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Control questions to determine of the initial level of knowledge (α = 2).
1. What features in the embryogenesis of the upper and lower jaws do you know?
2. What features in the embryogenesis of the articular process do you know?
3. When does the facial part begin to form? What does facial part develop from?
4. Name the embryonic structures taking part in face formation
5. Describe the process of the embryogenesis during the 4th week of intrauterine development
6. Describe the process of the embryogenesis during the 6th -7th week of intrauterine development
7. Name the peculiarities of lower jaw development during intrauterine development. What violations of the development and growth of lower jaw can be?
8. Describe the embryogenesis of the teeth
9. Into what groups may all prophylactic methods be devided?
10. What issues should be done by doctor in the medicogenetic room to prevent dentognathic pathology?
11. What factors threaten the normal development of the dentognathic apparatus in the period of pregnancy?
12. Characterize the Pfaundler-Liushke’s fold cushions. What is its function?
13. Characterize the Roben-Mazhito’s fold cushions. What is its function?
14. Characterize fatty balls of Bichat? What is its function?
15. Where does 4-5 pairs of cross folds localize? What is its function?
16. Peculiarities of the infant’s tongue. What is it function?
17. Why the infant can breathe, suck and swallow simultaneously?
18. Characterize peculiarities of the infant’s TMJ and lower jaw position that allow him to suck?
19. Characterize the peculiarities of the infant’s upper jaw?
20. Characterize the peculiarities of the infant’s lower jaw?
21. Characterize the peculiarities of growth of upper jaw?
The educational material.
There are a number of common and distinguishing features in the embryogenesis of the upper and lower jaws. Both jaws develop from the first branchial arch, refer to membrane bones, and in the process of ontogenetic development undergo only two stages — membranous and osseous.
The articular process of the lower jaw is an exception as it develops from cartilage and performs approximately the same function as the cortical bones epiphyses in their longitudinal growth
From the 2nd week of pregnancy the facial part of the head begins to form (Table 1). After tissues differentiation the brain part structures, and then the facial part structures form in the head region of the embryo. The facial part develops from seven so-called processes: 1 frontal, 2 nasal, 2 maxillary, and 2 mandibular.
| Prominence | Parts of face forming from them |
| Frontonasal | Forehead, bridge of nose, medial and lateral nasal processes |
| Medial nasal | Central part of upper lip, dorsum and tip of nose, nasal septum, incisial bone |
| Lateral nasal | Wings of nose |
| Maxillary | Cheeks, lateral parts of upper lip, upper jaw, hard and soft palate soft palate |
| Mandibulary | Lower lip, lower jaw |
During the 4lh week the septum, which separates the oral fossa from the pharyngeal cavity, breaks. Later on this corresponds to the arrangement of palatine arches, pharyngeal tonsils, and the root of tongue. In front of this place the dentognathic apparatus is forming. To the side of the oral fossa mesenchyma cells growth is noted, the maxillary processes develop.
From the 6lh—7th week of intrauterine development the separation of the oral cavity begins due to the formation of the hard and soft palate; rapid enlargement makes the descending of the tongue possible. The lower jaw, which used to be located behind, is found in the anterior position relative to the upper jaw. Under the tongue pressure the lower jaw growth is stimulated.
In contrast to the upper jaw the lower one is built of Meckel's cartilage in enchondral way, reminding cortical bones. At the moment of child's birth both halves of the lower jaw are connected with fibrocartilage. A part of Meckel's cartilage in posterior regions serves as the matrix for the formation of middle ear elements. From the clinical point of view it should be taken into account that any affection in this region arising from different reasons can cause violation of the development and growth of the temporal bone, elements of the temporomandibular joint, ear. For example, at congenital auricle atresia there are observed deafness and one-sided congenital mandibular micrognathia.
Teeth growth begins from a thin dental plate, which becomes visible during the
8!h week of pregnancy at 12—13 mm of embryo's length. Epithelial dental plates, laid in the jaws mesenchyma, gradually acquire the form of arches. The first signs of temporary teeth dental germs development become visible. The development has a certain sequence and is tightly linked to jaws development. The lower incisors germs are laid earlier and develop quicker than those of the upper incisors, the quicker development of the lower jaw is marked. During the 3rd month of intrauterine development alveolar septa appear in the jaws alveolar processes, at first in the frontal, and later in lateral parts. The irregularity of dental tissues formation and mineralization, taking place during the 16lh month of pregnancy, is observed. During the З^-б1" month of embryogenesis, because of the reinforced development of dental follicles (color insert, Fig. I), considerable growth of alveolar processes takes place. During the 7th—8,h months their growth continues, though the rate of growth and mineralization slows down. From the 9lh month alveolar processes growth increases, temporary teeth germs are surrounded by bony tissue from all sides, intensive mineralization of temporary teeth crowns takes place.
All the prophylactic methods of treating dentognathic anomalies may be divided into such periods:
• the 1st period — before the conception of the child (creation of medicogenetic cabinets);
• the 2nd period — intrauterine;
• the 3rd period — lactational (the first half a year of the child's life);
• the 4Ih period — from 6 months till the end of the temporary occlusion period (2-2.5 years);
• the 5Ih period — transitional dentition occlusion (6—13 years);
• the 6th period — permanent occlusion (from 13 years).
In the process of medicogenetic consultation there are determined:
1)if the person, who has appealed for consultation, is ill with any heritable disease, if the person is a carrier of the disease;
2)if there is a risk of having a child with heritable malformation in the dentofacial and other areas;
3)what complications, caused by a heritable disease, are in one of the partners going to get married, or in a couple going to have a baby; what the risk prognosis of such disorders recurrence in the descendant is;
4)what help the parents can obtain in taking a decision after putting prenatal diagnosis;
5)what prophylactic and medical help may be rendered to the newborn child at the presence of genetically conditioned malformation; where the necessary help may be rendered, in what consequence and in what age periods.
There are differentiated general and special types of dentognathic anomalies prophylaxis. General prophylaxis consists in creating optimal conditions for the growth of the whole organism beginning from the intrauterine period. In this period measures should be taken to prevent injuries, various diseases, and dysbolism of the pregnant woman. The prospective mother is to be protected from harmful psychic, physical or chemical influences; favorable conditions of work and life are to be created for her.
Transversally striated lips (Pfaundler—Liushke's proboscidiform cushions) with the evident orbicular muscle of mouth, which promotes grasping and holding of the nipple. It provides of hermetic oral cavity in time the act of sucking.
Elastic gingival membrane (Roben—Mazhito's fold) in the form of mucous tunic duplicaton with a lot of elastic fibers, which promotes holding of the nipple and press milk.
Fatty interlayer of cheeks and fatty balls of Bichat, which provide negative pressure in the oral cavity during sucking.
4—5 pairs of cross folds, due to which asperity forms in the anterior part of the hard palate, which promotes holding of the nipple.
The tongue is comparatively big. It function like the piston during sucking.
High position of the aperture of larynx (above the level of the inferoposterior margin of the palate veil) and its junction only with the nasal cavity allow the child to breath, suck, and swallow simultaneously.
The articular tubercle absence and occipital inclination of the underdeveloped branch, the wide flat glenoid fossa, the distal position of the lower jaw (physiological retrognathia), the undeveloped intra-articular disk and glenoid fossa create favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
A child is born with the so-called childhood retrognathia (retromandibulism), which can be explained by physiologic necessity, as this eases labor and decreases the possibility of a trauma of the mobile lower jaw. The latter is located in the distal and lingual position relative to the upper jaw by 5—6 mm on average. There is a 2.5—2.7 mm vertical fissure between the alveolar processes, its absence conditions deep occlusion development. The functional load of the lower jaw during the act of sucking promotes its quick elongation. Up to the 6'h—8th month of life during the period of temporary incisors eruption the correlation of jaws normalize therefore the distal correlation of jaws in infants is viewed as a physiological regularity. The 5—6-month-old fetus' jaw is triangular, but during the first 6 months after birth it acquires the form of an arch, and by 4 years — of a parabola.
The widthway growth of the upper jaw takes place during the Iя year of life due to raphes. During the development period, that is during the first 2 years of life, raphes growth slows down sharply. The spread of the palate half is noted as a result of considerable palatine plates growth along the median palatine suture, which promotes alveolar arch increase.
At the moment of child's birth both halves of the lower jaw are connected with fibrocartilage. During the Iя year of life the widthway growth of the lower jaw in the region of symphysis finishes because of its ossification.
A child is born with the so-called childhood retrognathia (retromandibulism), which can be explained by physiologic necessity, as this eases labor and decreases the possibility of a trauma of the mobile lower jaw. The latter is located in the distal and lingual position relative to the upper jaw by 5—6 mm on average. There is a 2.5—2.7 mm vertical fissure between the alveolar processes, its absence is conditions for deep occlusion development. The functional load of the lower jaw during the act of sucking promotes its quick elongation. Up to the 6'h—8th month of life during the period of temporary incisors eruption the correlation of jaws normalizes therefore the distal correlation of jaws in infants is viewed as a physiological regularity.
The lower jaw, being the only movable element of the facial skeleton, during the lactation period is functionally irritated by protruding muscles. 6—7-time feeding of infants, during which the lower jaw makes numerous movements in the antero-posterior direction, promotes the training of this group of muscles and stimulates the lengthwise growth of the lower jaw. As a result of this, during the lactation period jaws correlation changes from retrognathia to normal. At that, the lower jaw during the same period of time enlarges more than the upper one, which can be explained by masticatory muscles activity, especially that of protruding muscles. In this connection the role of natural feeding in the process of facial cranium growth and development, retrognathia elimination, and providing of orthognathic jaws correlation by the end of the I* year of the life increases.
The character and way of feeding are very important in this period. Every feedingof a child (6 times a day during 30 min) promotes training of the lower jaw, mastication, facial, and lingual muscles during 3 hours daily. The zones of bones growth are conditioned genetically and undergo the influence of the environment. Therefore wrong, especially artificial feeding, at which the child gets plenty of milk quickly, does not promote the necessary functional load, and in some cases the child even has to move the lower jaw backwards to swallow food as the head is thrown back. All this delays lower jaw growth, later on physiologic retrognathia can become pathologic, as a result of which posterior occlusion forms.
Act of sucking consist of 4 phases:
1st phase of act of sucking: grasping and holding of the nipple.
2st phase of act of sucking: move of sucking.
3st phase of act of sucking: press of milk.
4st phase of act of sucking: swallow.
The tip of the tongue lowers, enveloping the nipple from the bottom and pressing it against the hard palate, whereupon the lips press against the nipple area of the milk gland, ensuring the closure of the oral cavity space.
At this stage, the back of the tongue is located high up, reaching the hard and the soft palates. The back of the tongue lowers which creates a rarefied space in the oral cavity.
Grasping and holding of the nipple is provided by:
· Transversally striated lips (Pfaundler—Liushke's proboscidiform cushions) with the evident orbicular muscle of mouth;
· 4—5 pairs of cross folds, due to which asperity forms in the anterior part of the hard palate;
· Elastic gingival membrane (Roben—Mazhito's fold;
· Fatty interlayer of cheeks and fatty balls of Bichat.
· the grasping reflexes
2st phase of act of sucking: move of sucking is provided by:
· comparatively big tongue.
· fatty interlayer of cheeks and fatty balls of Bichat.
· the sucking reflexes
During 2st phase of act of sucking milk from the deep part of the milk gland move to the nipple.
3st phase of act of sucking: press of milk is provided by the next pecularities: articular tubercle absence and occipital inclination of the underdeveloped branch, the wide flat glenoid fossa, the distal position of the lower jaw (physiological retrognathia), the undeveloped intra-articular disk and glenoid fossa create favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
During 3st phase of act of sucking the milk from the nipple enters the oral cavity.
4st phase of act of sucking: swallow. The milk flows from the oral cavity into both the oral pharynx and on into the esophagus. High position of the aperture of larynx (above the level of the inferoposterior margin of the palate veil) and its junction only with the nasal cavity allow the child to breath, suck, and swallow simultaneously.
The articular tubercle absence and occipital inclination of the underdeveloped branch, the wide flat glenoid fossa, the distal position of the lower jaw (physiological retrognathia), the undeveloped intra-articular disk and glenoid fossa create favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
Improper forceps application during delivery can lead to condylar damage/ fracture thereby causing internal hemorrhage into the joint area. The joint area may later become ankylosed or fibrosed leading to under development of mandible or mandibular growth retardation. This deformity’names “Bird face” deformity. The facial appearance of growth disturbance in “Bird face” deformity patients is well described and includes characteristic features of small mandible, Angles class II malocclusion (mandibular retrognathia) (unilateral or bilateral), anterior open bite, lower incisor crowding, and incisal protrusion. The facial disturbance is largely due to a backward rotational growth pattern of the mandible.
After the child's birth favorable environment is necessary for its development and general diseases prevention. Regimen and character of feeding are of special concern. Correct position of the child's head during sleep should be watched. Lactational period is characterised by moderate influence on the organism of the mother and formation of the child's organism. This period is also only prophylactic. Except for the influence on the organism of the wet nurse with the purpose of increasing the quantity and quality of milk, there is also exerted the direct influence on the child's organism, which consists in improving the conditions of its existence.
Is recommended beginning first walks with the child since 3—4 weeks' age in cold season (temperature being —15° C). In summer at temperature not lower than +18° С (in the shadow) with no wind the child since 3-months' age is to be habituated to air-baths. In other seasons air-baths are to be conducted indoors, beginning from a month's age.
Correct child-minding is also important. The child should not be overheated by excessive wrapping: cloths and bed linen should not cause sweating, the child must get everyday hygienic baths, and beginning from 2-months' age — sponged down with warm (37° C) salty water.
The child is to be fed with breast milk, which is useful in the view of physiology as more valuable than feeding formulae; it is the healthiest kind of food.
I.P. Pavlov writes: "Secretory work of the stomach for milk assimilation is significantly less in comparison with any other food". For breast milk digestion little fermentative capability of the gastric and pancreatic juices is enough, and in a 3—4-month-old child the secretory activity of digestive glands is qualitatively and quantitatively weaker and milk substitutes are poorly digested. The more favorable ratio of calcium and phosphorus (1: 1) in the woman's milk than in the animals' milk also plays some role.
Artificially fed children have been found to fall ill more often and more severely than naturally fed children. The former also put on weight slowly.
Therefore, mothers are to be convinced to feed children with breast milk longer; of course, the mother's state of health should be taken into account. In cases of artificial feeding measures should be taken to liken it to the natural one. For this purpose, the nipple of the milk bottle should be made of rubber reminding mamilla by its form and elasticity. The bottle should be held not vertically but horizontally so that the milk is not poured into the child's mouth by itself, the child must make efforts to suck milk from the bottle. It should also be attended that the bottle with milk does not press on the lower jaw in order to avoid its deformation. Finally, the mother ought not put the bottle with milk into the child's mouth and leave the child lying as it is often done, but the child should be hold in hands during feeding. All this creates such conditions, which are at least somehow close to natural.
By the end of the first or second month of life some children suck their fists for a long time, therefore the prophylaxis of sucking fingers and fists should begin from the first days of the child's life.
The child should also be habituated to the correct position during sleep: not to put a fist under the cheek, not to sleep with the head thrown back or bent down.
Engel on direct observation of infants during the first year of life revealed their organization to be an oral and clinging one. At birth, the child has a reflex pattern of neuromuscular functions such as sucking.
The habit of sucking is a reflex occurring in the oral stage of development and disappears during normal growth between 1-2 years. Even before birth, oral contractions and other reflexes have been observed. This early neural organization allows the in faot to nurse and cling to the mother as evidenced by the sucking and the grasping reflexes. With hearing and vision development, the baby tries to reach and transport to its mouth, what it has seen and heard at a distance. The baby tends to persist until all possible objects are carried into his mouth.
Tests for determining the initial level of knowledge (α = 2).
1. In what week of intrauterine development does the facial part begin to form?
1. 3rd
2. 10th.
3. 2nd.
4. 7th
5. 24th
2. In what week does the the septum, which separates the oral fossa from the pharyngeal cavity, breaks?
1. 17th.
2. 9th.
3. 20th.
4. 4th.
5. 25th.
3. In what week of intrauterine development does temporary teeth anlage begin?
1. 3rd
2. 10th.
3. 12th.
4. 7th
5. 24th
4. In what week does the anlage of 6321 / 1236 teeth begin?
1. 8th.
2. 13th.
3. 20th.
4. 25th.
5. 16th.
5. In what week of intrauterine development does the separation of the oral cavity begins due to the formation of the hard and soft palate?
1. 3rd
2. 10th.
3. 12th.
4. 7th
5. 24th
6. Name the embryonic structures taking part in lower lip formation
1. Frontonasal.
2. Medial nasal.
3. Lateral nasal.
4. Maxillary.
5. Mandibulary.
7. Name the embryonic structures taking part in upper lip formation
1. Medial nasal.
2. Medial nasal and Lateral nasal.
3. Lateral nasal.
4. Medial nasal and Maxillary.
5. Mandibulary.
8. Name the embryonic structures taking part in lower jaw formation
1. Medial nasal.
2. Medial nasal and Lateral nasal.
3. Lateral nasal.
4. Medial nasal and Maxillary.
5. Mandibulary.
9. Name the embryonic structures taking part in upper jaw formation
1. Medial nasal.
2. Medial nasal and Lateral nasal.
3. Lateral nasal.
4. Medial nasal and Maxillary.
5. Mandibulary.
10. Name the embryonic structures taking part in incisial bone formation
1. Medial nasal.
2. Medial nasal and Lateral nasal.
3. Lateral nasal.
4. Medial nasal and Maxillary.
5. Mandibulary.
11. What form does the 5—6-month-old fetus' jaw have?
1. the form of an arch
2. triangular
3. parabola
12. What is Pfaundler-Liushke’s proboscidiform cushions?
a. Transversally striated lip
b. Elastic gingival membrane in the form of mucous tunic duplicaton with a lot of elastic fibers.
c. Fatty interlayer of cheeks.
d. 4—5 pairs of cross folds in the anterior part of the hard palate
e. The comparatively big tongue.
13. What is Pfaundler-Liushke’s proboscidiform cushions function?
a. It promotes grasping and holding of the nipple. It provides of hermetic oral cavity in time the act of sucking.
b. It promotes holding of the nipple and press milk.
c. It provides negative pressure in the oral cavity during sucking.
d. It allows the child to breath, suck, and swallow simultaneously.
e. It creates favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
14. What is Roben-Mazhito’s fold cushions?
a. Transversally striated lip
b. Elastic gingival membrane in the form of mucous tunic duplicaton with a lot of elastic fibers.
c. Fatty interlayer of cheeks.
d. 4—5 pairs of cross folds in the anterior part of the hard palate
e. The comparatively big tongue.
15. What is Roben-Mazhito’s fold cushions. function?
a. It promotes grasping and holding of the nipple. It provides of hermetic oral cavity in time the act of sucking.
b. It promotes holding of the nipple and press milk.
c. It provides negative pressure in the oral cavity during sucking.
d. It allows the child to breath, suck, and swallow simultaneously.
e. It creates favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
16. What is fatty balls of Bichat?
a. Transversally striated lip
b. Elastic gingival membrane in the form of mucous tunic duplicaton with a lot of elastic fibers.
c. Fatty interlayer of cheeks.
d. 4—5 pairs of cross folds in the anterior part of the hard palate
e. The comparatively big tongue.
17. What is fatty balls of Bichat function?
a. It promotes grasping and holding of the nipple. It provides of hermetic oral cavity in time the act of sucking.
b. It promotes holding of the nipple and press milk.
c. It provides negative pressure in the oral cavity during sucking.
d. It allows the child to breath, suck, and swallow simultaneously.
e. It creates favorable conditions for the unhampered movement of the lower jaw in the sagittal plane during sucking.
18. Where does 4-5 pairs of cross folds localize?
a. in the anterior part of the soft palate.
b. in the posterior part of the hard palate
c. in the middle part of the hard palate
d. in the anterior part of the hard palate
e. in the posterior part of the soft palate
19. What is peculiarities of the infant’s tongue?
a. The tongue is comparatively small.
b. The tongue is comparatively big.
c. The tongue is absent.
20. Why the infant can breathe, suck and swallow simultaneously?
a. position of the aperture of larynx under the level of the inferoposterior margin of the palate veil.
b. position of the aperture of larynx such as the level of the inferoposterior margin of the palate veil.
c. position of the aperture of larynx above the level of the inferoposterior margin of the palate veil.
d. the aperture of larynx junctions only with the oral cavity.
e. the aperture of larynx junctions with the nasal and oral cavity.
21. What peculiarities of the infant’s TMJ do allow him to suck?
a. the glenoid fossa is deep
b. the intra-articular disk is developed
c. the distal position of the lower jaw (pathological retrognathia)
d. the articular tubercle is absent
e. the mesial position of the lower jaw
22. What peculiarities of the infant’s lower and upper jaw position do allow him to suck?
a. the mesial position of the lower jaw
b. the distal position of the lower jaw (physiological retrognathia)
c. the distal position of the lower jaw (pathological retrognathia)
d. the distal position of the upper jaw
e. the mesial position of the upper jaw
23. In what plane is movement of the infant’s lower jaw during sucking?
a. Vertical
b. Transversal
c. Sagittal
d. Transversal and sagittal
e. Transversal and vertical
24. What form does infant’s jaw have during the first 6 months after birth?
a. The form of an arch
b. Triangular
c. parabola
25. What distance is between infant’s upper and lower jaws during the first 6 months after birth on average?
a. 1-2 mm
b. 3-4 mm
c. 5-6 mm
d. 7-8 mm
e. 9-10 mm
26. In what age does correlation of jaws normalize?
a. 1'h—2th month
b. 3'h—4th month
c. 6'h—8th month
d. 12'h—18th month
e. 24'h—30th month
Control questions to determine of the final level of knowledge (α = 3).
1. How do infant’s jaws correlate? Why is this correlation important?
2. How does the character and way of feeding influence occlusion forming?
3. Biomechanics of act of sucking.
4. Biomechanics of act of sucking. 1st phase. Describe. What anatomical structures take part in this act?
5. Biomechanics of act of sucking. 2nd phase. Describe. What anatomical structures take part in this act?
6. Biomechanics of act of sucking. 3d phase. Describe. What anatomical structures take part in this act?
7. Biomechanics of act of sucking. 4th phase. Describe. What anatomical structures take part in this act?
8. Characterize peculiarities of the infant’s TMJ and lower jaw position which allow him to suck?
9. What factors threaten to the normal development of the dentognathic apparatus in the period of infancy?
Home tasks
1. Write main stages of ontogenetic forming of maxillofacial organs (table)
| № | Stage of face forming | Term |
2. Divide etiological factors of forming of dentognathic anomalies that influence during prenatal period
| № | Etiological factor | Internal | External |
3. Make conversation thesis in complex of primary prophylactics of dentognathic anomalies for pregnant women.
4. To divide anatomical peculiarities by their task
| № | Anatomical peculiarity of a newborn | Function of an oral cavity which it optimizes |
Literature:
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