What's behind the alarming rise in a mystery dental condition that's leaving children's teeth discoloured and crumbling?

Rising numbers of British children are being affected by a little-known dental condition that leaves teeth yellowed, fragile and prone to crumbling, experts have warned.

The condition, known as molar incisor hypomineralisation (MIH), weakens the enamel, the protective outer layer of teeth, making them vulnerable to decay and damage.

Also known as ‘chalk teeth’, the problem becomes apparent as a child’s adult teeth come through from around the age of six.

In severe cases, teeth can become so brittle that they begin to break apart just months after emerging. This can leave youngsters facing years of dental problems, including repeated fillings, extractions and potentially costly long-term treatment.

Importantly, it is not caused by poor brushing, sugar or other day‑to‑day dental habits, but by a problem in how the enamel forms early in life.

And while traditional tooth decay linked to poor oral health has declined in recent decades, experts say MIH is being diagnosed far more frequently – and the condition appears to be on the rise.

Though only first recognised in the 1980s, today as many as one in six children in the UK are now believed to have the disorder.

And in Scandinavian countries, this estimate is even higher. According to recent research from Norwegian scientists, the condition impacts nearly one in three children in the region.

Dentists speaking to The Mail on Sunday say they’re seeing more and more children coming into their clinics with MIH – which can make eating, drinking and even brushing teeth an agonising experience.

Yet scientists are still baffled by what’s behind it.

‘We’re not sure why it’s happening,’ says Dr Helen Rodd, professor of paediatric dentistry at the University of Sheffield. ‘It’s not anything to do with how a child’s teeth are taken care of, because these teeth are developing at birth.

‘They’re coming in, around the age of six or so, with teeth that are already discoloured and crumbling. We just can’t explain it.’

Professor Greig Taylor, clinical lecturer in paediatric dentistry at Newcastle University and a spokesman for the British Society of Paediatric Dentistry, added: ‘It’s about the amount of mineral in the tooth.’

The enamel that covers teeth is the strongest substance in the body and is made largely from minerals – mainly phosphate and calcium.

But in children with MIH, the enamel forms with lower levels of these minerals and higher levels of protein, leaving it weaker and more porous.

Pieces of affected teeth can break away and are often a different colour to the surrounding teeth – ranging from mottled white to cream, yellow or brown.

By definition, the condition affects the first permanent molars – the back teeth that come through at around six – as well as the upper front incisors, which follow a year or so later.

However, experts say not all of these teeth will necessarily be affected.

‘What’s so unusual about the condition is that, for some children, just one tooth will have MIH, while for others, they’ll nearly all be affected,’ says Professor Taylor.

‘The effect on the tooth itself also ranges. In a mild case it may look like little white flecks – while on another the tooth may be dark brown and totally broken down.’

On the back molars, the lack of enamel can leave the tooth pulp – the soft, living tissue at the centre of the tooth, which is full of nerves – exposed, causing intense sensitivity when chewing and drinking, says Professor Rodd.

‘Enamel normally protects teeth from extremes of temperature. But in children with MIH, where this layer is weakened, the tooth is almost like a sponge. Everyday things like hot or cold food and drink can trigger intense pain,’ she adds.

On the incisors, meanwhile, MIH poses mainly aesthetic issues. ‘In front teeth, it often presents as discrete, white, yellow, brown or cream spots. They don’t crumble and break away, as back teeth do,’ says Professor Taylor.

‘But while this doesn’t affect chewing, it can impact quality of life for a child. They might not want to smile or go to school.’

And it’s not just the appearance or structural weakness of the teeth that can cause problems. Because the protective enamel is more porous, teeth affected by MIH are more vulnerable to decay and cavities, as bacteria can more easily penetrate and damage the weakened surface.

A further problem, says Professor Rodd, is that the added sensitivity can make the intensive tooth brushing required to prevent decay painful or uncomfortable.

‘Brushing a six-year-old’s teeth is difficult at the best of times,’ she adds. ‘For parents, dealing with MIH can be a minefield.’

Yet for more and more British parents, it’s their new reality.

Once considered rare, a 2021 paper from the British Society of Paediatric Dentistry (BSPD) estimated that one in eight children in the UK have some form of MIH. That figure is likely even higher today, says Professor Taylor, who led the BSPD initiative.

‘Based purely on anecdotal evidence from the patients and parents I see, I think that if we did that same study again it would now be more like one in five or six children,’ he says.

For Manchester-based mum-of-two Nicole Radley, 36, it was a shock to be told her six-year-old daughter had the condition.

‘She’d been complaining that her tooth was sore when she ate, but I didn’t think much of it,’ says Nicole.

‘We had a dentist check-up, so I brought it up then. I wasn’t expecting to be told it was caused by something that occurred when she was a baby.

‘I felt like they dropped a bombshell and walked away, leaving us to figure it all out. How do you get a child to take special care of her teeth if she doesn’t want to brush them anyway?’

Experts do have some explanation for the seemingly exponential increase in the number of MIH cases in recent years.

For a start, improvements in the dental health of British children, as well as better awareness around the condition amongst dentists, says Professor Rodd, have simply made it more visible.

‘Children’s teeth were more decayed in the past, so enamel defects were less obvious. Likewise, many dentists would have recognised a tooth was discoloured or weak, but not known to identify it as MIH,’ she explains. But increased awareness of the condition can’t fully explain the surge in cases, recent research suggests.

A 2024 paper by Swiss scientists, analysing the dental data of more than 46,000 children, found a ‘considerable’ rise in the prevalence of MIH between 1992 and 2013.

Cases of the condition in children aged six to 15 jumped from 3 per cent to nearly 20 per cent in the three-decade period, they revealed. Today, scientists across the world are racing to uncover what could be triggering the disease – and have so far pointed to a range of culprits, from environmental pollutants to childhood illnesses.

Some studies have linked the condition to a vitamin D deficiency in early childhood, while others have found a tenuous connection between enamel damage and exposure to certain toxic chemicals.

Illnesses such as chickenpox, measles, recurrent ear infections and even the common cold could also impact a child’s tooth development if they cause a high fever before the age of two, research has found. But experts say one of the best-evidenced theories is also one of the most concerning.

Recent research has found a strong link between difficult births and MIH – with children born via emergency C-section nearly 1.5 times more likely to develop the condition than children who were born vaginally.

Emergency C-sections in Britain, meanwhile, have surged to an all-time high, making up roughly one in four births.

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The reason for the possible link, says Professor Taylor, is because the cells responsible for making tooth enamel – which form in the womb and continue to calcify around the time of birth – are uniquely sensitive to stress.

‘Babies starved of oxygen for even less than a minute – usually due to a difficult labour – will see changes to their teeth in later life,’ he explains. ‘We know that there’s a good correlation there.’

But, he urges, it’s not a question of parental choice or blame. ‘There’s definitely a sense of parental guilt around the condition, which is unfounded,’ he says.

‘We still don’t know enough about MIH to go back in a child’s life and pick out what caused it.

‘Often there’s no clear event or illness at all. It’s simply not in a parent’s control. Instead, the emphasis needs to be on how to recognise and manage it.’

In the meantime, say experts, parents must learn to recognise the signs of the condition early, as prompt diagnosis could help prevent lifelong dental problems.

‘Parents need to be aware of what MIH looks like on a child’s teeth – and get them to a dentist as soon as possible to reduce the risk of further decay,’ says Professor Rodd.

Signs to look out for include any sort of discolouration on a child’s teeth – whether a slight patch of yellow or even an unnaturally bright white, she explains. ‘I often describe it as a popcorn tooth – yellow, brown or white mixed together,’ she says.

Children complaining of toothache or soreness, particularly when chewing or brushing their teeth, can also be a sign of MIH.

Treatments depend on which teeth are affected and the extent of the damage. For crumbly back molars, the best method is often extraction – particularly in severe cases, where teeth are already damaged.

‘If a tooth is unrestorable, they’re better off coming out. And if you do it early enough – around the age of nine – the space will close by itself as the back teeth naturally move,’ says Professor Rodd.

If a case is milder – or a child or parent is against extraction – the tooth can be protected with fillings, crowns and protective coatings.

But while early action is essential when treating back teeth with MIH, when it comes to front teeth the best practice is often to leave treatment until a child is a little older – around their teens.

‘We usually wait until a child is older to mask MIH on the front teeth – whether that’s white fillings over the tooth, or a whitening procedure – as the gums don’t fully mature until 20,’ says Professor Taylor.

‘With any treatment for MIH, it’s about trying to make sure patients have got no pain, a good quality of life and a good aesthetic outcome.’

While treatments for the condition have come on in leaps and bounds in the past few decades, experts hope that ongoing research will one day find a way to prevent MIH from developing in the first place.

In the meantime, increasing awareness should help both dentists and parents pick it up quicker, says Professor Rodd.

‘The message is that it’s a very common condition that can have big consequences,’ she says. ‘You just need to get in there early and give the teeth that extra looking after.’

Kat Storr’s son Ollie was seven when she noticed one of his molars was a strange orange-brown colour.

At first, journalist Kat, 41, suspected too much sugar or poor brushing, especially as his other teeth seemed healthy.

But when Ollie began complaining of pain and sensitivity while eating or brushing, she knew something was up.

It was only when she took him to the dentist that she learned of the condition molar incisor hypomineralisation (MIH).

Mother-of-three Kat, of Tooting, south London, says: ‘I was asked if I’d been ill in pregnancy or had done anything which could have caused poor development of Ollie’s teeth in utero. I racked my brain but couldn’t think of anything. It left me feeling responsible for the tooth damage and incredibly guilty.’

Today, after learning more about MIH, Kat knows that the dentist’s line of questioning was unfair as experts are still unsure why the condition occurs.

Ollie, pictured right with Kat, is now nearly ten and set to have two molars removed under general anaesthetic.

Kat says: ‘I was worried more of his adult teeth would be affected as they’ve come through, but they all seem fine so far.

‘I’m still frustrated though, that we don’t know what caused this.’