Dentin
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Parts of a tooth, including dentin |
Dentin (
BE:
dentine) is the substance between the
enamel (substance in the crown) or
cementum (substance in the root) of a
tooth and the
pulp chamber. Dentin is secreted by the
odontoblasts of the
dental pulp. The formation of dentin is known as
dentinogenesis. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water. Because it is softer than enamel, it decays more rapidly and is subject to severe cavities if not properly treated, but dentine still acts as a protective layer and supports the crown of the tooth.
Elephant ivory is solid dentine. The structure of the dentinal tubules contributes both to its
porosity (useful for
piano keys) and its
elasticity (useful for
billiard balls. Elephant tusks are formed with a thin cap of enamel, which soon wears away, leaving the dentine exposed. Exposed dentine in humans causes the symptom of
sensitive teeth.
Dentin is a mineralized
connective tissue with an organic matrix of collagenous proteins. The inorganic component of dentine consists of
dahllite. Dentin has a complex structure. Microscopic channels called
dentinal tubules radiate outward through the dentine from the pulp cavity to the exterior cementum or enamel border. These canals have different configurations in different species and their diameter ranges between 0.8 and 2.2 micrometres. Although they may have tiny side-branches, they do not intersect with each other. Their length is dictated by the radius of the tooth. The three dimensional configuration of the dentinal tubules is under genetic control and is therefore a characteristic unique to the order, although in many mammalian species the tubules follow a gentle
helical course through the solid matrix.
Because dentine is softer than enamel, it wears away more quickly than enamel. Some mammalian teeth exploit this phenomenon, especially
herbivores such as
horses,
deer or
elephants. In many herbivores, the
occlusal (biting) surface of the tooth is composed of alternating areas of dentine and enamel. Differential wearing causes sharp ridges of enamel to be formed on the surface of the tooth (typically a
molar), and to remain during the working life of the tooth. Herbivores grind their molars together as they chew (
masticate), and the ridges help to shred tough plant material.
Dentine may be demineralised and stained for
histological study, unlike enamel. Dentine is approximately 3 on the
Mohs scale of mineral hardness.
A material similar to dentine forms the hard material that makes up
dermal denticles in
sharks and other cartilaginous fish.
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Dentigenix - Dentin Regeneration Technology
