The upper dental arch is “crossed” at certain points with the lower dental arch.
In anterior crossbite one or more front teeth of the upper jaw are behind the corresponding ones of the lower jaw. That is due to local causes or disharmony in the size of the jaws.
In posterior crossbite the upper jaw is “narrow” in range or the lower jaw is unusually wide or teeth of the upper and lower jaw are in an ectopic location that leads to the creation of a crossbite.
When the upper side is closed through the lower teeth. Usually in this case the closing of the upper middle line does not coincide with the lower causing asymmetry of the face which through years requires surgery to be corrected.
When both sides and the upper jaw come through the lower.
Treatment in crossbite should be initiated as early as possible – it can start before the eruption of permanent teeth -because otherwise the problem can be evolved into skeletal with several difficulties in its treatment.