Relationships among tongue volume, hyoid position, airway volume and maxillofacial form in paediatric patients with Class-I, Class-II and Class-III malocclusions

OBJECTIVES: To clarify the associations among tongue volume, hyoid position, airway volume and maxillofacial form using cone beam computed tomography (CBCT) data for children with Class-I, Class-II and Class-III malocclusion. SETTING AND SAMPLE POPULATION: Sixty children (mean age, 9.2 years) divided into Class-I, Class-II and Class-III malocclusion groups according to the A-nasion-B angle. MATERIAL AND METHODS: Cone beam computed tomography was used for three-dimensional reconstruction of the maxillofacial region and airway. The hyoid position and the tongue, airway and oral cavity volumes were evaluated. Upper airway ventilation status was calculated using computational fluid dynamics. The groups were compared using analysis of variance and Kruskal-Wallis tests; relationships among the parameters were assessed using Pearson's and Spearman's rank correlation tests. RESULTS: The tongue volume was larger in Class-III patients (50.63 cm3 ) than in Class-I patients (44.24 cm3 ; P < 0.05). The hyoid position was lower (49.44 cm), and anatomical balance (AB; tongue volume/oral cavity volume; 85.06%) was greater in Class-II patients than in Class-I patients (46.06 cm, 80.57%, respectively; P < 0.05 for both). The hyoid height showed a positive correlation with AB (r = 0.614; P < 0.001). CONCLUSIONS: Children with Class-III malocclusion have large tongue volumes and small AB; the reverse is true for children with Class-II malocclusion. The hyoid position is closely associated with AB in children with malocclusion.