prostho 12 ,Post Dam area and check records

8/3/2019 prostho 12 ,Post Dam area and check records

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I didnt have the slides so it made it much more difficult to me forgive me for any mistakes

We will discuss two topics in this lecture :

1-Post dam in complete dentures2 - Check records

Post dam complete denturesThis is a typical picture for an upper edentulous

mouth. What you have being doing during your

third year is learning how to construct a complete

denture.

In order to have a successful complete denture, it's

important to achieve retention and stability in the

final complete denture.

Anteriorly we have the labial sulcus and posteriorly the buccal sulcus, in

both these areas we can easily achieve a peripheral seal. Butwhat is

peripheral seal ?

Peripheral seal is the area of contact between the mucosa and the

peripheral polished surfaces of the denture base, thus preventing

passage of air between the denture and tissues). It depends upon the

proper extension of the denture borders, both in width and depth, to fill

the mucobuccal space and contact the cheeks and lips without distorting

them. achieved by having the peripheral borders and the polished

surfaces of the complete denture in contact with the mucobuccal and

the mucolabial fold (. This is ensured by proper border moulding) .This

will help in preventing air from leaking beneath the denture surface.However, the problem is in the posterior area where no posterior

vestibule is present

So howcan we achieve a posterior seal in this area?


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there is a unique tissue structure in the soft palate which allows us to

apply some pressure but within a certain physiological limits. To

compensate for the absence of the vestibule we need something that

stays constantly in contact with the tissues of the soft palate that will

help in preventing the air from leaking beneath the complete denture. .

This is known as post dam

This part in the patients mouth is called the posterior palatal seal area the

opposing area which is part of the denture is called the post dam so they are

two different parts.

posterior palatal seal is part of the patients mouth .

post dam is part of the denture which is going to sit against the posterior

palatal seal area.

what are the anatomical landmarks to the posterior palatal seal area ?and

how we are going to determine it in the patients mouth?

The Post Dam AreaThe post dam is an elevated ridge of acrylic, so it is extra amount ofacrylic is added on the posterior fitting surface of the denture, this will

be in continuous contact with the posterior palatal seal in the patient's

mouth.

So the main aim is to achieve good peripheral seal both during rest

and during function, we can achieve this by a proper border molding

using the green stick.

So if we have achieved a successful peripheral seal we will achieve:

1- a good retention ( which is preventing the denture from fallingdownward) if we have a dislodging force acting perpendicular to the

base of the denture.


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Cohesion (retentive forces between similar molecules, ex saliva)

and adhesion (retentive forces acting between dissimilar surfaces,

ex saliva between the denture fitting surface and underlying

mucosa) and surface tension. All threehelp in retaining the

denture when forces are applied 90 degrees to the denture base.

2- Lateral and horizontal dislodging forces are resisted by havingcomplete peripheral seal.

3- Increasing stability of the denture and this is achieved by having anintimate contact between the soft tissues and the denture. So

whenever denture moves; it will remain in contact with the

underlying resilient tissues of the soft palate thus increasing the

denture's stability.

advantages of post dam and posterior palatalseal

1-It decreases:

a) Gagging - which is usually stimulated by touching the

posterior third of the mouth not by touching the soft palate, so if

we have a denture which drops every second and continuously

touching the posterior third of the mouth, that will stimulate the

gag reflex.

b) tongue discomfort - the post dam

should blend with the tissues of the

soft palate. It does not end as a buttjoint

c) food accumulation - there will be

no separation between the denture base and soft tissues thus food

accumulating beneath the denture.


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2-it compensate for shrinkage :

When you process acrylic (PMMA); there will be polymerization

shrinkage. Post dam will act as reservoir in order to compensate

for the amount of shrinkage that might happen.

3-having a partial vacuum effect:

Having continuous vacuum throughout when the denture is in

the patients mouth is harmful, which usually ends by pathological

tissue overgrowth. All what is needed is to only a partial effect.

This is only activated when having horizontal lateral tipping

forces which is not enough for to dislodge the upper denture, it

will only slightly break the peripheral seal and this will lead tolittle amount of air leaking beneath the denture. Atmospheric air

pressure is higher than the one beneath the denture and this

pressure gradient will help to keep the denture in place.

anatomical landmarks:1- pterygomaxillary notch ( hamular notch)

its located posteriorly behind the tuberosity area and in front of

the pterygoid process. This area has the capability of withstanding

the physiological compression so we would like to extend the

posterior border of the complete denture into this area. However,

it's so important not to extend it over the pterygoid process

because its only covered with

a thin layer of mucosa .

2- fovea palatine

which is the two ductalopenings of the mucus glands

which is found on either side

of the midline. It helps in

determining the vibrating line.


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3- midpalatal raphe

a very thin layer of mucous membrane overlying the midpalatal

suture, appears clinically as a tight cord, contains little or no

submucosa and will tolerate little compression, may extend onto

the soft palate. So when designing the postdam, it is important notto cause any pressure on it.

4-pterygomandibular raphe

loose band of connective, extends from the pterygoid process to

the retromolar pad area, mustnt be encroached upon by the

denture.

5- posterior nasal spine

which is the posterior part of the palatine bone, and that will

affect the shape of the anterior vibrating line (see below)

6-vibrating lines

We have anterior vibrating line

and a posterior vibrating line.

The anterior vibrating line is an

imaginary line located between the well

attached tissues which are overlying the

hard palate and between the

compressible ones over the soft palate.

It is always on the soft palate and should NOT be confused with the

junction between the hard and the soft palate (it's never in the hard

palate because we need certain amount of compressibility). It is not a

straight line due to the projection of the posterior nasal spine.

The posterior vibrating line is an imaginary line, it represents the

demarcation between that part of the soft palate that has limited or shallowmovement and the remainder of the soft palate that is markedly displaced

during function. Marks the most distal extension of the denture base.

In the majority of patients (70- 80%) the posterior vibrating line is located

anterior to the fovea palatine and t is found to be behind the fovea palatine in

around 20% of patients.


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The area between the anterior and posterior vibrating lines can be

compressed by the post dam in the upper denture because the area it covers

from the soft palate contains glandular and adipose tissue, however you can

notice here that there is minimal depth and width in the mid palatine part but

why? Because this area does not contain glandular and adipose tissues andits covered by a thin layer of mucosa so we try to avoid having pressure over

this area.

The posterior palatal seal area - anatomically

it's divided to two distinct anatomical parts:

1- the pterygomaxillary seal (A in

the pic)

2- the postpalatal seal (B in the pic)

Both of them constitute the

posterior palatal seal area.

Pterygomaxillary seal occupies

the entire width of the hamularnotch (extends from the distal

surface of the tuberosity to the

hamular process), continuing 3-

4mm anterolaterally approximating

the mucogingival fold.

Post palatal seal extends medially from one tuberosity to the other and

it occupies the vibrating line.

classification of soft palate:

(A) Pterygomaxillary seal extends through thepterygomqxillary notch (B)Post PS extends

medially from 1 tuberosity to the other

(C)posterior PS area lies btw the anterior &

osterior V.L


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Knowing the

classifications of

the soft palatewill guide us in

determining the

outline of the post

dam area.

we have three classifications according to the angle which is formed

between the soft palate (The more acute the angle the more muscle

activity there is).

1-Class one : it's actually the most favorable because we haveminimal muscular activity and its almost horizontal in shape, this

will allow us to achieve the widest area (large distance between

the AVL and PVL) of post dam however that will be the least in

depth.

2-Class three : we have the maximum muscular activity (acuteangle which is formed between the hard palate and the soft

palate), which means that the soft palate will be more displaced

compared to class 1 and class 2, this will lead to the narrowest

post dam but the deepest.

3-Class two: lies between class 1 and 3 in its properties.Having mentioned that class 3 have the maximum displaceability and

imagine we have a denture in place, so if the soft palate is going to be

displaced downwards and forming an acute angle between the hard andsoft palate, there will be a large gap between the fitting surface of the

denture and the soft palate, so I need to increase the depth scrapped in

the cast and therefore the thickness of the post dam area in order to

preserve the intimate contact between the fitting surface and the soft

tissues.


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Now in class 1 I have a minimal movement so there is a minimal space

between the fitting surface and the soft palate so no need to increase the

thickness of the post dam here, so its the widest however its the least

in depth.

outline shape of the post damAccording to the classification of the soft palate I can outline the shape

of the post dam area. There are three major types:

1-major and minor2- cupid's bow or the butterfly shape ( which is the most used here)3-single line

In an average Class I soft palate -

the widest area of the butterfly-

shaped post dam is between 4 to

6 mm in width. However, it is 2-

3mm in the modified butterfly.

Picture represents the width and

depth of the post dam in an Class

I soft palate.

The two mm in the hamular notch is almost average in the human

beings however the area over the 4-6 mm may have slight variation

between individuals and this will depend on the amount of displace

ability and the activity of the muscle in the soft palate.

Now the depth of the hamular notch is around 0.5 ml that will increase

gradually to reach its maximum (in which we have the glandular and

adipose tissues) and then will decrease gradually to reach 1ml towards

the midline.


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recording the posterior palatal seal (clinical part )We can do it at any stage after the primary impression, however we

usually do it at the try-in stage.

We can do it in the master impression stage if we can anticipate that

we are going to face problems in the retention of the record blocks at

the jaw registration stage.

The techniques in the clinic:

1- anatomical2- functional3- arbitrary - 'guess estimate' the least accurate

The anatomical technique:

We start creating the post dam at the secondary impression by proper

border moulding using green stick. We should check that the tray is well

extended (2mm behind the fovea palatini) to prevent having an under

extended post dam area at the final denture compromising the

denture's retention.

Green stick is a soft flowable material and it needs something rigid to

support it. Thus, we should apply it over the posterior acrylic not the

posterior edge. And to compress the soft tissues there should be enough

thickness of the material.

When it comes to the anatomy then we should determine:

a) Pterygomaxillary sealb)Postpalatal seal (PVL, AVL)

First. outline the pterygomaxillary seal by an indelible pencil line is

placed through the hamular notch and extended 3-4mm anterolateral to

the tuberosity, approximating the mucogingival junction.


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How to determine the posterior vibrating line?

1-asking the patient to say AHHH in short bursts2-Valsalva maneuver: ask the patient to close their nose and to

forcibly blow against the closed airway; noting the area betweenshallow and marked displacement)

How to determine the anterior vibrating

line ?

AVL is determined by palpating the tissues

anterior to the PVL using a T burnisher or

mouth mirror to determine their

compressibility and width. Valsalvamaneuver or AH may be also used. Note

the area in front of the posterior vibrating

line until the compressibility of the tissues

reaches its minimal or disappears, that will

demarcate the anterior vibrating line.

So we determine with an indelible pencil

the lines in the patients mouth and

either insert the record block, thetrial denture, or the master

impression (depending in which

stage we are recording the

posterior palatal seal area) in the

patient's mouth. The aim is to copy

the lines from the patient's mouth

to the master cast to the correct

depth and width that we havealready talked about.

Disadvantages of the anatomical technique

Determining the compressibility of

tissues usin T burnisher

The anterior vibrating line has transferred to

the master cast


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1)There is a chance to over compress the tissues beyond their

physiological limits and 2) it needs accuracy in transferring these lines

into the master cast.

The functional technique

It is actually done in the master impression stage. All the steps in

determining the posterior palatal seal are repeated just like the

conventional way. After we finish border moulding and made the

secondary impression using ZOE, we transfer the lines drawn

intraorally to the master impression after it has set.

After copying the post dam area onto

the impression, we fill this area with

a flowable wax which is designed to

flow at mouth temperature.On the secondary impression, we

melt the wax and place it over the

determined posterior palatal seal

area which was transferred to theimpression. Wax is applied slightly in

excess and allowed to cool below the

mouth temperature to increase its

consistency then held hold the tray

under gentle pressure and leave it in patient's mouth for 5 minutes. Wax

will flow at the patient's mouth temperature and will record the

physiological displaceability of the soft tissues.

The elevated part of wax will be replicated, when pouring the impression, asa negative depression in the master cast.

Advantages of functional stage

The melted wax is painted onto the final impr

within the outline of the posterior palatal seal


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1- over trimming the master cast is avoided2- over compressing the tissues is avoided3- it helps in achieving a better retentive record blocks at the jaw

registration stage.

4-mechanical scraping of the cast is avoidedDisadvantages: 1) more time is needed 2)difficulty handling the

material.

Errors in recording of posterior palatal seal1- underextension

Which will have a short posterior border of the denture that will

compromise our retention and stability of the denture.

what might have lead to this under extension ?

A)poor examination and poor determining of the posterior palatalseal area.

B)

it can be seen in patients who have severe gag reflex becauseduring the primary or secondary impression you try not to push

the material to the posterior part of the patient's mouth, so you

will have an under extended master impression and therefore the

final result will be an under extended complete denture.

2-over extension

We sometimes try to overextend the upper posterior border

thinking that we are maximizing the retention. However, the

posterior edge will contact the active portion of the soft palateand will drop each time the soft palate in function compromising

the retention.

Overextension is due to wrong determining of the PVL. Patient

will come complaining from painful swallowing and ulcers. Pain in

the pterygoid process area which is covered by thin mucosa.


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We can overcome this over extension by cutting back the distal

border.

3-shallow post dam

Can either be due to 1)mouth widely open and

pterygomandibular fold becomes tense OR 2) under scrapping of

the master cast.

To overcome this problem we can further scrap the master cast

and adapt the trial base if the conventional anatomical way is used

or add more wax if the functional way was selected.

4-deep post dam:

Due to over scrapping the master cast. Swallowing is painful and

difficult, ulcers, nausea, loss of retention can all be expressed bythe patient

Correct it by selective trimming and polishing to the over

convexities in the post dam.

Now we will talk about another topic which is:

Check recordsAt the insertion stage; you can end up by two scenarios - a successful

polished surface, fitting surface and occlusal harmony or a denture full

of errors and disharmony in occlusion.

Now there are many causes that may lead to such a, less than ideal, final

result, it can be due to lab error or clinical error.

Errors in occlusion can be due to:

1) incorrect registration of the centric relation.


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At the jaw relation record we have unstable record bases and there is a

big chance they will move while recording the centric relation resulting

in premature contact (unilateral, bilateral or in the incisor region) and

leading to uneven compression of the underlying mucosa. You will end

by having a premature contact on one side and a gap on the other side.

This does not happen on cast, so this may pass unnoticed at the try-in

stage.

2) poor mounting of the record blocks, you have achieved a good jaw

relation record, you have sealed both upper and lower record blocks

but you missed to check that the heels of the casts are not touching... so

you will end up by incorrect jaw relation records .

3) irregular setting of the teeth by the technician, failing to achieveeven contact in both centric relation and lateral excursions.

Teeth are set in soft wax when cooling the wax will shrinks, so that may

add to some of the inaccuracy at the insertion stage.

the other cause is that at the try in stage the teeth are set in wax so

you try to determine if you have a correct centric relation, however the

patient can bite hard on one side than another, or if he has any

premature contact there will be a slight movement of teeth under wax,or sliding of the base plates to achieve the maximum inter-cuspation

between teeth. This is why problems can go unnoticed in the try in stage

and that will only be noticed at the insertion stage.

4) Flasking errors

How can I adjust occlusion?1-If I had minimal errors I can adjust them at the chair side.

I insert the upper and lower denture, mark any premature

contacts of high pots using articulating paper and adjust chair

side. .


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Summery -> LAB REMOUNT PROSEURE

:

2-Lab remount

The main purpose is to achieve occlusal harmony (balanced

occlusion and articulation) , re-establish the correct vertical

dimension .

I shouldnt over trim while adjusting teeth because otherwise I

will lose the correctly determined vertical dimension.

Ideally it should be done routinely after each de-flasking and

before inserting the denture in

the patient's mouth.

Now this is the master cast and

the processed denture still

attached to it after deflasking.

(Keep in mind that we still have

the plaster mounting bases and

the master cast at this stage).

we re-attach the master cast into

the plaster mounting and then get them back to the articulator

because we need to know if we have done enough processingerrors to either increase the vertical dimension due to processing

or if I have any occlusal disharmony due to any tooth movement

during flasking which was incorrectly repositioned.

I shouldnt have the incisal pin raised more than 1 mm away from

the incisal table. This would indicate that enough errors are done

that merits the need to remake a new denture.


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Now after I have adjusted the dentures in the lab, and got rid of

any lab errors. I send them to the clinic to insert them in the

patients mouth. All what I may face of errors now are clinical

ones, which may have happened during jaw registration stage.

3- clinical remount

In the clinical remount I destroyed the master cast, in order to get

the dentures out of them. I have nothing to remount the denture

again back in the clinic, so how can I know the actual relationship

between the upper and the lower once again ?

We should first agree that the vertical dimension is correct at the

insertion stage. Now, if I inserted the upper denture and the lower

denture checked that(retention, stability, aesthetics are

satisfactory) but there was a huge occlusal disharmony (ex

anterior or posterior open bite, uneven contact etc...) that can't be

corrected chair side I have to do something called clinical

remount.

Firstly, I have to remount the upper denture using either a

facebow ( which is the most accurate) or arbitrary mounting jig

that you have used in the lab.

Now before remounting the upper denture you have to block out

any undercuts in the fitting surface using tissue papers because

we are going to pour the denture with plaster, so we are dealing

with the denture as an impression, if we miss this stage the

denture will be locked in the cast and will break upon removal.


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Now after mounting the upper denture on the articulator, you

separate it from the plaster you insert it in the patient's mouth

then you insert the lower denture as well. I now need to

determine the relation between the upper and the lower, we have

to re-record the centric relation once again. How can I record the

relation between the upper and lower ?

We have something called the ALUWAX or we can use the red

modeling wax. Cover the maxillary teeth with 2-thicknesses of

base-plate wax or ALUWAX but not beyond the buccal cusps

(hinders visual assessment). Guide to RCP and stop just before

teeth contact, teeth separation is about 0.5mm. Any area of

thinned wax (uneven pressure) => repeatAccuracy is crucialMake sure that you have a stable lower denture. Remove both

dentures together and mount lower denture after blocking the

undercuts!.The relation between the upper and lower dentures are

determined in the pre-centric position, which means that I will

guide the patient to the centric relation where the condyles are in

the most superior and anterior position, however I dont want the

patient to go bite through the entire width of the wax (I dont let

the teeth to touch each other), because if they do touch it will lead

to displacement of dentures...repeating the same error that we

have already done at the jaw relation stage. Any penetration or

thinning in the wax will necessitate repeating the pre-centric

record.

centric relation teeth are touching

precentric avoid teeth touching


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To put things together, we mounted the upper after blocking out

the undercuts=> take the pre-centric record=> mount the lower

=> remove the wax which was used to record the relation

between the upper and lower dentures=> we will be left out byspace which represents the thickness of wax=> we need to close

the incisal pin in order to see where is the first premature contact

I am facing.

adjusting the centric relation:1-We can have a premature contact between a cusp and a fossa, but the

question is: shall I deepen the fossa?or shall I trim the cusp ? or does it

make any difference if I have a functional cusp or nonfunctional cusp ?

Which one we try to avoid ?

Answer: Avoid adjusting functional cusp as those are the ones

which preserves the determined vertical dimension.

The functional cusp in the upper palatal cusp

The functional cusp in the lower buccal cusp

So imagine if we have premature contact between the upper palatal

cusp (which is the functional cusp ) and opposing lower center fossa.

Q- Do I have to adjust the palatal cusp or deepen the opposing fossa ?

I can't determine now, I have to further ask the patient to do lateral

excursions.

if the cusp is high in both centric relation and lateral excursion, the

problem is from the cusp, so I have to adjust the it. However, if the cusp

which is already high at the centric relation is out of occlusion in lateral


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excursion, this means that the problem is coming from the fossa and we

have to deepen it.

Summary: so at centric relation it's difficult to determine whether I

have to adjust the cusp or the fossa, so we will have to further ask thepatient to move to lateral excursions and determine if the cusp is still in

contact and needs adjustment.

This picture is a premature contact

between the functional cusp which is

the buccal cusp in the lower, and the

opposing fossa in the upper, so if this

cusp is still high at lateral excursions,I need to adjust from the cusp, I

adjust the slopes of the cusp(the

mesial and the distal slopes) not cut the tip of the cusp.

adjusting the lateral contact:Now I have achieved an even contact at the centric relation, so I won't

touch the centric relation again, I have to go and adjust the lateral

contact.

Now in lateral we have a working side and a non working side contacts.

what is the working side ?

If I asked the patient to move to the left side, the direction in which the

patient is moving is called the working side, and the right side will be

the non working side .if I have both lower and upper buccal cusp touching, I adjust the upper

because it's the non functional cusp .

if I have both, the lower lingual cusp and upper palatal cusp touching I

adjust the lower lingual cusp.


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so this rule is called the BULL rule, we adjust the buccal upper cusp

and the lower lingual cusp, which are the non-functional cusps.

Now what if we have a balancing interference (which is on the non-

working side) this happens with between both functional cusp betweenthe upper palatal and the lower buccal cusp, so shall I trim the upper or

the lower ?

It is preferable to preserve the palatal cusp and rather adjust the lower.

We try to adjust the slope of the cusps, by re-shaping the buccal-facing

slope of the upper palatal cusp and the lingual-facing slope lower buccal

cusp.

Adjusting the protruding contact:By asking the patient to slight forward to an edge to edge contact. I may

have anterior and/or posterior pre-mature contacts.

- Grind the palatal surface of the upper anteriors and labial surface of

lower incisorsthis does not reduce teeth length but sometimes I need

to reduce slightly from the length of the lower incisors.

-Anterior interferences are adjusted by preferably grinding the lower

incisors because presumably the clinician has spent time to ensure

correct aesthetics and phonetics.

-Posterior interferences are adjusted by grinding the distal slopes of

upper cusps and mesial slopes of lower cusps.

Now after adjusting everything you need re-polish the teeth to

have a smooth surface, not ending by having rough surface after

trimming the teeth. This can be done by applying some pumice to


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the occlusal surface of teeth and move them against each other,

while they are still on the articulator.

THE END

Wish you all the best of luck

Life is too short, so smile while you still have teeth

Diana : thank you for helping me ( bs mu kteer :P ) bel tafree3' o god bless our lovely friendship

Documents

prostho 12 ,Post Dam area and check records