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Dentin is classified into three types: primary, secondary, and tertiary. [24] [25] Secondary dentin is a layer of dentin formed after the tooth's root has fully formed. Tertiary dentin develops as a result of a stimulus, such as a carious attack or wear. [26]
Tertiary dentin on the surface of a gorilla tooth. The darker area indicated by the white arrow is tertiary dentin and has formed as a response to tooth wear. Wear on the surface of a tooth can lead to the exposure of the underlying dentin. When wear is severe tertiary dentin may form to help protect the pulp chamber. [4]
There are three types of dentin, primary, secondary and tertiary. [19] 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. [20]
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary ...
Reactionary dentin is formed by odontoblasts when the injury does not damage the odontoblast layer. Reparative dentin is formed by replacement odontoblasts when the injury is so severe that it damages a part of the primary odontoblast layer. Thus a type of tertiary dentin forms in reaction to stimuli, such as attrition or dental caries.
As more tertiary dentin is produced, the size of the pulp decreases. This type of dentin has been subdivided according to the presence or absence of the original odontoblasts. [85] If the odontoblasts survive long enough to react to the dental caries, then the dentin produced is called "reactionary" dentin. If the odontoblasts are killed, the ...
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 ...
The lungs can be included in the lower respiratory tract or as separate entity and include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. [3] Adult and pediatric airway anatomy. The respiratory tract can also be divided into a conducting zone and a respiratory zone, based on the distinction of transporting gases or ...