Classification of dentin, dentin and cementum are derived from

According to the shape and use, the plate teeth are divided into round plate teeth, square plate teeth (square plate teeth), hexagonal plate teeth (hexagonal plate teeth), and tubes. Plate teeth, shaped plate teeth and tube plate teeth. Among them, the round plate tooth is widely used, and the specification range is millimeters.

Round plate tooth and hexagonal plate tooth countries have national standards, but the hardware market can generally only buy round plate teeth, it is difficult to buy hexagonal plate teeth, let alone square plate teeth. Since there is no national standard for the square teeth (Fig. 1), there are fewer manufacturers and the appearance is not the same. However, square teeth are very useful in the repair and installation of machinery and equipment.

For example, when installing the machine tool, the thread of the anchor bolt is often easy to be damaged, and the general unit only has a round plate tooth, and the round plate tooth must have a plate tooth frame to thread the wire, and the plate tooth frame is very large, and it occupies space, and the machine tool can not thread at the footing. At this time, just put the round plate teeth in the sand....

Answer]: B. External mesenchymal can develop into periodontal tissues such as dentin, cementum, pulp, and periodontal ligament. Therefore, dentin and cementum ** are in mesenchymal Zen Zheng cells. Bridge Hall.

Answer]: The formation of dentin is an orderly process, i.e., the formation of the dentin is not aware of the secretion of the matrix by the cells and further mineralization. Because the tooth is formed throughout the life of the chain, there is always an organic matrix between the odontoblast cell layer and the mineralized dentin.

Only E can be selected for this question.

How teeth are classified.

Teeth are first divided into deciduous teeth and permanent teeth Deciduous teeth are generally replaced around the age of twelve, and are called permanent teeth alternately Deciduous teeth are divided into deciduous incisors, deciduous lateral incisors, deciduous canines and deciduous molars, and deciduous teeth are those without bicuspids Permanent teeth are divided into incisors, lateral incisors, canines, bicuspids (premolars) and molars Incisors to canines are called anterior teeth, and later called posterior teeth Incisors, lateral incisors, and four upper and lower canines A total of eight bicuspids Molars are also However, people also have a kind of tooth called wisdom teeth, but not everyone has them, and the number varies from 1 to 4, Rare with more than 5 If there is a problem with differentiation during human development, then the number of teeth may increase or decrease, and the extra teeth that are added are called supernumerary teeth, and the decrease is called congenital deletion.

What is the classification and function of teeth?

Teeth are divided into four categories: incisors, canines, bicuspids, and molars.

The incisors are located in the front part of the oral cavity, with a total of 8 left, right, upper and lower teeth, and the adjacent crown is wedge-shaped, with a thick neck and thin incision margin, which is a single root; Canine teeth, commonly known as canines, are located at the corners of the mouth, with a total of 4 left, right, upper and lower, the crown is still wedge-shaped, and there is a prominent cusp on the incision; Bicuspids, also known as premolars, are located behind the canines and before the molars, with a total of 8 left, right, upper and lower crowns, and a occlusal surface; The molars are located behind the bicuspids, with a total of 12 left, right, upper and lower crowns, large crowns, cubic shapes, and a wide occlusal surface. In general, the incisors are like knives used to cut food; Fangs have sharp cusps that are used to pierce and tear food; Teeth grinding is like a grinding disc used to grind food.

Categories: Medical & Health >> ENT.

Analysis: How teeth are classified.

In terms of the appearance of the teeth, the teeth are composed of three parts: the crown, the root and the neck. The crown is the part of the outer layer of the tooth that is covered by enamel and is the main part that performs the masticatory function. The root is the part of the outer layer of the tooth that is covered by the cementum and is also the supporting part of the tooth; Some teeth have a single root, some have multiple teeth, and the tip of each root is called the apex; Each apex has a small hole through the pulp vascular nerve called the apical foramen; Normally, the root of the tooth is completely embedded in the alveolar bone.

The junction between the crown and the root of the tooth is in an arc-shaped curve, called the neck, also known as the neck margin or neckline.

From the cross-section of the tooth, the tooth body is composed of four layers: enamel, cementum, dentin and pulp. Tooth enamel forms the surface layer of the crown and is a translucent white hard tissue, the hardest tissue that is highly calcified in the tooth tissue. Cementum is the yellowish hard tissue that forms the surface of the tooth root.

Dentin forms the main body of the tooth and is located in the inner layer of the enamel and cementum, which is not as hard as the enamel, and there is a cavity in it called the pulp cavity. The pulp is a honeycomb that fills the pulp cavity and contains blood vessels, nerves, and lymph. It is the only soft tissue in the tooth tissue.

According to the morphological characteristics and functional characteristics of teeth, teeth are divided into four categories: incisors, canines, bicuspids, and molars. The incisors are located in the front of the oral cavity, with a total of 8 left, right, upper and lower teeth, and the crown of the adjacent tooth is wedge-shaped, with a thick neck and thin incision margin, and its main function is to cut off food, which is a single root. The canine teeth, commonly known as canines, are located at the corners of the mouth, with a total of 4 left, right, upper and lower, the crown is still wedge-shaped, and there is a protruding cusp on the incisal margin, the main function is to puncture and tear food, and it is a single root that grows up stout and grows.

Bicuspid teeth, also known as premolars, are located behind the canines and before the molars, with a total of 8 left, right, upper and lower, the crown is cubic, there is a occlusal surface, there are generally double cusps on it, and the second bicuspid of the lower jaw has three cusps, the main function is to assist the canines to tear food and assist the grinding teeth to crush food, the tooth root is flattened, and there are also bifurcated people. Molars are located behind the bicuspids, left, right, upper and lower, a total of 12, the crown is large, cubic, there is a wide occlusal surface, there are 4 5 cusps on it, the main function is to grind food, generally the maxillary molars are three, and the mandibular molars are double.

Teeth are divided into baby teeth and permanent teeth based on how long they have been present in the mouth. Baby teeth begin to erupt in 7 or 8 months after birth, and all the baby teeth erupt around the age of 20 to years, and the baby teeth gradually fall out and are replaced by permanent teeth, which is called the replacement period or mixed dentition. Therefore, the time of baby teeth in the oral cavity is 5 to 10 years.

Around the age of the deciduous teeth, the occlusion period is the period. Permanent teeth are the second set of dentition after the loss of baby teeth, which will not fall out unless due to disease or accidental injury, and there is no tooth to erupt and replace after loss. The first permanent molars begin to develop from the embryo in April and begin to erupt at the age of 6 years, and are the first permanent teeth to erupt and do not replace any baby teeth.

12 After the age of 13, all the baby teeth fall out, which is called the occlusion period of permanent teeth.