As a dentist, I thought I knew everything about teeth. But after doing some research I found a few points that can be interesting to share. In fact there are many things about teeth that people are unaware of, and a few that might even surprise people working in the dental field. I gathered ten of what I thought can be the most fascinating ones.

1- Enamel is the hardest substance in the body

Enamel is the most solid and most mineralized substance in the body. It is made of 96 % minerals and 4 % of water and organic materials, where the primary mineral is called hydroxyapatite.

As enamel is the outer layer of all teeth in the mouth, it is made to be very hard so it can chew and break down almost all types of foods. But even though it’s the hardest tissue in the body, enamel is more brittle than other parts of a tooth and can therefore break more easily.

2- Not everyone has 2 sets of teeth

Humans grow 2 sets of teeth, primary teeth and permanent teeth. But some animals grow many more. Primary teeth in humans start erupting a few months after birth, and they are slowly replaced by permanent teeth years later.

However, for example, sharks grow a new set of teeth every two weeks to replace older worn teeth. Also juvenile crocodiles replace their teeth with larger ones every month, but the rate slows down at adulthood.

3- Teeth can be found in strange places

Teeth, when in the mouth, are not always attached to the jaw like for mammals and humans. They can grow on the palate, the floor of the mouth, or on the pharynx, like for many fish and reptiles.

Teeth can rarely grow on other organs of the human body. They are called teratomas, which are mild and rarely aggressive tumours that have dental or hair tissue in them. They can be found in the nose, on the tongue, in they eye, on the neck, in the brains, and even in the ovaries or the testicles!

4- Each set of teeth is unique

Each person’s set of teeth is different from anyone else’s, a lot like fingerprints. A set of teeth, or dentition, is the way teeth have erupted one next to the other. Even if the differences are calculated within fractions of millimetres, each tooth has a particular size, a particular placement, and a certain distance from its neighbour, which makes the whole set unique. Even identical twins do not have exactly the same set of teeth, because a set of teeth is not only determined by genes, but also by what happens in the mouth after birth. For example, a twin that sucks his or her thumb will have a different set from his/her brother/sister.

Forensic dentistry is the science that identifies victims or criminals based on their unique dentition. It uses dental records, which are either teeth impressions or x-rays.

Did you know that your tongue print is also unique?

5- Teeth need saliva

Although it does not replace brushing and flossing, saliva has a protective function. It helps to prevent dental plaque and food particles from building-up too much on teeth by washing them away. Bacteria in dental plaque can cause cavities and also lead to gum disease.

A healthy person produces 0.75 to 1.5 litres of saliva per day, which makes about 35,000 litres a lifetime, enough to fill two swimming pools! But xerostomia (decreased production of saliva) is a condition where a person can have, mostly at a later age, and it makes teeth more susceptible to dental diseases.

6- Not everyone wants straight teeth

Orthodontics is the branch of dentistry that straightens crooked teeth. Wearing braces is particularly popular in North America (and in lots of other countries) where for people a beautiful smile means having teeth that are well aligned.

But straight teeth are not the beauty ideal in every culture. For example, in Japan, some people might choose to get crooked veneers to cover up their straight teeth.

7- Some teeth are (very) expensive

In 2011, in an auction in London UK, a Canadian dentist has bought one of John Lennon’s teeth for £19,500 ($30,500). The buyer is hoping to use the DNA found in the tooth to clone Mr. Lennon in the future.

In 1816, a tooth said to belong to Sir Isaac Newton’s was also sold in London for £730 ($1,140), which is today’s equivalent of $35,700. This would be the most expensive sold human tooth known in history.

Unfortunately, nowadays the Tooth Fairy brings an average of just $3 per baby tooth lost.

8- Teeth are the only structures that can’t repair themselves

Unlike other organs in the body, which can heal themselves if they go under some level of damage, teeth cannot do that. If someone chipped a tooth, unfortunately only a dentist can repair it. The outer layer of the tooth is enamel, which is not a living tissue. Since it’s not alive, it cannot repair itself.

In reality teeth heal themselves to a very minimal extent, and only in deeper tissues other than the enamel. But due to a lack of the right cells they have no chance against visible cavities, infections or trauma.

9- Some people are born with missing teeth

Hypodontia, or tooth agenesis, is a condition where there are one or more teeth that are missing in a person’s mouth because they have never actually developed. The most common one is a wisdom tooth that can be missing in 9-35 % of people depending of racial factors. Other missing teeth can be the upper adult lateral incisors, or the second premolars.

Anodontia is a very rare condition where a person has all of their teeth missing. Another situation is hyperdontia where there are supernumerary teeth in the mouth, which are teeth that appear in addition to the regular number of teeth.

10- There is a tooth bank in Norway

MoBaTann, MoBaTooth in English, is a Norwegian tooth bank that plans to collect 100,000 baby teeth. All these teeth will be part of a study that will analyse the relationship between pollution of the environment and subsequent disease.

Primary teeth can give valuable information about environmental factors and nutrition during the foetal stage and in early childhood. Other information collected are the mother’s diet and the parents’ surroundings during pre- and post-pregnancy. All this data will give knowledge about the effect environmental pollutants have on children’s health.

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