3. ОПРЕЛЕЛЕНИЕ ЦО

1.

Determination of the central ratio of the jaws in the
complete absence of teeth. Biomechanics of the
lower jaw. Patterns of articulation and occlusion of
the dentition. Laws of articulation Bonvil, Hanau.
2022 Moscow

2.

Pathological processes in the dentition (caries, wear of hard
dental tissues, secondary deformations after tooth loss, etc.) lead
to the loss of central occlusion and the formation of "forced
occlusion". In this case, changes occur in the
temporomandibular joint, the articular heads are displaced,
there is no correct position of the head-disk-fossa complex.

3.

Signs of a violation of the relative position of the head and disk:
1.Clicking in the joint when opening and
closing the mouth;
2.Pain when trying to put the lower jaw in
the position of the central ratio;
3.Unable to relax muscles.

4.

One of the clinical stages of prosthetics for patients with a complete absence of teeth
is to determine the central ratio of the jaws using wax templates with occlusal rollers.
All modern methods for determining the central ratio are based on the fact that in a relaxed
patient, the articular heads are independently centered using a neuromuscular mechanism, if
there are no symptoms of musculo-articular dysfunction.

5.

To determine the central ratio of the jaws means to determine the
position of the lower jaw in relation to the upper one in three
mutually perpendicular planes: vertical, sagittal, transversal.
Prerequisites for the correct definition of the central ratio:
• relaxation of chewing muscles,
• fixing the patient's head on the headrest,
• upright position of the head

6.

7.

Determining the height of the upper bite block and
oval design in the vestibular region
The basis with a bite roller is applied to the
jaw and the line of closing of the lips is
marked. When in a relaxed position, the
upper lip should not be tense or sink. The
position of the lips is corrected by cutting or
building up wax on the vestibular surface of
the roller. Then the height in the anterior
section is determined: the edge of the roller
should be at the level of the lower edge of the
upper lip or protrude from under it by 1.0-1.5
mm. These landmarks will subsequently
determine the position of the artificial teeth.

8.

POSITION OF THE UPPER OCCLUSION ROLLER IN
RELATION TO THE UPPER LIP:
1 - ABOVE THE LIP; 2 - AT LIP LEVEL; 3 - BELOW
THE LIP.

9.

Formation of the occlusal plane
The formation of the prosthetic plane is carried out first in the anterior section, and then in the lateral ones.
On the roller, a plane is created parallel in the anterior section of the pupillary line, and in the lateral sections
- to the nasal or camper horizontal
In addition to the rulers, the Larin apparatus can be used to design the occlusal plane with the simultaneous
establishment of the upper occlusal roller.

10.

Using rulers to determine the prosthetic plane:
Larin apparatus:

11.

Advantages:
✓Ease of manufacture;
✓High production speed;
✓No toxic materials.
Flaws:
✓Requires special equipment;
✓Comparatively higher manufacturing cost;
✓Requires special materials;
✓The inconvenience of grinding the spoon (the material can melt and clog the
cutter);
✓There is no possibility of making supports for the fingers in the side of the
spoon;
✓It is necessary to isolate undercuts on the model.

12.

AFTER CONSTRUCTION OF THE PROTETIC
PLANE, THE LOWER ROLLER IS SUPPLIED
TO THE UPPER.

13.

DETERMINATION OF INTERALVEOLAR
HEIGHT
METHODS FOR DETERMINING THE
HEIGHT OF THE LOWER FACE:
Anatomical (based on restoring the correct facial configuration)
Anthropometric (based on the principle of proportionality of body
parts)
Anatomical and physiological (based on the use of the height of
the relative physiological rest of the lower jaw in combination
with anatomical data or with functional conversational tests)

14.

ANATOMO-PHYSIOLOGICAL METHOD
• The height of the lower part of the face is the distance between two points located
in a vertical plane on the upper and lower jaws (Subnasale - at the base of the
nasal septum and Gnation - the most protruding part of the chin) in their central
ratio.
• It is necessary to take into account the state of relative physiological rest of the
masticatory muscles (pre-occlusive state). At the same time, the chewing muscles
are in a state of some tone (physiological), the degree of contraction of individual
muscles is minimal, giving relative rest (physiological balance) to the entire
chewing muscles. The state of physiological rest is characterized by free closing of
the lips in the presence of a gap between the dentition (from 1 to 9 mm).
• To obtain the height of the lower part of the face in a central ratio, it is necessary to
subtract 2-3 mm from the height of the lower part of the face in the position of
relative physiological rest.
• Interalveolar height - the distance between the alveolar arches during tooth loss. In
the absence of antagonistic teeth, the interalveolar height and the height of the
lower face are interdependent.

15.

Anthropometric landmarks
1
2
1 - Subnasale; 2 - Gnation

16.

Fixation of the central ratio of the jaws
On the upper roller, in the region of the first premolars and molars, two notches not
parallel to each other are made with a sharp spatula, and a well-heated strip of wax
is applied to the lower occlusal roller.
The doctor places his index fingers in the region of the chewing teeth, inviting the
patient to touch the posterior third of the hard palate with the tip of the tongue and
close the jaws in this position.
Heated wax enters the notches of the upper jaw, creating locks, and the heated wax
plate is squeezed out from under the rollers, as a result of which the lower part of the
face is not overestimated.
Then the occlusal ridges are removed from the oral cavity and cooled.
Cut off excess crushed wax and check the central relationship of the jaws several
times.

17.

APPLICATION OF ANATOMICAL REFERENCES FOR
SETTING ARTIFICIAL TEETH
• The median line (landmark for setting the central
incisors) is an imaginary line passing between the
central incisors. From the scalp down straight
down the middle of the face. Without straying
from this line, a cut is made on the vestibular
surface of the upper occlusal roller.
• Canine lines (determines the width of the front 5
teeth) are lines that run along the axis of the
canines, corresponding to the wing of the nose.
• Smile line (determines the height of the front
teeth) - the line of the necks of the front teeth. It
is carried out along the border with the red
border of the upper and lower lips with a smile.

18.

BIOMECHANICS OF THE LOWER JAW
The biomechanics of the lower jaw should be considered from
the point of view of the functions of the dentition: chewing,
swallowing, speech, etc. Movements of the mandible result from
a complex interplay of masticatory muscles, TMJ, and teeth,
coordinated and controlled by the CNS. Reflex and voluntary
movements of the lower jaw are regulated by the neuromuscular
apparatus and are carried out sequentially. Initial movements,
such as biting off and placing a piece of food in the mouth, are
voluntary. The subsequent rhythmic chewing and swallowing
occur unconsciously.

19.

The lower jaw moves in three
directions: vertical, sagittal
and transversal. Any
movement of the lower jaw
occurs with the simultaneous
sliding and rotation of its
heads.
1
2

20.

Vertical movements that
characterize the opening of
the mouth are carried out
with active bilateral
contraction of the muscles
going from the lower jaw to
the hyoid bone, as well as
due to the gravity of the jaw
itself.

21.

The sagittal movements
of
the
lower
jaw
characterize
the
protrusion of the lower
jaw forward, i.e. a
complex of movements
in the sagittal plane
within the boundaries of
the movement of the
interincisal point.

22.

Transversal (lateral) movements of the
lower jaw are carried out as a result of
a predominantly unilateral contraction
of the lateral pterygoid muscle. When
the lower jaw moves to the right, the
left lateral pterygoid muscle contracts
and vice versa.

23.

The distance that the head of the lower jaw
travels when it moves forward is called the
sagittal articular path. It averages 7-10 mm.
The angle formed by the intersection of the line
of the sagittal articular path with the occlusal
plane is called the angle of the sagittal articular
path. Depending on the degree of expression of
the articular tubercle and tubercles of the lateral
teeth, this angle varies, but on average
(according to Gizi) it is 33°.

24.

The sagittal occlusal curve (Spee
curve) runs from the upper third
of the distal mandibular canine to
the distal buccal cusp of the
mandibular last molar.

25.

The angle formed between the lines of the
sagittal and transverse articular path is
called the angle of the transversal articular
path (“Bennett angle”) and is, on average,
17 °.

26.

The curves of the lateral
movements of the anterior teeth
intersect at an obtuse angle at the
interincisal point. This angle is
called gothic or transversal incisal
path angle. It determines the span
of the incisors during lateral
movements of the lower jaw and is
equal to an average of 100-110°.

27.

Laws of articulation BONVILLE, GANAU
The study of the compensation mechanism is of great
practical importance, because taking into account the
overlap of the lower teeth by the upper teeth and the
relationship between the depth of overlap, the steepness of
the articular path, the height of the tubercles and the
curvature of the Spee line is of great importance for the
stabilization of prostheses.

28.

Laws of Bonville
Bonville noticed a pattern between the elements of the chewing apparatus:
1. The distance between the centers of the articular heads and between them and the medial
angles of the lower incisors form an equilateral triangle, each side of which is 10 cm.
2. The depth of overlap in the area of the incisors is not arbitrary or random,
but depends on the height of the molars and premolars,
on the position of these teeth in the jaw arch and on the curvature of the entire dental arch.
The height of the bumps gradually decreases from premolars to molars.
3. The incisors determine all movements of the lower jaw in relation to the upper.
4. The vestibular surfaces of the anterior teeth lie in a circle, and the lateral ones lie in a straight line.
5. The line of closure of the molars is curved in the sagittal direction.
6. When moving the lower jaw to the sides on the working side, the same name is obtained,
and on the balancing - opposite names.
Bonville's laws emphasize the importance of taking into account the dependence between the various
elements of the articulatory chain.
The question of the leading significance of one or another element of articulation in the clinic of
prosthetics of edentulous jaws has been in the spotlight for many years.

29.

Laws of articulation GANAU
Hanau analyzes the system of articulation and especially
emphasizes the difference between the position of
prostheses in the articulator and in the mouth due to the
lack of consideration of tissue elasticity.

30.

Laws of articulation GANAU
From a number of articulatory laws, Hanau singled out 5 main
factors, calling them the articulatory five:
1 - inclination of the articular path,
2 - compensation curve depth,
3 - inclination of the reference plane,
4 - slope of the upper incisors,
5 - the height of the bumps.

31.

Laws of articulation GANAU
All these five factors can vary in different ways: the articular path, the
orientation plane and the position of the incisors - in the slope, the
compensation curve - in depth, the tubercles - in height. The existing
dependence of the values can be represented, for example, as follows:
an increase in the depth of the compensation curve leads to an increase
in the slope and vice versa. It should be noted, however, that the listed
elements of the articulation complex of the balancing theory are
difficult to accurately measure and take into account. This applies not
only to the inclination of the articular path, but also to the angle of the
cusps, occlusal cusps and occlusal plane.

32.

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