Milk teeth vs permanent teeth: what parents should know

Children grow 20 milk teeth, which are gradually replaced by up to 32 permanent teeth. The two sets are built quite differently: milk teeth are whiter, have thinner enamel that lets decay spread faster, and have roots designed to dissolve as the adult teeth push through. They also do a quiet but vital job, holding the space that guides each permanent tooth into position. That is why "they will fall out anyway" is one of the costliest myths in children's dentistry, and why looking after milk teeth is the simplest way to protect your child's adult smile.

How milk teeth and permanent teeth differ

Milk teeth, also called baby or primary teeth, begin erupting when teething starts, often around six months, and a full set of 20 is usually in place by around age three. Permanent teeth replace them gradually from about age six, eventually numbering up to 32 including the wisdom teeth. The two sets are built differently: milk teeth are smaller, whiter and covered in thinner enamel, while permanent teeth are larger, slightly deeper in colour and built to last a lifetime. The table below sets out the differences that matter most for parents.

Why decay moves faster in milk teeth

Enamel is the hard outer shell of a tooth, and on milk teeth it is noticeably thinner and less mineralised than on permanent teeth. The dentine underneath is thinner too, and the nerve chamber inside is proportionally larger. Put together, this means decay that begins as a small mark on a milk tooth can reach the nerve far sooner than it would in an adult tooth. A dark spot, a chalky white patch near the gum line or a child who suddenly avoids chewing on one side all deserve a prompt dental visit rather than a wait-and-see approach.

Untreated decay in a milk tooth does not stay put. It can cause toothache, broken sleep, difficulty eating and, if infection develops at the root, swelling that needs urgent care. Because the permanent tooth develops directly beneath the milk tooth, a long-standing infection can also disturb the adult tooth forming below it. Our guide to cavities in kids explains the early signs to watch for and how small cavities are usually treated. If your child has facial swelling or fever alongside a toothache, treat it as urgent and contact a dentist or doctor the same day.

Why "they will fall out anyway" is a costly myth

Every milk tooth is a natural space maintainer. It reserves the exact spot its permanent successor needs and guides it into position when the time comes. When a milk tooth is lost early, whether to deep decay or an accident, the neighbouring teeth can begin to drift into the gap. The permanent tooth underneath then finds its path blocked or narrowed, and it may erupt crooked, come through in the wrong place or stay trapped in the jaw. What began as one neglected cavity can turn into crowding and alignment problems that take far longer to correct in the teenage years.

This is why our consultant paediatric dentist, Dr. Vanessa Lobo, who holds an MDS in Paedodontics and Preventive Dentistry, treats saving a milk tooth as the first choice wherever possible. Fillings and, where the nerve is involved, pulp treatment with a protective crown can keep a milk tooth working until it is ready to leave on its own. If a tooth genuinely cannot be saved, a simple appliance called a space maintainer can hold the gap open so the permanent tooth still has room to arrive properly.

How the changeover to permanent teeth works

Milk teeth are designed to leave. As a permanent tooth develops and moves upwards in the jaw, it presses on the root of the milk tooth above it, and the body gradually dissolves that root away. This process, called resorption, is why a milk tooth that once sat firmly begins to wobble and eventually falls out with little more than a gentle twist. The front teeth usually go first, from around age six, and the changeover continues in stages over several years. Our baby teeth eruption chart shows the typical order and timing for both sets.

Occasionally the changeover misbehaves slightly. A permanent tooth may appear behind a milk tooth that has not yet fallen out, creating a brief double row that parents often call shark teeth. This usually resolves once the milk tooth loosens and comes away, but if it stays firm for weeks after the adult tooth appears, have it checked. Likewise, if a milk tooth falls out and nothing has appeared in the space many months later, a dental visit and, if needed, a simple X-ray can confirm that the permanent tooth is on its way.

Protecting your child's milk teeth

Good habits protect thin enamel. Brush your child's teeth twice a day with a fluoride toothpaste suited to their age, using a smear for babies and toddlers and a pea-sized amount for older children, and help with brushing until they can manage a thorough job themselves. Keep sugary snacks and drinks to mealtimes, and avoid putting a baby to bed with a bottle of milk or juice. Through our paediatric dentistry service in Viman Nagar, check-ups are gentle and unhurried, and preventive options such as fluoride varnish and fissure sealants can add an extra layer of protection to vulnerable chewing surfaces.

• Brush twice a day with a fluoride toothpaste appropriate for your child's age
• Help or supervise brushing until your child can do a thorough job alone
• Keep sweets, biscuits and sugary drinks to mealtimes rather than all-day grazing
• Never settle a baby to sleep with a bottle of milk or juice
• Book the first dental visit by the first birthday, then keep up regular check-ups

Sources & further reading: NHS, Dental Health; American Dental Association (MouthHealthy); World Health Organization, Oral Health; Indian Dental Association.