Along with the jaws and jaw muscles, the teeth are structures that make chewing of food possible. Since they have to cut, grind, crush and mix all textures of food, teeth often have to withstand forces of up to 150 to 200 pounds. Tooth enamel, cementum, dentin and dental pulp are all parts of teeth that confer great strength, equal to or more than that of bone, on these tiny grinding machines.
Dental Anatomy – Parts of Teeth
Every tooth has two recognizable parts, the root and the crown. While the crown is the visible part projecting outside the gums, the root is the portion that anchors the tooth to its bony socket in the jaw bone. The upper surface of the crown has facets that help teeth of the upper jaw fit with those on the lower jaw when the mouth is closed.
But every tooth has functional parts that give it strength, resistance and protection. The parts of a tooth are:
- Dental pulp
- Dentin
- Cementum
- Dental enamel
Tooth Anatomy – Dental Pulp
The dental pulp is at the core of every tooth. This is where the nerves and blood vessels that nourish the tooth lie. The pulp is lined by teeth cells called odontoblasts that produce the substance of the dentin layer. With time, these cells invade more and more of the pulp space, reducing its size till the dentin layer stops growing.
Tooth Morphology – Dentin
Dentin lies immediately outside the pulp of the tooth and forms the bulk of the tooth. It is the layer that gives teeth the strength of bone. This is because dentin is mainly composed of hydroxyapatite crystals which are really bone salts made of calcium and phosphate, but more densely packed together than in bone.
In the dentin layer, these hydroxyapatite crystals are embedded in a matrix of collagen fibres, protein fibres that provide tensional strength to tissues. These features make the dentin very similar to bone in composition.
Tooth Structure – Cementum
Cementum forms the layer outside the dentin layer in the region of the root. It is again very similar to bone and forms the bridge between the root of the tooth and its bony socket. Cementum is secreted by the periodontal membrane, the membrane that lines the socket.
With age and use, the layer of cementum gains in thickness and strength, anchoring the teeth more firmly in their bony sockets.
Dental Anatomy – Tooth Enamel
Dental enamel is the outermost layer of the teeth covering the crown region. Enamel is secreted by special tooth cells called ameloblasts before eruption and is not produced after the tooth erupts. Enamel is made of hydroxyapatite crystals which, alongwith ions like caronates, magnesium and potassium, are embedded in a strong matrix of insoluble protein fibres.
Tooth enamel is the strongest part of the tooth. The insoluble protein it contains helps the tooth resist the corrosive activity of acids and enzymes and protects it from dental caries.
With dental enamel, cementum, dentin and dental pulp, tooth morphology is well designed for strength and resistance.
Sources:
Arthur C. Guyton, John E. Hall; Textbook of Medical Physiology, 11th Edition; Elsevier; ISBN:978-0-7216-0240-0
Lakshmi Ananth - Lakshmi Ananth is a practising ENT, head and neck surgeon and has faculty position at a medical college. She is specially interested in ...
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