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Posterior cross-bites can occur as a result of teeth being deflected either buccal, or lingual/palatal to their correct position in a Roman arch form. The second cause is an under developed maxilla, a skeletal posterior cross-bite. Some patients have both problems, and the dental cross-bite is usually corrected first in the sequence of therapy.
Posterior Dental Cross-Bite
The posterior dental cross-bite is diagnosed by evaluating the teeth in cross-bite, relative to their position in the poster force plane of the Roman arch. Attachments are placed on the involved teeth to retain the 3/16” – 4 1/12oz elastics. Separating elastics are placed mesial and distal to the teeth actually in the cross-bite.
Posterior Skeletal Cross-Bite
The posterior skeletal cross-bites requires a rigid orthopedic appliance to develop the transverse width of the maxilla. These skeletal cross-bites are most often seen with the mandible deviated ipisi lateral to the quadrant in cross-bite. This deviation creates the illusion the cross-bite is unilateral, when it is bilateral.
The lower arch will functionally increase in width as the maxilla is developed. This is either allowed to occur, or anchored using a lower retainer.
Posterior cross-bites should be corrected as soon as they are diagnosed. This allows the child to resume a normal growth pattern.
Early Correction of Cross-Bite