Prostho Lab 7 ,Anterior Teeth Setting

8/3/2019 Prostho Lab 7 ,Anterior Teeth Setting

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T EETH SETTING

In dentures we try our best to reestablish esthetics, phonetics and function, but

we still have problems and it's far away from being perfect! As commonlyknown in general prosthodontics, the prosthesis (whether a denture or a maxillo-

facial prosthesis or any other replacement of a part of the body) will never be

exactly the same as the lost body part, or as good as Allah's creation.

If someone loses a limb and gets a prosthesis, he doesn’t expect that it will be

as good as his natural limb, but unfortunately in dentures, our patients tend to

have this false expectation, they feel that the denture should feel as comfortable

as their natural teeth! This is impossible! So a large part of our job is to dealwith patients psychologically, and give them the correct expectation of whatthe denture will be like, and this should be discussed with the patient on the first

visit.

Unless you talk the patient through all of this, he will be surprised when he

gets the final denture and neither of you will be happy! So keep them informed

and give them the true expectation of what the denture will be like!

What do you know about natural occlusion? What's so special about natural

teeth?

N ATURAL VS. ARTIFICIAL TEETH

The main thing that distinguishes natural teeth from artificial teeth is that

each natural tooth is attached to the bone through the PDL, that means each

individual natural tooth is a unit by itself , if it moves it moves alone, if it

fractures it fractures alone, if it is extracted it's extracted by itself .

However in dentures (partial or complete), all teeth are attached to the

denture's base, the denture is considered as one big unit (as if it was one big

tooth).

In other words the functioning unit in natural teeth is every tooth on its own,

but in dentures the whole upper or lower denture is one big functioning unit.



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Why is this significant?? Because every time a patient with denture bites on

something on one side the other side will be affected, or if he bites an apple in

the front the back tends to come down a bit.

In dentures we have 28 teeth (we don’t set third molars), 14 in the upper jaw

and 14 in the lower jaw, the company sends us 28 teeth per set.

In jaw relationship records, we have four steps as discussed earlier:

1) Vertical relationship

2) Horizontal relationship

3) Face-bow transfer records

4) Tooth selection

In the horizontal relationship, we talked about centric relation (maximum

intercuspation for denture teeth equals centric relation, but in natural teeth it's

not the same).

In natural teeth, the patient chews on one side which we call the working

side, the other side is called the non-working side because the teeth don’t

touch, and this is normal, if they touch we call it interference and it's bad.

However in dentures when the patient chews on one side (working side), the

teeth are designed to contact each other on the other side (balancing side).

Why do we design denture that way?

Because when the patient chews, we want some kind of support on the other

side, otherwise the denture will fall off or move; it will cause instability andloosening of the denture. There for we design the denture so that teeth are in

contact at all times and in all movements, whether centric or eccentric.



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In horizontal relation, after we learned about Centric Relation we will learn

about what we call Eccentric Relation.

Eccentric relation represents all other movements other that the centricrelation and we use these movements daily. In fact, the time spent in centric

relation is very minimal (about 15 min daily), so the majority of the time, our

teeth is in eccentric relation which includes lateral, protrusive and retrusive

movements such as chewing.

Centric relation is a static relation (it's the zero point), while eccentric

relation is a dynamic relation (right, left and forward movements and

everything in between).

The patient is going to chew in dynamic relationship, that means we have todesign the teeth so that when the patient chews on the right, the teeth will

contact evenly on the left, and when he bites forwards the teeth will touch

posteriorly as well, and this is a little bit more complicated than it sounds, and

we call this type of symmetry Balanced Occlusion.

In natural teeth we don’t have balanced occlusion.

In the balanced occlusion we have a working and a balancing side and the

teeth touch in both, while in natural teeth we have a working and a non-working

side and the teeth should only touch on the working side.

Main differences between natural teeth and dentures:

1) In natural teeth each individual tooth is an independent unit ,

while in dentures the whole upper or lower denture is one big

functional unit .

2) In natural teeth when you chew, the teeth on the working side

touch but they don’t touch on the non-working, while in dentures

we have BLANCED OCCLUSION, and teeth touch on both the

working and balancing side.



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We are going to learn to set the teeth in centric relation (static relationship)

but we are not going to create balanced occlusion, because our denture opens

and closes in one position so we are not concerned with other movements.

HOW TO CREATE BALANCED OCCLUSION?

Even though we will not be doing this in lab but it is a very important part of

making dentures that you need to know in some detail.

We have five factors affecting occlusal balance (HANAU's QUINT):

1) Condylar inclination

2) Incisal guidance3) Occlusal plane

4) Cusp angle

5) Compensating curves (CC)

Using and varying these five factors we can create balanced occlusion.

1) C ONDYLAR INCLINATION

o It's an anatomical position, it is fixed.

o It can't be controlled by the dentist.o It's the angle between the condyle and the articular eminence.



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2) INCISAL GUIDANCE

o Incisal guidance: Relates the overbite with the over jet.

o It is usually expressed in degrees of angulations from the horizontalocclusal plane by a line drawn between the incisal edges of the upper and

lower incisor teeth when closed in centric occlusion.

3) OCCLUSAL PLANE

Which we made according to camper's plane and was previously discussed.

4) C USP ANGLE

Companies provide us with teeth with variant cusp angle, which ranges

from sharp to almost flat cusps.



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5) C OMPENSATING CURVES

Instead of making the arch flat, we create a curve in it, and this is one of themost important ways to maintain balanced occlusion. We design the teeth tohave some degree of curvature.

We need this curve to be present antero-posteriorly and laterally.

In natural teeth we have two curves:

1) Curve of spee

2) Curve of Wilson

CURVE OF SPEE:o If we draw an anterio-posterior line touching the cusp tips and incisal

edges of mandibular teeth we will end up with is a smooth, linearcurve which is called the curve of Spee.

o It is viewed from the lateral aspect.





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o TWO TYPES:

1) Antero-posterior CC: They compensate for the curve of spee seen in

natural teeth.

2) Lateral CC: They compensate for the curve of Wilson seen in natural

teeth.

SEQUENCE OF TEETH SETTING

1) Upper anterior

2) Lower anterior

3) Upper posterior

4) Lower posterior

Upon setting teeth, we are going to face a problem which is the loss of our

occlusal plane reference which is the wax. Because as I set teeth most of the

wax will be melted away! And that’s where the plastic sheet comes in. It will

be my occlusal plane reference as wax will be lost and disfigured. This sheet is

flat so I create the curves by raising the teeth above it as much as I want. The

metal sheets are the best and the easiest to use but the plastic sheets are fine.

- Curve of spee and Wilson are only present in natural teeth.

- Compensating curves are present in dentures

- However we sometimes use Spee and Wilson to talk about

dentures and you will find some books that confuse the two

terms also.



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SETTING OF ANTERIOR TEETH

Before we start setting, we should:

1) Check the articulator :a) Incisal pin position is correct.

b) Condyles don’t move.

2) Have the midline marked:

a) Marked in the clinic for actual patients: Use midline of the face not

the mouth or nose.

b) Marked on the cast in our lab

After you mark the midline on the cast, mark it on the occlusal rim and on the

base plate so you don’t lose it. It's CRITICAL that you mark the midline

correctly as any shift will cause all the teeth to shift to one side which is not

acceptable.

3) Draw a template on the plastic sheet as a reference for the occlusal

plane to stay oriented.

To set teeth correctly you should know that each tooth has a specific:

1) Mesiodistal inclination

2) Buccolingual inclination

3) Correct relationship with the occlusal plane.

To mark the midline on the cast, use the anatomic land marks like

the incisive papilla and labial frenum anteriorly, and the fovea

palatini posteriorly. But be careful because on our cast the fovea

palatini aren't completely centered in the midline (the midline

touches the right fovea palatini)



Following the sheet (Setting of Anterior Teeth) we have:

Central incisor:

o Incisal edge touches the occlusal plane.o The neck is slightly distally inclined (about 5

o).

Lateral incisor:

o Raised above the occlusal plane by 0.5-1.0 mm (the more its raised the

more feminine the teeth look)

o The neck is more distally inclined (about 10o)

Canine:

o Touches the occlusal plane

o The neck is again more distally inclined (about 10o-15

o)

Anterior View of Upper Anterior Teeth



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Central incisor:

o The facial surface is at right angle with the occlusal plane: this means

that the overall tooth will have a slight 5o-10

oproclination.

o Natural teeth have planes, if we had a root it would appear as if part of

the tooth is on one axis and the other part of the roots is on a different

axis. We want the facial axis of the tooth to be at right angles with the

occlusal plane, this will give the entire tooth a slight proclination.

Lateral incisor:

o The neck is more palatal (it's further in, or more deep)o It looks smaller because it's raised from the occlusal plane and because

the neck is further inside.

Canine:

o It is a prominent tooth with a large crown and root.

o It is the corner of the arch and it provides support.o The whole axis of the tooth is at right angles with the occlusal plane,

this will make the facial surface or the belly of the canine look prominent.

What we have so far:

Central incisor:o Touching the occlusal plane.o

Mesiodistally: the neck is located slightly distally (5

o

)o Buccolingually: the axis of the whole tooth is slightly proclined (5

o-10

o)

Lateral View of Upper Anterior Teeth



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Lateral incisor:o Raised about 0.5 – 1.0 mm

o Mesiodistally: the neck is more distally inclined (10o)

o Buccolingually: the tooth axis is more proclined. The neck is more

palatal. And our concentration is not so much on the proclination as muchas it is on the neck being depressed.

Canine:o Touching the occlusal plane.

o Mesiodistally: the neck is again more distally inclined (15o)

o Buccolingually: the tooth axis is upright. (the bulge is more apparent)

These criteria are for each tooth alone, but the wax rim is what determinestheir places in the arch according to the shape of the patient's mouth. Too

narrow wax rim will give V-shaped arch and too wide will give a more flat arch.

If the wax is not symmetrical, use the setting plate to set the anterior teeth.

And it can be used only for anterior teeth because the template we have is too

wide for the posterior.

The upper anterior over lap the lower anterior.

The horizontal distance is called: Horizontal Overjet (HO) The vertical distance is called: Vertical overbite (VO)

Lower Anterior Teeth



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Normal overjet and overbite Normal incisal guidance.

Longer overjet or shorter over bite incisal guidance less steep

(more horizontal)

This is a factor in Hanau's Quint that we already discussed. It is the

incisal guidance.

To understand the incisal guidance follow these three examples:



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Shorter overjet or longer overbite incisal guidance very steep

(more vertical)

The appropriate overbite and overjet are 1 mm for both, but it isacceptable to have it from 0.5-2.0 mm.

Teeth don’t touch.

Incisal edges of lower anterior teeth are above the incisal edges of upper

anterior teeth; hence the incisal edges of lower anteriors are above theocclusal plane. So their incisal edges will be slightly above the wax rim.

ACRYLIC TEETH

Teeth are provided from the companies in different molds, they differ in:- Size

- Shape

- Shade

The shape: usually we have three basic shapes:-

Square Triangular

Round or ovoid

Or we can have a hybrid shape such as triangular square or square ovoid.



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An over view of a set of acrylic teeth:

A major problem that students face is confuse the right and left teeth,

or lower and upper, because later on we won't have much teeth left. Becareful because this will affect your mark significantly

Write on the corners whether these are left or right so when you haveless teeth you don’t get confused between right and left or upper or

lower.

Or you can mark on the teeth themselves in some way that makes you

recognize them.

Do not lose these teeth! There are no replacements!

Patient's Right Patient's left Patient's Right Patient's left



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3

4

2

3

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Now what do these letters stand for?

Done By:

Anwar Durrah.

عيجل عست ضرا هذ..نح مإو نح مف!!

The name of the mold of the upper anterior teeth. It indicates the

shape and size according to a catalogue provided by the company.

The Shade:

A: (the Hue: Basic color) 1: (the value: light or dark)

The name of the brand: Yamahchi New Ace

This is called carding wax of the family of utility wax.

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Prostho Lab 7 ,Anterior Teeth Setting