Removable Partial Dentures Flashcards
Path of placement/path of insertion
The specific direction in which the prosthesis is placed on the residual alveolar ridge, abutment teeth, dental implant abutment(s) or attachments.
Retention
The quality inherent in the dental prosthesis acting to resist the forces of dislodgement along the path of placement.
Guide planes
Limit the path of insertion = better retention
Support
The foundation area on which a prosthesis rests; with respect to dental prostheses, the resistance to forces directed toward the basal tissue or underlying structures.
Rest seats
Provide support for the prosthesis
Saddle
The part of the denture which rests on the foundation tissue and to which teeth are attached.
Classification for partial dentures that we use
Kennedy (1925)
Applegate (1960)
Class I kennedy classification
Bilateral free end saddles
Rest seats on mesial side of most mesial teeth
Class II kennedy classification
Unilateral free end saddle
Class III kennedy classification
Tooth bounded saddle
Class IV kennedy classification
Free end saddle anteriorly
Class V Applegate
Tooth bounded edentulous saddle where the anterior abutment is weak e.g. lateral incisor abutment that is incapable of providing support for conventional RPD and the edentulous space is long.
Class VI Applegate
Tooth-bounded edentulous area but restoration can be a fixed partial space as the edentulous space is short and abutments are capable of providing support for the denture
Design steps for RPD
- Saddle
- Support: rest seats
- Retention: clasps, guide planes
- Indirect retention: rest seat
- Minor connectors
- Major connectors
- Simplification - so much metal can we simplify the design
Craddock denture types
Tooth-borne
Mucosa-borne
Mucosa- and tooth-borne
What is indirect retention?
Resistance to rotation about clasp axis by acting on the opposite side to the displacing force.
(Prevents denture from rocking where there is a free end saddle)
RPI System
Rest
Proximal plate
I bar
Whenever there is a fre end saddle, covering more than 180 degrees of the tooth.
When would you consider the altered cast technique?
Long saddles
Types of rest seats
Occlusal, cingulum, incisal (not placed due to aesthetics)
How do you prepare a rest seat?
Marginal ridge is lowered to allow sufficient thickness without creating an occlusal interference - to 1-1.5mm
Teeth where rest seats will be provided should be…
Periodontally sound, have enough tooth tissue and good endodontic status
How to find out where to place clasps?
Use a surveyor to draw lines over abutment teeth. These lies will show you the bulbosity of your abutment teeth = height of contour and gingival to this is the undercut. Clasps will engage at the undercut.
Different types of clasps
Occlusally approaching
Gingival approaching: I bar, T bar, J bar and Y bar
When should RPA (Akers) system be used?
Can’t accommodate a gingival approaching clasp e.g. not enough gingival sulcus for I bar to engage the tooth or massive bony tuberosity
Rest seat, proximal plate + akers clasp
Aesthetic clasps properties
Made from thermoplastic resin, no metal show, great resistance to fracture, lose brightness over time, difficult to adjust and repair
Major connectors should be
Rigid, have smooth and rounded line angles, conform to anatomic structures, not interfere with moveable tissues, not allow food entrapment, not cover more tissue than necessary, not use marginal gingiva for support and not impinge on soft and hard tissue.
Types of major connectors for maxilla
- Anterior-posterior palatal strap (ring)
- Palatal strap
- Palatal plate
- Horseshoe (if pt gags, bony tuberosity)
Types of major connectors for the mandible
- Lingual bar (need minimum 7mm space
- Sublingual bar
- Dental bar
- Lingual plate (most commonly used)
- Labial bar (if pts’ teeth are too lingually placed, rarely used e.g. cancer pts)
Minor connector
Anything that connects bits of the denture together.
