Mouth and Teeth

Why Are the Mouth and Teeth Important?

Every time we smile, frown, talk, or eat, we use our mouths and teeth. Our mouths and teeth let us make different facial expressions, form words, eat, drink, and begin the process of digestion.

The mouth is essential for speech. With the lips and tongue, teeth help form words by controlling airflow out of the mouth. The tongue strikes the teeth or the roof of the mouth as some sounds are made.

When we eat, our teeth tear, cut, and grind food in preparation for swallowing. The tongue helps push food to the teeth, and allows us to taste the food we eat. 

What Do the Parts of the Mouth Do?

The mouth is lined with moist mucous (MYOO-kus) membranes. The membrane-covered roof of the mouth is called the palate (PAL-it):

• The front part consists of a bony portion called the hard palate. The hard palate divides the mouth and the nasal cavity above.
• The fleshy rear part is called the soft palate. The soft palate forms a curtain between the mouth and the throat, or pharynx, to the rear. When we swallow, the soft palate closes off the nasal passages from the throat to prevent food from entering the nose.
  
  The soft palate contains the uvula (YOO-vyoo-luh), the dangling flesh at the back of the mouth. The tonsils are on either side of the uvula and look like twin pillars holding up the opening to the throat, or pharynx (FAR-inks).

A bundle of muscles extends from the floor of the mouth to form the tongue. The top of the tongue is covered with tiny bumps called papillae (puh-PIL-ee). These contain tiny pores that are our taste buds. Four main kinds of taste buds are found on the tongue — they sense sweet, salty, sour, and bitter tastes.

During chewing, salivary glands in the walls and floor of the mouth secrete saliva (spit), which moistens the food and helps break it down even more. Saliva makes it easier to chew and swallow foods (especially dry foods), and contains enzymes that help begin the digestion of foods.

Once food is a soft, moist mass, it's pushed to the back of the mouth and the throat to be swallowed.

How Do Teeth Do Their Job?

Each type of tooth plays a role in the chewing process:

• Incisors are the squarish, sharp-edged teeth in the front of the mouth that cut foods when we bite into them. There are four on the bottom and four on the top.
• On either side of the incisors are the sharp canines. The upper canines are sometimes called eyeteeth or cuspids.
• Behind the canines are the premolars, or bicuspids, which grind and mash foods. There are two sets, or four premolars, in each jaw.
• The molars, found behind the premolars, have points and grooves, and allow for vigorous chewing. There are 12 molars — three sets in each jaw called the first, second, and third molars. The third molars are the wisdom teeth. Because they can crowd out the other teeth or cause problems like pain or infection, a dentist might need to remove them.

Humans are diphyodont (dy-FY-uh-dant), meaning that they develop two sets of teeth. The first set are 20 deciduous (duh-SID-you-wus) teeth that are also called the milk, primary, temporary, or baby teeth. They begin to develop before birth and begin to fall out when a child is around 6 years old. They're replaced by a set of 32 permanent teeth, which are also called secondary or adult teeth.

What Are the Parts of the Teeth?

Human teeth are made up of four different types of tissue: pulp, dentin, enamel, and cementum.

• The pulp is the innermost portion of the tooth and consists of connective tissue, nerves, and blood vessels, which nourish the tooth. The pulp has two parts — the pulp chamber, which lies in the crown, and the root canal, which is in the root of the tooth. Blood vessels and nerves enter the root through a small hole in its tip and extend through the canal into the pulp chamber.
• Dentin surrounds the pulp. A hard yellow substance, it makes up most of the tooth and is as hard as bone. It's the dentin that gives teeth their yellowish tint.
• Enamel, the hardest tissue in the body, covers the dentin and forms the outermost layer of the crown. It lets teeth withstand the pressure of chewing and protects them from harmful bacteria and changes in temperature from hot and cold foods.
• A layer of cementum covers the outside of the root, under the gum line, and holds the tooth in place within the jawbone. Cementum is also as hard as bone.

How Can I Help Keep My Mouth and Teeth Healthy?

To help keep your mouth and teeth healthy:

• Eat a nutritious diet. Limit juice, sugary snacks, and sticky foods like dried fruit.
• Go for regular dental checkups.
• Brush your teeth twice a day for 2 minutes at a time. Floss the teeth once a day.
• Use a mouthguard during sports where there is a risk of mouth injury.
• Never walk or run with anything in the mouth, such as a toothbrush or pencil.
• Stay smoke-free. People exposed to secondhand smoke are more likely to get cavities. If you or anyone in your household smokes, call 1-800-QUIT-NOW for tips and advice on quitting.