Effects of Class III malocclusion on young male adults' vocal tract development: a pilot study

PURPOSE: To compare the vocal tract configuration between male speakers with Class III malocclusion and their normally-developing counterparts, and investigate the concomitant acoustic changes due to the alterations in vocal tract configuration. PATIENTS AND METHODS: Eight young males with Class III malocclusion and eight normallydeveloping counterparts participated in this study. Acoustic reflection (AR) technology was used to measure vocal tract dimensions in the two groups. A continuous speech sample and four sustained vowels (/a/, / æ /, /i/, and /u/) were recorded from each participant to obtain the fundamental frequency and the first three formant frequencies (F1, F2, and F3). RESULTS: The results showed significantly greater oral length and oral volume for young men with Class III malocclusion than their cohorts. The F1 of vowel /u/ was found to be significantly higher in males with Class III malocclusion than their cohorts. The vowel space of the four recorded vowels was reduced and the F1-F2 formant map for /u/ was relatively more scattered in males with Class III malocclusion than in the control speakers. CONCLUSION: This study has provided preliminary information on the effects of Class III malocclusion on vocal tract configuration and concomitant acoustic changes in young men