2013 Volume 76 Issue 1 Pages 9-17
We investigated how mandibular setback for skeletal Class III cases influenced swallowing by focusing on the closing movement of the aditus laryngis by the epiglottis. We studied the swallow-triangle (HEP) on lateral cephalograms, which is formed by H (the hyoid), E (the epiglottis) and P (the posterior wall of the pharynx : the imaginary point with which the epiglottis connects). We used 20 cephalograms. Fifteen were from 5 patients who had received treatment ; 5 were pre-treatment, 5 were immediately after the operation, and 5 were post-treatment. Another 5 were from subjects with normal occlusion, which were used as controls.
We evaluated measurements including the distances H-E, H-P and E-P, the position H, E and P, and the pharyngeal airway dimension in the region. The pre-treatment group, the immediate post-operation group and the post-treatment group were statistically analyzed using oneway ANOVA. Based on the t-test, comparisons were made between the pre-treatment group and the controls, between the immediate post-operation group and controls, and between the post-treatment group and the controls. There were no significant differences except for the measurement of the vertical position of E between the immediate post-operation group and the controls.
We also observed behaviors of the swallow-triangle during treatment by superimposition of cephalometric tracings. Observations mainly indicated that the triangle immediately after the operation had moved posteroinferior to its original position, while the post-treatment triangle had moved anterosuperior towards its original position. The same situation was observed after longterm follow-up with the hyoid in stable cases treated by mandibular setback.
Our study suggests morphological and positional stability of the swallow-triangle during mandibular setback is probably dependent on maintaining respiration and swallowing. Stability of the swallow-triangle might be associated with the stable treatment results.
