Teeth

What are teeth?

Your teeth play a big role in digestion. They cut and crush foods, making them easier to swallow.

Though they look more like bones, teeth are actually ectodermal organs. Other ectodermal organs include your hair, skin and sweat glands.

How many teeth do humans have?

Most adults have 32 permanent teeth. But some people are born with missing teeth (hypodontia), and some people have extra teeth (hyperdontia).

Most children have 20 primary teeth that grow in (erupt) between the ages of 4 months old and 6 years old. These are baby teeth that’ll eventually fall out and make room for permanent adult teeth.

What are the four types of teeth?

We have different types of teeth, and each type serves an important purpose. There are four types of permanent teeth in humans:

• Incisors.
• Canines.
• Premolars.
• Molars.

Incisors

Your incisors are the most visible teeth in your mouth. Most people have four incisors on the upper jaw and four on the lower. These include your front two teeth and the teeth on either side of them.

Each incisor has a single narrow edge, which helps cut into food when you bite.

Canines

Canine teeth get their name because they resemble a dog’s fangs. They’re pointier than other types of teeth. Most people have four canine teeth — one in each quadrant (upper right, upper left, lower right, lower left).

Canine teeth help you tear into foods like meat and crunchy vegetables. Sometimes, people call canines “eye teeth” because of their position directly under your eyes.

Premolars

Also called bicuspids, premolars sit between your canines and your molars (the teeth in the back of your mouth).

Premolar teeth have features of both canines and molars. They help you tear, crush and grind food into smaller pieces.

Molars

Your molar teeth are in the very back of your mouth. Most of your chewing — about 90% — takes place here. Most adults have 12 molar teeth — three in each quadrant.

Molar teeth include wisdom teeth (third molars). So, if you’ve had your wisdom teeth removed, or if you were born without them, then you probably have eight molars altogether.

Because molars are your main chewing teeth, they’re good for crushing and grinding up your food.

How do teeth function?

All of your teeth work together harmoniously to cut, tear, mix and grind your food into smaller pieces. Then, your tongue and oropharynx (the upper part of your throat) shape the food into a small ball that’s easy to swallow.

What’s the anatomy of a tooth?

A tooth consists of two main structures:

• Crown. This is the part of your tooth that you can see — the portion above your gums. Enamel — a hard, protective substance — covers your tooth crown.
• Root. This is the part of your tooth that holds it in your jaw. You can’t see the root because your gums cover it. The root anchors your tooth to your periodontal ligament (the soft connective tissue that lines your tooth socket).

What are teeth made of?

Your teeth have four main layers, including:

• Enamel. This is the protective outer layer of each tooth. Enamel helps shield your teeth from cavity-causing bacteria. Enamel is the hardest substance in the human body.
• Dentin. Just underneath your enamel, there’s a layer of dentin. Dentin isn’t as strong as enamel. When missing enamel exposes dentin, your risk for cavities increases.
• Cementum. Cementum covers your tooth root. Along with your periodontal tissues, it helps anchor your tooth firmly in your jaw.
• Tooth pulp. This is the innermost layer of your tooth. It contains nerves, blood vessels and connective tissues.

Are teeth bones?

No. Although teeth resemble bones, they’re actually quite different. Bones can regenerate (repair) when they’re broken. Teeth can’t. Unlike bones, your teeth don’t contain marrow.

What are teeth numbers?

Dentists and other healthcare providers use numbering systems to label teeth. There are a few different numbering systems, but the one most providers in the United States use is the Universal Numbering System.

Universal Numbering System for adult teeth

The Universal Numbering System assigns a number from 1 to 32 to adult teeth, beginning with your upper-right third molar. You count toward your two front teeth and then to the left side. Once you reach #16 (your upper-left third molar), you drop down and begin with #17 (your lower-left third molar). Then, counting across your lower teeth, you end up at #32 (your lower-right third molar).

Dentists still assign numbers to any missing teeth. By doing this, they can create an accurate tooth chart to keep in your records.

Universal Numbering System for baby teeth

Dentists also use the Universal Numbering System to label primary (baby) teeth. It works in a similar way, but instead of numbers, you use letters. For example, baby teeth are labeled A to T, beginning with the upper-right molar. Counting all the way across the upper teeth, you reach #J (the upper-left molar). Next, you drop down to #K on the lower left, then count all the way across the lower teeth until you reach #T (the lower-right molar).

What are the common conditions that can affect my teeth?

Tooth decay is one of the most common dental issues. In fact, over 90% of adults in the U.S. over 40 have had at least one cavity. Cavities can form when bacteria eat through the hard, outer layer of your enamel. Once the dentin underneath loses this protective layer, the bacteria continue to erode your tooth.

Other common issues that can affect your teeth include:

• Bruxism (teeth grinding). Clenching and grinding your teeth can erode the enamel and make your teeth more susceptible to damage.
• Teeth sensitivity. Most of the time, teeth sensitive to heat and cold have worn enamel or exposed roots.
• Trauma to your mouth. Vehicular accidents, sports-related injuries and other traumas can lead to chipped, cracked or knocked-out teeth.
• Tooth discoloration. It’s normal for some foods and drinks — such as tea, coffee or berries — to stain your teeth over time. You can also develop tooth discoloration from taking certain medications.
• Impacted teeth. Sometimes teeth don’t erupt properly and they get stuck in your gums or jaw bone. The most common example is wisdom teeth impaction, though it can happen to any tooth.
• Orthodontic misalignment. Crooked, gapped, crowded or rotated teeth are all examples of orthodontic misalignment. These conditions can have a negative impact on your oral health and chewing function.
• Abscessed tooth. Sometimes bacteria invade the pulp — the innermost layer of your tooth. When this happens, you could develop a painful abscess (pocket of pus).
• Gum disease. Even though gum disease starts in your gums, it can eventually lead to loose teeth and tooth loss.

What are some common symptoms of conditions affecting my teeth?

Some of the most common complaints among people with dental issues include:

• Toothache.
• Sensitivity to heat, cold or sweets.
• Pain when biting down.
• Sore, bleeding gums.
• Swollen jaw.

What are some common dental treatments?

Some of the most common dental treatments include:

• Dental fillings.
• Dental crowns.
• Dental bridges.
• Dental bonding.
• Teeth whitening.
• Porcelain veneers.
• Teeth braces.
• Dental implants.
• Dentures.

How can I keep my teeth healthy?

Proper oral hygiene is the key to healthy teeth and gums. Here are some general guidelines:

• Visit your dentist for regular exams and teeth cleanings.
• Brush your teeth at least twice a day for at least 2 minutes.
• Use a soft-bristled toothbrush and fluoride toothpaste.
• Floss between your teeth once every day.
• Use an alcohol-free, antibacterial mouthwash.

What if I’m missing teeth?

Sometimes, people are born without certain teeth. Others may lose teeth due to cavities, gum disease or trauma.

Whether you need to replace the tooth depends on a few factors, including the location of the missing tooth and your personal oral health goals.

Today, there are many teeth replacement options available, including dental implants, dental bridges and dentures.

How does a tooth feel pain?

Each tooth has nerves and blood vessels that supply nutrients. When an infection reaches the tooth pulp, the nerves in the center of the tooth can detect pain.

A note from Cleveland Clinic

Your teeth are an essential part of your digestive system. They help you bite, tear and grind food up before swallowing it. To keep your teeth healthy, visit your dentist regularly and practice good oral hygiene at home. With proper care and maintenance, your teeth can serve you well for a lifetime.