Prostho Lecture 2 ,Anatomy of Edentulous Ridge

8/3/2019 Prostho Lecture 2 ,Anatomy of Edentulous Ridge

1/19

1 | P a g e


2/19

2 | P a g e

In the name of Allah the most gracious, the most merciful

***Please return to the slides while studying, because I didnt havethem when doing this lecture.

-Today we will talk about the anatomy of the Edentulous Ridges. Forthe past two lectures we were going pretty slowly. Today we will be slowbut you will see for the coming lectures how the dr will pick up slides quitequickly. So if you miss the reading assignments, you will have lot of reading to do by the time when we come to the midterm and finalexamination.

"The reading assignment for the anatomy lectures from the text book are (pg211 to pg251)", this includes the impression procedure and theanatomy for the maxillary and mandibular arches. The anatomy for themaxillary arch is about 6-7 pages in the beginning of the chapter.

Last week we talked about primary impressions and pouring up theprimary impression . This week were working on making the custom traysto make the primary impressions so that next week you can make yourfinal impression using materials that you will be using in the clinic.

Ultimately ending with alginate impression or the impressioncompound for taking the primary impression, ,and finally ending with aprimary cast which we used to make a custom tray.

- When we talk about the anatomy of the maxillary arch, it will be a goodidea to talk a little bit about the extra oral anatomy; not the extra oral

anatomy that we used to, such as the extra muscle for facial expressionand so on. Actually, some of the landmark that we will talk about when wetalk about history examination of the patient.


3/19

3 | P a g e

- There are specific landmarks that you are very familiar with. The first is the vermilion border of the lips; It is essentially the meeting of the oralmucosa with the skin ( ( vermilion = . .Vermilion borders are important because whether the lips have support

from the dentures or not, determines whether the vermilion borders willbe clear or more hidden or straight.

When the lips are supported by teeth thevermilion border is more clear,however; with age or teeth extraction the lipget smaller.( ,

(

** You can see the upper and lower vermilionborders in the picture.

-You might be familiar with terms such as: mesio- labial groove and labio-mental groove. All of these specific facial features become more expressedwith age . If we dont have teeth support they become even moreexaggerated. They are signs of age.

- Why??- Because we are losing essential facial support as we have no teeth. Not only we lose the support anterio-posterior and laterally, but also we losethe support as the jaws become closer and more approximate to eachother. We lose anterior facial height " " So we have loss of facial tone.

-Some patients can do quite a lot of facial expressions; you will besurprised how close jaws could be brought together!! The dr has seenpatients who could bring their lower lips above their nose. The atrophy iscontinuous after extraction and it continues for life.The early the patient


4/19

4 | P a g e

extract the teeth, the less bone they will have.The resorption will continuethrough the alveolar bone to the Basel bone. The bone is so cutinize that in fracture and dissolves by itself. ((

- Bone resorption means there is no support for the facial tissue.

-Do you know what the Philtrum is? The Philtrum is essentially a smallarea in the midline in the upper lip ( But in the opposite.( of the philtrum we have something that is calledcolumella.

-The columella opposes the philtrum . So we

have a depression in the upper lip. Thecolumella is essentially below the bridge of thenose , it's the area between the nares " openingsof the nose". It's like a column, and if you followthe columella down there is the philtrum .

- The angle between the columella and thephiltrum ,if there is adequate or sufficient labialsupport ,is supposed to be approximately 90 like the picture because we have a lip support with the other lip.

What we attempt to see is that there is an anglebetween them. But If the patient loses his other lip support. What willhappen?

-The angle will become obtuse ( ), the lip will lose it support.

( (. This is important fact when we actually set teethwe do (jaw relationship record).


5/19

5 | P a g e

We talked about specific guidelines we must follow when we set the teeth and do jawrelationship record, one of the mainguidelines that we look for is: this angle.

Whats the main muscle in the cheek? It is the Buccinator. Behind the mandible

) (we have the masseter muscle.We are just mentioning this because later on you will see that it functions inthe denture in an indirect way.

Those of you who have taken the lab have already heard some of the thingsthat Im going to talk about today. Hopefully the repetition will help you.

When we talked about the intra-oral anatomy of the Edentulous Arches(the maxillary and the mandibular), we essentially divided the anatomy intotwo parts:

1- A part which supports the denture (the denture bearing area, the support area).

2- Peripheral structures (the limiting structures around the denture).

We said that the object of taking the primary or secondary impression is toregister the entire surface area and the Edentulous Ridge, so that we havebetter support for the denture. Its in our interest and the patients interest tocover the largest area. If I cover a small area, and the patient chews thedenture will hurt the patient in that area. The more support I have, the greatersurface area, the better and the more comfortable the patient is.

So Ill cover as much as of the Edentulous Arch as I can. As I said, if I enlargethis support area and I keep reaching the borders beyond the EdentulousRidge Im going to run into the tissues that move because Ive muscles.


6/19

6 | P a g e

We said that we have the Buccinator in the cheek and orbicularis orisaround the opening of the mouth and posteriorly I have the soft palate andlevator and tensor veli palatini, there are a number of muscles that attach themaxilla to the mandible into the tongue. And in the mandibular arch I have thetongue with extrinsic and intrinsic muscles. These tissues move and I cant

extend the denture into this movement.

Extending the denture to the movable areas leads to one of two things :

1- Dislodgement and movement of the denture which is uncomfortable tothe patient.

2- The denture is relatively stable so it will cause trauma ( )

So I have a dilemma! I want to cover as much as possible but I dont want togo beyond the normal movement. These things are important when I talk about the impression, because as you will see the impression is taken in twostages:

1- Figuring out what the limiting structures are. (Border molding aroundthe sides of the tray as you saw in the lab).

2- Then we take an impression of the whole area. So we have the externalstructure around the denture and then the denture bearing areas.

Quick review to the things that we'll be talking about today: we can take alook at the palate, the residual ridge, the vestibule externally and the soft palate posteriorly.

The prominence of bone as you know is what remains after the teeth are

extracted; we said that it is called the alveolar bone or the residual bone . It constantly changes shape after extraction. And the way it resorbs or atrophiesis very typical from patient to patient.

The resorption occurs in specific directions, sometimes more resorptionhappens on the labial than the lingual side, while other parts resorbs from the


7/19

7 | P a g e

lingual more than the labial, depending on the density of the bone and theanatomy of the bone in that area.

At the end of the residual ridge in the maxillary arch we have two largeprominences called the maxillary tuberosities (designated with the squares),sometimes they are small depending on whether they were removed duringextraction. So essentially the residual ridge extends from one maxillary tuberosity to the other .

The ridgecan havedifferent shapes, it canbe prominent,atrophied,regular,irregular,symmetricalor

nonsymmetrical.

At the junction of the anterior part of the palate and the residual ridge youhave the incisive papilla (the circle). The incisive papilla is essentially smallprominence which over lays the exit of the naso-palatine nerve and bloodvessels. Its a sensitive part, we d ont like to load it, its what we call a relief area !! We dont want pressure in this area.

If you feel the upper part of your mouth, just behind your central incisors you will find asmall prominence, is the incisive papilla .Behind the incisive papilla in the anterior part of your mouth, we have an irregular areacalled rugae ; we will talk about it in moredetail.


8/19

8 | P a g e

In the midline, at the junction between the palatine process of the maxillaeand the palatine bones we have the mid palatine suture (mid palatineraphe) .

If we go further behind we will run into the soft palate, if we go furtherfacially, we'll end up into a pocket like structure called a vestibule (sulcus).This is divided anteriorly and posteriorly into the labial sulcus and the buccalsulcus on either side. The labial sulcus is divided from the buccal sulcus by thebuccal frenum on either side. In the middle of the labial sulcus we have labialfrenum.

In the back, we have the (HamularNotch) which is a depression between the

maxillary tuberosity and the hamularprocess of medial pterygoid plate.

Microscopically the tissue found in themouth on the residual ridge is a scartissue. If you cut yourself the tissue willheal and it will leave a scar. When we extract teeth the tissue that remainsafter extraction is a scar tissue (healing tissue). It wasnt designed to withstandthe force of a denture. Its important t o understand this. The Edentulousmouth wasnt designed to support the denture . We take advantage of it tosupport the denture, but the tissue and the mucosa above it arent specificallydesigned for denture. It is a sensitive mucosa.

You know that the tissue in the mouth before extraction is divided intokeratinized and non- keratinized (masticatory mucosa and lining mucosa)

or specialized mucosa (like the surface of the tongue where we have the tastebud).

If you take a look on the maxillary Edentulous Ridge, you will notice that the entire palatal surface and the residual ridge are keratinized mucosa


9/19

9 | P a g e

(masticatory mucosa), it will withstand a certain amount of friction eventhought it wasnt specifically designed to have a denture sitting on top of it.

The further out we go , were running to a junction. Masticatory mucosa isattached mucosa; its attached to the bone in the palate or to the residual ridge.However, when we go further out to the vestibule, there will be a junction at which the tissue is no longer attached.

So, we have attached and un-attached tissue . We want to extend just ontothe un-attached tissue but not much farther beyond. The un-attached tissuewill be lining mucosa (no keratinization). Friction and movement of this part of the mouth might cause ulceration and trauma. Its not so much only that wewant to extend to the extent of the muscle we also want to have support from

tissue that can withstand friction and force.Whats under neath the mucosa? We have the sub-mucosa and mucosa have

squamous epithelium, lamina propria and the sub-mucosa which has bloodvessels , glandular tissue and adipose tissue and so on (It provides support).The thickness of the sub-mucosa varies in different parts of the mouth, and inour case it varies in the maxillary arch. Some parts of the arch have a thick sub-mucosa, some of them have loose sub-mucosa and some of them have verythin area. Depending on the thickness of sub-mucosa , we'll find that someareas are designed well to stand stress from the denture while other areas arenot! We need to relieve or avoid them from the denture so th ey wont causepain, ulceration or friction in the patients mouth.

We already said that in the incisive papilla area we have a group of bloodvessels and nerves ( a relief area ). In the posterior part of the palate, we have

the greater and lesser palatine nerves (we dont want a heavy load in this areaeither). Thankfully, we have thick sub- mucosa so it wont be a problem.

In the midline palatine raphe , the mucosa is very thin , so it's a relief area.Depending on the tissue and the sub-mucosa, whether it's thick or thin youwill see that some areas are considered primary stress bearing areas , areas


10/19

10 | P a g e

are considered secondary stress bearing areas and some are consideredrelieve areas (we dont want to place force on them).

If you look closely in some mouths you will actually see a groove (depression of the residual ridge), it indicates where the facial and lingualgingiva met after healing (like we said its a scar tissue). The position of thisgroove is sometimes helpful to us when we set teeth just as the incisive papillais! It tends not to move that much so it's a good guideline of setting of theteeth.

What can we see behind the maxillary tuberosity (the small depressionreferring to the slides ? Its the hamular notch , it's a soft area withrelatively thick sub-mucosa, the only thing that you can find here are

tendinous attachment s for two muscles of the soft palate which are the :levator veli palatini and tensor veli palatini.

You cant extend the denture behind this area for a specific reason,because behind it we have a rigid tissue, it's called pterygo mandibularraphe . It attaches to end of the pterygoid hamulus of the medial pterygoidplate.***In the body when you have a tuberosity or a prominence or attachment (attachment of the muscle) it's there for a reason. If you find the boneraised when looking at the skeleton and its not raised because there istension on this area ,then it is usually attachment of muscle or a tendon.

Pterygo-mandibular raphe : is an attachment from the hamulus downto the posterior part of the mandible in an area we call it retromolarpad" We will learn about it next week inshallah ". Its not there for no reason,

its a junction between muscles, its an anastomosis of two muscles , whichare the Buccinator and the superior constrictor muscles. This tensionallows the hamulus to move. If you want to look for the hamulus in ayoung child, you properly wont find it, it wont be very clear. Just like themastoid process, it wont be very large.


11/19

11 | P a g e

Young children dont have large sternocleidomastoid muscles. Thesebones tempt to be larger and more prominence and angular as time goeson. There is tension on these areas. So, back here we have bony processand in the end of the bony process we have pterygo mandibular raphe. So,I cant extend beyond here because I essentially have pterygo mandibular

raphe and beneath it cant press so much because I have the thinattachment of the soft palate muscles. However, the (Hamular Notch) isimportant because it delineate the posterior part of the denture. posteriorpart of the denture is very important.

-The junction between the hard and soft palate is not the end of the

denture, I extend my denture just beyond the anatomic junction betweenthe hard and soft palate, just onto the soft palate.

How far is the soft palate?

Thats determined by which part of the soft palate moves . We know that the soft palate goes up and down, it closes up the nose from theoropharynx and closes up the mouth from the nasopharynx when we

breathe or eat. This movement will end on the soft palate not the hardpalate, that means that I can take an advantage of the soft palate todetermine the end of my denture. And usually the junction between themovable and the unmovable parts of the soft palate is called the vibrating line . Becausethe soft palate moves when the patient speaksor say aaaah , we take a look inside the

patient s mouth and then we can see parts of the soft palate in this area vibrating ,herewhere we want our denture to end. The dr willtalk more about why we reached that point in the end of the

lecture .


12/19

12 | P a g e

If we go posterior, the (Hamular Notch) on the bone will be about their referring to the slides . Its difficult to see and not every patient has aprominence tuberosity , usually well take an instrument like a mouthmirror or a blunt instrument and run it along the residual ridge until theinstrument drops. When it drops we know weve reached depression we

want.

The vibrating line is not always visible as some of these clinical pictures.So, here we have the imaginary vibrating line which we said is usually not on the hard palate, its just into the soft palate , to find it we I do one of 2things:

I ask the patient to say aaaah and I look

inside the mouth and I see where the motionstops and ends I take an advantage and usea special pencil (copier pencil) and I mark it inside the mouth to see which part of the soft palate moves and which part of the soft palateremains stable.

And also can take an advantage of certain

anatomic landmarks. We know there issmall depression in the posterior part of the palate whichs called Fovea Palatine.The Fovea Palatine is usually located 1-2mm behind the vibrating line. When wesee Fovea Palatine we mark them andwe know where the vibrating line is , just in front of the Fovea

Palatine by 1-2mm. we use a a copier pencil to mark so when I put acustom tray in the patients mouth, the denture it will imprint fromthe patients mouth into the custom tray and then I remove theexcess. So, this is a primary impression, if I want to know the exact line in the primary cast where the line is? I can even imprinted on theprimary impression before I take the impression


13/19

13 | P a g e

( )custom tray

And usually we take it at different stages during the fabrication of thedenture. Like I said we take advantage of these Fovea Palatine. What areFovea Palatine histologically ??

They are essentially grooves at the mucous minor salivary gland. Theydont have that much significan t in the mouth except they provide goodlandmark to find the vibrating line. (In the posterior end of the denture).You will notice that the posterior part of the denture there is different types of compatibility.

We said that the significant of the limiting structures is not the fact that we dont want the movement of the muscles to cause a displacement inthe denture. We said that the way the denture remains inside the patient mouth is very significant, Do you know how exactly the denture is retainedinside the patient mouth?. 1- Pressure 2- Some students said that we usesome kind of glue to stay in its position (dr said we dont use adhesives toprevent the denture falling by the gravity 3 - Physical forces that keepthe denture in the mouth like (adhesion and cohesion)

( ( however in the mouth, this not enough, it is there, it helps us but its not enough to keep the denture in the patients mouth w hile thepatient chews, speaks, shouts and whatever . It is there, it helps but it isnot significant.

Sometimes, we have mechanical retention. In some mouths we have

prominent bone; we can keep the denture over the prominence but it isnot permanent in every mouth and we cant take an advantage in everymouth even if its there. We said the primary method of the denture willremain in the patients mouth according to the Physical forces there issomething called peripheral seal (


14/19

14 | P a g e

( ! which we have asuction force, the patient faces the denture in mouth it sequences in a verysmall amount of air out. Now, the pressure underneath the denture is lessthan in the surrounding environment. If the patient tries to remove it, thepressure will be come less and it will be retaining more. So, we have

negative atmospheric pressure underneath the denture. How can I keepthe area seal? ( ... ( .. What I have is, Im very fortunate the limiting structures in thelabial vestibule and a buccal vestibule are already there, I have the cheek buccally and the lip labially. Posteriorly, I have a problem because I dont have a muscle that comes down. I have a soft palate which moves but Idont have an actual muscle that comes down and helps the denture.

So, what I said in the lab is the vibrating line is important because I dont want to extend on to the movable parts that of the soft palate but I want togo back as far as possible in order to extend the denture onto tissue that Ican press up. The back part; the posterior part of the denture is made sothat it compresses slightly into the tissue ( ..so the back end of the denture will actually

stick into the tissue not a lot it wont hur t the patient it only goes half mmin the back. So, the around cheeks and the lips they will come down andthey will create a seal. In the back, because the soft palate doesnt comedown like that so what I want you to do with the denture is to go up intothe soft tissue. So, the significance of the vibrating line is

1-I wants to go as far back as possible to make maximum coverage without going into mobile soft palate.

2- I want to meet the soft palate because I need soft tissue to be able to gointo it. If I end the denture in the hard palate the tissue is very thin so Icant compress it without cutting or traumatizing the patient so locatingthe vibrating line is very important thing to create the seal it is calledborder or peripheral seal. It will give me retention for the denture.


15/19

15 | P a g e

4- Physiological forces/retention (muscular control): some patientseven if the denture doesnt stay in the mouth by itself, they are able tokeep the denture in their mouth just by trapping it between the muscles) ( Buccinator and orbicularis oris ( ) this varies from one patient to the another.Some patients can control the denture and brace it and other patients areunable to do that) .so we try to make the denture as retentive as possibleby itself as much as possible without burden the patient. ThePhysiological forces/retention from muscle is more important for themandibular arch than the maxillary. The palatal form is different fromperson to person, some people are tall some people are shorter. The soft palate is sometimes more horizontal in some patients or more vertical in

others . These positions make it easier or more difficult for us to create theposterior seal ( ) so the horzintal is class l , thevertical is class lll and class ll is the one in between , the most favorable isclass l ~ House classification for soft palate form-In general, class I represents the gentle movement, class III represents theexcessive movement, while class II lies in the middle.

-The tuberasity as you can see it can be very large. If the last teeth to beextracted are the molars sometimes with time the teeth supra-erupt. ( ,if I remove one tooth ( the teeth they will lose the balance anddrift or they will lose the balance andthere will be a space. If I remove thelower tooth without removing the uppertooth sometimes the upper tooth will


16/19

16 | P a g e

drift and go down with the bone. Sometimes, if I leave posterior teeth toolong, the tooth will super-erupt and will bring the bone with it. Sometimes,I end up with maxillary tuberasity thats so large that they come dow n andtouch the lower arch. In such cases we do surgery to reduce the amount of bone, we have too much bone in this case.

(the tuberasity is too large they went for surgery the above picture)

-the residual ridge is important but the part of the hard palate is alsoimportant. Which shape do youthink is better or more suitable to

support the denture?? If you takethese different examples,remember you need a residualridge.

So, the U-SHAPED palate is the best one because you have a residualridge at the end to provide somestability from side to side. This oneIS EXCLLENT retention but there is nothing on the sides; slight movement may hurt the peripheral seal. The rounded is acceptable. The V-shapedproperly the poorest. The ridges how they can be? Sharp, rounded,prominent or undercut. A nice well rounded ridge is properly the best type. Nice ridges are properly a good support for the denture it wont cause pain at the vestibule of the ridge. Sometimes the tissue is so soft that moves you will found that the bone unlike what you might think = atrophyis much faster than the soft tissue. ( )so, whenthe bone resorpes , it means that the soft tissue, what will happen?? Thetissue will become loose just like someone whos very healthy they loseweight so they become thinner suddenly then the clothes will be loose. In


17/19

17 | P a g e

the mouth this is the situation. I the mouth, the bone resorpes then theridge become loose in some cases, in these cases its very important toremove excess tissue or we take an impression in a very special way. Thelabial vestibule on the maxillary arch is not significant as in themandibular arch. Like I said we have buccal vestibule and the labial

vestibule (which is divided by the Buccal Frenum- sometimes there is onefrenum or there are two frena/frenum). Posterior to the buccal frenumbeneath the vestibule you can spot a solid buccal bone (support) from thezygoma , this doesnt usually affect the fabrication of the denture unlessthere is a large amount of resorbtion in the ridge besides the zygoma thereis another landmark that we must take into consideration when making adenture which is the coronoid process (found outside the maxillary

tuberosity, the coronoid process comes forward when the jaw is openedcompletely (this movement must be taken into account when making thedenture).

Recall from your Head and Neck Anatomy Lectures the major musclesof facial expression: The Buccinator , the orbicularis oris and mentalis. All the major muscles of facial expressionanastomose (join together) at the corner of themouth; this anastomosis is called the modulus . Themodulus is significant because it overlies the buccalfrenum, so when the Buccinator pulls the cheek back,the buccal frenum will go back and when theorbicularis oris contracts the entire modulus ( when the patients smile the (

modulus will go up. This means when we make an impression we need tobe careful in the area of the buccal frenum, we must create a notch in thedenture that allows the buccal frenum to move freely without restriction.( ) )


18/19

18 | P a g e

Earlier we mentioned that the mid palatine raphe is important becausethe underlying tissue Is very thin, in themedian suture of the midpaltine raphesometimes there is a protrusion present called: Torus Palatinus, is is basically an

excess of very compact dense bone found inone every five patients. The size of theseTorus differ (can be small or very large) but the tissue underneath the bone is very thin, meaning that any excessivepressure in this area will cause trauma and irritations to the patientstherefor e we cannot rely on this area as a Denture support area becauseof patient sensitivity as well as the fact that its not present in most

patients. Attempting to remove the Tori will lead to formation of heavyscar tissue and cause irritation. In fact there is Tori in the mandibleusually lingual to the canine (not a tumor just a bone)( ) We only remove it in some cases when its too big and causes

interference with removal/placement of the denture.

Finally we will discuss the direction of resorption ( ). In different parts of the mouth the bone have different angulations. In the upper anterior part of the mouth the teeth & thealveolar bone are slightly proclined at around 15Degrees. ( , 15 ), in the upper posterior part

of the mouth the molars are angled very slightly outward so you can seethe direction is towards the buccal (the alveolar bone of the posteriormolars follows in the same angulation), the lower anterior teeth & alveolarbone are angulated slightly outwards. The only exception to this rule isthe lower posterior teeth which are angulated in an inward direction (toward the tongue not toward the cheek) because they are trying tobalance out the upper teeth which they are angulated outward.

** Lower posterior teeth are the only teeth that are angulated inwards.


19/19

19 | P a g e

Recall from the curves of occlusion that the occlusal plane is curved.(Curve of monson , curve of spee and the sphere of willson). When weextract a tooth the alveolar bone beneath it will become shorter, Comparethe crest of the ridge before extraction and after extraction. Did it movetowards the palate or toward the cheek?? It moved towards the Mandible.) ), another example: This is the residual ridge beforeand after (referring to the slides) ( ridge (. The middle of the ridge becomes shorter and inward (further palatal). This is the case forall the Edentulous Ridges (Ridge & Bone) except the posterior of themandible mandibular posterior is going out and the maxillaryposterior is going in (they are moving opposite to each other). You willfind that the movement/resorbtion of the ridge has a significant in makinga denture and it has a significant in where we put the. In the upper archwe will put the teeth outside the Edentulous Ridges to put them back before they were extracted. In the mandible, we will try to put themfurther in before they were extracted.

**The lower posterior teeth are the only ones that resorb differently.

**Maxillary Arch becomes smaller

**Mandibular Arch anteriorly becomes smaller, Premolar area staysthe same & posteriorly it will become larger.

DONE BY: RAWAN YOUSEF MAKAHLEH

Date post:	07-Apr-2018
Category:	Documents
Upload:	justden09
View:	216 times
Download:	0 times

Prostho Lecture 2 ,Anatomy of Edentulous Ridge

Documents