Baby teeth and adult teeth differ in number, size, colour, enamel thickness and root structure, and those differences change how quickly decay can cause problems. When parents ask me about baby teeth vs adult teeth, the short version is that children have 20 baby (primary) teeth, while adults typically have 32 permanent teeth, or 28 if the four wisdom teeth are not counted. Baby teeth also have enamel roughly half as thick as adult teeth, which is one reason decay can reach the nerve of a baby tooth surprisingly fast. Knowing the differences helps you spot what is normal, what is not, and when to book a check.
Key Takeaways
- Children have 20 baby teeth. Adults typically have 32 permanent teeth, including four wisdom teeth.
- The first baby tooth usually appears around 6 months, and all 20 are typically through by about age 3. Our baby teeth eruption order chart sets out the usual sequence.
- Baby teeth have thinner enamel and dentine and relatively larger nerve chambers, so decay can progress faster than in adult teeth.
- The first permanent molars arrive around age 6 behind the baby teeth, without any tooth falling out, and parents often mistake them for baby teeth.
- New adult front teeth often look more yellow than the baby teeth beside them and may have bumpy edges. Both are usually normal.
- Baby teeth hold space for adult teeth and support speech and chewing, so they are worth looking after until they fall out naturally.
Baby Teeth vs Adult Teeth at a Glance
The difference between baby teeth and permanent teeth goes beyond size. The table below summarises the main points parents tend to ask about at check-ups.
| Feature | Baby (primary) teeth | Adult (permanent) teeth |
|---|---|---|
| Number | 20 | 32 including 4 wisdom teeth (28 without them) |
| When they appear | From around 6 months, usually all present by about age 3 | From around age 6, most present by about age 12 to 13, wisdom teeth later if at all |
| Enamel | Thinner, roughly half as thick | Thicker and more mineralised |
| Colour | Whiter, often almost milky | Slightly more yellow or creamy by comparison |
| Size and shape | Smaller, with a more bulbous crown | Larger, with new front teeth often showing bumpy edges |
| Nerve (pulp) size | Relatively large compared with the tooth | Relatively smaller compared with the tooth |
| Roots | Shorter and thinner, and they dissolve as the adult tooth comes through | Longer and designed to last for life |
How Many Baby Teeth, and How Many Adult Teeth
A full set of baby teeth is 20: eight incisors, four canines and eight molars, split evenly between the upper and lower jaws. Baby teeth actually begin forming before birth.
The adult set adds teeth that have no baby predecessor. Premolars replace the baby molars, and three permanent molars on each side of each jaw grow in behind them. The third molars are the wisdom teeth, which some people never develop. That is why the permanent count is usually given as 32, or 28 without wisdom teeth.
The years when a child has a mix of both types, roughly from age 6 to 12, are called the mixed dentition stage. Gaps and teeth of different sizes and colours side by side are common during this stage.
The Six-Year Molar Mix-Up
The most common misunderstanding I see in the chair involves the first permanent molars, often called six-year molars. Around age 6, these large back teeth come through behind the last baby molar. Because no baby tooth falls out to make room for them, many parents assume they are simply more baby teeth.
This matters because six-year molars are permanent. They have to last a lifetime, yet they arrive at an age when children are still learning to brush well and the back of the mouth is hard to reach. Their deep chewing grooves collect plaque easily.
A simple way to check at home: count the teeth on one side of the lower jaw from the middle. If there are five teeth and your child is around 6 or older, the fifth tooth from the front may well be a permanent molar. Our guide to six-year molars explains what to look for and how to protect them. The second permanent molars follow around age 12 in the same way, again without any baby tooth being lost.
Enamel, Nerves and Why Decay Moves Faster in Baby Teeth
Baby teeth have thinner enamel and dentine than adult teeth, and the nerve chamber (pulp) takes up a larger share of the tooth. In practical terms, there is less protective material between the surface and the nerve. A small cavity in a baby molar can reach the pulp in a shorter time than a similar cavity in an adult tooth.
Decay in baby teeth is common. Reports from the Australian Institute of Health and Welfare have found that around 1 in 3 children aged 5 to 6 have had decay in their baby teeth. Early decay is easy to miss at home until a child complains of pain.
Parents often ask whether decay in a tooth that will fall out anyway is worth treating. In many cases it is, depending on how deep the decay is and how long that tooth still has to go. Our article on whether baby teeth cavities need treating covers the options, from monitoring and fluoride through to fillings.
Colour, Size and Shape: What New Adult Teeth Look Like
When the first adult front teeth come through, usually around age 6 to 7, many parents are surprised by how they look. The new teeth are larger and can appear more yellow than the baby teeth beside them. This is usually normal: adult teeth have thicker dentine, the slightly yellow layer under the enamel, and the whiter baby teeth beside them exaggerate the contrast.
New adult incisors also often have three small bumps along their biting edge, called mamelons. These typically wear down with normal chewing and need no treatment.
Things worth having checked include white or brown chalky patches, a tooth that looks much darker than its neighbours, or an adult tooth coming through behind a baby tooth that has not loosened. That last pattern is often described as shark teeth, and in many cases the baby tooth loosens on its own, though some children need help.
How Baby Teeth Make Way for Adult Teeth
Baby teeth do not simply fall out at random. As the adult tooth develops underneath, it presses on the root of the baby tooth above it, and that root gradually resorbs, or dissolves. Eventually the baby tooth is held only by gum and becomes loose enough to come out.
The timing varies from child to child, but the overall pattern is fairly predictable. The table below gives rough ages.
| Stage | Typical age (approximate) |
|---|---|
| Baby teeth start forming | Before birth |
| First baby tooth appears, usually a lower front tooth | Around 6 months |
| All 20 baby teeth present | Around 2.5 to 3 years |
| First permanent molars come in behind the baby teeth | Around 6 years |
| Baby front teeth loosen and adult incisors come through | Around 6 to 8 years |
| Baby canines and baby molars are replaced | Around 9 to 12 years |
| Second permanent molars come in | Around 11 to 13 years |
| Wisdom teeth, if they develop | Late teens to early twenties |
A few months either side of these ages is common. If a baby tooth is very loose but will not come out, our guide on a loose baby tooth that will not come out explains when to wait and when to come in.
Treat Baby Teeth as if They Matter, Because They Do
If there is one rule to take from the comparison of baby teeth vs adult teeth, it is this: care for baby teeth as carefully as you would adult teeth. Baby teeth do several jobs while they are in the mouth.
- Holding space. Each baby tooth keeps a gap open for the adult tooth underneath. If one is lost early to decay, neighbouring teeth can drift and reduce the room available, which may lead to crowding later.
- Chewing and nutrition. Children need comfortable teeth to eat a varied diet.
- Speech. Front teeth help children form certain sounds as their speech develops.
- Protecting the adult tooth. Infection from a badly decayed baby tooth can, in some cases, affect the developing adult tooth below it.
In practice, that means brushing twice a day from the first tooth, limiting sugary drinks and snacks between meals, and regular check-ups. From 18 months, a pea-sized amount of low-fluoride children's toothpaste is commonly recommended in Australia. For permanent molars, a dentist or oral health therapist may suggest fissure sealants to help protect the deep grooves.
Common Questions
How many baby teeth do children have?
Children have 20 baby teeth in total, 10 in the upper jaw and 10 in the lower jaw. Most children have all 20 by about age 3, though the exact timing varies.
What is the main difference between baby teeth and permanent teeth?
Baby teeth are smaller and whiter, with thinner enamel, larger nerves and roots that dissolve so they can fall out. Permanent teeth are larger, more mineralised and meant to last for life.
Why do my child's new adult teeth look yellow?
New adult teeth usually look more yellow because they have thicker dentine under the enamel, and they are being compared with very white baby teeth. If one tooth looks very different from the others, it is worth having it checked.
Should sealants go on baby teeth or adult teeth?
Sealants are most often placed on permanent molars, particularly the six-year and twelve-year molars, because their deep grooves are prone to decay. In some cases a dentist may suggest them on baby molars too. Our guide to dental sealants for children explains how they work.
How much toothpaste should a child use?
From 18 months, a pea-sized amount of low-fluoride children's toothpaste is commonly recommended in Australia, with the child spitting rather than rinsing afterwards. Our article on children's fluoride toothpaste amounts covers the guidance by age.
Children's Check-Ups at Lumi Dental, Melrose Park
Regular check-ups let the team track the change from baby teeth to adult teeth, pick up early decay, and spot the six-year molars before they become a problem. At Lumi Dental, our oral health therapists work closely with children and families, and the practice accepts the Child Dental Benefits Schedule (CDBS) for eligible children. Families from Melrose Park, Ryde, Parramatta, Ermington and Rydalmere can learn more about our general dentistry services or see our current deals for check-up options, with a written quote provided after an examination if treatment is needed.
