Effects of the Orthognathic Surgery on the Voice Characteristics of Skeletal Class III Patients

To analyze the effects of the bimaxillary orthognathic surgery on the voice characteristics of skeletal Class III cases, and to evaluate correlations between acoustic and skeletal changes.

Skeletal Class III adult patients (7 male, 18 female) were asked to pronounce the sounds "[a], [ɛ], [ɯ], [i], [ɔ], [œ], [u], [y]" for 3 seconds. Voice records and lateral cephalometric x-rays were taken before the surgery (T0) and 6 months after (T1). Voice records were taken for the control group with 6 months of interval (n=20). The formant frequencies (F0, F1, F2, and F3), Shimmer, Jitter and Noise to Harmonic Ratio (NHR) parameters were considered with Praat version 6.0.43.

In the surgery group, significant differences were observed in the F1 of [e], F2 and Shimmer of [ɯ] and F1 and F2 of [œ] and F1 of [y] sound, the post-surgery values were lower. F3 of [u] sound was higher. In comparison with the control group, ΔF3 of the [ɔ], ΔF3 of the [u] and ΔF1 of the [y] sound, ΔShimmer of [ɛ], [ɯ], [i], [ɔ], [u] and [y], and the ΔNHR of [ɔ] sound significantly changed. The Pearson correlation analysis proved some correlations; ΔF2 between ΔSNA for [ɯ] and [œ] sounds, ΔF1 between ΔHBV for [y] sound.

Bimaxillary orthognathic surgery changed some voice parameters in skeletal Class III patients. Some correlations were found between skeletal and acoustic parameters. We advise clinicians to consider these findings and inform their patients.