What causes a tooth to become impacted?

The two problems behind almost every impaction

Strip away the specifics and nearly every impacted tooth traces back to one of two things. Either the jaw simply has not left enough open space for the tooth to land where it belongs, or the tooth is aimed in a direction that does not lead cleanly into the arch. Sometimes both are true at once, which tends to make the case more noticeable when it is eventually found.

Crowding is the most familiar version of the space problem, where neighboring teeth have already claimed the room a later tooth needs. The direction problem is less visible from the outside and usually only shows up clearly on an X-ray, where a tooth angled sideways or tipped away from its intended path becomes obvious in a way it never would be from a look in the mirror.

What tends to create those two problems

A handful of situations show up again and again behind an impacted tooth. A baby tooth that has not loosened and stepped aside on its own timeline can sit directly in the permanent tooth's way. An extra tooth beyond the usual number can occupy space or block a path that would otherwise be open. Dense tissue or, less often, a small cyst near the developing tooth can do the same thing from a different direction. A jaw that is simply on the smaller side relative to the size of the teeth trying to fit into it is one of the more common underlying setups, and it often runs in families the same way tooth size and jaw size generally do.

None of these are something a parent caused or could have prevented. They are simply how a crowded or oddly angled path tends to happen.

Why canines and the last molars end up on this list so often

Upper canines take an unusually long and high route to reach the arch compared with most other teeth, which gives them more opportunity to go astray along the way. The very last molars, often called wisdom teeth, arrive after every other permanent tooth has already claimed its spot, so whatever room is left over is frequently not quite enough. Both situations are well recognized in mainstream dentistry, which is exactly why growth checks pay particular attention to these two long before either tooth is due.

When this stops being a search and becomes a phone call

An impacted tooth rarely announces itself the way a toothache does, so most cases are found at a routine visit rather than reported by a worried parent. Still, a few things are worth mentioning sooner.

• A baby canine that has not loosened at all well past when the teeth around it have
• Noticeable swelling, tenderness, or a firm bump along the gum where a tooth is expected
• A gap that is closing up on its own instead of a tooth arriving into it
• For older kids and teens, discomfort or pressure toward the very back of the jaw

None of these need same-day attention, but they are worth a call rather than more waiting. One number reaches both offices, and a real person answers: (239) 482-2722. More parent questions like this one are collected at our quick answers page.