FEATURES OF MORPHOGENESIS OF THE BONES OF THE HUMAN ORBIT.

OBJECTIVE: The aim: To find out the sources of origin, the chronology of ossification, the peculiarities of age-related topographical and anatomical changes in the bones of the human orbit. PATIENTS AND METHODS: Materials and methods: The research was carried out on the specimens of 18 human embryos and prefetuses aged from 4th to 12th weeks of intrauterine development and 12 human fetuses aged from 4th to 9th months which were studied by microscopic examination and 3D reconstruction. RESULTS: Results: The first signs of osteogenesis around the main nervous and visceral contents of the orbit rudiment are observed in 6-week-old embryos in the form of seven cartilaginous bone models. The first signs of ossification in the region of the orbit are found in the maxilla. During the 6th month of intrauterine development, intensive processes of ossification of the frontal, sphenoidal, ethmoidal bones and maxilla are noticeable. From the beginning of the fetal pe¬riod of human ontogenesis, the ossification of bone rudiments that form the walls of the orbit continues. The processes of ossification of the structures of the sphenoidal bone continue, which leads to morphological transformations of the orbit in 5-month-old fetuses - it is separated from the sphenopalatine and infratemporal fossae by a bone layer, the optic canal is formed, and in 6-month-old fetuses, processes of ossification of the frontal, sphenoidal and ethmoidal bones and maxilla occur, Müller's muscle changes its structure to a fibrous one. CONCLUSION: Conclusions: Critical periods of the orbit development are the 6th month of prenatal ontogenesis and the 8th month.

PECULIARITIES OF THE HUMAN MAXILLA MORPHOGENESIS.

OBJECTIVE: The aim: To find out the sources of formation and the chronological sequence of the morphogenesis of the maxilla at the early stages of human ontogenesis. PATIENTS AND METHODS: Materials and methods: 14 series of consecutive histological specimens of human embryos and prefetuses (4,0-66,0 mm of parietal-coccygeal length) aged from 4 to 11 weeks of intrauterine development with the use of a complex of modern morphological methods of investigation (anthropometry, morphometry, microscopy, and 3D computer reconstruction) were studied. RESULTS: Results: On the basis of a complex of morphological research methods, data were obtained that made it possible to establish the general patterns of development of the human maxilla: separation of the pharyngeal apparatus (4th week), convergence and fusion of the jaw processes (5-8th weeks), formation of tooth buds (7-8th weeks), which allows considering the specified periods as critical in the formation of possible anomalies in the facial part of the skull. At the same time, a tendency of heterochrony of morphological transformations in the maxilla and maxilla was revealed. CONCLUSION: Conclusions: 1. At the beginning of the 4th week of intrauterine development, 3 pairs of pharyngeal arches are formed. Detachment of the mandibular and maxillary processes of the mandibular pharyngeal arch is planned. 2. During the 7th week of intrauterine development, the maximum convergence of the maxillary processes with the lateral and medial nasals occurs, and in embryos of 20.0 mm PCL grow with the frontal process, forming the maxilla and upper lip. During the 8th week of intrauterine development, the bone base of the jaws is modeled as a result of the increase in the size of osteogenic islands and their fusion, alveolar processes are formed. 3. During the 9-10th weeks of intrauterine development, the primary palate is formed as a result of the fusion of the palatine processes. 4. At the 11th week of intrauterine development, the bone base models both jaws. Due to the processes of histogenesis of the soft tissues of the maxillofacial apparatus, the face acquires anthropomorphic definitive human features.

PECULIARITIES OF THE SOURCES OF ORIGIN AND MORPHOGENESIS OF THE HUMAN MANDIBLE.

OBJECTIVE: The aim: To determine the sources and terms of origin, developmental peculiarities and dynamics of ossification of the mandible during the prenatal period of human ontogenesis. PATIENTS AND METHODS: Materials and methods: The research was carried out on the specimens of 30 embryos, 30 pre-fetuses and 60 human fetuses at the period from the 9th to the 12th weeks of the intrauterine development, which were studied by microscopic examination. Three-dimensional computer reconstructions of the human pre-fetal head were made. RESULTS: Results: During the 7th week of development the maxillary processes maximum approach the lateral and medial nasal ones; in pre-fetuses 20,0 mm of PCL they join the frontal spindle forming the facial structures (upper jaw and lip, vestibule of the oral cavity, rudiments of dental laminas, and rudiments of dental buds in its distal portions). Osteogenous islets, rudiments of the mimic and masticatory muscles, blood vessels are formed. During the 8th week of development the osseous tissue of the mandible is formed, the alveolar processes are formed. The oral and nasal cavities are isolated in 9-10-week pre-fetuses, the mass of the osseous tissue increases in both jaws, the enamel organs are detached, the angles and rami formed by the hyaline cartilaginous tissue of the mandible are determined, the rudiments of the temporomandibular joints are already seen. During the 11th week of development the osseous base of both jaws become formed. Till the end of the 12th week the osseous tissue begins to replace the hyaline cartilage of the mandibular rami, and the articular heads are formed in the portion of their proximal ends. CONCLUSION: Conclusions: The mandible in its development is known to be characterized by intra-cartilaginous formation of the bone which starts from the ends of the cartilage gradually displaced by the osseous tissue. It is indicated that both jaws in pre-fetuses 37,0 and 42,0 mm of PCL are presented by the typical cartilaginous tissue, and in pre-fetuses 45,0-50,0 mm of PCL the osseous tissue is already available replacing the cartilaginous one.

MORPHOMETRIC ANALYSIS OF TOPOGRAPHIC VARIABILITY OF THE LEFT AND RIGHT MANDIBULAR CANALS IN CASE OF LOSS OF THE MASTICATORY TEETH.

OBJECTIVE: The aim: To study the topographic variability of the left and right mandibular canals in case of bone atrophy caused by the loss of the masticatory teeth. PATIENTS AND METHODS: Materials and methods: 136 digital scans were selected for morphometric analysis, 68 for each side taken with the Vatech PaX-i 3D Green extra-oral radiography system. The readout of absolute morphometric values, laying the left and right MC was performed in the projection of 3.7, 3.6, 4.6, 4.7 teeth using standardized Ez3D-I software. RESULTS: Results: The alveolar part is characterized by distance to the alveolar ridge, and primarily exposed to pronounced atrophic processes of bone tissue. Distance to the lingual ridge directly proportionally indicates the morphological transposition vector of the mandibular canals for the distance to the buccal ridge, by the same length to its reduction. Morphometric analysis on a short toothless segment determines the variability of laying the mandibular canals but it is characterized by constant regular values of the ridge of the mandibular base. CONCLUSION: Conclusions: Dentition defects, moving towards the missing teeth, lead to a decrease in the biophysical stimulus on bone tissue, causing pronounced morphological changes with the loss of significant volume and restructuring of its trabecular layer, which synchronously affects the topographic variability of the left and right MC.

PECULIARITIES OF THE MORPHOMETRIC PARAMETERS OF SUPRAHYOID REGION OF THE HUMAN PREFETUSES.

OBJECTIVE: The aim: To determine the peculiarities of the morphometric parameters of suprahyoid region of the human prefetuses. PATIENTS AND METHODS: Materials and methods: Thirty specimens of human prefetuses of 14.0-80.0 mm parietococcygeal length (PCL) (7-12 weeks of IUD) were studied using a complex of modern methods of morphological research. RESULTS: Results: On the basis of obtained digital indicators of the main morphometric parameters of human SHR in the dynamics of the prenatal period of IUD the critical periods of development of the region were clarified and mathematical functions that describe the normal course of organogenesis of SHR were created, which can be useful for creating diagnostic algorithms for the norm when carrying out prenatal diagnostics and monitoring the state of the fetus. It has been established that the 9-10th week of IUD is a critical period in the development of SHR, since during this time, intensive growth processes occur, which are manifested by a sharp change in the size of the organ, and this can lead to the appearance of variants of the structure and possible congenital defects of the SHR and the dental-maxillary apparatus in general. CONCLUSION: Conclusions: 1.Age-depended dynamics of changes in the anterior angle of the SHR shows an almost linear decrease in the angle by the end of the 9th week of IUD almost to 76°, after which it increases to almost 90° by the end of the 10th week. From the 11th week of the IUD, the anterior angle decreases again to 77 °, but begins to increase at the 12th week and by the end of the prefeal period. 2.The lateral length of SHR increases almost uniformly until the 9th week of IUD, during which its growth rate slows down. Starting from the end of the 10th week of IUD, this morphometric parameter begins to grow rapidly until the end of the prenatal period of ontogenesis. The growth rate of the lateral length of the SHR is described by the function: L lat = 1.1025 + 0.0015 x + 0.001 x2. 3.The width of the SHR from the 10th week of IUD begins to grow rapidly until the end of the prenatal period of development. The growth rate of the width of SHR is described by the function: W = 1.1025 + 0.0015 x + 0.001 x2. 4.Analysis of the age dynamics of the area of SHR demonstrates the exponential dependence on the age of the prefetuses, which is described by a mathematical function: A = 1,2452exp(0,0424x). Meanwhile, there is a slight slowdown in its growth rate at the 10th week of IUD with subsequent recovery of growth by the end of the prenatal period of ontogenesis. 5.The 9-10th week of IUD is a critical period in the development of SHR, since during this time, intensive growth processes occur, which are manifested by a sharp change in the size of the mandible.