Dental health: what is dental hypomineralization, which affects one in five children in France?

Molar-incisor hypomineralization (MIH) is a malformation of tooth enamel due to a lack of minerals during its formation. It affects children's permanent (definitive) teeth, primarily molars, but also, in the most severe cases, incisors.

"Teeth affected by hypomineralization show visible abnormalities, creamy stains ranging from white to brown, and varying in extent," says Laurie Fuchs. But the concern isn't just aesthetic: a hypomineralized tooth is also more fragile. "The enamel is more porous, softer, since it has formed less well. It is therefore more permeable to external aggressions," explains the dentist. In the most severe cases, the consequences include increased sensitivity to temperature variations and sugary or acidic foods, as well as a higher risk of cavities or fractures.

2. At what age can hypomineralization occur?

"MIH only affects permanent teeth, meaning those that appear around the age of six," explains Laurie Fuchs. However, it's much earlier than that: the disorder occurs around birth and the first year of life, when permanent teeth are developing under the gums.

Are baby teeth spared? Not so simple. "If hypomineralization is observed before the appearance of permanent teeth, in baby teeth, it is not called MIH but HSPM ( Hypomineralized Second Primary Molars )," explains Laurie Fuchs. "This disorder is observed in the second temporary molars, which erupt around the age of two and a half." This pathology, similar to MIH, affects approximately 7% of children worldwide, and 9.8% in France. And while it is not necessarily a sign that the little patient will later develop MIH, it remains a risk factor to monitor.

"Today, there is no single known cause of MIH," says Laurie Fuchs. "What we do know is that everything happens between the end of pregnancy and the first year of life." According to this specialist, "what the studies show so far is that there is both a genetic predisposition, associated with triggering factors, such as problems at birth, a complicated or complicated delivery, but also the occurrence of infections with high fevers in the first months of life...". But, she specifies, "this is not systematic either, so it is impossible to establish a strict cause-and-effect link."

Concerning the impact of environmental factors, such as endocrine disruptors, sometimes put forward as an explanation for an "increase in MIH cases," caution is also advised. "Today, studies have not established a direct link," says Laurie Fuchs.

For her, the number of cases is not increasing either. "The prevalence of MIH (i.e. its frequency of occurrence in the population, editor's note) has been studied since the 1980s, but we see that in more than 30 years, it has hardly increased, it remains around 15% in the world, a little more in France. This disorder has existed for a very long time, we have even found and studied cases observed in the Middle Ages, and I think that at that time, we did not have the same problems with endocrine disruptors as today. So we cannot draw conclusions in that direction." According to the dentist, the feeling of an increase in cases could be linked to better diagnosis: "Today, professionals are better trained and informed about MIH, particularly in university courses. Since they know how to recognize it better, they have the feeling of seeing more of it." But not enough to make it a statistical truth, therefore.

"Go see a dentist for a professional opinion," advises Laurie Fuchs, who adds: "There are several causes of stains on teeth, MIH is just one of them. For example, if the molars are not affected but only the incisors, it is not MIH. And then a stain can be a history of trauma on a temporary tooth, an infection, or an isolated anomaly... If all the teeth are affected, it can also be genetic... There are many different anomalies. A dentist will be able to make the diagnosis, and above all, suggest the right treatment, because there are many ways to treat problems, whether for function or aesthetics."

Without waiting for symptoms to appear, health authorities recommend that children consult a dentist as early as possible. "Officially, it is said that a child can consult a dentist as early as their first year of life," Laurie Fuchs adds. "Social security sends out the "M'T Dents" prevention programs from the age of 3, at the age when the second temporary molars have erupted, so we can observe if there is any hypomineralization, even on baby teeth. From there, we can also put prevention in place with parents, give advice, and ensure that the slightest concern is addressed as best and as early as possible."

Several treatments are possible, from prevention to repair, depending on the damage and severity. "The idea is to have closer monitoring for children with MIH, to prevent it from damaging their teeth too much," explains Laurie Fuchs. "In daily life, this means, for example, avoiding very sticky foods, having a healthy lifestyle, and brushing teeth with fluoride-enriched toothpaste, with an age-appropriate concentration. Prevention also involves applying fluoride varnish to the teeth or sealing the grooves for protection," she explains.

In the case of cavities, "We can use a resin restoration to rebuild the tooth, but we can also place crowns or onlays, which are prosthetics that allow for a more durable reconstruction," explains Laurie Fuchs. "In cases of severe damage, we can also choose to remove certain teeth, in addition to orthodontic treatment. For example, in many adolescents, we have their wisdom teeth removed. But if some molars affected by MIH are too damaged, we can choose to remove those and move the others, provided that this is feasible given the patient's growth and compliance."

What about fluoride? Fluoride plays a protective role against cavities, but can taking fluoride—long prescribed to children as a preventative measure in tablet form—limit the consequences of hypomineralization? Yes and no, according to Laurie Fuchs. "Today, taking fluoride supplements is no longer recommended because their effectiveness is inconclusive and the risk of overdose is problematic. The only recommendation is for a dental surgeon to apply a fluoride varnish topically (to a specific area, editor's note) to the teeth of patients at high risk of caries. And when you have MIH, you're one of them."

Several research teams are working on dental hypomineralization. Among them is Professor Elsa Garot's team from the University of Bordeaux, with whom Laurie Fuchs had the opportunity to work. "Her team has developed treatment techniques that allow, when there is a significant level of tooth decay, to repair them more effectively by preserving as much of the original tissue as possible and improving aesthetics," explains the dentist.

In terms of prevention, the new dental care agreement for 3-24 year olds encourages them to consult a professional more regularly, and as a preventative measure, in order to be able to treat any pathologies as early as possible.