Odontoblasts are tooth-forming mesenchymal cells of the dentition and secrete so-called predentin to dentinize the teeth. After tooth formation is complete, they maintain the teeth and repair them in cases of chewing and decay. In avitaminoses such as vitamin C deficiency, irreversible degeneration of the cells often occurs.
What are odontoblasts?
With the milk teeth and the change of teeth, tooth-forming processes take place twice in the human organism. Odontoblasts play an important role in these processes. These are highly specialized cells of the dental tissue. They have mesenchymal origin and develop from the ectodermal neural crest. After their differentiation, the cells are significantly involved in the development of teeth. Throughout their life, they produce predentin, which is known as the organic precursor of the tooth substance dentin. In tooth development terms, the formation of dentin is known as dentinization or dentinogenesis. Odontoblasts provide the necessary material for this dentinogenesis. As cells of the mesenchymal connective tissue, they are related to osteoblasts and fibroblasts. Just as osteoblasts perform bone-building tasks, they perform tooth-forming functions. Except for hard enamel, the mesenchyme provides all the components of teeth. Because of their direct connection to the nervous system, odontoblasts also play a crucial role in the perception of pain in the dentition.
Anatomy and structure
During tooth development, epithelial cells in Hertwig’s sheaths initiate the development of osteoblasts. They induce the cells of the adjacent mesenchyme to differentiate. Thus, the mesenchyme cells give rise to odontoblasts. The odontoblasts then settle in the border area between pulp and dentin. The former mesenchyme cells have a cylindrical shape and palisade-like arrangement. Because they form dentin throughout their entire life, the pulp cavum decreases in size with increasing age. The fine cell processes of the odontoblasts are called Tomes’ fibers. During the formation of dentin, calcification of the predentin occurs at these structures, creating dentinal tubules. These channels are called Tomes’ channels and correspond to the fine, hair-shaped cavities that run from the inside to the outside of the formed dentin. The canals are filled by the projections of the odontoblasts, which can be up to five millimeters long. Each odontoblast is also in direct contact with free nerve endings.
Function and tasks
Odontoblasts secrete predentin, known as the organic precursor of dentin, to form teeth. Thus, they are instrumental in odontogenesis. Dentin formation is also referred to as dentinogenesis. During tooth formation, this process appears as the first recognizable feature of the crown stage. The odontoblasts differentiate from the dental papilla cells and secrete an organic matrix at the later tooth apex, which is close to the inner epithelium. The matrix consists of collagen fibers with diameters up to 0.2 μm. The odontoblasts migrate to the center of the future tooth. There they form offshoots, which is also called the odontoblast process. The offshoot initiates the secretion of hydroxyapatite crystals. Mineralization of the organic matrix begins. The mantle dentin forms from pre-existing basic substances of the dental papilla. Primary dentin is formed by processes of odontoblasts. The cells increase in size until no extracellular resources can contribute to the organic matrix. Large odontoblasts secrete little collagen and grow structurally heterogeneous nuclei. In addition to collagen secretion, lipids, phosphoproteins, and phospholipids are secreted at this stage. When tooth formation is complete, odontoblasts lose the ability to divide. They come to rest in the pulp periphery and maintain the dentin mantle of the teeth for the rest of their lives by growing secondary and tertiary dentin. Secondary dentin forms significantly slower than primary dentin. Formation takes place only after root formation is complete. In the immediate vicinity of the crown, development is faster than elsewhere on the tooth. Tertiary dentin is also referred to as reparative dentin and forms reactively to chewing or caries.
Diseases
Vitamin deficiencies can show effects on odontoblasts. This is especially true for vitamin C deficiency.Avitaminosis C is also known as scurvy and used to be particularly common among sea travelers without a balanced food supply. The associated deficiency of ascorbic acid endangers the cohesion of the tissues, as sufficient putty substance can no longer be produced. In the musculature, capillary blood leakage leads to small foci of hemorrhage. In bone, cartilage cells and epiphyses detach and edema often develops in the mouth. The odontoblasts are equally affected by vitamin C deficiency. They slowly degenerate and no longer release dentin in sufficient quantities. They are sealed off from the predentin, which further promotes their degeneration. Since the degenerated cells are no longer capable of repairing the teeth due to reduced dentin production, the teeth are hit all the harder by diseases such as caries. Somewhat less common than avitaminoses are dentinal dysplasia of the radicular and coronal forms or dentinogenesis imperfecta. In these hereditary diseases, dentinogenesis by odontoblasts is disturbed. Large cavities appear within the dentin. The teeth wear down more easily and are more susceptible to fractures. The symptoms of the hereditary diseases can be alleviated by endodontic and endosurgical measures as needed. If the teeth cannot be preserved, they are removed. After removal, implant placement can take place if needed.
Typical and common dental diseases.
- Tooth loss
- Tartar
- Toothache
- Yellow teeth (tooth discoloration)
