Posterior crossbite:

The upper molars and canine of a side or both sides bite inside the lower teeth. It presents a morphological asymmetry and causes a functional asymmetry. It usually involves a malposition not only of the teeth, but also the face and the skull.

Anterior crossbite:

The inferior incisors or canines bite outside the lower teeth. It can occur in three different ways:

-Simple anterior crossbite: the crossbite affects only one or two teeth and there is enough space to correct their position in the arch.

-Functional crossbite: during the occlusion the mandible moves forward, towards the front, owing to the interference of the anterior teeth. It gives rise to a malocclusion or functional class III malocclusion.

-Complicated anterior crossbite: besides several impacted teeth, other troubles appear, such as lack of space, mandibular prognathism (real class III), and skeletal pseudo Class III malocclusion due to an underdevelopment of the jaw.