Teeth anatomy.

Teeth anatomy.

Teeth anatomy is a field of anatomy dedicated to the study of tooth structure. 

Enamel:

Enamel is the hardest and most highly mineralized substance of the body. It has its origin from oral ectoderm. It is one of the four major tissues which make up the tooth, along with dentin, cementum, and dental pulp. It is normally visible and must be supported by underlying dentin. 96% of enamel consists of mineral, with water and organic material comprising the rest. The normal color of enamel varies from light yellow to grayish white. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue tone. Since enamel is semitranslucent, the color of dentin and any restorative dental material underneath the enamel strongly affects the appearance of a tooth. Enamel varies in thickness over the surface of the tooth and is often thickest at the cusp, up to 2.5mm, and thinnest at its border, which is seen clinically as the CEJ. The wear rate of enamel, called attrition, is 8 micrometers a year from normal factors.

Enamel's primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. The large amount of minerals in enamel accounts not only for its strength but also for its brittleness. Dentin, which is less mineralized and less brittle, compensates for enamel and is necessary as a support. Unlike dentin and bone, enamel does not contain collagen. Proteins of note in the development of enamel are ameloblastins, amelogenins, enamelins and tuftelins. It is believed that they aid in the development of enamel by serving as framework support, among other functions. In rare circumstances enamel can fail to form, leaving the underlying dentine exposed on the surface.

Enamel plays a very important role in protecting your teeth from decay, so it is important to do everything that you can to prevent your enamel from eroding. It forms a strong barrier that protects the inner layers of your teeth from the effects of acids and plaque; it also protects the sensitive inner layers of your teeth from foods and beverages that are very hot or very cold.

Dentin:

Dentin is a calcified tissue of the body.  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 hydroxylapatite, 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.  Dentin is the substance between enamel or cementum and the pulp chamber. It is secreted by the odontoblasts of the dental pulp. 

The formation of dentin is known as dentinogenesis. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight. Because it is softer than enamel, it decays more rapidly and is subject to severe cavities if not properly treated, but dentin still acts as a protective layer and supports the crown of the tooth.  

Dentin is a mineralized connective tissue with an organic matrix of collagenous proteins. Dentin has microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp cavity to the exterior cementum or enamel border. The diameter of these tubules range from 2.5 μm near the pulp, to 1.2 μm in the midportion, and 900 nm near the dentino-enamel junction. Although they may have tiny side-branches, the tubules do not intersect with each other. Their length is dictated by the radius of the tooth. The three dimensional configuration of the dentinal tubules is genetically determined.   

There are three types of dentin, primary, secondary and tertiary. Secondary dentin is a layer of dentin produced after root formation and continues to form with age. Tertiary dentin is created in response to stimulus, such as cavities and tooth wear.  Another way in which dentin is different than enamel is that it is living tissue with the ability for constant growth and repair. 

Tiny dentinal tubules that run between the cementoenamel junction (the interface of crown enamel and the tooth root cementum) and the pulp layer beneath it assist in this regeneration process. Cell processes in the pulp layer reach into the tubules, creating new dentin and mineralizing it. Nerves also pass through these dentinal tubules allowing dentin to transmit pain, unlike enamel.

Cementum:

Cementum is a specialized bone like substance covering the root of a tooth. It is approximately 45% inorganic material (mainly hydroxyapatite), 33% organic material (mainly collagen) and 22% water. Cementum is excreted by cementoblasts within the root of the tooth and is thickest at the root apex. Its coloration is yellowish and it is softer than dentin and enamel. The principal role of cementum is to serve as a medium by which the periodontal ligaments can attach to the tooth for stability. At the cement to enamel junction, the cementum is acellular due to its lack of cellular components, and this acellular type covers at least ⅔ of the root. The more permeable form of cementum, cellular cementum, covers about ⅓ of the root apex.

Dental pulp:

The dental pulp or pulp chamber.

The dental pulp is the soft area within the center of the tooth and contains the nerve, blood vessels, and connective tissue. The tooth's nerve is in the "root" or "legs" of the tooth. The root canals travel from the tip of the tooth's root into the pulp chamber.

The dental pulp is the central part of the tooth filled with soft connective tissue.  This tissue contains blood vessels and nerves that enter the tooth from a hole at the apex of the root. Along the border between the dentin and the pulp are odontoblasts, which initiate the formation of dentin. Other cells in the pulp include fibroblasts, preodontoblasts, macrophages and T lymphocytes. The pulp is commonly called "the nerve" of the tooth.

The pulp is the part in the center of a tooth made up of living connective tissue and cells called odontoblasts. The pulp is a part of the dentin–pulp complex (endodontium). The vitality of the dentin-pulp complex, both during health and after injury, depends on pulp cell activity and the signaling processes that regulate the cell's behavior.

The pulp is the neurovascular bundle central to each tooth, permanent or primary. It comprises a central pulp chamber, pulp horns, and radicular canals. The large mass of pulp is contained within the pulp chamber, which is contained in and mimics the overall shape of the crown of the tooth. Because of the continuous deposition of dentine, the pulp chamber becomes smaller with age. This is not uniform throughout the coronal pulp but progresses faster on the floor than on the roof or side walls.

Radicular pulp canals extend down from the cervical region of the crown to the root apex. They are not always straight but vary in shape, size, and number. They are continuous with the periapical tissues through the apical foramen or foramina.

The total volumes of all the permanent teeth organs is 0.38cc and the mean volume of a single adult human pulp is 0.02cc.

Accessory canals are pathways from the radicular pulp, extending laterally through the dentin to the periodontal tissue seen especially in the apical third of the root. Accessory canals are also called lateral canals because they are usually located on the lateral surface of the roots of the teeth.

Read more: Human tooth, maxilla.