Many parents first learn about six-year molars when a dentist points one out and mentions that it is permanent. These four large teeth usually come through at around six or seven years of age, right behind the last baby molars, and no baby tooth is lost to make room for them. Because nothing wobbles or falls out, they tend to arrive unnoticed, and that is exactly why they are so often the first adult teeth to decay.
They come in behind the baby teeth, not in place of one
Most adult teeth take over a space left by a baby tooth. The first permanent molars are different. The Sydney Children's Hospitals Network describes them coming through at about six years of age, behind the baby molars. There is one in each corner of the mouth, two upper and two lower.
The timing varies. Some children have them before their sixth birthday and others closer to seven. Since they arrive while a full set of baby teeth is still in place, it is easy to assume they are baby teeth too and will be replaced later. They will not. A six-year molar is meant to last for life, and it does a large share of the chewing for decades.
A simple habit helps: from about age five, lift your child's cheek during brushing and look behind the last tooth on each side. A small patch of white tooth breaking through the gum is the molar on its way.
Why these teeth decay so readily
The biting surface of a molar is not flat. It is folded into pits and narrow grooves called fissures, and on a newly erupted tooth these can be deep. Plaque and food settle into the bottom of those grooves where bristles struggle to reach.
Position adds to the problem. A molar that is only partly through the gum sits lower than the teeth in front, so a toothbrush tends to skate over it. Newly erupted enamel is also still maturing for a while after it appears. Put together, a young molar in a hard-to-reach spot, with deep grooves and immature enamel, is a common place for decay to start in school-age children.
Sealing the grooves
A fissure sealant is a thin, flowable coating that the dentist or OHT bonds into the grooves of a molar. It does not involve drilling or an injection. Once set, it smooths over the fissures so plaque has fewer places to hide.
The evidence for resin sealants on first permanent molars is reasonably strong. A 2017 Cochrane review led by Ahovuo-Saloranta pooled trials in children aged 5 to 10 and found that sealed molars developed far less decay over two years than unsealed ones. As an example from the review, where about 40% of unsealed surfaces would decay over that time, sealing would bring that down to around 6%. The protective effect continued at longer follow-up, though with fewer studies.
Sealants work best once the biting surface is fully through the gum and can be kept dry while the material is placed. They need checking at regular visits, because a sealant that chips or wears can be topped up. Our guide to dental sealants for children goes through placement and how long they tend to last.
Brushing that actually reaches them
Young children rarely have the coordination to clean the back teeth on their own. The Better Health Channel notes that children can usually brush well by themselves at about eight years old, so until then a parent's help still counts for a lot. Bring the brush in from the side, angle the bristles onto the biting surface of the back molar, and use small scrubbing movements. A brush with a small head makes this easier.
Under Australian guidance, children aged 18 months to six years use a smear of low-fluoride children's toothpaste, and from six they move to a pea-sized amount of standard fluoride toothpaste (Australian Dental Association, teeth.org.au). Since the six-year molars arrive at about the same age, this is a natural time to make that switch. Our guide on how much fluoride toothpaste children need covers the amounts by age.
When the new molar looks chalky or discoloured
Some first molars come through with creamy, yellow or brown patches, or enamel that seems soft and breaks down soon after eruption. This is often molar incisor hypomineralisation (MIH), where the enamel did not mineralise fully as it formed. It is common: a 2018 review by Schwendicke and colleagues in the Journal of Dentistry estimated it affects about 13% of children worldwide, roughly 1 in 8.
Affected molars can be sensitive to cold and brushing, which makes children avoid cleaning them, and they can decay quickly. If a new molar looks patchy, it is worth having it checked early so it can be protected with fluoride, sealants or a protective filling as needed.
Early decay does not always mean a filling
When decay is caught early, before it forms a hole, a dentist may be able to slow or stop it with fluoride varnish and better cleaning. In suitable cases, silver diamine fluoride can be painted onto an early lesion to help arrest it, without drilling. It does stain decayed areas black, which matters less on a back molar but should be discussed first. Our article on silver diamine fluoride explains how it is used.
Discomfort as they come through
Erupting molars can make the gum tender for a few days. Some children chew on their fingers, rub the cheek or are off their food for a short time. Gently rubbing the gum with a clean finger, or offering something cool to chew, usually helps. Pain that persists, swelling of the face or gum, or a fever are not normal parts of a tooth coming through and should be checked.
Common questions about six-year molars
Will my child lose these teeth later?
No. Six-year molars are permanent teeth. If one is lost to decay, there is no replacement coming.
When should they be sealed?
Usually once the biting surface has fully erupted and can be kept dry, which for many children is within a year or so of the tooth appearing. Your dentist or OHT can advise on timing at a check-up.
My child has had no decay in baby teeth. Do the molars still need attention?
A good record with baby teeth is encouraging, but the new molars bring deep grooves that did not exist before. A check soon after they appear is still worthwhile.
Booking a check for new molars
At Lumi Dental, our oral health therapists Sabrina Tran and Jennifer Nguyen see children and families, with a focus on prevention, and eligible children can be bulk billed under the Child Dental Benefits Schedule. If your child is around the age for their first adult molars, you can book a visit online or see family offers on our current deals page. If it will be their first dental visit, our guide to a child's first dental visit may help you prepare.
