Molar incisor hypomineralisation (MIH) affects nearly 30% of Scandinavian children, yet outside specialist dental circles it remains remarkably unknown – and, even within them, is frequently misdiagnosed. The condition, almost as common as tooth decay, leaves permanent teeth permanently weakened and discoloured, but its causes and triggers are still only partially understood.
What is MIH?
MIH is a developmental defect of tooth enamel. In a healthy child, enamel – the hardest material in the human body – forms a dense, highly mineralised outer layer over the crown of each tooth. But in children with MIH, something goes wrong during the critical window of enamel formation, which occurs from around birth until roughly the age of two, while the teeth are still developing inside the jaw. The enamel that emerges is softer and contains far fewer minerals than normal. This disruption means the affected teeth are structurally compromised before they ever break through the gum.
The consequences are wide-ranging. Because the enamel is weaker, it chips, crumbles or breaks away easily – particularly in the first permanent molars, the so-called six-year molars, which bear heavy chewing loads. The teeth often appear discoloured, with patches that can be white, creamy, yellow or brown. This is most obvious on the front incisors and can affect a child’s self-esteem. The compromised enamel also makes teeth painfully sensitive to hot, cold and sweet foods and drinks, and even to brushing. This sensitivity can lead children to avoid cleaning the affected teeth, increasing the risk of rapid decay. According to researchers at the University of Copenhagen’s dental hospital, MIH typically affects the first permanent molars and the incisors – the teeth that erupt around age six or seven. In some cases, baby molars can also be involved, which may signal a higher likelihood that the adult teeth will be affected too.
MIH is not caused by poor oral hygiene, sugar consumption or any other dietary habit. It is a developmental condition, and its exact origins remain a puzzle. Current research points to five possible contributing factors: prolonged illness in early life – such as fevers, infections or repeated periods of illness; long-term use of antibiotics; complications during pregnancy or birth, including oxygen deprivation or premature birth; environmental factors like air pollution; and nutritional deficiencies, for example of vitamin D, which can impair the body’s ability to form strong enamel. There is also evidence of a genetic vulnerability, meaning some children may simply be more susceptible than others. Importantly, the condition is not preventable with current knowledge. As the University of Copenhagen team puts it, “as parents, there’s nothing you can actually do to stop the condition from occurring.”
What can parents do?
Although MIH cannot be prevented, parents can take practical steps to limit the damage. Brushing twice a day with a fluoride toothpaste is vital, because the softer enamel is harder to keep clean and far more prone to cavities. For older children, dentists may recommend a high-fluoride toothpaste (1450 parts per million or more) or a fluoride mouthwash. Toothpastes containing stannous fluoride have also been shown to help reduce sensitivity. Limiting sugary foods and drinks to mealtimes is important, as affected teeth decay rapidly. Equally crucial is helping a child build a positive relationship with the dentist. The University of Copenhagen team advises speaking positively about what dentists do – namely, helping to protect teeth so they do not hurt or break – and encouraging the child to say exactly where and how a tooth hurts.
What can the dentist do?
Dental treatment for MIH depends on the severity of the condition and which teeth are affected. Dentists classify affected molars as mild, moderate or severe. For mild molars, concentrated fluoride gel or a transparent plastic sealant is applied to protect against cavities. Moderate molars receive temporary fillings, and because the affected tooth is very sensitive, anaesthesia is needed. Severe molars require fillings, and in the most serious cases a stainless steel crown – a foil cap that shields the tooth from breaking, decay and pain. In rare cases, if the long-term prognosis is too poor, the dentist may recommend extraction, typically performed between the ages of eight and ten.
Front incisors usually have only mild to moderate MIH and are often left untreated initially. When children grow older and seek aesthetic improvements, treatment may involve whitening combined with a newer technique called resin infiltration. In this procedure, a thin, fluid resin is infiltrated into the porous enamel, filling the empty spaces and making the discolouration disappear, leaving the tooth with a normal, smooth crown colour. For severely affected molars in adulthood, a crown or porcelain inlay may be beneficial. Additional treatments for incisors include microabrasion, where an acidic polishing paste removes a thin layer of discoloured enamel, and white fillings to mask patches. More invasive options such as composite bonding or porcelain veneers are generally reserved for adult cases.
MIH also presents challenges for dentists. The weakened enamel can make it difficult to achieve effective local anaesthesia, and the porous surface can make bonding of dental materials less reliable. Diagnosis itself is not always straightforward: MIH can be mistaken for fluorosis, amelogenesis imperfecta or general enamel hypoplasia. Regular check-ups with a dentist who specialises in children’s dentistry are therefore crucial for early detection and monitoring.
Research also suggests that MIH is often accompanied by other dental anomalies. One study found that 29% of children with MIH had an associated anomaly – including congenitally missing teeth (hypodontia) in 12% of cases, ectopic first permanent molars in 8%, and infraocclusion of primary molars in 9%. This finding has important implications for treatment planning, as the presence of multiple anomalies can complicate care.
Despite its prevalence – affecting between one in eight and one in five children in the UK, according to estimates, or around one million children – MIH remains under-recognised. Studies in the UK have recorded prevalence rates ranging from 10% to 20%, with one figure of 15.9% in Northern England. The condition appears to be less commonly reported in Africa and Asia, though researchers suspect this may be largely due to differences in diagnosis and recording, as well as variations in early childhood illnesses and genetic factors. As the University of Copenhagen team notes, stronger, more consistent studies and a better agreement across the profession on how MIH is diagnosed and recorded are urgently needed. Meanwhile, researchers continue to work on the most basic questions: what are the key triggers, and why do some children develop MIH while others do not?
