Vowel sound production and its association with cephalometric characteristics in skeletal Class III subjects.

This study investigates differences in vowel sound production between Japanese males with skeletal Class III malocclusion—characterized by a forward mandibular position and larger mandible—and those with skeletal Class I anatomy, using acoustic and cephalometric analyses. Results showed that Class III subjects produced a significantly different back and rounded vowel (/o/) with higher second formant (F2) and lower fourth formant (F4) frequencies, suggesting altered tongue and lip articulation linked to their anatomical features. Moderate negative correlations were found between vowel acoustic parameters and mandibular measurements such as mandibular length, SNB angle, and overjet in Class III individuals. The findings highlight the potential for speech distortion related to skeletal discrepancies and underscore the importance of multidisciplinary evaluation, including speech pathology, especially considering possible speech changes following orthognathic surgery.