Teeth and Tooth Decay

• • In Humans, only the LOWER Jaw is Movable, while the Upper Jaw is fixed to the SKULL
  • Chewing is done by Cheek Muscles, which move the LOWER Jaw up and down, and SOME side-to-side movement
• Teeth Formation (Dentition)

  • Adults have 32 teeth. The Formation is (2123 | 2123) x 2
  • Children (under 7) have 20 teeth. Their Formation is (2012 | 2012) x 2

  A) Incisors

  B) Canines

  C) Premolars

  D) Molars

  
• [Incisors.] Biting off PIECES of Food

  [Canines.] Tearing up the Pieces of Food

  [Premolars + Molars.] Grinding and tearing up the Food

  
• Inside an Incisor (side view):

  • [Enamel] is the hard, NON-Living material which covers the outside of the tooth
  • [Dentine] Softer material under the Enamel, but still as HARD as Bone
  • [Pulp Cavity] Contains Blood Vessels and Nerves

  A) Crown

  B) Root

  C) enamel

  D) dentine

  E) Pulp Cavity

  F) Vessels

  
• The FIRST set of Teeth are called the Milk Teeth. These grow on a child that is just a few months old

  • By 21 or 22 Months, a child will have a set of 20 Teeth
  • But, at the Age of 7 Years, the Milk Teeth are pushed out by Permanent Teeth growing underneath them

  A) -

  
• Tooth Decay (or Dental Caries):

  • It's caused by Bacteria in the mouth FEEDING on Sugar
  • The Bacteria Break down the sugar, forming Acids which DISSOLVE the Tooth Enamel. When the Enamel is broken into, the Acid breaks down the Dentine underneath, where a Cavity is formed

  [Periodontal Disease] the Gums become inflamed and too SENSITIVE to brush, so they BLEED