Dental crossbite is a term for abnormal occlusion of the teeth in a transverse plane. It can also be used to describe the reversal of position of vertical overlap between upper and lower teeth. Generally, cross-bites are caused due malposition of one or more teeth which interferes with opposing tooth in the dental arch. The crossbite may include anterior or posterior teeth and could be skeletal, dental or functional in origin.
Anterior crossbites result from displacement of maxillary incisors towards the palate in relationship with the mandibular anterior teeth. It may be associated with an extra tooth and eruption of the teeth in abnormal positions. Posterior crossbites are seen when one or more teeth in the dental arch are not in alignment, leading to lack of co-ordination in lateral dimension. The condition can be unilateral (one-sided) or bilateral (affects both sides).
Another variation of posterior cross bite is termed as ‘scissor bite’, where maxillary posteriors occlude with mandibular teeth in a direction towards the cheeks. The skeletal forms of crossbite are associated with discrepancies in the development of maxilla and mandible. It may be inherited or may result form defective embryological development. It can also be seen in cases with excessive mandibular growth with narrow maxilla. Functional crossbites are seen in patients exhibiting a pseudo class III malocclusion, with habitual forward placement of the mandible.
- The persistence of a milk tooth often results in palatal displacement of its permanent successor leading to an anterior crossbite.
- Crowding of the teeth and abnormal displacement of the teeth due to various reasons can also lead to dental crossbites.
- Certain oral habits are frequently associated with crossbites including thumb sucking and mouth breathing. In patients with abnormal muscles force and tongue movements, narrowing of upper dental arch may take place leading to posterior crossbites.
- Retarded development of the maxilla or forwardly positioned mandible can also lead to posterior cross bites.
- Congenital defects leading to collapse of maxillary dental arch such as cleft palate can cause crossbites.
- Any disorders or syndrome affecting unilateral growth of the face and the jaws.
In a developing anterior crossbite, tongue blade therapy can be used if there is sufficient space for the tooth to be brought out. The blade is made to rest on the mandibular tooth in crossbite and acts as a fulcrum. The patient is asked to rotate the oral part of the blade upwards and forwards. This is continued for 1 to 2 hours for about 2 weeks.
Other commonly used orthodontic appliances to treat anterior crossbites include Catlan’s appliance or lower anterior inclined plane, Z spring (double cantilever spring) and fixed mechanotherapy using multi-looped arch wires. The skeletal form of crossbites can be treated by using reverse head gear (protraction face masks) causing protraction of maxilla.
Posteriors crossbites can be treated using cross elastics. Coffin spring, quad helix are few other intra-oral appliances used. The removable type of appliance used is acrylic plates containing jack screws. Bilateral skeletal crossbite along with a narrow deep palate can be treated by rapid maxillary expansion treatment.