Outer surface of the lower jaw. Features of the lower jaw

The lower jaw is a mobile bone of the facial skeleton, consisting of a body, a branch, an angle.
The body consists of basal and alveolar parts.
The branch has two processes - condylar, ending with the head of the lower jaw, and coronal.
The ratio of the height of the branch to the length of the body of the jaw in an adult is 6.5-7:10. The angle of the lower jaw is normally 120 degrees ± 5 (Trezubov).

The shape of the dentition is parabolic.
The lower jaw is a horseshoe-shaped non-paired bone consisting of a body, two branches that end in two processes, coronal and articular, between the processes there is a semilunar notch.
The lower edge of the body and the posterior edge of the branch form an angle of 110-130°

Inner surface:

1. In the region of the central incisors, the chin spines;
2. Next to them is the digastric fossa, the place of attachment of the muscle of the same name;
3. Laterally (from the fossa) the bone roller is the internal oblique line (maxillary-hyoid);
4. In the area of ​​​​the angle on the inside, pterygoid tuberosity, the place of attachment of the muscle of the same name;
5. On the inner surface of the branch of the lower jaw there is a hole, the exit point of the neurovascular bundle.

Outside surface:

1. Chin protrusion, chin holes in the area of ​​the second premolars;
2. The external oblique line goes to the top and posteriorly, merging with the internal oblique line forming behind the retromolar space;
3. In the area of ​​the corner, masticatory tuberosity.

So, the lower jaw consists of a body, corpus mandibulae, formed by two horizontal branches and paired vertical branches , rami mandibulae connecting with the body at an obtuse angle. The body of the lower jaw bears a row of lower teeth.

The junction of the body and branches of the lower jaw forms the angle of the lower jaw angulus mandibulae, to which the masticatory muscle is attached from the outside, causing the appearance of the tuberosity of the same name, tuberositas masseterica. On the inner surface of the angle is pterygoid tuberosity , tuberositas pterigoidea, to which the internal pterygoid muscle is attached, m. pterigoideus medialis. In newborns and the elderly, this angle is approximately 140-150 degrees; in adults, the angle of the lower jaw is close to a right one. This is directly related to chewing activity.

Rice. Anatomy of the lower jaw (according to H. Milne, 1998): 1 - the body of the lower jaw; 2 - chin tubercle; 3 - chin spine; 4 - chin hole; 5 - alveolar part; 6 - branch of the lower jaw; 7 - angle of the lower jaw; 8 - condylar process; 9 - neck of the lower jaw; 10 - pterygoid fossa; 11 - coronoid process; 12 - notch of the lower jaw; 13 - opening of the lower jaw; 14 - tongue of the lower jaw.

The structure and relief of the body of the lower jaw are due to the presence of teeth and its participation in the formation of the mouth (M.G. Weight gain et al., 1974).

The outer surface of the body of the lower jaw is convex, protruding forward with a chin protrusion, protuberantia mentalis. The mental prominence is divided by the mental symphysis, symphysis mandibulae (mentalis), on the sides of which there are two chin tubercles, tubercula mentali. Above them and slightly lateral to the symphysis (at the level of the gap between the 1st and 2nd small molars) are the chin fossae, where the chin holes are located, foramen mentale, representing the outlets of the mandibular canals, canalis mandibulae. The third branches of the trigeminal nerve pass through them. external oblique line, line oblique, goes from the chin protrusion to the upper edge of the vertical branch. Alveolar arch , arcus alveolaris, goes along the upper edge of the body of the lower jaw and carries dental cells, alveoli dentales. In old age, the alveolar part often atrophies and the whole body becomes thin and low.

The inner surface of the body of the lower jaw is concave with a pronounced hyoid oblique line, linea mylohyoidea, running from front to back from the upper chin protrusions to the upper edge of the vertical branch. Above this line there is a hypoglossal fossa, fossa sublingualis where the sublingual gland is located. Under the line is the submandibular fossa, fossa submaxillaris, - the location of the submandibular gland.

In the region of the symphysis, two mental spines protrude on the inner surface, spina mentales, - places of tendon attachment mm. genioglossi. The tendinous way of attaching the muscles of the tongue contributed to the development of articulate speech. The mental spines are the places of attachment of the geniolingual, mm. genioglossi, and geniohyoid muscles, mm. geniohyoidei.

On the sides of spina mentalis, closer to the lower edge of the lower jaw there are places of attachment of the digastric muscle, fossae digastricae.

vertical branches, rami mandibulae, - flat bones with two protrusions: the condylar process, processus condylaris, and the coronoid process, processus coronoideus, separated by the mandibular notch, incisura mandibula.

On the inner surface there is a mandibular opening, foramen mandibulae, leading to the mandibular canal. The inner edge of the hole protrudes in the form of a tongue of the lower jaw , lingual mandibulae to which the sphenomandibular ligament is attached, lig. sphenomandibular. To pterygoid tuberosity, tuberositas pterygoidea, the internal pterygoid muscle is attached. At the junction of the body and vertical branches, gonion, there is an attachment of the stylomandibular ligament, lig.stylomandibulare.

At the top, as already mentioned, the branch ends with two processes: condylar and coronal. The coronoid process was formed under the influence of the traction of the temporal muscle. On the inner surface of the branch towards the coronoid process, from the level of the last molars, the comb of the buccal muscle rises Crista buccinatoria. The condylar process has a head, caput mandibulae, and the neck collum mandibulae. In front of the neck is a fossa, to which the external pterygoid muscle is attached. , m. pterigoideus lateralis.

A preliminary impression (PR) is a negative image of the tissues of the prosthetic bed with clinically significant anatomical landmarks, obtained using a standard tray and a set of functional tests (FP), providing maximum information to the dental technician for the manufacture of an individual tray (IL), requiring minimal correction to obtain an effective functional suction impression.

Obtaining primary information about the prosthetic bed for a dental technician is carried out only on the basis of preliminary impressions obtained by an orthopedist from edentulous jaws. Despite this, when analyzing the numerous literature on the topic of "complete removable prosthetics", it seems that the majority of authors do not pay due attention to the significant role of the stage of obtaining software for the manufacture of IL. A secondary attitude to this stage may initially lead, at best, to the complication of the already laborious and lengthy fitting of IL, at worst, to a mismatch of the boundaries of a complete removable denture (PRP). And if we take into account the fact that shortcomings and errors in obtaining PO can only be corrected in the rarest cases by means of final functional impressions (FP), we can make an unambiguous conclusion - obtaining PO is an obligatory and responsible stage in the rehabilitation of patients with complete absence of teeth (POZ) removable prostheses that require an appropriate implementation protocol and criteria for assessing its quality. When obtaining software, it is necessary to strive to obtain the most approximate correspondence between the boundaries of the impression and the future PSP, minus the thickness of the edging material (on average 2-4 mm, depending on the material used), as well as creating a minimum pressure on the underlying mucous membrane (CO) in order to exclude its deformation.

Before obtaining software for the manufacture of IL, it is necessary to carefully weigh the data of the patient's clinical examination, study the clinical anatomy of the edentulous jaws, the nature and degree of bone bed atrophy, have an idea of ​​the peripheral boundaries of the future PSP, the type of SM, its compliance and endurance to pressure and, as a result, , to predict the degree of compression effect of the impression mass (OM) during the period of receiving the PO.

Software requirements:

• PO is removed from healthy tissues of the prosthetic bed. If there are signs of chronic or acute inflammation of the mucous membrane, a week before the impressions, measures are taken to eliminate them (limiting the time of using old removable dentures, refusing adhesives that cause swelling of the mucous membrane, clinical relining, or using a tissue conditioner - Ufi Gel).
• SO receive OM, displaying the relief of the prosthetic bed, moderately pressing the surrounding soft tissues and not having excessive fluidity. For these purposes, alginate masses are optimally suited.
• The software overlaps or is at the level of those anatomical formations that are in contact with the basis of the future PSP. Failure to comply with this requirement will certainly lead to a significant discrepancy between the boundaries of the FI and future prostheses, and, consequently, to a decrease in their functional value.
• The software fixes not only the depth of the anatomical furrows, but also their width. In other words, the boundaries of the PO should be voluminous, as well as the edges of future prostheses.
• Using functional tests to design the outer edge of the software, the borders of the software are brought as close as possible to the neutral zone. As a result of the correct implementation of this stage, the ILs will require minimal correction, which will further facilitate their fitting and save time for the doctor and the patient.
• The contour of the future IL is marked on the software with an indelible marker, always in the presence of the patient (for the possibility of clarifying the boundaries). To facilitate this stage, you can display anatomical landmarks with an indelible pencil in the oral cavity, and when the impression is repeated, they will be imprinted on its surface.
• Use the stage of fitting the PO in the oral cavity with the creation of clear boundaries and the thickness of the edge of the impression of at least 3 mm before making the IL, which will significantly reduce its fit in the future and increase the functionality (patented author's technique).

The first and very important point in obtaining preliminary impressions is the stage of a clear visual representation of the boundaries of a complete removable denture in a particular patient. It is difficult to guarantee success in the prosthesis of patients with POI, based on the recommendations most often mentioned in the educational literature on the location of the boundaries of the PSP (“the borders of the PSP should pass along the “A” line, the transitional fold, overlapping the maxillary tuberosities (MT) and the mucous tubercles on the mandible (LF), while bypassing the frenulum and strands of soft tissues ... "). Effective prosthetics require specific anatomical landmarks that allow not only to accurately determine the preliminary boundaries of the FI with the subsequent functional design of its edges, but also to assess the boundaries of the finished PSP.

Functionally significant anatomical formations

The main guidelines in determining the boundaries of the PSP, which should be displayed on the software, include the following anatomical formations on the HF:

1. The frenulum of the upper lip in all cases does not overlap with the PSP. Therefore, the PO is released to the full length and thickness, especially at its base, not exceeding the size of the bridle itself.
2. The labial vestibule (potential labial vestibule space) is identified by gently pulling the upper lip down and slightly forward with the index finger and thumb. In this case, the resulting space must be completely filled with the volumetric edge of the PSP.
3. The bucco-alveolar cords are located at the level of the premolars or canines. Their movement should not be limited by the edge of the PSP, therefore they are displayed on the print as several grooves directed from front to back and from bottom to top.
4. The buccal vestibule with the base of the zygomatic process of the HF is the bone basis of the transitional fold (the neutral zone coincides with the transitional fold). An impression is easily formed in this area using a passive test - pulling the cheek to the side and down with the index and thumb of the doctor.
5. The vestibular spaces in the region of the maxillary tubercles (Einsenring's ampulla zone) are often narrow and have undercuts. Actively formed by bilateral lateral displacements of the bass.
6. The maxillary tubercles do not atrophy in case of loss of teeth and should be displayed in the software in full.
7. The pterygo-mandibular notches are determined using a dental mirror sliding along the distal slope of the HF tubercle. At the base of the hillock, the end edge of the mirror falls into a depression, which is this formation and partly the rear boundary of the PSP. The pterygo-mandibular notches are marked with an indelible marker, since they are not visible during a normal examination of the oral cavity.
8. Line "A" is easily determined during a nasal inflating test. The patient blows air through the nose with the nostrils pinched. At the same time, the soft palate descends almost vertically and the “A” line becomes clearly visible. More often, the PSP overlaps by 1-2 mm, but depending on the shape of the slope of the soft palate, the edge of the prosthesis can lengthen up to 5 mm with a flat shape or coincide with it with a steep one. In this case, the following pattern is observed: the higher the palatine vault, the more anteriorly the line "A" is located and the sharper its bend.
9. If, during a naso-inflating test, the patient has significantly compliant CO along the distal border, small folds may form on the tissues of the “A-zone”, as a result of which it will be impossible to determine a clear border of the “A” line. In such cases, the position of the A-line determined during the sound "A-test" (pronunciation of a short sound "A", but short sounds "AK" or "AH" are more effective) should be taken as a basis.
10. Blind pits are a good guideline for finding the rear border of the PSP and are more often overlapped by the PO. With significant compliance in the paratorus area, these formations can not overlap the PSP, but in order to improve the marginal closing valve, it is necessary to engrave on the working model along the posterior border.
11. Sagittal suture with bone elevation. With a pronounced torus, its borders should be accurately marked by a doctor on the software and isolated by a dental technician on the model before manufacturing the FI. These actions apply to exostoses.
12. The incisive papilla is more often isolated on the working model. Otherwise, compression of this formation is possible and, as a result, a subjective deterioration in taste sensitivity.
13. Transverse palatine folds must be isolated before the manufacture of IL.

Anatomical landmarks on the bass:

1. The frenulum of the lip, due to reduced tone, can be partially displaced by the edge of the PSP without any consequences.
2. The labial vestibule (potential labial vestibule space) is identified by gently pulling the lower lip up and forward with the index finger and thumb. In this case, the resulting potential space must be completely filled with the volumetric edge of the PSS.
3. The bucco-alveolar bands are not overlapped by the prosthesis and are displayed on the impression as several furrows directed from front to back and from top to bottom.
4. Mandibular or cheek pockets (Fisch's cavities). Their boundaries in front are the buccal-alveolar cords, behind - the retmolar spaces, laterally - the external oblique lines, medially - the external slopes of the alveolar process. These formations are completely covered by the basis of the prosthesis.
5. The alveolar process is completely covered with an impression, up to the transitional fold.
6. Retromolar mandibular spaces with mucoid tubercles, which, regardless of shape and compliance on the PO, should be displayed completely or distal to their two-thirds.
7. The mandibular pterygoid lines rarely coincide with the boundaries of the PSP, more often overlapping them, going into muscleless triangles with their edges.
8. Muscleless triangles are more likely to overlap PSP under unfavorable anatomical conditions. If a patient develops a sore throat or pain when swallowing (angina-like pains), it is necessary to first thin the edge of the PSP in this area, and if there is no effect, shorten it.
9. Internal oblique lines (maxillary-hyoid lines) are determined, like the tone of the muscles of the bottom of the mouth, only by palpation. Depending on the severity of muscle tone, the edge of the PSP overlaps these formations by 2-6 mm not vertically down, but gently, taking into account the functional state of the muscles of the floor of the mouth.
10. Language. With the correct design of the inner edge of the mandibular PSP, the tongue performs a stabilizing function (lingual inclination of artificial teeth is unacceptable, which contributes to dropping the PSP).
11. The frenulum of the tongue never overlaps the PSP. The basis of the prosthesis should not expand along the frenulum, otherwise the marginal closing valve is broken.
12. External oblique lines (oblique lines) are determined only by palpation, for the purpose of visualization they are immediately marked with an indelible marker and overlapped by the edge of the prosthesis by 2 mm in order to form a marginal closing valve with a low-toned buccal muscle.
13. The geniohyoid eminence always overlaps. Otherwise, the closing valve will not be possible.
14. The sublingual papillae, located on either side of the frenulum of the tongue, must not overlap with the PSP, otherwise they may become blocked and interfere with salivation. The patient feels dryness in the mouth, the salivary gland swells, and there is an unpleasant feeling of tension.
15. The sublingual ridges that limit the lingual edge of the mandibular PSP are clear guidelines for its boundaries in this area.

Protocol of actions upon receipt of software

After a thorough examination, the patient is seated in a chair in an upright position. The doctor measures using a dental compass, included in the set with standard spoons (SL) for edentulous jaws, the largest buccal bulge on the tubercles of the HF and between the internal oblique lines in the region of the first molars on the lower.

Selects the appropriate spoon according to the template included in the set and tries it on in the mouth. For this, the patient is asked to open the mouth halfway and the spoon is inserted into the mouth in a horizontal direction using the handle. On the HF, first, the back edge of the spoon is placed in the pterygomaxillary recesses, and then installed in the anterior section, aligning the frenulum of the lip with the middle of the spoon (in this case, the alveolar process should be in the center of the alveolar groove of the spoon). The handle of the impression tray is the central guideline for impression tray application, with the middle of the handle aligned with the midline of the face to ensure proper positioning. The use of SL for highly accurate impressions has shown that only due to the optimal selection it is possible to save up to 30-40% of the impression material.

Creation of positioners on a standard impression tray

In restless patients, during the curing of the alginate impression (AO), undesirable displacements of the SL, a sharp squeezing of the mobile SM, especially the labial or buccal frenulum, may occur, which will inevitably affect the quality of the PR.

To prevent this moment and create a uniform gap between the SL and the tissues of the prosthetic bed with a width of 3-5 mm, you can use the method of creating silicone limiters on the inner surface of the spoon, which exclude its lateral displacement (guiding function) and, with too long and too much pressure, prevent elastic shape change BY .

After the re-introduction of the SL with limiters, it is easy to assess the relationship of its edge to the anatomical landmarks and, if they are short, to carry out individual completion (individualization of the SL edges). At the same time, we must adhere to the rule: "the edges of the PSP should not end on the hard tissues of the prosthetic bed due to the impossibility of obtaining a marginal closing valve."

Individualization in the area of ​​the hard palate is required if there is a significant discrepancy in this area between the SL and the roof of the palate (more than 5 mm). The material located in the area of ​​the hard palate of the SL not only individualizes, but also performs a guiding and restrictive role when it is applied during the preparation of a preliminary impression.
With severe atrophy of the jaws, it is often recommended to use silicone and polyvinylsiloxane masses with varying degrees of viscosity in order to obtain PO in order to push back the mobile soft tissues, the sublingual glands, located close to the top of the alveolar part. In this case, due to the increased viscosity, a thickening of the PO edges and deformation of the transitional fold inevitably occur, which makes it difficult to determine the real boundaries of the IL. Considering the above disadvantages and the high cost of these materials, alginate materials can be used as RM for PO even under unfavorable conditions, but with the obligatory individualization of the SL edges regulated by the doctor. Due to the wide variety of atomic features of edentulous jaws, the high plasticity of alginate materials, and the risk of shortening or expanding the boundaries of SL PO along the periphery, it can be clinically designed with base wax, thermoplastic or high-viscosity silicone masses. To do this, a softened and folded in half strip of base wax is placed along the edge of the SL, glued with a hot spatula and, inserting a spoon into the oral cavity, compress the wax along the slope of the alveolar processes. The areas of wax that have entered the actively mobile CO are cut off.

Most often, at HF, individualization of the SL is required in the region of the labial space, tubercles and the entire posterior border (to immerse the edge in the pterygomandibular notches and overlap the “A” line). At the LF, the completed edges of the SL should overlap the mucous tubercles, internal and external oblique lines, and, if necessary, go into the region of the muscleless triangle.

In rare cases, you can use edging around the entire perimeter of the trunk. By edging along the posterior border of the maxillary SL, we thereby not only lengthen its borders, but also prevent the impression mass from flowing far into the soft palate. To do this, the wax strip expands towards the soft palate by 10-15 mm, while the palatine curtain moves back and up, which contributes to its display on the software in an elevated position. Individualization in the area of ​​the hard palate is required if there is a significant discrepancy in this area between the SL and the roof of the palate (more than 5 mm). At the same time, the material located in the region of the hard palate of the SL not only individualizes, but also performs a guiding and restrictive role when it is applied during the acquisition of PO. Before adding alginate to the SL, it is recommended for the doctor and the patient to practice setting the spoon in the desired position (especially on the LF) with imitation of functional tests and to teach the patient to breathe correctly while receiving the PO. In this case, the severity of the gag reflex can be assessed.

Before receiving PO, it is recommended to rinse the mouth well using weak antiseptic solutions or special liquids. They effectively eliminate mucus and food residues, have a moderately pronounced tanning effect of CO, and have disinfectant properties. You can free the CO surface from thick saliva and mucus using a sterile gauze wound around your index finger.

An analysis of the works that substantiate and consider the effectiveness of the use of compression, unloading and differentiated methods for obtaining FO in various clinical conditions of the tissues of the prosthetic bed indicates that many authors underestimate the moment of compression and deformation of the SM when obtaining FO for the manufacture of IL (Abdurakhmanov A.I., 1982).

Underestimation of the properties of RMs for obtaining PO leads to the fact that the manufactured ILs fix the deformation of the tissues of the prosthetic bed and the subsequent use of silicone OMs, as if providing differential compression of the CO, causes the same degree of compression and deformation of the tissues, which was established when obtaining the PO.

To achieve these goals, alginate materials are most suitable, since silicone materials produce 47% CO compression, and alginate masses - by 27%. As a result of the use of alginates, it is possible to avoid FI fixation of the deformed state of the tissues of the prosthetic bed, to obtain an accurate reflection of the SO relief, achieving a fairly accurate ratio of the FI edge to the transitional fold.

Before receiving PO, it is recommended to rinse the mouth well using weak antiseptic solutions or special liquids. They effectively eliminate mucus and food residues, have a moderately pronounced tanning effect of CO, and have disinfectant properties.
Given that alginate turns into a gel in about 40-50 seconds (A.P. Voronov, A.I. Abdurakhmanov, 1981, A.I. Doinikov, 1986), and functional tests are lengthy, novice doctors are advised to use cold water to delay the setting of OM. To obtain the correct OM consistency, only the water and powder dosing containers supplied by the manufacturer should be used. The powder should not be poured with a slide. Kneading the material by eye leads to the wrong consistency of the mass.

For good adhesion of the RM to the surface of the SL, its edges must first be treated with adhesive sprays or a special glue-adhesive. It is especially important to fulfill this condition when using edging materials in order to individualize the edges of the SL. Mixing of the alginate mass must be carried out intensively during the time specified by the manufacturer until a homogeneous paste-like mass is obtained. The finished material must be sufficiently viscous so that it can be applied with a slide to the SL. The index finger wetted in the input is given a smooth surface and a mass is formed in the form of an alveolar ridge. The creation of an aqueous film relieves the surface tension of the print.

Insertion of a standard impression tray into the oral cavity and functional formation of the PO edges

Using a spatula or index finger, a small amount of alginate can be placed in the distal buccal vestibule and in the deepest region of the roof of the palate at the HF and in the sublingual region at the LF to fully display the anatomy and prevent the formation of air pores. This should always be done when the clinician ignores the individualization of SL.

A spoon with OM is introduced into the oral cavity in a circular motion, while the left corner of the mouth is retracted with the index finger (preferably a mirror), and the right corner is moved away by the side of the SL. In this case, the following actions are performed: centering the tray with OM, its immersion on the prosthetic bed, fixation and stabilization. With the help of oscillatory movements, the OM on the HF should first of all fill the labial and buccal grooves, after which the palatal region of the SL is pressed. The upper lip should be raised with the index and middle fingers so that a sufficient amount of alginate enters the labial vestibule. Holding a spoon with one hand, the doctor can check the fullness of the bucco-labial furrows with the other hand. Translational pressure on the spoon stops when the alginate is visible along its entire back border. Thanks to prefabricated limiters, you can not be afraid of excessive immersion of the SL, even with significant finger pressure on it.

Complex of functional tests for maxillary software:

• After complete positioning of the SL with OM on the prosthetic bed, the doctor exerts finger pressure on it, perpendicular to its crest in the projection of teeth 16 and 26 or in the area of ​​the hard palate.
• Pulls the cheeks with the index and thumb fingers to the side and down, thereby forming the buccal vestibule and eliminating the pinching of CO.
• The upper lip is gently pulled forward with two fingers to release the frenulum of the upper lip.
• The patient draws his cheeks inward, makes LF movements to the sides in order to shape the foreign space, taking into account the dynamics of the coronoid processes.
• The patient sets the lips with a tube and takes the corners of the mouth back, forming the area of ​​the buccal-alveolar bands.
• In addition, the patient is asked to open his mouth wide, fixing the influence of the pterygoid folds on the distal edge of the PO.
• After carrying out the above tests, the SL is kept at rest until the alginate has completely reached a dense state. The pressure on the spoon or its edging will cause stress in the layer where the hardening has begun, which will cause the PO to be distorted. The use of silicone stops eliminates this complication.

Important clinical points:

• In the region of the frenulum of the upper lip, passive tests should be minimal.
• The lip should be pulled slightly forward and slightly down.
• Lateral movements of the lip are excluded as non-physiological, leading to expansion of the space around the frenulum of the upper lip.
• In the buccal region, passive tests should be quite intense, with the maximum pulling of the cheek to the side and down.
• A wide opening of the mouth and lateral movements of the mandible are essential.

Complex of functional tests for mandibular software:

• To display the frenulum of the tongue in dynamics, we ask the patient to slightly lift and stick out the tongue forward.
• Slight lateral movements of the tongue to the sides to advance the impression material into the retromolar region and remove excess alginate from the sublingual region.
• Pull the cheeks with the index and thumb fingers to the side and up, bringing the borders of the impression closer to the outer oblique lines and excluding pinching of the cheeks.
• Pull the lower lip slightly up and forward at an angle of 45 degrees with the help of fingers, thereby making out the potential space of the labial vestibule.
• The doctor exerts significant finger pressure on the spoon, perpendicular to its crest in the projection of teeth 46 and 36, as a result of which the anterior bundles of the masticatory muscles proper, which are woven into the buccal muscles, reflexively contract, while the distal-lateral edges of the PO are formed in the form of notches. This test cannot be performed without silicone stops.
• Holding the tongue with a finger, we ask the patient to make several swallowing movements to functionally display the tissues of the floor of the oral cavity located below the internal oblique line.
• The patient draws his cheeks inward, makes LF movements to the sides.
• Sets the lips with a tube and takes the corners of the mouth back, forming the area of ​​the buccal-alveolar bands.
• In conclusion, the tip of the tongue rests against the place of attachment of the handle to the SL until the impression material is completely cured, thereby forming the edge of the PO in the area of ​​the sublingual ridges (Lauricen's test).
• Tests such as touching the tip of the tongue to the cheeks with a half-closed mouth and licking the upper lip often lead to a shortening of the lingual borders of the prosthesis and, as a result, to poor fixation of the prosthesis.

When receiving PO with LF, it is necessary that the mouth be covered as much as possible, because in the open state the boundaries of the PO can be distorted by tense muscles.

When using perforated trays, it is important that when the tray is removed from the mouth, there is no separation of the material from the tray, since repositioning the impression back will be difficult and may lead to its deformation.

The best way to remove the impression from the mouth is to press the excess material in the lateral zones of the vestibule of the mouth or, before removing the tray from the oral cavity, press the PO firmly against the jaw for 2-3 seconds. During this short time, the gap between the PO and the jaw is deformed, the capillary effect disappears, and the SL with the impression can be removed without resistance. An attempt to pull the PO by the handle can lead to the separation of the mass from the SL.

After removing the software from the oral cavity, pay attention to the following points:

• Adhesion of the impression material to the SL. When separating the OM from the spoon, the PO must be re-shot.
• Correspondence of software boundaries and future memory bandwidth. With a significant shortening of its peripheral boundaries, the impression must be made again.
• The presence of porosity in the print. If there are large or multiple pores, the software is retaken.
• The edges of the PO should be smooth, rounded, but not thick. The latter indicate stretching of the soft tissues, which does not correspond to their anatomical shape and indicates the expansion of the boundaries of the relatively immobile SM of the oral cavity.
• Lack of blurring of the relief of the prosthetic bed.

Borders of individual spoons

For the maximum transfer of information to the dental technician on the software, the boundaries of the FI are marked with a marker, always in the presence of the patient for their possible clarification. To facilitate this stage, anatomical landmarks can be marked with an indelible pencil in the oral cavity, and when the software is reapplied to the prosthetic bed, they will be displayed on its surface. Due to the fact that the alginate mass has a viscous consistency, the boundaries of the impression in any case are extended. Therefore, when applying the borders of the IL, it is recommended to retreat from the edge of the print by 4-5 mm. It is possible to note on the impression areas with low compliant CO, buffer zones identified with the help of a spherical float, and “dangling ridges”.

For several years now, the author has been using the following IL guidelines. On the upper jaw, the IL overlaps the maxillary tubercles, passes along the buccal vestibule just below the neutral zone, while widely bypassing the bucco-alveolar bands. In the region of the labial vestibule, the IL boundary is 2 mm less than the depth of its potential space and, bending around the frenulum of the lip in the form of a narrow slit, passes to the opposite side. The posterior border is a line connecting the pterygomandibular notches, located 2 mm distally from the “A” line.

It is possible to mark anatomical landmarks with an indelible pencil in the oral cavity, and when the software is reapplied to the prosthetic bed, they will be displayed on its surface
On the LF in the region of the labial vestibule, the edge of the IL is shorter by 2 mm of the depth of its potential space. In the buccal vestibule, widely bending around the buccal bands, the border passes along the external oblique line, then along the lateral surface of the retromolar region, bending around the bundle of the chewing muscle proper in a tense state, then horizontally crosses the mucous tubercle at the level of its 2/3 and sharply falls vertically downward or distally at an angle of 45 degrees to the internal oblique line, heading medially along it.

Located in front of the hyoid ridge and bypassing the frenulum of the tongue and the mental torus, the IL border continues to the other side of the LF. Depending on the tone of the muscles of the floor of the mouth, the internal oblique lines overlap with IL by 2-6 mm (the lower the muscle tone, the greater the overlap). The excretory ducts of the salivary glands always remain open.

The shortening of the edges of the IL relative to the boundaries of the PSP should be carried out by the thickness of the edging material used (for A-silicones, this is 2-3 mm).

In order to correct the edges of the PO in the oral cavity, taking into account the functional state of the soft tissues (in length and thickness) and to bring them as close as possible to the boundaries of the FI, we can recommend the author's method of fitting the PO (invention patent No. 2308905), which has been used by the author since 2005. This stage reveals, eliminates and prevents errors made when receiving software, which significantly reduces the stage of fitting FI and improves the quality of FI.

Author's software fitting technique

After drawing the borders of the FI with a marker on the PO (Fig. 1), the doctor, using a scalpel placed perpendicular to the surface of the alveolar ridge, cuts off the edge of the PO along the marked line (Fig. 2). After that, the PO can be introduced into the oral cavity to clarify its boundaries relative to the anatomical landmarks of the oral cavity, taking into account their functional state (the edges of the fitted PO should be close to the boundaries of the future IL). If necessary, the edges of the PO can be repeatedly corrected by cutting with a scalpel. For the convenience of performing the stage of fitting the PO in the oral cavity, you can use a scalpel to make the edge thickness of the PO 3-4 mm along the entire perimeter (Fig. 3).

Rice. 1. Schematic section of the maxillary PO in the projection of the molars (green indicates the limiter on the palatal surface of the SL). Rice. 2. Schematic representation of the shortening of the edges of the PO along the boundaries of the IL. Rice. 3. Schematic representation of the shortening of the edges of the PO in thickness (3-4 mm).

After that, on the cast plaster model in the area of ​​the base of the alveolar ridge, a platform is obtained that is perpendicular to the surface of the vestibular slope along its entire perimeter (Fig. 4-6).

Rice. 4. Schematic representation of a section of a plaster model with a given thickness along the edge and fitted software. Rice. Fig. 6. Photo of a plaster model obtained using the supplied software, with the boundaries set by the doctor for the manufacture of IL.

This platform is a specific limiter for the length of the edge of the future IL and its thickness (3-4 mm), which is a necessary condition for obtaining a volumetric edge of the FI. Displaying areas with significant compliance (buffer zone area according to E.I. Gavrilov) and thinned SO (torus, exostoses) on the FA with the help of a marker will give the dental technician the opportunity to make IL for a differentiated FO. The boundaries of the buffer zones are easily defined using a spherical trowel.

With the functional design of software, it should be remembered that the time spent is proportional to the quality of the FD, and hence the degree of fixation of the PSP, and inversely proportional to the time spent on fitting and edging the FI
In order to prevent the spread of nosocomial infection, the software is first disinfected by rinsing them with a stream of running water for 1 minute. This simple manipulation reduces microbial contamination of the impression by approximately 50%. Then the software is immersed in a glass dish with a disinfectant solution. Disinfection is carried out with the lid closed when the software is completely immersed in the solution. In this case, the level of the solution above the impression should be at least 1 cm. After the end of the procedure, the software is removed from the solution and washed with a stream of water for 0.5-1 minute to remove disinfectant residues. And only after that the software is transferred to the dental laboratory. Ideally, alginate impressions should be cast with plaster within the first 30 minutes of being taken. If they are cast in a remote dental laboratory, they should be transported in a plastic bag along with a piece of damp cloth to avoid drying out. At the same time, the fabric should not touch the alginate, so that local swelling of the material does not occur. Before casting the working model, you can sprinkle the inner surface of the PO with gypsum powder, after 1-2 minutes thoroughly rinse the impression under running water and remove the remaining powder with a soft brush. This will clear the PO of mucus residue and bind the free chains of alginic acids.

The most common mistakes when getting software:

1. Shortened borders of the PO and, as a result, not always resolvable difficulties during the fitting of IL in the oral cavity. Reasons: incorrectly selected SL (short edges), lack of individualization of its edges, unreasonably wide use of passive samples in the functional design of software, high viscosity of OM.
2. Excessively long PO boundaries lead to an increase in the doctor's time spent at the stage of fitting the IL. Causes: improperly selected SL (long edges), high viscosity of OM, low intensity of active functional tests, lack of silicone limiters.
3. One-sided shift of the software distorts the true boundaries of the FI. Reason: not using limiters/positioners.
4. Significant compression of the tissues of the prosthetic bed of the OM may prevent further obtaining a functional differentiated impression. Reason: use of high viscosity OM.
5. The presence of significant pores along the edges of the software and on its inner surface. Reason: incorrect imprinting on the prosthetic bed, the use of a high-viscosity OM.
6. Transmission of SL through OM. Causes: small SL, lack of silicone stops and excessive finger pressure on the spoon.
7. Thin, dangling edges along the edge of the PO are easily deformed during the casting of a plaster model, subsequently distorting the dimensions and boundaries of the FI. Causes: incorrectly selected SL (short edges), lack of individualization of its edges, fluid or incorrectly mixed OM.
8. Software deformation (not visualized). Reasons: significantly delayed receipt of the plaster model, use of the long-term immersion method for disinfection of software.
9. "Smeared layer" of plaster on the working surface of the model. Causes: poorly cleaned of mucus and alginic acid surfaces of the tissues of the prosthetic bed and PO.

Conclusion

In the functional design of software, it should be remembered that the time spent is proportional to the quality of the FD, and hence the degree of fixation of the PSP, and inversely proportional to the time spent on fitting and edging the IL. With a hasty and careless attitude to the stage of obtaining PO, it is difficult to count on the correct formation of the edges of the FD and obtaining the functional suction of the PSP. Errors at this initial stage of prosthetics can become a serious obstacle in the future to achieve a good end result. Remember that the strength of an entire chain is determined by its weakest link.

Literature

1. Lebedenko I. Yu., Voronov A. P., Lugansky V. A. Method for obtaining preliminary impressions from edentulous jaws using the author's technique. - M., 2010. - 54 p.
2. Boucher S. Prosthodontic Treatment for Edentulous Patients/ S. Boucher, G. A. Zarb, C. L. Bolender, G. E. Carlsson. - Mosby, 1997. - 558 p.
3. Hayakawa I. Principles and Practices of Complete Dentures/ I. Hayakawa. - Tokyo, 2001. - 255 p.

TOPOGRAPHANATOMICAL.

FEATURES OF TOOTHLESS JAWS.

The causes that cause complete loss of teeth are most often caries and its complications, periodontitis, trauma and other diseases; very rare primary (congenital) adentia. Complete absence of teeth at the age of 40-49 years is observed in 1% of cases, at the age of 50-59 years - in 5.5% and in people older than 60 years - in 25% of cases.

With a complete loss of teeth due to the lack of pressure on the underlying tissues, functional disorders are aggravated and ♦ atrophy of the facial skeleton and the soft tissues covering it rapidly increases. Therefore, prosthetics of edentulous jaws is a method of restorative treatment, leading to a delay in further atrophy.

With the complete loss of teeth, the body and branches of the jaws become thinner, and the angle of the lower jaw becomes more blunt, the tip of the nose drops, the nasolabial folds are pronounced, the corners of the mouth and even the outer edge of the eyelid drop. The lower third of the face is reduced in size. Muscle flabbiness appears and the face acquires an senile expression. In connection with the patterns of atrophy of bone tissue, to a greater extent from the vestibular surface on the upper and from the lingual - on the lower jaw, the so-called senile progeny is formed (Fig. 188).

With complete loss of teeth, the function of the masticatory muscles changes. As a result of a decrease in the load, the muscles decrease in volume, become flabby, and atrophy. There is a significant decrease in their bioelectric activity, while the phase of bioelectric rest in time prevails over the period of activity.

Changes are also taking place in the TMJ. The articular fossa becomes flatter, the head moves backwards and upwards.

The complexity of orthopedic treatment lies in the fact that under these conditions, atrophic processes inevitably occur, as a result of which the landmarks that determine the height and shape of the lower face are lost.

Prosthetics in the complete absence of teeth, especially on

Rice. 188. View of a person with a complete absence of teeth, a - before prosthetics; b - after prosthetics.

mandible is one of the most difficult problems in orthopedic dentistry.

When prosthetics for patients with edentulous jaws, three main questions are solved:

How to strengthen prostheses on edentulous jaws?.

How to determine the necessary, strictly individual size and shape of prostheses so that they best restore the appearance of the face?

How to design dentitions in prostheses so that they function synchronously with other organs of the masticatory apparatus involved in food processing, speech formation and respiration?

To solve these problems, it is necessary to know well the topographic structure of the edentulous jaws and mucous membrane.

In the upper jaw, during examination, first of all, attention is paid to the severity of the frenulum of the upper lip, which can be located from the top of the alveolar process in the form of a thin and narrow formation or in the form of a powerful strand up to 7 mm wide.

On the lateral surface of the upper jaw there are cheek folds - one or more.

Behind the tubercle of the upper jaw there is a pterygomandibular fold, which is well expressed with a strong opening of the mouth.

If the listed anatomical formations are not taken into account when taking impressions, then when using removable dentures in these areas there will be bedsores or the prosthesis will be dropped.

The boundary between the hard and soft palate is called line A. It can be in the form of a zone from 1 to 6 mm wide. The configuration of line A is also different depending on the configuration of the bone base of the hard palate. The line can be located up to 2 cm in front of the maxillary tubercles, at the level of the tubercles, or up to 2 cm go towards the pharynx, as shown in Fig. 189. In the clinic of orthopedic dentistry, blind holes serve as a guideline for the length of the posterior edge of the upper prosthesis. The rear edge of the upper prosthesis should overlap them by 1-2 mm. At the top of the alveolar process, along the midline, there is often a well-defined incisive papilla, and in the anterior third of the hard palate there are transverse folds. These anatomical formations must be well displayed on the impression, otherwise they will be infringed under the rigid base of the prosthesis and cause pain.

The seam of the hard palate in case of significant atrophy of the upper jaw is pronounced, and in the manufacture of prostheses it is usually isolated.

The mucous membrane covering the upper jaw is motionless, different compliance is noted in different areas. There are devices of various authors (A P. Voronov, M. A. Solomonov, L. L. Soloveychik, E. O. Kopyt), with the help of which the degree of mucosal compliance is determined (Fig. 190). The mucosa in the region of the palatine suture has the least compliance - 0.1 mm, and the greatest - in the posterior third of the palate - up to 4 mm. If this is not taken into account in the manufacture of laminar prostheses, then prostheses can balance, break or, by exerting increased pressure, lead to pressure sores or increased atrophy of the bone base in these areas. In practice, it is not necessary to use these devices; you can use a finger test or a tweezers handle to determine whether the mucous membrane is sufficiently pliable.

In the lower jaw, the prosthetic bed is much smaller than in the upper. A tongue with loss of teeth changes its shape and takes the place of missing teeth. With significant atrophy of the lower jaw, the sublingual glands can be located at the top of the alveolar part.

When making a prosthesis for the lower edentulous jaw, it is also necessary to pay attention to the severity of the frenulum of the lower lip, tongue, lateral vestibular folds and ensure that these formations are well and clearly displayed on the cast.

Rice. 190. Voronov's apparatus for determining the compliance of the mucous membrane.

there is a so-called retromolar tubercle. It can be hard and fibrous or soft and pliable and must always be covered with a prosthesis, but the edge of the prosthesis should never be placed on this anatomical formation.

The retroalveolar region is located on the inner side of the angle of the lower jaw. Behind, it is limited by the anterior palatine arch, from below - by the bottom of the oral cavity, from the inside - by the root of the tongue; its outer border is the inner angle of the lower jaw.

This area must also be used in the manufacture of laminar prostheses. To determine the possibility of creating a "wing" of the prosthesis in this area, there is a finger test. The index finger is inserted into the retroalveolar region and the patient is asked to extend the tongue and touch the cheek with it from the opposite side. If, with such a movement of the tongue, the finger remains in place and is not pushed out, then the edge of the prosthesis must be brought to the distal border of this zone. If the finger is pushed out, then the creation of a “wing” will not lead to success: such a prosthesis will be pushed out by the root of the tongue.

Outer surface of the lower jaw differs in the following anatomical features: the chin protrusion (protuberantia mentalis) is located in the symphysis area - at the place of fusion of the two halves of the lower jaw. Fusion occurs, as mentioned above, in the first year of the extrauterine life of the child. In the future, this part of the chin fuses with the chin bones (ossicula mentalia I-4 bones according to Meckel). These bones also take part in the formation of the chin protrusion.

chin protrusion on the side it is limited by the mental foramen (foramen mentale), which serves as the exit point for the mental nerves and vessels and is located between the first and second premolars. An external oblique line stretches upward and backward from the opening, located on the border between the body of the lower jaw and the alveolar process. On the outer surface of the angle of the lower jaw there is a roughness formed as a result of the traction of the masticatory muscle attached in this place, the so-called masticatory tuberosity (tuberositas masseterica). The external oblique line, as well as the internal one, serves to strengthen the lower molars and protect them from loosening in the buccal-lingual direction during transverse chewing movements (A. Ya. Katz).

Between articular head and coronoid process there is a mandibular notch formed as a result of phylogenetic development (incisura mandibulae). Some authors consider one of the reasons for its formation to be the thrust of the muscles attached here. The external pterygoid muscle pulls the articular head inwards and somewhat upwards, and the horizontal bundles of the temporal muscle pull the coronoid process backwards and upwards. Such a direction of traction of the musculature caused the formation of a semilunar notch as a result of species development.

Interesting in a nutshell dwell on the phylogeny of the chin protrusion (protuberantia mentalis). Chin formation is explained differently by different authors.
Some attribute the emergence chin action of the pterygoid muscles. The external and internal pterygoid muscles, acting on both sides in opposite directions, create an area of ​​​​a dangerous section in the zone of the chin protrusion and stimulate the bone tissue in the chin region to grow and thicken, which protects the lower jaw from fracture. This theory is one-sided.

Others explain chin formation the emergence of articulate speech and rich facial expressions that distinguish modern man from his ancestors. Various emotional experiences, which are reflected on the face and require continuous and specialized mobility of facial muscles, cause increased functional irritation of the bone tissue and, as a result, the formation of a chin protrusion. This idea is confirmed by the fact that all modern people have a pronounced chin, while primitive people, who stood at a low rung of the phylogenetic ladder, had no chin.

Still others explain chin formation reduction of the alveolar process due to the reverse development of the lower dentition, the basal arch of the lower jaw therefore protrudes.

In our opinion, chin development is determined not by one cause, but by many factors depending on the relationship between form and function and the ability of a living organism to adapt to environmental conditions. These are the main features that distinguish the relief of the lower jaw as a place of attachment of the masticatory muscles. Under the influence of increased functional activity of the lower jaw, not only the relief changes, but also the internal structure of this bone. It is known that the beams of spongy matter and their direction are always in a natural connection with the development of thrust and pressure. Pressure and traction in any bone causes special compression and rupture curves to occur. These lines of thrust and pressure are called trajectories.

Trajectories detected also in the study of the architecture of the lower jaw. Walkhoff, studying the functional structure of the lower jaw, examined the structure of the bone using an x-ray and found that the trajectories go from the place of loading through the area of ​​application of the force of the masticatory muscles and go to the articular heads. It distinguishes 8 directions of trajectories.

A. Ya. Katz also studied spongy substances of the lower jaw. He made cuts of the jaw in three mutually perpendicular planes. Research by A. Ya. Katz showed that the direction of the beams of the spongy substance reflects the functional activity of the lower jaw. The spongy substance of the retromolar region and branches is characterized by a lamellar structure.

Video lesson of the normal anatomy of the lower jaw

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