RPD Flashcards
support
resistance to occlusally directed load
Kennedy class I
bilateral free end saddles
Kennedy class II
unilateral free end saddle
Kennedy class III
bounded saddle
Kennedy class IV
anterior bounded saddle crossing the midline
craddock class 1
tooth borne - teeth provide hard tissue resistance to occlusal loading
craddock class 1
tooth borne - teeth provide hard tissue resistance to occlusal loading
craddock class 2
mucosa borne - large soft tissue coverage provides resistance to occlusal loading
craddock class 3
tooth and mucosa borne - reduced teeth and large edentulous spaces
why is tooth support better
transmits load through PD membrane protects soft tissue comfortable more natural likely to stay in close contact with supporting structures
disadvantages of mucosa borne
may damage gingival margins
more likely to displace
types of rest
occlusal, cingulum, incisal
retention
resistance to vertical displacement of denture - given by clasps
best teeth for support
those with large roots i.e. molars then canines
clasp thickness
CoCr 0.25mm, Au 0.5mm, Stainless Steel 0.75mm
2/3s of clasp
should be above survey line
terminal 1/3 of clasp
should be below survey line engaging the undercut
guide planes
bounded saddles
2 or more parallel axial surfaces on abutment teeth
can occur naturally
more often need to be prepared
large the guide surface the more efficient it is
limit tilt and improve stability
frictional retention
guide planes
indirect retention
resistance to rotational displacement of denture
examples of indirect retainers
major connectors, minor connectors, rests, saddle, denture base
RPI system
mesial rest
proximal plate (adjacent to saddle) guide surface of 2-3mm
I-bar clasp (gingivally approaching) at greatest prominence of tooth contour
open vs closed major connectors
open - greater clearance but reduced retention
closed - more contact, greater retention, guide planes but increased irritation
plates
- can be thin in x section and maintain rigidity
- only recommended in mandibular arch when there is no space for a bar as they will cover gingival margin
- when less tooth support plates with confer mucosal support
- 0.5mm thickness
bars
- less coverage of gingival margins
- must be thick to maintain rigidity
- 2mm thickness
- default connector in mandibular arch
lingual bar
need 8mm space:
3mm distance from gingival margin
4mm height of bar (thickness)
1mm above floor of mouth
minor connectors
join components such as rests to major connector and transfer functional stresses to and from the abutment teeth
sub lingual bar
4mm thickness
path of insertion
path followed by denture from first contact with teeth/tissue until it fully seats
common path of displacement
90 degrees to the occlusal plane (horizontal)
why do we survey
to determine the path of insertion
why do we tripod
records common path of displacement as well as insertion and withdrawal so it casts can be relocated to here
how to survey
position cast on surveyor table
orientate to common path of displacement
place ruler on cast
tripod
use analysing rod to eyeball cast for undercuts of abutments and associated soft tissues
use graphite rod to to mark upper and lower survey lines on teeth and soft tissues
what surveyor do we use
ARCON - average value arcon
survey lines
indicate the extent of the undercut - below the line must be used or blocked out
