Tooth Anatomy: Enamel, Dentine, Pulp and Root Explained
Tooth anatomy is the structure of a tooth: enamel outside, dentine beneath, the pulp at the centre, and a root held in the jaw by cementum, the periodontal ligament and alveolar bone. This guide explains each part, why dentine can feel sensitive and why lost enamel cannot grow back.
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Clinically reviewed by Dr Ibraheem Ijaz, dentist · GDC 301711
Medical disclaimer: This page is for general information only. It does not replace an examination or treatment by a dentist.
Dr Ibraheem Ijaz, GDC 301711, principal dentist at Deepcar Dental Care, reviewed this page. He is a General Dental Practitioner with a BDS, BSc (Hons), MSc (Leeds) and postgraduate qualifications in implant, restorative and aesthetic dentistry.
What are the parts of a tooth?
A tooth is built from four tissues: enamel over the crown, cementum over the root, dentine forming the bulk and the pulp at its centre. A 2017 review of enamel biology describes this structure.
The root sits in a socket in the jaw. The gum, periodontal ligament, root cementum and alveolar bone form the periodontium, whose main function is to attach the tooth to the jawbone, a standard periodontology textbook explains.
| Part | Where it is | What it does |
|---|---|---|
| Enamel | Outer layer of the crown | Protects the dentine and pulp |
| Dentine | Under the enamel and in the root | Forms most of the tooth |
| Pulp | Centre of the tooth | Holds blood vessels and nerves |
| Cementum | Thin layer over the root | Anchors the ligament fibres |
| Periodontal ligament | Between root and socket | Holds the tooth and spreads biting force |
| Alveolar bone | Jawbone around each socket | Supports the tooth |
What is enamel?
Enamel is the hard outer coating of a tooth's crown and the hardest substance in the human body, a 2017 enamel review explains.
Enamel is a wear-resistant, insulating barrier protecting the dentine and pulp from physical, thermal and chemical forces. Fluoride toothpaste helps prevent and control tooth decay, the NHS says, as explained in how fluoride works.
What is dentine, and why can it feel sensitive?
Dentine is the layer under the enamel that forms most of a tooth, an NHS oral health leaflet explains. By weight it is about 70% mineral, 20% organic matrix and 10% water, a 2011 review of dentine reports.
In tooth anatomy, dentine is crossed by about 18,000 to 21,000 tiny tubules per square millimetre, more numerous nearer the pulp. Into them, the dentine-forming cells, called odontoblasts, extend long processes from the edge of the pulp.
Dentine sensitivity can happen when dentine is exposed, usually near the gum line through gum recession or loss of enamel, and its tubules are open to the pulp. Under the most widely accepted explanation, the hydrodynamic theory, air, cold, sugar or acid move the fluid in the tubules and trigger the pulp's nerves, a 2013 review explains, though the nerve response is not fully understood.
When should you see a dentist about sensitive teeth?
The Oral Health Foundation, a UK oral health charity, advises seeing a dentist if the pain is severe, sensitivity lasts more than a few weeks, only one tooth is affected or the pain comes on suddenly.
The NHS lists sensitive teeth among the causes of tooth pain. It advises seeing a dentist if toothache lasts more than 2 days, does not go away when you take painkillers, comes with a high temperature, pain when you bite, red gums or a bad taste in your mouth, or your cheek or jaw is swollen. If you do not have a dentist or cannot get an emergency appointment, call 111 or visit 111 online.
Go to A&E if you have toothache and the area around your eye or your neck is swollen, or swelling in your mouth or neck is making it difficult to breathe, swallow or speak. Do not drive to A&E: ask someone to drive you or call 999 for an ambulance.
What is the dental pulp?
The dental pulp is the soft, living centre of a tooth, holding connective tissue, blood vessels and nerves, Elsevier's Complete Anatomy explains.
The pulp fills the pulp chamber in the crown and the root canals. Blood vessels and sensory nerves enter it through the apical foramen, a small opening near the apex, the tip of the root. The pulp's outer layer holds the odontoblasts, and a 2017 enamel review calls the pulp the organ that generates and supplies them. The NHS notes that tooth decay can reach the pulp, explained under dental caries.
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What holds a tooth in its socket?
In tooth anatomy, the periodontal ligament holds a tooth in its socket, joining the cementum on the root to the alveolar bone of the jaw.
Cementum is a thin mineralised layer over the root with no blood supply. Its main role is to anchor the ligament's fibres to the root, a 2025 review of cementum explains.
The ligament is mainly collagen fibres, with blood vessels and nerves. It supports the tooth, transmits and disperses biting force, and acts as a mechanoreceptor for muscle activity during chewing, a 2025 ligament review reports.
The alveolar bone proper is the thin plate of bone lining each socket, a periodontology textbook explains. Periodontitis, a chronic inflammatory disease, damages these supporting tissues and can lead to tooth loss, the cementum review notes, as covered in periodontitis and its effect on the bone.
Teeth move under orthodontic load through loss and formation of alveolar bone, though the trigger is debated, a 2014 study notes, as covered in how teeth move. Conventional implants connect directly to bone, a bond called osseointegration, with no periodontal ligament, a 2020 review notes.
Why does enamel not grow back?
Enamel does not grow back because its forming cells, ameloblasts, are lost once the tooth erupts, a 2014 review of enamel regeneration explains.
Formed enamel contains no cells and no collagen, so, unlike bone, it cannot remodel, a 2017 enamel review adds. It can regain some minerals: the UK prevention toolkit Delivering Better Oral Health says early tooth decay can be reversed. When mineral loss outweighs repair, decay progresses, unless checked, into the dentine until a cavity forms. The toolkit names two levers: less sugar, covered in diet and tooth decay, and fluoride.
Dentine is different. Once a tooth meets its opposing teeth, odontoblasts lay down secondary dentine throughout life, and tertiary dentine forms in reaction to decay or abrasion, a 2011 dentine review explains. Neither replaces lost enamel.
Why does tooth anatomy matter for dental care?
Tooth anatomy matters because lost enamel does not regrow, and the ligament and bone hold each tooth in place.
Lost enamel is replaced with artificial materials, and none yet matches every property of natural enamel, a 2014 enamel review notes. Saving natural teeth by repairing and rebuilding damaged teeth is covered separately. Whitening peroxide is thought to diffuse through enamel and lighten coloured compounds, particularly in the dentine, a 2006 review explains, as described in how teeth whitening works.
The NHS advises regular dental check-ups even if you have no problems. That routine, ongoing care is general dentistry, and our guide to routine dental care explains each visit.
Frequently asked questions
How many teeth does an adult have?
A full adult set is 32 teeth, an NHS oral health leaflet explains. That is 8 incisors, 4 canines, 8 premolars and 12 molars, wisdom teeth included. Adult teeth begin to come through at around 6. Wisdom teeth usually start coming through in the teens or early 20s, the NHS says.
How are baby teeth different from adult teeth?
There are fewer of them, and none are premolars. An NHS oral health leaflet lists 20 baby teeth: 8 incisors, 4 canines and 8 molars. Most children have them all by 2 to 3 years old, the NHS says. Decay in baby teeth is covered in tooth decay in children.
What is enamel made of?
Mature enamel is about 95% mineral by weight, with 1 to 2% organic material and 2 to 4% water, a 2017 review reports. The mineral is a calcium phosphate based on hydroxyapatite, and calcium makes up about 36% of enamel by weight.
What is the difference between the crown and the root?
The crown is the enamel-covered part of a tooth, and the root is the cementum-covered part that sits in the jaw socket. Both are mainly dentine around the pulp, and the root also contains the root canal, through which nerves and blood vessels reach the pulp.
Is dentine the same as bone?
No, although the two are related. Both are mineralised tissues formed by cells of mesenchymal origin, and dentine has a large collagen component, a 2017 review notes. Unlike bone, dentine has no blood vessels and is more highly mineralised, a 2011 dentine review explains.
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