Why are my toddler's teeth decaying?

How it happens

The pattern dentists call early childhood caries usually follows a familiar path. A child falls asleep with a bottle or sippy cup containing juice, sweetened milk or formula. Sugary liquid pools around the upper front teeth. During sleep, saliva flow — the mouth's main defence — drops substantially. Bacteria feed on the sugar for hours, producing acid against the enamel.

The upper front teeth are usually affected first and worst, because that is where the liquid sits. It can progress remarkably fast in young children, whose enamel is thinner than an adult's.

The three main risk factors

• Sugary drinks in bottles and sippy cups — including fruit juice, which parents often assume is a healthy choice. It is high in both sugar and acid. Sipping it slowly all day is worse than drinking it at once.
• Bedtime bottles — the single highest-risk habit, for the reasons above.
• Bacterial transmission from carers — the bacteria that cause decay are not present at birth. They are commonly passed to a child through shared spoons, testing food temperature by mouth, or cleaning a dummy in your own mouth. A carer with untreated decay has more of these bacteria to pass on, which is one reason a parent's own dental health matters for their child's.

Preventing it

• Only water or plain milk in a bottle, and never sugary drinks at bedtime. Water is the only safe drink to fall asleep with.
• Move to an open cup from around 12 months, which stops the slow all-day sipping that prolongs acid exposure.
• Start cleaning before teeth appear — wipe the gums with a clean damp cloth. Once the first tooth arrives, brush twice daily with a smear of fluoride toothpaste.
• Brush for them until they have the manual dexterity to do it properly themselves, which is later than most parents expect — typically around age seven, and supervise after that.
• Do not share spoons or clean a dummy in your mouth.
• Keep juice to mealtimes and dilute it, rather than offering it throughout the day.

They are only baby teeth — does it matter?

Yes, considerably. Baby teeth hold the space for adult teeth and guide them into the correct position. Losing them early to decay can cause crowding and alignment problems that need orthodontic treatment later.

Beyond that, decayed baby teeth hurt. They interfere with eating, sleeping, speech development and concentration, and infection can affect the developing adult tooth underneath.

Current guidance is that a child should see a dentist by their first birthday, or within six months of the first tooth appearing. See when should my child first see a dentist?