A crossbite occurs when the upper teeth in the back of the mouth fit inside the lower teeth. The other teeth may line up correctly, however. This usually occurs when the upper jaw is too narrow. Crossbites can cause issues with chewing as the bite is not aligned properly. It is important to correct crossbites at an early age so that the upper jaw can continue to grow properly.
A crossbite is usually corrected using braces or an expander.