Teeth: The Early Years

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Wondering when those baby teeth make their grand entrance? From in utero to adulthood, let's break it down...

In utero: first trimester: At around 6 or 7 weeks, the fetus forms a band of tissue called the dental lamina, which leads to tooth buds.

Second trimester: By week 20, the baby teeth buds are in place, and a second set of buds—for future adult teeth—begins growing too.

Third trimester: The gums become rigid by week 36. Teeth won't show for half a year, but those gums are so firm they deliver a sort of bite-lite.

Birth: Each tooth is formed, though they remain underground. Still, one in every 2,000 babies is born with a tooth showing, called a natal tooth. Such as, famously, Louis XIV; his wet nurses were not happy.

6 to 8 months: The first tooth: It's nearly always a bottom front one (the lower central incisor). Baby teeth are also called deciduous teeth because they fall out.

8 to 12 months: The top front teeth (upper central incisors) join the party. On average, a girl's teeth appear sooner than a boy's teeth.

9 to 13 months: Now come the top lateral incisors (which bookend the two front teeth).

10 to 16 months: The bottom lateral incisors crop up. Your child has a headful of eight teeth.

13 to 19 months: The first molars grow in, on top and bottom.

16 to 22 months: The pointier canine teeth surface, and the baby vampire jokes begin.

25 to 33 months: The biggest baby teeth, the second molars, rise way in the back, and the full quota of 20 baby teeth is reached.

4 years: They're all Lauren Huttons now. The gaps help adult teeth grow in evenly.

6 to 7 years: The first tooth falls out. It's usually the lower central incisor, the first to appear in babyhood. Baby teeth don't actually fall out; they're pushed out. The adult tooth below presses so hard on the baby tooth above that the baby tooth's roots dissolve and its crown has nothing to tie it down. Fairies everywhere flex their wings.

7 to 8 years: Baby teeth begin their departure in a mostly first-hired/first-fired order, starting in the middle and edging out to the nearest neighbors. Enjoy watching your child leave furrows in his pizza.

9 to 13 years: As baby teeth go, in come comically large replacements. Eight brand new ones (premolars and second premolars) take up all the extra room in your big kid's mouth.

14 to 23 years: Now it's a 28-tooth holding pattern until your child hits her early 20s and her third molars, aka wisdom teeth, come in. The epic journey from 20 baby teeth to 32 adult teeth is over. Chew on that.

* Ages are estimates, of course. The age estimates come from the American Academy of Pediatric Dentistry.