Abstract
We discussed the influence of the tongue rest position on the anterior occlusal relationship among children with tongue thrust.24 children with anterior malocclusion in the mixed dentition period were classified into two groups, the habit group and the non-habit group. The habit group was divided into two types, the open bite type and the anterior cross bite type, and the non-habit group was also divided into two types, the anterior cross bite type and Class I crowding type, according to their clinical diagnoses. The ultrasound mid-sagittal images of their tongue movements during deglutition were recorded using the B-mode. In order to analyze the degree of flatness of the tongue dorsum both when swallowing and resting, the traced tongue dorsum images were divided into quarters mesiodistally and the tangent of each quarter was calculated. We defined the averaged absolute values of the four tangents as the CTD (Curvature of Tongue Dorsum) of each child, and analyzed the relationship between the CTDs and the overbite figures which were calculated from their lateral cephalograms.
There were significant correlations both between the CTD during swallowing and the overbites and between the CTD during resting and the overbites. There was no significant correlation between the CTD during swallowing and the CTD during resting. It is, therefore, suggested that the tongue rest position influenced the anterior occlusal relationship in addition to the tongue swallowing position. The mean of the CTDs of the open bite type in the habit group was the lowest, and that of the anterior cross bite type in the habit group followed. The variations of the CTDs in the habit group are significantly smaller than those of the non-habit group. It seemed that the tongue dorsum of the habit group was by and large flat and the habit group had the characteristic shapes of the tongue dorsum.
