kids
Shark Teeth, and Usually Nothing to Do
It is called shark teeth, it is common, and it usually resolves itself. There is one thing to do at home and one line at which it needs an appointment.
A six-year-old opens their mouth and there are two rows of lower front teeth — the baby ones still in place, and a set of adult teeth coming up behind them.
It looks alarming and it is common enough to have a nickname. Shark teeth.
What is actually happening
A permanent tooth does not push a baby tooth out from below. It dissolves the root.
The permanent tooth develops in the bone underneath its predecessor and releases signals that recruit osteoclasts — the cells that break down bone and hard tissue. Those cells eat away the root of the baby tooth above until there is nothing left holding it, and it falls out.
Which explains why a shed baby tooth is a small crown with no root and almost no bleeding.
Shark teeth happen when the timing slips. The permanent tooth erupts on schedule while the root of the baby tooth has not finished dissolving — usually because the permanent tooth came through slightly behind rather than directly beneath, so the resorption signal did not reach the root squarely.
The lower front teeth are where it happens most, and the usual age is five to seven.
Why it usually resolves itself
Two things fix it without any intervention.
The root keeps dissolving. The process is under way, just late, and it generally finishes over the following weeks.
And the permanent tooth moves forward. This is the part parents find hardest to believe, and it works because teeth are not fixed in place — each one hangs in a ligament that remodels the bone around it in response to pressure. Once the baby tooth is gone, the tongue pushes the new tooth forward into the space over weeks to months.
That is the same mechanism orthodontics uses. It is running here for free.
The one thing to do at home
Get them to wiggle it. Several times a day, with clean fingers or by pushing with the tongue.
This is not folklore. Movement accelerates resorption of the remaining root, and children who wiggle consistently lose the tooth noticeably sooner than children who leave it alone.
It also has to come from the child. A parent pulling at a tooth that is not ready is painful, frightening, and a reliable way to make the child refuse to let anybody near their mouth for the next year.
Crunchy food helps for the same reason — apples, carrots, anything that requires biting into rather than chewing.
When it needs an appointment
Four situations, and none of them is an emergency.
Still firm after about two months. If the baby tooth has not loosened at all while the permanent one has continued to come up, the root is not resorbing and the baby tooth may need removing. It is a quick procedure.
The permanent tooth fully erupted and the baby tooth completely solid.
Pain, swelling or bleeding gum around either tooth.
Or several teeth at once. One shark tooth is a timing quirk. Four is a pattern, and worth having looked at properly.
What not to worry about
Crookedness while it is happening. The permanent tooth sitting behind and looking rotated is normal at this stage and is not a prediction about the final position.
Whether this means braces later. It doesn’t, particularly. Late crowding has other causes, and a shark tooth episode at six is not a signal about anything at twelve.
And the yellowness of the new tooth. Permanent teeth are naturally darker than baby teeth — baby enamel is thinner and whiter, so a new adult tooth next to old baby ones always looks yellow by comparison. Nothing is wrong. It looks like that because it is next to the wrong reference.
The thing to keep in mind
The double row is a scheduling problem rather than a structural one. Two processes that normally overlap neatly have got slightly out of step, and the second one usually catches up.
Which makes the useful posture patient rather than urgent: wiggle it, give it crunchy things to bite, and put a date in the calendar about two months out. If the tooth is still there then, get it seen.
Most of the time it will have gone long before.
The short version
A permanent tooth has come up behind a baby tooth whose root has not finished dissolving. Common, has a nickname, most often the lower front teeth around six.
Wiggling several times a day genuinely speeds it up, and the new tooth usually drifts forward into place by itself once the old one is out.
Two months of no loosening at all, or pain, or several teeth at once — that is when it needs an appointment.
Questions people actually ask
Why does my child have two rows of teeth?
Because a permanent tooth has erupted behind a baby tooth that has not come out yet. It's common enough to have a nickname — shark teeth — and it happens most often with the lower front teeth around age six.
Will the baby tooth fall out on its own?
Usually yes, within a few weeks to a couple of months, once the root finishes dissolving. Encouraging the child to wiggle it several times a day genuinely speeds it up.
Will the permanent tooth stay crooked?
In most cases it moves into position on its own once the baby tooth is out, pushed forward by the tongue over weeks to months. Teeth are not fixed in place, which is exactly why they can correct.
When should you see a dentist?
If the baby tooth is still firm after two months, if the permanent tooth is fully through and the baby tooth has not loosened at all, if it is painful, or if the same thing happens to several teeth at once.