Voice characteristics before versus after mandibular setback surgery in patients with mandibular prognathism using nonlinear dynamics and conventional acoustic analyses

Abstract

Objectives: The purpose of this study was to explore the voice characteristics of patients with mandibular prognathism, and to investigate the effects of mandibular setback surgery on these characteristics using nonlinear dynamics and conventional acoustic analyses.

Materials and methods: Sixteen patients (8 males and 8 females) who had skeletal 3, class III malocclusion without cleft palate, and who underwent a bilateral sagittal split ramus osteotomy (BSSRO), were enrolled. As controls, 50 healthy adults (25 males and 25 females) were enrolled. The mean first LEs (mLE1) computed for each one-second interval, and the fundamental frequency (F0) and frequencies of the first and second formant (F1, F2) were calculated for each Japanese vowel.

Results and conclusions: The mLE1s for /u/ in males, and /o/ in females and the F2s for /i/ and /u/ in males, changed significantly after BSSRO. Class III voice characteristics were observed in the mLE1s for /i/ in both males and females, in the F0 for /a/, /i/, /u/ and /o/ in females, and in the F1 and F2 for /a/ in males, and the F1 for /u/ and the F2 for /i/ in females. Most of these characteristics were preserved after BSSRO.

Keywords: Formant frequency; Fundamental frequency; Lyapunov exponent; Mandibular prognathism; Sagittal split ramus osteotomy.