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Teeth: Names, types, and functions

Teeth are made up of different layers — enamel, dentin, pulp, and cementum. Enamel, which is the hardest substance in the body, is on the outside of the tooth. The second layer is dentin, which is softer than enamel, and the deepest layer inside the tooth is pulp, which consists of nerves and blood vessels. Cementum is on the root of the tooth and is beneath the gums.

The number and types of teeth a person has changes as they age. Typically, people have two sets of teeth during their life — primary, or baby teeth, and permanent, or adult teeth. In this article, we look at the teeth that children and adults have, as well as their functions.

Humans have the following types of teeth:

Incisors

Incisors are the sharp teeth at the front of the mouth that bite into food and cut it into smaller pieces. They are flat with a thin edge. They are also called anterior teeth.

Both children and adults have eight incisors — four central incisors at the front of the mouth, two on each row, with one lateral incisor positioned on either side of them.

Canines

Canines are the sharp, pointed teeth that sit next to the incisors and look like fangs. Dentists also call them cuspids or eyeteeth. Canines are the longest of all the teeth, and people use them to tear food.

Both children and adults have four canines. Children usually get their first permanent canines between the ages of 9 and 12. The lower canines tend to come through slightly before those in the upper jaw.

Premolars

Premolars, or bicuspids, are bigger than the incisors and canines. They have many ridges and help chew and grind up food. Adults have eight premolars. The first and second premolars are the molars that sit next to the canines.

Young children do not have premolar teeth. These first appear as permanent teeth when children are 10–12 years old.

Molars

Molars are the biggest of all the teeth. They have a large, flat surface with ridges that allow them to chew food and grind it up. Adults have 12 permanent molars — six on the bottom and top jaw, and children have eight primary molars.

The last molars to erupt are wisdom teeth, or third molars, which usually come through between the ages of 17–21. These sit at the end of the row of teeth, in the far corners of the jaw. Some people do not have all four wisdom teeth, or the teeth may stay unerupted in the bone and never appear in the mouth.

Sometimes wisdom teeth can become impacted, which means they can become trapped under the gum and are unable to come through properly.

Wisdom teeth that only come through halfway or are in the wrong position can increase the risk for infection or damage in surrounding areas. It is essential to see a dentist if people have any issues with their wisdom teeth.

People may experience mild discomfort when their wisdom teeth start pushing through the gums, but anyone feeling a lot of pain or has swelling should see a dentist.

A dentist may need to remove wisdom teeth if a person has tooth decay, pain, or an infection. People do not need these teeth for chewing, and they are difficult to keep clean because of their position far back in the mouth.

Number of teeth

Children have 20 primary, or baby, teeth. Primary teeth first start to appear when babies are around 6 months old. Children usually get all their primary teeth by the age of 3.

These teeth gradually fall out, and 28 permanent teeth replace them. Sometimes, permanent teeth push the baby teeth out, but typically, permanent teeth come through the gums at the back of the mouth behind the last baby tooth in the jaw.

The first permanent teeth to erupt through the gums are four first, or ‘6-year’ molars, so-called because they usually come through when a child is about 6 years old.

The first baby teeth to fall out are the lower central incisors. The adult central incisors tend to erupt around the same time as the first permanent molars around age 6-7.

Usually, people have lost all of their baby teeth by around the age of 14.

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How does tooth enamel last a lifetime?

If we cut our skin or break a bone, these tissues will repair themselves; our bodies are excellent at recovering from injury.

Tooth enamel, however, cannot regenerate, and the oral cavity is a hostile environment.

Every mealtime, enamel is put under incredible stress; it also weathers extreme changes in both pH and temperature.

Despite this adversity, the tooth enamel that we develop as a child remains with us throughout our days.

Researchers have long been interested in how enamel manages to stay functional and intact for a lifetime.

As one of the authors of the latest study, Prof. Pupa Gilbert from the University of Wisconsin–Madison puts it, «How does it prevent catastrophic failure?»

The secrets of enamel

With assistance from researchers at the Massachusetts Institute of Technology (MIT) in Cambridge and the University of Pittsburgh, PA, Prof. Gilbert took a detailed look at the structure of enamel.

The team of scientists has now published the results of its study in the journal Nature Communications.

Enamel is made up of so-called enamel rods, which consist of hydroxyapatite crystals. These long, thin enamel rods are around 50 nanometers wide and 10 micrometers long.

By using cutting edge imaging technology, the scientists could visualize how individual crystals in tooth enamel are aligned. The technique, which Prof. Gilbert designed, is called polarization-dependent imaging contrast (PIC) mapping.

Before the advent of PIC mapping, it was impossible to study enamel with this level of detail. «[Y]ou can measure and visualize, in color, the orientation of individual nanocrystals and see many millions of them at once,» explains Prof. Gilbert.

The architecture of complex biominerals, such as enamel, becomes immediately visible to the naked eye in a PIC map.

When they viewed the structure of enamel, the researchers uncovered patterns. «By and large, we saw that there was not a single orientation in each rod, but a gradual change in crystal orientations between adjacent nanocrystals,» explains Gilbert. «And then the question was, ‘Is this a useful observation?'»

The importance of crystal orientation

To test whether the change in crystal alignment influences the way that enamel responds to stress, the team recruited help from Prof. Markus Buehler of MIT. Using a computer model, they simulated the forces that hydroxyapatite crystals would experience when a person chews.

Within the model, they placed two blocks of crystals next to each other so that the blocks touched along one edge. The crystals within each of the two blocks were aligned, but where they came in contact with the other block, the crystals met at an angle.

To investigate, co-author Cayla Stifler returned to the original PIC mapping information and measured the angles between adjacent crystals. After generating millions of data points, Stifler found that 1 degree was the most common size of misorientation, and the maximum was 30 degrees.

This observation agreed with the simulation — smaller angles seem better able to deflect cracks.

Now we know that cracks are deflected at the nanoscale and, thus, can’t propagate very far. That’s the reason our teeth can last a lifetime without being replaced.

Prof. Pupa Gilbert

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Tooth extraction aftercare: A how-to guide

A dentist or dental surgeon will perform the extraction in their clinic and then give the person some instructions for caring for the area as it heals.

During the appointment, the dental surgeon will inject a strong anesthetic into the area around the tooth to prevent the person from feeling any pain. They will then use a series of instruments to loosen the tooth before pulling it out.

After removing the tooth, they will place gauze over the extraction site to help control bleeding and promote clotting.

Learn more about tooth extraction aftercare in this article. We also provide a general healing timeline and explain when to speak to a dentist.

Aftercare

Aftercare for an extracted tooth can vary slightly depending on a few factors.

These include which tooth the dentist took out, as some teeth have deeper roots than others and take longer to heal. However, most people find that pain decreases after about 3 days.

One of the most important aspects of aftercare is maintaining the blood clot that forms in the socket where the tooth used to be.

Caring for this blood clot is key to the healing process, and it helps prevent painful complications, such as dry socket.

Days 1–2

Much of the aftercare in the first couple of days following an extraction focuses on allowing a blood clot to form and caring for the mouth in general.

As some experts note, low level bleeding for up to 24 hours after an extraction is perfectly normal. However, active bleeding after this point requires treatment.

Here are a few additional tips for the first 2 days of aftercare:

  • Get plenty of rest: Expect to be resting for at least the first 24 hours after the extraction.
  • Change the gauze as necessary: It is important to leave the first gauze in the mouth for at least a few hours to allow the clot to form. After this, it is fine to change the gauze as often as necessary.
  • Avoid rinsing: As tempting as it can be, avoid rinsing, swishing, or gargling anything in the mouth while the area is still clotting. These actions may dislodge any clot that is forming and affect the healing time.
  • Do not use straws: Using a straw places a lot of pressure on the healing wound, which can easily dislodge the blood clot.
  • Do not spit: Spitting also creates pressure in the mouth, which may dislodge the blood clot.
  • Avoid blowing the nose or sneezing: If the surgeon removed a tooth from the upper half of the mouth, blowing the nose or sneezing can create pressure in the head that may dislodge the developing blood clot. Avoid blowing the nose and sneezing if possible.
  • Do not smoke: Smoking creates the same pressure in the mouth as using a straw. While it is best to avoid smoking during the entire healing process, it is crucial not to smoke during the first couple of days as the blood clot forms.
  • Take pain relievers: Over-the-counter pain relievers may help reduce pain and inflammation.
  • Use cold compresses: Placing an ice pack or a towel-wrapped bag of ice on the area for 10–20 minutes at a time may help dull pain.
  • Elevate the head: When sleeping, use extra pillows to elevate the head. Lying too flat may allow blood to pool in the head and prolong healing time.
  • Take any medications that the dentist recommends: The dental surgeon may order prescription medications for complex removals. It is important to complete the full course of treatment.

Days 3–10

After the clot has formed, it is vital to keep it securely in place and to follow some extra steps for oral hygiene to help prevent other issues.

Tips for aftercare between the third and 10th day include:

  • Saline rinses: When the clot is securely in place, gently rinse the mouth with a warm saline solution or a pinch of salt in warm water. This mixture helps kill bacteria in the mouth, which may prevent infections as the mouth heals.
  • Brush and floss as usual: Brush and floss the teeth as usual, but take care to avoid the extracted tooth altogether. The saline solution and any medicated mouthwash that a dentist recommends should be enough to clean this area.
  • Eat soft foods: Throughout the entire healing process, people should eat soft foods that do not require a lot of chewing and are unlikely to become trapped in the empty socket. Consider sticking to soups, yogurt, applesauce, and similar foods. Avoid hard toast, chips, and foods containing seeds.

Aftercare for multiple teeth

Sometimes, dental surgeons will need to extract more than one tooth at a time. When extracting multiple teeth, the surgeon is more likely to recommend general anesthesia instead of using a local anesthetic.

The person will, therefore, be unconscious throughout the process. The dentist will also give them some special instructions leading up to the extraction, such as avoiding food for a certain time. After the procedure, the person will need someone else to drive them home.

Caring for multiple extractions can be challenging, especially if they are on different sides of the mouth. Dentists may have specific instructions for these cases, and they may request a follow-up appointment shortly after the extraction.

They may also use clotting aids in the extraction sites. These are small pieces of natural material that helps clotting. The body breaks the clotting aids down safely and absorbs them over time.

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Eleven tips to treat white spots on teeth

Although people may see white spots on their teeth as undesirable, they rarely need to be a serious cause for concern from a medical point of view.

In this article, we look at the reasons why people might get white spots on their teeth, and provide 11 tips for treating and preventing them.

Causes

There are several possible causes of white spots on the teeth.

A common cause is dental fluorosis.

People usually get this when they are young if they consumed too much fluoride as a child. It is usually a harmless condition that only tends to develop before the teeth break through the gums.

Another common cause is enamel hypoplasia.

This condition occurs when a person’s teeth enamel does not form properly. Like fluorosis, hypoplasia only occurs during childhood when a person’s teeth are still developing. However, it can increase the risk of tooth decay.

Other causes of white spots on the teeth include poor dental hygiene, especially when someone is wearing braces, or eating too many acidic or sugary foods.

Treatments

There are several possible treatments for white spots on the teeth. The suitability of these treatments may depend on the underlying cause of the white spots and the condition of a person’s teeth.

1. Enamel microabrasion

Some people may be able to have microabrasion done to treat their white spots. During this procedure, a dentist removes a small amount of enamel from the teeth to reduce the appearance of the white spots.

This professional treatment is typically followed by teeth bleaching, which can make the teeth appear more uniform in color.

2. Teeth whitening or bleaching

Whitening or bleaching teeth can help to reduce the appearance of white spots and other stains. A variety of teeth whitening products, such as strips and paste, are available over-the-counter (OTC.) People can also buy these products online.

People with white spots can also see a dentist for professional whitening treatments. These treatments tend to use stronger bleaching solutions than those available OTC, which may make them work better.

3. Dental veneer

Dental veneers are thin, protective coverings that attach to the front surface of a person’s teeth. They can conceal white spots and other blemishes very effectively.

Dental veneers are only available from a dentist and must be professionally fitted. This can make them costly.

4. Topical fluoride

A dentist may apply topical fluoride to the teeth of people with enamel hypoplasia. This may encourage the development of enamel on the teeth and help prevent tooth decay.

5. Composite resin

For people with enamel hypoplasia, a dentist may apply composite resin to fill in cavities and to bond the outer enamel of the teeth. This may not be suitable if people have large numbers of white spots on their teeth.

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