DENTAL APPARATUS DEVELOPMENT IN THE BAIKAL SEAL IN ONTOGENESIS

The aim of this study is to investigate the development of the dental apparatus in the Baikal seal. Dental formation in the Baikal seal begins during the prenatal period of ontogenesis. In the fetus, at 4–5 months of age (including diapause), jaw bone tissue forms through direct osteogenesis. In the fetus, at 6–7 months of age, developing teeth are already present in the bone base of the jaws. The crown denticles are composed of bone (dentinoid) tissue, while the rest of the tooth is still composed of connective tissue. In the Baikal seal, there is no transition from deciduous to permanent teeth – the first set of erupted teeth is retained throughout life. In newborn seals, teeth are represented by bony enamel organs filled with a tooth germ. The surface of the enamel organ is differentiated by color into the crown, neck, and root of the tooth. The roots are not yet formed, but in their place are openings that correspond to their presence and number. The dental sac attaches to the edge of the future root while it is still in the gum. This sac covers the enamel organ, which is the future periodontium and cementum. Within the cavity of the enamel organ is the dental pulp chamber (tooth germ), which consists of connective tissue with a large number of collagen fibers and fibroblast cells with an abundance of neurovascular structures. In newborns, odontoblasts form several layers around the periphery of the pulp chamber. The odontoblasts are tightly adjacent to the predentin. By 3–4 weeks of age, all roots of the enamel organ and tooth germ have completed their growth on the upper and lower jaws. By 3–5 months, the Baikal seal already has a fairly well-formed enamel layer, bordering the dentin layer, which develops from the predentin. As the seal ages, the dentin layer thickens and the odontoblast layer thins. The beginning of tooth eruption is observed in newborn puppies, with the apices of all molars visible on the upper jaw, while only the third, fourth, and fifth molars are visible on the lower jaw. In puppies aged three to four weeks, the dental arcade is fully visible. The dental formula is as follows: 2× I 3/2 : C 1/1 : M 5/5 = 34.