Oww! Scientists discover the molecule in dental cells that signals the brain when exposed to cold

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There is nothing more excruciating than biting into a cold ice cream and feeling a terrible pang, especially if you’ve been a little lax in the dental hygiene department.

Researchers from the US and Germany have finally discovered the cause of this pain – by identifying the specific cells in teeth, odontoblasts, that perceive cold temperatures.

These cells are rich in special cold-sensitive proteins that ensure that the brain knows when you eat or drink something cold.

According to the team, developing drugs specifically targeting these sensors could eventually pave the way to new treatments for cold sensitivity.

Additionally, the findings finally also explain an age-old home remedy for toothache, clove oil, which happens to contain a chemical that blocks the cold-sensitive protein.

Cold sensitivity is often more extreme in people with cavities, where some of a tooth’s protective enamel is worn away by films of bacteria and acid.

It is estimated that about 2.4 billion people – about a third of the world’s population – have untreated cavities in their permanent or ‘adult’ teeth.

There is nothing more excruciating than biting into a cold ice cream and feeling a terrible pang, especially if you've been a little lax in the dental hygiene department.  Researchers from the US and Germany have finally discovered the cause of this pain: they identify the specific cells in teeth, odontoblasts, that sense cold temperatures (stock image)

There is nothing more excruciating than biting into a cold ice cream and feeling a terrible jolt of pain, especially if you’ve been a little lax in the oral hygiene department (stock image)

The researchers – led by neurobiologist David Clapham of the Howard Hughes Medical Institute in Maryland – originally had no intention of studying teeth.

Instead, their work focused on so-called ‘ion channels’, pores in the membranes of cells that act as gates to molecules.

When these channels detect a particular signal, such as a chemical message or temperature change, they respond by either clamping shut or opening wide.

In the latter case, ions flow into the cell, creating an electrical pulse that travels to other cells and allows the body to transmit information.

About 15 years ago, the team determined that such an ion channel – TRPC5 – was very sensitive to cold. However, it was unclear where TRPC5 was used.

The researchers were able to rule out its action in the skin, at least by publishing in a 2011 paper that mice lacking the ion channel were still able to feel the cold

After that, they ‘ran to a dead end,’ explains team member and electrophysiologist Katharina Zimmermann, who was originally a member of Professor Clapham’s laboratory but now works at Friedrich-Alexander University Erlangen-Nürnberg in Germany.

However, the inspiration eventually came when the team was having lunch. Teeth are another part of the body with cold sensitivity – and one that worked in a way that wasn’t entirely clear at the time.

Experts from the US and Germany have finally discovered the cause of this pain, documented in this work of art, where the specific cells in teeth, odontoblasts, perceive cold temperatures

Experts from the US and Germany have finally discovered the cause of this pain, documented in this work of art, where the specific cells in teeth, odontoblasts, perceive cold temperatures

Experts from the US and Germany have finally discovered the cause of this pain – captured in this artwork – by identifying the specific cells in teeth, odontoblasts, that perceive cold temperatures

The main theory for how teeth feel cold involved tiny channels in the teeth that contain fluid that moves when the temperature changes.

It was thought that nerves could perhaps sense the direction of this movement, thus indicating whether a tooth was hot or cold.

“We cannot rule out this theory,” said Professor Clapham. However, he added that there was no direct evidence for it either.

The problem is that the smooth motion of the teeth is extremely difficult to study – since gaining access to the inside of the teeth means cutting through hard layers of enamel and dentin without crushing the soft pulp that protects it.

As Professor Zimmerman grimly explained, teeth studied in this way sometimes “just fall apart.”

Teeth are particularly difficult to study, the team explained, because accessing their inner workings involves cutting hard layers of enamel and dentin without crushing the soft pulp that protects it.  Picture: a cross section of a tooth.  Odontoblasts are located between the pulp cavity and the surrounding dentin layer

Teeth are particularly difficult to study, the team explained, because accessing their inner workings involves cutting hard layers of enamel and dentin without crushing the soft pulp that protects it.  Picture: a cross section of a tooth.  Odontoblasts are located between the pulp cavity and the surrounding dentin layer

Teeth are particularly difficult to study, the team explained, because accessing their inner workings involves cutting hard layers of enamel and dentin without crushing the soft pulp that protects it. Picture: a cross section of a tooth. Odontoblasts are located between the pulp cavity and the surrounding dentin layer

Despite these challenges, when Professor Clapham and colleagues examined adult human teeth, they found that they do indeed contain TRPC5 ion channels, as they had previously guessed.

Additionally, TRPC5 is more common in cavity teeth, which are notoriously more sensitive to cold than their healthy counterparts.

To investigate further, the team conducted experiments on live mice – recording their neural activity when their teeth came into contact with an ice-cold solution.

In regular mice, the team found that the chill triggered nervous activity. Mice that missed TRPC5 or had been treated with a chemical that blocked the ion channel did not respond in the same way, suggesting that TRPC5 is the key to cold detection in teeth.

The team traced the location of TRPC5 to a specific type of cell in teeth called 'odontoblasts' (shown here in green) that can be found between the pulp and surrounding dentin.

The team traced the location of TRPC5 to a specific type of cell in teeth called 'odontoblasts' (shown here in green) that can be found between the pulp and surrounding dentin.

The team traced the location of TRPC5 to a specific type of cell in teeth called ‘odontoblasts’ (shown here in green) that can be found between the pulp and surrounding dentin.

The team also found that another ion channel in teeth, ‘TRPA1’, also appears to play a role in responding to cold temperatures.

Finally, the team traced the location of TRPC5 to a specific type of dental cell called ‘odontoblasts’, found between the pulp and surrounding dentin.

When someone bites themselves on a cold ice cream – especially if they have cavities and exposed dentin – these cells are full of TRPC5 that pick up the cold sensation and send pain signals to the brain.

The full findings of the study have been published in the journal Science Advances

OWW, TEETH!

Causes of toothache

Toothache can be caused by:

  • tooth decay
  • a dental abscess
  • a cracked or damaged tooth
  • a loose or broken filling
  • an infection – this often happens when a tooth (such as a wisdom tooth) has broken the skin but doesn’t have enough room to come through completely
  • problems with your braces

How to prevent a toothache

The best way to prevent a toothache is to keep your teeth and gums as healthy as possible.

To do this:

  • undergo regular dental check-ups
  • Cut back on sugary foods and drinks – only take them as an occasional treat at mealtimes
  • brush your teeth with a fluoride toothpaste twice a day for about 2 minutes
  • clean between your teeth daily with dental floss or an interdental brush to remove food, dirt and plaque

When should you visit a dentist?

See a dentist if you have a toothache:

  • that takes more than 2 days
  • that will not go away if you are taking painkillers
  • with a high temperature, pain when biting, red gums or a bad taste in your mouth
  • and your cheek or jaw is swollen

How to relieve a toothache while waiting for an appointment

To do:

  • taking painkillers, such as ibuprofen or acetaminophen (children under 16 should not take aspirin) – a pharmacist can advise you
  • try rinsing your mouth with salt water (kids shouldn’t try this)
  • use an analgesic gel for your mouth – you can buy this from pharmacies or supermarkets
  • eat soft foods, such as yogurt or scrambled eggs, and try to avoid chewing with the sore tooth

Not:

  • eat foods that are sweet, very hot, or very cold
  • smoke – it can make some dental problems worse

SOURCE: NHS