Parts of the Teeth – It is very important for every person associated with the work of Dental Office to be familiar with the physiology of a tooth as well as the function of each part of the tooth. Three main parts make up a tooth—the crown, the cervix, and the root.
Parts of the Teeth – THE CROWN
The crown is the Parts of the Teeth that is utilized for mastication and is visible in the oral cavity. The dental crown can be divided into two Parts of the Teeth—the anatomical crown and the clinical crown.
The anatomical crown is the part of the tooth that extends from the incisal or coronal surface to the cervical neck (the cementoenamel junction). It is the part entirely covered by enamel. The cementoenamel junction is formed by the line where the enamel of the crown and cementum of the root meet. Another name for this is the cervical line.
The clinical crown is one of the Parts of the Teeth from the incisal edge to the crest of the gingival height. The clinical crown is the part you see above the gum line. The clinical crown height can be greater than the anatomical crown height because of periodontal disease, or it can vary with age. Gingival recession can cause exposure of the root, adding length to the clinical crown.
Parts of the Teeth – THE CERVIX
The cervix, or neck, is one of the Parts of the Teeth where the anatomic crown meets the anatomic root. This part of the tooth is also referred to as the cementoenamel junction.
Parts of the Teeth – THE ROOT
The root of the tooth is the part that supports the crown and is usually below the gingiva. This section of the tooth is contained within the bony structures of the supporting maxilla and mandible. The root can be divided into two categories— the anatomic root and the clinical root.
The anatomic root is the area from the cervix to the apex (the end of the root) Parts of the Teeth. It is covered with cementum.
The clinical root is the distance from the crestal height of the alveolar bone to the apex of the tooth.
Parts of the Teeth – The Apex
The apex of a tooth is located at the tip of the root. At the end of the root is a small opening— the apical foramen. The function of this tiny opening is to “feed” the tooth. The opening allows blood vessels to carry nourishment to a tooth. A second function of the apical foramen is to allow the entrance of nerves to the tooth. This process is known as innervation of the tooth.
COMPOSITION OF THE TEETH
A tooth consists of three hard tissue which are Parts of the Teeth, the enamel, dentin and cementum, surrounding a soft tissue— the pulp. The pulp is surrounded by dentin on all sides except at the apical foramen, where it is continuous with the periodontal soft tissue.
Parts of the Teeth – Enamel
Enamel is the hardest tissue of the entire human body. It is a calcified matrix, which covers the entire anatomical crown of the tooth and protects the dentin (the inner portion of the tooth). It is formed by epithelial cells. It is made up of 96 percent inorganic (calcium and phosphorous) and four percent organic (carbon compounds) material. Another purpose of enamel is to protect the Parts of the Teeth, which is exposed to the oral cavity during mastication. When enamel is mature, no further growth or repair takes place.
Parts of the Teeth – Cementum
Cementum is a very dense tissue and one of the Parts of the Teeth that covers the clinical root of a tooth. It is composed of approximately 55 percent inorganic material (mainly calcium salts) and 45 percent organic material (mainly collagen). Cementum is of light yellow color and regenerates by forming new layers over older ones. The cementum covers the clinical root and meets the clinical crown at the cementoenamel junction. Sometimes, the cementum and enamel do not meet in a perfect juncture, forming a space which can be sensitive to external stimuli such as heat, cold, chemicals, sweetness, or mechanical stimuli.
The primary function of cementum is to anchor a tooth to the bony wall of the socket. Cementum is formed throughout the life of a tooth. When a fracture of the tooth root takes place, the new cementum formed may replace the lost tissue, helping to repair it. Two types of cementum are usually recognized—primary and secondary.
Parts of the Teeth – Dentin
Dentin, which is one of the Parts of the Teeth, is the material that makes up the hard structure of a tooth. Dentin is harder than bone but softer than enamel. It is covered by the cementum in the root area and enamel in the crown area. The majority of dentin is composed of inorganic materials (70 percent), mainly calcium. The remaining 30 percent is organic material. Dentin is continually formed throughout the life of the tooth. It forms from the outside of a tooth near the enamel and grows inwards towards the pulp. One of the main functions of dentin is pupal protection. If, for example, the dentin is irritated by bacterial decay, cavity preparation, or wearing away, it changes formation and try to do the repair work by formation of Secondary or Reparative Dentin.
The dentin thus formed develops in layer called the irregular secondary dentin next to the pupal wall. This dentin is dense and actually forms a layer of insulation over the pulp. An irregular dentin usually forms when severe trauma, such as a deep fracture, is experienced. Dentin continues to develop throughout the life of the tooth. It continues to thicken during this time and eventually invades the pupal chamber. This growth will cause a decrease in the size of the pupal chamber later in a person’s life.
Parts of the Teeth – Pulp
The pulp is the lifeline of the tooth. The soft tissue of the pulp is found within the hard structures that forms one of the Parts of the Teeth. The area that houses the pulp in the coronal (crown) section is called the pulp chamber The area in the root of a tooth that houses the pulp is called the root canal. Finally, the section at the root apex where the pulpal material enters a tooth is called the apical foramen. The pulp is composed mainly of loose connective tissue, blood vessels, and nerve materials. Its function can be divided into the following four categories:
(A) Formation. The external portion of the pulp chamber is lined by odontoblasts (dentin-forming cells). The function of these odontoblasts is in the formation of dentin. The chief function of pulp is to make dentin. The odontoblasts appear as a layer of cells between the pulp and the dentin and are actually part of the pulp.
(B) Nutrition. The pulp supplies the tooth with nutrients necessary for the organic portion of the tooth. It also supplies moisture for the tooth to prevent its desiccation (drying).
(C) Sensation. The pulp has a very extensive nerve supply. Whenever an external stimulus traumatizes a tooth, the pain is transmitted by the nerves and alerts the brain to the presence of a toothache.
(D) Defense. One of the main functions of the pulp is in the formation of secondary dentin for protection whenever an external stimulus causes a pupal reaction. Along with this, the blood supply will form defense cells such as macrophages and fibrocytes for the protection of the tooth.