Mysterious disease in children's teeth: MIH
Dental health is a major issue in this country. Mothers' and fathers' counsellors and school dental care instructors focus on children's dental care from kindergarten age. As a result, the incidence of tooth decay among schoolchildren in Switzerland has been reduced by 90 per cent over the past 40 years.
But there is no time to rest on one's laurels. On the contrary: a new enemy is spreading in children's mouths - molar incisor hypomineralisation, or MIH for short. If a child is affected, their first permanent molars have not been properly mineralised.
The enamel is often brittle or missing completely. Molar teeth become stained and crumbly, sometimes even primary school pupils need steel crowns. And all this in otherwise completely healthy teeth.
MIH was first described in 1987, and a good 15 years later around five per cent of children were affected. According to current studies, 20 per cent of children in Germany now suffer from MIH, and according to the Oral Health Study, almost 30 per cent of 12-year-olds are affected by this structural anomaly.
The figures vary greatly as the studies are very heterogeneous. In addition, an untrained eye can confuse caries with MIH - and vice versa.
Read on to find out more about this mysterious dental disease.
One to two MIH patients per day
Switzerland is one of the few countries for which MIH statistics are not yet available. «However, based on our findings, we can assume an infestation similar to that in neighbouring countries, i.e. between 7 and 20 per cent,» says Hubertus van Waes, Head of Paediatric Dentistry at the University of Zurich.
Richard Steffen, dentist in Weinfelden, says: «We get a lot of referrals for MIH treatments, I have one or two small patients with this problem almost every day.»
Norbert Krämer is President of the German Society for Paediatric Dentistry. In recent years, he has also increasingly pulled out children's ailing molars in his dental chair or tried to save what can be saved.
The pictures he shows look as if caries bacteria have been running riot on a tooth for years without being stopped: rough and porous, fissured in places. In other photos, the molars have yellow-brown spots, but otherwise look intact and, above all, smooth. These are the lucky patients - those in whom the MIH is only slightly pronounced.
The causes are unknown
«We differentiate between three degrees of severity: mild, moderate and severe MIH,» says Krämer. «In the first two forms, patients have no symptoms - the problem here is primarily aesthetic in nature.» And this is usually only the case if the front teeth are affected in addition to the molars.
However, the severe form of MIH brings with it a whole range of difficulties. Not only do the teeth crumble and break off in places - the fissured surface cannot be cleaned properly, so caries often builds up on top of the existing MIH lesions.
Rough, porous, fissured: A tooth affected by MIH looks as if caries bacteria have been ravaging it for years.
In addition, teeth affected by MIH are often sensitive to cold, air and touch, which is why children stay away from them with a toothbrush. «If the dentist misinterprets MIH as caries and blows air through the mouth, the children go ballistic,» says Norbert Krämer.
Why is there a lack of knowledge about MIH?
Because those who graduated in dentistry five or ten years ago never heard of molar incisor hypomineralisation during their studies, there is still a lack of knowledge about this structural disorder in many dental practices today. «However, this is currently changing a lot, awareness of MIH is growing and we are organising a lot of further training on the topic,» says Krämer.
This is also important because MIH stains do not only resemble carious spots. A differential diagnosis is particularly important for affected incisors, and the parents must be questioned carefully. This is because if a milk tooth has suffered trauma at the front, has been knocked or broken off, it can injure the remaining tooth that is still in the jaw. The resulting damage can look exactly the same as the stains caused by MIH.
Meticulous oral hygiene, a sensible diet and generally taking care of your teeth are extremely important in such cases.
So far, dentists have been powerless in the face of MIH. There is no regularity: Sometimes only the first permanent molars are affected, which erupt at around the age of six, sometimes the later teeth and incisors are also affected.
Sometimes the spots are white-yellow, sometimes yellow-brown. Sometimes only the cusp of a molar is crumbly, sometimes the entire crown. Sometimes the first signs of MIH can already be seen on the milk tooth, sometimes a flawless milk tooth is followed by two completely broken molars. The doctors are at a loss: «As we don't know the cause of MIH, we have no chance of primary prevention,» says Weinfeld dentist Richard Steffen.
How can MIH be prevented?
This makes secondary prevention all the more important in order to protect the affected teeth from further damage. This includes comprehensive information for parents, regular check-ups and attempts to protect the teeth at least a little more with increased mineralisation.
«The application of a paste containing tricalcium phosphate is a very promising approach,» says Steffen. But even if MIH teeth can mature a little and mineralise a little better with a greater supply of minerals: They need four to five times as long as a healthy tooth for such a process. During this vulnerable phase, it is particularly important to treat the teeth with care.
«Meticulous oral hygiene, a sensible diet and generally taking care of your teeth are extremely important in such cases, and I always explain this to parents in great detail,» says Steffen. «Small sins that are occasionally acceptable for children with healthy teeth are even less acceptable for children with MIH teeth.» The doctors are unable to answer the shocked parents' questions about the cause of the enamel changes.
The difficult search for the perpetrator
Jan Kühnisch, a dentist at the Polyclinic for Tooth Preservation and Periodontology at the University of Munich, has been studying MIH for years and is particularly keen to get to the bottom of the cause. It is clear from the disorder that this must be sought at some point during pregnancy or in the first months and years of life.
"There are currently two main theories," says Kühnisch. One is environmental toxins, the other is antibiotics." He himself currently considers antibiotics to be a plausible explanation. Although he and his team have not been able to show a causal link between antibiotics and MIH, it is striking that the incidence of MIH was significantly higher in children who suffered from respiratory diseases - and therefore presumably received more antibiotics.
According to Kühnisch, the fact that the phenomenon of MIH was first described scientifically ten years after antibiotics were increasingly used in medicine and especially in paediatrics also speaks in favour of the antibiotic hypothesis. The fact that there are no regularities here either speaks against the antibiotic hypothesis: The researchers have seen children who have received a lot of antibiotics and show no traces of MIH, and likewise those who never receive antibiotics but have severe enamel disorders.
«I think that this is a systemic and multifactorial process,» says Kühnisch, «especially because enamel development takes place in different phases.» Kühnisch hypothesises that the cells responsible for tooth enamel may have different sensitivities in different phases: «This can change from week to week.»
The decisive factor would then be when the damaging factor comes into play. In other words: perhaps there is a time window in which the intake of antibiotics does not affect the development of enamel at all, and one in which it causes serious damage.
What role does BPA play in the development of MIH?
The second main suspect in the MIH scandal is bisphenol A, or BPA for short. This hormonally active substance made it onto the list of possible culprits thanks to a study carried out by French researchers on rats.
Jürgen Thier-Kundke from the Federal Institute for Risk Assessment (BfR) does not think it is right to attribute demineralisation to this one study, «especially as we know that rats are generally more sensitive to bisphenol A than humans». BPA is used as a starting material for plastics, including polycarbonates.
The foundations for tooth formation are already laid in the unborn child in the womb.
Interesting: Polycarbonates became popular in the 1960s and 1970s and were used to make baby bottles, among other things. Polycarbonates containing BPA have been banned in the EU for two years. «However, we checked this at the time and found that hardly any of it passes into the milk in the bottle,» says Thier-Kundke. The possibility of bisphenol A entering the child's body through breastfeeding can also be largely ruled out.
According to the BfR expert, no study has been able to detect BPA in breast milk.
Meanwhile, Jan Kühnisch in Munich has another potential enamel disruptor on the list: Vitamin D deficiency. In their cohort, the researchers measured the vitamin D level in the serum and found that a high level is associated with less MIH. «Here, too, we are still cautious about drawing any conclusions, but there does seem to be a connection,» says Kühnisch.
How a tooth is created
The development of a tooth is a lengthy and intricate process. After all, enamel, dentine, root cementum and root skin have to be created for each tooth. Both in the primary dentition and in the permanent teeth.
The foundations for tooth formation are therefore already laid in the unborn child in the womb. It all starts with the dentin. It is formed by odontoblasts. Every person has these cells throughout their life so that dentin can be reproduced. Cells called ameloblasts - or adamantoblasts - are responsible for tooth enamel.
They form the enamel in two phases. First, they secrete two proteins that form the framework for the enamel and represent a preliminary mineralisation. Then the second phase begins, the so-called maturing phase, in which the enamel is filled with salts that mineralise to form hydroxyapatite - the main component of tooth enamel. Here, the ameloblasts mainly take on transport tasks. Once they have done their job and thoroughly coated the dentin of a new tooth with enamel, they die off.
This all happens while the tooth is still in the jaw. If the finished crown then breaks through, enamel formation is complete. As there are no more ameloblasts and they cannot be formed again, the enamel can no longer be repaired. At some point during this enamel formation process, something goes wrong in children who later suffer from MIH. That much is clear. But what exactly impairs the function of the ameloblasts, whether there are too few of them or the existing ones simply cannot do their job properly - nobody knows.
