Three-dimensional ultrasound diagnostics of tongue posture in children with unilateral posterior crossbite.

INTRODUCTION Incorrect tongue posture on the mouth floor is considered an important factor in the etiology of unilateral posterior crossbite. The aim of this study was to objectively assess tongue posture in children with unilateral posterior crossbite and those with normal deciduous dentition by using 3-dimensional (3D) ultrasonography. METHODS First, referential 3D ultrasound images for differently postured tongues were acquired and reconstructed in 10 adults. Second, 27 children with unilateral posterior crossbite (mean age, 5.4 ± 1 years) and 23 children with normal deciduous dentition (mean age, 6.2 ± 0.4 years) were examined by using the 3D ultrasound technique. The referential 3D ultrasound reconstructions were used for the assessment of tongue posture in each child. RESULTS The characteristic 3D reconstruction of the tongue postured on the palate displays distinctive convexity of the tongue dorsum, whereas, in the 3D reconstruction with the tongue postured on the mouth floor, the dorsum is characterized by a central groove and expressed concavity. Posture on the mouth floor was demonstrated by 81.5% of the children with unilateral posterior crossbite and by only 34.8% of those with normal deciduous dentition. The difference was statistically significant (Fisher exact test: P = 0.0012). CONCLUSIONS Three-dimensional ultrasonography enables objective assessment of tongue posture and could become in the future an important part of functional diagnostics before, during, and after orthodontic treatment.