Crossbite explained

The two kinds

• Posterior crossbite. One or more upper back teeth bite inside the lower ones, usually because the upper jaw is narrow. Often on one side, and frequently the jaw shifts sideways on closing to find a comfortable position — a functional shift, which matters because the asymmetry you see may be postural rather than skeletal.
• Anterior crossbite. One or more upper front teeth sit behind the lower ones. Sometimes a single tipped tooth, sometimes a genuine jaw relationship where the lower jaw is positioned forward.

Why it should not be left

A crossbite concentrates force on teeth at an angle they are not built to withstand. Over years that produces enamel wear, gum recession on the affected teeth, and asymmetric loading of the jaw joint. A functional shift held for long enough can influence how the lower jaw grows in a child. None of this is an emergency, and all of it is easier to prevent than to repair.

Correction by age

Age	Approach
7–11	Palatal expander; the suture responds readily and correction is straightforward
12–15	Expansion still works, with more force and a longer stabilisation period
Adult	Bone-anchored expansion, surgically assisted expansion, or dental compensation depending on severity

A single anterior tooth in crossbite is often corrected quickly with limited braces, and catching it while the root is still forming is easier than later.

What parents notice first

A jaw that appears to slide to one side when the child bites together, wear on one side only, a chin that looks off-centre when smiling, or difficulty biting into food cleanly. Any of those is worth an examination, and expansion is covered in more detail on palatal expanders.