RPD Design: saddle & support Flashcards
what is a saddle area
edentulous area - where the replacement teeth will sit
what is a denture base
is it the connecter
what is the flange
it is the replacement tissue
it extends from the alveolar ridge into the vestibular sulcus
what is the system of design with dentures
will a prosthesis be made?
what type of prosthesis?
what teeth will be replaced and why?
how will occlusal loading be resisted by the denture?
how will denture be retained
how will the denture resist horizontal movement
how will the components be joined
what are the basic system of design steps
saddles support retention bracing and reciprocation connector
what is kennedy classification
an anatomical classification that describes the number and distribution of the saddle area
what teeth are ignored in kennedy classification
third molars
unless they play a direct part in denture design
what saddle defines classification
most posterior
what is class I KC
bilateral free end
what is class II KC
unilateral free end
what is class III KC
unilateral bounded
what is class IV KC
anterior bounded (crossing midline)
what is each additional saddle area referred to as
a modification
what is meant by support
a term used to describe the resistance of a denture to occlusal directed load
what are the options for resisting movement towards the tissue
utility of hard tissue
spread the load over a large surface area
what is tooth support
prevents/resists movement, directs load through PDL of adjacent teeth
what is mucosal support
needs a large surface area so that the load is distributed over a wide area
what is craddocks classification
simple classification based on support for a removable partial denture
only gives the type of support and does not tell anything about distribution or number of the teeth
what is class I CC
tooth support
they provide a HARD tissue resistance to occlusal loading
what is class iI CC
mucosa
a large coverage provides resistance to occlusal loading
what is class III CC
tooth & mucosa
a combination of hard tissue and large coverage when there is a reduced number of teeth and a large edentulous saddles
describe tooth support
transmits load via the periodontal membrane
allows the supported denture base to feel like the natural dentition
is more comfortable for the patient
protects the soft tissues from trauma
is likely to stay in close contact with its supporting structures over a period of time
describe mucosal support
must cover as large an area as possible - reduction of the occlusal table
allows the denture base to move slightly which could result in potential damage to adjacent gingival margins
why does the denture move with mucosal support
it is compressive
what should first be considered in terms of support for dentures
tooth support
what are the best teeth for support
those with the largest root area depending on the health of the PDL attachment
how much can a healthy tooth potentially carry
its own load plus one and a half similar
how much more is periodontal membrane for support than the mucosal coverage of a lost tooth
4 times
how is tooth support provided
by metal alloy rests on the surface of adjacent abutment teeth
how do the rests transfer the load
down the long axis of the tooth
what are rests
the components which provide support for the denture from vertical forces
how are rests described
by the part of the tooth they contact - cingulum, incisal, occlusal
what are rests made out of
cast or wrought metal
what are the rests best used as a part of
cast metal denture framework
what do rests do
they oppose movement of the base towards the tissues
why is incorporating rests into acrylic resin a problem
due to low base strength
placing a metal component potentially weakens the acrylic surrounding it
what should occlusal rests be like
large rests are recommended as this can direct force down the long axis of the tooth
what are incisal rests
extended from denture base framework used mostly on lower anterior teeth poor aesthetic appearance may interfere with incisal occlusion not recommended on wear facets
what are cingulum rests
extended from the denture base framework
unless prominent cingulum is available a preparation is required to provide a vertical stop
used most on maxillary and mandibular canines and can be used on maxillary incisors and laterals
aesthetically superior to incisal rests
apply stress at lower levels - less rotational forces
less likely to breakage
describe metal framework base
CoCr
rigid and strong
all rests are integral to the base connected to the major connect directly or by minor connectors
the base is produced by casting using a lost wax technique
describe PMMA
flexible (not rigid) and poor strength
rests are incorporates mechanically into the base
any load is resisted by the rests through the denture base placing an internal stress on the base material
rests for support within an acrylic base are the exception rather than the rule although it can be used when opposing forces are light e.g complete denture
what do tooth support rests do
prevent movement of an RPD towards the mucosa
assist in distribution occlusal load
direct retentive elements to work in a planned manner
prevent over-eruption of unopposed teeth
provide bracing on anterior teeth
determine the axis of rotation for free-end saddle RPDs
what are additional uses of rests
reciprocation
indirect retention
what is the purpose of a rest
support denture against vertical load
why are rests often placed on the occlusal surface of a tooth
will direct occlusal forces of a tooth down the long axis fo the abutment teeth
what is the default position to place a rest for a bounded saddle
immediately adjacent to the saddle
additional rests may be incorporated
position may have to be changed depending on the opposing dentition
where is the rest placed on a free end saddle
not immediately adjacent to the saddle
we do not want to compromise the abutment by having axial torus on it
we try to mitigate this by having the rest on the medial surface of the abutment tooth
where should the rest be positioned/placed in tooth supported bases
the support should be on the tooth surface nearest to the base
where should the rest be placed for tooth and mucosa supported base
the support should be on the tooth surface which is not next to the base
where should you avoid placing an occlusal rest
in an occlusal centric stop
the denture will be uncomfortable and interfere with the occlusion
what are the possible consequences of rest seats
loss of occlusal stop when denture is not worn
destruction of tooth surface
exposure of dentine
what is mucosal support dependent on
as large an area possible of mucosa being covered
what should be taken account when making up dentures with mucosal support
since soft tissue is compressible it is inadvisable to place the base within 3mm of the gingival margins are, this will place pressure at the gingival margin
what is the Every partial denture design
mucosa borne denture which restores the dental arch; with contact points between the denture and abutment teeth
what is put in every partial design to ensure most distal tooth does not drift posteriorly
a wire stop is conor-orated
what is not covered by the Eveery denture design
gingival margins
what is an issue with tooth and mucosal support
different in compressibility between periodontium (vertical displacement of tooth attachment within its socket) and the mucoperiosteum
what does a uniform foundation allow in a denture
spreads load evenly and rest or sink depending on compressibility
