Functional and morphological-occlusal aspects in children treated for unilateral posterior cross-bite

Morphological and functional aspects were investigated in children with unilateral posterior cross-bite (UPXB) before and after treatment. Sixty-five patients with Class I malocclusion with UPXB in the mixed dentition stage (mean age 8.8 +/- 1.6 years) served as the experimental group and 10 children of comparable age, with normocclusion or very mild Class I malocclusion (without UPXB) served as controls. The morphological aspects were examined on a longitudinal basis while the functional recordings, by means of a sirognathograph, were performed in a cross-sectional fashion. Complete elimination of cross-bite was maintained in 61 per cent and was accompanied by a dramatic reduction in the prevalence of functional mandibular displacement. However, the prevalence of mandibular midline deviation related to the maxillary midline as recorded in the intercuspal position was not affected. In addition, the high prevalence of Class II subdivision relationships which accompanied the UPXB in the intercuspal position was resolved in 50 per cent of the cases only. The sirognathographic recordings of the masticatory pattern showed a very high prevalence of a 'reverse sequencing' type pattern before treatment which was significantly lower following the elimination of UPXB, but still notably higher when compared with the controls. Reasons for these results are suggested and possible inter-relationships between the morphological and functional aspects are discussed.