Dentin(redirected from dentinum)
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a variety of tooth tissue that makes up the principal mass of the tooth and is also found in placoid scale.
In contrast to other types of bone, the principal matter of dentin does not contain cavities with cells but is penetrated with tubules, in which are located processes called odonto-blasts (Tomes’ fibers), which are on the periphery of the basic matter. This matter consists of a network of collagen fibers, which form a more compact layer around the tubules and an interfibral amorphous substance. The dentin of the teeth of an adult human being contains about 28 percent organic matter, about 64 percent inorganic matter, and about 8 percent water. A variety of dentin is substitute dentin, or vasodentin; it is usually in the teeth and scales of fish. Its basic matter is penetrated with blood capillaries and contains cellular elements; there are no tubules.