Abstract
Objective: We measured the formant frequency of vowels in retrusion patients and normal healthy control patients, and made a comparative study of the purpose in phonology. We wanted to know how orthognathic surgery has influenced the articulation of vowels in patients. We investigated how the relationships between the position of the maxilla and mandible and incisor occlusion affected vowel sounds. And because resonance space is believed to affect sound frequencies, we investigated the effect of the width of the airway preoperatively and postoperatively on vowel sounds.
Methods: Five vowel sounds in 10 Japanese patients with mandibular retrusion requiring surgery for jaw deformity and malocclusion preoperatively and at 3 and 6 months postoperatively were recorded and compared with those in normal healthy control patients. Also, the effect of the positional relationship between the maxilla and the mandible and incisor occlusion on these vowel sounds was investigated by correlating skeletal and denture patterns of cephalometric measurements taken preoperatively and at 3 months postoperatively with these vowel sounds. The width of the airway was measured preoperatively and 3 months after the operation, and the correlation with the frequency of the vowels was examined.
Results: In /e/ F1, /o/ F2-F1, significant differences were observed between the preoperative patients and the control patients. However, these differences disappeared at 3 and 6 months postoperatively.
A significant difference was admitted with F1 of /a/ and F1 of /e/ in comparing the preoperative with the postoperative patients 6 months by a rank test with a sign of Wilcoxon.
Both preoperatively and postoperatively, positive correlations were observed between F2-F1 the narrow, open vowels /i/ with SNA and SNB. In the preoperative patients, some correlations were observed between F1 the semi-narrow, open vowel /e/ and denture patterns.
Significant increases were observed between the preoperative and 3 months postoperative patients in the width of the hypopharyngeal cavity. Many correlations were observed between the change of width of the airway and the vowel frequency, particularly in the posterior tongue vowel /u/. But other vowels had few correlations.
Conclusion: A change of occlusion of the front teeth and a change of frame by the mandible correction operation greatly influenced close vowels and half close vowels that were a front tongue vowel, especially the influence of /i/ and /e/ in retrusion patients. It was an interior tongue vowel that the change in the airway influenced the vowel frequency of only /u/.
