Odontoblast

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Odontoblast
Enamelmineralization11-17-05.jpg
A developing tooth with odontoblasts marked.
Cervical-loop.png
The cervical loop area: (1) dental follicle cells, (2) dental mesenchyme, (3) Odontoblasts, (4) Dentin, (5) stellate reticulum, (6) outer enamel epithelium, (7)inner enamel epithelium, (8) ameloblasts, (9) enamel.
Details
Precursor Neural crest
Location Tooth
Identifiers
Latin odontoblastus
MeSH D009804
FMA 62999
Anatomical terms of microanatomy

In vertebrates, an odontoblast is a cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the formation of dentin, the substance beneath the tooth enamel on the crown and the cementum on the root.

Contents

Structure

Odontoblasts are large columnar cells, whose cell bodies are arranged along the interface between dentin and pulp, from the crown to cervix to the root apex in a mature tooth. The cell is rich in endoplasmic reticulum and Golgi complex, especially during primary dentin formation, which allows it to have a high secretory capacity; it first forms the collagenous matrix to form predentin, then mineral levels to form the mature dentin. Odontoblasts form approximately 4 μm of predentin daily during tooth development. [1]

During secretion after differentiation from the outer cells of the dental papilla, it is noted that it is polarized so its nucleus is aligned away from the newly formed dentin, with its Golgi complex and endoplasmic reticulum towards the dentin reflecting its unidirectional secretion. Thus with the formation of primary dentin, the cell moves pulpally, away from the basement membrane (future dentinoenamel junction) at the interface between the inner enamel epithelium and dental papilla, leaving behind the odontoblastic process within the dentin. The odontoblastic cell body keeps its tapered structure with cytoskeletal fibres, mainly intermediate filaments. Unlike cartilage and bone, as well as cementum, the odontoblast's cell body does not become entrapped in the product; rather, one long, cytoplasmic attached extension remains behind in the formed dentin. [2] The differentiation of the odontoblast is done by signaling molecules and growth factors in the cells of the inner enamel epithelium. [1]

Like enamel, dentin is avascular. Nutrition for odontoblasts within the dentin comes through the dentinal tubules from tissue fluid that originally traveled from the blood vessels located in the adjacent pulp tissue. Within each dentinal tubule is a space of variable size containing dentinal fluid, an odontoblastic process, and possibly an afferent axon (see next discussion). The dentinal fluid in the tubule presumably also includes the tissue fluid surrounding the cell membrane of the odontoblast, which is continuous from the cell body in the pulp. [2]

It has been shown that odontoblasts secrete the extracellular matrix protein reelin. [3] [4] [5]

A pulpal A-delta (noxious, short sharp pain) nerve fibre is either wrapped around the base of this process, or travels a short way into the dentinal tubule with the odontoblast process (max ~0.1 mm) This process lies in the dentinal tubule. In primates enamel spindles were observed where the odontoblast process reaches until the border between dentin and enamel. With the discovery of TRPC5 as cold transducer the odontoblast transduction theory has become a likely explanation of dentinal hypersensivity [6]

The contribution of TRPC5 channels to the sensory function in odontoblasts is still controversial [7]

It has been shown that odontoblast-neuron signal communication via Piezo1/TRPA1 channels and pannexin-1 in odontoblasts and P2X3 receptors in A-delta neuron is involved in the generation of dentinal sensitivity/hypersensitivity. Oodontoblasts are necessary for sensory transduction to generate dentinal sensitivity as mechanosensory receptor cells. [8]

Development

Odontoblasts first appear at sites of tooth development at 17–18 weeks in utero and remain present until death unless killed by bacterial or chemical attack, or indirectly through other means such as heat or trauma (e.g. during dental procedures). Odontoblasts were originally the outer cells of the dental papilla. Thus, dentin and pulp tissue have similar embryological backgrounds, because both are originally derived from the dental papilla of the tooth germ. [2]

Function

  1. To aid in the secretion of intertubular and peritubular dentin (the dentin surrounding odontoblastic process) that forms the dentinal tubule, which further organizes and strengthens the dentin as a whole
  2. General maintenance of both the dentinal tubule and dentinal fluid (ion/protein content etc.)
  3. To secrete sclerotic dentin upon carious attack to block off dentinal tubules, slowing the progress of the attack (air space above blockage is known as a dead tract)
  4. To channel signals of attack to the odontoblastic cell body, thus initiating secretion of reactionary dentin
  5. To act as cellular component of the dental temperature sensing system either by sensing temperature changes directly or by detecting hydrokinetic forces of fluid movement in the tubules or a combination of both. [6]

The odontoblasts secrete dentin throughout life, unlike enamel, which is considered secondary dentin once root formation is complete, which may be an attempt to compensate for natural wear of the enamel. This is because of the retention of the odontoblasts within the tooth, along the outer pulpal wall. [2]

Odontoblasts also secrete tertiary dentin when irritated. Tertiary dentin secreted by odontoblasts is often due to chemical attack, either by chemicals diffusing through the dentin and insulting the odontoblasts, or by diffusion of toxic bacterial metabolites down the dentinal tubules in the instance of a carious attack with dental decay. This tertiary dentin is called reactionary dentin. This is an attempt to slow down the progress of the caries so that it does not reach the pulp.

In the case of an infection breaching the dentin to or very near the pulp, or in the instance of odontoblast death due to other attack (e.g. chemical or physical), undifferentiated mesenchymal cells can differentiate into odontoblast-like cells which then secrete another type, reparative dentin, underneath the site of attack. This is not only to slow the progress of the attack, but also prevents the diffusion of bacteria and their metabolites into the pulp, reducing the probability of partial pulp necrosis.

The distinction of the two kinds of tertiary dentin is important, because they are secreted by different cells for different reasons. Reactionary dentin is secreted at varying speeds, dependent on the speed of progression of caries in the outer dentin surface. Histologically, it is easily distinguishable by its disordered tube structure, the location of the secretion (it protrudes into the pulpal cavity) and its slightly lower degree of mineralization than normal. The tooth is often able to be saved by a simple restoration. In contrast, reparative dentin is secreted when the tooth has a poor prognosis.

Other animals

Teeth in the molluscan radula are also produced by cells termed "odontoblasts".

See also

Related Research Articles

<span class="mw-page-title-main">Human tooth</span> Calcified whitish structure in humans mouths used to break down food

Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

<span class="mw-page-title-main">Cementum</span> Specialized calcified substance covering the root of a tooth

Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.

<span class="mw-page-title-main">Tooth decay</span> Deformation of teeth due to acids produced by bacteria

Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors, from yellow to black. Symptoms may include pain and difficulty eating. Complications may include inflammation of the tissue around the tooth, tooth loss and infection or abscess formation. Tooth regeneration is an on-going stem cell based field of study that is trying to reverse the effects of decay, unlike most current methods which only try to make dealing with the effects easier.

<span class="mw-page-title-main">Dentin</span> Calcified tissue of the body; one of the four major components of teeth

Dentin or dentine is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By volume, 45% of dentin consists of the mineral hydroxyapatite, 33% is organic material, and 22% is water. Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive and can become hypersensitive to changes in temperature due to the sensory function of odontoblasts, especially when enamel recedes and dentin channels become exposed.

<span class="mw-page-title-main">Pulp (tooth)</span> Part in the center of a tooth made up of living connective tissue and cells called odontoblasts

The pulp is the connective tissue, nerves, blood vessels, and odontoblasts that comprise the innermost layer of a tooth. The pulp's activity and signalling processes regulate its behaviour.

<span class="mw-page-title-main">Ameloblast</span>

Ameloblasts are cells present only during tooth development that deposit tooth enamel, which is the hard outermost layer of the tooth forming the surface of the crown.

<span class="mw-page-title-main">Bone canaliculus</span> Canal system in bones

Bone canaliculi are microscopic canals between the lacunae of ossified bone. The radiating processes of the osteocytes project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do not entirely fill up the canaliculi. The remaining space is known as the periosteocytic space, which is filled with periosteocytic fluid. This fluid contains substances too large to be transported through the gap junctions that connect the osteocytes.

<span class="mw-page-title-main">Enamel organ</span> Aggregate of cells involved in tooth development

The enamel organ, also known as the dental organ, is a cellular aggregation seen in a developing tooth and it lies above the dental papilla. The enamel organ which is differentiated from the primitive oral epithelium lining the stomodeum. The enamel organ is responsible for the formation of enamel, initiation of dentine formation, establishment of the shape of a tooth's crown, and establishment of the dentoenamel junction.

<span class="mw-page-title-main">Human tooth development</span> Process by which teeth form

Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stages of fetal development. Primary (baby) teeth start to form between the sixth and eighth week of prenatal development, and permanent teeth begin to form in the twentieth week. If teeth do not start to develop at or near these times, they will not develop at all, resulting in hypodontia or anodontia.

Amelogenesis is the formation of enamel on teeth and begins when the crown is forming during the advanced bell stage of tooth development after dentinogenesis forms a first layer of dentin. Dentin must be present for enamel to be formed. Ameloblasts must also be present for dentinogenesis to continue.

<span class="mw-page-title-main">Dental papilla</span>

In embryology and prenatal development, the dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8–10 weeks of intra uteral life. The dental papilla gives rise to the dentin and pulp of a tooth.

Dentinogenesis is the formation of dentin, a substance that forms the majority of teeth. Dentinogenesis is performed by odontoblasts, which are a special type of biological cell on the outer wall of dental pulps, and it begins at the late bell stage of a tooth development. The different stages of dentin formation after differentiation of the cell result in different types of dentin: mantle dentin, primary dentin, secondary dentin, and tertiary dentin.

Pulpitis is inflammation of dental pulp tissue. The pulp contains the blood vessels, the nerves, and connective tissue inside a tooth and provides the tooth's blood and nutrients. Pulpitis is mainly caused by bacterial infection which itself is a secondary development of caries. It manifests itself in the form of a toothache.

An odontoblast process is an extension of a cell called an odontoblast, which forms dentin in a tooth. The odontoblast process is located in dentinal tubules. It forms during dentinogenesis and results from a part of the odontoblast staying in its location as the main body of the odontoblast moves toward the center of the tooth's pulp. The odontoblast process causes the secretion of hydroxyapatite crystals and mineralization of the matrix secreted by the odontoblasts.

Dentin hypersensitivity is dental pain which is sharp in character and of short duration, arising from exposed dentin surfaces in response to stimuli, typically thermal, evaporative, tactile, osmotic, chemical or electrical; and which cannot be ascribed to any other dental disease.

In dentistry, the hydrodynamic or fluid movement theory is one of three main theories developed to explain dentine hypersensitivity, which is a sharp, transient pain arising from stimuli exposure. It states that different types of stimuli act on exposed dentine, causing increased fluid flow through the dentinal tubules. In response to this movement, mechanoreceptors on the pulp nerves trigger the acute, temporary pain of dentine hypersensitivity.

<span class="mw-page-title-main">Osteomodulin</span> Protein-coding gene in the species Homo sapiens

Osteomodulin is a protein that in humans is encoded by the OMD gene.

Dentin sialophosphoprotein is a precursor protein for other proteins found in the teeth. It is produced by cells (odontoblasts) inside the teeth, and in smaller quantities by bone tissues. It is required for normal hardening (mineralisation) of teeth. During teeth development, it is broken down into three proteins such as dentin sialoprotein (DSP), dentin glycoprotein (DGP), and dentin phosphoprotein (DPP). These proteins become the major non-collagenous components of teeth. Their distribution in the collagen matrix of the forming dentin suggests these proteins play an important role in the regulation of mineral deposition. Additional evidence for this correlation is phenotypically manifested in patients with mutant forms of dentin sialophosphoprotein. Such patients suffer dental anomalies including type III dentinogenesis imperfecta.

Dentin sialoprotein is a protein found in teeth. It is one of the two proteins produced by the segmentation of dentin sialophosphoprotein. Dentin sialoprotein can be found in the dentin immediately subjacent to cellular cementum, but not subjacent to acellular fibrous cementum.

<span class="mw-page-title-main">Pulp stone</span>

Pulp stones are nodular, calcified masses appearing in either or both the coronal and root portion of the pulp organ in teeth. Pulp stones are not painful unless they impinge on nerves.

References

  1. 1 2 Ten Cate's Oral Histology, Nanci, Elsevier, 2013, page 170
  2. 1 2 3 4 Illustrated Dental Embryology, Histology, and Anatomy, Bath-Balogh and Fehrenbach, Elsevier, 2011, page 156
  3. Buchaille R, Couble ML, Magloire H, Bleicher F (September 2000). "A substractive PCR-based cDNA library from human odontoblast cells: identification of novel genes expressed in tooth forming cells". Matrix Biology . 19 (5): 421–30. doi:10.1016/S0945-053X(00)00091-3. PMID   10980418.
  4. Bleicher F, Couble ML, Buchaille R, Farges JC, Magloire H (August 2001). "New genes involved in odontoblast differentiation". Adv. Dent. Res. 15: 30–3. doi:10.1177/08959374010150010701. PMID   12640735. S2CID   38535458.
  5. Maurin JC, Couble ML, Didier-Bazes M, Brisson C, Magloire H, Bleicher F (August 2004). "Expression and localization of reelin in human odontoblasts". Matrix Biology . 23 (5): 277–85. doi:10.1016/j.matbio.2004.06.005. PMID   15464360.
  6. 1 2 Bernal L, et al. (March 2021). "Odontoblast TRPC5 channels signal cold pain in teeth". Science Advances . 7 (13): eabf5567. doi: 10.1126/sciadv.abf5567 . PMC   7997515 . PMID   33771873.
  7. Held, Katharina; Lambrechts, P; Voets, T; Bultynck, G (July 2021). "I scream for ice cream - TRPC5 as cold sensor in teeth". Cell Calcium. 97 (10241): 102419. doi:10.1016/j.ceca.2021.102419. PMID   33993004.
  8. Ohyama, S; Ouchi, T; Kimura, M; Kurashima, R; Yasumatsu, K; Nishida, D; Hitomi, S; Ubaidus, S; Kuroda, H; Ito, S; Takano, M; Ono, K; Mizoguchi, T; Katakura, A; Shibukawa, Y (Dec 2022). "Piezo1-pannexin-1-P2X3 axis in odontoblasts and neurons mediates sensory transduction in dentinal sensitivity". Frontiers in Physiology. 13: 891759. doi: 10.3389/fphys.2022.891759 . PMC   9795215 . PMID   36589456.