Human Dentition: Structure and Dental Formula

• Canines in humans are quite similar to the incisors
• Premolars and molars in humans have broad surfaces for grinding food

Dental Formula

• Shows the number and types of teeth an animal has in each half of each jaw
• Different mammals have different dental formulae depending on diet
• The dental formula of a human is: i2/2 c1/1 pm2/2 m3/3 = 16
• Each of the four types of teeth is indicated by its initial letter
• The total number of teeth is indicated by the dental formula multiplied by 2.
• Humans have 32 teeth

Tooth Structure

• All teeth have the same basic structure
• The crown projects above the gums
• The root is embedded in the jawbone
• The neck is the junction of the crown and root
• The center of the tooth is the pulp cavity, containing blood vessels and nerves, which are sensitive to heat and cold
• Enclosing the pulp is a layer of dentine, a hard and bone-like material
• Dentine contains living cytoplasm
• A hole at the tip of each root allows blood vessels and nerves of the pulp to connect to bones and gums

Enamel and Cement

• Enamel is a white layer covering the dentine
• Enamel is the hardest material made by animals
• Enamel protects the pulp and dentine
• Enamel is not present in the root region
• A thin layer of cement covers the dentine in the root region
• Cement is surrounded by the periodontal membrane, which fixes the tooth to the jawbone, but allows slight movement during biting and chewing
• Each tooth has a continuous blood supply through holes at the root tip

Closed Teeth

• Teeth are kept alive by a continuous blood supply
• Blood supply is sufficient to keep the tooth alive but not enough to allow the tooth to grow
• This sort of teeth are known as closed teeth

Dental Care

• Teeth can easily decay
• Germs grow on bits of food that stick to the teeth after meals
• Germs break down food particles (especially carbohydrates) to produce acids
• Acids wear away the enamel and dentine, exposing the nerves and blood vessels in the pulp cavity
• The tooth begins to ache and the gum becomes infected
• Permanent teeth cannot be replaced once they fall out
• It's very important to take care of our teeth