Only lower jaw is movable. Upper jaw is fused to skull.

Chewing by cheek muscles which move lower jaw up and down, allow some side-to-side movement.

• Four types of teeth

1. incisors (4)

2. canines (2)

3. premolars (4)

4. molars (6)

Dentition: the arrangement of an animal’s teeth

Incisors

At the front of the mouth

Relatively sharp, chisel-shaped teeth

Used for biting off pieces of food

Canines

Behind incisors

Similar shape to incisors

Have same biting function

Molars, Premolars (Cheek teeth)

A flatter top surface(crown)

Chewing or crushing food

The crown of a tooth is covered with enamel (hardest substance in the body)

Underneath, dentine (softer but as hard as bone)

Middle of the tooth is pulp cavity (contains blood vessels and nerves)

The root of the tooth is covered with cement.

Fibres attatching tooth to jawbone but allows a slight degree of movement when the person is chewing

• In dentine, there are fine channels filled with cytoplasm

• Cytoplasm strands are kept alive by nutrients and oxygen from blood vessels in pulp cavity

Mammals have 2 sets of teeth

1. Milk teeth (a few months old to around 7)

2. Permanent teeth

Adult teeth - 32

Tooth decay (Dental caries)

1. Bacteria feeing on sugar

2. Forming lactate acids which dissolve tooth enamel

3. Enamel is penetrated

4. Acid breaks down dentine

5. A cavity is formed

6. Bacteria enters the cavity

7. Enlarge until decay reaches pulp cavity(nerves)

8. You feel pain

Periodontal disease - caused by bacteria

• Gums become inflamed, so sensitive

• Bleed when teeth are brushed

• Lead to loss of teeth

Dental hygiene

• Plaque, tartar

1. regular brush teeth

2. regular visit to dentist

3. use fluoride

4. avoid sweets and sugary drinks

5. balanced diet