for kennedy class III?
- alveolar ridge loss
- unsuitable abutment teeth
When do we use a reduced base for kennedy class IV?
- alveolar ridge loss
- unsuitable abutment teeth
Why cant we use a reduced base with unsuitable abutment teeth?
They need more support and stability
Shortened bases characteristics? (4)
- Only cover the top of the ridge
- Saddle shape
- With retention pins for denture teeth
- Fully metallic to comply with mechanical requirements
Advantages of shortened bases? (4)
- 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
Shortened bases disadvantages? (3)
- Dont provide support to the denture: Need strong abutment teeth
- Dont provide additional retention or stability
Shortened bases indications?
- Typical of tooth supported RPDs (but not always)
- For every edentulous area of only 1 tooth that implies a modification of any kennedys class
What kennedys classes do we use for shortened bases? (2)
Class III and class IV
When do we use a shortened bases for a kennedy class IV?
Class IV with little bone loss
When do we use a shortened bases for a kennedy class III?
Class III with short edentulous areas (1-2 teeth)
