Teeth and Their Parts
- Each tooth has two main parts, the crown and the root.
- The crown and the root meet at the neck of the tooth, which is normally just below the gum margin.
- The crown
This is the part of the tooth that we see in the mouth.
It is made up of the enamel, dentine and pulp.
The appearance of teeth varies in shape and size.
- The front incisor teeth have a straight edge as a cutting tool.
- The canine or eye teeth are the pointed long teeth between the incisor and premolar teeth.
- The pre-molar and molar teeth are larger and have cusps.
- A cusp is the raised pointed part of the chewing surface of a tooth.
- The presence of large cusps on pre-molar and molar teeth marks the main difference between them and the front teeth.
- Pre-molar teeth (bicuspids) have two cusps.
- Molar teeth each have four or more cusps.
- The four permanent lower incisor teeth each erupt with three small cuspettes that resemble a serrated edge. These cusps wear down with use and the teeth remain with a straight edge.
- The four permanent upper incisors may erupt with three very small cuspettes. These are much less obvious than those on the lower incisors. They are also normally worn away to form a straight edge.
- The enamel is the white hard covering over the crown of the tooth.
- It is shaped into cusps, fissures and pits in premolar and molar teeth.
- It is the hardest material in the body and does not have a nerve supply.
Chipping or damage to enamel only will not be painful.
- It also does not have a blood supply.
This results in a chipped tooth remaining exactly as it is.
Enamel cannot heal or repair as bone or dentine can.
- Dentin is a cream coloured hard material that makes up the bulk of the tooth.
- It is covered by enamel on the crown, and by cementum on the roots.
- The dentine surrounds and protects the nerves and blood vessels (pulp) in the crown and roots.
- Dentine is alive or vitalin as much as more dentine can be formed, and it can register pain.
- A protective layer of secondary dentine can be layed down over the pulp.
- This happens in response to caries, attrition, abrasion, erosion, or fracture of a tooth, when the dentine becomes exposed.
- The tooth becomes sensitive to temperature changes and feels painful, when the dentine is exposed in the above mentioned ways.
The nerves and blood vessels of the tooth are called the pulp.
- The roots
The roots are embedded in the tooth socketin the jaw bone.
- The front incisor and eye-teeth each have a single root.
- Pre-molar teeth (bicuspids) have one or two roots.
- The molar teeth can have two or three roots.
- Each root has a root canal for the nerves and blood vessels to pass through.
- Roots are covered by cementum and held in place by the periodontal ligament.
- The cementum is a thin calcified covering of the roots.
- It meets the enamel at the neck of the tooth.
- It has no nerve supply.
- The cementum covers the dentine of the roots.
- It is attached to the periodontal ligament.
- Periodontal membrane or ligament
The periodontal ligament attaches the roots to the alveolar boneof the jaw.
- It has both a nerve and blood supply
- The ligament provides an elastic cushion between the tooth and the bone. Slight movement of a tooth is made possible by the ligament.
- Teeth are not rigidly joined to bone. There is flexibility.