Prostho IV - Lec 3 - Review of the Relevant Anatomy for Maxillary and Mandibular Dentures

7/27/2019 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

Documents

Prostho IV - Lec 3 - Review of the Relevant Anatomy for Maxillary and Mandibular Dentures