pros tho don tics lecture 5,jaw relationship record
TRANSCRIPT
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8/3/2019 Pros Tho Don Tics Lecture 5,Jaw Relationship Record
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Jaw relationship record
:Notes
The Dr. started the lecture by revising a few steps in making complete
denture which we talked about it many times !
The dr. announced that he'll ask us in the exam about advantages and
disadvantages of materials used for making primary and secondary
impressions in the lab, I summarized them in the last page.
This lecture and the coming one, we'll cover chapters 15 & 16
in the book .
the Dr. repeated some points many many times so I mentioned them
in a simple way.
Now we'll begin our lecture .
Jaw relationship record has a lot of steps, it's not a simply taking animpression or border molding or wax impression, it essentially need
establishing the measurement of patient's face.
Now we know from studies that usually there are certain things
present in patient's mouth before and after extracting teeth.
we know that after we extracted teeth, the residual ridge:Example
resorb , and when we want to set teeth back to their normal position,
how can I do that if I have lost teeth and I don't have a record for the
patient's original ones ?! .. there are a number of guidelines that will
help us along away.
I told you that there are some things in the mouth:For example
remain the same such as the incisive papilla, we said that the center of
the incisive papilla is 8-10 mm behind the labial incisal edge of the
central incisor.
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So we have a guideline that presents before and after extraction in order to
find the ideal position of the teeth.
I know for instance that the teeth in the upper arch toward labial
(facial) to the ridge, so when the ridge resorbed I have to put the teethlabially.
Just to each residual ridge, this is relatively simple but when we talk
about upper and lower jaw and the 3D relationship between them, it
becomes a little bit complicated.
mandibular relationship :-Maxillo
In jaw relationship record, there are three basic steps :
1- Adjusting the maxillary and mandibular rims forming vertical
relationship.
So firstly, I find the distance between two arches; it's important and different
between patients .
2- Hinge axis location , I need to find the relationship between the
upper jaw and the patient head. The relationship between the upper
jaw and the axis of rotation of the lower jaw, because I'm taking these
relationships to transfer them the patient's face to an instrument
called " Dental Articulator " which is used to simulate the patient's
head.
3- Horizontal relationship between upper and lower jaws. To find the
relationship between two objects; I have to find the x,y and z axis.
ionship between upper: is the relatOcclusal Vertical Dimension
and lower jaws when the teeth are in occlusion.
.: also called the "centric relation"Horizontal relationship
It is the reference position of the mandible that can be routinely
assumed by edentulous patients under the direction of the dentist[ from
the book].
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In this lecture we'll concentrating on the vertical dimension of
occlusion .
When the patient comes without teeth, how can I find the relationship
between the upper and lower jaw. Remember always we use aguideline that presents before and after extraction because the
patients comes to me after extraction so I don't know what he like
before. In some rare cases patients come with some teeth so I can do
some measurements. BUT usually the patient comes without teeth so
the normal relationship is almost lost.
You know from physiology that muscles always and for certain
degrees are contracted, the mandible is hanged; attached to the upper
jaw not only through the TMJ but with muscles. We have the massester
outside, medial pterygoid inside.. we have muscles of mastication and
muscles in floor of the mouth attached to the hyoid bone.When I'm not required to chew, speak or swallow then the mandible
is relaxing (hanging). If the patient setting upright, muscles that tends
to hold the mandible up by some degree of extension and the gravity
will leave the mandible from a specific distance from the upper jaw.
Because we're dealing with edentulous patients so I need a
measurement that present before and after extraction. The objective in
making complete denture is the distance between upper and lower
jaws with teeth inside them not to make a denture at the rest position
all the time.
If I draw a point on the tip of the nose and the tip of the chin then I get
a ruler and measured the distance between them; I call it " the verticaldimension of occlusion (VDO)" represented by A in the picture below.
A student asked : do we have an average that we can rely on it to all patients ?
- unfortunately no ! it doesn't work so the best thing is to use a guideline which
is present before and after extraction.
Why this is significant ?
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This is important because I'll set the teeth according to it.
After the teeth are lost, VDO is lost but we still have the vertical
dimension of rest (VDR) so it's the same before and after extraction.
So now, I know VDR but still the VDO is unknown .. here we use the
average , they took many normal people and measure VDO and VDR to
them and found that the distance between these two measurements is
approximately 3 1 mm ( range 2-4 mm ) in 95 % of population.
This distance is called the" interocclusal distance (IOD)" or commonly
known as "Freeway space" .
So for my edentulous patient; I know IOD (constant) and VDR but I
don't know VDO .. look at this simple equation :
VDR= VDO + IOD ( FWS)
VDO= VDR IOD (FWS)
Assume that VDR = 8 cm ( 80 mm) then I can find my objective which
is VDO :
VDO = 80mm 3mm
=77mm
We made a record block in the lab which has a wax rim on it; wax rims
made according to the average measurements, when I put the wax rim
in the patient mouth and measure from tip to tip (it's not VDO nor VDR
it's vertical dimension of wax rims) , assume that we found it 85 mm
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then we have to remove wax to reach 77mm ( according to the
example ) , if we found it 75mm then we have to add 2mm of wax in
order to reach 77mm which is the VDO.
Teeth were designed to chew and even in chewing they'll not become
in touch because if we they do we'll end up with what's called
clenching and bruxism. So it's a natural protection in order not to hurt
the muscles and joints so they become in touch only 15-20 minutes
daily !
The teeth only touch in chewing and swallowing, the average of
swallowing is about 1000 daily but they actually become in touch for
less than a second so it's a count for almost nothing.
If we give the patient a longer teeth, let's say 80 mm .. then when they
become in contact there will be tension on TMJ, muscles and inflamed
gum.
So the reasons for having FWS are :
1- phonetic.
2-relaxing jaw.
While measuring, try to use tissues that don't move a lot like the tip of
the chin and the tip of the nose, or the base of the nose and the base of
the chin. (( the Dr. showed us a picture for instruments used for
measuring VDO but unfortunately I couldn't understand their names ))
but in the clinic we usually use a ruler.
We measure VDO and VDR when the patient in upright not in lying
position because the tension on muscles will be different and the
equation also will be .
Why we have FWS ?
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We have what's called "Frankfurt Horizontal plane ".
But it's not our reference because the teeth aren't at the same level;
they are short in the front than in the back so if you look to the patient
mouth when sitting upright you'll see that the front teeth will be lower
than the back teeth. That's mean that right and left will be at the same
level but in the back it'll be higher; so it's not parallel to Frankfurt
horizontal plane.
In the clinic we use what's called " Camper's plane "; camper is thename of a dentist.
It is the anatomical position of the human skull. It was decided that a plane passing
through the inferior margin of the left orbit (the point called the left orbital) and
the upper margin of each ear canal or external auditory meatus, a point called the
porion, was most nearly parallel to the surface of the earth, and also close to the
position the head is normally carried in the living subject. [ wikipedia]
Now, how can I know the correct plane for the wax rim in
the patient mouth ?
http://en.wikipedia.org/wiki/Anatomical_positionhttp://en.wikipedia.org/wiki/Human_skullhttp://en.wikipedia.org/wiki/Orbit_(anatomy)http://en.wikipedia.org/wiki/Porionhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Porionhttp://en.wikipedia.org/wiki/Orbit_(anatomy)http://en.wikipedia.org/wiki/Human_skullhttp://en.wikipedia.org/wiki/Anatomical_position -
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We need anterior and posterior lines, the anterior one pass from pupil
to pupil ; this is the anterior reference to the wax. The posterior one is
called " Ala- tragus line " from the lower border of the ala of the nose
to the tragus of the ear ( variable between patients) . The angle
between the Ala- tragus line and Frankfurt plane is 5
-15
.
The patient should show 1-2 mm of the incisal edges ( the wax rim in
edentulous ).
So now we know the length and axis of the wax rim, we remove wax
until it becomes parallel to the Ala-tragus line and at the same time
shows 1-2 mm of the wax rim interiorly. After we knew the length of
the wax rim , we need to support the lip so the angle between thecolumella of the nose and the philtrum of the lip is 90
. So I adjust the
upper wax rim to be parallel to the Ala-tragus line , inter-pupillary line
showing 1-2 mm below the crest of the upper lip.
Now after finishing with the upper, we put the lower one and start
adjusting it by adding or removing wax as in the upper.
How long the wax rim should be ?
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Usually we adjusting the upper rim for esthetic, phonetic and occlusal
plane then we put the lower rim and start adding or removing wax
according to our VDO.
** The next two pages contain classification of impression materials
and tables for materials used in both primary and secondary
impressions .. hope they'll be useful
Done by:
Eman Tawalbeh.
" It is amazing how a person can make your life very special "
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Materials for taking primary impressions
DisadvantagesAdvantagesMaterial
1- poor dimensional
stability.
2-syneresis (loss of water)
and imbibitions (sorption of
water).
1- elastic.
2- cheap.
3- good for deep undercuts.
4- used for dentate and edentulous
patients.
5- accurate.
Alginate
1. Poor dimensional stability.
2. Easy to distort when
withdrawn from the
Mouth.
1- reusable.
2- Non-irritant and non-toxic.Impression
compound
1- hydrophobic.
2- expensive.
1- accurate.
2- dimensional stability.
3- non irritant or toxic.
Rubber
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Materials for taking secondary impressions
DisadvantagesAdvantagesMaterial
1. Cannot be used in deep
undercuts.
2. Eugenol allergy in some
patients.
1. Low viscosity no compression of
soft tissues.
2. Dimensional stability (shrinkage less
than 0.1 %).
3. Good surface detail reproduction.
4. cheap.
Zink oxide
eugenol
(ZOE)
1- hydrophobic.
2- expensive.
1- accurate.
2- dimensional stability.
3- non irritant or toxic.
Rubber