Inalienable clinical stage prosthetics is the calculation of central occlusion.
From this article you will learn about all important factors, which should be taken into account in order to correctly record the CO, what stages of the procedure and determination methods are used, which means control of correctness.
Central occlusion can be characterized by muscle, articular and dental characteristics.
For muscle signs characterized by uniform tension of several muscle groups at the same time (masticatory, temporal, medial).
For articular signs characteristically, the articular convexity of the lower dentition is adjacent to the posterior slope of the articular tubercle.
For dental signs Characteristic features of jaw compression in comparison with all teeth, as well as frontal and lateral.
Features of contact for all teeth are as follows:
Signs of connection of anterior teeth:
Signs of contact of the lateral incisors:
In case of partial absence of teeth, prosthetics is performed, which involves determining the central occlusion. Incorrect fixation of central proportions can lead to many undesirable aesthetic and functional consequences.
The CO can be determined in the following ways:
In order to install the CO, a wax roller is carefully placed on the lower row of teeth and adjusted to the upper one. Then the mesiodistal position of the jaws is determined.
Since the lower line of the chin is fixed by natural teeth, centric proportions are established without the use of occlusal ridges.
This technique for calculating the CO consists of fixing maximum quantity chewing contacts. It is permissible to use this technique in the absence of two lateral or four frontal teeth.
To determine the correct location of the teeth in the central comparison, the following technique is used:
To do this, a softened warm strip of wax is glued to the chewing surface of the fitted roller and inserted into the growth cavity, after which the patient quickly clenches the jaw until the wax has cooled.
As a result of such actions, an impression is formed on the wax strip, according to which the design of the prosthesis is made in a central comparison;
A small layer is cut off from the bottom roller, then a warm strip of wax is applied on top. When the patient clenches his teeth, the wax lining of the lower roller in the form of wedge-like protrusions is inserted into the grooves of the upper one.
The height of the lower point of the face is great value in orthopedic dentistry.
Measurements of this area are necessary to achieve the best esthetic results, to improve dental contacts in normal functioning conditions, as well as to create space in the vertical plane.
Dentists need to set the size lower section individuals using the following methods:
To return the correct contours of the face, one should take into account the fact that while measuring the interalveolar height, the patient must completely close his lips without straining them. This method is usually used in conjunction with the other two.
To measure the height of the lower point of the face, the patient needs to move the lower jaw, and then lift it and slightly close the lips.
In this position, the specialist makes the necessary measurements and subtracts three millimeters from the resulting figure. This sets the height of the lower point of the face in the central comparison.
Many experts use certain techniques to accurately calculate lower jaw in the CO.
For example, the patient is required to clench his jaw and swallow saliva. The second technique is that the patient should touch the soft palate with his tongue.
In addition, the patient needs to touch right hand(palm) to the chin, close your mouth, and while doing this try to push your jaw back (without fixing the central point).
When the patient closes his mouth, imprints formed by antagonizing pairs remain on the bite ridge, which are subsequently used to create prosthetic structures.
Errors when calculating CO are classified into groups.
As the bite increases, the patient experiences tense clenching of the lips, a slightly surprised facial expression, an elongated chin, and teeth chattering when speaking.
To eliminate this error, with an increased bite height due to lower teeth, the rollers should be remade only for the bottom row.
If the height is increased due to the upper incisors, new ridges are required only for upper jaw. Next, you need to calculate the CO again and set up the teeth.
When the bite is lowered, the patient notices clearly visible nasolabial wrinkles, chin skin folds, sunken lips, drooping tips of the mouth, and slight shortening of the chin.
When understated only due to the lower teeth, the rollers are remade for the lower jaw. But if the height is reduced due to the upper incisors, both rollers are remade. After this, the CO is redefined.
If the lower jaw is not fixed in the central alignment, but in the frontal, posterior or lateral (right, left).
In frontal position a prognathic bite, tubercular contact of the lateral incisors, and a small gap between the front teeth can be seen.
When positioned laterally– increased bite, slight gap between displaced teeth.
The most common mistake is fixing the lower jaw pushed forward when measuring the CO.
To correct it, converted ridges are installed on the sides of the lower jaw. If the lower jaw is displaced back, new ridges are installed over the entire bottom surface teeth.
Because patients often fixate their jaws in incorrect positions, it is not easy to establish an accurate CO.
If there is no contact between some antagonistic pairs, this can be explained by the following factors:
The main signs of these defects are the lack of contact between the lateral teeth on one or both sides.
They can be eliminated by applying a not too heated wax strip to the chewing surface of the teeth. After which, you need to fix the bite again.
Signs of this error are an increase in the bite, a gap between the front teeth, and an uneven cuspal connection. chewing teeth. The error is eliminated with the help of bite rollers with rigid bases.
The video provides additional information on the topic of the article.
In conclusion, it can be noted that central occlusion should be determined qualified specialist, taking into account the anatomical physiological characteristics dentition.
Only after a thorough check of the central organ, detection and correction of errors, can wax casts be plastered into the articulator and sent to the laboratory for the manufacture of prostheses.
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Muscle signs: the muscles that elevate the lower jaw (masticatory, temporal, medial pterygoid) contract simultaneously and evenly;
Joint signs: the articular heads are located at the base of the slope of the articular tubercle, in the depths of the articular fossa;
Dental signs:
1) between the teeth of the upper and lower jaw there is the most dense fissure-tubercle contact;
2) each upper and lower tooth closes with two antagonists: the upper one with the same and behind the lower one; the lower one - with the same name and the one in front of the upper one. The exceptions are the upper third molars and lower central incisors;
3) the midlines between the upper and central lower incisors lie in the same sagittal plane;
4) the upper teeth overlap the lower teeth in the frontal region by no more than ⅓ of the length of the crown;
5) the cutting edge of the lower incisors is in contact with the palatal tubercles of the upper incisors;
6) the upper first molar meets the two lower molars and covers ⅔ of the first molar and ⅓ of the second. The medial buccal cusp of the upper first molar fits into the transverse intercuspal fissure of the lower first molar;
7) in the transverse direction, the buccal cusps of the lower teeth overlap the buccal cusps of the upper teeth, and the palatal cusps of the upper teeth are located in the longitudinal fissure between the buccal and lingual cusps of the lower teeth.
Muscle signs: this type of occlusion is formed when the lower jaw moves forward by contraction of the external pterygoid muscles and horizontal fibers of the temporal muscles.
Joint signs: the articular heads slide along the slope of the articular tubercle forward and down to the apex. In this case, the path taken by them is called sagittal articular.
Dental signs:
1) the front teeth of the upper and lower jaws are closed by the cutting edges (end-to-end);
2) the midline of the face coincides with the midline passing between the central teeth of the upper and lower jaws;
3) the lateral teeth do not close (tubercle contact), diamond-shaped gaps form between them (disocclusion). The size of the gap depends on the depth of the incisal overlap during the central closure of the dentition. It is greater in persons with a deep bite and absent in persons with a straight bite.
Muscle signs: occurs when the lower jaw shifts to the right and is characterized by the fact that the left lateral pterygoid muscle is in a state of contraction.
Joint signs: V In the joint on the left, the articular head is located at the top of the articular tubercle and moves forward, down and inward. In relation to the sagittal plane, it is formed articular path angle (Benett's angle). This side is called balancing. On the offset side - right (working side), the articular head is located in the articular fossa, rotating around its axis and slightly upward.
With lateral occlusion, the lower jaw is displaced by the amount of the cusps of the upper teeth. Dental signs:
1) the central line passing between the central incisors is “broken”, displaced by the amount of lateral displacement;
2) the teeth on the right are closed by the cusps of the same name (working side). The teeth on the left meet with opposite cusps, the lower buccal cusps meet the upper palatal cusps (balancing side).
All types of occlusion, as well as any movements of the lower jaw, occur as a result of the work of muscles - they are dynamic moments.
The position of the lower jaw (static) is the so-called a state of relative physiological rest. The muscles are in a state of minimal tension or functional equilibrium. The tone of the muscles that elevate the mandible is balanced by the force of contraction of the muscles that depress the mandible, as well as the weight of the body of the mandible. The articular heads are located in the articular fossae, the dentition is separated by 2 - 3 mm, the lips are closed, the nasolabial and chin folds are moderately pronounced.
Bite
Bite- this is the nature of the closure of teeth in the position of central occlusion.
Classification of bites:
1. Physiological occlusion, providing full function of chewing, speech and aesthetic optimum.
A) orthognathic- characterized by all the signs of central occlusion;
b) direct- also has all the signs of central occlusion, with the exception of the signs characteristic of the frontal region: the cutting edges of the upper teeth do not overlap the lower ones, but are butted (the central line coincides);
V) physiological prognathia (biprognathia)- the front teeth are inclined forward (vestibular) along with the alveolar process;
G) physiological opistognathia- the front teeth (upper and lower) are inclined orally.
2. Pathological occlusion, in which the function of chewing, speech, and a person’s appearance are impaired.
a) deep;
b) open;
c) cross;
d) prognathia;
d) progeny.
The division of occlusions into physiological and pathological is arbitrary, since with the loss of individual teeth or periodontopathies, teeth are displaced, and a normal occlusion can become pathological.
Determination of the central relationship of the jaws is carried out in the clinic and is preparatory stage necessary to continue laboratory work on the design of dentures.
Determining the central relationship of the jaws consists of the following steps.
Determination of the height of the occlusal ridge for the upper jaw. The lower edge of the occlusal ridge of the upper jaw should be flush with the upper lip or visible from under it by 1.0-1.5 mm. In the future, the cutting edges of the upper front teeth will be located at this level, which is important for aesthetics and maintaining natural diction.
Determination of the prosthetic plane along the pupillary line for the anterior teeth and along the nasal line for the lateral teeth.
Determination of the height of the lower part of the face. In case of complete absence of teeth, the occlusal height is established, i.e. the distance between the alveolar ridges of the upper and lower jaws in the central
Rice. 186. Guidelines marked on the occlusal ridges for the selection and placement of teeth.
1 - middle line; 2 - smile line; S - lower edge of the occlusal plane; 4 - line of fangs.
Rice. 187. Cross-shaped cuts on the occlusal ridge for the upper jaw (a) and their imprints on the ridge for the lower jaw (b).
occlusion according to the position of the lower jaw in a state of physiological rest.
Fixation of the central relationship of the jaws.
Applying landmarks to the vestibular surface of wax rolls. On the occlusal ridges, the doctor marks the main landmarks necessary for the dental technician to construct dentures for edentulous jaws (p. 186).
The median line serves to correct setting central incisors and the symmetry of the arrangement of all teeth. The smile line determines the level of the necks of the anterior teeth, i.e. their vertical size, equal to the distance from the level of the occlusal (prosthetic) plane to the smile line. The canine cusps are located on the canine lines, and the distance between the midline and the canine line is equal to the width of the central, lateral incisors and half of the canine on each side. The lines of the smile and fangs determine the choice of shape, size and type artificial teeth according to the patient’s face type, which the doctor makes a note about in the order.
The vestibular surface of the occlusal ridge determines the location upper lip and its red border, since it is a guide for the location of the vestibular surfaces of the incisors and canines, which will serve as support for the upper lip. The prosthetic plane guides the dental technician when setting teeth in creating sagittal and transversal compensation curves.
Occlusal height is necessary to establish the interalveolar height and position the teeth in this space. Fixing the occlusal height and position of the lower jaw in central occlusion contributes to the correct orientation of the model of one jaw in relation to the other and is necessary for plastering the models into the articulator.
The relief of the design of the vestibular surface of the occlusal ridge of the base for the lower jaw determines the type of relationship of the dentition; orthognathic, direct, progenic or prognathic.
In order to, after removing the bases with occlusal ridges from the oral cavity, fold them in the position of the found central relationship of the jaws, the doctor makes retention wedge-shaped or cross-shaped cuts on the upper ridge in the area of the first molars on the right and left (Fig. 187). In the areas of the lower roller corresponding to these cutouts, a layer of wax 1-2 mm thick is removed and a heated wax plate 2 mm thick is applied. The doctor reinserts the bases with occlusal ridges into the oral cavity, the patient closes the jaws in the position of central occlusion and the softened wax of the lower roller enters the recesses on the occlusal surface of the base roller of the upper jaw. The bases connected in this way are removed from the oral cavity, cooled, separated and reinserted into the oral cavity for a final check of the correctness of determination and fixation of the central occlusion. Wax bases with rollers are cooled, applied to plaster models, the bases of which are fastened together. The dental technician receives them in this condition. He places and plasters the bonded models into the articulator.
Central occlusion is a type of articulation characterized by uniform and maximum tension of the muscles responsible for raising the lower jaw. The maximum number of points coincide when the jaw closes, which can contribute to the formation of a malocclusion.
Occlusion is common in young children due to prolonged use of nipples, bad habits or diseases. The problem is diagnosed during the first visit to the dentist after the examination. Before the child reaches adulthood, it can be easily corrected. After 16 years, treatment of occlusion will be more difficult, and it will not be possible to completely correct the bite: in mature age You can only correct the problem a little.
In dentistry, correct occlusion consists of long-term and proper operation dentofacial apparatus without distortion of facial features. When groups of incisors of both jaws come into contact, this is called direct occlusion.
A sign of articulation is any use of the jaw during speaking, singing and swallowing. Occlusion is closely related to bite. Correct bite is determined by heredity - genes influence the formation of the jaws, determining what type of bite the child will have.
The main reasons that influence the formation of deviations in correct bite:
Correct swallowing is developed in a child by the age of three. The presence or problems with the tonsils leads to deviations in swallowing, which causes pathological swallowing in a four-year-old child. Such deviations become the causes of the development of abnormal occlusions of the jaws.
At this time, it is very important to correct the central relationship of the jaws, which only a specialist can do. Bye jaw apparatus It is plastic; it will not be difficult for an orthodontist to make a correction.
The earlier a problem is identified, the easier it is to correct it and prevent complications from the anomaly, which will negatively affect the process of eating and digesting food. Digestive problems may occur.
The classification of occlusions is based on the motor function of the movable jaw, and the relationship of the jaws to each other is also taken into account:
The sooner it is revealed pathological development relationship of the jaws, the better the problem can be corrected.
Each type of occlusion has a number of specific characteristics by which the types of deviation can be differentiated.
The main signs of occlusion are divided into three large groups:
Signs of central occlusion:
Dental features consist of the following features:
Fixation of central occlusion is determined by the closure of dental arches with a large number of tubercles when the jaw is at rest. The vertical line on the face is located along the dividing line between the central incisors, without pathological change joint
Signs of anterior occlusion:
Signs of lateral occlusion:
Movement of the jaws is carried out with the help of muscles. If the bite is disturbed, pathological placement of the jaws relative to each other can be diagnosed.
Pathology leads to the formation of malocclusion. Types and features of deviation:
The physiological occlusion is normal, does not distort facial expressions and performs functions while maintaining articulation.
Any type of malocclusion is identified when visiting a dentist after an external examination by a specialist; sometimes an X-ray examination is prescribed to clarify the pathological picture.
You can correct your bite up to the age of 16, but after that it is not possible to make a correction, especially in severe cases.
Methods for determining central occlusion:
After research and diagnosis, the dentist selects an individual correction method for the patient, taking into account the age characteristics of the child’s body.
In case of minor deviations from physiologically correct occlusion, the patient may not be prescribed any treatment in the absence of discomfort and problems with chewing and articulation.
If the child needs minor correction, orthodontic structures, most often braces, can be used.
After examination by a specialist, the patient may be offered the following options corrections:
In case of complete absence of teeth, prosthetics are performed, which will help restore the central position of the jaws and correct central occlusion.
Before installing the prosthesis, special impressions are made. In prosthetics there is large selection models that can be removable or permanent.
The main complications of malocclusion:
TO preventive measures include the following:
Pathology of the jaw relationship requires specific treatment, therefore, if symptoms occur, you should consult a dentist. Ignoring the problem will lead to severe irreversible complications, since in adulthood, correction of occlusion is impossible.
Central occlusion is the position from which the lower jaw begins its path and in which it ends.
Central occlusion is a functional position, not a static one. Throughout life, the height of central occlusion changes and depends on the wear and presence of chewing teeth. These conditions are combined with changes in the TMJ.
Central occlusion is characterized by maximum contact of all cutting and chewing surfaces of the teeth; muscles in the position of central occlusion develop maximum muscle traction; in this position, the most effective crushing of food occurs; the chewing and temporal muscles themselves on both sides contract simultaneously and evenly; the midline of the face coincides with the line passing between the central incisors of the upper and lower jaws; the articular heads are located on the slope of the articular tubercles, at their base.
L.V. Ilyina-Markosyan (1973) introduced the concept of habitual occlusion, which is characterized by various displacements of the lower jaw. With these displacements, there is no coordinated work of the masticatory muscles and the TMJ. There is also a retrusive (extremely posterior position) of the lower jaw, from which it cannot be displaced distally, since its displacement is limited by the lateral ligaments of the joint. In a retrusive position, the lower jaw moves posteriorly from the central occlusion by 0.5-1 mm and in 90% of cases does not coincide with the central occlusion.
It is necessary to know the listed positions of the lower jaw in relation to the upper jaw, since in clinical practice they are sometimes encountered.
When fitting prosthetics to patients with complete absence teeth determine the central relationship of the jaws, and not the central occlusion, since at this stage there are waxy occlusal ridges, and not dentition. Determining the central relationship of the jaws means determining the position of the lower jaw in relation to the upper jaw in three mutually perpendicular planes: vertical, sagittal and transversal.
All methods for determining the central relationship of the jaws can be divided into static and functional.
Static methods. These methods are based on the principle of constancy of the central relationship of the jaws. This is the method of Jupitz, who proposed the golden ratio compass; Watsward's method, which stated that the distance between the corner of the eye and the corner of the mouth is equal to the distance between the tip of the nose and the chin in the position of central occlusion; Gysi's method, which determined the height of the lower part of the face by the severity of the nasolabial folds.
All these methods are inaccurate and mostly overestimate the lower part of the face.
fnvdpvlnB methods. Haber proposed using rigid bases and determining the height of the central relationship of the jaws using a gnathodynamometer. Since muscles in the position of central occlusion develop the greatest muscle traction, Haber was guided by the highest readings of the gnathodynamometer. A small pin was fixed in front of the upper wax roller, and a metal plate with a recording table covered with a thin layer of wax was attached to the wax roller of the lower jaw. The pin should touch the surface of the table. The patient was asked to make lateral movements of the lower jaw until fatigue. An angle of approximately 120° is outlined on the table with a pin. The location of the pin at the apex of the angle will indicate the central relationship of the jaws.
There is an intraoral method for recording the central relationship of the jaws, developed by B. T. Chernykh and S. I. Khmelevsky (1973). The essence of the method is that recording plates are strengthened on rigid bases of the upper and lower jaws using wax. A pin is fixed on the upper metal plate, and the lower one is covered with a thin layer of wax. When performing various movements with the lower jaw, a clearly defined angle appears on the lower plate, covered with wax, in the area of the apex of which one should look for the central relationship of the jaws. Then a thin celluloid plate with indentations is placed on top of the bottom plate, aligning the indentation with the top of the corner, and it is filled with wax. The patient is again asked to close his mouth and, if the support pin gets into the recess of the plate, the bases are secured on the sides with plaster blocks, removed from the oral cavity and transferred to plaster models of the jaws.
♦ All of the listed methods for determining the central relationship of the jaws were not found wide application due to inaccuracy of definition or complexity of implementation. In everyday practice, the anatomical and physiological method is used.
Anatomical and physiological method. It is known from anatomy that with the correct shape of the face, the lips close freely, without tension; the nasolabial and chin folds are slightly pronounced, the corners of the mouth are slightly lowered.
The physiological basis of the method for determining the central relationship of the jaws is the position of the lower jaw in relative physiological rest and the fact that the occlusal height of the lower part of the face is 2-3 mm less than the height at physiological rest. Physiological rest is a free sagging of the lower jaw, in which the distance between the dentition is 2-3 mm, the masticatory muscles and the orbicularis oris muscle are slightly tense.
First, the models are examined, on which the boundaries of the future prosthesis, the incisive papilla, the palatine fossa, the palatine torus, the line of the middle of the alveolar process, the tubercles of the upper jaw, the midlines, and the mandibular mucous tubercle should be marked with a pencil. The midline and the midline of the alveolar process should be drawn onto the base of the model. The bases on which the occlusal ridges are strengthened are prepared from durable wax or plastic. Rigid bases are used for difficult anatomical conditions in the oral cavity.
The wax bases should tightly cover the model, their edges exactly correspond to the boundaries of the future prosthesis. It is necessary to ensure that the edges of the wax bases are not sharp, otherwise they are smoothed with a heated spatula.
Then, if necessary, begin to correct the occlusal wax ridge. On the upper jaw, the height of the cushion should be approximately 15 cm in the anterior area, and 5-7 mm in the area of the chewing teeth.
In the anterior section of the upper jaw, the ridge should protrude slightly forward and be 3-4 mm wide; in the lateral areas it protrudes from the top of the alveolar ridge by 5 mm and reaches 8-10 mm in width.
Thus, the occlusal ridge on the upper jaw must match the perimeter and shape of the future dental arch.
A wax base with an occlusal roller is inserted into the oral cavity and the position of the upper lip is determined - it should not be tense or sunken. The position of the lip is corrected by cutting or building up wax on the vestibular surface of the roller. Then determine its height in the front section: the edge of the roller should be at the level bottom edge upper lip or protrude from under it by 1.0-15 mm. It must be remembered that the length of the upper lip can vary depending on.
from this, the edge of the upper lip can protrude from under the lip by 2 mm, be at the level of it or above the edge of the upper lip by 2 mm (Fig. 200).
Having determined the level of the prosthetic plane, they begin to form it, first in the anterior section, and then in the lateral sections. To do this, a plane is created on the roller, parallel in the anterior section of the pupillary line, and in the lateral sections - to the nasal line: the wax is cut off or extended onto the plane of the roller made by the technician.
When forming a roller in the anterior area, they are guided by the pupillary line. The rulers - placed under the edge of the upper cushion and set along the line of the pupil - should be parallel (Fig. 201). If the rulers are not parallel, for example they diverge on the left side, then this indicates the following: I 1) the roller to the right of center line has a small vertical
size; 2) the roller to the left of the center line is large.
To establish which position is correct, remove the rulers, ask the patient to relax, and if the ridge on the right is above the level of the red border of the lip, then the area from the midline to the canine line is extended with a strip of wax. After this, the parallelism of the rulers is checked. If the ridge to the left of the center line protrudes from under the red border of the lip by more than 1-15 mm, then this area must be cut off.
Then they begin to create a prosthetic plane in the lateral areas. To do this, one ruler is installed under the upper roller, and the other - at the level of the lower edge of the nose wing and ear canal(Camper's line). These lines must also be parallel. If necessary, the wax is cut off or extended in the lateral sections. After the surfaces of the roller are parallel to the pupillary and nasal lines, it must be smoothed, making the created prosthetic plane very even. For this purpose, the Naisha apparatus is used.
In addition to rulers, the Larin apparatus can be used to form a prosthetic plane. It includes an intraoral occlusal plate and extraoral ones, which serve to establish them along the nasal lines. These plates have screw connections at the front and can be installed to any height and width.
Then the vertical size of the lower part of the face is determined when the lower jaw is in physiological rest. On the patient’s face, 2 points are marked with a pencil: one above, the other below the oral fissure. Most often, one point is placed on the tip of the nose, the other on the chin. The distance between the points is recorded on paper or on a wax plate. When determining this indicator, make sure that the patient’s head is correctly positioned and the muscles are relaxed. Sometimes.
They suggest making swallowing movements and after a while the height is recorded. When working with wax bases, you need to check their stability, and to prevent deformation, cool them in water from time to time.
The next stage is fitting the lower roller to the upper one. Usually, when the lower base is introduced into the oral cavity with the occlusal ridge, contact is noted only in the lateral areas, so in this area the roller is cut off with a spatula or the Naisha apparatus is used. The height of the lower roller must be adjusted in such a way that when the jaws are closed, the distance between the marked points is 2-3 mm less than in a state of physiological rest. Along the perimeter, the lower occlusal ridge should be identical to the upper one. One of the main points ensuring the success of the work is the uniform, plane contact of the rollers when they are closed. There are many ways to fix the rollers (brackets, fixation with a heated spatula, liquid plaster, etc.), but they are designed for experienced doctors.
Rice. 201. Facial landmarks for determining and forming the prosthetic plane, a - in the anterior section; b - in the area of chewing teeth.
Rice. 200. Position of the upper occlusal ridge in relation to the upper lip (diagram). 1 - above the lip; 2 - at lip level; 3 - below the lip.
The following method of fixing the central relationship of the jaws is recommended. On the upper ridge, in the area 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 ridge. The doctor places his index fingers in the area of the chewing teeth, inviting the patient to touch the back third with the tip of his tongue hard palate and in this position close your jaws. Heated wax enters the notches of the upper jaw, creating locks, and the heated plate of wax is squeezed out from under the rollers, as a result of which the lower part of the face does not rise. Then the occlusal ridges are removed from the mouth, cooled, excess crushed wax is cut off and the central relationship of the jaws is checked several times. At this stage, phonetic tests can be carried out. When pronouncing vowel sounds, the distance between the upper and lower occlusal ridges should be 2 mm, and when speaking - 5 mm.
The last step is to draw guide lines for the placement of the six upper teeth. Based on these lines, the technician selects the size of the teeth. On the upper roller it is necessary to apply the median line, the line of the fangs and the smile.
The midline is drawn vertically, as a continuation of the midline of the face, dividing the philtrum of the upper lip into equal parts. This line cannot be drawn along the frenulum of the upper lip, which is quite often shifted to the side. The midline is located between the central incisors. The line of fangs, passing along the tubercles of the latter, descends from the outer wing of the nose.
A horizontal line is drawn along the border of the red border of the upper lip when smiling and the vertical size of the tooth is determined. Artificial teeth are placed so that their necks are above the marked line (Fig. 202). With this arrangement of artificial teeth, their necks and artificial gums will not be visible when you smile.
If the patient has dentures, they are used for correct orientation when determining the height of the lower part of the face when the lower jaw is in physiological rest and the thickness of the vestibular edge.
In case of a large degree of atrophy of the alveolar processes of the upper and alveolar parts of the lower toothless jaws, poor fixation of wax bases with occlusal ridges, it is advisable to determine the central ratio of the jaws on rigid bases, which are much better fixed, do not deform, do not move on the jaws and on which in the future it is possible to placement of artificial teeth.
Functional-physiological method. The human body is a complex, constantly changing biology.
Rice. 202. Positioning of the anterior teeth in relation to anthropometric landmarks.
system, the regulation and development of which is carried out according to the principle feedback.
As the body ages, teeth are lost, and jaws atrophy, the functionality of the entire complex of muscle, bone and vascular tissues changes. Therefore, static methods, as well as methods that are not able to take into account and reflect in specific digital values those functional physiological features that are characteristic of the dentoalveolar system at a particular moment in orthopedic treatment, lead to a number of side effects and a decrease in the quality of orthopedic care.
It is known from the laws of mechanics that a muscle can develop maximum force only when the distance between the points of attachment and the area of the muscle fiber is optimal for performing the function. This function is under the control of the central nervous system, which carries out regulation according to the feedback principle, and this in turn entails a whole complex of interactions, manifested in blood supply, metabolism and the function of the entire dentofacial apparatus. Due to this orthopedic treatment at toothless jaws is one of the most serious and complex sections of orthopedic dentistry.
What could be a feedback signal that could be recorded during operation? dental system, one of the main functional properties of which is chewing food? Naturally, with an effort that the entire muscle complex is capable of developing. However, the feedback signal is generated not only from the muscles and areas where food is ground, but also from the mucous membrane, tongue and other areas of the oral cavity.
Registration of the feedback signal, expressed in the magnitude of forces that the muscular apparatus of the dentofacial system is capable of developing, is carried out when the muscular apparatus is in a balanced state and the position of the jaws is fixed. In this position, the muscles are able to develop maximum force, and the device itself used for this purpose makes it possible to simulate future loads on the mucous membrane and the prosthetic bed. Based on this approach, a special apparatus for determining the central occlusion of the AOCO with an intraoral device was developed, which makes it possible to determine the central relationship of the jaws, taking into account all the listed factors with an accuracy of ±0.5 mm.
The device has a device for recording signals coming from a special force sensor, which is placed on a support plate in the oral cavity. The results of muscle efforts can be recorded in kilograms or recorded using an orthogram recorder. The apparatus includes a set of support plates for jaws of different sizes, as well as support pins and force sensor simulators (Fig. 203).
Manufactured rigid individual base spoons are fitted in the mouth and, after shortening the edge by 1-2 mm and edging with orthocore, they are functionally designed. On the lower individual spoon, a support plate with a force sensor is strengthened parallel to the pupillary line, and on the upper one, a special metal support platform included in the device kit is attached.
The trays prepared in this way are inserted into the oral cavity and a support pin is installed on the force sensor, which corresponds to the distance between the jaws in a state of physiological rest. Given the ratio, the distance between the jaws is obviously too high. The force sensor is connected to the recording part of the AOTSO device with output to the recorder and the patient is asked to clench his jaw several times. At the same time, the force is recorded, which develops the entire complex of the muscular system, taking into account the compliance of the mucous membrane and other indicators, since the relationship of the jaws is simulated by a support pin. The latter not only limits the closure of the jaws, but also balances the entire system and transmits force to the prosthetic bed.
Having registered this force, the pin is replaced with a smaller size with an interval of 0.5 mm. The patient is again asked to clench his jaw as much as possible several times. By changing the size of the pin, the position when the muscles are able to develop maximum force is recorded. It should be noted that as soon as the distance between the jaws becomes less than required for optimal function, even by 0.5 mm, the level of force generated will immediately decrease. It is this vertical relationship of the jaws that is the starting point from which all other parameters of the central relationship are measured (Fig. 204).
Apply to the support plate of the upper base tray thin layer melted wax and, placing spoons on the jaws, offer the patient to clench his jaws and make several movements of the lower jaw forward and to the sides. In this case, the pin will leave a mark in the form of an arrowhead on the supporting platform of the upper jaw. The top of this figure will be the point at which the jaws will be in centric relation.
The next stage is determining the occlusal surface. This stage can be carried out as traditional methods, under the control of a support pin, and with the help of wax-carborundum rollers, which allow you to achieve maximum effect. After strengthening the rollers on trays with support platforms, a sensor simulator and a pin, they are inserted into the oral cavity, while the rollers are made such that the pin does not reach the upper support platform by 1.5-2.0 mm. The grinding in of the rollers is carried out under the strict control of the pin, in which it is impossible to reduce the bite, and the central relationship of the jaws can be easily controlled by the location of the pin in relation to the figure on the supporting platform of the upper jaw.
Using an intraoral device, it is also advisable to take functional impressions under pin pressure. This will make it possible to take into account not only the pliability of the mucous membrane, but also to simulate the load on it during the use of the prosthesis and reflect the features of the prosthetic bed that arise during the function in the cast, and, consequently, the model from which the prosthesis is made. The subsequent stages of making dentures are carried out in a conventional occluder or articulator, depending on the chosen method of teeth placement.
To set up artificial dentition on spherical surfaces, the central ratio of the jaws is determined using a device developed by A. L. Sapozhnikov and M. A. Napadov. The device consists of an extraoral face bow-ruler and an intraoral forming plate, the front part of which is flat and distal sections have a spherically curved surface (Fig. 205).
In the usual way, decorate the front part of the upper
occlusal roller and, using it as a stop area, form pre-softened lateral sections of the occlusal roller with the intraoral part of the device so that the extraoral part is installed parallel to the naso-auricular and pupillary lines. Then the lower wax roller is heated with a hot spatula and placed on the lower jaw. A pre-cooled upper roller and the intraoral part of the device are introduced into the mouth and the patient is asked to close his mouth, while ensuring that the height of the occlusal rollers and the intraoral part of the device located between them corresponds to the height of the lower part of the face when the lower jaw is in physiological rest.
After removing the device, which has a thickness of 15>-2.0 mm, the height of the central relationship of the jaws is obtained on the rollers formed on spherical surfaces. The correct formation of the ridges is checked by the presence of tight contact between them at various shifts of the lower jaw.
After fixing the rollers, the work is transferred to the dental laboratory.
