The Effect of Bimaxillary Orthognathic Surgery on Voice Characteristics in Skeletal Class 3 Deformity Patients: An Evaluation Using Acoustic Analysis

The aim of this study was to analyze the effects of bimaxillary orthognathic surgery on the acoustic voice characteristics of skeletal class 3 patients. All healthy nonsyndromic patients with Class 3 deformity who were eligible for bimaxillary orthognathic surgery, were included in this before and after quasi-experimental study. This experiment's main intervention was mandibular setback surgery by bilateral sagittal split osteotomy plus maxillary advancement using LeFort 1 osteotomy. Age, sex, and intraoperative jaw movements were recorded. Acoustic analysis of voice samples (vowels /a/ and /i/) was performed with Praat software as outcome variables. The formant frequencies (F0, F1, F2, and F3) of these vowels were extracted 1 week preoperatively (T0), 1 and 6 months (T1, T2) postoperatively by a speech therapist. The significance level was set at 0.05 using SPSS 19. The study sample comprised 20 patients including 11 women (55%) and 9 men (45%) with a mean age of 31.95 ± 4.72 years. The average mandibular setback and maxillary advancement were 3.30 ± 0.86 and 2.85 ± 0.74 mm, respectively. The fundamental frequency (F0) and the first, second, and third formants (F1, F2, F3) of vowels /i/ and /a/ were significantly decreased over time intervals, postoperatively (P < 0.05). The finding revealed that bimaxillary orthognathic surgery (maxillary advancement and mandibular setback with bilateral sagittal split osteotomy) might reduce the acoustic formant parameters of voice to the normal frequency ranges, in patients with class 3 skeletal deformities. More clinical trials with greater sample sizes and long-term follow-ups are suggested in the future.