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Removable partial denture
24/2/2013
Abeer Abu sobeh
3esam-el3alem
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Prosthodontics II: lec IV.
Title:Maxillary Major Connectors for Metal Framework RPDs.Mandibular Major Connectors for Metal Framework RPDs
The references for this lecture
Chapter 2, Stewarts Clinical Removable Partial Prosthodontics,4th Ed, 2008 (pages 19-36).
Chapter 5, Removable Partial Denture Design - Outline Syllabus,5th Ed, Kroll et al, 1999 (pages 33-45).
Today we are going to be talking about the major components of RPD
structure before you learn how to design, you need to know the components,
if youre going to build a building you need to know the materials that youll
use ,you need to know the structures or components of the building whichyou are going to design ,for the partial denture its similar, you need to
understand the major components and the different choices that you have
for each of this components when you fabricate it ,so the first thing we are
going to learn about :
Components of the metal framework removable partial denture:
The major connector: Its like a skeleton for the partial denture, it connects various parts
together and it transmits the force so that the functional load is
distributed on both mucosa and teeth.
It always extend from one side of the arch to the other.
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It provides support. When the patient bites down on one side it
prevents the rotation of the denture and keeps it in place.
Many patients often come to us in the removable prosthodontics Clinique
and they are missing 2-3 teeth on one side ,and they asking for
removable prosthesis, they say thats fine its only going to be on that
side right? we say no we never make removable prosthesis on only one
half of the patients mouth, if its removable by definition for safety
and for structural reasons:
1)The first reason is for structural, removable prosthesis is not attached
to the adjacent teeth like a bridge, it has to cross the arch for stabilityand retention, remember not all of this prosthesis have a lot of tooth
support , so itll distribute the support from one side to the another .
2)The other reason which is for safety: even if technically we can make it
of one side from the patients mouth we avoid it, because it is so small
,and the problem is if the patient will leave our Clinique he might sneezes
,yawns ,be in an accident ,this might dislodged so the patient can swallow
it or worse aspirate it if it gets lodged in his trachea. So we never make
unilateral or one side partial dentures, they always cross the arch, when
they cross the arch they give us additional stability retention and
support when it cross the palate we get some support from the palate in
addition. Depending on the different components that the major
connector has it provides stability and to some degree it provides
support, like we said theres a skeleton and theres backbone over
prosthesis but we need to have specific requirements when we make this
prosthesis, first of all the materials need to be compatible, the material
that we use we call it: cobalt chromium and there are other alloys that
we can use (like: nickel chromium, high noble alloys -gold alloys-
although it is expensive but it was very popular in the past , titanium
which is difficult to fabricate).
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-The one which is economically and technically most usable it is: cobalt
chromium and nickel chromium, but in general we avoid nickel chromium
because approximately 1/20 people has nickel sensitivity.
Notes:
o Acrylic partial dentures for strength reasons need to be at
least 2-3 mm thick in the cross of the base plate.
o Metal framework partial denture could be make as thinnest
0.5 as routine and could be 0.3-0.4 if it covers the entire
palate.o if the major connector does not reach to the cingula then
it has to be 6 mm away from the gingival margin .
o The distance between minor connectors in the maxilla
should be at least 5 mm (the space needs to be large enough
so its self cleansing ,if its small the food will accumulate in
this area which might cause caries, gingival inflammation ,
and irritation to the patient).o We should cross the gingiva at right angles.
o In the anterior part of the mouth the metal plate -the
major connector often ends in the rugae area.
o The function of rugae area: Phonetics, taste stimulation,
maybe have something to do with nursing in mammals so it
stimulates lactation.
o The posterior border shouldnt end to the vibrating line
because the soft palate is movable.
o The anterior and posterior borders should cross the midline
at right angle so it causes the least irritation thats
possible.
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So, the principle functions for the major connector: Unification & rigidity.
Major connectors has many requirements, the doctor mentioned some of
them: it must be rigid, unifies the different parts together, it shouldnt be
irritating to the tissues like marginal gingival and midpalatine raphae,mandibular tori or to the tongue, shouldnt be too thick , should across from
one side to the other and thats only in the maxilla , because in the mandible
this cant be possible due to the presence of the tongue .
o Rigidity is necessary, if a force is applied on one side of the
prosthesis, it should be distributed to all parts, because as we knowthe edentulous area was not designed to support the occlusal force .
o In a partial denture, we want to distribute the force over a large area
as much as possible, or to other teeth if we can .
Maxillary Major Connectors:
Major connectors in the maxilla have different designs , due to the anatomy
of the maxilla and the variation of Kennedy classes that guides the design of
the prosthesis.
Depending on the class we have (the location of the edentulous spaces),we
have to decide what type of design is the suitable one , and if we need to
make either broad or small major connector . so its not only the coverage
that is important , but also the thickness .
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In maxillary RPDs we place bead lines ( ONLY IN MAXILLA) at the edges
of the major connectors, The bead line is something you scraping in the cast,
so the material of the denture will go in and it will comprise this area it can
be in anywhere in the maxillary denture ,but we dont place bead lines in themandible. we make a groove which usually about 0.5-1 mm deep and wide and
the metal will go inside this.
Bead line hasnt to be between the junction of the movable and non-movable
parts of the soft palate, it provides mechanical seal to food and saliva ,
prevents things from going in and out underneath the denture, indicates the
technician where to stop trimming , gives strength to the borders , it has a
retentive function specifically in complete dentures because theres an extra
thickness at the edge of the border so it will strengthen it ,and the denture
Will be less prone to breakage.
and in acrylic RPDs it counteracts the contraction that occurs during
setting and cooling of the material .
The depth is usually no more than 0.5 1 mm , because compressing the
tissue to this depth causes no harm to them , if deeper it will harm the
tissues .
As it gets close to the gingiva it becomes shallower and shallower , alsoit should be thin in the midpalatine suture area in order not to irritate
these areas .
We try to finish the edges of the denture ( bead lines ) behind the
rugae not in front of it , because it would be more comfortable for the
tongue , but if the denture ends in front one of the rugae this makes it
less comfortable and more thick . So in the first case the tongue will
pass from the major connector to the rougae , it will keep sliding as if
the border of the partial denture isnt there .
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The junction between the major connector and the acrylic is called
the finish line, in the maxilla it differs in location between the
fitting surface and the polished surface . If they were both on the
same level, the metal will be very thin and might break .
In polished surface: its closer to the teeth . In fitting surface : its
closer to the palate . at the fitting surface we want to cover as much as
we can from the ridge , we might need to reline the base again in the
future .
o Note: major connectors can be designed to add a tooth to the
prosthesis later, this is called planning for future failure.
TERMINOLOGY :
Three main terms: a palatal bar , a palatal strap and a palatal plate .
o Bar > strap > plate , as we go from bar to strap to plate , the shape
gets thinner and broader .
o Bar are more common in mandibular partial dentures , not used
much in the maxilla . Bar is less than 8 mm wide ( lateral dimension
, not thickness ) .
o Strap is between 8-12 mm .
o
Plate is greater than 12 mm wide . ( this is for the maxilla )
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Mid palatal strap (posterior):
One of the most common major connectors used in the maxilla, usually
used in bounded saddle (class III), missing premolars and molars at
one or both sides it has a mid-palatal strap that extends from one side
to the other for retention and rest.
So its used for tooth borne prosthesis. And in some rare cases can be
used in tooth tissue borne prosthesis.
Should be 8-12 mm wide. Thickness of the strap is 1.5 mm .
o Note: Usually the anterior posterior width is proportional to the
degree of support required, the more the support the greater
the area we need to cover.
o We usually thicken the center to give it more rigidity.
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Anterior palatal strap horse shoe , U shaped :
It covers the edentulous area, goes around anterior part of the palate
and then goes back.
Preferred by patients, not by dentists. Patient like it because it frees
the palate, for taste and temperature sensation and its not irritating
for the tongue . Dentists dont like it because it is more flexible,
especially in tooth tissue borne prosthesis.
Its indicated for tooth borne when anterior and posterior teeth aremissing but in different areas, and specifically indicated when a palatal
torus cant be removed or covered. so for large Kennedy class 1 ,
bilateral distal extension and with presence of torus , I want a lot of
coverage and support but still cant cover the torus , horse shoe
design is the suitable one .
o Note: we may have combinations of: anterior posterior, mid
posterior and so on of these designs.
o Problems with this design : relatively flexible , poor rigidity and
is often misused ( many dentists use it routinely) .
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Anterior posterior palatal strap:
Relatively popular design, covers large surface area, its a rigid design
because it has not only an anterior part but also a posterior one,
middle part of the palate area is cleared to maintain sensation.
Its indicated for both tooth & tooth-tissue borne prosthesis , also
useful if the torus is the in center of the palate and cant be covered .
o It covers less area than modified palatal plate, therefore it
provides LESS support than plate.
If the torus is large, extending to the vibrating line, horse shoe
design is indicated .
If the torus is small and just in the center, anterior posterior
palatal strap is indicated .
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Although it clears p
many edges In the c
borders are someti
coverage.
o Note : Palatal
covering the
.
Modified palatal pl
o In this design
edentulous ar
o It is broader
(anterior and
o Indicated mai
rt of the palate, irritation occurs du
onnectors design. So this is an examp
es more irritating than the thickness
plate can be either complete full or
hole palatal area or only a part of it ,
ate:
, we cover areas that we need to reac
as.
han 12 mm, has extend and flat two b
osterior), it gives a lot of support.
ly in tooth tissue supported prosthes
Torus
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to having
le where
or the
modified ,
respectively.
the
orders
is .
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A complete full pa
o It does not nec
than 90 % of it
o The patient do
reaches the vib
o Its indicated f
extensive class
latal plate:
essary cover 100 % of the palate , but
. the figure below is an example for t
s not feel any borders with this desig
rating line and the teeth in all other a
r very large edentulous areas , exten
IV or class III with many modificatio
H
is
fo
th
it
co
pl
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usually more
is .
n , usually it
reas .
sive class I ,
ns .
ere everything
covered, except
a small area in
front.But still
considered a
plete full
te.
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Split major connector :
o Its a rare design, not seen any more in clinics.
o The objective is for stress relief between the retention and the
support.
o Used when rigidity is undesirable, mainly in maxillofacial
prosthodontics , in such cases part of the palate is gone , the sinus
is open , this area is very movable and there isnt much support that
if I connect it very rigidly to the few remaining teeth , everytime
the patient bites down , a lot of force is applied on the remaining
teeth , which with time may lead to extraction of these teeth .
So we just need a design that keeps the denture in the patients
mouth, without a lot of rigidity .
o This is achieved by splitting the major connector, making it more
flexible.
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Palatal Bar:
o Bars are rarely u
o Used in very sma
Or if theres a v
o Its thick, and n
Notes:
o Each of these designo Complete full palatal
rigidity .
o However , we dont w
prosthesis , due to o
considerations . so o
o In the maxilla , we te
mandible its the oppo Bars in the maxilla ar
thats why they are t
are not exposed to t
sed in the palate, because of its thick
ll edentulous areas, like in Kennedy cl
ry large torus, and we have to work a
rrow.
s provides rigidity and support in diffplate is the one that provides best s
nt to cover the palate everytime we
al hygiene considerations and prepar
ly when its really needed .
nd to use plates and straps more than
site .e exposed to the dorsum surface of t
hinner than the lingual bars in the ma
e dorsum surface of the tongue .
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ness.
ss III .
ound it .
rent ratios.pport and
re making a
tion
bars , in the
he tongue ,
dible , which
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MANDIBULAR M
o The first choice
bar .o Lingual bars are
tongue and beca
of the mouth is
In the mandible ,a
present :
There should be a dist
at least 3 mm for gingiv
have this distance , the
cingulam . so the only t
the gingival margin or c
leaving a 0 , 1 ,2 mm spa
allowed , because itll c
The key nu
The key nu
connector d
6 mm away
JOR CONNECTORS :
for mandibular major connectors is t
made quite thick, because they are b
use the distance between the gingiva
mall, making it difficult to place a pla
ar is placed unless the following co
nce between the bar and the free gin
al health and oral hygiene . if its not
we have to cover the whole gingiva u
o choices are either keep a distance
ver the gingiva up to the cingula , me
ce between the bar and the gingival m
use irritation and gingival recession .
ber in the mandible is 3 mm .
ber in the maxilla is 6 mm, if the major
oes not reach to the cingula then it has t
from the gingival margin .
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e lingual
low the
nd the floor
te .
nditions are
gival margin,
ossible to
p to the
way from
ns that
argin is not
be
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o Lingual plates creates problems in oral hygiene especially in small narrow lower
anterior teeth .
o In the mandible , there are no bead lines . however , we usually relief (wax
spacer ) underneath the major connector ,because theres a certain degree of
motion in the mandible , and depending on either the case is tooth borne Or
tooth-tissue borne, the thickness and location of this relief varies , notice
that in tooth borne the movement is up and down only , in tooth tissue borne
theres rotation .
o In tooth-tissue borne prosthesis , in addition to the lingual bar ,indirect
retention is needed . so there will be extension that goes from the lingual bar
to the lingual surfaces of the teeth to prevent rotation. So , another option
when we cant do lingual bar is lingual plate , but it has its contraindications , if
theres spacing between the teeth ( it would be unaesthetic because its going
to appear through these spaces), if theres crowding.
Double lingual bar ( kennedy bar ) :
Is two lingual bars , one on the cingulam surface and one below .
Labial bar :
Instead of extending the major connector from the lingual, we extend it
from the labial. And thats when mandibular tori are present.
However , its considered the very last choice because the longer the bar
the more flexible it is and the more irritating it is for the patient.
And the rule of 3 mm away from the gingival margin also applies here (
from the labial side ) .
Its indicated when the lower anterior teeth is so severely retroclined ,
or theres a large lingual torus .
Hinge / Swing-lock design , dental bar , sublingual bar . These are other types
of mandibular major connectors .
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No straps in the m
For strength , the B
gingivally .
7 mm distance is nee
frenum , and additio
which equals 8 mm .
that means to place
margin to the floor o
bar , if we have 8 m
between the bar and
the bar itself , 1 mm
(very important )
These measurement
probe , before makin
ndible .
r in the mandible must be 4 mm in wi
ded between free gingival margin and
al 1 mm for the free movement of th
bar we have to measure , from the f
f the mouth , if its less than 8 mm we
and more , then we can ; 3 mm is the
the free gingival margin , 4-5 mm for
for the free movement of the lingual
are done in the patients mouth with
g the design .
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dth occluso
the lingual
frenum ,
ee gingival
cant do a
distance
the width of
frenum .
a periodontal
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Superio inferiorly it
Advantages of lingua
gives a degree on ind
The shape of a Lingu
and rounded at the t
attached to it that r
possible , the botto
Double lingual bar is
reduce the amount o
the teeth . however
5 mm , thickness is 2 mm .
l plate : gives support because it sets
irect retention ( there are rests atta
al bar is half bear shaped , broad at t
op . A lingual plate is a lingual bar with
eaches the cingulam , so the top part
part is rounded for strength & suppo
indicated when there are open embra
the metal that would be shown thro
its irritating for the patient .
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on the teeth,
hed to it).
e bottom
a plate
is tapered as
rt .
ures to
gh between
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Hinge/swing lock design is a ( lingual bar + lingual plate + labial bar ) . it
locks the teeth from lingual and labial surfaces , its popular with
extensive kennedy class I . its used for added retention , we want
retention from all anterior teeth not only canine . its not very common
these days because we have implants .
Done by: Abeer Abu sobeh