Unilateral Angle II in functional lateralities.

The aim of this study was to explore unilateral Angle II-type malocclusion prevalences in functionally true right-sided (TRS) and non-right-sided (NRS) children having one or more left-sided functions (eye, hand, foot). A half cusp sagittal relationship of the upper and lower M1 and Dm2 was determined on dental casts of 1423 young American black and white children in a cross-sectional sample with the mean age of 8.5 years (range 6-12 years). Hand, foot and eye preferences were recorded at the age of 4 years during the Collaborative Perinatal Study. The prevalences of symmetric bilateral Angle I and II and asymmetric unilateral Angle II right and Angle II left cases were compared between TRS and NRS children using Chi-square analysis. In general, unilateral Angle II right occurred in 9 per cent of the population and Angle II left in 6.5 per cent. In moderate non-right sideness (two-thirds of left dominant functions), these proportions were 17 and 3 per cent, respectively, and in true right sidedness 8 and 6 per cent, respectively. TRS subjects were more symmetric (bilateral Angle I or II in 85 per cent of cases) than NRS children (80 per cent), and the differences were statistically significant (P < 0.02). These results highlight the anatomical relationships of structures supporting the occlusion and the symmetry/asymmetry of the neurocranium, cranial base, masticatory apparatus, and probably also the sidedness and the growth-stimulating effect of lateralized jaw function. Based on the results and considering earlier observations on brain asymmetry in functional lateralities, it can be hypothesized that a normal symmetric sagittal occlusal relationship is based on unilateral sagittal compensatory growth to maintain optimal bite, challenging early preventive orthodontic treatment in suspect unilateral Angle II cases.