The short answer to this question is that if the tooth is lost at the time in the child’s life when it is generally expected to fall out, the new tooth could appear in as soon as a week, or as long as six months. If the tooth is lost due to fracture or decay, this premature loss could mean that it will take longer for the adult tooth to come in.
In rare cases, other baby teeth or permanent teeth might interfere with the desired adult tooth’s ability to break through the gums. If this is suspected, an x-ray can confirm the problem. In most instances, though, the adult teeth will come through when they’re supposed to.
The tooth transition phase usually starts around age six, and by the time the child reaches 12-13, the permanent teeth should be fully in place. When the baby teeth, also known as deciduous teeth, are gone, there should be 32 permanent adult teeth. Baby teeth will usually fall out on their own, so it’s not necessary to extract them.
Many parents obsess needlessly during the transitional phase. Frequently, the permanent teeth will come in crooked, and a parent may rush unnecessarily to an orthodontist. It’s worth noting that the transitional period is often referred to as an “ugly duckling” phase for just such reasons, and it often is just that—a phase. Most of the time the teeth will straighten out on their own. Once all the teeth have come in, and the dentist is satisfied that the child’s jawbones are not going to develop any more than they have already, that would be the time to consider whether the child is going to require orthodontic treatment.