teeth setting - Weebly · So You know now about the selection of teeth. And we are ready to move to...
Transcript of teeth setting - Weebly · So You know now about the selection of teeth. And we are ready to move to...
. Done by: Rida alkhatib, Daniel atieh prosthodontics sheet#8____________________________________
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The first part of this sheet is written by Rida al Khatib and the second part is written by
Daniel attieh, according to section 2 record.
So You know now about the selection of teeth. And we are ready to move to the next
step:
teeth setting
*upper anteriors:
1) Setting of upper central incisor:
A) Tooth from the front: the long axis of the tooth diverges slightly from the midline distally and
the incisal edge contacts the occlusal table or the horizontal plane
B) Tooth from the side: the neck of the central incisor is depressed by 2mm and that create an
angle with vertical plane, and the incisal edge is in line with wax rim.
2) Setting of upper lateral incisor:
A) Tooth from the front: the incisal edge is shorter than the occlusal table by 1 mm, the long axis
is inclined more distally than the central incisor.
B) Tooth from the side: the neck of the lateral incisor is more depressed than the central incisor
creating an angle more than that for the central incisor with vertical plane. So this tooth is more
labially inclined.
. Done by: Rida alkhatib, Daniel atieh prosthodontics sheet#8____________________________________
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3) Setting of upper canine
(Placed at the angle of the mouth)
a) Tooth from the front: the long axis is almost upright, diverges slightly distally.
b) Tooth from the side: the long axis of the tooth is perpendicular on the horizontal
table. And the cusp of the canine touching the occlusal table. The cervical third is more
prominent than the cusp tip.
*you can see here the different inclinations of anterior teeth:
A B C
*harmony in the general arrangement of anterior teeth with:
-harmony of the incisal show and the patient age: younger patient shows more
incisor than the older patient.
-harmony of teeth with smiling line of the lower lip: if we extend a line between
upper canine to the other canine, this line should follow the curvature of the
lower lip during smiling regardless of the shape of the upper lip, also the vertical
positioning of upper canine is responsible for the shape of the smile line because
this line extend from the canine cusp tip of one side to canine cusp tip to other
side; and it should also touche the incisal edges of central incirsors.
A) Central incisor
B) Lateral incisor
C) canine
Tooth from the
side:
A) Central incisor
B) Lateral incisor
C) canine
Tooth from the
side:
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-harmony of the dental arch form and the form of the residual ridge, the
arrangement of the teeth must follow the shape of the arch:
arch is square in shape: the central incisors and canine are set on a line; to fit
the shape of dental arch
Arch is tapering in shape: the incisors are a greater distance forward from the
canines; and teeth have rotations and lapping.
Arch is ovoid in shape: the relationship between the incisor and canine is more
flat, and no rotation of teeth because the arch is wider; so more of the labial
surfaces of teeth are seen.
-harmony of the long axis of the teeth (central incisors) with the long axis of the
patient’s face; to give esthetic’s appearance to the patient.
Square form
Taper form
Ovoid form
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harmony of the opposing labial and buccal long axes of teeth: Balanced opposing lines.
Such as dissimilarities in the inclination, rotation, and position of the teeth on each side
of the midline provide what is called asymmetrical symmetry: when we look at the left
side and the right side, they are asymmetrical (they don’t show symmetry), but they
are symmetrical in another way; for example: if we look at the long axis of right lateral
incisor, it slopes distally, and when we look at the long ax of the left lateral is it slopes
distally as well (mirror image to each other).harmony of the long axes between upper
and lower teeth; when we look at the long axes of the lower teeth, it slopes distally as
well as upper teeth so the long axes appear as a continuous line between upper and
lower tooth.
*Lower anterior:
Lower Central incisors:
A) Tooth from the front: the long axis is almost vertical and slight mesial inclination to the
midline (according to incisal edge), less distal inclination than the lateral and canine
(according to root).
B) Tooth from the side: its positioned labially; which makes an angle with the
perpendicular plane.
Lower lateral incisor:
A) Tooth from the front: the long axis is slightly inclined mesially (according to incisal
edge), little distal inclination (according to root).
B) Tooth from the side: the long axis is vertical to the hohizontal plane.
Lower canine:
A) Tooth from the front: the long axis is more distally inclined (according to root).
B) Tooth from the side: the cusp of canine is lingually inclined and the cervical third is
prominent.
*the cervical third of the canine is prominent because the tooth has lingual inclination;
the tip of the tooth is more depressed lingually.
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**Two relationship between upper and lower teeth which are:
1) Static: A) vertical overlap (overbite),B) horizontal overlap (overjet) between upper
central incisor and lower central incisor.
2) dynamic: during function which is mainly (protrusive movement) lower central
incisors slide against the palatal surface of upper central incisors. This path is called the
Incisal guidance (is the path on the lingual surface of the maxillary anterior teeth along
which the mandibular anterior teeth glide).
Incisal guidance angle: angle between the incisal guidance and the horizontal plane.so
in the complete denture we need this angle to be as shallow as possible and not greater
than 15 degrees (to achieve balanced occlusion). If it’s greater than 15 degree posterior
teeth will have separation during protrusion
-the incisal guidance angel depend on vertical overlap (overbite) or the
horizontal overlap (overjet) between the upper and lower incisors, so if these
change, the angle will be different. (The dimension of the triangle will change
so the angle also will change.
** the relationship between upper and lower anterior teeth at centric
occlusion; how should the upper and lower anterior teeth be arranged:
Anterior teeth are set with a minimal vertical overlap(over bite) for about .5-1 mm, and the
horizontal overlap(overjet) around 1-2 mm to make an incisal angle as shallow as possible.
No contact between upper and lower anterior teeth; there is a separation between them, no
contact at centric occlusion; equidistance overjet: when we measure the horizontal overlap from
the lower canine to the lower canine on the other side, this horizontal distance is equal (Even
horizontal distance from the left side to the right side).
Shallow incisal guidance will enhance denture stability when we talk about balanced
occlusion.
. Done by: Rida alkhatib, Daniel atieh prosthodontics sheet#8____________________________________
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Here we are talking about the overbite and overjet which interact with each other
to give us the incisal angle:
-the triangle at the central: forming an angle of 15 degree
-the triangle at the upper right: overjet increase and the overlap is fixed; the angel is
reduced.
-the triangle at the upper left: overjet is fixed and the overbite is reduced; the angle is
reduced.
-the triangle at the lower left: overjet is fixed and the overbite increased; the angle is
greater.
-the triangle at the lower right: overjet is reduced and the overbite decreased; the angle is
greater.
Therefore, in order to obtain a shallow incisal angle; either we increase overjet or decrease
overbite.
This picture shows incisal relationship in different incisal classifications:
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Class 1: the lower incisal edge occludes with or lie immediately below the middle part of the
palatal surface of the upper central incisors.
Class 2: division 1: the upper central incisors are proclined or of average inclination and there is
an increase in overjet.
Class 2: division 2: the upper central incisors are retroclined: the overjet is minimal but may be
increased.
*setting upper posteriors:
First premolar:
A) Tooth from the front: the long axis is perpendicular to the horizontal plane or occlusal
table.
B) Tooth from the side: we can notice that the buccal cusp touching the horizontal plane or
occlusal table while the palatal cusp is shorter than the buccal cusp so it doesn’t touch
the horizontal plane or occlusal table (refer to arrow).
Second premolar:
A) Tooth from the front: the long axis is perpendicular to the horizontal plane or occlusal
table.
B) Tooth from the side: we can notice that the buccal cusp and the palatal cusp are in
contact with the occlusal table or the horizontal plane. (Refer to arrow).
. Done by: Rida alkhatib, Daniel atieh prosthodontics sheet#8____________________________________
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First molar:
A) Tooth from the front: the long axis slopes mesially (according to root).
B) Tooth from the side: all the cusps are not contact with the horizontal plane
except mesiopalatal cusp; so the mesiobuccal cusp is about 0.5mm higher than
the occlusal table while the distobuccal cusp is much higher than the MBC;
around 1mm.
First premolar and second premolar and the first molar from the occlusal view:
A line: a line extending from the distal surface of the canine touching the buccal surface of the
first premolar and second premolar and the MB surface of first molar, and this line will
continuous with the distal surface of the canine.(refer to arrow)
That mean there is a continuation of arrangement to produce an arch shape between
the anterior teeth and the posterior teeth.
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Second Molar
- Long axis slopes more mesially (because we can see the occlusal surface) a bit more than first
molar (buccal view). The occlusal surface faces distally and buccaly.
- All four cusps do not touch the lower occlusal rim but the mesiolingual cusp is the nearest.
B- LINE
This second line contacts the buccal surface of the buccal
cusps of first molar and second molar.
The two lines (A & B) will achieve the curve of the arch
that is required.
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SETTING MANDIBULAR TEETH - GENERAL STEPS TO ACHIEVE
Long axis of all lower teeth must be perpendicular to the horizontal plane which
means no inclination in all lower posteriors
these teeth are set in centric occlusion (maximum intercuspation/contact
between upper and lower teeth). No spaces should be seen specially in posterior
teeth, but buccal over-jet should be present to prevent cheek biting.
in order to produce this max intercuspation, you either reduce the size of
marginal ridges of upper and lower teeth, or slight spacing in upper teeth.
should allow sufficient, equidistant buccal over-jet in order to prevent cheek
biting.
we always start with the lower first molar in setting
lower first molar is placed over the crest of the lower ridge and its central fossa
occludes with the mesio-palatal cusp of the upper first molar
You need to look at the relationship between upper and lower teeth in centric
occlusion (table in the slides). For example: (1) palatal cusp of upper first
premolar occludes with the distal triangular fossa of lower first premolar (note
that we talk about maxillary lingual cusps because they are the functional cusps
of upper teeth).
(2) For second premolar, palatal cusp of upper tooth contacts distal triangular
fossa of lower second premolar (3) For the first molar, the mesiopalatal cusp of
the upper contacts central fossa of lower first molar and the distolingual cusp of
the upper contacts distal marginal ridges of lower first molar and mesial
marginal ridge of second molar.
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Compensating curves:
Two curves created in artificial teeth while setting to stimulate
curve of spee and
Monson, as they exist
naturally. Those two
cruves are: A =
Anteroposterior curve
similar to curve of
spee, B= lateral curve
similar to curve on Monson
BALANCED OCCLUSION AND ARTICULATION
The mandible in real life is not static, but is dynamic. Think about
grinding food, which produces dyamic mandible movement
involving protrusion and lateral movements. Those are the
horizontal movements produced (lateral + protrusive movements
i.e. eccentric). Vertical movements also take place.
So let's talk a bit more about the horizontal relations (centric and
eccentric relations). Centric relation have many definitions, but a
simple one describes the position of the maximum retrusion of
the mandible in which lateral movements can be produced. It may
or may not coincide with maximum intercuspation. While
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producing the complete denture, we do it so that centric relation
= maximum intercuspation.
The eccentric relations describe the lateral and protrusive
movements produced as mentioned.
Now let's go back to our main topic concerned with balanced
occlusion. In order for all those dynamic movements to be
achieved and be successful, we must ensure that the denture
remains stable and does not dislodge by keeping teeth in contact
together to provide support.
Balanced occlusion means that there should be a bilateral,
simultaneous contacts between upper and lower teeth in centric
and eccentric positions of the mandible i.e this is a static
relationship.
Balanced articulation is actually the same idea of bilateral, even
contact between upper and lower teeth, but this is during
movement like sliding for protrusion movement (changing from
centric position to eccentric) i.e a dynamic relationship.
In average value articulator, we can achieve balanced occlusion
but not the balanced articulation because you will need to record
the condylar guidance angle exactly as it is in the patient.
Example - during lateral movement
if mandible moves to the right, then the right side is the working
side and the left side should be the balancing side (in order to
prevent dislodgment - that's only one advantage actually).
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One more thing to note is that the condyle that moves is not the
one on the working side but on the balancing side. Working side
condyle show minimal movement in position only.
In this figure, A is the balancing
side and B is the working side.
Note that during this lateral
movement of the mandible,
buccal cusps of upper meet
buccal cusps of lower and lingual cusps of upper meet the lingual
cusps of upper on the working side. However, on the balancing
side, the palatal cusp of upper meet the buccal cusp (the lingual
incline part of the buccal cusp) of the lower.
Example - during protrusion movement
in the same way, we should achieve the contacts between
teeth, so that the incisal edges meet anteriorly and at the
same time have posterior contacts of teeth to avoid
dislodgement. The more posterior the contacts, the better,
but if we can achieve at least one on each side then it will
be sufficient.
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Advantages of Balanced Occlusion:
1) allows the denture to be seated during activities such as eating, speaking etc.
2) If the denture is unseated properly, it will keep moving with different activities,
and this will lead to soreness and inflammation, and will also accelerate the bone
resorption.
3) Enhance retention and stability during activities (actually this is related to
point 1).
Factors that influence Balanced Occlusion:
We have incisal and condylar guidance on one side. And we have
cusp angles, orientation of occlusal plane, and compensating
curves on the other side. The reason we put them in separate
groups is because increase in one side will need to be balanced by
an increase on the other side to maintain the balance and so on.
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