Narrow Jaw: Causes, Crowding and Crossbite, and Ways to Widen It

The teeth sit in a curved arch. When that arch is narrow, particularly in the upper jaw, there is not enough width for the teeth, so they overlap, twist or sit behind others. A narrow upper arch can also be too small to fit over the lower teeth.

This is separate from jaw height or length. People may say small jaw to mean either the width or the whole size of the jaw. A dentist can tell which it is.

A narrow arch typically shows up as crowding, covered in our guide on crooked teeth. It can also cause a crossbite, where some upper back teeth bite inside the lower ones, and in some children the lower jaw slides to one side to bite comfortably.

Causes include inherited jaw shape and childhood habits such as long-term thumb sucking, and breathing mainly through the mouth. A link between narrow jaws and breathing or sleep problems has been discussed, but it is not simple, so if you or your child snores heavily, breathes through the mouth most of the time or sleeps badly, ask a doctor.

In children, a palatal expander is a small appliance that gently widens the upper jaw over weeks, using the fact that the bones are still growing. Braces usually follow. This is the reason an early check is advised; see the guide on the best age for braces.

In teenagers and adults the central joint of the palate has hardened. Options include braces with careful arch widening, extractions to create room in some cases, and, for a marked skeletal narrowness, surgically assisted expansion. Each carries trade-offs, and the braces and orthodontics page describes the general process.