“Shark Teeth” in Kids: Why Permanent Teeth Sometimes Grow Behind Baby Teeth
In the lower front teeth, a permanent tooth pushing up behind a baby tooth that has not fallen out yet is a normal way for that tooth to arrive. Parents call it shark teeth because of the double row. In most children the baby tooth loosens over the following weeks, comes out, and the new tooth drifts forward into the space on its own.
That is the short answer, and for the lower front teeth it is usually the whole answer. But there are versions of this worth having someone look at, and they tend not to be the ones parents worry about first.
Why the new tooth comes in behind instead of underneath
Lower permanent front teeth do not develop directly beneath their baby counterparts. They form slightly toward the tongue, behind the baby tooth roots, and they travel upward along roughly that same line. So a lower permanent incisor arriving on the tongue side is not off course. It is on the course it started on.
What usually happens next is that the baby tooth’s root dissolves as the permanent tooth presses against it, the baby tooth gets loose, and it falls out. When the permanent tooth comes up behind rather than squarely underneath, some of that pressure can miss part of the root. The root holds on longer than expected, and for a few weeks your child has two teeth where one belongs.
Pediatric dental textbooks treat lingual eruption of the lower permanent incisors, which is the clinical name for this, as essentially normal rather than as a problem to correct. It shows up in children whose baby teeth were nicely spaced and in children whose teeth looked crowded, which is the part most parents find surprising.
It is usually not a crowding signal
The most common worry we hear is that the new tooth came in behind because there is not enough room, and that this means braces are coming.
The research we have does not support reading it that way. In a study of children aged five to seven and a half who had one or more lower permanent incisors erupting behind the baby teeth, most of them had adequate space, mild excess space, or only a small shortage. There was no clear relationship between how much room a child had and how the situation turned out. Whether the tooth was going to sort itself out did not track with space at all.
Permanent front teeth are genuinely wider than the baby teeth they replace, and the jaw makes up the difference as your child grows, partly by widening across the arch. This is also why gaps between baby front teeth are a good sign rather than a problem: that spacing is room the permanent teeth will use. Whether your child will need orthodontic care is a separate question answered by a full evaluation, usually around age seven, not by what the lower front teeth are doing for a few weeks at age six. Our early start orthodontics page covers what that evaluation actually looks at.
What helps at home
Wiggling is the standard advice, and the reasoning is simple: a tooth held on by a shortening root and a bit of gum comes free with repeated gentle movement. Encourage your child to work at it with a clean finger or their tongue a few times a day. Children often avoid touching it because it feels strange, and that is usually what is slowing things down.
Normal chewing helps for the same reason. Apples, raw carrots, and anything that makes the front teeth work will loosen a tooth that is ready to go.
What does not help is forcing it. Pliers, string, and hard yanking on a tooth that is still firmly attached can hurt, can tear the gum, and can leave a root fragment behind. If a tooth is not loosening on its own, that is information, not an obstacle to push through.
Keep brushing both teeth, including the tight space between them, because that gap traps food and is easy to skip when a mouth looks unfamiliar.
When it is worth having someone look
Some of these situations are worth a call rather than a wait. Bring it up if:
- The baby tooth is still firm after several weeks with no give at all, while the permanent tooth keeps coming up behind it.
- The permanent tooth has come nearly all the way in and is approaching the height of the teeth beside it while the baby tooth has not moved.
- It is happening in the upper front teeth. This one matters. An upper baby front tooth that will not come out, or upper permanent teeth arriving unevenly, is one of the situations where dentists specifically look for an extra tooth blocking the way. The lower-front version and the upper-front version are not the same finding.
- That baby tooth was injured at some point. A knock to a baby front tooth years earlier can change how and when the permanent tooth behind it comes in.
- Only one side is doing this while the matching tooth on the other side came out and was replaced months ago.
- There is pain, swelling, a bulge in the gum, or bleeding that is not just the normal ooze of a tooth coming loose.
- Nothing has appeared at all in a spot where the baby tooth came out months ago. That is a different question with a different answer.
What the exam actually involves
The visit is short. We check how much the baby tooth moves, how far the permanent tooth has come, whether the gum around it is healthy, and how the other side of the mouth compares. Comparing left to right tells us more than comparing your child to a chart.
If what we can see does not explain what is happening, or if the pattern is in the upper front teeth, an image may be useful to show how much baby tooth root is left and whether anything unexpected is sitting in the eruption path. Imaging is decided case by case here, not taken automatically because a tooth is late.
Does the baby tooth need to be removed?
Sometimes, but far less often than parents expect. In the follow-up study mentioned earlier, the large majority of children shed the baby tooth without any help at all, and fewer than one in five needed it taken out.
When removal is the right call, it is usually because the baby tooth is genuinely holding its ground and is in the way, not simply because a permanent tooth is visible behind it. Two teeth being briefly present is not itself a reason to remove one. This is a judgment call about that specific tooth in that specific mouth, which is why the answer is a look rather than a rule.
If a baby tooth does need to come out, it is a short appointment and the area is numbed first. We will walk your child through what will happen before anything starts, which for most children is the part that matters more than the procedure itself.
What this usually looks like a few months on
For most families, this resolves the way it started: on its own. The baby tooth loosens, comes out, and over the following weeks the tongue and the growing jaw bring the new tooth forward into line. That repositioning happens gradually, so a tooth that looks alarmingly far back the week it appears often looks unremarkable a couple of months later.
If you want the wider picture of how the whole transition works, our post on how children’s teeth erupt and fall out walks through the sequence from the first baby tooth to the last permanent one.
Quick answers
Are shark teeth painful?
Usually not. Children more often describe it as feeling odd or crowded than sore. Real pain, a swollen gum, or a tooth that hurts to touch is worth a call, because that points to something other than a slow-shedding baby tooth.
Will the new tooth stay crooked if it comes in behind?
In the lower front teeth, generally no. Once the baby tooth is gone, tongue pressure and jaw growth move the permanent tooth forward over the following months. That correction is gradual, so judging the final position in the first few weeks is premature.
How long should I wait before calling?
There is no exact deadline, and any dentist who gives you one is simplifying. A reasonable trigger is a baby tooth with no movement at all after several weeks while the tooth behind it keeps coming, or the permanent tooth reaching the height of its neighbors with the baby tooth still solid.
My child has this in the upper front teeth. Is that different?
It can be. An upper baby front tooth that will not shed, or upper permanent teeth arriving out of step with each other, is a recognized reason to check for an extra tooth or another obstruction in the eruption path. It does not mean something is wrong, but it does mean the situation earns a look sooner than the lower-front version.
Can I just pull it myself if it is loose?
If it is genuinely loose and your child wants it out, wiggling it free is fine. If it needs real force, stop. Firm attachment means the root is still there, and pulling against that is painful and can leave part of the root behind.
Talk to us about it
If your child has a permanent tooth coming in behind a baby tooth and you are not sure whether to wait or come in, call us at 317-580-9199 and describe what you are seeing. Often the answer is to keep wiggling and check it at the next visit, and it helps to hear that from someone who has looked at the actual tooth.
Our Indianapolis office is at 9240 N. Meridian St., Suite 250, open Monday through Thursday. You can also reach us through our contact page, or read about how we care for children at each stage on our pediatric dentistry page.
