BDS2 RPDS revision Flashcards
What is a saddle area?
an edentulous aeea
- the area of missing teeth to be restored with a partial denture
what is a saddle?
part of the denture that carries the replacement prosthetic teeth to fill the edentulous area
types of saddle area
bounded saddle
free-end sadd
Kennedy Class I - define
bilateral free-end saddles
Kennedy class II - define
unilateral free-end saddle
Kennedy Class III - define
bounded saddle
Kennedy Class IV - define
Anterior bounded saddle
crossing the midline
Give the Kennedy classification for an anterior saddle that does not cross the midline?
Kennedy Class III
In dentures with multiple saddles, which saddle is used to classify the arch?
the most posterior saddle
Define the term ‘support’ in relation to partial dentures
the resistance of a denture to occlussally directed load
How to improve support for a denture?
utilise remaining natural teeth
spread load over large surface area (soft tissue)
Craddock class 1 - define
tooth borne
Craddock Class II - define
mucosal borne
Craddock class III define
a combination of hard and soft tissue coverage
tooth supported dentures - features
transmits load via periodontal membrane
allows supported denture base to feel like the natural dentition
is more comfortable for patient
protects soft tissues from trauma
mucosal supported dentures - features
must cover as large an area as possible
allows denture base to move slightly
- possible damage to adjacent gingival margins
Function of rests in RPDs
components which provide support for denture from vertical opposing forces
What material is usually used for rests
cast metal
Types of rests used in RPDS
cingulum, occlusal or incisal
Why are large rests more suitable than smaller rests?
they can direct force down the long axis of the tooth
benefits of occlusal rests
prevent movement of the RPD towards the mucosa
assist the distribution of occlusal load
prevent over eruption of unopposed teeth
can provide indirect retention
features of incisal rets
used mostly on lower anterior teeth
poor aesthetic appearance
may interferer with incisal occlusion
Cingulum rests - features
preparation required if prominent cingulum not available
most commonly used on canines
aesthetically superior to incisal rests
less likely to breakage than incisal rets
applies stress at a lower level
The default position to place a rest for a bounded saddle is…
immediately adjacent to the saddle
The default position to place a rest for a free end saddle is…
NOT immediately adjacent to the saddle
Rest position for tooth supported bases
Should be placed on the tooth surface nearest to the base
Rest position for Craddock Class iii bases
should be placed on the tooth surface which is not next to the base
- opposite side of tooth from saddle area
possible consequences of rest seats
destruction of tooth surface
exposure of dentine
loss of occlusal stop when denture is not worn
Define ‘retention’ in reference to RPD design
the resistance of a denture to vertical dislodging forces
How can retention be achieved in an RPD?
mechanical
- clasps
muscular
- shape of the denture
physical
- mucosal coverage
indirect retention - define
resistance to rotational displacement of the denture
What is a denture clasp?
a metal arm that, when in position, contacts the tooth preventing removal of the denture base
where are denture clasps placed?
below the undercut of a tooth
where are undercuts found?
below the most bulbous part of a tooth
how are undercuts identified?
from surveying the cast
Give the name for a gingival approaching clasp
I-bar clasp
What is a gingivally approaching clasp?
a clasp that approaches the identified undercut via the gingival margin
what is an occlsually approaching clasp?
a clasp that approaches the identified undercut from above the maximum bulbosity of the tooth
types of occlusally approaching clasp
self reciprocating class
single arm clasp with separate reciprocating arm
depth of undercut required to place a clasp in a CoCr framework
0.25mm
Give examples of indirect retainers
major connectors
minor connectors
rests
saddles
denture base
What is a connector?
the rigid part of a denture base that unites other components
ideal features of a minor connector
rigidity
covers as little gingival tissue as possible
crosses the gingival margin at right angles
- to maintain gingival health
Minor connectors - function
joins components such as rests to the major connector
provides indirect retention by resisting movement about the axis of rotation
major connectors - ideal features
be ridges
avoid covering gingival margin s
be comfortable with as few edges as possible
types of maxillary major connectors
palatal plate
posterior bar
anterior plate
mid palatal plate
horseshoe bar
horseshoe plate
common connector choice for Craddock class 1 cases
bars
connector choice for Craddock class 2 cases
plates
types of mandibular connectors
lingual bar
dental bar
lingual plate
sub-lingual bar
lingual bar with dental bar
RPI system use cases
distal extension RPDs
- Kennedy class 1 and class 2
Which components make up an RPI system
mesial rest
proixmal guide plate
gingival approaching I-bar clasp
Function of the RPI system
used in free end saddle designs to prevent stress on the last abutment tooth
