Chalky Teeth (MIH): Why Some New Teeth Come In Soft, Spotted or Sensitive

"Her new back tooth only just came in, and it already looks yellow and is breaking. We brush every night. What did we do wrong?" Parents who say this are often surprised by the answer: probably nothing. These may be chalky teeth, a condition dentists call MIH (molar incisor hypomineralisation). It is more common than many parents think, and early care can make a real difference.

What is MIH?

In MIH, parts of the enamel, the hard outer layer of the tooth, did not harden properly while the tooth was forming inside the jaw. The affected enamel is softer and more porous than normal. The tooth comes in with this weakness already built in.

It usually affects:

• The six-year molars, the first permanent back teeth, which appear around age 6. One, two, three or all four may be affected, often to different degrees.
• The front adult teeth (incisors), sometimes, usually more mildly.

Some children have similar chalky patches on their baby back molars, and this can be an early hint to keep a close eye on the adult molars when they arrive.

What does it look like?

• White, cream, yellow or brown patches with clear edges, which look like part of the tooth rather than a stain on it. Yellow and brown patches are often weaker than white ones.
• Chalky, crumbly enamel that can chip or break down soon after the tooth comes in, sometimes leaving rough or sharp areas.
• Sensitivity to cold drinks, air, or even a toothbrush. Some children avoid brushing one side, or chew only on the other.

MIH is different from early decay, which usually starts as a chalky line near the gum, and from fluorosis, which tends to look like faint, even white streaks. A dentist can usually tell them apart.

Why does it happen?

The honest answer is that the cause is not fully understood. These teeth form from around birth to about age 3, and researchers suspect that things affecting a child during that early window may play a part, such as serious illness or high fevers in early childhood, problems around birth, and possibly genetic factors. Research is ongoing.

What we do know: MIH is not caused by poor brushing, sweets or anything parents did or didn't do. You could not have prevented it, and there is no need to feel guilty.

Why it matters

• Faster decay: porous enamel lets bacteria in more easily, so cavities can form and grow quickly.
• Breakdown: chewing forces can make weak enamel crumble.
• Harder to numb: affected teeth can be more sensitive, and local anaesthetic sometimes works less well than usual. Dentists plan for this with extra care and patience.

What helps

1. Check the six-year molars early. Look at the back teeth every few weeks from around age 5, and book a visit when they appear, especially if you see patches or your child mentions sensitivity.
2. Fluoride varnish, applied by the dentist, can help strengthen the enamel and reduce sensitivity. It may be repeated more often than usual.
3. Sealants or protective coatings can cover the grooves and weak areas, sometimes even before the tooth is fully through.
4. Desensitising toothpaste, or a special tooth-strengthening paste, may help, but use it only as your dentist advises for your child's age.
5. Protective fillings or crowns may be needed if a tooth starts breaking down. For badly affected molars, a crown can protect the tooth and make it far more comfortable.
6. Orthodontic planning in severe cases. Occasionally a molar is too damaged to keep long term. The dentist and orthodontist may then plan the timing of its removal so the teeth behind can move forward and fill the space.

Practical tips at home

• Brush with lukewarm water if cold water makes your child flinch.
• Use a soft, small-headed brush and keep brushing the sensitive side gently. Skipping it makes decay more likely.
• Spit, don't rinse after brushing, so the fluoride stays on the teeth.
• Limit how often sugary and acidic snacks and drinks are taken.
• Keep regular check-ups, often more frequent than every six months for these teeth.