Posterior crossbite – detailed

Normal transverse relationships

In patients without a skeletal crossbite or dental crossbite, the palate has a normal width, the upper and lower buccal teeth possess normal angulations and the tongue sits up towards the palate.

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Posterior crossbite without skeletal discrepancy

This diagram is exaggerated for the illustration purposes.

A dental crossbite without skeletal discrepancy occurs when the palate (maxilla) is of normal width. Upper teeth may be tipped in and/or lower teeth may be upright causing a posterior crossbite. The crossbite can appear as a single tooth crossbite, unilateral crossbite or bilateral crossbites. See intra-oral features for details.

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Posterior crossbite with skeletal discrepancy

This diagram is exaggerated for the illustration purposes.

A skeletal discrepancy occurs when there is a narrow palate. This often occurs in transversely constricted maxillas and in those who are obligatory mouth-breathers due to chronic nasal obstruction. Notice the lowered position of the tongue. The upper teeth may naturally present in a buccally tipped position as compensation.

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Skeletal discrepancy without posterior crossbite

This diagram is exaggerated for the illustration purposes.

A skeletally constricted palate can occur without a posterior crossbite as well. The level of compensation of the buccal teeth determines if a posterior crossbite is present. In this example the upper teeth have compensated with significant buccal crown tip and the lower teeth with significant lingual crown tip.