The clinical application of acoustic analysis to evaluation of tongue position

Tongue thrust is a habit in which the tongue protrudes between the upper and lower anterior teeth and causes malocclusion. Oral myofunctional therapy (MFT) is used to eliminate the habit of tongue-thrust swallowing. In the present study, we investigated changes in the tongue position before and after MFT using acoustic analysis. Twelve patients with tongue thrust who underwent MFT were enrolled. The first formant (F1) and the second formant (F2) of the consonant /∫/ were analyzed. To revise individual differences, F1 and F2 were divided by the fourth formant (F’4) of the vowel /i/. As a result, F1/F’4 and F2/F’4 were significantly lower after MFT than before MFT. Our results suggest that the tongue moves superiorly and posteriorly after MFT, which restores normal swallowing in patients with the tongue thrust habit.