Download - Prostho IV - Lec 3 - Review of the Relevant Anatomy for Maxillary and Mandibular Dentures
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Review of the relevant anatomy for
maxillary and mandibular dentures
Razan Tanous
Khalid Al-Hamad
6-10-2013
3
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Review of the relevant anatomy for maxillary
and mandibular dentures
Mucosa: stratified squamus epithelium and connective tissue (lamina dura)
Submucosa : connective tissues made of dense to loose areolar tissues- if firmly attached : withstands pressure
- if loose, thin, traumatized, mobile, flabby: won't be stable to withstand
pressure {not resilient}
Masticatory Mucosa (keratinized) : hard palate, residual ridges, residual attached
gingival
Hard palate:
- keratinized.
- mid palatine suture : submucosa is extremely
thin, requires relief!
- primary support area: horizontal portion of the
hard palate
- secondary support area: rugae area (set at right
angle to the residual ridge)
The palatal gingival vestige: remnants of the lingual
gingival margin, it is the remains of the palatal
gingival ; after tooth extraction the position of the
vestige remains relatively constant (static), the
same as the incisive papilla. This can be a very
helpful pointer for posterior tooth positioning
during denture construction.
there are some techniques that are based on
these static marks, but we won't be using any of them in our fourth & fifth
years!
Residual Ridges:
1. Mucus membrane: it's keratinized and firmly attached the submucosa: devoid the glandular tissue. Dense collagenous fibers.
It's relatively thin and not sufficient to provide support for the denture
base.
2. Crest of the ridges: it is prone to resorption, and of the secondary supportarea!
3. Inclined facial surfaces: it loses its firm attachment, so it offers little supportand cannot be used as a support area.
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The Fovea Palatine:
1. Two orifices one on each side of the palatalmidline.
It is the coalescence of several mucous glands,
and it's ALWAYS located in the soft palate!
2. They act as collecting ducts for a group ofminor palatine salivary glands.
The most important thing in impressions is to get the BORDERS accurately!
It's also important to get all the structures accurately; it's not an easy task to be
done accurately. But it's important to know that a denture depends on the
peripheral seal (for the primary impression), ok you need good adaptation, good
impression, no voids here and there, the choice of the material or the technique....
but this is sort of easy; to fill between the borders! But as we can see there are
many structures here at the borders that you have to get in order to have a good
final impression.
- Knowledge of the muscles and structures that produce the borders is aprerequisite to successful impression making.
- Knowledge of how to activate the muscles and locate the structures is alsoneeded.
Let's start with
them one by
one...
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These are the labial frenum
and the buccal frenum...
Then we come to the
orbicularis oris,
levator labii superioris,
levator anguli oris,
incisivus labii superioris
muscles that form the anteriorpart of the denture (and the
impression).
These structures will control
the depth and the length of the
sulcus.
Then we go to the buccinator
muscle...
Forming the distal part of the
denture (the impression).
"the lip form the ant. Part up
to the buccal frenum area"
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Now the risorius muscle,
controlling the width of that
area.
Here you ask the patient to
open wide and move the
mandible to the left and to
the right, to get the
impression of the coronoid.
The hamular notch should
be recorded here, or another
name for it is the
pterygomaxillary fissure.
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The palatine aponeurosis
which consists of different
structures this area is really
important to get, to complete
your peripheral seal, by
adapting the denture to
compress that area.
The structures are:
tensor veli palatini,
levator veli palatini,
palatophartngeus,
palatoglossus,
musculus uvulae muscles.
And there it is all the
structures are in this picture.
Let's Now Concentrate On The Posterior Palatal Seal.
We have this line making the junctionbetween the hard and soft palate
it's also called Valsalva Maneuver
so anterior to it is the hard palate,
and posteriorly the soft palate.
How do we get that line?
you ask the patient to close the
nostrils and blow through the nose
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Now the soft palate is composed
of: immovable part (just behind
valsalva maneuver) and movable
part
The line that separates them is
called the Vibrating line.
Behind this line, shouldn't be
covered for retention! Bcoz the
area there is movable
Sometimes u need to check the
compressibility of the hard palate
with a burnisher coz sometimes
the tissues there are compressible
(50% in average) so can be used
for the posterior palatal seal.
- measure the depth of soft tissue
displacement and make a depth
"not more than" 2/3rds
that
depth"; about one-half of the
displacement!
And what you do next is you carve
the cast at that area "between thehard-soft palate junction & the
vibrating line" (spoon shaped);
the deepest part is in the middle
and zero over the lines as if it
flushes all the way up!
That's how you make your posterior palatal seal.
We have several advantages of the posterior palatal seal:
1. To increase the maxillary complete denture retention by having the posterior aspectof the denture base slightly compress the posterior portion of the palatal soft tissue
(both soft and hard palates)
2. To compensate for the polymerization shrinkage of the resin so the denture base willcontact the posterior aspect of the palate and maintain the seal.
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These are the labial frenum
and the buccal frenum.
Then the lip musculature:
Depressor labii inferioris,
mentalis,
incisivus labii inferioris,
orbicularis oris muscles.
These muscles will form the
anterior area of the
impression controlling the
sulcus depth and width.
Let's start with
them one by
one...
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Then the buccinator again
Forming all the posterior
area.
Here is the masseter muscle.
it compresses the buccinator
muscle forming the
masseteric notch.
*These structures should not
be always present, what u
do is that u try to
manipulate the muscles and
try to see the maximum
action of the muscle on the
impression material, but if
you don't see these things,
this doesn't mean your
impression is not good!
The temporalis muscle.
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And also we have two
important structures forming
the gap ligually; the superior
constrictor muscle and the
palatoglossus muscle.
You get these impressions by
putting your finger on the tip
of the tongue and ask the
patient to push forward, and
you resist this push.
And we have the mylohyoid
muscle forming all the lingual
portion of your impression.
most of the common mistakes in the
lower impression is this area it's
usually short! So we have to go deep
and maximize the stability and
retention of the lower denture.
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These are all the structures
of the mandibular
impression
The buccal shelf area is important for support and also the marginal ridge and all the
other structures.
Crest Of The Residual Ridge:
1. Ridge is smaller comparing to that of the upper in a healthy mouth.2. Attachment varies considerably. In some people the submucosa is loosely attached to
the underlying bone.
3. When securely attached to the bone, the mucous membrane is capable of providingsupport for the denture. However, because the underlying bone is cancellous, the
crest of the residual ridge may not be favorable as a primary stress bearing area forthe lower denture.
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The buccinator muscle, the
mandibular raphe, the superior
constrictor, masseteric muscle,
medial pterygoid .these are the
structures that have many thingsto do with the placement and the
relations of the denture in the
jaw.
-For the buccal shelf area:The mucus membrane is more
loosely attached and less
keratinized than that covering
the residual ridge. Although the
mucous membrane may not be as suitable histological to provide support for the
denture, the bone of the buccal shelf area is covered by a layer of cortical bone. This,
plus the fact that the shelf lies at right angle to the vertical occlusal force, makes it the
most suitable primary stress bearing area for the lower denture.
- The external oblique ridge does not govern the extension of the buccal flange becausethe resistance or the lack of it varies widely. The buccal flange may extend to the
external oblique ridge, up onto it, or even over it depending on the location of the muco-
buccal fold.
-The bearing of the denture on the muscle fibers of the buccinator wouldn't be possibleexcept for the fact that the fibers run parallel to the border and not at right angle.
-The distobuccal border must converge rapidly to avoid the action of the masseter whichpushes inward the buccinator.
-The distal extension is limited by:* The ramus* The buccinator
* The pterygo-mandibular raphe
* Superior constrictor muscle
* The sharpness of the boundaries of the retro-molar fossa.
( the denture should extend slightly to the lingual into the pearl shaped retro-molar
pad).
-The retro-molar pad is a triangular soft pad of tissue. It's mucosa is composed of thin,non-keratinized epithelium.Its submucosa contains:
* Glandular tissue.
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* Fibers of the buccinator and superior constrictor.
* Pterygo-mandibular raphe.
* Fibers of the temporalis.
Because of these structures the denture base should only extend to one half to two thirds
of the retro-molar pad.
The Retro-molar Pad:
It is split into two sections. The anterior section isusually firm and fibrous, it's important for denture
support and preventing distal displacement.
The Mylohyoid Ridge:
It becomes more prominent following the extraction ofnatural teeth and subsequent resorption. This can result
in mucosal soreness beneath the denture bearing area
over the mylohyoid ridge.
When we talk about the mylohyoid muscle why do we look
for the S shape? Because of the way the mylohyoid muscle
is attached to the bone;
The retro-molar pad area is
deep, so the denture can go
slightly in, and so will be close
to the bone. (The sulcus is
close to the bone).
While here the mylohyoid
attachment is quite high, so
the denture will be away from
the bone (closer to the
tongue).
So close to the bone
posteriorly, then away
(towards the tongue), then
down closer to the bone (because the muscle attachment is low there).(IN , OUT , IN) This is the nice S shape u get on your lower impression.
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You get that S shape by properly
manipulating the tongue, but you don't
always get it, not because your
technique is wrong, but because
sometimes the anatomy is not clear (the
place of the attachment, the resorption
of the ridges). But we are talking about
the ideal situation.
"The doctor skipped many slides, but I
wrote everyth. here, so u don't have to
go back to the slides"
Notes about: The Mylohyoid Muscle:
1. It is a thin sheet of fibers and in a relaxed state will not resist the impressionmaterial.
2. Carrying the border under the mylohyoid cannot be tolerated. The contraction ofthis muscle will displace the denture.
3. Fortunately, the denture in the posterior area of the mylohyoid can beyond itsattachment because the fold isn't in this area.
4. In the retro-mylohyoid fossa the border of the denture can move back toward thebody of the mandible producing the S curve of the lingual flange.
5. In the anterior region, a depression (the pre-mylohyoid fossa) can be palpated, anda corresponding prominence (the per-mylohyoid eminence) is seen on the
impression.
The doctor played some videos about how to activate the muscles during impression
making? But he refused to give them to us. Sorry about thisHere are two videos that cover most of the information needed
http://www.youtube.com/watch?v=W87YVwMy4fo http://www.youtube.com/watch?v=Z3Um3z4Zo88
http://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DW87YVwMy4fo&h=qAQGjlcTahttp://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DW87YVwMy4fo&h=qAQGjlcTahttp://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DZ3Um3z4Zo88&h=qAQGjlcTahttp://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DZ3Um3z4Zo88&h=qAQGjlcTahttp://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DZ3Um3z4Zo88&h=qAQGjlcTahttp://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DW87YVwMy4fo&h=qAQGjlcTa