Dentin
Dentinum
Also known as: dentine
Dentin is the yellowish, bone-like calcified tissue that forms most of the tooth. It is penetrated by microscopic tubules containing the processes of odontoblasts.
Overview
Dentin is about 70% mineral (hydroxyapatite), about 20% organic matter (mostly type I collagen) and about 10% water. It is softer and more elastic than enamel and supports the brittle enamel above it. Odontoblasts line the pulp, and each sends a process (Tomes fibre) into a dentinal tubule that crosses the full thickness of the dentin. This makes dentin a living, sensitive tissue.
Primary dentin forms before root completion. Secondary dentin is laid down slowly throughout life, so the pulp chamber shrinks with age. Tertiary (reparative) dentin forms locally under caries, wear or cavity preparation as a defensive barrier.
- Location
Between the enamel (crown) or cementum (root) and the pulp cavity.
Anatomy
- Histology
Tubular dentin with peritubular and intertubular matrix. A layer of unmineralised predentin lies next to the odontoblasts.
Function
- Forms the main body and shape of the tooth.
- Cushions and supports the enamel.
- Transmits stimuli to the pulp; tubule fluid movement causes pain.
- Physiology
By the hydrodynamic theory, stimuli such as cold, air or sweet foods move fluid within exposed dentinal tubules. This deforms nerve endings at the pulp–dentin border and produces sharp pain (dentine hypersensitivity).
Clinical significance
Dentine hypersensitivity and dentinogenesis imperfecta
Gingival recession or enamel loss exposes the tubules and causes sharp pain with cold. Dentinogenesis imperfecta gives opalescent, fragile teeth; one form accompanies osteogenesis imperfecta (a type I collagen defect).
Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.