1. Anatomy
Every tooth consists of a crown and one or more roots. The crown is the part visible in the mouth and the roots are hidden inside the jaw, the junction of the crown and root is called the neck and the end of the root is the apex

2. Composition of a tooth

3. Enamel
Enamel is the protective outer covering of the crown and is the hardest substance in the body
It is made up of 96% mineral crystals (inorganic) arranged as prisms in an organic matrix called the interprismatic substance
The main mineral crystals are hydroxyapatite

4. The prisms lie at right angles to the junction with the next tooth layer (dentine)
The junction between these two layers is known as the Amelodentinal junction (ADJ)
Enamel is formed before tooth eruption by ameloblast cells which lie at the ADJ

5. It contains no nerves or blood vessels and cannot experience any pain
It can not grow or repair itself so any damage is permanent, it can however remineralise its surface after an acid attack
Can exchange fluoride to form crystals which make the surface harder and more resistant to acid attack
Is translucent in appearance

6. Dentine
Forms the bulk of the tooth and is covered by the enamel in the crown of the tooth and by cementum in the root of the tooth
It consists of upto 80% inorganic tissue, mainly calcium
It is composed of hollow tubes which contain nerve endings called fibrils

7. It is a living tissue so therefore can feel pain
Softer than enamel and has a shock absorbing capability
Dentine is formed by Odontoblast cells and these lie along the the inner edge of the pulp chamber and can produce new dentine as required

8. It can repair itself to an extent by laying down secondary dentine
Secondary dentine also forms as part of a natural ageing process and its formation gradually narrows the pulp chamber
Dentine is a yellowish colour and gives teeth their shade

9. Pulp
The pulp is a soft tissue and is found at the very centre of the tooth in both the crown and root
Contains nerves and blood vessels, it allows the tooth to feel pain sensations
The nerves and blood supply enter the pulp through the apical foramen at the apex of the tooth

10. Cementum
Cementum is the protective outer covering of the root
It meets enamel at the neck of the tooth and lies beneath the gingivae
It allows the attachment of the tooth root to the supporting structure of the periodontal ligament

11. Softer than dentine
Paler than dentine and darkens with age
Formed by cells called cementoblasts

12. Supporting structures
The supporting structures can be found around the roots of the teeth and they hold the teeth in their sockets.
The hold is not rigid, it allows the teeth to have some movement which acts as a shock absorber when pressure is exerted on the teeth by chewing

13. Periodontal ligament
The periodontal ligament is a fibrous tissue that attaches the teeth to the alveolar bone and surrounding gingivae
It acts as a shock absorber to teeth during chewing
Its fibres are made up of a protein called collagen

14. They run in various directions which allows the teeth to move in their sockets
This prevents tooth fracture and pain when forces are exerted on the teeth such as chewing
Inflammation of the ligament is called periodontitus and occurs during periodontal disease

15. Alveolar Bone
The maxilla and mandible both contain a horse shoe shaped ridge of bone called the alveolar process
It is here that teeth form and then from where they erupt into the mouth

16. Is a specialised bone found only in the jaws
The outer layer is made of a hard compact bone called the lamina dura
The inner layer is called cancellous bone and is sponge like in appearance to allow the passage of nerves and blood vessels that supply the jaws, teeth and the surrounding soft tissues

17. The purpose of the alveolar bone is to support the teeth, and when a tooth is extracted the bone gradually resorbs away
The teeth lie in individual sockets in the alveolar bone, each one being lined with the lamina dura
The outer surface of the alveolar bone is covered in specialised alveolar mucosa which forms the gingivae around the necks of the teeth

18. Gingiva
This is the correct term for the gums, it is a specialised soft tissue that is only found in the oral cavity.
It is attached to the alveolar bone as a mucoperiosteal layer of tissue

19. The gingivae fits around the neck of every tooth like a tight cuff this site is called the junctional epithelium
The gingival crevice is a shallow space between the tooth surface and gingival margin
A mound of gingival tissue occurs between each tooth this is called the interdental papilla

20. When healthy the gingivae are firm, pink and have a stippled appearance
Inflammation of the gingivae is called gingivitis caused by plaque, gingivae appears red and swollen and bleeds easily
The gingiva can be forced to overgrow and become hyperplastic due to medication patients may be taking