Teeth grinding: the intriguing evolutionary reason it’s so common

We’ve all found ourselves grinding our teeth at some point in their lives, and it’s probably been during particularly stressful moments or periods of time. But what really is teeth grinding? Why do we do itand how can it be prevented?

Paleontologist Michael Archer, a Professor of Biological, Earth & Environmental Sciences at University of New South Wales, and dentist Dr Christopher Telford address these very questions in their article “Grinding on schedule” in Cosmos Magazine #96.

What is teeth grinding?

We humans don’t use our teeth as weapons so much anymore, at least once we’re out of childhood and have been socialised to refrain from that kind of behaviour. But that doesn’t mean we don’t know it can be a threat when they’re on display – think a dog barring its teeth.

Humans respond in many ways to the stress of a threat, you’re probably already familiar with the instinctive survival response of fight or flight.

Read more: Birds shun fight to aid their flight

What you might not know, according to Archer and Telford, is that another one of those responses is called “thegosis” – the act of grinding teeth to sharpen them.

Thegosis – which is a Greek word that means to sharpen or wet – describes the process by which many animals, including humans, sharpen their teeth, beaks, or any other interacting hard parts.

Why is this behaviour necessary? Well, just like using your knives or scissors dulls them over time, eating or fighting will dull the cutting edge of teeth.

Some animals whose upper and lower teeth don’t actually meet, like sharks and crocodiles, replace their teeth by growing new ones. Other animals whose upper and lower teeth or beaks do meet, instead resharpen them by grinding them against each other.  

Read more: Smile, we’re taking a good look at your teeth.

In mammals, thegosis results in the sharpening of the anterior teeth – the 12 teeth at the front of the mouth which includes the incisors and canines – when the lower teeth are ground against the upper teeth in a forwards and sideways direction.

You wouldn’t think it, but these teeth are our primary biological weapon, and grinding them is an important way of keeping them sharp. So, it makes sense that we would do so in response to a perceived threat.

Thegosing also sharpens the cheek teeth, the premolars and molars, which is important for chewing our food into smaller pieces.

Excessing teeth grinding can become a problem

Teeth grinding is also known as “bruxism” – a condition in which people grind, gnash or clench their teeth, either while awake or during sleep.

According to Archer and Telford, the more stress we are under, the more intensely we thegose our teeth in response to that perception of threat. 

Dental retainer
Dental splint or dental retainer. Credit: Tanaonte/Getty Images

Normally, our brains can suppress the instinct while awake, but during deep sleep that instinct can emerge again, to begin thegosis. And if a threatening or frightening confrontation is too intense, humans may also spontaneously thegose while awake.

Severe stress can also cause excessive teeth grinding, and this can have harmful consequences, including headaches, damage to parts of the face, head, and neck, and even sensitive or broken teeth.

But while using a splint or mouth guard may temporarily limit the amount of dental damage that occurs, Archer and Telford suggest that it doesn’t fix the root of the problem – stress.

Instead, they suggest that dentists should explain the relationship between stress and excessive teeth grinding to their patients and, if appropriate, refer severely stressed individuals to a psychologist who can help treat the underlying cause, instead of the symptoms.

Cosmos Magazine #96 is available now. Subscribe at comosmagazine.com and save up to $35.

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