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Anatomy of edentulous maxilla and
mandible
- First of all I want to tell you that this lecture is veryinteresting lecture and as DR said it is very important to
understand this lecture very well . only study it well .
- Denture- bearing Area ( DBA) :
We will discuss the anatomy of supporting areas of completedenture
- In the maxilla we call denture bearing area Denture
foundation but in the mandible we call it Denture Basal
Seat .
- In any denture we have two types of area :
1. Stress bearing areas or supporting areas
(provide support to denture )
2. Peripheral or limiting areas (determine the
periphery of the denture )
- Maxillary denture foundation :
1. It is made up of bone of hard palate and RAR
(residual alveolar ridge) covered by mucus
membrane .
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- may contain glands , fat , mucle fibers.
- It transmit blood and nerve supply to the
mucosa.
- It attached to bone by periosteum
- Very important notes :
1.The support of complete denture relies on two things
:
- type of bone of denture-bearing area.
- the thikness and consistency of submucosa :
1. if submucosa is firmly attached to bone so itcan withstand the pressure of denture --------
good for support
2. if submucosa is thin and loosely attached to
bone so soft tissue will non-resilent , and
mucus membrane will be easily traumazied
----- poor support.
2. soft tissue is very important for support of complete
denture .
so the arragment finally is :
mucosa----- lamina propria ----- submucosa----
periosteum ----- bone
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- Hard palate :
1. It is formed by the palatine processes of the two
maxillae and palatine bone .
2. It covers with soft tissues varying in thickness.
- Median sagittal suture :
1. It is the junction between two maxillae.
2. We consider it relief area because soft tissue
that cover it is thin although madian sagittal
suture is on the palate but we consider it as
Relief area .
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3. Relief area : it means that fitting surface of
denture or the base of the denture doesnt have
intimate contact with this area so we provide a
little space for relief .
- Posterior palate :
We cosider it primary stress-bearing area ( it
means it provides the main support to complete
denture during function )for two reasons:
1. The submucosa of soft tissue is firmly attached
to bone .
2. Posteriotr palate is perpendicular to vertical
forces and it is resistant to resorption.
The submucosa of posterior palate is mainly
contain minor salivary glands.
- Anterior palate (rauge ) :
It is mainly composed of fat tissues so this
increase the displace ability .
We consider it as secondry stress bearing area fortwo reasons 1. Soft tissue is more displaceable
3. Rugae is inclined so inclinations of this rugae are
not perpendicular to vertical forces.
- Residual alveolar ridge (RAR) :
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1. Shape and size change after tooth extraction
due to resorption if the patient wear denture or
not .
2. The resorption is a physiological not
pathological process .
3. The rate of resorption : it continues forever
from time of extraction until patients death(allah yrhamo )
4. The rate of resorption in the mandible is 3-4
times higher than in the maxilla and this is the
reason why in most cases we suffer from
supporting problems in maxillary arch .
5. Most of resorption happen in the first three
months of extraction after that the rate of
resorption declined but it continues of
significant amount until first year after that
resorption happens with lesser rate .
6. Direction of resorption in maxilla it happens
upward ,backward , inward because there is
a palate which is resistant to resorption so most
of resorption happened facially so
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- the labial wall of the ridge goes backward
- the lateral wall of the ridge goes inward
-the vertical height shorten
the net result of that resorption is :
1. smaller maxilla
2. lack of cortical bone so we will have spaces in
the bone we call this type of bone cancellousbone (trabecular, spongy )
7. soft tissue is firmly attached to bone and it is
perpendicular to vertical forces but we consider
crest of RAR secondary stress- bearing area
because the lack of cortical bones .
8. slopes of RAR provide little support because
they arent perpendicular to vertical forces
(inclination ) and we have what we call it muco-
gingival folds ( junction between keratinized and
non-keratinized mucosa )
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- Note:
sometimes in tuberosity area we can find cortical
bones this is why in some textbooks they consider
tuberosity as primary stress- bearing area.
-Types of RAR and palate :
Please refer to the pic on the slides from left to
right i will explain the pictures.
1. The first picture on the left :
This is the most favourable types of
palate(horizontal palate) because it provides
good support, stability , retention.
We can see well-developed ridges .
The arrow
indicate to
Muco-buccal fold
or
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2.The one on the right :
v-shaped palate it is good for stability (can resist
displacement during function ) but adhesion and
cohesion are reduced so (good stability ,
reduced retention)
3. The second one in the left corner :
We can see resorped ridges and more
displacable soft tissue
Poor retention because reduced surface area
Poor stability because no resistant to
retentional forces
Poor support because most of the bones are
lost
4. The last one :
We can see developed ridges but we have
undercuts , if we have undercuts we have the
following :
If undercuts are mild ---- good for retention
If undercuts are moderate to severe specially if
bilateral ----not good for retention either we
need to do relief of the denture or surgical
reduction of the ridges to avoid trauma and loss
of peripheral retention.
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- Incisive papilla :
1. It covers incisive foramen or canal .
2. Indicator of amount of resorption
If incisive papilla is closed to the crest of the
ridge this indicate that significant amount of
resorption happened
If incisive papilla is still higher than crest of RAR
this indicate that the ridges are still good (little
resorption)
3. It is considered as relief area
4. It is helpful in setting of teeth
- Maxillary tuberosity (area posterior to third
molar) :
1.Supportive area
The arrow indicate to :
Incisive papilla Not incisive
foramen why???
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2. May hang down and need surgical removal
3. Could be fibrous or bony enlargement
- Other relief areas:
1. Sharp spiny processes (it happens because of
the resorption of the bone and we should relief
the denture beneath it )
2. Torus palatinus : it just bony enlargement , and
the soft tissue that cover it is thin so we
consider it as relief area.
- Anatomy of peripheral structures :
1.Labial sulcus or vestibule :
From one buccal frenum to the other .
This is picture of torus palatinus be
careful this is not osteosarcoma thisis just benign bony growth or
enlargement
It is not uncommon thats mean it is
common ( less than common)
If it is too big like this picture we
prefer surgical reduction not
necessarily completetly removal .
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The labial vestibule divided to right and left
labial vestibule by the labial frenum .
2. Labial frenum : fold of mucous membrane with
no muscular attachment , because of this we
need relief in the denture flange we call it labila
notch and this notch shouldnt be wide from
latral side to the other because we dont have
muscular attachment in this region and for our
luck as dentists (hahah) orbicularis oris muscle
its fibers are run horizontal so whe this muscle
contracts it doesnt dislodge the denture.
As we know from anatomy we know what
modiouls means
Modiouls : it is the junction between the fibers
of orbicularis oris muscle and buccinator muscle
.
3.Buccal frenum :
- Divides labial and buccal vistibues
- It could be single or double folds ( note that labial
frenum is always single fold)
- Buccal frenum should have wide notch than on
denture than labial frenum because of more
movements
- Buccal frenum moves :
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1. Up and down by levator anguli muscle
2. Posteriorly by buccinators muscle
3. Anteriorly by orbicularis oris muscle
- If we dont provide sufficient room or space for this
range of movement in the buccal frenum we will
end up with frenum ulceration .
4.Buccal sulcus or vestibule :
- From buccal frenum to hamular notch
- Its size varies depend on :
1.Amount of resorption
2.Buccinator contraction3.Masseter contraction
4. Coronoid process of mandible
- Usually this vestibule has the longest and highest
space in the upper complete denture.- Distal to it there is root of zygoma (soft tissue that
cover it is thin so we need relief the denture )
how???
During border molding we ask the patient to open
widely and move from side to side because if
buccal flange of denture was thick , opening willbe limited , trauma could happen , dislodgment of
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denture could also happen because of the
thickness of the flange .
5.Hamular notch :
1. It is the area between tuberosity and hamulus of
medial pterygoid plate .
2. It composed of thick submucosa so it is
compressible and this help in achieve posterior
palatal seal (peripheral seal of upper completedenture)
3. The posterior extension of upper complete
denture is hamular notch.
6.The vibrating line (ah line ):
- It is an imaginary line from one hamular notch to
the other
- It is 2mm away from fovea palatinae
- Fovea palatinae : small identations in the
anterior part of the soft palate formed by
coalescence of gland ducts( arrow in pic)
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- Denture extends to vibrating line or 1-2 mm
posterior to it and extends into hamular notch
7. Perygomandibular raphe:
- It extends from hamulus to the top of disto-medial
corner of retromolar pad area in the mandible
( buccinator musle when it turns medially behind
retro-molar pad area it will merge with superior
constrictor muscle of the pharynx in this raphe .
- It is very important in ID block.
- If denture manily lower is over-extended
posteriorly trauma to the raphe could happen .
- Please look at these pictures they are useful
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- This picture sammarizes every things:
Oh 25eeeran 5alsna anatomy of maxilla we will move to
anatomy of mandible (eshrabo fnjan 2hweh w rja3o 3la
tafree3) .
- Anatomy of supporting structures :
- Mandibular DBA ( denture-bearing area) =
14 cmsquare
- Maxillary DBA =24 cm square
1- Labial frenum
2- Labial vestibule
3- Buccal frenum
4- Buccal vestibule
5- Coronoid bulge
6- Residual alveolar ridge
7- Maxillary tuberosity
8- Hamular notch
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- We notice that mandibular DBA is about half
surface area of maxillary arch so this is why
maxillary dentures are more successful than
more mandibular dentures ( increase surface
area ------ better retention ).
- Crest of RAR : keratinized mucosa and
variable submucosa attachment it could be firm
or loose , it contains cancellous bone so we
consider it secondary stress bearing area .
- RAR:
1. Shape and size change after teeth extraction
due to resorption
2. Rate of resorption : it is 4 times faster than
maxilla and as we know most of resorption
happened after 3 months of extraction so we ask
the patient to visit us after 3 months to be sure
that we dont need to do relining to the denture .
3. Direction :
- In the mandible the alveolar ridge and the
base are not on the same level so after extraction
the resorption takes place in the alveolar bone
not the base .
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- In anterior area : there is no palate to
resist resorption as maxilla so ---- labial wall of
ridge resorption happened backward
Lingual wall of ridge it goes forward
Net result is RAR becomes more forward
- In premolar area : labial wall ---- goes
lingually
Lingual wall --- goes labially
But the crest of RAR stays static (in the same
place )
- In the molar region :
you dont have resorption from labial wall
resorption from lingual wall ----- labially
the net result : larger mandible ,smaller maxilla
( class III ) prognathic .
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- In this picture we can see the progressive
resorption of maxillary and mandibular ridges
makes the maxilla narrower and mandible wider.
A and B represent the centers of the ridges notice
that distance become greater as maxilla and
mandible resorb.
- We know that after resorption we will end
with sharp spines .
- Sometimes when the resorption is of
significant amount the lingual fold ( soft tissue of
In this pic we can
see resorption that
take place
In this picture we
see resorption that
take place
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floor of the mouth and submandibular gland duct
underneath it ) , so when it becomes higher than
the ridges it self it complicate the construction of
lower complete denture .
- Retro-molar fossa : it is the space between
the external and internal oblique ridges.
-The anatom of supporting structures :
1. Buccal shelf (buccal flange area ):
- Boundaries :
Medially ----- crest of RAR
Laterally ----- external oblique ridge
Anteriorly ---- buccal frenum
Posteriorly---- retromolar pad
- The mucus membrane is loosely attached and less
keratinized but because there are high amount of
cortical bone and perpendicular to vertical forces
we consider it primary stress bearing area
- Buccinators muscle fibers are horizontal so it
doesnt dislodge the denture.
Note very important :
- In lower complete denture :
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The primary stress bearing area is buccal shelf
area but
The secondary stress- bearing area is crest of RAR
2.Mylohyoid ridge :
- Obligue
- It is close to inferior border of the mandible
anteriorly
Left picture : the arrow indicate buccal shelf area
Right picture : the dotted area is the buccal shelf area that extend
from buccal frenum (A) to retromolar pad area (B) and from external
oblique ridge to the crest of the residual alveolar ridge (C)
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- It is close to superior border of mandible
posteriorly
- The mucus membrane over a sharp mylohyoid
ridge will be easily traumatized by denture base
.so we need to do relief to the denture base.
3.Mental foramen :
- Indicator of the amount of resorption if it is very
close to the crest of RAR this indication of severe
resorption.
- The mental nerve and blood vessels could be
compressed by denture base unless relief is
provided .
In the picture :
A- Canine region
B- Premolar region
C- First molar
D- Third molar
In anterior area we see that
mylohyoid muscle is close to the
base of the mandible but in
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- In some patients with severe resorption
mylohyoid muscle becomes sometimes above the
crest of the ridge
4.Genial tubercules :
- With resorption it become prominent so we need t
do relief .
5.Torus mandibularis :
- It is bony prominence
- It found bilaterally and lingually near the first and
second premolars.
- It covers with thin layer of mucus membrane so we
need to do surgical removal of these tori becausetrauma could happen to the mucosa and
peripheral seal affected also .
- Anatomy of limiting strctures :
1.Labial vestibule :
This is a picture of
torus mandibularis as
we said if too largelike this we should do
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- From labial frenum to buccal frenum
- Length and thickness of labial flange vary
- Labial frenum : it contains band of fibrousconnective tissue that helps attach the orbicularis
oris muscle so labilal frenum is quiet sensitive and
active .
2.Buccal vestibule :
-From buccal frenum to retromolar pad.
- The extent of buccal vestibule is influenced by the
buccinator muscle .
- The buccal flange may extend to the external
oblique ridge up onto it or over it depending on thelocation of muco-buccal fold and sharpness of
external oblique ridge.
- Posteriorly the buccal vestibule must converge to
avoid displacement by the contraction of masseter
muscle ( anterior fibers of this muscle run outsideand behind the buccinators muscle ) so we need to
do relief .
- Distal extension :
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1. Retromolar fossa : it is the area between
external and internal oblique ridges
If the impression is overextend it can cause
soreness and displacement of denture because
pterygomandibular raphe during movement it
will dislodge the denture anteriorly
2.Retromolar pad :
-It is pear shaped soft tissue pad located at distalend of RAR
- It contains thin non-keratinized mucosa
- Submucosa contain glandular tissue and muscle
fibers (pterygomandibular raphe and tendon of
temporalis )
- The denture should cover to 2/3 over the
retromolar pad .
- Notice when buccal shelf turns to cover retromolar pad
area (in that area we have only buccinators muscle)behind buccinators there is masseter muscle so when the
The arrow indicate toretromolar pad area and
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patient bites masseter muscle contracts and become
wider , it pushes buccinators muscle . so in some patient
we need to do relief to flange of denture and we do this
during border molding we press on tray and ask the
patient to bite aganist our fingers so masseter muscle
contarcts and we call this ( masseteric notch )
- In other patient we have tense mentalis muscle so we
cant provide thick flange in this area it will dislodge so
the flange of denture should extend to muco-buccal fold
and some fibers of buccinators muscle will be under the
denture.
3. Lingual border :
- The lingual tissues under the tounge are less resistance
than labial and buccal and ar easily distorted.
- Mylohyoid muscle :
1. It forms the floor of the mouth
2. It originates from mylohyoid ridge and inserted to hyoid
bone
3. The ridge more prominent posteriorly so denture flange
must parallel to mylohyoid muscle to avoid sorness
(pain) , peripheral seal and tounge rests on the flange
4. Retromylohyoid fossa :
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- It located posterior to mylohyoid muscle and it is
bounded with
Retromylohyoid curtain
- The denture must extend to this fossa ( S-curve
configuration )
5.Retromylohyoid curtain boundaries:
- Posteriolaterally : superior constrictor
- Posteriomedially : palatoglossus muscle
- Inferior wall : overlies submandibular gland
- Medial pterygoid muscle can cause bulge in the
wall of the curtain as masseter dose with
buccinators
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- The following picture may help you in
understanding :
- Finally i advice you to refer to my tafree3on my-
toothy because there are alot of pictures
In this picture sorry the letters
are inverted
B : buccinator muscle
M: masseter muscle
MP: medial ptyregoid
PR: pterygomandibular raphe
RM: ramus of the mandible
SC: superior constrictor muscle
RMC : posteriolateral portion of
retromylohyoid curtain formed by
the mucus membrane covering
SC. If pic is not clear please refer
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