Morphological and positional asymmetries of young children with functionalunilateral posterior crossbite

This prospective clinical study evaluated the morphological and positional mandibular asymmetry of young patients with functional unilateral posterior crossbite. The sample included 9 girls and 6 boys (8.8 +/- 1.0 years of ag e), evaluated at the initiation of treatment and approximately 6 months aft er the retention phase (1.1 +/- 0.2 years after initiation of treatment). E ach patient had a complete unilateral posterior crossbite involving 3 or mo re posterior teeth, a functional shift from centric relation-intercuspal po sition, and no signs or symptoms of temporomandibular disorder. A bonded pa latal expansion appliance was used to rapidly expand the maxilla (1 month) and retain the treatment changes (6 months). Zonograms were used to assess articular joint spaces, and submental vertex radiographs were used to asses s morphological and positional asymmetry. The results showed that the mandi ble was significantly longer on the noncrossbite side than it was on the cr ossbite side. The asymmetry was most evident for the ramus and involved bot h the condylar and the coronoid processes. The posterior and superior joint spaces were larger on the noncrossbite side than they were on the crossbit e side. After treatment and retention, the mandible showed no significant m orphological asymmetries. Mandibular growth was greater on the crossbite si de than it was on the noncrossbite side, and the mandible had been repositi oned; the crossbite side had rotated forward and medially toward the noncro ssbite side. We concluded that unilateral posterior crossbites produce morp hological and positional asymmetries of the mandible in young children, and that these asymmetries can be largely eliminated with early expansion ther apy.