Many parents only find out about the twelve-year molars when a child complains of a sore gum right at the back of the mouth, with no wobbly tooth anywhere in sight. That is because these teeth do not replace anything. They are the second permanent molars, they push up into empty gum behind the six-year molars, and according to the Australian Dental Association's teeth.org.au eruption chart, they usually arrive at about 11 to 13 years for the lower teeth and 12 to 13 for the upper.
Where they fit among the adult molars
An adult can have up to three molars on each side of each jaw. The first permanent molars, the six-year molars, come through at about 6 to 7. The second molars follow around the start of high school. The third molars, or wisdom teeth, usually appear somewhere between 17 and 21, if they come through at all. None of the three replaces a baby tooth; each one adds to the row at the back.
| Permanent molar | Usual age of eruption (teeth.org.au) | Replaces a baby tooth? |
|---|---|---|
| First molar (six-year molar) | About 6 to 7 | No |
| Second molar (twelve-year molar) | Lower about 11 to 13, upper about 12 to 13 | No |
| Third molar (wisdom tooth) | About 17 to 21, if present | No |
A few months either side of these ages is normal. Our guide to six-year molars covers the first set, and the eruption order chart can help if you are not sure whether a back tooth is a baby molar or a permanent one.
Deep grooves at the back of the mouth
The chewing surfaces of molars are not flat. They have pits and narrow grooves, called fissures, that are often too narrow for toothbrush bristles to reach the bottom. Food and plaque settle into them easily, and the twelve-year molars sit in the hardest place to reach, behind every other tooth. At the age they arrive, many children are brushing on their own with less supervision than before, and the very back teeth are often the ones that get missed.
A partly erupted molar is harder again to clean, because a flap of gum can cover part of the biting surface for weeks or months while the tooth comes through.
Sealants are the main extra protection
A fissure sealant is a thin coating that a dentist or OHT flows into the grooves of the molar once enough of the tooth is above the gum to keep it dry. It smooths the surface so plaque has fewer places to hide. Applying one is quick and usually needs no drilling or injection.
The evidence is reasonably strong. A 2017 Cochrane review (Ahovuo-Saloranta and colleagues) of 38 trials involving 7,924 children found moderate-quality evidence that resin-based sealants on the chewing surfaces of permanent molars reduced decay by between 11% and 51% compared with no sealant over 24 months, with similar benefit seen up to 48 months. Sealants need checking at regular visits, because a chipped or partly lost sealant can be topped up.
Not every molar needs sealing. The dentist or OHT will look at the depth of the grooves, how well the teeth are being cleaned, and the child's history of decay. Our article on dental sealants for children explains how they are placed. Eligible children may be bulk billed for basic care, which can include sealants, under the Child Dental Benefits Schedule.
Daily habits that protect the new molars
- Brush twice a day with standard fluoride toothpaste, which is recommended from age 6.
- Angle the brush towards the very back and give the last tooth on each side a few extra strokes.
- A brush with a smaller head can reach behind the molars more easily.
- Keep sugary snacks and drinks, including sports drinks, to mealtimes where possible.
- Check the back teeth occasionally, even if your child brushes on their own.
Sore gums while they come through
Some children notice nothing; others have a tender, slightly swollen gum and prefer to chew on the other side for a few days. Gently cleaning the area and rinsing with warm salty water can help, and children's pain relief can be used as directed on the pack if needed.
See a dentist if the gum over the tooth becomes very swollen or painful, there is a bad taste or discharge, your child has a fever, or it hurts to open the mouth. Food trapped under the gum flap can cause inflammation that needs attention.
Questions parents ask
My child is 14 and the molars are not through. Should I worry?
Eruption timing varies, and a few months late is common. If a molar seems well overdue, or one side has come through and the other has not, a dentist can check with an examination and an X-ray if needed.
Are sealants worth it if my child has never had a filling?
A child with no decay may still have deep grooves that are hard to clean. The dentist or OHT will weigh the shape of the teeth and the child's risk before recommending one.
Can a twelve-year molar be mistaken for a wisdom tooth?
Sometimes, especially in teenagers. An X-ray shows which teeth are present and whether wisdom teeth are developing behind the second molars.
Check-ups for growing teeth
A check-up around the time the twelve-year molars arrive is a good chance to look at the new teeth, discuss sealants and see how brushing is going. Our oral health therapists and dentists see children and families at Lumi Dental in Melrose Park, and you can see the current offers for new patients.
This article is general information and not a substitute for personal dental advice. Please see a dentist for care tailored to your child's situation.
