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The dentinoenamel junction or dentin-enamel junction (DEJ) [1] is the boundary between the enamel and the underlying dentin that form the solid architecture of a tooth. It is also known as the amelo - dentinal junction, [ 2 ] or ADJ.
Enamel-dentin fracture A fracture is confined to enamel and dentin with loss of tooth structure, but exposing the pulp; Not tender upon percussion test; If tenderness is observed, evaluate the tooth for possible luxation or root fracture injury; Normal mobility; Sensibility pulp test is usually positive; Enamel-dentin loss is visible
Cross-sectional diagram of a molar tooth. 1: crown, 2: root, 3: enamel, 4: dentin and dentin tubules, 5: pulp chamber, 6: blood vessels and nerve within root canal, 7: periodontal ligament, 8: apex and periapical region, 9: alveolar bone VITA classical A1-D4 shade guide arranged according to value VITA classical A1-D4 shade guide arranged according to chroma; A: red-brown, B: red-yellow, C ...
Tooth development begins at week 6 in utero, in the oral epithelium. The process is divided into three stages: Initiation; Morphogenesis and; Histogenesis [2]; At the end of week 7 i.u., localised proliferations of cells in the dental laminae form round and oval swellings known as tooth buds, which will eventually develop into mesenchymal cells and surround the enamel organ.
In permanent teeth, the enamel rods near the cementoenamel junction (CEJ) tilt slightly toward the root of the tooth. Understanding enamel orientation is very important in restorative dentistry, because enamel unsupported by underlying dentin is prone to fracture. [10] The area around the enamel rod is known as interrod enamel.
Enamel spindles are often confused with two other entities: enamel lamellae and enamel tufts. Lamellae are linear enamel defects that extend from the surface of the enamel towards the DEJ, or vice versa. Enamel tufts are "small, branching defects that are found only at the DEJ, protruding into the enamel towards the enamel surface.
Enamel tufts do not normally lead to enamel failure, due to these defects stabilizing potential fractures. The processes involved include the creation of stress shielding by increasing the compliance of enamel next to the dentin. [8] Decussation is another factor by which cracks form wavy stepwise extensions that arrest their further development.
Cross-section of a tooth. B is dentin. Dentin (/ ˈ d ɛ n t ɪ n / DEN-tin) (American English) or dentine (/ ˈ d ɛ n ˌ t iː n / DEN-teen or / ˌ d ɛ n ˈ t iː n / DEN-TEEN) (British English) (Latin: substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth.