Dental anatomy is the study of the structure, development, and function of the teeth and their supporting structures, including the gums, jaws, and surrounding tissues. It involves understanding the different parts of the teeth, such as the enamel, dentin, pulp, and roots, as well as the various types of teeth found in the mouth, such as incisors, canines, premolars, and molars.
The tooth is a hard, calcified structure found in the jaws of many vertebrates, including humans. It is used for biting, tearing, and grinding food, and plays an important role in the digestive process. Also, they help us smile and talk.
The tooth is one of the most individual and complex anatomical as well as histological structures in the body. There are two sets of teeth. The first set is known as baby, milk, primary, or deciduous teeth. The primary teeth start to erupt at about 6 months of age. These teeth are later replaced by the permanent teeth (the 2nd set).
Tooth structure
Each tooth consists of 3 anatomical parts: the crown, neck, and root.
The crown of a tooth is the part of the tooth that is visible above the gumline. It is the part of the tooth that is responsible for biting, chewing, and grinding food. The shape and size of the crown vary depending on the type of tooth and its function in the mouth.
The neck, also known as the cervix, is the area where the crown joins the root. The neck is surrounded by gingiva (gum).
The root of a tooth is the part of the tooth that is below the gum line and anchors the tooth into the jawbone.
Tooth Layers
The tooth is made of several layers of varying density and hardness: the enamel, dentin, cementum, and pulp.
Enamel is the hard, outer layer of a tooth that covers the crown of the tooth.
Tooth enamel is the most resistant and hardest tissue in the human body. Enamel is formed during tooth development and does not contain any living cells, which means it cannot regenerate or repair itself once it is damaged. It consists of 95% inorganic substance (mainly calcium and phosphate in the form of hydroxyapatite), 1% organic substance, and 4% water. The fluoride increases the hardness of tooth enamel by converting the hydroxyapatite crystals to fluorapatite. So, fluoride toothpaste can increase the strength of enamel. In contrast, acid can damage the enamel by detaching calcium and phosphate, causing dental caries. The tooth enamel is exposed to 2 processes:
1) Remineralization: when the oral pH rises, the enamel restores minerals (calcium and phosphate) from saliva, reversing the early stage of dental caries.
2) Demineralization: when oral bacteria decompose carbohydrates in food debris and produce acid, the oral pH drops below 5.5, when the normal pH of the oral cavity is between 6.2 and 7.0. The bacterial acid dissolves the enamel surface, which leads to the loss of calcium and phosphate ions, causing early stage of dental caries. This is known as “demineralization”.
The dentin is the second layer of the tooth, after the enamel. It is the largest part of tooth structure, surrounding the pulp. Dentin is formed by specialized cells called odontoblasts, which are located at the outer surface of the pulp. Odontoblasts secrete a mineralized matrix that eventually hardens to form dentin. Dentin is yellowish in color and contains microscopic channels called dentinal tubules that extend from the pulp to the outer surface of the tooth. Unlike enamel, dentin can regenerate to a limited extent in response to injury or decay. It is softer and less dense than enamel and therefore is more susceptible to caries, but is harder and denser than bone. The dentin is sensitive to heat, cold, and touch, which appears as pain sensation.
The cementum is a calcified substance that covers the root. It attaches the tooth to the alveolar bone. It is yellowish in color and softer than both enamel and dentin. Cementum is formed by specialized cells called cementoblasts, which are located in the root of the tooth. Cementoblasts secrete a mineralized matrix that eventually hardens to form cementum. Cementum also contains microscopic channels that allow for the exchange of nutrients and waste between the tooth and the surrounding tissue. Cementum plays an important role in maintaining the health of the tooth and the surrounding periodontal tissues. It helps to protect the underlying dentin and root from decay and mechanical damage, and provides a surface for the periodontal ligaments to attach to.
The dental pulp, also known as the pulp chamber, is a soft, connective tissue located in the center of a tooth that contains nerve tissues and blood vessels that nourish the tooth. These nerve tissues and blood vessels are extending from the jaw bone to the pulp through a small hole (Apical foramen) at the root tip. The dental pulp plays an important role in the growth, development, and maintenance of a tooth. It is responsible for the formation and development of the dentin and other tooth structures during tooth development.
Periodontal ligament (PDL), also known as periodontal fibers. It is connective tissue fibers in the small gap between the cementum and the jaw bone. The periodontal ligament provides an attachment of the tooth to the jaw bone. Also, it has a supporting, nutritive, sensory, and remodeling function.
The alveolar bone supports teeth and is covered by the gingiva. It’s well supported with blood and subjected to continuous modification.
The pressure during mastication is transmitted to the bone and stimulates its modification which makes the bone stronger.
When there is no pressure on the bone because of tooth loss, the bone recedes.
Bone loss may make it difficult to anchor a dental implant or hold a denture.
Types of Teeth and Their Functions
There are four main types of teeth in the human mouth, each with a specific function:
Incisors: they are in the front area of the upper and lower jaw (4 in each arch). Incisors are sharp and allow food biting and cutting.
Canines: they are located directly after the incisors. There are four canines in the human mouth, two on the upper jaw and two on the lower jaw. Canines are conical-shaped. They hold food during biting to facilitate the cutting of food.
Premolars and molars: they are located behind canines. They have a wide and flat surface (occlusal surface) with several cusps. They crush food between the occlusal surfaces of upper and lower premolars and molars to make food swallowing and digestion easier.
Comments