# Why do adult teeth move in? **URL:** \ **Category:** Factual Questions\ **Created:** [June 19, 2004, 6:46am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179 "2004-06-19T06:46:55Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Chotii](https://avatars.discourse-cdn.com/v4/letter/c/71e660/32.png) [@Chotii](https://boards.straightdope.com/u/Chotii)\ **Post date:** [June 19, 2004, 6:46am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/1 "2004-06-19T06:46:55Z")
I know that baby teeth fall out because first, the root dissolves, and second, the incoming adult tooth pushes them out. But what causes the adult teeth to grow up and in? My daughters are losing their front baby teeth and it’s a blast, watching these larger, serrated incisors push out from their gums. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [June 20, 2004, 5:24pm UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/2 "2004-06-20T17:24:23Z")
> [@](#): > > \*\*But what causes the adult teeth to grow up and in? \*\* Not sure what you’re getting at here. My initial answer would be, “Genetic programming”, the same thing that causes all juvenile organisms to progress at a particular pace towards “adulthood” and eventually “old age” and “death”. It’s genetically encoded, IOW. ---
**Author:** ![Chotii](https://avatars.discourse-cdn.com/v4/letter/c/71e660/32.png) [@Chotii](https://boards.straightdope.com/u/Chotii)\ **Post date:** [June 20, 2004, 6:41pm UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/3 "2004-06-20T18:41:53Z")
Clearly I haven’t asked the right question. I know that genetics cause these things. But what mechanism causes teeth to move in the jaw? I had braces, and making my teeth move in my jaw THAT way was a long, painful, tedious and ultimately futile ordeal (since my teeth got all messed up again when my wisdom teeth came in) But my daughters lose their teeth, and in a few weeks a new tooth just migrates in. It’s really cool to watch (and I’m sure it was cool when I was a kid, I just don’t remember it much). I’m more curious about the mechanism, how the body causes the tooth to migrate. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 20, 2004, 6:48pm UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/4 "2004-06-20T18:48:37Z")
> [@Chotii](#): > > I’m more curious about the mechanism, how the body causes the tooth to migrate. You’re talking about two entirely different and unrelated things. Adult teeth _grow_ in a child’s mouth to replace lost “baby” teeth. The aren’t migratign from anywhere, because they don’t exist until the baby tooth is lost and the adult one begins growing in. OTOH, moving teeth around with braces is simply a controlled way of doing something teeth are capable of naturally. Teeth aren’t fixed in place, but can move somewhat, to accomodate changes in dentition (such as when teeth wear down over time, or you have one pulled). Pressure from other teeth cause them to shift, so that the teeth mesh together as neatly as possible. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [June 20, 2004, 11:23pm UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/5 "2004-06-20T23:23:06Z")
> [@Q.E.D.](#): > > You’re talking about two entirely different and unrelated things. Adult teeth _grow_ in a child’s mouth to replace lost “baby” teeth. The aren’t migratign from anywhere, because they don’t exist until the baby tooth is lost and the adult one begins growing in. Actually, the adult teeth are there before the baby teeth are lost, and migrate up or down through the gums to replace the baby teeth as they’re lost. If you look at an x-ray of a child’s head you can see the adult teeth waiting to come in while the baby teeth are still in place. Look at the lower-right image on [this page](http://www.atlasorthogonal.com.au/epilepsy.html) for an example. ---
**Author:** ![Little\_Cloud](https://avatars.discourse-cdn.com/v4/letter/l/bcef8e/32.png) [@Little\_Cloud](https://boards.straightdope.com/u/Little_Cloud)\ **Post date:** [June 21, 2004, 1:25am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/6 "2004-06-21T01:25:24Z")
I don’t know the answer to your question but I know it hasn’t been answered yet. The loss of baby teeth is not what triggers the emergence of adult teeth necessarily. My middle son’s adult teeth started coming in right behind his baby teeth (like a shark) contributing to what his pediatrician calls an orthodontic nightmare. Several of his baby teeth had to be extracted. He was at the normal age for emergence of permanent teeth but the baby teeth were still dug in. ---
**Author:** ![Waenara](https://avatars.discourse-cdn.com/v4/letter/w/50afbb/32.png) [@Waenara](https://boards.straightdope.com/u/Waenara)\ **Post date:** [June 21, 2004, 1:36am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/7 "2004-06-21T01:36:37Z")
Here’s a good site with a [picutre](http://www.aboutsmiles.org/6to12.htm) showing the baby teeth (in place), and the adult teeth growing in the jaw. ---
**Author:** ![Waenara](https://avatars.discourse-cdn.com/v4/letter/w/50afbb/32.png) [@Waenara](https://boards.straightdope.com/u/Waenara)\ **Post date:** [June 21, 2004, 1:39am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/8 "2004-06-21T01:39:43Z")
Sorry, hit “Submit” instead of “Preview”. Obviously, I meant “picture”. Also, that site gives the normal timeline for eruption of adult teeth, but doesn’t mention the mechanism by which this worked. I always assumed that it was because the growing adult teeth put pressure on the deciduous (baby) teeth, and causes the root to loosen and the tooth to eventually fall out. But this is just a random guess, it could be something completely different. ---
**Author:** ![phouka](https://avatars.discourse-cdn.com/v4/letter/p/c5a1d2/32.png) [@phouka](https://boards.straightdope.com/u/phouka)\ **Post date:** [June 21, 2004, 2:38am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/9 "2004-06-21T02:38:20Z")
I had to have my left bottom cuspid pulled when I was in fourth grade, because the adult tooth was coming up underneath it, cracking the baby tooth’s enamel. As soon as the baby tooth was pulled, the adult tooth came up within a few days. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [June 21, 2004, 6:39am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/10 "2004-06-21T06:39:46Z")
> [@Q.E.D.](#): > > You’re talking about two entirely different and unrelated things. Adult teeth _grow_ in a child’s mouth to replace lost “baby” teeth. The aren’t migratign from anywhere, because they don’t exist until the baby tooth is lost and the adult one begins growing in. OTOH, moving teeth around with braces is simply a controlled way of doing something teeth are capable of naturally. Teeth aren’t fixed in place, but can move somewhat, to accomodate changes in dentition (such as when teeth wear down over time, or you have one pulled). Pressure from other teeth cause them to shift, so that the teeth mesh together as neatly as possible. Eh? Not like you, **Q**. Every kid who’s seen his/her own dental x-ray knows that adult teeth are already present below the gumline _before_ the milk tooth falls out. To answer the OP, I believe the adult tooth pushes the baby tooth out, rather than just knowing it’s time to appear when the baby tooth is gone. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 21, 2004, 6:47am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/11 "2004-06-21T06:47:45Z")
> [@Really Not All That Bright](#): > > Every kid who’s seen his/her own dental x-ray knows that adult teeth are already present below the gumline _before_ the milk tooth falls out. Yes, and I can see why I was misunderstood. I didn’t _mean_ to imply that the adult teeth only grew in after the baby teeth had fallen out. I was only trying to make a distiction between the way teeth are moved around using orthodontics and the growing of permanent teeth to replace the baby ones, adn sort of glossed over the details. FWIW, the buds for the permanent teeth begin to grow between the ages of two and three, and usually by about 4 or so are all ready to begin pushing out the milk teeth. ---
**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\ **Post date:** [June 21, 2004, 6:53am UTC](https://boards.straightdope.com/t/why-do-adult-teeth-move-in/251179/12 "2004-06-21T06:53:12Z")
I don’t know if you want a deeper genetic answer, but my guess is that the teeth remain as buds (or some sort of stem cell) for the first years of a child’s life, and either after a certain number of divisions or the detection of external hormones (maybe triggered by puberty) or some sort or external signal the buds decide it is time to grow into adult teeth.